package main

import (
	"fmt"
	"log"
	"os"
	"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)
	}
	for _, fileInfo := range fileInfos {
		if fileInfo.IsDir() {
			processDir(fileInfo, nil, append(paths, pwdInfo.Name()))
		} else {
			ext := path.Ext(fileInfo.Name())
			switch ext {
			case ".mp4":
				processMP4(fileInfo, append(paths, pwdInfo.Name()))
			}
		}
	}
}

func processMP4(fileInfo os.FileInfo, paths []string) {
	filename := fileInfo.Name()
	path := strings.Join(paths, "/")
	if path != "." {
		filename = path + "/" + filename
	}
	t, err := time.ParseInLocation("20060102150405", strings.Split(fileInfo.Name(), "-")[1][:14], timeLocation)
	if err != nil {
		log.Println("Parse time fail from filename ", fileInfo.Name())
		return
	}
	fmt.Println("processing file ", filename, t.Format(time.RFC3339))
	err = os.Chtimes(filename, t, t)
	if err != nil {
		log.Printf("Chtimes file %s fail: %v\n", filename, err)
	}
}