From 9d778f4072038db1054a4a359f5230148b62724f Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Mon, 9 Dec 2024 22:31:59 +0100
Subject: [PATCH] webdav: add support for If-Match/If-None-Match in
 FileSystem.Create

---
 fs_local.go | 26 +++++++++++++++++++++-----
 server.go   | 11 +++++++++--
 webdav.go   | 13 +++++++++++++
 3 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/fs_local.go b/fs_local.go
index 65df148..c2cfd46 100644
--- a/fs_local.go
+++ b/fs_local.go
@@ -114,15 +114,31 @@ func (fs LocalFileSystem) ReadDir(ctx context.Context, name string, recursive bo
 	return l, errFromOS(err)
 }
 
-func (fs LocalFileSystem) Create(ctx context.Context, name string, body io.ReadCloser) (*FileInfo, bool, 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, false, err
 	}
-	created := false
-	fi, _ := fs.Stat(ctx, name)
-	if fi == nil {
-		created = true
+	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)
diff --git a/server.go b/server.go
index 3f7ea13..b5ba8f4 100644
--- a/server.go
+++ b/server.go
@@ -17,7 +17,7 @@ type FileSystem interface {
 	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) (fileInfo *FileInfo, created bool, err 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)
@@ -194,7 +194,14 @@ func (b *backend) PropPatch(r *http.Request, update *internal.PropertyUpdate) (*
 }
 
 func (b *backend) Put(w http.ResponseWriter, r *http.Request) error {
-	fi, created, err := b.FileSystem.Create(r.Context(), r.URL.Path, r.Body)
+	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 err
 	}
diff --git a/webdav.go b/webdav.go
index e691ac5..eb5c742 100644
--- a/webdav.go
+++ b/webdav.go
@@ -19,6 +19,11 @@ type FileInfo struct {
 	ETag     string
 }
 
+type CreateOptions struct {
+	IfMatch     ConditionalMatch
+	IfNoneMatch ConditionalMatch
+}
+
 type CopyOptions struct {
 	NoRecursive bool
 	NoOverwrite bool
@@ -48,3 +53,11 @@ func (val ConditionalMatch) ETag() (string, error) {
 	}
 	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
+}