package main

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

func sha256File(path string) (string, error) {
	f, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer f.Close()
	h := sha256.New()
	io.Copy(h, f)
	return fmt.Sprintf("SHA256 (%s) =  %x", path, h.Sum(nil)), nil
}

func main() {
	if len(os.Args) < 2 {
		log.Fatalln("Usage shadir file")
	}

	var wg sync.WaitGroup
	chan_hash, chan_path := make(chan string), make(chan string)

	for i := 0; i < 100; i++ {
		go func() {
			for path := range chan_path {
				if h, err := sha256File(path); err != nil {
					wg.Done()
					log.Print("Error "+path, err)
				} else {
					chan_hash <- h
				}
			}
		}()
	}

	go func() {
		for h := range chan_hash {
			fmt.Println(h)
			wg.Done()
		}
	}()

	err := filepath.Walk(os.Args[1], func(path string, info os.FileInfo, err error) error {
		if err == nil && !info.IsDir() {
			wg.Add(1)
			chan_path <- path
		}
		return err
	})
	if err != nil {
		log.Fatalln(err)
	}
	wg.Wait()
}