package main

import (
	"bytes"
	"encoding/hex"
	"fmt"
	"github.com/ugorji/go/codec"
	"io/ioutil"
	"os"
	"strings"
)

func usage(retval int) {
	fmt.Printf("%s: converts msgpack data structures to JSON.\n",
		os.Args[0])
	fmt.Printf("usage: %s [input-file]\n", os.Args[0])
	fmt.Printf("\n")
	fmt.Printf("The input file should contain hex digits with no spaces or linebreaks.\n")
	os.Exit(retval)
}

func main() {
	i := 1
	if len(os.Args) < 2 {
		usage(1)
	}
	if (os.Args[i] == "-h") || (os.Args[i] == "--help") {
		usage(0)
	}
	if i >= len(os.Args) {
		usage(1)
	}
	path := os.Args[i]
	buf, err := ioutil.ReadFile(path)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Got error reading from %s: %s\n",
			path, err.Error())
		os.Exit(1)
	}
	str := strings.ToLower(strings.TrimSpace(string(buf)))
	if len(str)%2 != 0 {
		fmt.Fprintf(os.Stderr, "The number of hex digits is not even.\n")
		os.Exit(1)
	}
	var bin []byte
	bin, err = hex.DecodeString(str)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to decode hex string '%s': %s\n",
			str, err.Error())
		os.Exit(1)
	}
	fmt.Fprintf(os.Stdout, "input=\n"+hex.Dump(bin)+"\n")

	// Decode msgpack
	mh := new(codec.MsgpackHandle)
	mh.WriteExt = true
	mh.RawToString = true
	dec := codec.NewDecoderBytes(bin, mh)
	var body interface{}
	err = dec.Decode(&body)

	//fmt.Fprintf(os.Stdout, "body=%v\n", body);

	// Encode JSON
	jh := new(codec.JsonHandle)
	var out bytes.Buffer
	enc := codec.NewEncoder(&out, jh)
	err = enc.Encode(body)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error re-encoding message as JSON: %s\n",
			err.Error())
		os.Exit(1)
	}
	fmt.Fprintf(os.Stdout, "output=\n%s\n", out.String())
	os.Exit(0)
}