Add error returning for missing error output paths

Co-Authored-By: Captain ALM <captainalm@captainalm.com>

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,5 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Question
+    url: "https://web.libera.chat/gamja/#emersion"
+    about: "Please ask questions in #emersion on Libera Chat"

.github/ISSUE_TEMPLATE/issue_template.md

@@ -0,0 +1,12 @@
+---
+name: Bug report or feature request
+about: Report a bug or request a new feature
+---
+
+<!--
+
+Please read the following before submitting a new issue:
+
+Do NOT create GitHub issues if you have a question about go-webdav or about WebDAV in general. Ask questions on IRC in #emersion on Libera Chat.
+
+-->

.gitignore

@@ -12,3 +12,4 @@
 
 # Project-local glide cache, RE: https://github.com/Masterminds/glide/issues/736
 .glide/
+.idea/

README.md

@@ -1,6 +1,6 @@
 # go-webdav
 
-[![GoDoc](https://godoc.org/github.com/emersion/go-webdav?status.svg)](https://godoc.org/github.com/emersion/go-webdav)
+[![Go Reference](https://pkg.go.dev/badge/github.com/emersion/go-webdav.svg)](https://pkg.go.dev/github.com/emersion/go-webdav)
 
 A Go library for [WebDAV], [CalDAV] and [CardDAV].
 

caldav/caldav.go

@@ -4,16 +4,71 @@
 package caldav
 
 import (
+	"fmt"
 	"time"
 
 	"github.com/emersion/go-ical"
+	"github.com/emersion/go-webdav"
+	"github.com/emersion/go-webdav/internal"
 )
 
+var CapabilityCalendar = webdav.Capability("calendar-access")
+
+func NewCalendarHomeSet(path string) webdav.BackendSuppliedHomeSet {
+	return &calendarHomeSet{Href: internal.Href{Path: path}}
+}
+
+// ValidateCalendarObject checks the validity of a calendar object according to
+// the contraints layed out in RFC 4791 section 4.1 and returns the only event
+// type and UID occuring in this calendar, or an error if the calendar could
+// not be validated.
+func ValidateCalendarObject(cal *ical.Calendar) (eventType string, uid string, err error) {
+	// Calendar object resources contained in calendar collections
+	// MUST NOT specify the iCalendar METHOD property.
+	if prop := cal.Props.Get(ical.PropMethod); prop != nil {
+		return "", "", fmt.Errorf("calendar resource must not specify METHOD property")
+	}
+
+	for _, comp := range cal.Children {
+		// Calendar object resources contained in calendar collections
+		// MUST NOT contain more than one type of calendar component
+		// (e.g., VEVENT, VTODO, VJOURNAL, VFREEBUSY, etc.) with the
+		// exception of VTIMEZONE components, which MUST be specified
+		// for each unique TZID parameter value specified in the
+		// iCalendar object.
+		if comp.Name != ical.CompTimezone {
+			if eventType == "" {
+				eventType = comp.Name
+			}
+			if eventType != comp.Name {
+				return "", "", fmt.Errorf("conflicting event types in calendar: %s, %s", eventType, comp.Name)
+			}
+			// TODO check VTIMEZONE for each TZID?
+		}
+
+		// Calendar components in a calendar collection that have
+		// different UID property values MUST be stored in separate
+		// calendar object resources.
+		compUID, err := comp.Props.Text(ical.PropUID)
+		if err != nil {
+			return "", "", fmt.Errorf("error checking component UID: %v", err)
+		}
+		if uid == "" {
+			uid = compUID
+		}
+		if compUID != "" && uid != compUID {
+			return "", "", fmt.Errorf("conflicting UID values in calendar: %s, %s", uid, compUID)
+		}
+	}
+	return eventType, uid, nil
+}
+
 type Calendar struct {
-	Path            string
-	Name            string
-	Description     string
-	MaxResourceSize int64
+	Path                  string
+	Name                  string
+	Description           string
+	MaxResourceSize       int64
+	SupportedComponentSet []string
 }
 
 type CalendarCompRequest struct {
@@ -27,19 +82,30 @@ type CalendarCompRequest struct {
 }
 
 type CompFilter struct {
-	Name       string
-	Start, End time.Time
-	Props      []PropFilter
-	Comps      []CompFilter
+	Name         string
+	IsNotDefined bool
+	Start, End   time.Time
+	Props        []PropFilter
+	Comps        []CompFilter
+}
+
+type ParamFilter struct {
+	Name         string
+	IsNotDefined bool
+	TextMatch    *TextMatch
 }
 
 type PropFilter struct {
-	Name      string
-	TextMatch *TextMatch
+	Name         string
+	IsNotDefined bool
+	Start, End   time.Time
+	TextMatch    *TextMatch
+	ParamFilter  []ParamFilter
 }
 
 type TextMatch struct {
-	Text string
+	Text            string
+	NegateCondition bool
 }
 
 type CalendarQuery struct {
@@ -47,9 +113,15 @@ type CalendarQuery struct {
 	CompFilter  CompFilter
 }
 
-type CalendarObject struct {
-	Path    string
-	ModTime time.Time
-	ETag    string
-	Data    *ical.Calendar
+type CalendarMultiGet struct {
+	Paths       []string
+	CompRequest CalendarCompRequest
+}
+
+type CalendarObject struct {
+	Path          string
+	ModTime       time.Time
+	ContentLength int64
+	ETag          string
+	Data          *ical.Calendar
 }

caldav/client.go

@@ -2,6 +2,7 @@ package caldav
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"mime"
 	"net/http"
@@ -15,6 +16,12 @@ import (
 	"github.com/emersion/go-webdav/internal"
 )
 
+// DiscoverContextURL performs a DNS-based CardDAV service discovery as
+// described in RFC 6352 section 11. It returns the URL to the CardDAV server.
+func DiscoverContextURL(ctx context.Context, domain string) (string, error) {
+	return internal.DiscoverContextURL(ctx, "caldavs", domain)
+}
+
 // Client provides access to a remote CardDAV server.
 type Client struct {
 	*webdav.Client
@@ -34,9 +41,9 @@ func NewClient(c webdav.HTTPClient, endpoint string) (*Client, error) {
 	return &Client{wc, ic}, nil
 }
 
-func (c *Client) FindCalendarHomeSet(principal string) (string, error) {
-	propfind := internal.NewPropNamePropfind(calendarHomeSetName)
-	resp, err := c.ic.PropfindFlat(principal, propfind)
+func (c *Client) FindCalendarHomeSet(ctx context.Context, principal string) (string, error) {
+	propfind := internal.NewPropNamePropFind(calendarHomeSetName)
+	resp, err := c.ic.PropFindFlat(ctx, principal, propfind)
 	if err != nil {
 		return "", err
 	}
@@ -49,14 +56,15 @@ func (c *Client) FindCalendarHomeSet(principal string) (string, error) {
 	return prop.Href.Path, nil
 }
 
-func (c *Client) FindCalendars(calendarHomeSet string) ([]Calendar, error) {
-	propfind := internal.NewPropNamePropfind(
+func (c *Client) FindCalendars(ctx context.Context, calendarHomeSet string) ([]Calendar, error) {
+	propfind := internal.NewPropNamePropFind(
 		internal.ResourceTypeName,
 		internal.DisplayNameName,
 		calendarDescriptionName,
 		maxResourceSizeName,
+		supportedCalendarComponentSetName,
 	)
-	ms, err := c.ic.Propfind(calendarHomeSet, internal.DepthOne, propfind)
+	ms, err := c.ic.PropFind(ctx, calendarHomeSet, internal.DepthOne, propfind)
 	if err != nil {
 		return nil, err
 	}
@@ -94,11 +102,22 @@ func (c *Client) FindCalendars(calendarHomeSet string) ([]Calendar, error) {
 			return nil, fmt.Errorf("carddav: max-resource-size must be a positive integer")
 		}
 
+		var supportedCompSet supportedCalendarComponentSet
+		if err := resp.DecodeProp(&supportedCompSet); err != nil && !internal.IsNotFound(err) {
+			return nil, err
+		}
+
+		compNames := make([]string, 0, len(supportedCompSet.Comp))
+		for _, comp := range supportedCompSet.Comp {
+			compNames = append(compNames, comp.Name)
+		}
+
 		l = append(l, Calendar{
-			Path:            path,
-			Name:            dispName.Name,
-			Description:     desc.Description,
-			MaxResourceSize: maxResSize.Size,
+			Path:                  path,
+			Name:                  dispName.Name,
+			Description:           desc.Description,
+			MaxResourceSize:       maxResSize.Size,
+			SupportedComponentSet: compNames,
 		})
 	}
 
@@ -156,7 +175,7 @@ func encodeCompFilter(filter *CompFilter) *compFilter {
 	return &encoded
 }
 
-func decodeCalendarObjectList(ms *internal.Multistatus) ([]CalendarObject, error) {
+func decodeCalendarObjectList(ms *internal.MultiStatus) ([]CalendarObject, error) {
 	addrs := make([]CalendarObject, 0, len(ms.Responses))
 	for _, resp := range ms.Responses {
 		path, err := resp.Path()
@@ -179,6 +198,11 @@ func decodeCalendarObjectList(ms *internal.Multistatus) ([]CalendarObject, error
 			return nil, err
 		}
 
+		var getContentLength internal.GetContentLength
+		if err := resp.DecodeProp(&getContentLength); err != nil && !internal.IsNotFound(err) {
+			return nil, err
+		}
+
 		r := bytes.NewReader(calData.Data)
 		data, err := ical.NewDecoder(r).Decode()
 		if err != nil {
@@ -186,17 +210,18 @@ func decodeCalendarObjectList(ms *internal.Multistatus) ([]CalendarObject, error
 		}
 
 		addrs = append(addrs, CalendarObject{
-			Path:    path,
-			ModTime: time.Time(getLastMod.LastModified),
-			ETag:    string(getETag.ETag),
-			Data:    data,
+			Path:          path,
+			ModTime:       time.Time(getLastMod.LastModified),
+			ContentLength: getContentLength.Length,
+			ETag:          string(getETag.ETag),
+			Data:          data,
 		})
 	}
 
 	return addrs, nil
 }
 
-func (c *Client) QueryCalendar(calendar string, query *CalendarQuery) ([]CalendarObject, error) {
+func (c *Client) QueryCalendar(ctx context.Context, calendar string, query *CalendarQuery) ([]CalendarObject, error) {
 	propReq, err := encodeCalendarReq(&query.CompRequest)
 	if err != nil {
 		return nil, err
@@ -210,7 +235,7 @@ func (c *Client) QueryCalendar(calendar string, query *CalendarQuery) ([]Calenda
 	}
 	req.Header.Add("Depth", "1")
 
-	ms, err := c.ic.DoMultiStatus(req)
+	ms, err := c.ic.DoMultiStatus(req.WithContext(ctx))
 	if err != nil {
 		return nil, err
 	}
@@ -218,22 +243,61 @@ func (c *Client) QueryCalendar(calendar string, query *CalendarQuery) ([]Calenda
 	return decodeCalendarObjectList(ms)
 }
 
-func populateCalendarObject(co *CalendarObject, resp *http.Response) error {
-	if loc := resp.Header.Get("Location"); loc != "" {
+func (c *Client) MultiGetCalendar(ctx context.Context, path string, multiGet *CalendarMultiGet) ([]CalendarObject, error) {
+	propReq, err := encodeCalendarReq(&multiGet.CompRequest)
+	if err != nil {
+		return nil, err
+	}
+
+	calendarMultiget := calendarMultiget{Prop: propReq}
+
+	if len(multiGet.Paths) == 0 {
+		href := internal.Href{Path: path}
+		calendarMultiget.Hrefs = []internal.Href{href}
+	} else {
+		calendarMultiget.Hrefs = make([]internal.Href, len(multiGet.Paths))
+		for i, p := range multiGet.Paths {
+			calendarMultiget.Hrefs[i] = internal.Href{Path: p}
+		}
+	}
+
+	req, err := c.ic.NewXMLRequest("REPORT", path, &calendarMultiget)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Add("Depth", "1")
+
+	ms, err := c.ic.DoMultiStatus(req.WithContext(ctx))
+	if err != nil {
+		return nil, err
+	}
+
+	return decodeCalendarObjectList(ms)
+}
+
+func populateCalendarObject(co *CalendarObject, h http.Header) error {
+	if loc := h.Get("Location"); loc != "" {
 		u, err := url.Parse(loc)
 		if err != nil {
 			return err
 		}
 		co.Path = u.Path
 	}
-	if etag := resp.Header.Get("ETag"); etag != "" {
+	if etag := h.Get("ETag"); etag != "" {
 		etag, err := strconv.Unquote(etag)
 		if err != nil {
 			return err
 		}
 		co.ETag = etag
 	}
-	if lastModified := resp.Header.Get("Last-Modified"); lastModified != "" {
+	if contentLength := h.Get("Content-Length"); contentLength != "" {
+		n, err := strconv.ParseInt(contentLength, 10, 64)
+		if err != nil {
+			return err
+		}
+		co.ContentLength = n
+	}
+	if lastModified := h.Get("Last-Modified"); lastModified != "" {
 		t, err := http.ParseTime(lastModified)
 		if err != nil {
 			return err
@@ -244,14 +308,14 @@ func populateCalendarObject(co *CalendarObject, resp *http.Response) error {
 	return nil
 }
 
-func (c *Client) GetCalendarObject(path string) (*CalendarObject, error) {
+func (c *Client) GetCalendarObject(ctx context.Context, path string) (*CalendarObject, error) {
 	req, err := c.ic.NewRequest(http.MethodGet, path, nil)
 	if err != nil {
 		return nil, err
 	}
 	req.Header.Set("Accept", ical.MIMEType)
 
-	resp, err := c.ic.Do(req)
+	resp, err := c.ic.Do(req.WithContext(ctx))
 	if err != nil {
 		return nil, err
 	}
@@ -274,13 +338,13 @@ func (c *Client) GetCalendarObject(path string) (*CalendarObject, error) {
 		Path: resp.Request.URL.Path,
 		Data: cal,
 	}
-	if err := populateCalendarObject(co, resp); err != nil {
+	if err := populateCalendarObject(co, resp.Header); err != nil {
 		return nil, err
 	}
 	return co, nil
 }
 
-func (c *Client) PutCalendarObject(path string, cal *ical.Calendar) (*CalendarObject, error) {
+func (c *Client) PutCalendarObject(ctx context.Context, path string, cal *ical.Calendar) (*CalendarObject, error) {
 	// TODO: add support for If-None-Match and If-Match
 
 	// TODO: some servers want a Content-Length header, so we can't stream the
@@ -298,14 +362,14 @@ func (c *Client) PutCalendarObject(path string, cal *ical.Calendar) (*CalendarOb
 	}
 	req.Header.Set("Content-Type", ical.MIMEType)
 
-	resp, err := c.ic.Do(req)
+	resp, err := c.ic.Do(req.WithContext(ctx))
 	if err != nil {
 		return nil, err
 	}
 	resp.Body.Close()
 
 	co := &CalendarObject{Path: path}
-	if err := populateCalendarObject(co, resp); err != nil {
+	if err := populateCalendarObject(co, resp.Header); err != nil {
 		return nil, err
 	}
 	return co, nil

caldav/elements.go

@@ -2,6 +2,7 @@ package caldav
 
 import (
 	"encoding/xml"
+	"fmt"
 	"time"
 
 	"github.com/emersion/go-webdav/internal"
@@ -12,11 +13,16 @@ const namespace = "urn:ietf:params:xml:ns:caldav"
 var (
 	calendarHomeSetName = xml.Name{namespace, "calendar-home-set"}
 
-	calendarDescriptionName   = xml.Name{namespace, "calendar-description"}
-	supportedCalendarDataName = xml.Name{namespace, "supported-calendar-data"}
-	maxResourceSizeName       = xml.Name{namespace, "max-resource-size"}
+	calendarDescriptionName           = xml.Name{namespace, "calendar-description"}
+	supportedCalendarDataName         = xml.Name{namespace, "supported-calendar-data"}
+	supportedCalendarComponentSetName = xml.Name{namespace, "supported-calendar-component-set"}
+	maxResourceSizeName               = xml.Name{namespace, "max-resource-size"}
 
-	calendarName = xml.Name{namespace, "calendar"}
+	calendarQueryName    = xml.Name{namespace, "calendar-query"}
+	calendarMultigetName = xml.Name{namespace, "calendar-multiget"}
+
+	calendarName     = xml.Name{namespace, "calendar"}
+	calendarDataName = xml.Name{namespace, "calendar-data"}
 )
 
 // https://tools.ietf.org/html/rfc4791#section-6.2.1
@@ -25,6 +31,10 @@ type calendarHomeSet struct {
 	Href    internal.Href `xml:"DAV: href"`
 }
 
+func (a *calendarHomeSet) GetXMLName() xml.Name {
+	return calendarHomeSetName
+}
+
 // https://tools.ietf.org/html/rfc4791#section-5.2.1
 type calendarDescription struct {
 	XMLName     xml.Name `xml:"urn:ietf:params:xml:ns:caldav calendar-description"`
@@ -37,6 +47,12 @@ type supportedCalendarData struct {
 	Types   []calendarDataType `xml:"calendar-data"`
 }
 
+// https://tools.ietf.org/html/rfc4791#section-5.2.3
+type supportedCalendarComponentSet struct {
+	XMLName xml.Name `xml:"urn:ietf:params:xml:ns:caldav supported-calendar-component-set"`
+	Comp    []comp   `xml:"comp"`
+}
+
 // https://tools.ietf.org/html/rfc4791#section-9.6
 type calendarDataType struct {
 	XMLName     xml.Name `xml:"urn:ietf:params:xml:ns:caldav calendar-data"`
@@ -60,6 +76,15 @@ type calendarQuery struct {
 	// TODO: timezone
 }
 
+// https://tools.ietf.org/html/rfc4791#section-9.10
+type calendarMultiget struct {
+	XMLName  xml.Name        `xml:"urn:ietf:params:xml:ns:caldav calendar-multiget"`
+	Hrefs    []internal.Href `xml:"DAV: href"`
+	Prop     *internal.Prop  `xml:"DAV: prop,omitempty"`
+	AllProp  *struct{}       `xml:"DAV: allprop,omitempty"`
+	PropName *struct{}       `xml:"DAV: propname,omitempty"`
+}
+
 // https://tools.ietf.org/html/rfc4791#section-9.7
 type filter struct {
 	XMLName    xml.Name   `xml:"urn:ietf:params:xml:ns:caldav filter"`
@@ -78,19 +103,49 @@ type compFilter struct {
 
 // https://tools.ietf.org/html/rfc4791#section-9.7.2
 type propFilter struct {
-	XMLName      xml.Name   `xml:"urn:ietf:params:xml:ns:caldav prop-filter"`
+	XMLName      xml.Name      `xml:"urn:ietf:params:xml:ns:caldav prop-filter"`
+	Name         string        `xml:"name,attr"`
+	IsNotDefined *struct{}     `xml:"is-not-defined,omitempty"`
+	TimeRange    *timeRange    `xml:"time-range,omitempty"`
+	TextMatch    *textMatch    `xml:"text-match,omitempty"`
+	ParamFilter  []paramFilter `xml:"param-filter,omitempty"`
+}
+
+// https://tools.ietf.org/html/rfc4791#section-9.7.3
+type paramFilter struct {
+	XMLName      xml.Name   `xml:"urn:ietf:params:xml:ns:caldav param-filter"`
 	Name         string     `xml:"name,attr"`
 	IsNotDefined *struct{}  `xml:"is-not-defined,omitempty"`
-	TimeRange    *timeRange `xml:"time-range,omitempty"`
 	TextMatch    *textMatch `xml:"text-match,omitempty"`
-	// TODO: param-filter
 }
 
 // https://tools.ietf.org/html/rfc4791#section-9.7.5
 type textMatch struct {
-	XMLName xml.Name `xml:"urn:ietf:params:xml:ns:caldav text-match"`
-	Text    string   `xml:",chardata"`
-	// TODO: collation, negate-condition
+	XMLName         xml.Name        `xml:"urn:ietf:params:xml:ns:caldav text-match"`
+	Text            string          `xml:",chardata"`
+	Collation       string          `xml:"collation,attr,omitempty"`
+	NegateCondition negateCondition `xml:"negate-condition,attr,omitempty"`
+}
+
+type negateCondition bool
+
+func (nc *negateCondition) UnmarshalText(b []byte) error {
+	switch s := string(b); s {
+	case "yes":
+		*nc = true
+	case "no":
+		*nc = false
+	default:
+		return fmt.Errorf("caldav: invalid negate-condition value: %q", s)
+	}
+	return nil
+}
+
+func (nc negateCondition) MarshalText() ([]byte, error) {
+	if nc {
+		return []byte("yes"), nil
+	}
+	return nil, nil
 }
 
 // https://tools.ietf.org/html/rfc4791#section-9.9
@@ -151,3 +206,32 @@ type calendarDataResp struct {
 	XMLName xml.Name `xml:"urn:ietf:params:xml:ns:caldav calendar-data"`
 	Data    []byte   `xml:",chardata"`
 }
+
+type reportReq struct {
+	Query    *calendarQuery
+	Multiget *calendarMultiget
+	// TODO: CALDAV:free-busy-query
+}
+
+func (r *reportReq) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	var v interface{}
+	switch start.Name {
+	case calendarQueryName:
+		r.Query = &calendarQuery{}
+		v = r.Query
+	case calendarMultigetName:
+		r.Multiget = &calendarMultiget{}
+		v = r.Multiget
+	default:
+		return fmt.Errorf("caldav: unsupported REPORT root %q %q", start.Name.Space, start.Name.Local)
+	}
+
+	return d.DecodeElement(v, &start)
+}
+
+type mkcolReq struct {
+	XMLName      xml.Name              `xml:"DAV: mkcol"`
+	ResourceType internal.ResourceType `xml:"set>prop>resourcetype"`
+	DisplayName  string                `xml:"set>prop>displayname"`
+	// TODO this could theoretically contain all addressbook properties?
+}

caldav/match.go

@@ -0,0 +1,205 @@
+package caldav
+
+import (
+	"strings"
+	"time"
+
+	"github.com/emersion/go-ical"
+)
+
+// Filter returns the filtered list of calendar objects matching the provided query.
+// A nil query will return the full list of calendar objects.
+func Filter(query *CalendarQuery, cos []CalendarObject) ([]CalendarObject, error) {
+	if query == nil {
+		// FIXME: should we always return a copy of the provided slice?
+		return cos, nil
+	}
+
+	var out []CalendarObject
+	for _, co := range cos {
+		ok, err := Match(query.CompFilter, &co)
+		if err != nil {
+			return nil, err
+		}
+		if !ok {
+			continue
+		}
+
+		// TODO properties are not currently filtered even if requested
+		out = append(out, co)
+	}
+	return out, nil
+}
+
+// Match reports whether the provided CalendarObject matches the query.
+func Match(query CompFilter, co *CalendarObject) (matched bool, err error) {
+	if co.Data == nil || co.Data.Component == nil {
+		panic("request to process empty calendar object")
+	}
+	return match(query, co.Data.Component)
+}
+
+func match(filter CompFilter, comp *ical.Component) (bool, error) {
+	if comp.Name != filter.Name {
+		return filter.IsNotDefined, nil
+	}
+
+	var zeroDate time.Time
+	if filter.Start != zeroDate {
+		match, err := matchCompTimeRange(filter.Start, filter.End, comp)
+		if err != nil {
+			return false, err
+		}
+		if !match {
+			return false, nil
+		}
+	}
+	for _, compFilter := range filter.Comps {
+		match, err := matchCompFilter(compFilter, comp)
+		if err != nil {
+			return false, err
+		}
+		if !match {
+			return false, nil
+		}
+	}
+	for _, propFilter := range filter.Props {
+		match, err := matchPropFilter(propFilter, comp)
+		if err != nil {
+			return false, err
+		}
+		if !match {
+			return false, nil
+		}
+	}
+	return true, nil
+}
+
+func matchCompFilter(filter CompFilter, comp *ical.Component) (bool, error) {
+	var matches []*ical.Component
+
+	for _, child := range comp.Children {
+		match, err := match(filter, child)
+		if err != nil {
+			return false, err
+		} else if match {
+			matches = append(matches, child)
+		}
+	}
+	if len(matches) == 0 {
+		return filter.IsNotDefined, nil
+	}
+	return true, nil
+}
+
+func matchPropFilter(filter PropFilter, comp *ical.Component) (bool, error) {
+	// TODO: this only matches first field, there can be multiple
+	field := comp.Props.Get(filter.Name)
+	if field == nil {
+		return filter.IsNotDefined, nil
+	}
+
+	for _, paramFilter := range filter.ParamFilter {
+		if !matchParamFilter(paramFilter, field) {
+			return false, nil
+		}
+	}
+
+	var zeroDate time.Time
+	if filter.Start != zeroDate {
+		match, err := matchPropTimeRange(filter.Start, filter.End, field)
+		if err != nil {
+			return false, err
+		}
+		if !match {
+			return false, nil
+		}
+	} else if filter.TextMatch != nil {
+		if !matchTextMatch(*filter.TextMatch, field.Value) {
+			return false, nil
+		}
+		return true, nil
+	}
+	// empty prop-filter, property exists
+	return true, nil
+}
+
+func matchCompTimeRange(start, end time.Time, comp *ical.Component) (bool, error) {
+	// See https://datatracker.ietf.org/doc/html/rfc4791#section-9.9
+
+	// evaluate recurring components
+	rset, err := comp.RecurrenceSet(start.Location())
+	if err != nil {
+		return false, err
+	}
+	if rset != nil {
+		// TODO we can only set inclusive to true or false, but really the
+		// start time is inclusive while the end time is not :/
+		return len(rset.Between(start, end, true)) > 0, nil
+	}
+
+	// TODO handle more than just events
+	if comp.Name != ical.CompEvent {
+		return false, nil
+	}
+	event := ical.Event{comp}
+
+	eventStart, err := event.DateTimeStart(start.Location())
+	if err != nil {
+		return false, err
+	}
+	eventEnd, err := event.DateTimeEnd(end.Location())
+	if err != nil {
+		return false, err
+	}
+
+	// Event starts in time range
+	if eventStart.After(start) && (end.IsZero() || eventStart.Before(end)) {
+		return true, nil
+	}
+	// Event ends in time range
+	if eventEnd.After(start) && (end.IsZero() || eventEnd.Before(end)) {
+		return true, nil
+	}
+	// Event covers entire time range plus some
+	if eventStart.Before(start) && (!end.IsZero() && eventEnd.After(end)) {
+		return true, nil
+	}
+	return false, nil
+}
+
+func matchPropTimeRange(start, end time.Time, field *ical.Prop) (bool, error) {
+	// See https://datatracker.ietf.org/doc/html/rfc4791#section-9.9
+
+	ptime, err := field.DateTime(start.Location())
+	if err != nil {
+		return false, err
+	}
+	if ptime.After(start) && (end.IsZero() || ptime.Before(end)) {
+		return true, nil
+	}
+	return false, nil
+}
+
+func matchParamFilter(filter ParamFilter, field *ical.Prop) bool {
+	// TODO there can be multiple values
+	value := field.Params.Get(filter.Name)
+	if value == "" {
+		return filter.IsNotDefined
+	} else if filter.IsNotDefined {
+		return false
+	}
+	if filter.TextMatch != nil {
+		return matchTextMatch(*filter.TextMatch, value)
+	}
+	return true
+}
+
+func matchTextMatch(txt TextMatch, value string) bool {
+	// TODO: handle text-match collation attribute
+	match := strings.Contains(value, txt.Text)
+	if txt.NegateCondition {
+		match = !match
+	}
+	return match
+}

caldav/match_test.go

@@ -0,0 +1,311 @@
+package caldav
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/emersion/go-ical"
+)
+
+var dateFormat = "20060102T150405Z"
+
+func toDate(t *testing.T, date string) time.Time {
+	res, err := time.ParseInLocation(dateFormat, date, time.UTC)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return res
+}
+
+// Test data taken from https://datatracker.ietf.org/doc/html/rfc4791#appendix-B
+// TODO add missing data
+func TestFilter(t *testing.T) {
+	newCO := func(str string) CalendarObject {
+		cal, err := ical.NewDecoder(strings.NewReader(str)).Decode()
+		if err != nil {
+			t.Fatal(err)
+		}
+		return CalendarObject{
+			Data: cal,
+		}
+	}
+
+	event1 := newCO(`BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Example Corp.//CalDAV Client//EN
+BEGIN:VTIMEZONE
+LAST-MODIFIED:20040110T032845Z
+TZID:US/Eastern
+BEGIN:DAYLIGHT
+DTSTART:20000404T020000
+RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
+TZNAME:EDT
+TZOFFSETFROM:-0500
+TZOFFSETTO:-0400
+END:DAYLIGHT
+BEGIN:STANDARD
+DTSTART:20001026T020000
+RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
+TZNAME:EST
+TZOFFSETFROM:-0400
+TZOFFSETTO:-0500
+END:STANDARD
+END:VTIMEZONE
+BEGIN:VEVENT
+DTSTAMP:20060206T001102Z
+DTSTART;TZID=US/Eastern:20060102T100000
+DURATION:PT1H
+SUMMARY:Event #1
+Description:Go Steelers!
+UID:74855313FA803DA593CD579A@example.com
+END:VEVENT
+END:VCALENDAR`)
+
+	event2 := newCO(`BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Example Corp.//CalDAV Client//EN
+BEGIN:VTIMEZONE
+LAST-MODIFIED:20040110T032845Z
+TZID:US/Eastern
+BEGIN:DAYLIGHT
+DTSTART:20000404T020000
+RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
+TZNAME:EDT
+TZOFFSETFROM:-0500
+TZOFFSETTO:-0400
+END:DAYLIGHT
+BEGIN:STANDARD
+DTSTART:20001026T020000
+RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
+TZNAME:EST
+TZOFFSETFROM:-0400
+TZOFFSETTO:-0500
+END:STANDARD
+END:VTIMEZONE
+BEGIN:VEVENT
+DTSTAMP:20060206T001121Z
+DTSTART;TZID=US/Eastern:20060102T120000
+DURATION:PT1H
+RRULE:FREQ=DAILY;COUNT=5
+SUMMARY:Event #2
+UID:00959BC664CA650E933C892C@example.com
+END:VEVENT
+BEGIN:VEVENT
+DTSTAMP:20060206T001121Z
+DTSTART;TZID=US/Eastern:20060104T140000
+DURATION:PT1H
+RECURRENCE-ID;TZID=US/Eastern:20060104T120000
+SUMMARY:Event #2 bis
+UID:00959BC664CA650E933C892C@example.com
+END:VEVENT
+BEGIN:VEVENT
+DTSTAMP:20060206T001121Z
+DTSTART;TZID=US/Eastern:20060106T140000
+DURATION:PT1H
+RECURRENCE-ID;TZID=US/Eastern:20060106T120000
+SUMMARY:Event #2 bis bis
+UID:00959BC664CA650E933C892C@example.com
+END:VEVENT
+END:VCALENDAR`)
+
+	event3 := newCO(`BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Example Corp.//CalDAV Client//EN
+BEGIN:VTIMEZONE
+LAST-MODIFIED:20040110T032845Z
+TZID:US/Eastern
+BEGIN:DAYLIGHT
+DTSTART:20000404T020000
+RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
+TZNAME:EDT
+TZOFFSETFROM:-0500
+TZOFFSETTO:-0400
+END:DAYLIGHT
+BEGIN:STANDARD
+DTSTART:20001026T020000
+RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
+TZNAME:EST
+TZOFFSETFROM:-0400
+TZOFFSETTO:-0500
+END:STANDARD
+END:VTIMEZONE
+BEGIN:VEVENT
+ATTENDEE;PARTSTAT=ACCEPTED;ROLE=CHAIR:mailto:cyrus@example.com
+ATTENDEE;PARTSTAT=NEEDS-ACTION:mailto:lisa@example.com
+DTSTAMP:20060206T001220Z
+DTSTART;TZID=US/Eastern:20060104T100000
+DURATION:PT1H
+LAST-MODIFIED:20060206T001330Z
+ORGANIZER:mailto:cyrus@example.com
+SEQUENCE:1
+STATUS:TENTATIVE
+SUMMARY:Event #3
+UID:DC6C50A017428C5216A2F1CD@example.com
+END:VEVENT
+END:VCALENDAR`)
+
+	todo1 := newCO(`BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Example Corp.//CalDAV Client//EN
+BEGIN:VTODO
+DTSTAMP:20060205T235335Z
+DUE;VALUE=DATE:20060104
+STATUS:NEEDS-ACTION
+SUMMARY:Task #1
+UID:DDDEEB7915FA61233B861457@example.com
+BEGIN:VALARM
+ACTION:AUDIO
+TRIGGER;RELATED=START:-PT10M
+END:VALARM
+END:VTODO
+END:VCALENDAR`)
+
+	for _, tc := range []struct {
+		name  string
+		query *CalendarQuery
+		addrs []CalendarObject
+		want  []CalendarObject
+		err   error
+	}{
+		{
+			name:  "nil-query",
+			query: nil,
+			addrs: []CalendarObject{event1, event2, event3, todo1},
+			want:  []CalendarObject{event1, event2, event3, todo1},
+		},
+		{
+			// https://datatracker.ietf.org/doc/html/rfc4791#section-7.8.8
+			name: "events only",
+			query: &CalendarQuery{
+				CompFilter: CompFilter{
+					Name: "VCALENDAR",
+					Comps: []CompFilter{
+						CompFilter{
+							Name: "VEVENT",
+						},
+					},
+				},
+			},
+			addrs: []CalendarObject{event1, event2, event3, todo1},
+			want:  []CalendarObject{event1, event2, event3},
+		},
+		{
+			// https://datatracker.ietf.org/doc/html/rfc4791#section-7.8.1
+			name: "events in time range",
+			query: &CalendarQuery{
+				CompFilter: CompFilter{
+					Name: "VCALENDAR",
+					Comps: []CompFilter{
+						CompFilter{
+							Name:  "VEVENT",
+							Start: toDate(t, "20060104T000000Z"),
+							End:   toDate(t, "20060105T000000Z"),
+						},
+					},
+				},
+			},
+			addrs: []CalendarObject{event1, event2, event3, todo1},
+			want:  []CalendarObject{event2, event3},
+		},
+		{
+			// https://datatracker.ietf.org/doc/html/rfc4791#section-7.8.1
+			name: "events in open time range (no end date)",
+			query: &CalendarQuery{
+				CompFilter: CompFilter{
+					Name: "VCALENDAR",
+					Comps: []CompFilter{
+						CompFilter{
+							Name:  "VEVENT",
+							Start: toDate(t, "20060104T000000Z"),
+						},
+					},
+				},
+			},
+			addrs: []CalendarObject{event1, event2, event3, todo1},
+			want:  []CalendarObject{event2, event3},
+		},
+		{
+			// https://datatracker.ietf.org/doc/html/rfc4791#section-7.8.6
+			name: "events by UID",
+			query: &CalendarQuery{
+				CompFilter: CompFilter{
+					Name: "VCALENDAR",
+					Comps: []CompFilter{
+						CompFilter{
+							Name: "VEVENT",
+							Props: []PropFilter{{
+								Name: "UID",
+								TextMatch: &TextMatch{
+									Text: "DC6C50A017428C5216A2F1CD@example.com",
+								},
+							}},
+						},
+					},
+				},
+			},
+			addrs: []CalendarObject{event1, event2, event3, todo1},
+			want:  []CalendarObject{event3},
+		},
+		{
+			// https://datatracker.ietf.org/doc/html/rfc4791#section-7.8.6
+			name: "events by description substring",
+			query: &CalendarQuery{
+				CompFilter: CompFilter{
+					Name: "VCALENDAR",
+					Comps: []CompFilter{
+						CompFilter{
+							Name: "VEVENT",
+							Props: []PropFilter{{
+								Name: "Description",
+								TextMatch: &TextMatch{
+									Text: "Steelers",
+								},
+							}},
+						},
+					},
+				},
+			},
+			addrs: []CalendarObject{event1, event2, event3, todo1},
+			want:  []CalendarObject{event1},
+		},
+		{
+			// Query a time range that only returns a result if recurrence is properly evaluated.
+			name: "recurring events in time range",
+			query: &CalendarQuery{
+				CompFilter: CompFilter{
+					Name: "VCALENDAR",
+					Comps: []CompFilter{
+						CompFilter{
+							Name:  "VEVENT",
+							Start: toDate(t, "20060103T000000Z"),
+							End:   toDate(t, "20060104T000000Z"),
+						},
+					},
+				},
+			},
+			addrs: []CalendarObject{event1, event2, event3, todo1},
+			want:  []CalendarObject{event2},
+		},
+		// TODO add more examples
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := Filter(tc.query, tc.addrs)
+			switch {
+			case err != nil && tc.err == nil:
+				t.Fatalf("unexpected error: %+v", err)
+			case err != nil && tc.err != nil:
+				if got, want := err.Error(), tc.err.Error(); got != want {
+					t.Fatalf("invalid error:\ngot= %q\nwant=%q", got, want)
+				}
+			case err == nil && tc.err != nil:
+				t.Fatalf("expected an error:\ngot= %+v\nwant=%+v", err, tc.err)
+			case err == nil && tc.err == nil:
+				if got, want := got, tc.want; !reflect.DeepEqual(got, want) {
+					t.Fatalf("invalid filter values:\ngot= %+v\nwant=%+v", got, want)
+				}
+			}
+		})
+	}
+}

caldav/server.go

@@ -0,0 +1,773 @@
+package caldav
+
+import (
+	"bytes"
+	"context"
+	"encoding/xml"
+	"fmt"
+	"mime"
+	"net/http"
+	"path"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/emersion/go-ical"
+	"github.com/emersion/go-webdav"
+	"github.com/emersion/go-webdav/internal"
+)
+
+// TODO if nothing more Caldav-specific needs to be added this should be merged with carddav.PutAddressObjectOptions
+type PutCalendarObjectOptions struct {
+	// IfNoneMatch indicates that the client does not want to overwrite
+	// an existing resource.
+	IfNoneMatch webdav.ConditionalMatch
+	// IfMatch provides the ETag of the resource that the client intends
+	// to overwrite, can be ""
+	IfMatch webdav.ConditionalMatch
+}
+
+// Backend is a CalDAV server backend.
+type Backend interface {
+	CalendarHomeSetPath(ctx context.Context) (string, error)
+
+	CreateCalendar(ctx context.Context, calendar *Calendar) error
+	ListCalendars(ctx context.Context) ([]Calendar, error)
+	GetCalendar(ctx context.Context, path string) (*Calendar, error)
+
+	GetCalendarObject(ctx context.Context, path string, req *CalendarCompRequest) (*CalendarObject, error)
+	ListCalendarObjects(ctx context.Context, path string, req *CalendarCompRequest) ([]CalendarObject, error)
+	QueryCalendarObjects(ctx context.Context, path string, query *CalendarQuery) ([]CalendarObject, error)
+	PutCalendarObject(ctx context.Context, path string, calendar *ical.Calendar, opts *PutCalendarObjectOptions) (*CalendarObject, error)
+	DeleteCalendarObject(ctx context.Context, path string) error
+
+	webdav.UserPrincipalBackend
+}
+
+// Handler handles CalDAV HTTP requests. It can be used to create a CalDAV
+// server.
+type Handler struct {
+	Backend Backend
+	Prefix  string
+}
+
+// ServeHTTP implements http.Handler.
+func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if h.Backend == nil {
+		http.Error(w, "caldav: no backend available", http.StatusInternalServerError)
+		return
+	}
+
+	if r.URL.Path == "/.well-known/caldav" {
+		principalPath, err := h.Backend.CurrentUserPrincipal(r.Context())
+		if err != nil {
+			http.Error(w, "caldav: failed to determine current user principal", http.StatusInternalServerError)
+			return
+		}
+
+		http.Redirect(w, r, principalPath, http.StatusPermanentRedirect)
+		return
+	}
+
+	var err error
+	switch r.Method {
+	case "REPORT":
+		err = h.handleReport(w, r)
+	default:
+		b := backend{
+			Backend: h.Backend,
+			Prefix:  strings.TrimSuffix(h.Prefix, "/"),
+		}
+		hh := internal.Handler{Backend: &b}
+		hh.ServeHTTP(w, r)
+	}
+
+	if err != nil {
+		internal.ServeError(w, err)
+	}
+}
+
+func (h *Handler) handleReport(w http.ResponseWriter, r *http.Request) error {
+	var report reportReq
+	if err := internal.DecodeXMLRequest(r, &report); err != nil {
+		return err
+	}
+
+	if report.Query != nil {
+		return h.handleQuery(r, w, report.Query)
+	} else if report.Multiget != nil {
+		return h.handleMultiget(r.Context(), w, report.Multiget)
+	}
+	return internal.HTTPErrorf(http.StatusBadRequest, "caldav: expected calendar-query or calendar-multiget element in REPORT request")
+}
+
+func decodeParamFilter(el *paramFilter) (*ParamFilter, error) {
+	pf := &ParamFilter{Name: el.Name}
+	if el.IsNotDefined != nil {
+		if el.TextMatch != nil {
+			return nil, fmt.Errorf("caldav: failed to parse param-filter: if is-not-defined is provided, text-match can't be provided")
+		}
+		pf.IsNotDefined = true
+	}
+	if el.TextMatch != nil {
+		pf.TextMatch = &TextMatch{Text: el.TextMatch.Text}
+	}
+	return pf, nil
+}
+
+func decodePropFilter(el *propFilter) (*PropFilter, error) {
+	pf := &PropFilter{Name: el.Name}
+	if el.IsNotDefined != nil {
+		if el.TextMatch != nil || el.TimeRange != nil || len(el.ParamFilter) > 0 {
+			return nil, fmt.Errorf("caldav: failed to parse prop-filter: if is-not-defined is provided, text-match, time-range, or param-filter can't be provided")
+		}
+		pf.IsNotDefined = true
+	}
+	if el.TextMatch != nil {
+		pf.TextMatch = &TextMatch{Text: el.TextMatch.Text}
+	}
+	if el.TimeRange != nil {
+		pf.Start = time.Time(el.TimeRange.Start)
+		pf.End = time.Time(el.TimeRange.End)
+	}
+	for _, paramEl := range el.ParamFilter {
+		paramFi, err := decodeParamFilter(&paramEl)
+		if err != nil {
+			return nil, err
+		}
+		pf.ParamFilter = append(pf.ParamFilter, *paramFi)
+	}
+	return pf, nil
+}
+
+func decodeCompFilter(el *compFilter) (*CompFilter, error) {
+	cf := &CompFilter{Name: el.Name}
+	if el.IsNotDefined != nil {
+		if el.TimeRange != nil || len(el.PropFilters) > 0 || len(el.CompFilters) > 0 {
+			return nil, fmt.Errorf("caldav: failed to parse comp-filter: if is-not-defined is provided, time-range, prop-filter, or comp-filter can't be provided")
+		}
+		cf.IsNotDefined = true
+	}
+	if el.TimeRange != nil {
+		cf.Start = time.Time(el.TimeRange.Start)
+		cf.End = time.Time(el.TimeRange.End)
+	}
+	for _, pfEl := range el.PropFilters {
+		pf, err := decodePropFilter(&pfEl)
+		if err != nil {
+			return nil, err
+		}
+		cf.Props = append(cf.Props, *pf)
+	}
+	for _, childEl := range el.CompFilters {
+		child, err := decodeCompFilter(&childEl)
+		if err != nil {
+			return nil, err
+		}
+		cf.Comps = append(cf.Comps, *child)
+	}
+	return cf, nil
+}
+
+func decodeComp(comp *comp) (*CalendarCompRequest, error) {
+	if comp == nil {
+		return nil, internal.HTTPErrorf(http.StatusBadRequest, "caldav: unexpected empty calendar-data in request")
+	}
+	if comp.Allprop != nil && len(comp.Prop) > 0 {
+		return nil, internal.HTTPErrorf(http.StatusBadRequest, "caldav: only one of allprop or prop can be specified in calendar-data")
+	}
+	if comp.Allcomp != nil && len(comp.Comp) > 0 {
+		return nil, internal.HTTPErrorf(http.StatusBadRequest, "caldav: only one of allcomp or comp can be specified in calendar-data")
+	}
+
+	req := &CalendarCompRequest{
+		AllProps: comp.Allprop != nil,
+		AllComps: comp.Allcomp != nil,
+	}
+	for _, p := range comp.Prop {
+		req.Props = append(req.Props, p.Name)
+	}
+	for _, c := range comp.Comp {
+		comp, err := decodeComp(&c)
+		if err != nil {
+			return nil, err
+		}
+		req.Comps = append(req.Comps, *comp)
+	}
+	return req, nil
+}
+
+func decodeCalendarDataReq(calendarData *calendarDataReq) (*CalendarCompRequest, error) {
+	if calendarData.Comp == nil {
+		return &CalendarCompRequest{
+			AllProps: true,
+			AllComps: true,
+		}, nil
+	}
+	return decodeComp(calendarData.Comp)
+}
+
+func (h *Handler) handleQuery(r *http.Request, w http.ResponseWriter, query *calendarQuery) error {
+	var q CalendarQuery
+	// TODO: calendar-data in query.Prop
+	cf, err := decodeCompFilter(&query.Filter.CompFilter)
+	if err != nil {
+		return err
+	}
+	q.CompFilter = *cf
+
+	cos, err := h.Backend.QueryCalendarObjects(r.Context(), r.URL.Path, &q)
+	if err != nil {
+		return err
+	}
+
+	var resps []internal.Response
+	for _, co := range cos {
+		b := backend{
+			Backend: h.Backend,
+			Prefix:  strings.TrimSuffix(h.Prefix, "/"),
+		}
+		propfind := internal.PropFind{
+			Prop:     query.Prop,
+			AllProp:  query.AllProp,
+			PropName: query.PropName,
+		}
+		resp, err := b.propFindCalendarObject(r.Context(), &propfind, &co)
+		if err != nil {
+			return err
+		}
+		resps = append(resps, *resp)
+	}
+
+	ms := internal.NewMultiStatus(resps...)
+
+	return internal.ServeMultiStatus(w, ms)
+}
+
+func (h *Handler) handleMultiget(ctx context.Context, w http.ResponseWriter, multiget *calendarMultiget) error {
+	var dataReq CalendarCompRequest
+	if multiget.Prop != nil {
+		var calendarData calendarDataReq
+		if err := multiget.Prop.Decode(&calendarData); err != nil && !internal.IsNotFound(err) {
+			return err
+		}
+		decoded, err := decodeCalendarDataReq(&calendarData)
+		if err != nil {
+			return err
+		}
+		dataReq = *decoded
+	}
+
+	var resps []internal.Response
+	for _, href := range multiget.Hrefs {
+		co, err := h.Backend.GetCalendarObject(ctx, href.Path, &dataReq)
+		if err != nil {
+			resp := internal.NewErrorResponse(href.Path, err)
+			resps = append(resps, *resp)
+			continue
+		}
+
+		b := backend{
+			Backend: h.Backend,
+			Prefix:  strings.TrimSuffix(h.Prefix, "/"),
+		}
+		propfind := internal.PropFind{
+			Prop:     multiget.Prop,
+			AllProp:  multiget.AllProp,
+			PropName: multiget.PropName,
+		}
+		resp, err := b.propFindCalendarObject(ctx, &propfind, co)
+		if err != nil {
+			return err
+		}
+		resps = append(resps, *resp)
+	}
+
+	ms := internal.NewMultiStatus(resps...)
+	return internal.ServeMultiStatus(w, ms)
+}
+
+type backend struct {
+	Backend Backend
+	Prefix  string
+}
+
+type resourceType int
+
+const (
+	resourceTypeRoot resourceType = iota
+	resourceTypeUserPrincipal
+	resourceTypeCalendarHomeSet
+	resourceTypeCalendar
+	resourceTypeCalendarObject
+)
+
+func (b *backend) resourceTypeAtPath(reqPath string) resourceType {
+	p := path.Clean(reqPath)
+	p = strings.TrimPrefix(p, b.Prefix)
+	if !strings.HasPrefix(p, "/") {
+		p = "/" + p
+	}
+	if p == "/" {
+		return resourceTypeRoot
+	}
+	return resourceType(len(strings.Split(p, "/")) - 1)
+}
+
+func (b *backend) Options(r *http.Request) (caps []string, allow []string, err error) {
+	caps = []string{"calendar-access"}
+
+	if b.resourceTypeAtPath(r.URL.Path) != resourceTypeCalendarObject {
+		return caps, []string{http.MethodOptions, "PROPFIND", "REPORT", "DELETE", "MKCOL"}, nil
+	}
+
+	var dataReq CalendarCompRequest
+	_, err = b.Backend.GetCalendarObject(r.Context(), r.URL.Path, &dataReq)
+	if httpErr, ok := err.(*internal.HTTPError); ok && httpErr.Code == http.StatusNotFound {
+		return caps, []string{http.MethodOptions, http.MethodPut}, nil
+	} else if err != nil {
+		return nil, nil, err
+	}
+
+	return caps, []string{
+		http.MethodOptions,
+		http.MethodHead,
+		http.MethodGet,
+		http.MethodPut,
+		http.MethodDelete,
+		"PROPFIND",
+	}, nil
+}
+
+func (b *backend) HeadGet(w http.ResponseWriter, r *http.Request) error {
+	var dataReq CalendarCompRequest
+	if r.Method != http.MethodHead {
+		dataReq.AllProps = true
+	}
+	co, err := b.Backend.GetCalendarObject(r.Context(), r.URL.Path, &dataReq)
+	if err != nil {
+		return err
+	}
+
+	w.Header().Set("Content-Type", ical.MIMEType)
+	if co.ContentLength > 0 {
+		w.Header().Set("Content-Length", strconv.FormatInt(co.ContentLength, 10))
+	}
+	if co.ETag != "" {
+		w.Header().Set("ETag", internal.ETag(co.ETag).String())
+	}
+	if !co.ModTime.IsZero() {
+		w.Header().Set("Last-Modified", co.ModTime.UTC().Format(http.TimeFormat))
+	}
+
+	if r.Method != http.MethodHead {
+		return ical.NewEncoder(w).Encode(co.Data)
+	}
+	return nil
+}
+
+func (b *backend) PropFind(r *http.Request, propfind *internal.PropFind, depth internal.Depth) (*internal.MultiStatus, error) {
+	resType := b.resourceTypeAtPath(r.URL.Path)
+
+	var dataReq CalendarCompRequest
+	var resps []internal.Response
+
+	switch resType {
+	case resourceTypeRoot:
+		resp, err := b.propFindRoot(r.Context(), propfind)
+		if err != nil {
+			return nil, err
+		}
+		resps = append(resps, *resp)
+	case resourceTypeUserPrincipal:
+		principalPath, err := b.Backend.CurrentUserPrincipal(r.Context())
+		if err != nil {
+			return nil, err
+		}
+		if r.URL.Path == principalPath {
+			resp, err := b.propFindUserPrincipal(r.Context(), propfind)
+			if err != nil {
+				return nil, err
+			}
+			resps = append(resps, *resp)
+			if depth != internal.DepthZero {
+				resp, err := b.propFindHomeSet(r.Context(), propfind)
+				if err != nil {
+					return nil, err
+				}
+				resps = append(resps, *resp)
+				if depth == internal.DepthInfinity {
+					resps_, err := b.propFindAllCalendars(r.Context(), propfind, true)
+					if err != nil {
+						return nil, err
+					}
+					resps = append(resps, resps_...)
+				}
+			}
+		}
+	case resourceTypeCalendarHomeSet:
+		homeSetPath, err := b.Backend.CalendarHomeSetPath(r.Context())
+		if err != nil {
+			return nil, err
+		}
+		if r.URL.Path == homeSetPath {
+			resp, err := b.propFindHomeSet(r.Context(), propfind)
+			if err != nil {
+				return nil, err
+			}
+			resps = append(resps, *resp)
+			if depth != internal.DepthZero {
+				recurse := depth == internal.DepthInfinity
+				resps_, err := b.propFindAllCalendars(r.Context(), propfind, recurse)
+				if err != nil {
+					return nil, err
+				}
+				resps = append(resps, resps_...)
+			}
+		}
+	case resourceTypeCalendar:
+		ab, err := b.Backend.GetCalendar(r.Context(), r.URL.Path)
+		if err != nil {
+			return nil, err
+		}
+		resp, err := b.propFindCalendar(r.Context(), propfind, ab)
+		if err != nil {
+			return nil, err
+		}
+		resps = append(resps, *resp)
+		if depth != internal.DepthZero {
+			resps_, err := b.propFindAllCalendarObjects(r.Context(), propfind, ab)
+			if err != nil {
+				return nil, err
+			}
+			resps = append(resps, resps_...)
+		}
+	case resourceTypeCalendarObject:
+		ao, err := b.Backend.GetCalendarObject(r.Context(), r.URL.Path, &dataReq)
+		if err != nil {
+			return nil, err
+		}
+
+		resp, err := b.propFindCalendarObject(r.Context(), propfind, ao)
+		if err != nil {
+			return nil, err
+		}
+		resps = append(resps, *resp)
+	}
+
+	return internal.NewMultiStatus(resps...), nil
+}
+
+func (b *backend) propFindRoot(ctx context.Context, propfind *internal.PropFind) (*internal.Response, error) {
+	principalPath, err := b.Backend.CurrentUserPrincipal(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: internal.PropFindValue(&internal.CurrentUserPrincipal{
+			Href: internal.Href{Path: principalPath},
+		}),
+		internal.ResourceTypeName: internal.PropFindValue(internal.NewResourceType(internal.CollectionName)),
+	}
+	return internal.NewPropFindResponse(principalPath, propfind, props)
+}
+
+func (b *backend) propFindUserPrincipal(ctx context.Context, propfind *internal.PropFind) (*internal.Response, error) {
+	principalPath, err := b.Backend.CurrentUserPrincipal(ctx)
+	if err != nil {
+		return nil, err
+	}
+	homeSetPath, err := b.Backend.CalendarHomeSetPath(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: internal.PropFindValue(&internal.CurrentUserPrincipal{
+			Href: internal.Href{Path: principalPath},
+		}),
+		calendarHomeSetName: internal.PropFindValue(&calendarHomeSet{
+			Href: internal.Href{Path: homeSetPath},
+		}),
+		internal.ResourceTypeName: internal.PropFindValue(internal.NewResourceType(internal.CollectionName)),
+	}
+	return internal.NewPropFindResponse(principalPath, propfind, props)
+}
+
+func (b *backend) propFindHomeSet(ctx context.Context, propfind *internal.PropFind) (*internal.Response, error) {
+	principalPath, err := b.Backend.CurrentUserPrincipal(ctx)
+	if err != nil {
+		return nil, err
+	}
+	homeSetPath, err := b.Backend.CalendarHomeSetPath(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	// TODO anything else to return here?
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: internal.PropFindValue(&internal.CurrentUserPrincipal{
+			Href: internal.Href{Path: principalPath},
+		}),
+		internal.ResourceTypeName: internal.PropFindValue(internal.NewResourceType(internal.CollectionName)),
+	}
+	return internal.NewPropFindResponse(homeSetPath, propfind, props)
+}
+
+func (b *backend) propFindCalendar(ctx context.Context, propfind *internal.PropFind, cal *Calendar) (*internal.Response, error) {
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: func(*internal.RawXMLValue) (interface{}, error) {
+			path, err := b.Backend.CurrentUserPrincipal(ctx)
+			if err != nil {
+				return nil, err
+			}
+			return &internal.CurrentUserPrincipal{Href: internal.Href{Path: path}}, nil
+		},
+		internal.ResourceTypeName: internal.PropFindValue(internal.NewResourceType(internal.CollectionName, calendarName)),
+		calendarDescriptionName: internal.PropFindValue(&calendarDescription{
+			Description: cal.Description,
+		}),
+		supportedCalendarDataName: internal.PropFindValue(&supportedCalendarData{
+			Types: []calendarDataType{
+				{ContentType: ical.MIMEType, Version: "2.0"},
+			},
+		}),
+		supportedCalendarComponentSetName: func(*internal.RawXMLValue) (interface{}, error) {
+			components := []comp{}
+			if cal.SupportedComponentSet != nil {
+				for _, name := range cal.SupportedComponentSet {
+					components = append(components, comp{Name: name})
+				}
+			} else {
+				components = append(components, comp{Name: ical.CompEvent})
+			}
+			return &supportedCalendarComponentSet{
+				Comp: components,
+			}, nil
+		},
+	}
+
+	if cal.Name != "" {
+		props[internal.DisplayNameName] = internal.PropFindValue(&internal.DisplayName{
+			Name: cal.Name,
+		})
+	}
+	if cal.Description != "" {
+		props[calendarDescriptionName] = internal.PropFindValue(&calendarDescription{
+			Description: cal.Description,
+		})
+	}
+	if cal.MaxResourceSize > 0 {
+		props[maxResourceSizeName] = internal.PropFindValue(&maxResourceSize{
+			Size: cal.MaxResourceSize,
+		})
+	}
+	props[internal.CurrentUserPrivilegeSetName] = func(*internal.RawXMLValue) (interface{}, error) {
+		return &internal.CurrentUserPrivilegeSet{Privilege: internal.NewAllPrivileges()}, nil
+	}
+
+	// TODO: CALDAV:calendar-timezone, CALDAV:supported-calendar-component-set, CALDAV:min-date-time, CALDAV:max-date-time, CALDAV:max-instances, CALDAV:max-attendees-per-instance
+
+	return internal.NewPropFindResponse(cal.Path, propfind, props)
+}
+
+func (b *backend) propFindAllCalendars(ctx context.Context, propfind *internal.PropFind, recurse bool) ([]internal.Response, error) {
+	abs, err := b.Backend.ListCalendars(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	var resps []internal.Response
+	for _, ab := range abs {
+		resp, err := b.propFindCalendar(ctx, propfind, &ab)
+		if err != nil {
+			return nil, err
+		}
+		resps = append(resps, *resp)
+		if recurse {
+			resps_, err := b.propFindAllCalendarObjects(ctx, propfind, &ab)
+			if err != nil {
+				return nil, err
+			}
+			resps = append(resps, resps_...)
+		}
+	}
+	return resps, nil
+}
+
+func (b *backend) propFindCalendarObject(ctx context.Context, propfind *internal.PropFind, co *CalendarObject) (*internal.Response, error) {
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: func(*internal.RawXMLValue) (interface{}, error) {
+			path, err := b.Backend.CurrentUserPrincipal(ctx)
+			if err != nil {
+				return nil, err
+			}
+			return &internal.CurrentUserPrincipal{Href: internal.Href{Path: path}}, nil
+		},
+		internal.GetContentTypeName: internal.PropFindValue(&internal.GetContentType{
+			Type: ical.MIMEType,
+		}),
+		// TODO: calendar-data can only be used in REPORT requests
+		calendarDataName: func(*internal.RawXMLValue) (interface{}, error) {
+			var buf bytes.Buffer
+			if err := ical.NewEncoder(&buf).Encode(co.Data); err != nil {
+				return nil, err
+			}
+
+			return &calendarDataResp{Data: buf.Bytes()}, nil
+		},
+	}
+
+	if co.ContentLength > 0 {
+		props[internal.GetContentLengthName] = internal.PropFindValue(&internal.GetContentLength{
+			Length: co.ContentLength,
+		})
+	}
+	if !co.ModTime.IsZero() {
+		props[internal.GetLastModifiedName] = internal.PropFindValue(&internal.GetLastModified{
+			LastModified: internal.Time(co.ModTime),
+		})
+	}
+
+	if co.ETag != "" {
+		props[internal.GetETagName] = internal.PropFindValue(&internal.GetETag{
+			ETag: internal.ETag(co.ETag),
+		})
+	}
+
+	return internal.NewPropFindResponse(co.Path, propfind, props)
+}
+
+func (b *backend) propFindAllCalendarObjects(ctx context.Context, propfind *internal.PropFind, cal *Calendar) ([]internal.Response, error) {
+	var dataReq CalendarCompRequest
+	aos, err := b.Backend.ListCalendarObjects(ctx, cal.Path, &dataReq)
+	if err != nil {
+		return nil, err
+	}
+
+	var resps []internal.Response
+	for _, ao := range aos {
+		resp, err := b.propFindCalendarObject(ctx, propfind, &ao)
+		if err != nil {
+			return nil, err
+		}
+		resps = append(resps, *resp)
+	}
+	return resps, nil
+}
+
+func (b *backend) PropPatch(r *http.Request, update *internal.PropertyUpdate) (*internal.Response, error) {
+	return nil, internal.HTTPErrorf(http.StatusNotImplemented, "caldav: PropPatch not implemented")
+}
+
+func (b *backend) Put(w http.ResponseWriter, r *http.Request) error {
+	ifNoneMatch := webdav.ConditionalMatch(r.Header.Get("If-None-Match"))
+	ifMatch := webdav.ConditionalMatch(r.Header.Get("If-Match"))
+
+	opts := PutCalendarObjectOptions{
+		IfNoneMatch: ifNoneMatch,
+		IfMatch:     ifMatch,
+	}
+
+	t, _, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
+	if err != nil {
+		return internal.HTTPErrorf(http.StatusBadRequest, "caldav: malformed Content-Type: %v", err)
+	}
+	if t != ical.MIMEType {
+		// TODO: send CALDAV:supported-calendar-data error
+		return internal.HTTPErrorf(http.StatusBadRequest, "caldav: unsupported Content-Type %q", t)
+	}
+
+	// TODO: check CALDAV:max-resource-size precondition
+	cal, err := ical.NewDecoder(r.Body).Decode()
+	if err != nil {
+		// TODO: send CALDAV:valid-calendar-data error
+		return internal.HTTPErrorf(http.StatusBadRequest, "caldav: failed to parse iCalendar: %v", err)
+	}
+
+	co, err := b.Backend.PutCalendarObject(r.Context(), r.URL.Path, cal, &opts)
+	if err != nil {
+		return err
+	}
+
+	if co.ETag != "" {
+		w.Header().Set("ETag", internal.ETag(co.ETag).String())
+	}
+	if !co.ModTime.IsZero() {
+		w.Header().Set("Last-Modified", co.ModTime.UTC().Format(http.TimeFormat))
+	}
+	if co.Path != "" {
+		w.Header().Set("Location", co.Path)
+	}
+
+	// TODO: http.StatusNoContent if the resource already existed
+	w.WriteHeader(http.StatusCreated)
+
+	return nil
+}
+
+func (b *backend) Delete(r *http.Request) error {
+	return b.Backend.DeleteCalendarObject(r.Context(), r.URL.Path)
+}
+
+func (b *backend) Mkcol(r *http.Request) error {
+	if b.resourceTypeAtPath(r.URL.Path) != resourceTypeCalendar {
+		return internal.HTTPErrorf(http.StatusForbidden, "caldav: calendar creation not allowed at given location")
+	}
+
+	cal := Calendar{
+		Path: r.URL.Path,
+	}
+
+	if !internal.IsRequestBodyEmpty(r) {
+		var m mkcolReq
+		if err := internal.DecodeXMLRequest(r, &m); err != nil {
+			return internal.HTTPErrorf(http.StatusBadRequest, "carddav: error parsing mkcol request: %s", err.Error())
+		}
+
+		if !m.ResourceType.Is(internal.CollectionName) || !m.ResourceType.Is(calendarName) {
+			return internal.HTTPErrorf(http.StatusBadRequest, "carddav: unexpected resource type")
+		}
+		cal.Name = m.DisplayName
+		// TODO ...
+	}
+
+	return b.Backend.CreateCalendar(r.Context(), &cal)
+}
+
+func (b *backend) Copy(r *http.Request, dest *internal.Href, recursive, overwrite bool) (created bool, err error) {
+	return false, internal.HTTPErrorf(http.StatusNotImplemented, "caldav: Copy not implemented")
+}
+
+func (b *backend) Move(r *http.Request, dest *internal.Href, overwrite bool) (created bool, err error) {
+	return false, internal.HTTPErrorf(http.StatusNotImplemented, "caldav: Move not implemented")
+}
+
+// https://datatracker.ietf.org/doc/html/rfc4791#section-5.3.2.1
+type PreconditionType string
+
+const (
+	PreconditionNoUIDConflict                PreconditionType = "no-uid-conflict"
+	PreconditionSupportedCalendarData        PreconditionType = "supported-calendar-data"
+	PreconditionSupportedCalendarComponent   PreconditionType = "supported-calendar-component"
+	PreconditionValidCalendarData            PreconditionType = "valid-calendar-data"
+	PreconditionValidCalendarObjectResource  PreconditionType = "valid-calendar-object-resource"
+	PreconditionCalendarCollectionLocationOk PreconditionType = "calendar-collection-location-ok"
+	PreconditionMaxResourceSize              PreconditionType = "max-resource-size"
+	PreconditionMinDateTime                  PreconditionType = "min-date-time"
+	PreconditionMaxDateTime                  PreconditionType = "max-date-time"
+	PreconditionMaxInstances                 PreconditionType = "max-instances"
+	PreconditionMaxAttendeesPerInstance      PreconditionType = "max-attendees-per-instance"
+)
+
+func NewPreconditionError(err PreconditionType) error {
+	name := xml.Name{Space: "urn:ietf:params:xml:ns:caldav", Local: string(err)}
+	elem := internal.NewRawXMLElement(name, nil, nil)
+	return &internal.HTTPError{
+		Code: 409,
+		Err: &internal.Error{
+			Raw: []internal.RawXMLValue{*elem},
+		},
+	}
+}

caldav/server_test.go

@@ -0,0 +1,235 @@
+package caldav
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/emersion/go-ical"
+)
+
+var propFindSupportedCalendarComponentRequest = `
+<d:propfind xmlns:d="DAV:" xmlns:c="urn:ietf:params:xml:ns:caldav">
+  <d:prop>
+     <c:supported-calendar-component-set />
+  </d:prop>
+</d:propfind>
+`
+
+var testPropFindSupportedCalendarComponentCases = map[*Calendar][]string{
+	&Calendar{Path: "/user/calendars/cal"}:                                                     []string{"VEVENT"},
+	&Calendar{Path: "/user/calendars/cal", SupportedComponentSet: []string{"VTODO"}}:           []string{"VTODO"},
+	&Calendar{Path: "/user/calendars/cal", SupportedComponentSet: []string{"VEVENT", "VTODO"}}: []string{"VEVENT", "VTODO"},
+}
+
+func TestPropFindSupportedCalendarComponent(t *testing.T) {
+	for calendar, expected := range testPropFindSupportedCalendarComponentCases {
+		req := httptest.NewRequest("PROPFIND", calendar.Path, nil)
+		req.Body = io.NopCloser(strings.NewReader(propFindSupportedCalendarComponentRequest))
+		req.Header.Set("Content-Type", "application/xml")
+		w := httptest.NewRecorder()
+		handler := Handler{Backend: testBackend{calendars: []Calendar{*calendar}}}
+		handler.ServeHTTP(w, req)
+
+		res := w.Result()
+		defer res.Body.Close()
+		data, err := ioutil.ReadAll(res.Body)
+		if err != nil {
+			t.Error(err)
+		}
+		resp := string(data)
+		for _, comp := range expected {
+			// Would be nicer to do a proper XML-decoding here, but this is probably good enough for now.
+			if !strings.Contains(resp, comp) {
+				t.Errorf("Expected component: %v not found in response:\n%v", comp, resp)
+			}
+		}
+	}
+}
+
+var propFindUserPrincipal = `
+<?xml version="1.0" encoding="UTF-8"?>
+<A:propfind xmlns:A="DAV:">
+  <A:prop>
+    <A:current-user-principal/>
+    <A:principal-URL/>
+    <A:resourcetype/>
+  </A:prop>
+</A:propfind>
+`
+
+func TestPropFindRoot(t *testing.T) {
+	req := httptest.NewRequest("PROPFIND", "/", strings.NewReader(propFindUserPrincipal))
+	req.Header.Set("Content-Type", "application/xml")
+	w := httptest.NewRecorder()
+	calendar := &Calendar{}
+	handler := Handler{Backend: testBackend{calendars: []Calendar{*calendar}}}
+	handler.ServeHTTP(w, req)
+
+	res := w.Result()
+	defer res.Body.Close()
+	data, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Error(err)
+	}
+	resp := string(data)
+	if !strings.Contains(resp, `<current-user-principal xmlns="DAV:"><href>/user/</href></current-user-principal>`) {
+		t.Errorf("No user-principal returned when doing a PROPFIND against root, response:\n%s", resp)
+	}
+}
+
+var reportCalendarData = `
+<?xml version="1.0" encoding="UTF-8"?>
+<B:calendar-multiget xmlns:A="DAV:" xmlns:B="urn:ietf:params:xml:ns:caldav">
+  <A:prop>
+    <B:calendar-data/>
+  </A:prop>
+  <A:href>%s</A:href>
+</B:calendar-multiget>
+`
+
+func TestMultiCalendarBackend(t *testing.T) {
+	calendarB := Calendar{Path: "/user/calendars/b", SupportedComponentSet: []string{"VTODO"}}
+	calendars := []Calendar{
+		Calendar{Path: "/user/calendars/a"},
+		calendarB,
+	}
+	eventSummary := "This is a todo"
+	event := ical.NewEvent()
+	event.Name = ical.CompToDo
+	event.Props.SetText(ical.PropUID, "46bbf47a-1861-41a3-ae06-8d8268c6d41e")
+	event.Props.SetDateTime(ical.PropDateTimeStamp, time.Now())
+	event.Props.SetText(ical.PropSummary, eventSummary)
+	cal := ical.NewCalendar()
+	cal.Props.SetText(ical.PropVersion, "2.0")
+	cal.Props.SetText(ical.PropProductID, "-//xyz Corp//NONSGML PDA Calendar Version 1.0//EN")
+	cal.Children = []*ical.Component{
+		event.Component,
+	}
+	object := CalendarObject{
+		Path: "/user/calendars/b/test.ics",
+		Data: cal,
+	}
+	req := httptest.NewRequest("PROPFIND", "/user/calendars/", strings.NewReader(propFindUserPrincipal))
+	req.Header.Set("Content-Type", "application/xml")
+	w := httptest.NewRecorder()
+	handler := Handler{Backend: testBackend{
+		calendars: calendars,
+		objectMap: map[string][]CalendarObject{
+			calendarB.Path: []CalendarObject{object},
+		},
+	}}
+	handler.ServeHTTP(w, req)
+
+	res := w.Result()
+	defer res.Body.Close()
+	data, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Error(err)
+	}
+	resp := string(data)
+	for _, calendar := range calendars {
+		if !strings.Contains(resp, fmt.Sprintf(`<response xmlns="DAV:"><href>%s</href>`, calendar.Path)) {
+			t.Errorf("Calendar: %v not returned in PROPFIND, response:\n%s", calendar, resp)
+		}
+	}
+
+	// Now do a PROPFIND for the last calendar
+	req = httptest.NewRequest("PROPFIND", calendarB.Path, strings.NewReader(propFindSupportedCalendarComponentRequest))
+	req.Header.Set("Content-Type", "application/xml")
+	w = httptest.NewRecorder()
+	handler.ServeHTTP(w, req)
+
+	res = w.Result()
+	defer res.Body.Close()
+	data, err = ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Error(err)
+	}
+	resp = string(data)
+	if !strings.Contains(resp, "VTODO") {
+		t.Errorf("Expected component: VTODO not found in response:\n%v", resp)
+	}
+	if !strings.Contains(resp, object.Path) {
+		t.Errorf("Expected calendar object: %v not found in response:\n%v", object, resp)
+	}
+
+	// Now do a REPORT to get the actual data for the event
+	req = httptest.NewRequest("REPORT", calendarB.Path, strings.NewReader(fmt.Sprintf(reportCalendarData, object.Path)))
+	req.Header.Set("Content-Type", "application/xml")
+	w = httptest.NewRecorder()
+	handler.ServeHTTP(w, req)
+
+	res = w.Result()
+	defer res.Body.Close()
+	data, err = ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Error(err)
+	}
+	resp = string(data)
+	if !strings.Contains(resp, fmt.Sprintf("SUMMARY:%s", eventSummary)) {
+		t.Errorf("ICAL content not properly returned in response:\n%v", resp)
+	}
+}
+
+type testBackend struct {
+	calendars []Calendar
+	objectMap map[string][]CalendarObject
+}
+
+func (t testBackend) CreateCalendar(ctx context.Context, calendar *Calendar) error {
+	return nil
+}
+
+func (t testBackend) ListCalendars(ctx context.Context) ([]Calendar, error) {
+	return t.calendars, nil
+}
+
+func (t testBackend) GetCalendar(ctx context.Context, path string) (*Calendar, error) {
+	for _, cal := range t.calendars {
+		if cal.Path == path {
+			return &cal, nil
+		}
+	}
+	return nil, fmt.Errorf("Calendar for path: %s not found", path)
+}
+
+func (t testBackend) CalendarHomeSetPath(ctx context.Context) (string, error) {
+	return "/user/calendars/", nil
+}
+
+func (t testBackend) CurrentUserPrincipal(ctx context.Context) (string, error) {
+	return "/user/", nil
+}
+
+func (t testBackend) DeleteCalendarObject(ctx context.Context, path string) error {
+	return nil
+}
+
+func (t testBackend) GetCalendarObject(ctx context.Context, path string, req *CalendarCompRequest) (*CalendarObject, error) {
+	for _, objs := range t.objectMap {
+		for _, obj := range objs {
+			if obj.Path == path {
+				return &obj, nil
+			}
+		}
+	}
+	return nil, fmt.Errorf("Couldn't find calendar object at: %s", path)
+}
+
+func (t testBackend) PutCalendarObject(ctx context.Context, path string, calendar *ical.Calendar, opts *PutCalendarObjectOptions) (*CalendarObject, error) {
+	return nil, nil
+}
+
+func (t testBackend) ListCalendarObjects(ctx context.Context, path string, req *CalendarCompRequest) ([]CalendarObject, error) {
+	return t.objectMap[path], nil
+}
+
+func (t testBackend) QueryCalendarObjects(ctx context.Context, path string, query *CalendarQuery) ([]CalendarObject, error) {
+	return nil, nil
+}

carddav/carddav.go

@@ -7,8 +7,16 @@ import (
 	"time"
 
 	"github.com/emersion/go-vcard"
+	"github.com/emersion/go-webdav"
+	"github.com/emersion/go-webdav/internal"
 )
 
+var CapabilityAddressBook = webdav.Capability("addressbook")
+
+func NewAddressBookHomeSet(path string) webdav.BackendSuppliedHomeSet {
+	return &addressbookHomeSet{Href: internal.Href{Path: path}}
+}
+
 type AddressDataType struct {
 	ContentType string
 	Version     string
@@ -94,8 +102,23 @@ type AddressBookMultiGet struct {
 }
 
 type AddressObject struct {
-	Path    string
-	ModTime time.Time
-	ETag    string
-	Card    vcard.Card
+	Path          string
+	ModTime       time.Time
+	ContentLength int64
+	ETag          string
+	Card          vcard.Card
+}
+
+// SyncQuery is the query struct represents a sync-collection request
+type SyncQuery struct {
+	DataRequest AddressDataRequest
+	SyncToken   string
+	Limit       int // <= 0 means unlimited
+}
+
+// SyncResponse contains the returned sync-token for next time
+type SyncResponse struct {
+	SyncToken string
+	Updated   []AddressObject
+	Deleted   []string
 }

carddav/carddav_test.go

@@ -0,0 +1,242 @@
+package carddav
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/emersion/go-vcard"
+	"github.com/emersion/go-webdav"
+)
+
+type testBackend struct {
+	addressBooks []AddressBook
+}
+
+type contextKey string
+
+var (
+	aliceData = `BEGIN:VCARD
+VERSION:4.0
+UID:urn:uuid:4fbe8971-0bc3-424c-9c26-36c3e1eff6b1
+FN;PID=1.1:Alice Gopher
+N:Gopher;Alice;;;
+EMAIL;PID=1.1:alice@example.com
+CLIENTPIDMAP:1;urn:uuid:53e374d9-337e-4727-8803-a1e9c14e0551
+END:VCARD`
+	alicePath = "urn:uuid:4fbe8971-0bc3-424c-9c26-36c3e1eff6b1.vcf"
+
+	currentUserPrincipalKey = contextKey("test:currentUserPrincipal")
+	homeSetPathKey          = contextKey("test:homeSetPath")
+	addressBookPathKey      = contextKey("test:addressBookPath")
+)
+
+func (*testBackend) CurrentUserPrincipal(ctx context.Context) (string, error) {
+	r := ctx.Value(currentUserPrincipalKey).(string)
+	return r, nil
+}
+
+func (*testBackend) AddressBookHomeSetPath(ctx context.Context) (string, error) {
+	r := ctx.Value(homeSetPathKey).(string)
+	return r, nil
+}
+
+func (*testBackend) ListAddressBooks(ctx context.Context) ([]AddressBook, error) {
+	p := ctx.Value(addressBookPathKey).(string)
+	return []AddressBook{
+		AddressBook{
+			Path:                 p,
+			Name:                 "My contacts",
+			Description:          "Default address book",
+			MaxResourceSize:      1024,
+			SupportedAddressData: nil,
+		},
+	}, nil
+}
+
+func (b *testBackend) GetAddressBook(ctx context.Context, path string) (*AddressBook, error) {
+	abs, err := b.ListAddressBooks(ctx)
+	if err != nil {
+		panic(err)
+	}
+	for _, ab := range abs {
+		if ab.Path == path {
+			return &ab, nil
+		}
+	}
+	return nil, webdav.NewHTTPError(404, fmt.Errorf("Not found"))
+}
+
+func (b *testBackend) CreateAddressBook(ctx context.Context, ab *AddressBook) error {
+	b.addressBooks = append(b.addressBooks, *ab)
+	return nil
+}
+
+func (*testBackend) DeleteAddressBook(ctx context.Context, path string) error {
+	panic("TODO: implement")
+}
+
+func (*testBackend) GetAddressObject(ctx context.Context, path string, req *AddressDataRequest) (*AddressObject, error) {
+	if path == alicePath {
+		card, err := vcard.NewDecoder(strings.NewReader(aliceData)).Decode()
+		if err != nil {
+			return nil, err
+		}
+		return &AddressObject{
+			Path: path,
+			Card: card,
+		}, nil
+	} else {
+		return nil, webdav.NewHTTPError(404, fmt.Errorf("Not found"))
+	}
+}
+
+func (b *testBackend) ListAddressObjects(ctx context.Context, path string, req *AddressDataRequest) ([]AddressObject, error) {
+	p := ctx.Value(addressBookPathKey).(string)
+	if !strings.HasPrefix(path, p) {
+		return nil, webdav.NewHTTPError(404, fmt.Errorf("Not found"))
+	}
+	alice, err := b.GetAddressObject(ctx, alicePath, req)
+	if err != nil {
+		return nil, err
+	}
+
+	return []AddressObject{*alice}, nil
+}
+
+func (*testBackend) QueryAddressObjects(ctx context.Context, path string, query *AddressBookQuery) ([]AddressObject, error) {
+	panic("TODO: implement")
+}
+
+func (*testBackend) PutAddressObject(ctx context.Context, path string, card vcard.Card, opts *PutAddressObjectOptions) (*AddressObject, error) {
+	panic("TODO: implement")
+}
+
+func (*testBackend) DeleteAddressObject(ctx context.Context, path string) error {
+	panic("TODO: implement")
+}
+
+func TestAddressBookDiscovery(t *testing.T) {
+	for _, tc := range []struct {
+		name                 string
+		prefix               string
+		currentUserPrincipal string
+		homeSetPath          string
+		addressBookPath      string
+	}{
+		{
+			name:                 "simple",
+			prefix:               "",
+			currentUserPrincipal: "/test/",
+			homeSetPath:          "/test/contacts/",
+			addressBookPath:      "/test/contacts/private",
+		},
+		{
+			name:                 "prefix",
+			prefix:               "/dav",
+			currentUserPrincipal: "/dav/test/",
+			homeSetPath:          "/dav/test/contacts/",
+			addressBookPath:      "/dav/test/contacts/private",
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx := context.Background()
+
+			h := Handler{&testBackend{}, tc.prefix}
+			ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				ctx := r.Context()
+				ctx = context.WithValue(ctx, currentUserPrincipalKey, tc.currentUserPrincipal)
+				ctx = context.WithValue(ctx, homeSetPathKey, tc.homeSetPath)
+				ctx = context.WithValue(ctx, addressBookPathKey, tc.addressBookPath)
+				r = r.WithContext(ctx)
+				(&h).ServeHTTP(w, r)
+			}))
+			defer ts.Close()
+
+			// client supports .well-known discovery if explicitly pointed to it
+			startURL := ts.URL
+			if tc.currentUserPrincipal != "/" {
+				startURL = ts.URL + "/.well-known/carddav"
+			}
+
+			client, err := NewClient(nil, startURL)
+			if err != nil {
+				t.Fatalf("error creating client: %s", err)
+			}
+			cup, err := client.FindCurrentUserPrincipal(ctx)
+			if err != nil {
+				t.Fatalf("error finding user principal url: %s", err)
+			}
+			if cup != tc.currentUserPrincipal {
+				t.Fatalf("Found current user principal URL '%s', expected '%s'", cup, tc.currentUserPrincipal)
+			}
+			hsp, err := client.FindAddressBookHomeSet(ctx, cup)
+			if err != nil {
+				t.Fatalf("error finding home set path: %s", err)
+			}
+			if hsp != tc.homeSetPath {
+				t.Fatalf("Found home set path '%s', expected '%s'", hsp, tc.homeSetPath)
+			}
+			abs, err := client.FindAddressBooks(ctx, hsp)
+			if err != nil {
+				t.Fatalf("error finding address books: %s", err)
+			}
+			if len(abs) != 1 {
+				t.Fatalf("Found %d address books, expected 1", len(abs))
+			}
+			if abs[0].Path != tc.addressBookPath {
+				t.Fatalf("Found address book at %s, expected %s", abs[0].Path, tc.addressBookPath)
+			}
+		})
+	}
+}
+
+var mkcolRequestBody = `
+<?xml version="1.0" encoding="utf-8" ?>
+   <D:mkcol xmlns:D="DAV:"
+                 xmlns:C="urn:ietf:params:xml:ns:carddav">
+     <D:set>
+       <D:prop>
+         <D:resourcetype>
+           <D:collection/>
+           <C:addressbook/>
+         </D:resourcetype>
+         <D:displayname>Lisa's Contacts</D:displayname>
+         <C:addressbook-description xml:lang="en"
+   >My primary address book.</C:addressbook-description>
+       </D:prop>
+     </D:set>
+   </D:mkcol>`
+
+func TestCreateAddressbookMinimalBody(t *testing.T) {
+	tb := testBackend{
+		addressBooks: nil,
+	}
+	b := backend{
+		Backend: &tb,
+		Prefix:  "/dav",
+	}
+	req := httptest.NewRequest("MKCOL", "/dav/addressbooks/user0/test-addressbook", strings.NewReader(mkcolRequestBody))
+	req.Header.Set("Content-Type", "application/xml")
+
+	err := b.Mkcol(req)
+	if err != nil {
+		t.Fatalf("Unexpcted error in Mkcol: %s", err)
+	}
+	if len(tb.addressBooks) != 1 {
+		t.Fatalf("Found %d address books, expected 1", len(tb.addressBooks))
+	}
+	c := tb.addressBooks[0]
+	if c.Name != "Lisa's Contacts" {
+		t.Fatalf("Address book name is '%s', expected 'Lisa's Contacts'", c.Name)
+	}
+	if c.Path != "/dav/addressbooks/user0/test-addressbook" {
+		t.Fatalf("Address book path is '%s', expected '/dav/addressbooks/user0/test-addressbook'", c.Path)
+	}
+	if c.Description != "My primary address book." {
+		t.Fatalf("Address book sdscription is '%s', expected 'My primary address book.'", c.Description)
+	}
+}

carddav/client.go

@@ -2,9 +2,9 @@ package carddav
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"mime"
-	"net"
 	"net/http"
 	"net/url"
 	"strconv"
@@ -16,36 +16,10 @@ import (
 	"github.com/emersion/go-webdav/internal"
 )
 
-// Discover performs a DNS-based CardDAV service discovery as described in
-// RFC 6352 section 11. It returns the URL to the CardDAV server.
-func Discover(domain string) (string, error) {
-	// Only lookup carddavs (not carddav), plaintext connections are insecure
-	_, addrs, err := net.LookupSRV("carddavs", "tcp", domain)
-	if dnsErr, ok := err.(*net.DNSError); ok {
-		if dnsErr.IsTemporary {
-			return "", err
-		}
-	} else if err != nil {
-		return "", err
-	}
-
-	if len(addrs) == 0 {
-		return "", fmt.Errorf("carddav: domain doesn't have an SRV record")
-	}
-	addr := addrs[0]
-
-	target := strings.TrimSuffix(addr.Target, ".")
-	if target == "" {
-		return "", fmt.Errorf("carddav: empty target in SRV record")
-	}
-
-	u := url.URL{Scheme: "https"}
-	if addr.Port == 443 {
-		u.Host = target
-	} else {
-		u.Host = fmt.Sprintf("%v:%v", target, addr.Port)
-	}
-	return u.String(), nil
+// DiscoverContextURL performs a DNS-based CardDAV service discovery as
+// described in RFC 6352 section 11. It returns the URL to the CardDAV server.
+func DiscoverContextURL(ctx context.Context, domain string) (string, error) {
+	return internal.DiscoverContextURL(ctx, "carddavs", domain)
 }
 
 // Client provides access to a remote CardDAV server.
@@ -67,8 +41,8 @@ func NewClient(c webdav.HTTPClient, endpoint string) (*Client, error) {
 	return &Client{wc, ic}, nil
 }
 
-func (c *Client) HasSupport() error {
-	classes, _, err := c.ic.Options("")
+func (c *Client) HasSupport(ctx context.Context) error {
+	classes, _, err := c.ic.Options(ctx, "")
 	if err != nil {
 		return err
 	}
@@ -79,9 +53,9 @@ func (c *Client) HasSupport() error {
 	return nil
 }
 
-func (c *Client) FindAddressBookHomeSet(principal string) (string, error) {
-	propfind := internal.NewPropNamePropfind(addressBookHomeSetName)
-	resp, err := c.ic.PropfindFlat(principal, propfind)
+func (c *Client) FindAddressBookHomeSet(ctx context.Context, principal string) (string, error) {
+	propfind := internal.NewPropNamePropFind(addressBookHomeSetName)
+	resp, err := c.ic.PropFindFlat(ctx, principal, propfind)
 	if err != nil {
 		return "", err
 	}
@@ -102,15 +76,15 @@ func decodeSupportedAddressData(supported *supportedAddressData) []AddressDataTy
 	return l
 }
 
-func (c *Client) FindAddressBooks(addressBookHomeSet string) ([]AddressBook, error) {
-	propfind := internal.NewPropNamePropfind(
+func (c *Client) FindAddressBooks(ctx context.Context, addressBookHomeSet string) ([]AddressBook, error) {
+	propfind := internal.NewPropNamePropFind(
 		internal.ResourceTypeName,
 		internal.DisplayNameName,
 		addressBookDescriptionName,
 		maxResourceSizeName,
 		supportedAddressDataName,
 	)
-	ms, err := c.ic.Propfind(addressBookHomeSet, internal.DepthOne, propfind)
+	ms, err := c.ic.PropFind(ctx, addressBookHomeSet, internal.DepthOne, propfind)
 	if err != nil {
 		return nil, err
 	}
@@ -223,7 +197,7 @@ func encodeTextMatch(tm *TextMatch) *textMatch {
 	}
 }
 
-func decodeAddressList(ms *internal.Multistatus) ([]AddressObject, error) {
+func decodeAddressList(ms *internal.MultiStatus) ([]AddressObject, error) {
 	addrs := make([]AddressObject, 0, len(ms.Responses))
 	for _, resp := range ms.Responses {
 		path, err := resp.Path()
@@ -246,6 +220,11 @@ func decodeAddressList(ms *internal.Multistatus) ([]AddressObject, error) {
 			return nil, err
 		}
 
+		var getContentLength internal.GetContentLength
+		if err := resp.DecodeProp(&getContentLength); err != nil && !internal.IsNotFound(err) {
+			return nil, err
+		}
+
 		r := bytes.NewReader(addrData.Data)
 		card, err := vcard.NewDecoder(r).Decode()
 		if err != nil {
@@ -253,17 +232,18 @@ func decodeAddressList(ms *internal.Multistatus) ([]AddressObject, error) {
 		}
 
 		addrs = append(addrs, AddressObject{
-			Path:    path,
-			ModTime: time.Time(getLastMod.LastModified),
-			ETag:    string(getETag.ETag),
-			Card:    card,
+			Path:          path,
+			ModTime:       time.Time(getLastMod.LastModified),
+			ContentLength: getContentLength.Length,
+			ETag:          string(getETag.ETag),
+			Card:          card,
 		})
 	}
 
 	return addrs, nil
 }
 
-func (c *Client) QueryAddressBook(addressBook string, query *AddressBookQuery) ([]AddressObject, error) {
+func (c *Client) QueryAddressBook(ctx context.Context, addressBook string, query *AddressBookQuery) ([]AddressObject, error) {
 	propReq, err := encodeAddressPropReq(&query.DataRequest)
 	if err != nil {
 		return nil, err
@@ -289,7 +269,7 @@ func (c *Client) QueryAddressBook(addressBook string, query *AddressBookQuery) (
 
 	req.Header.Add("Depth", "1")
 
-	ms, err := c.ic.DoMultiStatus(req)
+	ms, err := c.ic.DoMultiStatus(req.WithContext(ctx))
 	if err != nil {
 		return nil, err
 	}
@@ -297,7 +277,7 @@ func (c *Client) QueryAddressBook(addressBook string, query *AddressBookQuery) (
 	return decodeAddressList(ms)
 }
 
-func (c *Client) MultiGetAddressBook(path string, multiGet *AddressBookMultiGet) ([]AddressObject, error) {
+func (c *Client) MultiGetAddressBook(ctx context.Context, path string, multiGet *AddressBookMultiGet) ([]AddressObject, error) {
 	propReq, err := encodeAddressPropReq(&multiGet.DataRequest)
 	if err != nil {
 		return nil, err
@@ -305,7 +285,7 @@ func (c *Client) MultiGetAddressBook(path string, multiGet *AddressBookMultiGet)
 
 	addressbookMultiget := addressbookMultiget{Prop: propReq}
 
-	if multiGet == nil || len(multiGet.Paths) == 0 {
+	if len(multiGet.Paths) == 0 {
 		href := internal.Href{Path: path}
 		addressbookMultiget.Hrefs = []internal.Href{href}
 	} else {
@@ -322,7 +302,7 @@ func (c *Client) MultiGetAddressBook(path string, multiGet *AddressBookMultiGet)
 
 	req.Header.Add("Depth", "1")
 
-	ms, err := c.ic.DoMultiStatus(req)
+	ms, err := c.ic.DoMultiStatus(req.WithContext(ctx))
 	if err != nil {
 		return nil, err
 	}
@@ -330,22 +310,29 @@ func (c *Client) MultiGetAddressBook(path string, multiGet *AddressBookMultiGet)
 	return decodeAddressList(ms)
 }
 
-func populateAddressObject(ao *AddressObject, resp *http.Response) error {
-	if loc := resp.Header.Get("Location"); loc != "" {
+func populateAddressObject(ao *AddressObject, h http.Header) error {
+	if loc := h.Get("Location"); loc != "" {
 		u, err := url.Parse(loc)
 		if err != nil {
 			return err
 		}
 		ao.Path = u.Path
 	}
-	if etag := resp.Header.Get("ETag"); etag != "" {
+	if etag := h.Get("ETag"); etag != "" {
 		etag, err := strconv.Unquote(etag)
 		if err != nil {
 			return err
 		}
 		ao.ETag = etag
 	}
-	if lastModified := resp.Header.Get("Last-Modified"); lastModified != "" {
+	if contentLength := h.Get("Content-Length"); contentLength != "" {
+		n, err := strconv.ParseInt(contentLength, 10, 64)
+		if err != nil {
+			return err
+		}
+		ao.ContentLength = n
+	}
+	if lastModified := h.Get("Last-Modified"); lastModified != "" {
 		t, err := http.ParseTime(lastModified)
 		if err != nil {
 			return err
@@ -356,14 +343,14 @@ func populateAddressObject(ao *AddressObject, resp *http.Response) error {
 	return nil
 }
 
-func (c *Client) GetAddressObject(path string) (*AddressObject, error) {
+func (c *Client) GetAddressObject(ctx context.Context, path string) (*AddressObject, error) {
 	req, err := c.ic.NewRequest(http.MethodGet, path, nil)
 	if err != nil {
 		return nil, err
 	}
 	req.Header.Set("Accept", vcard.MIMEType)
 
-	resp, err := c.ic.Do(req)
+	resp, err := c.ic.Do(req.WithContext(ctx))
 	if err != nil {
 		return nil, err
 	}
@@ -386,13 +373,13 @@ func (c *Client) GetAddressObject(path string) (*AddressObject, error) {
 		Path: resp.Request.URL.Path,
 		Card: card,
 	}
-	if err := populateAddressObject(ao, resp); err != nil {
+	if err := populateAddressObject(ao, resp.Header); err != nil {
 		return nil, err
 	}
 	return ao, nil
 }
 
-func (c *Client) PutAddressObject(path string, card vcard.Card) (*AddressObject, error) {
+func (c *Client) PutAddressObject(ctx context.Context, path string, card vcard.Card) (*AddressObject, error) {
 	// TODO: add support for If-None-Match and If-Match
 
 	// TODO: some servers want a Content-Length header, so we can't stream the
@@ -417,15 +404,69 @@ func (c *Client) PutAddressObject(path string, card vcard.Card) (*AddressObject,
 	}
 	req.Header.Set("Content-Type", vcard.MIMEType)
 
-	resp, err := c.ic.Do(req)
+	resp, err := c.ic.Do(req.WithContext(ctx))
 	if err != nil {
 		return nil, err
 	}
 	resp.Body.Close()
 
 	ao := &AddressObject{Path: path}
-	if err := populateAddressObject(ao, resp); err != nil {
+	if err := populateAddressObject(ao, resp.Header); err != nil {
 		return nil, err
 	}
 	return ao, nil
 }
+
+// SyncCollection performs a collection synchronization operation on the
+// specified resource, as defined in RFC 6578.
+func (c *Client) SyncCollection(ctx context.Context, path string, query *SyncQuery) (*SyncResponse, error) {
+	var limit *internal.Limit
+	if query.Limit > 0 {
+		limit = &internal.Limit{NResults: uint(query.Limit)}
+	}
+
+	propReq, err := encodeAddressPropReq(&query.DataRequest)
+	if err != nil {
+		return nil, err
+	}
+
+	ms, err := c.ic.SyncCollection(ctx, path, query.SyncToken, internal.DepthOne, limit, propReq)
+	if err != nil {
+		return nil, err
+	}
+
+	ret := &SyncResponse{SyncToken: ms.SyncToken}
+	for _, resp := range ms.Responses {
+		p, err := resp.Path()
+		if err != nil {
+			if err, ok := err.(*internal.HTTPError); ok && err.Code == http.StatusNotFound {
+				ret.Deleted = append(ret.Deleted, p)
+				continue
+			}
+			return nil, err
+		}
+
+		if p == path || path == fmt.Sprintf("%s/", p) {
+			continue
+		}
+
+		var getLastMod internal.GetLastModified
+		if err := resp.DecodeProp(&getLastMod); err != nil && !internal.IsNotFound(err) {
+			return nil, err
+		}
+
+		var getETag internal.GetETag
+		if err := resp.DecodeProp(&getETag); err != nil && !internal.IsNotFound(err) {
+			return nil, err
+		}
+
+		o := AddressObject{
+			Path:    p,
+			ModTime: time.Time(getLastMod.LastModified),
+			ETag:    string(getETag.ETag),
+		}
+		ret.Updated = append(ret.Updated, o)
+	}
+
+	return ret, nil
+}

carddav/elements.go

@@ -29,6 +29,10 @@ type addressbookHomeSet struct {
 	Href    internal.Href `xml:"DAV: href"`
 }
 
+func (a *addressbookHomeSet) GetXMLName() xml.Name {
+	return addressBookHomeSetName
+}
+
 type addressbookDescription struct {
 	XMLName     xml.Name `xml:"urn:ietf:params:xml:ns:carddav addressbook-description"`
 	Description string   `xml:",chardata"`
@@ -207,3 +211,11 @@ func (r *reportReq) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
 
 	return d.DecodeElement(v, &start)
 }
+
+type mkcolReq struct {
+	XMLName      xml.Name               `xml:"DAV: mkcol"`
+	ResourceType internal.ResourceType  `xml:"set>prop>resourcetype"`
+	DisplayName  string                 `xml:"set>prop>displayname"`
+	Description  addressbookDescription `xml:"set>prop>addressbook-description"`
+	// TODO this could theoretically contain all addressbook properties?
+}

carddav/match.go

@@ -0,0 +1,172 @@
+package carddav
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/emersion/go-vcard"
+)
+
+func filterProperties(req AddressDataRequest, ao AddressObject) AddressObject {
+	if req.AllProp || len(req.Props) == 0 {
+		return ao
+	}
+
+	if len(ao.Card) == 0 {
+		panic("request to process empty vCard")
+	}
+
+	result := AddressObject{
+		Path:    ao.Path,
+		ModTime: ao.ModTime,
+		ETag:    ao.ETag,
+	}
+
+	result.Card = make(vcard.Card)
+	// result would be invalid w/o version
+	result.Card[vcard.FieldVersion] = ao.Card[vcard.FieldVersion]
+	for _, prop := range req.Props {
+		value, ok := ao.Card[prop]
+		if ok {
+			result.Card[prop] = value
+		}
+	}
+
+	return result
+}
+
+// Filter returns the filtered list of address objects matching the provided query.
+// A nil query will return the full list of address objects.
+func Filter(query *AddressBookQuery, aos []AddressObject) ([]AddressObject, error) {
+	if query == nil {
+		// FIXME: should we always return a copy of the provided slice?
+		return aos, nil
+	}
+
+	n := query.Limit
+	if n <= 0 || n > len(aos) {
+		n = len(aos)
+	}
+	out := make([]AddressObject, 0, n)
+	for _, ao := range aos {
+		ok, err := Match(query, &ao)
+		if err != nil {
+			return nil, err
+		}
+		if !ok {
+			continue
+		}
+
+		out = append(out, filterProperties(query.DataRequest, ao))
+		if len(out) >= n {
+			break
+		}
+	}
+	return out, nil
+}
+
+// Match reports whether the provided AddressObject matches the query.
+func Match(query *AddressBookQuery, ao *AddressObject) (matched bool, err error) {
+	if query == nil {
+		return true, nil
+	}
+
+	switch query.FilterTest {
+	default:
+		return false, fmt.Errorf("unknown query filter test %q", query.FilterTest)
+
+	case FilterAnyOf, "":
+		for _, prop := range query.PropFilters {
+			ok, err := matchPropFilter(prop, ao)
+			if err != nil {
+				return false, err
+			}
+			if ok {
+				return true, nil
+			}
+		}
+		return false, nil
+
+	case FilterAllOf:
+		for _, prop := range query.PropFilters {
+			ok, err := matchPropFilter(prop, ao)
+			if err != nil {
+				return false, err
+			}
+			if !ok {
+				return false, nil
+			}
+		}
+		return true, nil
+	}
+}
+
+func matchPropFilter(prop PropFilter, ao *AddressObject) (bool, error) {
+	// TODO: this only matches first field, there could be multiple
+	field := ao.Card.Get(prop.Name)
+	if field == nil {
+		return prop.IsNotDefined, nil
+	} else if prop.IsNotDefined {
+		return false, nil
+	}
+
+	// TODO: handle carddav.PropFilter.Params.
+	if len(prop.TextMatches) == 0 {
+		return true, nil
+	}
+
+	switch prop.Test {
+	default:
+		return false, fmt.Errorf("unknown property filter test %q", prop.Test)
+
+	case FilterAnyOf, "":
+		for _, txt := range prop.TextMatches {
+			ok, err := matchTextMatch(txt, field)
+			if err != nil {
+				return false, err
+			}
+			if ok {
+				return true, nil
+			}
+		}
+		return false, nil
+
+	case FilterAllOf:
+		for _, txt := range prop.TextMatches {
+			ok, err := matchTextMatch(txt, field)
+			if err != nil {
+				return false, err
+			}
+			if !ok {
+				return false, nil
+			}
+		}
+		return true, nil
+	}
+}
+
+func matchTextMatch(txt TextMatch, field *vcard.Field) (bool, error) {
+	// TODO: handle text-match collation attribute
+	var ok bool
+	switch txt.MatchType {
+	default:
+		return false, fmt.Errorf("unknown textmatch type %q", txt.MatchType)
+
+	case MatchEquals:
+		ok = txt.Text == field.Value
+
+	case MatchContains, "":
+		ok = strings.Contains(field.Value, txt.Text)
+
+	case MatchStartsWith:
+		ok = strings.HasPrefix(field.Value, txt.Text)
+
+	case MatchEndsWith:
+		ok = strings.HasSuffix(field.Value, txt.Text)
+	}
+
+	if txt.NegateCondition {
+		ok = !ok
+	}
+	return ok, nil
+}

carddav/match_test.go

@@ -0,0 +1,633 @@
+package carddav
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/emersion/go-vcard"
+)
+
+func TestFilter(t *testing.T) {
+	newAO := func(str string) AddressObject {
+		card, err := vcard.NewDecoder(strings.NewReader(str)).Decode()
+		if err != nil {
+			t.Fatal(err)
+		}
+		return AddressObject{
+			Card: card,
+		}
+	}
+
+	alice := newAO(`BEGIN:VCARD
+VERSION:4.0
+UID:urn:uuid:4fbe8971-0bc3-424c-9c26-36c3e1eff6b1
+FN;PID=1.1:Alice Gopher
+N:Gopher;Alice;;;
+EMAIL;PID=1.1:alice@example.com
+CLIENTPIDMAP:1;urn:uuid:53e374d9-337e-4727-8803-a1e9c14e0551
+END:VCARD`)
+
+	bob := newAO(`BEGIN:VCARD
+VERSION:4.0
+UID:urn:uuid:4fbe8971-0bc3-424c-9c26-36c3e1eff6b2
+FN;PID=1.1:Bob Gopher
+N:Gopher;Bob;;;
+EMAIL;PID=1.1:bob@example.com
+CLIENTPIDMAP:1;urn:uuid:53e374d9-337e-4727-8803-a1e9c14e0552
+END:VCARD`)
+
+	carla := newAO(`BEGIN:VCARD
+VERSION:4.0
+UID:urn:uuid:4fbe8971-0bc3-424c-9c26-36c3e1eff6b3
+FN;PID=1.1:Carla Gopher
+N:Gopher;Carla;;;
+EMAIL;PID=1.1:carla@example.com
+CLIENTPIDMAP:1;urn:uuid:53e374d9-337e-4727-8803-a1e9c14e0553
+END:VCARD`)
+	carlaFiltered := newAO(`BEGIN:VCARD
+VERSION:4.0
+UID:urn:uuid:4fbe8971-0bc3-424c-9c26-36c3e1eff6b3
+EMAIL;PID=1.1:carla@example.com
+END:VCARD`)
+
+	for _, tc := range []struct {
+		name  string
+		query *AddressBookQuery
+		addrs []AddressObject
+		want  []AddressObject
+		err   error
+	}{
+		{
+			name:  "nil-query",
+			query: nil,
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{alice, bob, carla},
+		},
+		{
+			name: "no-limit-query",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					AllProp: true,
+				},
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "example.com"}},
+					},
+				},
+			},
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{alice, bob, carla},
+		},
+		{
+			name: "limit-1-query",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					AllProp: true,
+				},
+				Limit: 1,
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "example.com"}},
+					},
+				},
+			},
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{alice},
+		},
+		{
+			name: "limit-4-query",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					AllProp: true,
+				},
+				Limit: 4,
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "example.com"}},
+					},
+				},
+			},
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{alice, bob, carla},
+		},
+		{
+			name: "email-match",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					AllProp: true,
+				},
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "carla"}},
+					},
+				},
+			},
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{carla},
+		},
+		{
+			name: "email-match-any",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					AllProp: true,
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldEmail,
+						TextMatches: []TextMatch{
+							{Text: "carla@example"},
+							{Text: "alice@example"},
+						},
+					},
+				},
+			},
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{alice, carla},
+		},
+		{
+			name: "email-match-all",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					AllProp: true,
+				},
+				PropFilters: []PropFilter{{
+					Name: vcard.FieldEmail,
+					TextMatches: []TextMatch{
+						{Text: ""},
+					},
+				}},
+			},
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{alice, bob, carla},
+		},
+		{
+			name: "email-no-match",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					AllProp: true,
+				},
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "example.org"}},
+					},
+				},
+			},
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{},
+		},
+		{
+			name: "email-match-filter-properties",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldVersion,
+						vcard.FieldUID,
+						vcard.FieldEmail,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "carla"}},
+					},
+				},
+			},
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{carlaFiltered},
+		},
+		{
+			name: "email-match-filter-properties-always-returns-version",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldUID,
+						vcard.FieldEmail,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "carla"}},
+					},
+				},
+			},
+			addrs: []AddressObject{alice, bob, carla},
+			want:  []AddressObject{carlaFiltered},
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := Filter(tc.query, tc.addrs)
+			switch {
+			case err != nil && tc.err == nil:
+				t.Fatalf("unexpected error: %+v", err)
+			case err != nil && tc.err != nil:
+				if got, want := err.Error(), tc.err.Error(); got != want {
+					t.Fatalf("invalid error:\ngot= %q\nwant=%q", got, want)
+				}
+			case err == nil && tc.err != nil:
+				t.Fatalf("expected an error:\ngot= %+v\nwant=%+v", err, tc.err)
+			case err == nil && tc.err == nil:
+				if got, want := got, tc.want; !reflect.DeepEqual(got, want) {
+					t.Fatalf("invalid filter values:\ngot= %+v\nwant=%+v", got, want)
+				}
+			}
+		})
+	}
+}
+
+func TestMatch(t *testing.T) {
+	newAO := func(str string) AddressObject {
+		card, err := vcard.NewDecoder(strings.NewReader(str)).Decode()
+		if err != nil {
+			t.Fatal(err)
+		}
+		return AddressObject{
+			Card: card,
+		}
+	}
+
+	alice := newAO(`BEGIN:VCARD
+VERSION:4.0
+UID:urn:uuid:4fbe8971-0bc3-424c-9c26-36c3e1eff6b1
+FN;PID=1.1:Alice Gopher
+N:Gopher;Alice;;;
+EMAIL;PID=1.1:alice@example.com
+CLIENTPIDMAP:1;urn:uuid:53e374d9-337e-4727-8803-a1e9c14e0556
+END:VCARD`)
+
+	for _, tc := range []struct {
+		name  string
+		query *AddressBookQuery
+		addr  AddressObject
+		want  bool
+		err   error
+	}{
+		{
+			name:  "nil-query",
+			query: nil,
+			addr:  alice,
+			want:  true,
+		},
+		{
+			name: "match-email-contains",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "example.com"}},
+					},
+				},
+			},
+			addr: alice,
+			want: true,
+		},
+		{
+			name: "match-email-equals-ok",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldEmail,
+						TextMatches: []TextMatch{{
+							Text:      "alice@example.com",
+							MatchType: MatchEquals,
+						}},
+					},
+				},
+			},
+			addr: alice,
+			want: true,
+		},
+		{
+			name: "match-email-equals-not",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldEmail,
+						TextMatches: []TextMatch{{
+							Text:      "example.com",
+							MatchType: MatchEquals,
+						}},
+					},
+				},
+			},
+			addr: alice,
+			want: false,
+		},
+		{
+			name: "match-email-equals-ok-negate",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldEmail,
+						TextMatches: []TextMatch{{
+							Text:            "bob@example.com",
+							NegateCondition: true,
+							MatchType:       MatchEquals,
+						}},
+					},
+				},
+			},
+			addr: alice,
+			want: true,
+		},
+		{
+			name: "match-email-starts-with-ok",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldEmail,
+						TextMatches: []TextMatch{{
+							Text:      "alice@",
+							MatchType: MatchStartsWith,
+						}},
+					},
+				},
+			},
+			addr: alice,
+			want: true,
+		},
+		{
+			name: "match-email-ends-with-ok",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldEmail,
+						TextMatches: []TextMatch{{
+							Text:      "com",
+							MatchType: MatchEndsWith,
+						}},
+					},
+				},
+			},
+			addr: alice,
+			want: true,
+		},
+		{
+			name: "match-email-ends-with-not",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldEmail,
+						TextMatches: []TextMatch{{
+							Text:      ".org",
+							MatchType: MatchEndsWith,
+						}},
+					},
+				},
+			},
+			addr: alice,
+			want: false,
+		},
+		{
+			name: "match-name-contains-ok",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldName,
+						TextMatches: []TextMatch{{
+							Text:      "Alice",
+							MatchType: MatchContains,
+						}},
+					},
+				},
+			},
+			addr: alice,
+			want: true,
+		},
+		{
+			name: "match-name-contains-all-ok",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldName,
+						Test: FilterAllOf,
+						TextMatches: []TextMatch{
+							{
+								Text:      "Alice",
+								MatchType: MatchContains,
+							},
+							{
+								Text:      "Gopher",
+								MatchType: MatchContains,
+							},
+						},
+					},
+				},
+			},
+			addr: alice,
+			want: true,
+		},
+		{
+			name: "match-name-contains-all-prop-not",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				FilterTest: FilterAllOf,
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldName,
+						TextMatches: []TextMatch{{
+							Text:      "Alice",
+							MatchType: MatchContains,
+						}},
+					},
+					{
+						Name: vcard.FieldName,
+						TextMatches: []TextMatch{{
+							Text:      "GopherXXX",
+							MatchType: MatchContains,
+						}},
+					},
+				},
+			},
+			addr: alice,
+			want: false,
+		},
+		{
+			name: "match-name-contains-all-text-match-not",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name: vcard.FieldName,
+						Test: FilterAllOf,
+						TextMatches: []TextMatch{
+							{
+								Text:      "Alice",
+								MatchType: MatchContains,
+							},
+							{
+								Text:      "GopherXXX",
+								MatchType: MatchContains,
+							},
+						},
+					},
+				},
+			},
+			addr: alice,
+			want: false,
+		},
+		{
+			name: "missing-prop-ok",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+						"XXX-not-THERE", // but AllProp is false.
+					},
+				},
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "example.com"}},
+					},
+				},
+			},
+			addr: alice,
+			want: true,
+		},
+		{
+			name: "match-all-prop-ok",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+					AllProp: true,
+				},
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "example.com"}},
+					},
+				},
+			},
+			addr: alice,
+			want: true,
+		},
+		{
+			name: "invalid-query-filter",
+			query: &AddressBookQuery{
+				DataRequest: AddressDataRequest{
+					Props: []string{
+						vcard.FieldFormattedName,
+						vcard.FieldEmail,
+						vcard.FieldUID,
+					},
+				},
+				FilterTest: "XXX-invalid-filter",
+				PropFilters: []PropFilter{
+					{
+						Name:        vcard.FieldEmail,
+						TextMatches: []TextMatch{{Text: "example.com"}},
+					},
+				},
+			},
+			addr: alice,
+			err:  fmt.Errorf("unknown query filter test \"XXX-invalid-filter\""),
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := Match(tc.query, &tc.addr)
+			switch {
+			case err != nil && tc.err == nil:
+				t.Fatalf("unexpected error: %+v", err)
+			case err != nil && tc.err != nil:
+				if got, want := err.Error(), tc.err.Error(); got != want {
+					t.Fatalf("invalid error:\ngot= %q\nwant=%q", got, want)
+				}
+			case err == nil && tc.err != nil:
+				t.Fatalf("expected an error:\ngot= %+v\nwant=%+v", err, tc.err)
+			case err == nil && tc.err == nil:
+				if got, want := got, tc.want; got != want {
+					t.Fatalf("invalid match value: got=%v, want=%v", got, want)
+				}
+			}
+		})
+	}
+}

carddav/server.go

@@ -2,31 +2,50 @@ package carddav
 
 import (
 	"bytes"
+	"context"
 	"encoding/xml"
 	"fmt"
 	"mime"
 	"net/http"
+	"path"
+	"strconv"
+	"strings"
 
 	"github.com/emersion/go-vcard"
+	"github.com/emersion/go-webdav"
 	"github.com/emersion/go-webdav/internal"
 )
 
-// TODO: add support for multiple address books
+type PutAddressObjectOptions struct {
+	// IfNoneMatch indicates that the client does not want to overwrite
+	// an existing resource.
+	IfNoneMatch webdav.ConditionalMatch
+	// IfMatch provides the ETag of the resource that the client intends
+	// to overwrite, can be ""
+	IfMatch webdav.ConditionalMatch
+}
 
 // Backend is a CardDAV server backend.
 type Backend interface {
-	AddressBook() (*AddressBook, error)
-	GetAddressObject(path string, req *AddressDataRequest) (*AddressObject, error)
-	ListAddressObjects(req *AddressDataRequest) ([]AddressObject, error)
-	QueryAddressObjects(query *AddressBookQuery) ([]AddressObject, error)
-	PutAddressObject(path string, card vcard.Card) (loc string, err error)
-	DeleteAddressObject(path string) error
+	AddressBookHomeSetPath(ctx context.Context) (string, error)
+	ListAddressBooks(ctx context.Context) ([]AddressBook, error)
+	GetAddressBook(ctx context.Context, path string) (*AddressBook, error)
+	CreateAddressBook(ctx context.Context, addressBook *AddressBook) error
+	DeleteAddressBook(ctx context.Context, path string) error
+	GetAddressObject(ctx context.Context, path string, req *AddressDataRequest) (*AddressObject, error)
+	ListAddressObjects(ctx context.Context, path string, req *AddressDataRequest) ([]AddressObject, error)
+	QueryAddressObjects(ctx context.Context, path string, query *AddressBookQuery) ([]AddressObject, error)
+	PutAddressObject(ctx context.Context, path string, card vcard.Card, opts *PutAddressObjectOptions) (*AddressObject, error)
+	DeleteAddressObject(ctx context.Context, path string) error
+
+	webdav.UserPrincipalBackend
 }
 
 // Handler handles CardDAV HTTP requests. It can be used to create a CardDAV
 // server.
 type Handler struct {
 	Backend Backend
+	Prefix  string
 }
 
 // ServeHTTP implements http.Handler.
@@ -36,13 +55,27 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if r.URL.Path == "/.well-known/carddav" {
+		principalPath, err := h.Backend.CurrentUserPrincipal(r.Context())
+		if err != nil {
+			http.Error(w, "carddav: failed to determine current user principal", http.StatusInternalServerError)
+			return
+		}
+
+		http.Redirect(w, r, principalPath, http.StatusPermanentRedirect)
+		return
+	}
+
 	var err error
 	switch r.Method {
 	case "REPORT":
 		err = h.handleReport(w, r)
 	default:
-		b := backend{h.Backend}
-		hh := internal.Handler{&b}
+		b := backend{
+			Backend: h.Backend,
+			Prefix:  strings.TrimSuffix(h.Prefix, "/"),
+		}
+		hh := internal.Handler{Backend: &b}
 		hh.ServeHTTP(w, r)
 	}
 
@@ -58,9 +91,9 @@ func (h *Handler) handleReport(w http.ResponseWriter, r *http.Request) error {
 	}
 
 	if report.Query != nil {
-		return h.handleQuery(w, report.Query)
+		return h.handleQuery(r, w, report.Query)
 	} else if report.Multiget != nil {
-		return h.handleMultiget(w, report.Multiget)
+		return h.handleMultiget(r.Context(), w, report.Multiget)
 	}
 	return internal.HTTPErrorf(http.StatusBadRequest, "carddav: expected addressbook-query or addressbook-multiget element in REPORT request")
 }
@@ -120,7 +153,7 @@ func decodeAddressDataReq(addressData *addressDataReq) (*AddressDataRequest, err
 	return req, nil
 }
 
-func (h *Handler) handleQuery(w http.ResponseWriter, query *addressbookQuery) error {
+func (h *Handler) handleQuery(r *http.Request, w http.ResponseWriter, query *addressbookQuery) error {
 	var q AddressBookQuery
 	if query.Prop != nil {
 		var addressData addressDataReq
@@ -137,42 +170,45 @@ func (h *Handler) handleQuery(w http.ResponseWriter, query *addressbookQuery) er
 	for _, el := range query.Filter.Props {
 		pf, err := decodePropFilter(&el)
 		if err != nil {
-			return &internal.HTTPError{http.StatusBadRequest, err}
+			return &internal.HTTPError{Code: http.StatusBadRequest, Err: err}
 		}
 		q.PropFilters = append(q.PropFilters, *pf)
 	}
 	if query.Limit != nil {
 		q.Limit = int(query.Limit.NResults)
 		if q.Limit <= 0 {
-			return internal.ServeMultistatus(w, internal.NewMultistatus())
+			return internal.ServeMultiStatus(w, internal.NewMultiStatus())
 		}
 	}
 
-	aos, err := h.Backend.QueryAddressObjects(&q)
+	aos, err := h.Backend.QueryAddressObjects(r.Context(), r.URL.Path, &q)
 	if err != nil {
 		return err
 	}
 
 	var resps []internal.Response
 	for _, ao := range aos {
-		b := backend{h.Backend}
-		propfind := internal.Propfind{
+		b := backend{
+			Backend: h.Backend,
+			Prefix:  strings.TrimSuffix(h.Prefix, "/"),
+		}
+		propfind := internal.PropFind{
 			Prop:     query.Prop,
 			AllProp:  query.AllProp,
 			PropName: query.PropName,
 		}
-		resp, err := b.propfindAddressObject(&propfind, &ao)
+		resp, err := b.propFindAddressObject(r.Context(), &propfind, &ao)
 		if err != nil {
 			return err
 		}
 		resps = append(resps, *resp)
 	}
 
-	ms := internal.NewMultistatus(resps...)
-	return internal.ServeMultistatus(w, ms)
+	ms := internal.NewMultiStatus(resps...)
+	return internal.ServeMultiStatus(w, ms)
 }
 
-func (h *Handler) handleMultiget(w http.ResponseWriter, multiget *addressbookMultiget) error {
+func (h *Handler) handleMultiget(ctx context.Context, w http.ResponseWriter, multiget *addressbookMultiget) error {
 	var dataReq AddressDataRequest
 	if multiget.Prop != nil {
 		var addressData addressDataReq
@@ -188,43 +224,71 @@ func (h *Handler) handleMultiget(w http.ResponseWriter, multiget *addressbookMul
 
 	var resps []internal.Response
 	for _, href := range multiget.Hrefs {
-		ao, err := h.Backend.GetAddressObject(href.Path, &dataReq)
+		ao, err := h.Backend.GetAddressObject(ctx, href.Path, &dataReq)
 		if err != nil {
-			return err // TODO: create internal.Response with error
+			resp := internal.NewErrorResponse(href.Path, err)
+			resps = append(resps, *resp)
+			continue
 		}
 
-		b := backend{h.Backend}
-		propfind := internal.Propfind{
+		b := backend{
+			Backend: h.Backend,
+			Prefix:  strings.TrimSuffix(h.Prefix, "/"),
+		}
+		propfind := internal.PropFind{
 			Prop:     multiget.Prop,
 			AllProp:  multiget.AllProp,
 			PropName: multiget.PropName,
 		}
-		resp, err := b.propfindAddressObject(&propfind, ao)
+		resp, err := b.propFindAddressObject(ctx, &propfind, ao)
 		if err != nil {
 			return err
 		}
 		resps = append(resps, *resp)
 	}
 
-	ms := internal.NewMultistatus(resps...)
-	return internal.ServeMultistatus(w, ms)
+	ms := internal.NewMultiStatus(resps...)
+	return internal.ServeMultiStatus(w, ms)
 }
 
 type backend struct {
 	Backend Backend
+	Prefix  string
+}
+
+type resourceType int
+
+const (
+	resourceTypeRoot resourceType = iota
+	resourceTypeUserPrincipal
+	resourceTypeAddressBookHomeSet
+	resourceTypeAddressBook
+	resourceTypeAddressObject
+)
+
+func (b *backend) resourceTypeAtPath(reqPath string) resourceType {
+	p := path.Clean(reqPath)
+	p = strings.TrimPrefix(p, b.Prefix)
+	if !strings.HasPrefix(p, "/") {
+		p = "/" + p
+	}
+	if p == "/" {
+		return resourceTypeRoot
+	}
+	return resourceType(len(strings.Split(p, "/")) - 1)
 }
 
 func (b *backend) Options(r *http.Request) (caps []string, allow []string, err error) {
 	caps = []string{"addressbook"}
 
-	if r.URL.Path == "/" {
+	if b.resourceTypeAtPath(r.URL.Path) != resourceTypeAddressObject {
 		// Note: some clients assume the address book is read-only when
 		// DELETE/MKCOL are missing
 		return caps, []string{http.MethodOptions, "PROPFIND", "REPORT", "DELETE", "MKCOL"}, nil
 	}
 
 	var dataReq AddressDataRequest
-	_, err = b.Backend.GetAddressObject(r.URL.Path, &dataReq)
+	_, err = b.Backend.GetAddressObject(r.Context(), r.URL.Path, &dataReq)
 	if httpErr, ok := err.(*internal.HTTPError); ok && httpErr.Code == http.StatusNotFound {
 		return caps, []string{http.MethodOptions, http.MethodPut}, nil
 	} else if err != nil {
@@ -242,21 +306,25 @@ func (b *backend) Options(r *http.Request) (caps []string, allow []string, err e
 }
 
 func (b *backend) HeadGet(w http.ResponseWriter, r *http.Request) error {
-	if r.URL.Path == "/" {
-		return &internal.HTTPError{Code: http.StatusMethodNotAllowed}
-	}
-
 	var dataReq AddressDataRequest
 	if r.Method != http.MethodHead {
 		dataReq.AllProp = true
 	}
-	ao, err := b.Backend.GetAddressObject(r.URL.Path, &dataReq)
+	ao, err := b.Backend.GetAddressObject(r.Context(), r.URL.Path, &dataReq)
 	if err != nil {
 		return err
 	}
 
 	w.Header().Set("Content-Type", vcard.MIMEType)
-	// TODO: set ETag, Last-Modified
+	if ao.ContentLength > 0 {
+		w.Header().Set("Content-Length", strconv.FormatInt(ao.ContentLength, 10))
+	}
+	if ao.ETag != "" {
+		w.Header().Set("ETag", internal.ETag(ao.ETag).String())
+	}
+	if !ao.ModTime.IsZero() {
+		w.Header().Set("Last-Modified", ao.ModTime.UTC().Format(http.TimeFormat))
+	}
 
 	if r.Method != http.MethodHead {
 		return vcard.NewEncoder(w).Encode(ao.Card)
@@ -264,95 +332,231 @@ func (b *backend) HeadGet(w http.ResponseWriter, r *http.Request) error {
 	return nil
 }
 
-func (b *backend) Propfind(r *http.Request, propfind *internal.Propfind, depth internal.Depth) (*internal.Multistatus, error) {
+func (b *backend) PropFind(r *http.Request, propfind *internal.PropFind, depth internal.Depth) (*internal.MultiStatus, error) {
+	resType := b.resourceTypeAtPath(r.URL.Path)
+
 	var dataReq AddressDataRequest
-
 	var resps []internal.Response
-	if r.URL.Path == "/" {
-		ab, err := b.Backend.AddressBook()
-		if err != nil {
-			return nil, err
-		}
 
-		resp, err := b.propfindAddressBook(propfind, ab)
+	switch resType {
+	case resourceTypeRoot:
+		resp, err := b.propFindRoot(r.Context(), propfind)
 		if err != nil {
 			return nil, err
 		}
 		resps = append(resps, *resp)
-
-		if depth != internal.DepthZero {
-			aos, err := b.Backend.ListAddressObjects(&dataReq)
+	case resourceTypeUserPrincipal:
+		principalPath, err := b.Backend.CurrentUserPrincipal(r.Context())
+		if err != nil {
+			return nil, err
+		}
+		if r.URL.Path == principalPath {
+			resp, err := b.propFindUserPrincipal(r.Context(), propfind)
 			if err != nil {
 				return nil, err
 			}
-
-			for _, ao := range aos {
-				resp, err := b.propfindAddressObject(propfind, &ao)
+			resps = append(resps, *resp)
+			if depth != internal.DepthZero {
+				resp, err := b.propFindHomeSet(r.Context(), propfind)
 				if err != nil {
 					return nil, err
 				}
 				resps = append(resps, *resp)
+				if depth == internal.DepthInfinity {
+					resps_, err := b.propFindAllAddressBooks(r.Context(), propfind, true)
+					if err != nil {
+						return nil, err
+					}
+					resps = append(resps, resps_...)
+				}
 			}
 		}
-	} else {
-		ao, err := b.Backend.GetAddressObject(r.URL.Path, &dataReq)
+	case resourceTypeAddressBookHomeSet:
+		homeSetPath, err := b.Backend.AddressBookHomeSetPath(r.Context())
+		if err != nil {
+			return nil, err
+		}
+		if r.URL.Path == homeSetPath {
+			resp, err := b.propFindHomeSet(r.Context(), propfind)
+			if err != nil {
+				return nil, err
+			}
+			resps = append(resps, *resp)
+			if depth != internal.DepthZero {
+				recurse := depth == internal.DepthInfinity
+				resps_, err := b.propFindAllAddressBooks(r.Context(), propfind, recurse)
+				if err != nil {
+					return nil, err
+				}
+				resps = append(resps, resps_...)
+			}
+		}
+	case resourceTypeAddressBook:
+		ab, err := b.Backend.GetAddressBook(r.Context(), r.URL.Path)
+		if err != nil {
+			return nil, err
+		}
+		resp, err := b.propFindAddressBook(r.Context(), propfind, ab)
+		if err != nil {
+			return nil, err
+		}
+		resps = append(resps, *resp)
+		if depth != internal.DepthZero {
+			resps_, err := b.propFindAllAddressObjects(r.Context(), propfind, ab)
+			if err != nil {
+				return nil, err
+			}
+			resps = append(resps, resps_...)
+		}
+	case resourceTypeAddressObject:
+		ao, err := b.Backend.GetAddressObject(r.Context(), r.URL.Path, &dataReq)
 		if err != nil {
 			return nil, err
 		}
 
-		resp, err := b.propfindAddressObject(propfind, ao)
+		resp, err := b.propFindAddressObject(r.Context(), propfind, ao)
 		if err != nil {
 			return nil, err
 		}
 		resps = append(resps, *resp)
 	}
 
-	return internal.NewMultistatus(resps...), nil
+	return internal.NewMultiStatus(resps...), nil
 }
 
-func (b *backend) propfindAddressBook(propfind *internal.Propfind, ab *AddressBook) (*internal.Response, error) {
-	props := map[xml.Name]internal.PropfindFunc{
-		internal.ResourceTypeName: func(*internal.RawXMLValue) (interface{}, error) {
-			return internal.NewResourceType(internal.CollectionName, addressBookName), nil
-		},
-		internal.DisplayNameName: func(*internal.RawXMLValue) (interface{}, error) {
-			return &internal.DisplayName{Name: ab.Name}, nil
-		},
-		addressBookDescriptionName: func(*internal.RawXMLValue) (interface{}, error) {
-			return &addressbookDescription{Description: ab.Description}, nil
-		},
-		supportedAddressDataName: func(*internal.RawXMLValue) (interface{}, error) {
-			return &supportedAddressData{
-				Types: []addressDataType{
-					{ContentType: vcard.MIMEType, Version: "3.0"},
-					{ContentType: vcard.MIMEType, Version: "4.0"},
-				},
-			}, nil
-		},
-		// TODO: this is a principal property
-		addressBookHomeSetName: func(*internal.RawXMLValue) (interface{}, error) {
-			return &addressbookHomeSet{Href: internal.Href{Path: "/"}}, nil
-		},
-		// TODO: this should be set on all resources
-		internal.CurrentUserPrincipalName: func(*internal.RawXMLValue) (interface{}, error) {
-			return &internal.CurrentUserPrincipal{Href: internal.Href{Path: "/"}}, nil
-		},
+func (b *backend) propFindRoot(ctx context.Context, propfind *internal.PropFind) (*internal.Response, error) {
+	principalPath, err := b.Backend.CurrentUserPrincipal(ctx)
+	if err != nil {
+		return nil, err
 	}
 
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: internal.PropFindValue(&internal.CurrentUserPrincipal{
+			Href: internal.Href{Path: principalPath},
+		}),
+		internal.ResourceTypeName: internal.PropFindValue(internal.NewResourceType(internal.CollectionName)),
+	}
+	return internal.NewPropFindResponse(principalPath, propfind, props)
+}
+
+func (b *backend) propFindUserPrincipal(ctx context.Context, propfind *internal.PropFind) (*internal.Response, error) {
+	principalPath, err := b.Backend.CurrentUserPrincipal(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: internal.PropFindValue(&internal.CurrentUserPrincipal{
+			Href: internal.Href{Path: principalPath},
+		}),
+		addressBookHomeSetName: func(*internal.RawXMLValue) (interface{}, error) {
+			homeSetPath, err := b.Backend.AddressBookHomeSetPath(ctx)
+			if err != nil {
+				return nil, err
+			}
+			return &addressbookHomeSet{Href: internal.Href{Path: homeSetPath}}, nil
+		},
+		internal.ResourceTypeName: internal.PropFindValue(internal.NewResourceType(internal.CollectionName)),
+	}
+	return internal.NewPropFindResponse(principalPath, propfind, props)
+}
+
+func (b *backend) propFindHomeSet(ctx context.Context, propfind *internal.PropFind) (*internal.Response, error) {
+	homeSetPath, err := b.Backend.AddressBookHomeSetPath(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	// TODO anything else to return here?
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: func(*internal.RawXMLValue) (interface{}, error) {
+			principalPath, err := b.Backend.CurrentUserPrincipal(ctx)
+			if err != nil {
+				return nil, err
+			}
+			return &internal.CurrentUserPrincipal{Href: internal.Href{Path: principalPath}}, nil
+		},
+		internal.ResourceTypeName: internal.PropFindValue(internal.NewResourceType(internal.CollectionName)),
+	}
+	return internal.NewPropFindResponse(homeSetPath, propfind, props)
+}
+
+func (b *backend) propFindAddressBook(ctx context.Context, propfind *internal.PropFind, ab *AddressBook) (*internal.Response, error) {
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: func(*internal.RawXMLValue) (interface{}, error) {
+			path, err := b.Backend.CurrentUserPrincipal(ctx)
+			if err != nil {
+				return nil, err
+			}
+			return &internal.CurrentUserPrincipal{Href: internal.Href{Path: path}}, nil
+		},
+		internal.ResourceTypeName: internal.PropFindValue(internal.NewResourceType(internal.CollectionName, addressBookName)),
+		supportedAddressDataName: internal.PropFindValue(&supportedAddressData{
+			Types: []addressDataType{
+				{ContentType: vcard.MIMEType, Version: "3.0"},
+				{ContentType: vcard.MIMEType, Version: "4.0"},
+			},
+		}),
+	}
+
+	if ab.Name != "" {
+		props[internal.DisplayNameName] = internal.PropFindValue(&internal.DisplayName{
+			Name: ab.Name,
+		})
+	}
+	if ab.Description != "" {
+		props[addressBookDescriptionName] = internal.PropFindValue(&addressbookDescription{
+			Description: ab.Description,
+		})
+	}
 	if ab.MaxResourceSize > 0 {
-		props[maxResourceSizeName] = func(*internal.RawXMLValue) (interface{}, error) {
-			return &maxResourceSize{Size: ab.MaxResourceSize}, nil
+		props[maxResourceSizeName] = internal.PropFindValue(&maxResourceSize{
+			Size: ab.MaxResourceSize,
+		})
+	}
+	props[internal.CurrentUserPrivilegeSetName] = func(*internal.RawXMLValue) (interface{}, error) {
+		return &internal.CurrentUserPrivilegeSet{Privilege: internal.NewAllPrivileges()}, nil
+	}
+
+	return internal.NewPropFindResponse(ab.Path, propfind, props)
+}
+
+func (b *backend) propFindAllAddressBooks(ctx context.Context, propfind *internal.PropFind, recurse bool) ([]internal.Response, error) {
+	abs, err := b.Backend.ListAddressBooks(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	var resps []internal.Response
+	for _, ab := range abs {
+		resp, err := b.propFindAddressBook(ctx, propfind, &ab)
+		if err != nil {
+			return nil, err
+		}
+		resps = append(resps, *resp)
+		if recurse {
+			resps_, err := b.propFindAllAddressObjects(ctx, propfind, &ab)
+			if err != nil {
+				return nil, err
+			}
+			resps = append(resps, resps_...)
 		}
 	}
-
-	return internal.NewPropfindResponse("/", propfind, props)
+	return resps, nil
 }
 
-func (b *backend) propfindAddressObject(propfind *internal.Propfind, ao *AddressObject) (*internal.Response, error) {
-	props := map[xml.Name]internal.PropfindFunc{
-		internal.GetContentTypeName: func(*internal.RawXMLValue) (interface{}, error) {
-			return &internal.GetContentType{Type: vcard.MIMEType}, nil
+func (b *backend) propFindAddressObject(ctx context.Context, propfind *internal.PropFind, ao *AddressObject) (*internal.Response, error) {
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.CurrentUserPrincipalName: func(*internal.RawXMLValue) (interface{}, error) {
+			path, err := b.Backend.CurrentUserPrincipal(ctx)
+			if err != nil {
+				return nil, err
+			}
+			return &internal.CurrentUserPrincipal{Href: internal.Href{Path: path}}, nil
 		},
+		internal.GetContentTypeName: internal.PropFindValue(&internal.GetContentType{
+			Type: vcard.MIMEType,
+		}),
 		// TODO: address-data can only be used in REPORT requests
 		addressDataName: func(*internal.RawXMLValue) (interface{}, error) {
 			var buf bytes.Buffer
@@ -364,67 +568,191 @@ func (b *backend) propfindAddressObject(propfind *internal.Propfind, ao *Address
 		},
 	}
 
+	if ao.ContentLength > 0 {
+		props[internal.GetContentLengthName] = internal.PropFindValue(&internal.GetContentLength{
+			Length: ao.ContentLength,
+		})
+	}
 	if !ao.ModTime.IsZero() {
-		props[internal.GetLastModifiedName] = func(*internal.RawXMLValue) (interface{}, error) {
-			return &internal.GetLastModified{LastModified: internal.Time(ao.ModTime)}, nil
-		}
+		props[internal.GetLastModifiedName] = internal.PropFindValue(&internal.GetLastModified{
+			LastModified: internal.Time(ao.ModTime),
+		})
 	}
 
 	if ao.ETag != "" {
-		props[internal.GetETagName] = func(*internal.RawXMLValue) (interface{}, error) {
-			return &internal.GetETag{ETag: internal.ETag(ao.ETag)}, nil
+		props[internal.GetETagName] = internal.PropFindValue(&internal.GetETag{
+			ETag: internal.ETag(ao.ETag),
+		})
+	}
+
+	return internal.NewPropFindResponse(ao.Path, propfind, props)
+}
+
+func (b *backend) propFindAllAddressObjects(ctx context.Context, propfind *internal.PropFind, ab *AddressBook) ([]internal.Response, error) {
+	var dataReq AddressDataRequest
+	aos, err := b.Backend.ListAddressObjects(ctx, ab.Path, &dataReq)
+	if err != nil {
+		return nil, err
+	}
+
+	var resps []internal.Response
+	for _, ao := range aos {
+		resp, err := b.propFindAddressObject(ctx, propfind, &ao)
+		if err != nil {
+			return nil, err
+		}
+		resps = append(resps, *resp)
+	}
+	return resps, nil
+}
+
+func (b *backend) PropPatch(r *http.Request, update *internal.PropertyUpdate) (*internal.Response, error) {
+	homeSetPath, err := b.Backend.AddressBookHomeSetPath(r.Context())
+	if err != nil {
+		return nil, err
+	}
+
+	resp := internal.NewOKResponse(r.URL.Path)
+
+	if r.URL.Path == homeSetPath {
+		// TODO: support PROPPATCH for address books
+		for _, prop := range update.Remove {
+			emptyVal := internal.NewRawXMLElement(prop.Prop.XMLName, nil, nil)
+			if err := resp.EncodeProp(http.StatusNotImplemented, emptyVal); err != nil {
+				return nil, err
+			}
+		}
+		for _, prop := range update.Set {
+			emptyVal := internal.NewRawXMLElement(prop.Prop.XMLName, nil, nil)
+			if err := resp.EncodeProp(http.StatusNotImplemented, emptyVal); err != nil {
+				return nil, err
+			}
+		}
+	} else {
+		for _, prop := range update.Remove {
+			emptyVal := internal.NewRawXMLElement(prop.Prop.XMLName, nil, nil)
+			if err := resp.EncodeProp(http.StatusMethodNotAllowed, emptyVal); err != nil {
+				return nil, err
+			}
+		}
+		for _, prop := range update.Set {
+			emptyVal := internal.NewRawXMLElement(prop.Prop.XMLName, nil, nil)
+			if err := resp.EncodeProp(http.StatusMethodNotAllowed, emptyVal); err != nil {
+				return nil, err
+			}
 		}
 	}
 
-	return internal.NewPropfindResponse(ao.Path, propfind, props)
+	return resp, nil
 }
 
-func (b *backend) Proppatch(r *http.Request, update *internal.Propertyupdate) (*internal.Response, error) {
-	// TODO: return a failed Response instead
-	// TODO: support PROPPATCH for address books
-	return nil, internal.HTTPErrorf(http.StatusForbidden, "carddav: PROPPATCH is unsupported")
-}
+func (b *backend) Put(w http.ResponseWriter, r *http.Request) error {
+	ifNoneMatch := webdav.ConditionalMatch(r.Header.Get("If-None-Match"))
+	ifMatch := webdav.ConditionalMatch(r.Header.Get("If-Match"))
 
-func (b *backend) Put(r *http.Request) (*internal.Href, error) {
-	// TODO: add support for If-None-Match and If-Match
+	opts := PutAddressObjectOptions{
+		IfNoneMatch: ifNoneMatch,
+		IfMatch:     ifMatch,
+	}
 
 	t, _, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
 	if err != nil {
-		return nil, internal.HTTPErrorf(http.StatusBadRequest, "carddav: malformed Content-Type: %v", err)
+		return internal.HTTPErrorf(http.StatusBadRequest, "carddav: malformed Content-Type: %v", err)
 	}
 	if t != vcard.MIMEType {
 		// TODO: send CARDDAV:supported-address-data error
-		return nil, internal.HTTPErrorf(http.StatusBadRequest, "carddav: unsupporetd Content-Type %q", t)
+		return internal.HTTPErrorf(http.StatusBadRequest, "carddav: unsupporetd Content-Type %q", t)
 	}
 
 	// TODO: check CARDDAV:max-resource-size precondition
 	card, err := vcard.NewDecoder(r.Body).Decode()
 	if err != nil {
 		// TODO: send CARDDAV:valid-address-data error
-		return nil, internal.HTTPErrorf(http.StatusBadRequest, "carddav: failed to parse vCard: %v", err)
+		return internal.HTTPErrorf(http.StatusBadRequest, "carddav: failed to parse vCard: %v", err)
 	}
 
 	// TODO: add support for the CARDDAV:no-uid-conflict error
-	loc, err := b.Backend.PutAddressObject(r.URL.Path, card)
+	ao, err := b.Backend.PutAddressObject(r.Context(), r.URL.Path, card, &opts)
 	if err != nil {
-		return nil, err
+		return err
+	}
+	if ao.ETag != "" {
+		w.Header().Set("ETag", internal.ETag(ao.ETag).String())
+	}
+	if !ao.ModTime.IsZero() {
+		w.Header().Set("Last-Modified", ao.ModTime.UTC().Format(http.TimeFormat))
+	}
+	if ao.Path != "" {
+		w.Header().Set("Location", ao.Path)
 	}
 
-	return &internal.Href{Path: loc}, nil
+	// TODO: http.StatusNoContent if the resource already existed
+	w.WriteHeader(http.StatusCreated)
+
+	return nil
 }
 
 func (b *backend) Delete(r *http.Request) error {
-	return b.Backend.DeleteAddressObject(r.URL.Path)
+	switch b.resourceTypeAtPath(r.URL.Path) {
+	case resourceTypeAddressBook:
+		return b.Backend.DeleteAddressBook(r.Context(), r.URL.Path)
+	case resourceTypeAddressObject:
+		return b.Backend.DeleteAddressObject(r.Context(), r.URL.Path)
+	}
+	return internal.HTTPErrorf(http.StatusForbidden, "carddav: cannot delete resource at given location")
 }
 
 func (b *backend) Mkcol(r *http.Request) error {
-	return internal.HTTPErrorf(http.StatusForbidden, "carddav: address book creation unsupported")
+	if b.resourceTypeAtPath(r.URL.Path) != resourceTypeAddressBook {
+		return internal.HTTPErrorf(http.StatusForbidden, "carddav: address book creation not allowed at given location")
+	}
+
+	ab := AddressBook{
+		Path: r.URL.Path,
+	}
+
+	if !internal.IsRequestBodyEmpty(r) {
+		var m mkcolReq
+		if err := internal.DecodeXMLRequest(r, &m); err != nil {
+			return internal.HTTPErrorf(http.StatusBadRequest, "carddav: error parsing mkcol request: %s", err.Error())
+		}
+
+		if !m.ResourceType.Is(internal.CollectionName) || !m.ResourceType.Is(addressBookName) {
+			return internal.HTTPErrorf(http.StatusBadRequest, "carddav: unexpected resource type")
+		}
+		ab.Name = m.DisplayName
+		ab.Description = m.Description.Description
+		// TODO ...
+	}
+
+	return b.Backend.CreateAddressBook(r.Context(), &ab)
 }
 
 func (b *backend) Copy(r *http.Request, dest *internal.Href, recursive, overwrite bool) (created bool, err error) {
-	panic("TODO")
+	return false, internal.HTTPErrorf(http.StatusNotImplemented, "carddav: Copy not implemented")
 }
 
 func (b *backend) Move(r *http.Request, dest *internal.Href, overwrite bool) (created bool, err error) {
-	panic("TODO")
+	return false, internal.HTTPErrorf(http.StatusNotImplemented, "carddav: Move not implemented")
+}
+
+// PreconditionType as defined in https://tools.ietf.org/rfcmarkup?doc=6352#section-6.3.2.1
+type PreconditionType string
+
+const (
+	PreconditionNoUIDConflict        PreconditionType = "no-uid-conflict"
+	PreconditionSupportedAddressData PreconditionType = "supported-address-data"
+	PreconditionValidAddressData     PreconditionType = "valid-address-data"
+	PreconditionMaxResourceSize      PreconditionType = "max-resource-size"
+)
+
+func NewPreconditionError(err PreconditionType) error {
+	name := xml.Name{Space: "urn:ietf:params:xml:ns:carddav", Local: string(err)}
+	elem := internal.NewRawXMLElement(name, nil, nil)
+	return &internal.HTTPError{
+		Code: 409,
+		Err: &internal.Error{
+			Raw: []internal.RawXMLValue{*elem},
+		},
+	}
 }

client.go

@@ -1,6 +1,7 @@
 package webdav
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"net/http"
@@ -39,6 +40,11 @@ type Client struct {
 	ic *internal.Client
 }
 
+// NewClient creates a new WebDAV client.
+//
+// If the HTTPClient is nil, http.DefaultClient is used.
+//
+// To use HTTP basic authentication, HTTPClientWithBasicAuth can be used.
 func NewClient(c HTTPClient, endpoint string) (*Client, error) {
 	ic, err := internal.NewClient(c, endpoint)
 	if err != nil {
@@ -47,10 +53,13 @@ func NewClient(c HTTPClient, endpoint string) (*Client, error) {
 	return &Client{ic}, nil
 }
 
-func (c *Client) FindCurrentUserPrincipal() (string, error) {
-	propfind := internal.NewPropNamePropfind(internal.CurrentUserPrincipalName)
+// FindCurrentUserPrincipal finds the current user's principal path.
+func (c *Client) FindCurrentUserPrincipal(ctx context.Context) (string, error) {
+	propfind := internal.NewPropNamePropFind(internal.CurrentUserPrincipalName)
 
-	resp, err := c.ic.PropfindFlat("", propfind)
+	// TODO: consider retrying on the root URI "/" if this fails, as suggested
+	// by the RFC?
+	resp, err := c.ic.PropFindFlat(ctx, "", propfind)
 	if err != nil {
 		return "", err
 	}
@@ -66,7 +75,7 @@ func (c *Client) FindCurrentUserPrincipal() (string, error) {
 	return prop.Href.Path, nil
 }
 
-var fileInfoPropfind = internal.NewPropNamePropfind(
+var fileInfoPropFind = internal.NewPropNamePropFind(
 	internal.ResourceTypeName,
 	internal.GetContentLengthName,
 	internal.GetLastModifiedName,
@@ -86,6 +95,7 @@ func fileInfoFromResponse(resp *internal.Response) (*FileInfo, error) {
 	if err := resp.DecodeProp(&resType); err != nil {
 		return nil, err
 	}
+
 	if resType.Is(internal.CollectionName) {
 		fi.IsDir = true
 	} else {
@@ -94,11 +104,6 @@ func fileInfoFromResponse(resp *internal.Response) (*FileInfo, error) {
 			return nil, err
 		}
 
-		var getMod internal.GetLastModified
-		if err := resp.DecodeProp(&getMod); err != nil && !internal.IsNotFound(err) {
-			return nil, err
-		}
-
 		var getType internal.GetContentType
 		if err := resp.DecodeProp(&getType); err != nil && !internal.IsNotFound(err) {
 			return nil, err
@@ -110,29 +115,36 @@ func fileInfoFromResponse(resp *internal.Response) (*FileInfo, error) {
 		}
 
 		fi.Size = getLen.Length
-		fi.ModTime = time.Time(getMod.LastModified)
 		fi.MIMEType = getType.Type
 		fi.ETag = string(getETag.ETag)
 	}
 
+	var getMod internal.GetLastModified
+	if err := resp.DecodeProp(&getMod); err != nil && !internal.IsNotFound(err) {
+		return nil, err
+	}
+	fi.ModTime = time.Time(getMod.LastModified)
+
 	return fi, nil
 }
 
-func (c *Client) Stat(name string) (*FileInfo, error) {
-	resp, err := c.ic.PropfindFlat(name, fileInfoPropfind)
+// Stat fetches a FileInfo for a single file.
+func (c *Client) Stat(ctx context.Context, name string) (*FileInfo, error) {
+	resp, err := c.ic.PropFindFlat(ctx, name, fileInfoPropFind)
 	if err != nil {
 		return nil, err
 	}
 	return fileInfoFromResponse(resp)
 }
 
-func (c *Client) Open(name string) (io.ReadCloser, error) {
+// Open fetches a file's contents.
+func (c *Client) Open(ctx context.Context, name string) (io.ReadCloser, error) {
 	req, err := c.ic.NewRequest(http.MethodGet, name, nil)
 	if err != nil {
 		return nil, err
 	}
 
-	resp, err := c.ic.Do(req)
+	resp, err := c.ic.Do(req.WithContext(ctx))
 	if err != nil {
 		return nil, err
 	}
@@ -140,13 +152,14 @@ func (c *Client) Open(name string) (io.ReadCloser, error) {
 	return resp.Body, nil
 }
 
-func (c *Client) Readdir(name string, recursive bool) ([]FileInfo, error) {
+// ReadDir lists files in a directory.
+func (c *Client) ReadDir(ctx context.Context, name string, recursive bool) ([]FileInfo, error) {
 	depth := internal.DepthOne
 	if recursive {
 		depth = internal.DepthInfinity
 	}
 
-	ms, err := c.ic.Propfind(name, depth, fileInfoPropfind)
+	ms, err := c.ic.PropFind(ctx, name, depth, fileInfoPropFind)
 	if err != nil {
 		return nil, err
 	}
@@ -179,7 +192,8 @@ func (fw *fileWriter) Close() error {
 	return <-fw.done
 }
 
-func (c *Client) Create(name string) (io.WriteCloser, error) {
+// Create writes a file's contents.
+func (c *Client) Create(ctx context.Context, name string) (io.WriteCloser, error) {
 	pr, pw := io.Pipe()
 
 	req, err := c.ic.NewRequest(http.MethodPut, name, pr)
@@ -190,55 +204,98 @@ func (c *Client) Create(name string) (io.WriteCloser, error) {
 
 	done := make(chan error, 1)
 	go func() {
-		_, err := c.ic.Do(req)
-		done <- err
+		resp, err := c.ic.Do(req.WithContext(ctx))
+		if err != nil {
+			done <- err
+			return
+		}
+		resp.Body.Close()
+		done <- nil
 	}()
 
 	return &fileWriter{pw, done}, nil
 }
 
-func (c *Client) RemoveAll(name string) error {
+// RemoveAll deletes a file. If the file is a directory, all of its descendants
+// are recursively deleted as well.
+func (c *Client) RemoveAll(ctx context.Context, name string) error {
 	req, err := c.ic.NewRequest(http.MethodDelete, name, nil)
 	if err != nil {
 		return err
 	}
 
-	_, err = c.ic.Do(req)
-	return err
+	resp, err := c.ic.Do(req.WithContext(ctx))
+	if err != nil {
+		return err
+	}
+	resp.Body.Close()
+	return nil
 }
 
-func (c *Client) Mkdir(name string) error {
+// Mkdir creates a new directory.
+func (c *Client) Mkdir(ctx context.Context, name string) error {
 	req, err := c.ic.NewRequest("MKCOL", name, nil)
 	if err != nil {
 		return err
 	}
 
-	_, err = c.ic.Do(req)
-	return err
+	resp, err := c.ic.Do(req.WithContext(ctx))
+	if err != nil {
+		return err
+	}
+	resp.Body.Close()
+	return nil
 }
 
-func (c *Client) CopyAll(name, dest string, overwrite bool) error {
+// Copy copies a file.
+//
+// By default, if the file is a directory, all descendants are recursively
+// copied as well.
+func (c *Client) Copy(ctx context.Context, name, dest string, options *CopyOptions) error {
+	if options == nil {
+		options = new(CopyOptions)
+	}
+
 	req, err := c.ic.NewRequest("COPY", name, nil)
 	if err != nil {
 		return err
 	}
 
-	req.Header.Set("Destination", c.ic.ResolveHref(dest).String())
-	req.Header.Set("Overwrite", internal.FormatOverwrite(overwrite))
+	depth := internal.DepthInfinity
+	if options.NoRecursive {
+		depth = internal.DepthZero
+	}
 
-	_, err = c.ic.Do(req)
-	return err
+	req.Header.Set("Destination", c.ic.ResolveHref(dest).String())
+	req.Header.Set("Overwrite", internal.FormatOverwrite(!options.NoOverwrite))
+	req.Header.Set("Depth", depth.String())
+
+	resp, err := c.ic.Do(req.WithContext(ctx))
+	if err != nil {
+		return err
+	}
+	resp.Body.Close()
+	return nil
 }
 
-func (c *Client) MoveAll(name, dest string, overwrite bool) error {
+// Move moves a file.
+func (c *Client) Move(ctx context.Context, name, dest string, options *MoveOptions) error {
+	if options == nil {
+		options = new(MoveOptions)
+	}
+
 	req, err := c.ic.NewRequest("MOVE", name, nil)
 	if err != nil {
 		return err
 	}
 
 	req.Header.Set("Destination", c.ic.ResolveHref(dest).String())
-	req.Header.Set("Overwrite", internal.FormatOverwrite(overwrite))
+	req.Header.Set("Overwrite", internal.FormatOverwrite(!options.NoOverwrite))
 
-	_, err = c.ic.Do(req)
-	return err
+	resp, err := c.ic.Do(req.WithContext(ctx))
+	if err != nil {
+		return err
+	}
+	resp.Body.Close()
+	return nil
 }

elements.go

@@ -0,0 +1,32 @@
+package webdav
+
+import (
+	"encoding/xml"
+
+	"github.com/emersion/go-webdav/internal"
+)
+
+var (
+	principalName                = xml.Name{"DAV:", "principal"}
+	principalAlternateURISetName = xml.Name{"DAV:", "alternate-URI-set"}
+	principalURLName             = xml.Name{"DAV:", "principal-URL"}
+	groupMembershipName          = xml.Name{"DAV:", "group-membership"}
+)
+
+// https://datatracker.ietf.org/doc/html/rfc3744#section-4.1
+type principalAlternateURISet struct {
+	XMLName xml.Name        `xml:"DAV: alternate-URI-set"`
+	Hrefs   []internal.Href `xml:"href"`
+}
+
+// https://datatracker.ietf.org/doc/html/rfc3744#section-4.2
+type principalURL struct {
+	XMLName xml.Name      `xml:"DAV: principal-URL"`
+	Href    internal.Href `xml:"href"`
+}
+
+// https://datatracker.ietf.org/doc/html/rfc3744#section-4.4
+type groupMembership struct {
+	XMLName xml.Name        `xml:"DAV: group-membership"`
+	Hrefs   []internal.Href `xml:"href"`
+}

fs_local.go

@@ -1,6 +1,7 @@
 package webdav
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"mime"
@@ -13,8 +14,11 @@ import (
 	"github.com/emersion/go-webdav/internal"
 )
 
+// LocalFileSystem implements FileSystem for a local directory.
 type LocalFileSystem string
 
+var _ FileSystem = LocalFileSystem("")
+
 func (fs LocalFileSystem) localPath(name string) (string, error) {
 	if (filepath.Separator != '/' && strings.IndexRune(name, filepath.Separator) >= 0) || strings.Contains(name, "\x00") {
 		return "", internal.HTTPErrorf(http.StatusBadRequest, "webdav: invalid character in path")
@@ -34,7 +38,7 @@ func (fs LocalFileSystem) externalPath(name string) (string, error) {
 	return "/" + filepath.ToSlash(rel), nil
 }
 
-func (fs LocalFileSystem) Open(name string) (io.ReadCloser, error) {
+func (fs LocalFileSystem) Open(ctx context.Context, name string) (io.ReadCloser, error) {
 	p, err := fs.localPath(name)
 	if err != nil {
 		return nil, err
@@ -59,19 +63,31 @@ func fileInfoFromOS(p string, fi os.FileInfo) *FileInfo {
 	}
 }
 
-func (fs LocalFileSystem) Stat(name string) (*FileInfo, error) {
+func errFromOS(err error) error {
+	if os.IsNotExist(err) {
+		return NewHTTPError(http.StatusNotFound, err)
+	} else if os.IsPermission(err) {
+		return NewHTTPError(http.StatusForbidden, err)
+	} else if os.IsTimeout(err) {
+		return NewHTTPError(http.StatusServiceUnavailable, err)
+	} else {
+		return err
+	}
+}
+
+func (fs LocalFileSystem) Stat(ctx context.Context, name string) (*FileInfo, error) {
 	p, err := fs.localPath(name)
 	if err != nil {
 		return nil, err
 	}
 	fi, err := os.Stat(p)
 	if err != nil {
-		return nil, err
+		return nil, errFromOS(err)
 	}
 	return fileInfoFromOS(name, fi), nil
 }
 
-func (fs LocalFileSystem) Readdir(name string, recursive bool) ([]FileInfo, error) {
+func (fs LocalFileSystem) ReadDir(ctx context.Context, name string, recursive bool) ([]FileInfo, error) {
 	path, err := fs.localPath(name)
 	if err != nil {
 		return nil, err
@@ -95,18 +111,60 @@ func (fs LocalFileSystem) Readdir(name string, recursive bool) ([]FileInfo, erro
 		}
 		return nil
 	})
-	return l, err
+	return l, errFromOS(err)
 }
 
-func (fs LocalFileSystem) Create(name string) (io.WriteCloser, error) {
+func (fs LocalFileSystem) Create(ctx context.Context, name string, body io.ReadCloser, opts *CreateOptions) (fi *FileInfo, created bool, err error) {
 	p, err := fs.localPath(name)
 	if err != nil {
-		return nil, err
+		return nil, false, err
 	}
-	return os.Create(p)
+	fi, _ = fs.Stat(ctx, name)
+	created = fi == nil
+	etag := ""
+	if fi != nil {
+		etag = fi.ETag
+	}
+
+	if opts.IfMatch.IsSet() {
+		if ok, err := opts.IfMatch.MatchETag(etag); err != nil {
+			return nil, false, NewHTTPError(http.StatusBadRequest, err)
+		} else if !ok {
+			return nil, false, NewHTTPError(http.StatusPreconditionFailed, fmt.Errorf("If-Match condition failed"))
+		}
+	}
+	if opts.IfNoneMatch.IsSet() {
+		if ok, err := opts.IfNoneMatch.MatchETag(etag); err != nil {
+			return nil, false, NewHTTPError(http.StatusBadRequest, err)
+		} else if ok {
+			return nil, false, NewHTTPError(http.StatusPreconditionFailed, fmt.Errorf("If-None-Match condition failed"))
+		}
+	}
+
+	wc, err := os.Create(p)
+	if err != nil {
+		return nil, false, errFromOS(err)
+	}
+	defer wc.Close()
+
+	if _, err := io.Copy(wc, body); err != nil {
+		os.Remove(p)
+		return nil, false, err
+	}
+	if err := wc.Close(); err != nil {
+		os.Remove(p)
+		return nil, false, err
+	}
+
+	fi, err = fs.Stat(ctx, name)
+	if err != nil {
+		return nil, false, err
+	}
+
+	return fi, created, err
 }
 
-func (fs LocalFileSystem) RemoveAll(name string) error {
+func (fs LocalFileSystem) RemoveAll(ctx context.Context, name string) error {
 	p, err := fs.localPath(name)
 	if err != nil {
 		return err
@@ -115,31 +173,32 @@ func (fs LocalFileSystem) RemoveAll(name string) error {
 	// WebDAV semantics are that it should return a "404 Not Found" error in
 	// case the resource doesn't exist. We need to Stat before RemoveAll.
 	if _, err = os.Stat(p); err != nil {
-		return err
+		return errFromOS(err)
 	}
 
-	return os.RemoveAll(p)
+	return errFromOS(os.RemoveAll(p))
 }
 
-func (fs LocalFileSystem) Mkdir(name string) error {
+func (fs LocalFileSystem) Mkdir(ctx context.Context, name string) error {
 	p, err := fs.localPath(name)
 	if err != nil {
 		return err
 	}
-	return os.Mkdir(p, 0755)
+	return errFromOS(os.Mkdir(p, 0755))
 }
 
 func copyRegularFile(src, dst string, perm os.FileMode) error {
 	srcFile, err := os.Open(src)
 	if err != nil {
-		return err
+		return errFromOS(err)
 	}
 	defer srcFile.Close()
 
 	dstFile, err := os.OpenFile(dst, os.O_RDWR|os.O_CREATE|os.O_TRUNC, perm)
-	if err != nil {
-		// TODO: send http.StatusConflict on os.IsNotExist
-		return err
+	if os.IsNotExist(err) {
+		return NewHTTPError(http.StatusConflict, err)
+	} else if err != nil {
+		return errFromOS(err)
 	}
 	defer dstFile.Close()
 
@@ -150,7 +209,7 @@ func copyRegularFile(src, dst string, perm os.FileMode) error {
 	return dstFile.Close()
 }
 
-func (fs LocalFileSystem) Copy(src, dst string, recursive, overwrite bool) (created bool, err error) {
+func (fs LocalFileSystem) Copy(ctx context.Context, src, dst string, options *CopyOptions) (created bool, err error) {
 	srcPath, err := fs.localPath(src)
 	if err != nil {
 		return false, err
@@ -165,21 +224,21 @@ func (fs LocalFileSystem) Copy(src, dst string, recursive, overwrite bool) (crea
 
 	srcInfo, err := os.Stat(srcPath)
 	if err != nil {
-		return false, err
+		return false, errFromOS(err)
 	}
 	srcPerm := srcInfo.Mode() & os.ModePerm
 
 	if _, err := os.Stat(dstPath); err != nil {
 		if !os.IsNotExist(err) {
-			return false, err
+			return false, errFromOS(err)
 		}
 		created = true
 	} else {
-		if !overwrite {
-			return false, os.ErrExist
+		if options.NoOverwrite {
+			return false, NewHTTPError(http.StatusPreconditionFailed, os.ErrExist)
 		}
 		if err := os.RemoveAll(dstPath); err != nil {
-			return false, err
+			return false, errFromOS(err)
 		}
 	}
 
@@ -190,7 +249,7 @@ func (fs LocalFileSystem) Copy(src, dst string, recursive, overwrite bool) (crea
 
 		if fi.IsDir() {
 			if err := os.Mkdir(dstPath, srcPerm); err != nil {
-				return err
+				return errFromOS(err)
 			}
 		} else {
 			if err := copyRegularFile(srcPath, dstPath, srcPerm); err != nil {
@@ -198,19 +257,19 @@ func (fs LocalFileSystem) Copy(src, dst string, recursive, overwrite bool) (crea
 			}
 		}
 
-		if fi.IsDir() && !recursive {
+		if fi.IsDir() && options.NoRecursive {
 			return filepath.SkipDir
 		}
 		return nil
 	})
 	if err != nil {
-		return false, err
+		return false, errFromOS(err)
 	}
 
 	return created, nil
 }
 
-func (fs LocalFileSystem) MoveAll(src, dst string, overwrite bool) (created bool, err error) {
+func (fs LocalFileSystem) Move(ctx context.Context, src, dst string, options *MoveOptions) (created bool, err error) {
 	srcPath, err := fs.localPath(src)
 	if err != nil {
 		return false, err
@@ -222,23 +281,21 @@ func (fs LocalFileSystem) MoveAll(src, dst string, overwrite bool) (created bool
 
 	if _, err := os.Stat(dstPath); err != nil {
 		if !os.IsNotExist(err) {
-			return false, err
+			return false, errFromOS(err)
 		}
 		created = true
 	} else {
-		if !overwrite {
-			return false, os.ErrExist
+		if options.NoOverwrite {
+			return false, NewHTTPError(http.StatusPreconditionFailed, os.ErrExist)
 		}
 		if err := os.RemoveAll(dstPath); err != nil {
-			return false, err
+			return false, errFromOS(err)
 		}
 	}
 
 	if err := os.Rename(srcPath, dstPath); err != nil {
-		return false, err
+		return false, errFromOS(err)
 	}
 
 	return created, nil
 }
-
-var _ FileSystem = LocalFileSystem("")

go.mod

@@ -3,6 +3,6 @@ module github.com/emersion/go-webdav
 go 1.13
 
 require (
-	github.com/emersion/go-ical v0.0.0-20200224201310-cd514449c39e
-	github.com/emersion/go-vcard v0.0.0-20191221110513-5f81fa0d3cc7
+	github.com/emersion/go-ical v0.0.0-20240127095438-fc1c9d8fb2b6
+	github.com/emersion/go-vcard v0.0.0-20230815062825-8fda7d206ec9
 )

go.sum

@@ -1,4 +1,6 @@
-github.com/emersion/go-ical v0.0.0-20200224201310-cd514449c39e h1:YGM1sI7edZOt8KAfX9Miq/X99d2QXdgjkJ7vN4HjxAA=
-github.com/emersion/go-ical v0.0.0-20200224201310-cd514449c39e/go.mod h1:4xVTBPcT43a1pp3vdaa+FuRdX5XhKCZPpWv7m0z9ByM=
-github.com/emersion/go-vcard v0.0.0-20191221110513-5f81fa0d3cc7 h1:SE+tcd+0kn0cT4MqTo66gmkjqWHF1Z+Yha5/rhLs/H8=
-github.com/emersion/go-vcard v0.0.0-20191221110513-5f81fa0d3cc7/go.mod h1:HMJKR5wlh/ziNp+sHEDV2ltblO4JD2+IdDOWtGcQBTM=
+github.com/emersion/go-ical v0.0.0-20240127095438-fc1c9d8fb2b6 h1:kHoSgklT8weIDl6R6xFpBJ5IioRdBU1v2X2aCZRVCcM=
+github.com/emersion/go-ical v0.0.0-20240127095438-fc1c9d8fb2b6/go.mod h1:BEksegNspIkjCQfmzWgsgbu6KdeJ/4LwUZs7DMBzjzw=
+github.com/emersion/go-vcard v0.0.0-20230815062825-8fda7d206ec9 h1:ATgqloALX6cHCranzkLb8/zjivwQ9DWWDCQRnxTPfaA=
+github.com/emersion/go-vcard v0.0.0-20230815062825-8fda7d206ec9/go.mod h1:HMJKR5wlh/ziNp+sHEDV2ltblO4JD2+IdDOWtGcQBTM=
+github.com/teambition/rrule-go v1.8.2 h1:lIjpjvWTj9fFUZCmuoVDrKVOtdiyzbzc93qTmRVe/J8=
+github.com/teambition/rrule-go v1.8.2/go.mod h1:Ieq5AbrKGciP1V//Wq8ktsTXwSwJHDD5mD/wLBGl3p4=

internal/client.go

@@ -2,10 +2,12 @@ package internal
 
 import (
 	"bytes"
+	"context"
 	"encoding/xml"
 	"fmt"
 	"io"
 	"mime"
+	"net"
 	"net/http"
 	"net/url"
 	"path"
@@ -13,6 +15,42 @@ import (
 	"unicode"
 )
 
+// DiscoverContextURL performs a DNS-based CardDAV/CalDAV service discovery as
+// described in RFC 6352 section 11. It returns the URL to the CardDAV server.
+func DiscoverContextURL(ctx context.Context, service, domain string) (string, error) {
+	var resolver net.Resolver
+
+	// Only lookup TLS records, plaintext connections are insecure
+	_, addrs, err := resolver.LookupSRV(ctx, service+"s", "tcp", domain)
+	if dnsErr, ok := err.(*net.DNSError); ok {
+		if dnsErr.IsTemporary {
+			return "", err
+		}
+	} else if err != nil {
+		return "", err
+	}
+
+	if len(addrs) == 0 {
+		return "", fmt.Errorf("webdav: domain doesn't have an SRV record")
+	}
+	addr := addrs[0]
+
+	target := strings.TrimSuffix(addr.Target, ".")
+	if target == "" {
+		return "", fmt.Errorf("webdav: empty target in SRV record")
+	}
+
+	// TODO: perform a TXT lookup, check for a "path" key in the response
+	u := url.URL{Scheme: "https"}
+	if addr.Port == 443 {
+		u.Host = target
+	} else {
+		u.Host = fmt.Sprintf("%v:%v", target, addr.Port)
+	}
+	u.Path = "/.well-known/" + service
+	return u.String(), nil
+}
+
 // HTTPClient performs HTTP requests. It's implemented by *http.Client.
 type HTTPClient interface {
 	Do(req *http.Request) (*http.Response, error)
@@ -111,7 +149,7 @@ func (c *Client) Do(req *http.Request) (*http.Response, error) {
 	return resp, nil
 }
 
-func (c *Client) DoMultiStatus(req *http.Request) (*Multistatus, error) {
+func (c *Client) DoMultiStatus(req *http.Request) (*MultiStatus, error) {
 	resp, err := c.Do(req)
 	if err != nil {
 		return nil, err
@@ -123,7 +161,7 @@ func (c *Client) DoMultiStatus(req *http.Request) (*Multistatus, error) {
 	}
 
 	// TODO: the response can be quite large, support streaming Response elements
-	var ms Multistatus
+	var ms MultiStatus
 	if err := xml.NewDecoder(resp.Body).Decode(&ms); err != nil {
 		return nil, err
 	}
@@ -131,7 +169,7 @@ func (c *Client) DoMultiStatus(req *http.Request) (*Multistatus, error) {
 	return &ms, nil
 }
 
-func (c *Client) Propfind(path string, depth Depth, propfind *Propfind) (*Multistatus, error) {
+func (c *Client) PropFind(ctx context.Context, path string, depth Depth, propfind *PropFind) (*MultiStatus, error) {
 	req, err := c.NewXMLRequest("PROPFIND", path, propfind)
 	if err != nil {
 		return nil, err
@@ -139,17 +177,21 @@ func (c *Client) Propfind(path string, depth Depth, propfind *Propfind) (*Multis
 
 	req.Header.Add("Depth", depth.String())
 
-	return c.DoMultiStatus(req)
+	return c.DoMultiStatus(req.WithContext(ctx))
 }
 
 // PropfindFlat performs a PROPFIND request with a zero depth.
-func (c *Client) PropfindFlat(path string, propfind *Propfind) (*Response, error) {
-	ms, err := c.Propfind(path, DepthZero, propfind)
+func (c *Client) PropFindFlat(ctx context.Context, path string, propfind *PropFind) (*Response, error) {
+	ms, err := c.PropFind(ctx, path, DepthZero, propfind)
 	if err != nil {
 		return nil, err
 	}
 
-	return ms.Get(c.ResolveHref(path).Path)
+	// If the client followed a redirect, the Href might be different from the request path
+	if len(ms.Responses) != 1 {
+		return nil, fmt.Errorf("PROPFIND with Depth: 0 returned %d responses", len(ms.Responses))
+	}
+	return &ms.Responses[0], nil
 }
 
 func parseCommaSeparatedSet(values []string, upper bool) map[string]bool {
@@ -170,13 +212,13 @@ func parseCommaSeparatedSet(values []string, upper bool) map[string]bool {
 	return m
 }
 
-func (c *Client) Options(path string) (classes map[string]bool, methods map[string]bool, err error) {
+func (c *Client) Options(ctx context.Context, path string) (classes map[string]bool, methods map[string]bool, err error) {
 	req, err := c.NewRequest(http.MethodOptions, path, nil)
 	if err != nil {
 		return nil, nil, err
 	}
 
-	resp, err := c.Do(req)
+	resp, err := c.Do(req.WithContext(ctx))
 	if err != nil {
 		return nil, nil, err
 	}
@@ -190,3 +232,25 @@ func (c *Client) Options(path string) (classes map[string]bool, methods map[stri
 	methods = parseCommaSeparatedSet(resp.Header["Allow"], true)
 	return classes, methods, nil
 }
+
+// SyncCollection perform a `sync-collection` REPORT operation on a resource
+func (c *Client) SyncCollection(ctx context.Context, path, syncToken string, level Depth, limit *Limit, prop *Prop) (*MultiStatus, error) {
+	q := SyncCollectionQuery{
+		SyncToken: syncToken,
+		SyncLevel: level.String(),
+		Limit:     limit,
+		Prop:      prop,
+	}
+
+	req, err := c.NewXMLRequest("REPORT", path, &q)
+	if err != nil {
+		return nil, err
+	}
+
+	ms, err := c.DoMultiStatus(req.WithContext(ctx))
+	if err != nil {
+		return nil, err
+	}
+
+	return ms, nil
+}

internal/elements.go

@@ -1,11 +1,12 @@
 package internal
 
 import (
+	"encoding/base64"
 	"encoding/xml"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
-	"path"
 	"strconv"
 	"strings"
 	"time"
@@ -14,14 +15,16 @@ import (
 const Namespace = "DAV:"
 
 var (
-	ResourceTypeName     = xml.Name{"DAV:", "resourcetype"}
-	DisplayNameName      = xml.Name{"DAV:", "displayname"}
-	GetContentLengthName = xml.Name{"DAV:", "getcontentlength"}
-	GetContentTypeName   = xml.Name{"DAV:", "getcontenttype"}
-	GetLastModifiedName  = xml.Name{"DAV:", "getlastmodified"}
-	GetETagName          = xml.Name{"DAV:", "getetag"}
+	ResourceTypeName     = xml.Name{Namespace, "resourcetype"}
+	DisplayNameName      = xml.Name{Namespace, "displayname"}
+	GetContentLengthName = xml.Name{Namespace, "getcontentlength"}
+	GetContentTypeName   = xml.Name{Namespace, "getcontenttype"}
+	GetLastModifiedName  = xml.Name{Namespace, "getlastmodified"}
+	GetETagName          = xml.Name{Namespace, "getetag"}
 
-	CurrentUserPrincipalName = xml.Name{"DAV:", "current-user-principal"}
+	CurrentUserPrincipalName = xml.Name{Namespace, "current-user-principal"}
+
+	CurrentUserPrivilegeSetName = xml.Name{Namespace, "current-user-privilege-set"}
 )
 
 type Status struct {
@@ -89,36 +92,22 @@ func (h *Href) UnmarshalText(b []byte) error {
 }
 
 // https://tools.ietf.org/html/rfc4918#section-14.16
-type Multistatus struct {
+type MultiStatus struct {
 	XMLName             xml.Name   `xml:"DAV: multistatus"`
 	Responses           []Response `xml:"response"`
 	ResponseDescription string     `xml:"responsedescription,omitempty"`
+	SyncToken           string     `xml:"sync-token,omitempty"`
 }
 
-func NewMultistatus(resps ...Response) *Multistatus {
-	return &Multistatus{Responses: resps}
-}
-
-func (ms *Multistatus) Get(p string) (*Response, error) {
-	// Clean the path to avoid issues with trailing slashes
-	p = path.Clean(p)
-	for i := range ms.Responses {
-		resp := &ms.Responses[i]
-		for _, h := range resp.Hrefs {
-			if path.Clean(h.Path) == p {
-				return resp, resp.Status.Err()
-			}
-		}
-	}
-
-	return nil, fmt.Errorf("webdav: missing response for path %q", p)
+func NewMultiStatus(resps ...Response) *MultiStatus {
+	return &MultiStatus{Responses: resps}
 }
 
 // https://tools.ietf.org/html/rfc4918#section-14.24
 type Response struct {
 	XMLName             xml.Name   `xml:"DAV: response"`
 	Hrefs               []Href     `xml:"href"`
-	Propstats           []Propstat `xml:"propstat,omitempty"`
+	PropStats           []PropStat `xml:"propstat,omitempty"`
 	ResponseDescription string     `xml:"responsedescription,omitempty"`
 	Status              *Status    `xml:"status,omitempty"`
 	Error               *Error     `xml:"error,omitempty"`
@@ -133,14 +122,57 @@ func NewOKResponse(path string) *Response {
 	}
 }
 
+func NewErrorResponse(path string, err error) *Response {
+	code := http.StatusInternalServerError
+	var httpErr *HTTPError
+	if errors.As(err, &httpErr) {
+		code = httpErr.Code
+	}
+
+	var errElt *Error
+	errors.As(err, &errElt)
+
+	href := Href{Path: path}
+	return &Response{
+		Hrefs:               []Href{href},
+		Status:              &Status{Code: code},
+		ResponseDescription: err.Error(),
+		Error:               errElt,
+	}
+}
+
+func (resp *Response) Err() error {
+	if resp.Status == nil || resp.Status.Code/100 == 2 {
+		return nil
+	}
+
+	var err error
+	if resp.Error != nil {
+		err = resp.Error
+	}
+	if resp.ResponseDescription != "" {
+		if err != nil {
+			err = fmt.Errorf("%v (%w)", resp.ResponseDescription, err)
+		} else {
+			err = fmt.Errorf("%v", resp.ResponseDescription)
+		}
+	}
+
+	return &HTTPError{
+		Code: resp.Status.Code,
+		Err:  err,
+	}
+}
+
 func (resp *Response) Path() (string, error) {
-	if err := resp.Status.Err(); err != nil {
-		return "", err
+	err := resp.Err()
+	var path string
+	if len(resp.Hrefs) == 1 {
+		path = resp.Hrefs[0].Path
+	} else if err == nil {
+		err = fmt.Errorf("webdav: malformed response: expected exactly one href element, got %v", len(resp.Hrefs))
 	}
-	if len(resp.Hrefs) != 1 {
-		return "", fmt.Errorf("webdav: malformed response: expected exactly one href element, got %v", len(resp.Hrefs))
-	}
-	return resp.Hrefs[0].Path, nil
+	return path, err
 }
 
 func (resp *Response) DecodeProp(values ...interface{}) error {
@@ -150,40 +182,50 @@ func (resp *Response) DecodeProp(values ...interface{}) error {
 		if err != nil {
 			return err
 		}
-		if err := resp.Status.Err(); err != nil {
-			return err
+		if err := resp.Err(); err != nil {
+			return newPropError(name, err)
 		}
-		for _, propstat := range resp.Propstats {
+		for _, propstat := range resp.PropStats {
 			raw := propstat.Prop.Get(name)
 			if raw == nil {
 				continue
 			}
 			if err := propstat.Status.Err(); err != nil {
-				return err
+				return newPropError(name, err)
 			}
-			return raw.Decode(v)
+			if err := raw.Decode(v); err != nil {
+				return newPropError(name, err)
+			}
+			return nil
 		}
-		return HTTPErrorf(http.StatusNotFound, "missing property %s", name)
+		return newPropError(name, &HTTPError{
+			Code: http.StatusNotFound,
+			Err:  fmt.Errorf("missing property"),
+		})
 	}
 
 	return nil
 }
 
+func newPropError(name xml.Name, err error) error {
+	return fmt.Errorf("property <%v %v>: %w", name.Space, name.Local, err)
+}
+
 func (resp *Response) EncodeProp(code int, v interface{}) error {
 	raw, err := EncodeRawXMLElement(v)
 	if err != nil {
 		return err
 	}
 
-	for i := range resp.Propstats {
-		propstat := &resp.Propstats[i]
+	for i := range resp.PropStats {
+		propstat := &resp.PropStats[i]
 		if propstat.Status.Code == code {
 			propstat.Prop.Raw = append(propstat.Prop.Raw, *raw)
 			return nil
 		}
 	}
 
-	resp.Propstats = append(resp.Propstats, Propstat{
+	resp.PropStats = append(resp.PropStats, PropStat{
 		Status: Status{Code: code},
 		Prop:   Prop{Raw: []RawXMLValue{*raw}},
 	})
@@ -197,7 +239,7 @@ type Location struct {
 }
 
 // https://tools.ietf.org/html/rfc4918#section-14.22
-type Propstat struct {
+type PropStat struct {
 	XMLName             xml.Name `xml:"DAV: propstat"`
 	Prop                Prop     `xml:"prop"`
 	Status              Status   `xml:"status"`
@@ -248,7 +290,7 @@ func (p *Prop) Decode(v interface{}) error {
 }
 
 // https://tools.ietf.org/html/rfc4918#section-14.20
-type Propfind struct {
+type PropFind struct {
 	XMLName  xml.Name  `xml:"DAV: propfind"`
 	Prop     *Prop     `xml:"prop,omitempty"`
 	AllProp  *struct{} `xml:"allprop,omitempty"`
@@ -264,8 +306,8 @@ func xmlNamesToRaw(names []xml.Name) []RawXMLValue {
 	return l
 }
 
-func NewPropNamePropfind(names ...xml.Name) *Propfind {
-	return &Propfind{Prop: &Prop{Raw: xmlNamesToRaw(names)}}
+func NewPropNamePropFind(names ...xml.Name) *PropFind {
+	return &PropFind{Prop: &Prop{Raw: xmlNamesToRaw(names)}}
 }
 
 // https://tools.ietf.org/html/rfc4918#section-14.8
@@ -293,7 +335,7 @@ func (t *ResourceType) Is(name xml.Name) bool {
 	return false
 }
 
-var CollectionName = xml.Name{"DAV:", "collection"}
+var CollectionName = xml.Name{Namespace, "collection"}
 
 // https://tools.ietf.org/html/rfc4918#section-15.4
 type GetContentLength struct {
@@ -312,14 +354,14 @@ type Time time.Time
 func (t *Time) UnmarshalText(b []byte) error {
 	tt, err := http.ParseTime(string(b))
 	if err != nil {
-		return err
+		return errors.New(err.Error() + " : time_data : " + base64.StdEncoding.EncodeToString(b))
 	}
 	*t = Time(tt)
 	return nil
 }
 
 func (t *Time) MarshalText() ([]byte, error) {
-	s := time.Time(*t).Format(time.RFC1123Z)
+	s := time.Time(*t).UTC().Format(http.TimeFormat)
 	return []byte(s), nil
 }
 
@@ -378,8 +420,32 @@ type CurrentUserPrincipal struct {
 	Unauthenticated *struct{} `xml:"unauthenticated,omitempty"`
 }
 
+type CurrentUserPrivilegeSet struct {
+	XMLName   xml.Name    `xml:"DAV: current-user-privilege-set"`
+	Privilege []Privilege `xml:"privilege"`
+}
+
+type Privilege struct {
+	XMLName         xml.Name  `xml:"DAV: privilege"`
+	Read            *struct{} `xml:"DAV: read,omitempty"`
+	All             *struct{} `xml:"DAV: all,omitempty"`
+	Write           *struct{} `xml:"DAV: write,omitempty"`
+	WriteProperties *struct{} `xml:"DAV: write-properties,omitempty"`
+	WriteContent    *struct{} `xml:"DAV: write-content,omitempty"`
+}
+
+func NewAllPrivileges() []Privilege {
+	return []Privilege{
+		{Read: &struct{}{}},
+		{All: &struct{}{}},
+		{Write: &struct{}{}},
+		{WriteProperties: &struct{}{}},
+		{WriteContent: &struct{}{}},
+	}
+}
+
 // https://tools.ietf.org/html/rfc4918#section-14.19
-type Propertyupdate struct {
+type PropertyUpdate struct {
 	XMLName xml.Name `xml:"DAV: propertyupdate"`
 	Remove  []Remove `xml:"remove"`
 	Set     []Set    `xml:"set"`
@@ -396,3 +462,18 @@ type Set struct {
 	XMLName xml.Name `xml:"DAV: set"`
 	Prop    Prop     `xml:"prop"`
 }
+
+// https://tools.ietf.org/html/rfc6578#section-6.1
+type SyncCollectionQuery struct {
+	XMLName   xml.Name `xml:"DAV: sync-collection"`
+	SyncToken string   `xml:"sync-token"`
+	Limit     *Limit   `xml:"limit,omitempty"`
+	SyncLevel string   `xml:"sync-level"`
+	Prop      *Prop    `xml:"prop"`
+}
+
+// https://tools.ietf.org/html/rfc5323#section-5.17
+type Limit struct {
+	XMLName  xml.Name `xml:"DAV: limit"`
+	NResults uint     `xml:"nresults"`
+}

internal/elements_test.go

@@ -1,9 +1,11 @@
 package internal
 
 import (
+	"bytes"
 	"encoding/xml"
 	"strings"
 	"testing"
+	"time"
 )
 
 // https://tools.ietf.org/html/rfc4918#section-9.6.2
@@ -16,14 +18,20 @@ const exampleDeleteMultistatusStr = `<?xml version="1.0" encoding="utf-8" ?>
   </d:response>
 </d:multistatus>`
 
-func TestMultistatus_Get_error(t *testing.T) {
+func TestResponse_Err_error(t *testing.T) {
 	r := strings.NewReader(exampleDeleteMultistatusStr)
-	var ms Multistatus
+	var ms MultiStatus
 	if err := xml.NewDecoder(r).Decode(&ms); err != nil {
 		t.Fatalf("Decode() = %v", err)
 	}
 
-	_, err := ms.Get("/container/resource3")
+	if len(ms.Responses) != 1 {
+		t.Fatalf("expected 1 <response>, got %v", len(ms.Responses))
+	}
+
+	resp := ms.Responses[0]
+
+	err := resp.Err()
 	if err == nil {
 		t.Errorf("Multistatus.Get() returned a nil error, expected non-nil")
 	} else if httpErr, ok := err.(*HTTPError); !ok {
@@ -32,3 +40,26 @@ func TestMultistatus_Get_error(t *testing.T) {
 		t.Errorf("HTTPError.Code = %v, expected 423", httpErr.Code)
 	}
 }
+
+func TestTimeRoundTrip(t *testing.T) {
+	now := Time(time.Now().UTC())
+	want, err := now.MarshalText()
+	if err != nil {
+		t.Fatalf("could not marshal time: %+v", err)
+	}
+
+	var got Time
+	err = got.UnmarshalText(want)
+	if err != nil {
+		t.Fatalf("could not unmarshal time: %+v", err)
+	}
+
+	raw, err := got.MarshalText()
+	if err != nil {
+		t.Fatalf("could not marshal back: %+v", err)
+	}
+
+	if got, want := raw, want; !bytes.Equal(got, want) {
+		t.Fatalf("invalid round-trip:\ngot= %s\nwant=%s", got, want)
+	}
+}

internal/internal.go

@@ -2,7 +2,9 @@
 package internal
 
 import (
+	"errors"
 	"fmt"
+	"net/http"
 )
 
 // Depth indicates whether a request applies to the resource's members. It's
@@ -65,3 +67,44 @@ func FormatOverwrite(overwrite bool) string {
 		return "F"
 	}
 }
+
+type HTTPError struct {
+	Code int
+	Err  error
+}
+
+func HTTPErrorFromError(err error) *HTTPError {
+	if err == nil {
+		return nil
+	}
+	if httpErr, ok := err.(*HTTPError); ok {
+		return httpErr
+	} else {
+		return &HTTPError{http.StatusInternalServerError, err}
+	}
+}
+
+func IsNotFound(err error) bool {
+	var httpErr *HTTPError
+	if errors.As(err, &httpErr) {
+		return httpErr.Code == http.StatusNotFound
+	}
+	return false
+}
+
+func HTTPErrorf(code int, format string, a ...interface{}) *HTTPError {
+	return &HTTPError{code, fmt.Errorf(format, a...)}
+}
+
+func (err *HTTPError) Error() string {
+	s := fmt.Sprintf("%v %v", err.Code, http.StatusText(err.Code))
+	if err.Err != nil {
+		return fmt.Sprintf("%v: %v", s, err.Err)
+	} else {
+		return s
+	}
+}
+
+func (err *HTTPError) Unwrap() error {
+	return err.Err
+}

internal/server.go

@@ -2,57 +2,39 @@ package internal
 
 import (
 	"encoding/xml"
+	"errors"
 	"fmt"
+	"io"
 	"mime"
 	"net/http"
 	"net/url"
 	"strings"
 )
 
-type HTTPError struct {
-	Code int
-	Err  error
-}
-
-func HTTPErrorFromError(err error) *HTTPError {
-	if err == nil {
-		return nil
-	}
-	if httpErr, ok := err.(*HTTPError); ok {
-		return httpErr
-	} else {
-		return &HTTPError{http.StatusInternalServerError, err}
-	}
-}
-
-func IsNotFound(err error) bool {
-	return HTTPErrorFromError(err).Code == http.StatusNotFound
-}
-
-func HTTPErrorf(code int, format string, a ...interface{}) *HTTPError {
-	return &HTTPError{code, fmt.Errorf(format, a...)}
-}
-
-func (err *HTTPError) Error() string {
-	s := fmt.Sprintf("%v %v", err.Code, http.StatusText(err.Code))
-	if err.Err != nil {
-		return fmt.Sprintf("%v: %v", s, err.Err)
-	} else {
-		return s
-	}
-}
-
 func ServeError(w http.ResponseWriter, err error) {
 	code := http.StatusInternalServerError
-	if httpErr, ok := err.(*HTTPError); ok {
+	var httpErr *HTTPError
+	if errors.As(err, &httpErr) {
 		code = httpErr.Code
 	}
+
+	var errElt *Error
+	if errors.As(err, &errElt) {
+		w.WriteHeader(code)
+		ServeXML(w).Encode(errElt)
+		return
+	}
+
 	http.Error(w, err.Error(), code)
 }
 
+func isContentXML(h http.Header) bool {
+	t, _, _ := mime.ParseMediaType(h.Get("Content-Type"))
+	return t == "application/xml" || t == "text/xml"
+}
+
 func DecodeXMLRequest(r *http.Request, v interface{}) error {
-	t, _, _ := mime.ParseMediaType(r.Header.Get("Content-Type"))
-	if t != "application/xml" && t != "text/xml" {
+	if !isContentXML(r.Header) {
 		return HTTPErrorf(http.StatusBadRequest, "webdav: expected application/xml request")
 	}
 
@@ -62,13 +44,18 @@ func DecodeXMLRequest(r *http.Request, v interface{}) error {
 	return nil
 }
 
+func IsRequestBodyEmpty(r *http.Request) bool {
+	_, err := r.Body.Read(nil)
+	return err == io.EOF
+}
+
 func ServeXML(w http.ResponseWriter) *xml.Encoder {
-	w.Header().Add("Content-Type", "text/xml; charset=\"utf-8\"")
+	w.Header().Add("Content-Type", "application/xml; charset=\"utf-8\"")
 	w.Write([]byte(xml.Header))
 	return xml.NewEncoder(w)
 }
 
-func ServeMultistatus(w http.ResponseWriter, ms *Multistatus) error {
+func ServeMultiStatus(w http.ResponseWriter, ms *MultiStatus) error {
 	// TODO: streaming
 	w.WriteHeader(http.StatusMultiStatus)
 	return ServeXML(w).Encode(ms)
@@ -77,9 +64,9 @@ func ServeMultistatus(w http.ResponseWriter, ms *Multistatus) error {
 type Backend interface {
 	Options(r *http.Request) (caps []string, allow []string, err error)
 	HeadGet(w http.ResponseWriter, r *http.Request) error
-	Propfind(r *http.Request, pf *Propfind, depth Depth) (*Multistatus, error)
-	Proppatch(r *http.Request, pu *Propertyupdate) (*Response, error)
-	Put(r *http.Request) (*Href, error)
+	PropFind(r *http.Request, pf *PropFind, depth Depth) (*MultiStatus, error)
+	PropPatch(r *http.Request, pu *PropertyUpdate) (*Response, error)
+	Put(w http.ResponseWriter, r *http.Request) error
 	Delete(r *http.Request) error
 	Mkcol(r *http.Request) error
 	Copy(r *http.Request, dest *Href, recursive, overwrite bool) (created bool, err error)
@@ -101,17 +88,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		case http.MethodGet, http.MethodHead:
 			err = h.Backend.HeadGet(w, r)
 		case http.MethodPut:
-			var href *Href
-			href, err = h.Backend.Put(r)
-			if err == nil {
-				// TODO: Last-Modified, ETag, Content-Type if the request has
-				// been copied verbatim
-				if href != nil {
-					w.Header().Set("Location", (*url.URL)(href).String())
-				}
-				// TODO: http.StatusNoContent if the resource already existed
-				w.WriteHeader(http.StatusCreated)
-			}
+			err = h.Backend.Put(w, r)
 		case http.MethodDelete:
 			// TODO: send a multistatus in case of partial failure
 			err = h.Backend.Delete(r)
@@ -135,11 +112,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if err != nil {
-		code := http.StatusInternalServerError
-		if httpErr, ok := err.(*HTTPError); ok {
-			code = httpErr.Code
-		}
-		http.Error(w, err.Error(), code)
+		ServeError(w, err)
 	}
 }
 
@@ -152,14 +125,22 @@ func (h *Handler) handleOptions(w http.ResponseWriter, r *http.Request) error {
 
 	w.Header().Add("DAV", strings.Join(caps, ", "))
 	w.Header().Add("Allow", strings.Join(allow, ", "))
-	w.WriteHeader(http.StatusNoContent)
+	w.WriteHeader(http.StatusOK)
 	return nil
 }
 
 func (h *Handler) handlePropfind(w http.ResponseWriter, r *http.Request) error {
-	var propfind Propfind
-	if err := DecodeXMLRequest(r, &propfind); err != nil {
-		return err
+	var propfind PropFind
+	if isContentXML(r.Header) {
+		if err := DecodeXMLRequest(r, &propfind); err != nil {
+			return err
+		}
+	} else {
+		var b [1]byte
+		if _, err := r.Body.Read(b[:]); err != io.EOF {
+			return HTTPErrorf(http.StatusBadRequest, "webdav: unsupported request body")
+		}
+		propfind.AllProp = &struct{}{}
 	}
 
 	depth := DepthInfinity
@@ -171,23 +152,27 @@ func (h *Handler) handlePropfind(w http.ResponseWriter, r *http.Request) error {
 		}
 	}
 
-	ms, err := h.Backend.Propfind(r, &propfind, depth)
+	ms, err := h.Backend.PropFind(r, &propfind, depth)
 	if err != nil {
 		return err
 	}
 
-	return ServeMultistatus(w, ms)
+	return ServeMultiStatus(w, ms)
 }
 
-type PropfindFunc func(raw *RawXMLValue) (interface{}, error)
+type PropFindFunc func(raw *RawXMLValue) (interface{}, error)
 
-func NewPropfindResponse(path string, propfind *Propfind, props map[xml.Name]PropfindFunc) (*Response, error) {
-	resp := NewOKResponse(path)
+func PropFindValue(value interface{}) PropFindFunc {
+	return func(raw *RawXMLValue) (interface{}, error) {
+		return value, nil
+	}
+}
+
+func NewPropFindResponse(path string, propfind *PropFind, props map[xml.Name]PropFindFunc) (*Response, error) {
+	resp := &Response{Hrefs: []Href{Href{Path: path}}}
 
 	if _, ok := props[ResourceTypeName]; !ok {
-		props[ResourceTypeName] = func(*RawXMLValue) (interface{}, error) {
-			return NewResourceType(), nil
-		}
+		props[ResourceTypeName] = PropFindValue(NewResourceType())
 	}
 
 	if propfind.PropName != nil {
@@ -206,9 +191,8 @@ func NewPropfindResponse(path string, propfind *Propfind, props map[xml.Name]Pro
 
 			code := http.StatusOK
 			if err != nil {
-				// TODO: don't throw away error message here
 				code = HTTPErrorFromError(err).Code
-				val = emptyVal
+				val = NewRawXMLElement(xmlName, []xml.Attr{{Name: xml.Name{Space: "ERR", Local: "Error"}, Value: err.Error()}}, nil)
 			}
 
 			if err := resp.EncodeProp(code, val); err != nil {
@@ -229,8 +213,8 @@ func NewPropfindResponse(path string, propfind *Propfind, props map[xml.Name]Pro
 			f, ok := props[xmlName]
 			if ok {
 				if v, err := f(&raw); err != nil {
-					// TODO: don't throw away error message here
 					code = HTTPErrorFromError(err).Code
+					val = NewRawXMLElement(xmlName, []xml.Attr{{Name: xml.Name{Space: "ERR", Local: "Error"}, Value: err.Error()}}, nil)
 				} else {
 					code = http.StatusOK
 					val = v
@@ -251,18 +235,18 @@ func NewPropfindResponse(path string, propfind *Propfind, props map[xml.Name]Pro
 }
 
 func (h *Handler) handleProppatch(w http.ResponseWriter, r *http.Request) error {
-	var update Propertyupdate
+	var update PropertyUpdate
 	if err := DecodeXMLRequest(r, &update); err != nil {
 		return err
 	}
 
-	resp, err := h.Backend.Proppatch(r, &update)
+	resp, err := h.Backend.PropPatch(r, &update)
 	if err != nil {
 		return err
 	}
 
-	ms := NewMultistatus(*resp)
-	return ServeMultistatus(w, ms)
+	ms := NewMultiStatus(*resp)
+	return ServeMultiStatus(w, ms)
 }
 
 func parseDestination(h http.Header) (*Href, error) {

server.go

@@ -1,25 +1,27 @@
 package webdav
 
 import (
+	"context"
 	"encoding/xml"
 	"io"
 	"net/http"
 	"os"
 	"strconv"
+	"strings"
 
 	"github.com/emersion/go-webdav/internal"
 )
 
 // FileSystem is a WebDAV server backend.
 type FileSystem interface {
-	Open(name string) (io.ReadCloser, error)
-	Stat(name string) (*FileInfo, error)
-	Readdir(name string, recursive bool) ([]FileInfo, error)
-	Create(name string) (io.WriteCloser, error)
-	RemoveAll(name string) error
-	Mkdir(name string) error
-	Copy(name, dest string, recursive, overwrite bool) (created bool, err error)
-	MoveAll(name, dest string, overwrite bool) (created bool, err error)
+	Open(ctx context.Context, name string) (io.ReadCloser, error)
+	Stat(ctx context.Context, name string) (*FileInfo, error)
+	ReadDir(ctx context.Context, name string, recursive bool) ([]FileInfo, error)
+	Create(ctx context.Context, name string, body io.ReadCloser, opts *CreateOptions) (fileInfo *FileInfo, created bool, err error)
+	RemoveAll(ctx context.Context, name string) error
+	Mkdir(ctx context.Context, name string) error
+	Copy(ctx context.Context, name, dest string, options *CopyOptions) (created bool, err error)
+	Move(ctx context.Context, name, dest string, options *MoveOptions) (created bool, err error)
 }
 
 // Handler handles WebDAV HTTP requests. It can be used to create a WebDAV
@@ -36,17 +38,26 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	b := backend{h.FileSystem}
-	hh := internal.Handler{&b}
+	hh := internal.Handler{Backend: &b}
 	hh.ServeHTTP(w, r)
 }
 
+// NewHTTPError creates a new error that is associated with an HTTP status code
+// and optionally an error that lead to it. Backends can use this functions to
+// return errors that convey some semantics (e.g. 404 not found, 403 access
+// denied, etc.) while also providing an (optional) arbitrary error context
+// (intended for humans).
+func NewHTTPError(statusCode int, cause error) error {
+	return &internal.HTTPError{Code: statusCode, Err: cause}
+}
+
 type backend struct {
 	FileSystem FileSystem
 }
 
 func (b *backend) Options(r *http.Request) (caps []string, allow []string, err error) {
-	fi, err := b.FileSystem.Stat(r.URL.Path)
-	if os.IsNotExist(err) {
+	fi, err := b.FileSystem.Stat(r.Context(), r.URL.Path)
+	if internal.IsNotFound(err) {
 		return nil, []string{http.MethodOptions, http.MethodPut, "MKCOL"}, nil
 	} else if err != nil {
 		return nil, nil, err
@@ -68,17 +79,15 @@ func (b *backend) Options(r *http.Request) (caps []string, allow []string, err e
 }
 
 func (b *backend) HeadGet(w http.ResponseWriter, r *http.Request) error {
-	fi, err := b.FileSystem.Stat(r.URL.Path)
-	if os.IsNotExist(err) {
-		return &internal.HTTPError{Code: http.StatusNotFound, Err: err}
-	} else if err != nil {
+	fi, err := b.FileSystem.Stat(r.Context(), r.URL.Path)
+	if err != nil {
 		return err
 	}
 	if fi.IsDir {
 		return &internal.HTTPError{Code: http.StatusMethodNotAllowed}
 	}
 
-	f, err := b.FileSystem.Open(r.URL.Path)
+	f, err := b.FileSystem.Open(r.Context(), r.URL.Path)
 	if err != nil {
 		return err
 	}
@@ -106,33 +115,31 @@ func (b *backend) HeadGet(w http.ResponseWriter, r *http.Request) error {
 	return nil
 }
 
-func (b *backend) Propfind(r *http.Request, propfind *internal.Propfind, depth internal.Depth) (*internal.Multistatus, error) {
+func (b *backend) PropFind(r *http.Request, propfind *internal.PropFind, depth internal.Depth) (*internal.MultiStatus, error) {
 	// TODO: use partial error Response on error
 
-	fi, err := b.FileSystem.Stat(r.URL.Path)
-	if os.IsNotExist(err) {
-		return nil, &internal.HTTPError{Code: http.StatusNotFound, Err: err}
-	} else if err != nil {
+	fi, err := b.FileSystem.Stat(r.Context(), r.URL.Path)
+	if err != nil {
 		return nil, err
 	}
 
 	var resps []internal.Response
 	if depth != internal.DepthZero && fi.IsDir {
-		children, err := b.FileSystem.Readdir(r.URL.Path, depth == internal.DepthInfinity)
+		children, err := b.FileSystem.ReadDir(r.Context(), r.URL.Path, depth == internal.DepthInfinity)
 		if err != nil {
 			return nil, err
 		}
 
 		resps = make([]internal.Response, len(children))
 		for i, child := range children {
-			resp, err := b.propfindFile(propfind, &child)
+			resp, err := b.propFindFile(propfind, &child)
 			if err != nil {
 				return nil, err
 			}
 			resps[i] = *resp
 		}
 	} else {
-		resp, err := b.propfindFile(propfind, fi)
+		resp, err := b.propFindFile(propfind, fi)
 		if err != nil {
 			return nil, err
 		}
@@ -140,11 +147,11 @@ func (b *backend) Propfind(r *http.Request, propfind *internal.Propfind, depth i
 		resps = []internal.Response{*resp}
 	}
 
-	return internal.NewMultistatus(resps...), nil
+	return internal.NewMultiStatus(resps...), nil
 }
 
-func (b *backend) propfindFile(propfind *internal.Propfind, fi *FileInfo) (*internal.Response, error) {
-	props := make(map[xml.Name]internal.PropfindFunc)
+func (b *backend) propFindFile(propfind *internal.PropFind, fi *FileInfo) (*internal.Response, error) {
+	props := make(map[xml.Name]internal.PropFindFunc)
 
 	props[internal.ResourceTypeName] = func(*internal.RawXMLValue) (interface{}, error) {
 		var types []xml.Name
@@ -155,72 +162,90 @@ func (b *backend) propfindFile(propfind *internal.Propfind, fi *FileInfo) (*inte
 	}
 
 	if !fi.IsDir {
-		props[internal.GetContentLengthName] = func(*internal.RawXMLValue) (interface{}, error) {
-			return &internal.GetContentLength{Length: fi.Size}, nil
-		}
+		props[internal.GetContentLengthName] = internal.PropFindValue(&internal.GetContentLength{
+			Length: fi.Size,
+		})
 
 		if !fi.ModTime.IsZero() {
-			props[internal.GetLastModifiedName] = func(*internal.RawXMLValue) (interface{}, error) {
-				return &internal.GetLastModified{LastModified: internal.Time(fi.ModTime)}, nil
-			}
+			props[internal.GetLastModifiedName] = internal.PropFindValue(&internal.GetLastModified{
+				LastModified: internal.Time(fi.ModTime),
+			})
 		}
 
 		if fi.MIMEType != "" {
-			props[internal.GetContentTypeName] = func(*internal.RawXMLValue) (interface{}, error) {
-				return &internal.GetContentType{Type: fi.MIMEType}, nil
-			}
+			props[internal.GetContentTypeName] = internal.PropFindValue(&internal.GetContentType{
+				Type: fi.MIMEType,
+			})
 		}
 
 		if fi.ETag != "" {
-			props[internal.GetETagName] = func(*internal.RawXMLValue) (interface{}, error) {
-				return &internal.GetETag{ETag: internal.ETag(fi.ETag)}, nil
-			}
+			props[internal.GetETagName] = internal.PropFindValue(&internal.GetETag{
+				ETag: internal.ETag(fi.ETag),
+			})
 		}
 	}
 
-	return internal.NewPropfindResponse(fi.Path, propfind, props)
+	return internal.NewPropFindResponse(fi.Path, propfind, props)
 }
 
-func (b *backend) Proppatch(r *http.Request, update *internal.Propertyupdate) (*internal.Response, error) {
+func (b *backend) PropPatch(r *http.Request, update *internal.PropertyUpdate) (*internal.Response, error) {
 	// TODO: return a failed Response instead
 	return nil, internal.HTTPErrorf(http.StatusForbidden, "webdav: PROPPATCH is unsupported")
 }
 
-func (b *backend) Put(r *http.Request) (*internal.Href, error) {
-	wc, err := b.FileSystem.Create(r.URL.Path)
+func (b *backend) Put(w http.ResponseWriter, r *http.Request) error {
+	ifNoneMatch := ConditionalMatch(r.Header.Get("If-None-Match"))
+	ifMatch := ConditionalMatch(r.Header.Get("If-Match"))
+
+	opts := CreateOptions{
+		IfNoneMatch: ifNoneMatch,
+		IfMatch:     ifMatch,
+	}
+	fi, created, err := b.FileSystem.Create(r.Context(), r.URL.Path, r.Body, &opts)
 	if err != nil {
-		return nil, err
-	}
-	defer wc.Close()
-
-	if _, err := io.Copy(wc, r.Body); err != nil {
-		return nil, err
+		return err
 	}
 
-	return nil, wc.Close()
+	if fi.MIMEType != "" {
+		w.Header().Set("Content-Type", fi.MIMEType)
+	}
+	if !fi.ModTime.IsZero() {
+		w.Header().Set("Last-Modified", fi.ModTime.UTC().Format(http.TimeFormat))
+	}
+	if fi.ETag != "" {
+		w.Header().Set("ETag", internal.ETag(fi.ETag).String())
+	}
+
+	if created {
+		w.WriteHeader(http.StatusCreated)
+	} else {
+		w.WriteHeader(http.StatusNoContent)
+	}
+
+	return nil
 }
 
 func (b *backend) Delete(r *http.Request) error {
-	err := b.FileSystem.RemoveAll(r.URL.Path)
-	if os.IsNotExist(err) {
-		return &internal.HTTPError{Code: http.StatusNotFound, Err: err}
-	}
-	return err
+	return b.FileSystem.RemoveAll(r.Context(), r.URL.Path)
 }
 
 func (b *backend) Mkcol(r *http.Request) error {
 	if r.Header.Get("Content-Type") != "" {
 		return internal.HTTPErrorf(http.StatusUnsupportedMediaType, "webdav: request body not supported in MKCOL request")
 	}
-	err := b.FileSystem.Mkdir(r.URL.Path)
-	if os.IsNotExist(err) {
+	err := b.FileSystem.Mkdir(r.Context(), r.URL.Path)
+	if internal.IsNotFound(err) {
 		return &internal.HTTPError{Code: http.StatusConflict, Err: err}
 	}
 	return err
 }
 
 func (b *backend) Copy(r *http.Request, dest *internal.Href, recursive, overwrite bool) (created bool, err error) {
-	created, err = b.FileSystem.Copy(r.URL.Path, dest.Path, recursive, overwrite)
+	options := CopyOptions{
+		NoRecursive: !recursive,
+		NoOverwrite: !overwrite,
+	}
+	created, err = b.FileSystem.Copy(r.Context(), r.URL.Path, dest.Path, &options)
 	if os.IsExist(err) {
 		return false, &internal.HTTPError{http.StatusPreconditionFailed, err}
 	}
@@ -228,9 +253,90 @@ func (b *backend) Copy(r *http.Request, dest *internal.Href, recursive, overwrit
 }
 
 func (b *backend) Move(r *http.Request, dest *internal.Href, overwrite bool) (created bool, err error) {
-	created, err = b.FileSystem.MoveAll(r.URL.Path, dest.Path, overwrite)
+	options := MoveOptions{
+		NoOverwrite: !overwrite,
+	}
+	created, err = b.FileSystem.Move(r.Context(), r.URL.Path, dest.Path, &options)
 	if os.IsExist(err) {
 		return false, &internal.HTTPError{http.StatusPreconditionFailed, err}
 	}
 	return created, err
 }
+
+// BackendSuppliedHomeSet represents either a CalDAV calendar-home-set or a
+// CardDAV addressbook-home-set. It should only be created via
+// caldav.NewCalendarHomeSet or carddav.NewAddressBookHomeSet. Only to
+// be used server-side, for listing a user's home sets as determined by the
+// (external) backend.
+type BackendSuppliedHomeSet interface {
+	GetXMLName() xml.Name
+}
+
+// UserPrincipalBackend can determine the current user's principal URL for a
+// given request context.
+type UserPrincipalBackend interface {
+	CurrentUserPrincipal(ctx context.Context) (string, error)
+}
+
+// Capability indicates the features that a server supports.
+type Capability string
+
+// ServePrincipalOptions holds options for ServePrincipal.
+type ServePrincipalOptions struct {
+	CurrentUserPrincipalPath string
+	HomeSets                 []BackendSuppliedHomeSet
+	Capabilities             []Capability
+}
+
+// ServePrincipal replies to requests for a principal URL.
+func ServePrincipal(w http.ResponseWriter, r *http.Request, options *ServePrincipalOptions) {
+	switch r.Method {
+	case http.MethodOptions:
+		caps := []string{"1", "3"}
+		for _, c := range options.Capabilities {
+			caps = append(caps, string(c))
+		}
+		allow := []string{http.MethodOptions, "PROPFIND", "REPORT", "DELETE", "MKCOL"}
+		w.Header().Add("DAV", strings.Join(caps, ", "))
+		w.Header().Add("Allow", strings.Join(allow, ", "))
+		w.WriteHeader(http.StatusOK)
+	case "PROPFIND":
+		if err := servePrincipalPropfind(w, r, options); err != nil {
+			internal.ServeError(w, err)
+		}
+	default:
+		http.Error(w, "unsupported method", http.StatusMethodNotAllowed)
+	}
+}
+
+func servePrincipalPropfind(w http.ResponseWriter, r *http.Request, options *ServePrincipalOptions) error {
+	var propfind internal.PropFind
+	if err := internal.DecodeXMLRequest(r, &propfind); err != nil {
+		return err
+	}
+	props := map[xml.Name]internal.PropFindFunc{
+		internal.ResourceTypeName: func(*internal.RawXMLValue) (interface{}, error) {
+			return internal.NewResourceType(principalName), nil
+		},
+		internal.CurrentUserPrincipalName: func(*internal.RawXMLValue) (interface{}, error) {
+			return &internal.CurrentUserPrincipal{Href: internal.Href{Path: options.CurrentUserPrincipalPath}}, nil
+		},
+	}
+
+	// TODO: handle Depth and more properties
+
+	for _, homeSet := range options.HomeSets {
+		hs := homeSet // capture variable for closure
+		props[homeSet.GetXMLName()] = func(*internal.RawXMLValue) (interface{}, error) {
+			return hs, nil
+		}
+	}
+
+	resp, err := internal.NewPropFindResponse(r.URL.Path, &propfind, props)
+	if err != nil {
+		return err
+	}
+
+	ms := internal.NewMultiStatus(*resp)
+	return internal.ServeMultiStatus(w, ms)
+}

webdav.go

@@ -5,8 +5,11 @@ package webdav
 
 import (
 	"time"
+
+	"github.com/emersion/go-webdav/internal"
 )
 
+// FileInfo holds information about a WebDAV file.
 type FileInfo struct {
 	Path     string
 	Size     int64
@@ -15,3 +18,46 @@ type FileInfo struct {
 	MIMEType string
 	ETag     string
 }
+
+type CreateOptions struct {
+	IfMatch     ConditionalMatch
+	IfNoneMatch ConditionalMatch
+}
+
+type CopyOptions struct {
+	NoRecursive bool
+	NoOverwrite bool
+}
+
+type MoveOptions struct {
+	NoOverwrite bool
+}
+
+// ConditionalMatch represents the value of a conditional header
+// according to RFC 2068 section 14.25 and RFC 2068 section 14.26
+// The (optional) value can either be a wildcard or an ETag.
+type ConditionalMatch string
+
+func (val ConditionalMatch) IsSet() bool {
+	return val != ""
+}
+
+func (val ConditionalMatch) IsWildcard() bool {
+	return val == "*"
+}
+
+func (val ConditionalMatch) ETag() (string, error) {
+	var e internal.ETag
+	if err := e.UnmarshalText([]byte(val)); err != nil {
+		return "", err
+	}
+	return string(e), nil
+}
+
+func (val ConditionalMatch) MatchETag(etag string) (bool, error) {
+	if val.IsWildcard() {
+		return true, nil
+	}
+	t, err := val.ETag()
+	return t == etag, err
+}