feat: add udiff cmd package

Run uDiff as a standalone binary

cmd/go.mod

@@ -0,0 +1,11 @@
+module github.com/aymanbagabas/go-udiff/cmd
+
+go 1.18
+
+require (
+	github.com/aymanbagabas/go-udiff v0.2.0
+	github.com/mattn/go-isatty v0.0.20
+	github.com/spf13/pflag v1.0.5
+)
+
+require golang.org/x/sys v0.6.0 // indirect

cmd/go.sum

@@ -0,0 +1,8 @@
+github.com/aymanbagabas/go-udiff v0.2.0 h1:TK0fH4MteXUDspT88n8CKzvK0X9O2xu9yQjWpi6yML8=
+github.com/aymanbagabas/go-udiff v0.2.0/go.mod h1:RE4Ex0qsGkTAJoQdQQCA0uG+nAzJO/pI/QwceO5fgrA=
+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/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+golang.org/x/sys v0.6.0 h1:MVltZSvRTcU2ljQOhs94SXPftV6DCNnZViHeQps87pQ=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

cmd/udiff/main.go

@@ -0,0 +1,155 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/aymanbagabas/go-udiff"
+	"github.com/mattn/go-isatty"
+	"github.com/spf13/pflag"
+)
+
+const (
+	redSeq   = "\033[31m"
+	greenSeq = "\033[32m"
+	resetSeq = "\033[0m"
+)
+
+var (
+	contextLines int
+	color        string
+)
+
+func init() {
+	pflag.Usage = usage
+	pflag.IntVarP(&contextLines, "context", "C", udiff.DefaultContextLines, "number of context lines")
+	pflag.StringVarP(&color, "color", "", "auto", "colorize the output; can be 'always', 'never', or 'auto'")
+}
+
+func usage() {
+	fmt.Fprintf(os.Stderr, "Usage: %s [options] file1 file2\n", os.Args[0])
+	pflag.PrintDefaults()
+}
+
+func main() {
+	pflag.Parse()
+	args := pflag.Args()
+	if len(args) != 2 {
+		pflag.Usage()
+		os.Exit(1)
+	}
+
+	var colorize bool
+	switch strings.ToLower(color) {
+	case "always":
+		colorize = true
+	case "auto":
+		colorize = isatty.IsTerminal(os.Stdout.Fd())
+	}
+
+	f1, err := os.Open(args[0])
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "couldn't open file: %s\n", err)
+		os.Exit(1)
+	}
+
+	defer f1.Close()
+	f2, err := os.Open(args[1])
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "couldn't open file: %s\n", err)
+		os.Exit(1)
+	}
+
+	defer f2.Close()
+	s1, err := io.ReadAll(f1)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "couldn't read file: %s\n", err)
+		os.Exit(1)
+	}
+
+	s2, err := io.ReadAll(f2)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "couldn't read file: %s\n", err)
+		os.Exit(1)
+	}
+
+	edits := udiff.Strings(string(s1), string(s2))
+	u, err := udiff.ToUnifiedDiff(f1.Name(), f2.Name(), string(s1), edits, contextLines)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "couldn't generate diff: %s\n", err)
+		os.Exit(1)
+	}
+
+	fmt.Println(toString(u, colorize))
+}
+
+// String converts a unified diff to the standard textual form for that diff.
+// The output of this function can be passed to tools like patch.
+func toString(u udiff.UnifiedDiff, colorize bool) string {
+	if len(u.Hunks) == 0 {
+		return ""
+	}
+	b := new(strings.Builder)
+	fmt.Fprintf(b, "--- %s\n", u.From)
+	fmt.Fprintf(b, "+++ %s\n", u.To)
+	for _, hunk := range u.Hunks {
+		fromCount, toCount := 0, 0
+		for _, l := range hunk.Lines {
+			switch l.Kind {
+			case udiff.Delete:
+				fromCount++
+			case udiff.Insert:
+				toCount++
+			default:
+				fromCount++
+				toCount++
+			}
+		}
+		fmt.Fprint(b, "@@")
+		if fromCount > 1 {
+			fmt.Fprintf(b, " -%d,%d", hunk.FromLine, fromCount)
+		} else if hunk.FromLine == 1 && fromCount == 0 {
+			// Match odd GNU diff -u behavior adding to empty file.
+			fmt.Fprintf(b, " -0,0")
+		} else {
+			fmt.Fprintf(b, " -%d", hunk.FromLine)
+		}
+		if toCount > 1 {
+			fmt.Fprintf(b, " +%d,%d", hunk.ToLine, toCount)
+		} else if hunk.ToLine == 1 && toCount == 0 {
+			// Match odd GNU diff -u behavior adding to empty file.
+			fmt.Fprintf(b, " +0,0")
+		} else {
+			fmt.Fprintf(b, " +%d", hunk.ToLine)
+		}
+		fmt.Fprint(b, " @@\n")
+		for _, l := range hunk.Lines {
+			switch l.Kind {
+			case udiff.Delete:
+				if colorize {
+					fmt.Fprint(b, redSeq)
+				}
+				fmt.Fprintf(b, "-%s", l.Content)
+				if colorize {
+					fmt.Fprint(b, resetSeq)
+				}
+			case udiff.Insert:
+				if colorize {
+					fmt.Fprint(b, greenSeq)
+				}
+				fmt.Fprintf(b, "+%s", l.Content)
+				if colorize {
+					fmt.Fprint(b, resetSeq)
+				}
+			default:
+				fmt.Fprintf(b, " %s", l.Content)
+			}
+			if !strings.HasSuffix(l.Content, "\n") {
+				fmt.Fprintf(b, "\n\\ No newline at end of file\n")
+			}
+		}
+	}
+	return b.String()
+}