spaces-to-tabs.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"path/filepath"
)

func replace(s string) string {
	i := 0
	ans := ""
	for i < len(s)-1 {
		if s[i] == ' ' && s[i+1] == ' ' {
			ans += "\t"
			i += 2
		} else {
			break
		}
	}
	ans += s[i:]
	return ans
}

func format(file string) {
	f, err := os.Open(file)
	if err != nil {
		panic(err)
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)

	tfile := file + ".tmp"
	out, err := os.Create(tfile)
	if err != nil {
		panic(err)
	}
	defer out.Close()

	for scanner.Scan() {
		l := scanner.Text()
		rl := replace(l)
		out.Write([]byte(rl + "\n"))
	}

	os.Remove(file)
	os.Rename(tfile, file)
}

func main() {
	if len(os.Args) < 2 {
		panic("Wrong Usage, Expected a Directory Path or a Single File")
	}

	filepath.Walk(os.Args[1], func(path string, info os.FileInfo, err error) error {
		fmt.Println(info.Name())
		if !info.IsDir() {
			format(path)
		}
		return err
	})
}