package main

import (
	"crypto/md5"
	"encoding/hex"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"os"
	"os/exec"
	"strconv"
	"strings"
)

var tempDir *string
var ffmpeg = "ffmpeg"

func main() {
	b := flag.String("b", ":8080", "Server Bind Address")
	tempDir = flag.String("temp", os.TempDir(), "")
	flag.Parse()

	if _, err := exec.LookPath(ffmpeg); err != nil {
		fmt.Printf("Error Can't Find %s Client...", ffmpeg)
		return
	}

	http.HandleFunc("/", func(resp http.ResponseWriter, req *http.Request) {
		if strings.HasPrefix(req.RequestURI, "/amr2mp3") {
			amr2mp3(resp, req)
			return
		}
		api(resp, req)
	})

	http.ListenAndServe(*b, nil)
	fmt.Printf("FFmpeg WebInterface Listen on %s ...\n", *b)
}

func api(w http.ResponseWriter, r *http.Request) {
	handleInternal(w, r, r.FormValue("o"), r.FormValue("t"))
}

func amr2mp3(w http.ResponseWriter, r *http.Request) {
	handleInternal(w, r, "amr", "mp3")
}

func handleInternal(w http.ResponseWriter, r *http.Request, origin, target string) {
	// Read Byte From File Or URL
	bytes, err := readBytesFromRequest(r)
	if err != nil {
		w.Write([]byte("Error Read Bytes: " + err.Error()))
		return
	}
	// Convert origin to target
	out, err := convert(bytes, origin, target)
	if err != nil {
		w.Write([]byte("Error Handler: " + err.Error()))
		return
	}
	w.Write(out)
}

func convert(in []byte, origin, target string) (out []byte, err error) {
	source := *tempDir + "/" + fmt.Sprintf("ffmpeg-webapi-%s-%s", MD5(in), strconv.Itoa(len(in)))

	amr := source + "." + origin
	ioutil.WriteFile(amr, in, os.ModeAppend)
	defer os.Remove(amr)

	mp3 := source + "." + target
	err = exec.Command(ffmpeg, "-i", amr, mp3).Run()
	defer os.Remove(mp3)

	if err != nil {
		// Ignore Error Bucause ffmpeg will return not zero when amr to mp3
	}
	// check target file is exist if not maybe exec error
	if _, err := exec.LookPath(mp3); err == nil {
		return nil, err
	}

	return ioutil.ReadFile(mp3)
}

func readBytesFromRequest(r *http.Request) (out []byte, err error) {
	var reader io.Reader
	url := r.FormValue("url")
	if url != "" {
		fmt.Printf("[A2M] url request " + url + "\n")
		var resp *http.Response
		resp, err = http.Get(url)
		if err != nil {
			return nil, err
		}
		reader = resp.Body
	} else {
		fmt.Printf("[A2M] file request\n")
		reader, _, err = r.FormFile("file")
		if err != nil {
			return nil, err
		}
	}
	return ioutil.ReadAll(reader)
}

// MD5 生成32位MD5
func MD5(bytes []byte) string {
	ctx := md5.New()
	ctx.Write(bytes)
	return hex.EncodeToString(ctx.Sum(nil))
}