package main

import (
	"fmt"
	"image"
	"image/jpeg"
	"image/png"
	"os"
	"path/filepath"
	"strings"
	"sync"

	"github.com/chai2010/webp"
)

type Options struct {
	InputDir   string
	OutputDir  string
	Quality    int
	Workers    int
	Recursive  bool
}

func main() {
	opts := Options{
		InputDir:  "./images",   // 輸入目錄
		OutputDir: "./output",   // 輸出目錄
		Quality:   75,           // 壓縮質(zhì)量（0-100）
		Workers:   4,            // 并發(fā) worker 數(shù)
		Recursive: true,         // 是否遞歸
	}

	if err := run(opts); err != nil {
		fmt.Println("? 發(fā)生錯(cuò)誤:", err)
		os.Exit(1)
	}
	fmt.Println("? 批量壓縮完成！")
}

func run(opts Options) error {
	// 收集所有待處理文件
	var files []string
	err := filepath.Walk(opts.InputDir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if info.IsDir() {
			if path != opts.InputDir && !opts.Recursive {
				return filepath.SkipDir
			}
			return nil
		}
		ext := strings.ToLower(filepath.Ext(info.Name()))
		if ext == ".jpg" || ext == ".jpeg" || ext == ".png" || ext == ".webp" {
			files = append(files, path)
		}
		return nil
	})
	if err != nil {
		return err
	}

	if len(files) == 0 {
		return fmt.Errorf("沒有找到任何圖片文件")
	}

	// worker pool
	fileCh := make(chan string)
	var wg sync.WaitGroup

	for i := 0; i < opts.Workers; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for f := range fileCh {
				if err := compressImage(f, opts); err != nil {
					fmt.Printf("?? 壓縮失敗 %s: %v\n", f, err)
				} else {
					fmt.Printf("? 壓縮完成: %s\n", f)
				}
			}
		}()
	}

	for _, f := range files {
		fileCh <- f
	}
	close(fileCh)

	wg.Wait()
	return nil
}

// 壓縮單張圖片
func compressImage(path string, opts Options) error {
	inFile, err := os.Open(path)
	if err != nil {
		return err
	}
	defer inFile.Close()

	img, format, err := image.Decode(inFile)
	if err != nil {
		return fmt.Errorf("解碼失敗: %w", err)
	}

	// 輸出路徑
	rel, _ := filepath.Rel(opts.InputDir, path)
	outPath := filepath.Join(opts.OutputDir, rel)
	if err := os.MkdirAll(filepath.Dir(outPath), 0755); err != nil {
		return err
	}

	outFile, err := os.Create(outPath)
	if err != nil {
		return err
	}
	defer outFile.Close()

	switch format {
	case "jpeg":
		err = jpeg.Encode(outFile, img, &jpeg.Options{Quality: opts.Quality})
	case "png":
		encoder := png.Encoder{CompressionLevel: png.BestCompression}
		err = encoder.Encode(outFile, img)
	case "webp":
		err = webp.Encode(outFile, img, &webp.Options{Quality: float32(opts.Quality)})
	default:
		return fmt.Errorf("不支持的格式: %s", format)
	}
	return err
}

go mod init img-compressor
go get github.com/chai2010/webp

go run main.go