package main

import (
	"bytes"
	"fmt"
	"git.wanpinghui.com/WPH/go_common/wph"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"strings"
)

func main() {
	inputFiles, err := listFiles(`./ffmpeg/mp3`, `.mp3`)
	if nil != err {
		println(`查找输入文件出错:`, err.Error())
	}
	if nil == inputFiles || len(inputFiles) == 0 {
		return
	}

	var command, out string
	for _, f := range inputFiles {
		o := fmt.Sprintf(`./ffmpeg/output/%s.m4a`, strings.TrimRight(strings.ToLower(path.Base(f)), ".mp3"))
		command, out, err = MP3ToM4A(f, o)
		if nil != err {
			println("error:", err.Error())
			println("command:", command)
			println("out:\n", out)
		}
	}
}

const (
	wrongMP3Output = `Estimating duration from bitrate, this may be inaccurate`
	infoCmdFormat  = `ffmpeg -i %s`
	tempCmdFormat  = `ffmpeg -i %s -c:a alac -b:a 80k -c:v copy %s -y`
	audioCmdFormat = `ffmpeg -i %s -movflags faststart -c:a aac -b:a 80k -vn %s -y`
	transCmdFormat = `ffmpeg -i %s -movflags faststart -c:a aac -b:a 80k %s -y`
)

// mp3转m4a
func MP3ToM4A(inputFileName, outputFileName string) (string, string, error) {
	var err error
	var command string

	// 先查看文件信息
	command = fmt.Sprintf(infoCmdFormat, inputFileName)
	out, _ := RunCmd(command)
	if strings.Contains(out, wrongMP3Output) { // 处理特殊编码的mp3文件
		// 选用原始编码器先复写一份临时m4a，此文件含图像，体积特别大
		tempFileName := fmt.Sprintf(`./%d.m4a`, wph.NextId())
		command = fmt.Sprintf(tempCmdFormat, inputFileName, tempFileName)
		out, err = RunCmd(command)
		if nil != err {
			return command, out, err
		}
		// 从临时文件中提取音频
		command = fmt.Sprintf(audioCmdFormat, tempFileName, outputFileName)
		out, err = RunCmd(command)
		if nil != err {
			return command, out, err
		}
		// 删除临时文件
		_ = os.Remove(tempFileName)
	} else { // 正常编码的mp3
		command := fmt.Sprintf(transCmdFormat, inputFileName, outputFileName)
		out, err = RunCmd(command)
		if nil != err {
			return command, out, err
		}
	}
	return command, out, nil
}

func RunCmd(command string) (string, error) {
	command = strings.TrimSpace(command)
	if command == "" {
		return "", nil
	}

	var cmdAndArgs []string
	arr := strings.Split(command, " ")
	for i := 0; i < len(arr); i++ {
		part := strings.TrimSpace(arr[i])
		if part == "" {
			continue
		}

		cmdAndArgs = append(cmdAndArgs, part)
	}
	if nil == cmdAndArgs || len(cmdAndArgs) == 0 {
		return "", nil
	}
	var cmd *exec.Cmd
	if len(cmdAndArgs) == 1 {
		cmd = exec.Command(cmdAndArgs[0])
	} else {
		cmd = exec.Command(cmdAndArgs[0], cmdAndArgs[1:]...)
	}
	var out bytes.Buffer
	cmd.Stdout = &out
	cmd.Stderr = &out
	err := cmd.Start()
	if nil != err {
		return out.String(), err
	}
	err = cmd.Wait()
	return out.String(), err
}

func listFiles(dirPath string, extList ...string) ([]string, error) {
	dir, err := os.Stat(dirPath)
	if (nil != err && os.IsNotExist(err)) || !dir.IsDir() {
		return nil, nil
	}
	err = nil

	var files []string
	err = filepath.Walk(dirPath, func(name string, info os.FileInfo, err error) error {
		if info.IsDir() {
			return nil
		}

		ext := strings.ToLower(path.Ext(name))
		if wph.Contains(extList, ext) {
			files = append(files, name)
		}
		return nil
	})
	if nil != err {
		return nil, err
	}
	return files, nil
}