docs: add new example to chomp for parsing a git diff (#62)

README.md

@@ -51,6 +51,7 @@ The true power of `chomp` comes from the ability to build parsers by chaining (_
 Take a look at one of the examples of how to write a parser combinator.
 
 1. [GPG Private Key parser](https://github.com/purpleclay/chomp/blob/main/examples/gpg/main.go)
+1. [Git Diff parser](https://github.com/purpleclay/chomp/blob/main/examples/git-diff/main.go)
 
 ## Why use Chomp?
 

examples/git-diff/main.go

@@ -0,0 +1,261 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+	"strings"
+
+	"github.com/charmbracelet/lipgloss"
+	"github.com/purpleclay/chomp"
+)
+
+const (
+	// git diff header delimiter > @@ ... @@
+	hdrDelim = "@@"
+	// prefix for lines added
+	addPrefix = "+"
+	// prefix for lines removed
+	remPrefix = "-"
+)
+
+var (
+	red   = lipgloss.NewStyle().Foreground(lipgloss.Color("#b34139"))
+	green = lipgloss.NewStyle().Foreground(lipgloss.Color("#29b337"))
+)
+
+type FileDiff struct {
+	Path   string
+	Chunks []DiffChunk
+}
+
+func (d FileDiff) String() string {
+	var buf strings.Builder
+	buf.WriteString(fmt.Sprintf("path: %s\n", d.Path))
+	for _, chunk := range d.Chunks {
+		buf.WriteString(chunk.String())
+	}
+
+	return buf.String()
+}
+
+type DiffChunk struct {
+	Added   DiffChange
+	Removed DiffChange
+}
+
+func (d DiffChunk) String() string {
+	var buf strings.Builder
+
+	buf.WriteString("(")
+	buf.WriteString(red.Render("-"))
+	buf.WriteString(fmt.Sprintf("%d,%d ", d.Removed.LineNo, d.Removed.Count))
+	buf.WriteString(green.Render("+"))
+	buf.WriteString(fmt.Sprintf("%d,%d", d.Added.LineNo, d.Added.Count))
+	buf.WriteString(")\n")
+
+	if d.Removed.Change != "" {
+		buf.WriteString(red.Render(d.Removed.Change))
+		buf.WriteString("\n")
+	}
+
+	if d.Added.Change != "" {
+		buf.WriteString(green.Render(d.Added.Change))
+		buf.WriteString("\n")
+	}
+
+	return buf.String()
+}
+
+type DiffChange struct {
+	LineNo int
+	Count  int
+	Change string
+}
+
+func Parse(in string) (FileDiff, error) {
+	rem, path, err := diffPath()(in)
+	if err != nil {
+		return FileDiff{}, err
+	}
+
+	rem, _, err = chomp.Until(hdrDelim)(rem)
+	if err != nil {
+		return FileDiff{}, err
+	}
+
+	chunks, err := diffChunks(rem)
+	if err != nil {
+		return FileDiff{}, err
+	}
+
+	return FileDiff{
+		Path:   path,
+		Chunks: chunks,
+	}, nil
+}
+
+func diffPath() chomp.Combinator[string] {
+	return func(s string) (string, string, error) {
+		// diff --git a/scan/scanner.go b/scan/scanner.go
+		var rem string
+		var err error
+
+		if rem, _, err = chomp.Tag("diff --git ")(s); err != nil {
+			return rem, "", err
+		}
+
+		var path string
+		if rem, path, err = chomp.Until(" ")(rem); err != nil {
+			return rem, "", err
+		}
+		path = path[strings.Index(path, "/")+1:]
+
+		rem, _, err = chomp.Eol()(rem)
+		return rem, path, err
+	}
+}
+
+func diffChunks(in string) ([]DiffChunk, error) {
+	_, chunks, err := chomp.Map(chomp.Many(diffChunk()),
+		func(in []string) []DiffChunk {
+			var diffChunks []DiffChunk
+
+			for i := 0; i+5 < len(in); i += 6 {
+				// 0: removed line
+				// 1: removed count
+				// 2: added line
+				// 3: added count
+				// 4: removed lines
+				// 5: added lines
+				chunk := DiffChunk{
+					Removed: DiffChange{
+						LineNo: mustInt(in[i]),
+						Count:  mustInt(in[i+1]),
+						Change: in[i+4],
+					},
+					Added: DiffChange{
+						LineNo: mustInt(in[i+2]),
+						Count:  mustInt(in[i+3]),
+						Change: in[i+5],
+					},
+				}
+
+				diffChunks = append(diffChunks, chunk)
+			}
+
+			return diffChunks
+		},
+	)(in)
+
+	return chunks, err
+}
+
+func mustInt(in string) int {
+	out, _ := strconv.Atoi(in)
+	return out
+}
+
+func diffChunk() chomp.Combinator[[]string] {
+	return func(s string) (string, []string, error) {
+		/*
+			@@ -25 +3,3 @@ package scan
+			-import "bytes"
+			+import (
+			+       "bytes"
+			+)
+		*/
+		var rem string
+		var err error
+
+		var changes []string
+		rem, changes, err = chomp.Delimited(
+			chomp.Tag(hdrDelim+" "),
+			chomp.SepPair(diffChunkHeaderChange(remPrefix), chomp.Tag(" "), diffChunkHeaderChange(addPrefix)),
+			chomp.Eol(),
+		)(s)
+		if err != nil {
+			return rem, nil, err
+		}
+
+		var removed string
+		rem, removed, err = chomp.Map(
+			chomp.ManyN(chomp.Prefixed(chomp.Eol(), chomp.Tag(remPrefix)), 0),
+			func(in []string) string { return strings.Join(in, "\n") },
+		)(rem)
+		if err != nil {
+			return rem, nil, err
+		}
+
+		var added string
+		rem, added, err = chomp.Map(
+			chomp.ManyN(chomp.Prefixed(chomp.Eol(), chomp.Tag(addPrefix)), 0),
+			func(in []string) string { return strings.Join(in, "\n") },
+		)(rem)
+		if err != nil {
+			return rem, nil, err
+		}
+
+		return rem, append(changes, removed, added), nil
+	}
+}
+
+func diffChunkHeaderChange(prefix string) chomp.Combinator[[]string] {
+	return func(s string) (string, []string, error) {
+		rem, _, err := chomp.Tag(prefix)(s)
+		if err != nil {
+			return rem, nil, err
+		}
+
+		return chomp.All(
+			chomp.While(chomp.IsDigit),
+			chomp.Opt(chomp.Prefixed(chomp.While(chomp.IsDigit), chomp.Tag(","))),
+		)(rem)
+	}
+}
+
+func main() {
+	// generated by: git diff -U0 -- scan/scanner.go
+	diff := `diff --git a/scan/scanner.go b/scan/scanner.go
+index fdf8e52..02d20e5 100644
+--- a/scan/scanner.go
++++ b/scan/scanner.go
+@@ -25 +3,3 @@ package scan
+-import "bytes"
++import (
++       "bytes"
++)
+@@ -57,0 +38,25 @@ func eat(prefix byte, data []byte) []byte {
++
++// DiffLines is a split function for a [bufio.Scanner] that splits a git diff output
++// into multiple blocks of text, each prefixed by the diff --git marker. Each block
++// of text will be stripped of any leading and trailing whitespace. If the git diff
++// marker isn't detected, the entire block of text is returned, with any leading and
++// trailing whitespace stripped
++func DiffLines() func(data []byte, atEOF bool) (advance int, token []byte, err error) {
++       prefix := []byte("\ndiff --git")
++
++       return func(data []byte, atEOF bool) (advance int, token []byte, err error) {
++               if atEOF && len(data) == 0 {
++                       return 0, nil, nil
++               }
++
++               if i := bytes.Index(data, prefix); i >= 0 {
++                       return i + 1, bytes.TrimSpace(data[:i]), nil
++               }
++
++               if atEOF {
++                       return len(data), bytes.TrimSpace(data), nil
++               }
++
++               return 0, nil, nil
++       }
++}`
+
+	fileDiff, err := Parse(diff)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(fileDiff)
+}

examples/go.mod

@@ -5,17 +5,17 @@ go 1.19
 replace github.com/purpleclay/chomp => ../
 
 require (
-	github.com/charmbracelet/lipgloss v0.9.1
+	github.com/charmbracelet/lipgloss v0.12.1
 	github.com/purpleclay/chomp v0.0.0-20240108065605-b5889a9b1ff2
 )
 
 require (
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
+	github.com/charmbracelet/x/ansi v0.1.4 // indirect
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
-	github.com/mattn/go-isatty v0.0.18 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/mattn/go-runewidth v0.0.15 // indirect
-	github.com/muesli/reflow v0.3.0 // indirect
 	github.com/muesli/termenv v0.15.2 // indirect
-	github.com/rivo/uniseg v0.2.0 // indirect
-	golang.org/x/sys v0.12.0 // indirect
+	github.com/rivo/uniseg v0.4.7 // indirect
+	golang.org/x/sys v0.19.0 // indirect
 )

examples/go.sum

@@ -1,25 +1,24 @@
 github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
-github.com/charmbracelet/lipgloss v0.9.1 h1:PNyd3jvaJbg4jRHKWXnCj1akQm4rh8dbEzN1p/u1KWg=
-github.com/charmbracelet/lipgloss v0.9.1/go.mod h1:1mPmG4cxScwUQALAAnacHaigiiHB9Pmr+v1VEawJl6I=
+github.com/charmbracelet/lipgloss v0.12.1 h1:/gmzszl+pedQpjCOH+wFkZr/N90Snz40J/NR7A0zQcs=
+github.com/charmbracelet/lipgloss v0.12.1/go.mod h1:V2CiwIuhx9S1S1ZlADfOj9HmxeMAORuz5izHb0zGbB8=
+github.com/charmbracelet/x/ansi v0.1.4 h1:IEU3D6+dWwPSgZ6HBH+v6oUuZ/nVawMiWj5831KfiLM=
+github.com/charmbracelet/x/ansi v0.1.4/go.mod h1:dk73KoMTT5AX5BsX0KrqhsTqAnhZZoCBjs7dGWp4Ktw=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=
 github.com/lucasb-eyer/go-colorful v1.2.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
-github.com/mattn/go-isatty v0.0.18 h1:DOKFKCQ7FNG2L1rbrmstDN4QVRdS89Nkh85u68Uwp98=
-github.com/mattn/go-isatty v0.0.18/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
-github.com/mattn/go-runewidth v0.0.12/go.mod h1:RAqKPSqVFrSLVXbA8x7dzmKdmGzieGRCM46jaSJTDAk=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/mattn/go-runewidth v0.0.15 h1:UNAjwbU9l54TA3KzvqLGxwWjHmMgBUVhBiTjelZgg3U=
 github.com/mattn/go-runewidth v0.0.15/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
-github.com/muesli/reflow v0.3.0 h1:IFsN6K9NfGtjeggFP+68I4chLZV2yIKsXJFNZ+eWh6s=
-github.com/muesli/reflow v0.3.0/go.mod h1:pbwTDkVPibjO2kyvBQRBxTWEEGDGq0FlB1BIKtnHY/8=
 github.com/muesli/termenv v0.15.2 h1:GohcuySI0QmI3wN8Ok9PtKGkgkFIk7y6Vpb5PvrY+Wo=
 github.com/muesli/termenv v0.15.2/go.mod h1:Epx+iuz8sNs7mNKhxzH4fWXGNpZwUaJKRS1noLXviQ8=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
-github.com/rivo/uniseg v0.1.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
-github.com/rivo/uniseg v0.2.0 h1:S1pD9weZBuJdFmowNwbpi7BJ8TNftyUImj/0WQi72jY=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
-github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/rivo/uniseg v0.4.7 h1:WUdvkW8uEhrYfLC4ZzdpI2ztxP1I582+49Oc5Mq64VQ=
+github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
-golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.19.0 h1:q5f1RH2jigJ1MoAWp2KTp3gm5zAGFUTarQZ5U386+4o=
+golang.org/x/sys v0.19.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=