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read.go
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read.go
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package git_diff_highlight
import (
"bufio"
"bytes"
"fmt"
"io"
"regexp"
"strings"
"github.com/sergi/go-diff/diffmatchpatch"
)
const (
highlightColor = "\x1b[7m"
resetColor = "\x1b[27m"
colorRule = `\x1b\[[0-9;]*m`
minBufferSize = 512
)
var (
colorBlock = regexp.MustCompile(colorRule)
addedLine = regexp.MustCompile("^(?:" + colorRule + `)*\+`)
removedLine = regexp.MustCompile("^(?:" + colorRule + `)*\-`)
unchangedLine = regexp.MustCompile("^(?:" + colorRule + `)*\s`)
hunkLine = regexp.MustCompile("^(?:" + colorRule + `)*\@\@`)
)
type ttyPrinter struct {
highlightColor, resetColor string
buf *bytes.Buffer
}
func (p *ttyPrinter) Print(s string) {
p.buf.WriteString(s)
}
func (p *ttyPrinter) PrintInsert(s string) {
p.buf.WriteString(p.highlightColor)
p.buf.WriteString(s)
p.buf.WriteString(p.resetColor)
}
func (p *ttyPrinter) PrintDelete(s string) {
p.buf.WriteString(p.highlightColor)
p.buf.WriteString(s)
p.buf.WriteString(p.resetColor)
}
func NewReader(r io.Reader) io.Reader {
return &diffReader{
scanner: bufio.NewScanner(r),
printer: &ttyPrinter{
highlightColor,
resetColor,
new(bytes.Buffer),
},
}
}
type diffReader struct {
buf bytes.Buffer
inhunk bool
printer *ttyPrinter
scanner *bufio.Scanner
err error
}
func (r *diffReader) Size() int {
return r.printer.buf.Len()
}
// Read implement io.Reader interface.
func (r *diffReader) Read(p []byte) (n int, err error) {
for r.Size() < minBufferSize && r.scanner.Scan() {
r.hanldeLine(r.scanner.Text())
}
n, err = r.printer.buf.Read(p)
if err == io.EOF && r.buf.Len() > 0 {
r.dumpBuffer()
return r.printer.buf.Read(p)
}
return
}
func (r *diffReader) hanldeLine(s string) {
if !r.inhunk {
if hunkLine.MatchString(s) {
r.inhunk = true
}
r.printer.Print(s + "\n")
return
}
if addedLine.MatchString(s) || removedLine.MatchString(s) {
r.buf.WriteString(s)
r.buf.WriteString("\n")
return
}
if !unchangedLine.MatchString(s) && !hunkLine.MatchString(s) {
r.inhunk = false
}
if r.buf.Len() > 0 {
r.dumpBuffer()
}
r.printer.Print(s + "\n")
}
type diffPair struct {
inserted, deleted bytes.Buffer
}
func (p *diffPair) oneSideEmpty() bool {
return p.inserted.Len() == 0 || p.deleted.Len() == 0
}
func splitDiff(diff diffmatchpatch.Diff) (diffs []diffmatchpatch.Diff) {
diff.Text = strings.TrimSpace(diff.Text)
if !strings.Contains(diff.Text, "\n") {
diffs = append(diffs, diff)
return
}
text := diff.Text
for text != "" {
i := strings.Index(text, "\n")
d := diffmatchpatch.Diff{
Type: diff.Type,
}
if i == -1 {
d.Text = strings.TrimSpace(text)
diffs = append(diffs, d)
return
}
d.Text = strings.TrimSpace(text[:i])
newline := d
newline.Text = "\n"
diffs = append(diffs, d, newline)
text = text[i+1:]
}
return
}
func (p *diffPair) diffs() []diffmatchpatch.Diff {
diffs := diffmatchpatch.New().DiffMain(p.deleted.String(),
p.inserted.String(), false)
var safeDiffs []diffmatchpatch.Diff
for _, diff := range diffs {
diffs := splitDiff(diff)
safeDiffs = append(safeDiffs, diffs...)
}
return safeDiffs
}
func getPair(b []byte) *diffPair {
// sanitize color
b = colorBlock.ReplaceAll(b, []byte(""))
scanner := bufio.NewScanner(bytes.NewReader(b))
var pair diffPair
for scanner.Scan() {
t := scanner.Text()
if strings.HasPrefix(t, "-") {
pair.deleted.WriteString(t[1:])
pair.deleted.WriteString("\n")
} else if strings.HasPrefix(t, "+") {
pair.inserted.WriteString(t[1:])
pair.inserted.WriteString("\n")
} else {
panic("Unexpected input: " + t)
}
}
return &pair
}
func (r *diffReader) dumpBuffer() {
pair := getPair(r.buf.Bytes())
defer r.buf.Reset()
// If one side is empty, then there is nothing to compare or highlight
if pair.oneSideEmpty() {
r.printer.Print(r.buf.String())
r.printer.Print("\n")
return
}
diffs := pair.diffs()
s := r.buf.String()
it := &diffIterator{
diffs: diffs,
}
for s != "" {
diff := it.Next()
if diff == nil {
r.printer.Print(s)
s = ""
break
}
i := strings.Index(s, diff.Text)
// TODO don't panic
if i == -1 {
fmt.Printf("text is contains(%b): \"%s\"\n", strings.Contains(s, "\n"), s)
fmt.Printf("buf is: \"%s\"\n", r.buf.String())
panic("unknown string: \"" + diff.Text + "\"")
}
if diff.Type == diffmatchpatch.DiffEqual {
r.printer.Print(s[:i+len(diff.Text)])
s = s[i+len(diff.Text):]
continue
}
if i != 0 {
r.printer.Print(s[:i])
}
if diff.Type == diffmatchpatch.DiffDelete {
r.printer.PrintDelete(diff.Text)
} else {
r.printer.PrintInsert(diff.Text)
}
s = s[i+len(diff.Text):]
}
}
type diffIterator struct {
i int
flipped bool
diffs []diffmatchpatch.Diff
}
func (it *diffIterator) Next() *diffmatchpatch.Diff {
diff := it.next()
if diff == nil && !it.flipped {
it.flipped = true
it.i = 0
return it.next()
}
return diff
}
func (it *diffIterator) next() *diffmatchpatch.Diff {
skipType := it.skipType()
for it.i < len(it.diffs) {
if it.diffs[it.i].Type == skipType {
it.i++
continue
}
i := it.i
it.i++
return &it.diffs[i]
}
return nil
}
func (it *diffIterator) skipType() diffmatchpatch.Operation {
if it.flipped {
return diffmatchpatch.DiffDelete
}
return diffmatchpatch.DiffInsert
}