package main

import (
	"bytes"
	"encoding/binary"
	"log"
	"os/exec"

	"github.com/kkdai/youtube/v2"
)

const (
	ItagM4AAudio = 140
	SizeOfInt16  = 2
)

// TODO: process as stream to avoid loading full buffer in memory

func main() {
	var client youtube.Client

	videoID := "s_oJYdRlrv0"

	video, err := client.GetVideo(videoID)
	if err != nil {
		log.Fatal(err)
	}

	format := video.Formats.FindByItag(ItagM4AAudio)
	stream, _, err := client.GetStream(video, format)
	if err != nil {
		log.Fatal(err)
	}

	// TODO: force 44.1khz
	cmd := exec.Command("ffmpeg", "-i", "-", "-f", "s16le", "-acodec", "pcm_s16le", "-")
	cmd.Stdin = stream

	var out bytes.Buffer
	cmd.Stdout = &out

	var errOut bytes.Buffer
	cmd.Stderr = &errOut

	if err = cmd.Run(); err != nil {
		log.Fatalf("err = %v, stdErr = %s", err, errOut.String())
	}

	log.Printf("byteLen = %d", out.Len())

	// TODO: reflect.Slice to avoid copying?
	data := make([]uint16, 0, out.Len()/SizeOfInt16)
	for i := 0; i < out.Len(); i += SizeOfInt16 {
		v := binary.LittleEndian.Uint16(out.Bytes()[i : i+SizeOfInt16])
		data = append(data, v)
	}

	log.Printf("intLen = %d", len(data))
	log.Printf("ints = %+v", data[0:8192])
}