package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"path"
	"regexp"
	"strings"
	"sync"
)

func init() {
	log.SetFlags(log.Lmicroseconds | log.Lshortfile)
}

func main() {
	flag.Parse()
	var wg sync.WaitGroup
	var renamedFiles sync.Map
	extensionRegex := regexp.MustCompile(`\.[a-zA-Z0-9]+$`)

	wg.Wait()
	wg = sync.WaitGroup{}
	for _, file := range flag.Args() {
		wg.Add(1)
		go func(file string) {
			defer wg.Done()
			file = path.Clean(file)
			log.Printf("Checking file %s", file)

			if !DoesFileExist(file) {
				log.Printf("File %s does not exist", file)
				return
			}

			info, err := os.Stat(file)
			if info == nil {
				log.Printf("Error checking file %s: %s", file, err)
				return
			}

			if info.IsDir() {
				log.Printf("File %s is a directory", file)
				return
			}

			modtime := info.ModTime()
			modtimeString := modtime.Local().Format("2006-01-02T15-04-05")
			newFile := modtimeString

			res := extensionRegex.FindAllString(file, -1)
			if len(res) == 0 {
				log.Printf("No extension found for file %s", file)
				return
			}
			extension := res[0]

			dir := path.Dir(file)
			newFile = fmt.Sprintf("%s/%s%s", dir, newFile, extension)
			newFile = path.Clean(newFile)
			newFile = strings.TrimRight(newFile, ".bak")
			log.Printf("New file name for %s: %s", file, newFile)

			if DoesFileExist(newFile) {
				log.Printf("File %s already exists", newFile)
				return
			}

			_, ok := renamedFiles.Load(newFile)
			if ok {
				log.Printf("File %s already renamed", newFile)
				return
			}

			if file == newFile {
				log.Printf("File %s already has the correct name", file)
				return
			}
			renamedFiles.Store(newFile, struct{}{})
			log.Printf("%s -> %s", file, newFile)
			err = os.Rename(file, newFile)
			if err != nil {
				log.Printf("Error renaming file %s to %s: %s", file, newFile, err)
				return
			}
		}(file)
	}
	wg.Wait()
}

func DoesFileExist(input string) bool {
	file, err := os.Open(input)
	if err != nil {
		return false
	}
	file.Close()
	return true
}