Refactor entire hosts reading and writing code

go.mod

@@ -2,4 +2,13 @@ module golang.captainalm.com/HostPersister
 
 go 1.18
 
-require github.com/joho/godotenv v1.5.1
+require (
+	github.com/joho/godotenv v1.5.1
+	github.com/stretchr/testify v1.8.4
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -1,2 +1,12 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
 github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

hosts/Entry.go

@@ -1,76 +0,0 @@
-package hosts
-
-import "strings"
-
-func NewHostsEntry(lineIn string) Entry {
-	trLineIn := strings.ReplaceAll(strings.Trim(lineIn, "\r\n"), "	", " ")
-	lineSplt := strings.Split(trLineIn, " ")
-	if strings.HasPrefix(strings.TrimPrefix(trLineIn, " "), "#") {
-		return Entry{
-			IPAddress: "",
-			Domains:   nil,
-			comment:   trLineIn,
-		}
-	} else if len(lineSplt) > 1 {
-		var theDomains []string
-		for i := 1; i < len(lineSplt); i++ {
-			if lineSplt[i] == "" {
-				continue
-			}
-			if strings.HasPrefix(lineSplt[i], "#") {
-				break
-			}
-			theDomains = append(theDomains, lineSplt[i])
-		}
-		theComment := ""
-		theCommentStart := strings.Index(trLineIn, "#")
-		if theCommentStart > -1 {
-			theComment = trLineIn[theCommentStart:]
-		}
-		return Entry{
-			IPAddress: lineSplt[0],
-			Domains:   theDomains,
-			comment:   theComment,
-		}
-	} else {
-		return Entry{
-			IPAddress: "",
-			Domains:   nil,
-			comment:   "",
-		}
-	}
-}
-
-type Entry struct {
-	IPAddress string
-	Domains   []string
-	comment   string
-}
-
-func (e Entry) IsFilled() bool {
-	return e.IPAddress != "" && len(e.Domains) > 0
-}
-
-func (e Entry) HasDomain(domain string) bool {
-	if !e.IsFilled() {
-		return false
-	}
-	for _, c := range e.Domains {
-		if strings.EqualFold(c, domain) {
-			return true
-		}
-	}
-	return false
-}
-
-func (e Entry) ToLine() string {
-	if e.IsFilled() {
-		toReturn := []string{e.IPAddress}
-		toReturn = append(toReturn, e.Domains...)
-		if e.comment != "" {
-			toReturn = append(toReturn, e.comment)
-		}
-		return strings.Join(toReturn, " ")
-	}
-	return e.comment
-}

hosts/File.go

@@ -1,122 +0,0 @@
-package hosts
-
-import (
-	"io"
-	"os"
-	"strings"
-)
-
-const readBufferSize = 8192
-
-func NewHostsFile(filePath string) (*File, error) {
-	theHostFile := &File{
-		filePath: filePath,
-	}
-	err := theHostFile.ReadHostsFile()
-	if err == nil {
-		return theHostFile, nil
-	}
-	return nil, err
-}
-
-type File struct {
-	filePath   string
-	Entries    []Entry
-	lineEnding string
-}
-
-func (f *File) ReadHostsFile() error {
-	f.Entries = nil
-	theFile, err := os.Open(f.filePath)
-	if err != nil {
-		return err
-	}
-	defer theFile.Close()
-	var lenIn int
-	f.lineEnding = ""
-	theCBuffer := ""
-	theBuffer := make([]byte, readBufferSize)
-	for err == nil {
-		lenIn, err = theFile.Read(theBuffer)
-		if lenIn > 0 {
-			theCBuffer += string(theBuffer[:lenIn])
-			if f.lineEnding == "" {
-				if strings.Contains(theCBuffer, "\r\n") {
-					f.lineEnding = "\r\n"
-				} else if strings.Contains(theCBuffer, "\r") {
-					f.lineEnding = "\r"
-				} else if strings.Contains(theCBuffer, "\n") {
-					f.lineEnding = "\n"
-				}
-			}
-			if f.lineEnding == "\r\n" {
-				strings.ReplaceAll(theCBuffer, "\r\n", "\n")
-			} else if f.lineEnding == "\r" {
-				strings.ReplaceAll(theCBuffer, "\r", "\n")
-			}
-			splt := strings.Split(theCBuffer, "\n")
-			for i := 0; i < len(splt)-1; i++ {
-				f.Entries = append(f.Entries, NewHostsEntry(splt[i]))
-			}
-			theCBuffer = splt[len(splt)-1]
-		}
-	}
-	if err != io.EOF {
-		return err
-	}
-	if theCBuffer != "" {
-		f.Entries = append(f.Entries, NewHostsEntry(theCBuffer))
-	}
-	return nil
-}
-
-func (f File) WriteHostsFile() error {
-	theFile, err := os.OpenFile(f.filePath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
-	if err != nil {
-		return err
-	}
-	defer theFile.Close()
-	for _, entry := range f.Entries {
-		_, err = theFile.WriteString(entry.ToLine() + f.lineEnding)
-		if err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-func (f File) HasDomain(domain string) bool {
-	for _, entry := range f.Entries {
-		if entry.HasDomain(domain) {
-			return true
-		}
-	}
-	return false
-}
-
-func (f File) indexDomainSingleton(domain string) int {
-	for i, entry := range f.Entries {
-		if len(entry.Domains) == 1 && entry.HasDomain(domain) {
-			return i
-		}
-	}
-	return -1
-}
-
-func (f File) HasDomainSingleton(domain string) bool {
-	return f.indexDomainSingleton(domain) > -1
-}
-
-func (f *File) OverwriteDomainSingleton(domain string, ipAddress string) {
-	idx := f.indexDomainSingleton(domain)
-	if idx == -1 {
-		f.Entries = append(f.Entries, Entry{
-			IPAddress: ipAddress,
-			Domains:   []string{domain},
-		})
-	} else {
-		theEntry := f.Entries[idx]
-		theEntry.IPAddress = ipAddress
-		f.Entries = append(append(f.Entries[:idx], theEntry), f.Entries[idx+1:]...)
-	}
-}

hosts/comment-reader.go

@@ -0,0 +1,40 @@
+package hosts
+
+import (
+	"bytes"
+	"io"
+)
+
+type CommentReader struct {
+	r    io.Reader
+	over []byte
+	mark byte
+	hit  bool
+}
+
+var _ io.Reader = &CommentReader{}
+
+func NewCommentReader(r io.Reader, mark byte) *CommentReader {
+	return &CommentReader{r, nil, mark, false}
+}
+
+func (c *CommentReader) Read(p []byte) (n int, err error) {
+	if c.hit {
+		return 0, io.EOF
+	}
+	n, err = c.r.Read(p)
+	if err != nil {
+		return
+	}
+	n2 := bytes.IndexByte(p[:n], c.mark)
+	if n2 != -1 {
+		c.over = p[n2:n]
+		n = n2
+		err = io.EOF
+	}
+	return
+}
+
+func (c *CommentReader) Comment() io.Reader {
+	return io.MultiReader(bytes.NewReader(c.over), c.r)
+}

hosts/comment-reader_test.go

@@ -0,0 +1,49 @@
+package hosts
+
+import (
+	"github.com/stretchr/testify/assert"
+	"io"
+	"strings"
+	"testing"
+)
+
+func TestNewCommentReader(t *testing.T) {
+	t.Run("normal", func(t *testing.T) {
+		r := NewCommentReader(strings.NewReader("Hello world! # this is a comment"), '#')
+		all, err := io.ReadAll(r)
+		assert.NoError(t, err)
+		assert.Equal(t, "Hello world! ", string(all))
+		all, err = io.ReadAll(r.Comment())
+		assert.NoError(t, err)
+		assert.Equal(t, "# this is a comment", string(all))
+	})
+	t.Run("overflow start", func(t *testing.T) {
+		r := NewCommentReader(strings.NewReader(strings.Repeat("Hello world!", 2048)+" # this is a comment"), '#')
+		all, err := io.ReadAll(r)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.Repeat("Hello world!", 2048)+" ", string(all))
+		all, err = io.ReadAll(r.Comment())
+		assert.NoError(t, err)
+		assert.Equal(t, "# this is a comment", string(all))
+	})
+	t.Run("overflow comment", func(t *testing.T) {
+		r := NewCommentReader(strings.NewReader(strings.Repeat("Hello world!", 2048)+" # "+strings.Repeat("this is a comment", 2048)), '#')
+		all, err := io.ReadAll(r)
+		assert.NoError(t, err)
+		assert.Equal(t, strings.Repeat("Hello world!", 2048)+" ", string(all))
+		all, err = io.ReadAll(r.Comment())
+		assert.NoError(t, err)
+		assert.Equal(t, "# "+strings.Repeat("this is a comment", 2048), string(all))
+	})
+}
+
+func FuzzCommentReader(f *testing.F) {
+	f.Fuzz(func(t *testing.T, a string) {
+		r := NewCommentReader(strings.NewReader(a), '#')
+		b1, err := io.ReadAll(r)
+		assert.NoError(t, err)
+		b2, err := io.ReadAll(r.Comment())
+		assert.NoError(t, err)
+		assert.Equal(t, string(b1)+string(b2), a)
+	})
+}

hosts/entry.go

@@ -0,0 +1,90 @@
+package hosts
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"strings"
+)
+
+var ErrInvalidEntry = errors.New("invalid entry")
+
+type Entry struct {
+	IPAddress string
+	Domains   []string
+	Comment   string
+}
+
+func (e Entry) IsFilled() bool {
+	return e.IPAddress != "" && len(e.Domains) > 0
+}
+
+func (e Entry) HasDomain(domain string) bool {
+	if !e.IsFilled() {
+		return false
+	}
+	for _, c := range e.Domains {
+		if strings.EqualFold(c, domain) {
+			return true
+		}
+	}
+	return false
+}
+
+func (e Entry) ToLine() string {
+	var b strings.Builder
+	filled := e.IsFilled()
+	if filled {
+		b.WriteString(e.IPAddress)
+		for _, i := range e.Domains {
+			b.WriteByte(' ')
+			b.WriteString(i)
+		}
+	}
+	if e.Comment != "" {
+		b.Grow(len(e.Comment) + 2)
+		if filled {
+			b.WriteByte(' ')
+		}
+		b.WriteByte('#')
+		b.WriteString(e.Comment)
+	}
+	return b.String()
+}
+
+func ParseEntryString(line string) (Entry, error) {
+	return ParseEntry(strings.NewReader(line))
+}
+
+func ParseEntry(line io.Reader) (entry Entry, err error) {
+	cr := NewCommentReader(line, '#')
+	sc := bufio.NewScanner(cr)
+	sc.Split(bufio.ScanWords)
+
+	isFirst := true
+	for sc.Scan() {
+		t := sc.Text()
+		if isFirst {
+			entry.IPAddress = t
+			isFirst = false
+		} else {
+			entry.Domains = append(entry.Domains, t)
+		}
+	}
+	err = sc.Err()
+	if err != nil {
+		return
+	}
+
+	// invalid if the ip address is set but no domains are added
+	if entry.IPAddress != "" && len(entry.Domains) < 1 {
+		err = ErrInvalidEntry
+		return
+	}
+	var cAll []byte
+	cAll, err = io.ReadAll(cr.Comment())
+	if len(cAll) >= 1 {
+		entry.Comment = string(cAll[1:])
+	}
+	return
+}

hosts/entry_test.go

@@ -0,0 +1,72 @@
+package hosts
+
+import (
+	"github.com/stretchr/testify/assert"
+	"strings"
+	"testing"
+	"unicode"
+)
+
+func TestParseEntry(t *testing.T) {
+	entry, err := ParseEntry(strings.NewReader("127.0.0.1 myself.local another.local # this is a test comment"))
+	assert.NoError(t, err)
+	assert.Equal(t, Entry{
+		IPAddress: "127.0.0.1",
+		Domains:   []string{"myself.local", "another.local"},
+		Comment:   " this is a test comment",
+	}, entry)
+
+	entry, err = ParseEntry(strings.NewReader("127.0.0.1 test.local #another comment"))
+	assert.NoError(t, err)
+	assert.Equal(t, Entry{
+		IPAddress: "127.0.0.1",
+		Domains:   []string{"test.local"},
+		Comment:   "another comment",
+	}, entry)
+
+	entry, err = ParseEntry(strings.NewReader("127.0.0.1     "))
+	assert.EqualError(t, err, "invalid entry")
+}
+
+func TestEntry_IsFilled(t *testing.T) {
+	assert.True(t, Entry{IPAddress: "127.0.0.1", Domains: []string{"myself.local"}}.IsFilled())
+	assert.False(t, Entry{}.IsFilled())
+	assert.False(t, Entry{IPAddress: "127.0.0.1"}.IsFilled())
+}
+
+func TestEntry_HasDomain(t *testing.T) {
+	assert.True(t, Entry{IPAddress: "127.0.0.1", Domains: []string{"myself.local", "another.local"}}.HasDomain("myself.local"))
+	assert.True(t, Entry{IPAddress: "127.0.0.1", Domains: []string{"myself.local", "another.local"}}.HasDomain("MYSELF.local"))
+	assert.False(t, Entry{IPAddress: "127.0.0.1", Domains: []string{"notme.local", "another.local"}}.HasDomain("myself.local"))
+}
+
+func TestEntry_ToLine(t *testing.T) {
+	assert.Equal(t, "127.0.0.1 myself.local another.local # this is a test comment", Entry{IPAddress: "127.0.0.1", Domains: []string{"myself.local", "another.local"}, Comment: " this is a test comment"}.ToLine())
+	assert.Equal(t, "# this is a test comment", Entry{IPAddress: "", Domains: nil, Comment: " this is a test comment"}.ToLine())
+	assert.Equal(t, "127.0.0.1 myself.local another.local", Entry{IPAddress: "127.0.0.1", Domains: []string{"myself.local", "another.local"}}.ToLine())
+}
+
+func FuzzParseEntry(f *testing.F) {
+	f.Add("127.0.0.1", "myself.local", "another.local", "this is a test comment")
+	f.Fuzz(func(t *testing.T, a, b, c, d string) {
+		for _, i := range []string{a, b, c} {
+			i = strings.TrimSpace(i)
+			if i == "" || strings.ContainsFunc(i, func(r rune) bool {
+				return r == '#' || unicode.IsSpace(r)
+			}) {
+				t.Skip()
+			}
+		}
+
+		entry := Entry{IPAddress: a, Domains: []string{b, c}, Comment: d}
+		e2, err := ParseEntryString(entry.ToLine())
+		if err != nil {
+			t.Error(err)
+		}
+		assert.Equal(t, Entry{
+			IPAddress: strings.TrimSpace(a),
+			Domains:   []string{strings.TrimSpace(b), strings.TrimSpace(c)},
+			Comment:   d,
+		}, e2)
+	})
+}

hosts/file.go

@@ -0,0 +1,97 @@
+package hosts
+
+import (
+	"bufio"
+	"os"
+)
+
+func NewHostsFile(filePath string) (*File, error) {
+	theHostFile := &File{filePath: filePath}
+	err := theHostFile.ReadHostsFile()
+	if err == nil {
+		return theHostFile, nil
+	}
+	return nil, err
+}
+
+type File struct {
+	filePath string
+	Entries  []Entry
+	LF       string
+}
+
+func (f *File) ReadHostsFile() error {
+	f.Entries = nil
+	theFile, err := os.Open(f.filePath)
+	if err != nil {
+		return err
+	}
+	defer theFile.Close()
+
+	sc := bufio.NewScanner(theFile)
+	sc.Split(bufio.ScanLines)
+	for sc.Scan() {
+		t := sc.Text()
+		entry, err := ParseEntryString(t)
+		if err != nil {
+			return err
+		}
+		f.Entries = append(f.Entries, entry)
+	}
+	return sc.Err()
+}
+
+func (f *File) WriteHostsFile() error {
+	// default LF to \n
+	if f.LF == "" {
+		f.LF = "\n"
+	}
+	theFile, err := os.OpenFile(f.filePath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
+	if err != nil {
+		return err
+	}
+	defer theFile.Close()
+	for _, entry := range f.Entries {
+		_, err = theFile.WriteString(entry.ToLine() + f.LF)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (f *File) HasDomain(domain string) bool {
+	for _, entry := range f.Entries {
+		if entry.HasDomain(domain) {
+			return true
+		}
+	}
+	return false
+}
+
+func (f *File) indexDomainSingleton(domain string) int {
+	for i, entry := range f.Entries {
+		if len(entry.Domains) == 1 && entry.HasDomain(domain) {
+			return i
+		}
+	}
+	return -1
+}
+
+func (f *File) HasDomainSingleton(domain string) bool {
+	return f.indexDomainSingleton(domain) > -1
+}
+
+func (f *File) OverwriteDomainSingleton(domain string, ipAddress string) {
+	idx := f.indexDomainSingleton(domain)
+	if idx == -1 {
+		f.Entries = append(f.Entries, Entry{
+			IPAddress: ipAddress,
+			Domains:   []string{domain},
+		})
+	} else {
+		theEntry := f.Entries[idx]
+		theEntry.IPAddress = ipAddress
+		f.Entries = append(append(f.Entries[:idx], theEntry), f.Entries[idx+1:]...)
+	}
+}