package main

import (
	"encoding/hex"
	"flag"
	"fmt"
	"io"
	"os"

	"github.com/zeebo/blake3"
)

var (
	help = flag.Bool("h", false, "Prints help information")
	length = flag.Int("l", 32,  "The number of output bytes, prior to hex encoding (default 32)")
)

func main() {
	flag.Parse()
	if *help || len(flag.Args()) == 0 {
		flag.Usage()
		os.Exit(0)
	}
	buf := [65536]byte{}
	for _, name := range flag.Args() {
		file, err := os.Open(name)
		if err != nil {
			panic(err)
		}
		hasher := blake3.NewSized(*length)
		for {
			n, err := file.Read(buf[:])
			hasher.Write(buf[:n])
			if err == io.EOF {
				break
			} else if err != nil {
				panic(err)
			}
		}
		file.Close()
		hash := hasher.Sum([]byte{})
		fmt.Print(hex.EncodeToString(hash))
		fmt.Print("  ")
		fmt.Println(name)
	}
}