package main

import (
	"fmt"
	"log"
	"os"
	"os/exec"
	"path"
	"strings"
	"time"
)

var (
	timeLocation *time.Location
)

func init() {
	// 初始化时区
	var err error
	timeLocation, err = time.LoadLocation("Local")
	if err != nil {
		log.Fatalf("LoadLocation fail: %v", err)
	}
}

func main() {
	fmt.Println("start processing")
	pwd, err := os.Open(".")
	if err != nil {
		log.Fatalf("os.Open . error: %v", err)
	}
	defer pwd.Close()
	pwdInfo, err := pwd.Stat()
	if err != nil {
		log.Fatalf("pwd.Stat error: %v", err)
	}
	processDir(pwdInfo, pwd, []string{})
}

func processDir(pwdInfo os.FileInfo, pwd *os.File, paths []string) {
	fmt.Println("processing dir ", pwdInfo.Name())
	if !pwdInfo.IsDir() {
		log.Fatalf("input file %s is not a Dir", pwdInfo.Name())
	}
	if pwd == nil {
		var err error
		path := strings.Join(paths, "/")
		pwd, err = os.Open(path + "/" + pwdInfo.Name())
		if err != nil {
			log.Fatalf("os.Open %v %s error: %v", paths, pwdInfo.Name(), err)
		}
		defer pwd.Close()
	}
	fileInfos, err := pwd.Readdir(0)
	if err != nil {
		log.Fatalf("pwd %s Readdir error: %v", pwd.Name(), err)
	}
	ffmpegInstalled, ffmpegPath := checkFfmpegExist()
	if ffmpegInstalled {
		log.Println("ffmpeg installed: ", ffmpegPath)
	} else {
		log.Println("ffmpeg not installed, skip video files")
	}
	for _, fileInfo := range fileInfos {
		if fileInfo.IsDir() {
			processDir(fileInfo, nil, append(paths, pwdInfo.Name()))
		} else {
			ext := path.Ext(fileInfo.Name())
			switch ext {
			case ".jpg":
				processJPG(fileInfo, append(paths, pwdInfo.Name()))
			case ".mp4":
				if ffmpegInstalled {
					processMP4(fileInfo, append(paths, pwdInfo.Name()))
				}
			}
		}
	}
}

func processJPG(fileInfo os.FileInfo, paths []string) {
	filename := fileInfo.Name()
	path := strings.Join(paths, "/")
	if path != "." {
		filename = path + "/" + filename
	}
	t := fileInfo.ModTime()
	fmt.Println("processing file ", filename)
	err := os.Chtimes(filename, t, t)
	if err != nil {
		log.Printf("Chtimes file %s fail: %v\n", filename, err)
	}
	if filename != fileInfo.Name() {
		newName := strings.Join(paths[1:], "") + "-" + fileInfo.Name()
		log.Println("will rename ", filename, " to ", newName)
		err = os.Rename(filename, newName)
		if err != nil {
			log.Printf("Move file %s fail: %v\n", filename, err)
		}
	}
}

func processMP4(fileInfo os.FileInfo, paths []string) {
	filename := fileInfo.Name()
	path := strings.Join(paths, "/")
	if path != "." {
		filename = path + "/" + filename
	}
	t := fileInfo.ModTime()
	fmt.Println("processing file ", filename, t.Format(time.RFC3339))
	if filename != fileInfo.Name() {
		newName := strings.Join(paths[1:], "") + "-" + fileInfo.Name()
		log.Println("will move file ", filename, " to ", newName)
		cmd := exec.Command("ffmpeg", "-i", filename, "-c", "copy", "-metadata", "creation_time=\""+t.Format(time.RFC3339)+"\"", newName)
		err := cmd.Start()
		if err != nil {
			log.Println("set creation_time for file ", filename, " error: ", err)
			return
		}
	} else {
		log.Println("will replace old file ", filename)
		tmpFilename := filename + ".tmp.mp4"
		cmd := exec.Command("ffmpeg", "-i", filename, "-c", "copy", "-metadata", "creation_time="+t.Format(time.RFC3339), tmpFilename)
		err := cmd.Run()
		if err != nil {
			log.Println("set creation_time for file ", filename, " error: ", err)
			return
		}
		err = os.Remove(filename)
		if err != nil {
			log.Println("remove old file ", filename, " error")
			return
		}
		err = os.Rename(tmpFilename, filename)
		if err != nil {
			log.Println("move file ", tmpFilename, "to ", filename, " error")
			return
		}
	}
}

func checkFfmpegExist() (exist bool, path string) {
	path, err := exec.LookPath("ffmpeg")
	if err != nil {
		return
	}
	return true, path
}