package main

import "fmt"
import "crypto/sha256"
import "io"
import "log"
import "os"
import "path/filepath"
import "sync/atomic"

var chan_hash chan string
var running int32

func walk(path string, info os.FileInfo, err error) error {
	if err != nil {
		log.Fatalln(err)
		return err
	}

	if info.IsDir() {
		return nil
	} else {
		atomic.AddInt32(&running, 1)
		go hash(info.Name(), path)
	}
	return nil
}

func hash(name string, path string) {
	h, err := sha256File(path)
	if err != nil {
		log.Fatalln(err)
	}
	chan_hash <- fmt.Sprintf("SHA256 (%s) =  %x", name, h)
}

func sha256File(path string) ([]byte, error) {
	f, err := os.Open(path)
	if err != nil {
		log.Fatalln(err)
		return nil, err
	}
	defer f.Close()
	h := sha256.New()
	io.Copy(h, f)
	return h.Sum(nil), nil
}

func main() {
	if len(os.Args) < 2 {
		log.Fatalln("Usage shadir file")
	}
	chan_hash = make(chan string)
	if err := filepath.Walk(os.Args[1], walk); err != nil {
		panic(err)
	}
	for str := range chan_hash {
		fmt.Println(str)
		atomic.AddInt32(&running, -1)
		if running <= 0 {
			return
		}
	}
}