package media

import (
	"bytes"
	"fmt"
	"image"
	_ "image/gif"
	_ "image/jpeg"
	_ "image/png"
	"io"

	"github.com/chai2010/webp"
	"github.com/disintegration/imaging"
)

const (
	DefaultMaxEdge  = 1920
	DefaultThumbEdge = 400
	DefaultQuality  = 80
)

type ProcessOptions struct {
	MaxEdge    int
	ThumbEdge  int
	WebPQuality float32
}

type ProcessedImage struct {
	Main       []byte
	MainType   string // image/webp
	MainExt    string // .webp
	Thumb      []byte
	ThumbType  string
	ThumbExt   string
	Width      int
	Height     int
	ThumbWidth int
	ThumbHeight int
}

// ProcessImage 解码 → 等比缩放 → WebP 主图 + 缩略图
func ProcessImage(r io.Reader, opt ProcessOptions) (*ProcessedImage, error) {
	if opt.MaxEdge <= 0 {
		opt.MaxEdge = DefaultMaxEdge
	}
	if opt.ThumbEdge <= 0 {
		opt.ThumbEdge = DefaultThumbEdge
	}
	if opt.WebPQuality <= 0 || opt.WebPQuality > 100 {
		opt.WebPQuality = DefaultQuality
	}

	src, _, err := image.Decode(r)
	if err != nil {
		return nil, fmt.Errorf("无法解码图片: %w", err)
	}

	mainImg := fitWithin(src, opt.MaxEdge)
	thumbImg := fitWithin(src, opt.ThumbEdge)

	mainBuf := &bytes.Buffer{}
	if err := webp.Encode(mainBuf, mainImg, &webp.Options{Quality: opt.WebPQuality}); err != nil {
		return nil, fmt.Errorf("webp 编码失败: %w", err)
	}
	thumbBuf := &bytes.Buffer{}
	if err := webp.Encode(thumbBuf, thumbImg, &webp.Options{Quality: opt.WebPQuality}); err != nil {
		return nil, fmt.Errorf("缩略图编码失败: %w", err)
	}

	bMain := mainImg.Bounds()
	bThumb := thumbImg.Bounds()
	return &ProcessedImage{
		Main:        mainBuf.Bytes(),
		MainType:    "image/webp",
		MainExt:     ".webp",
		Thumb:       thumbBuf.Bytes(),
		ThumbType:   "image/webp",
		ThumbExt:    ".webp",
		Width:       bMain.Dx(),
		Height:      bMain.Dy(),
		ThumbWidth:  bThumb.Dx(),
		ThumbHeight: bThumb.Dy(),
	}, nil
}

func fitWithin(img image.Image, maxEdge int) image.Image {
	b := img.Bounds()
	w, h := b.Dx(), b.Dy()
	if w <= maxEdge && h <= maxEdge {
		return img
	}
	if w >= h {
		return imaging.Resize(img, maxEdge, 0, imaging.Lanczos)
	}
	return imaging.Resize(img, 0, maxEdge, imaging.Lanczos)
}

// AllowedUploadMIME 上传阶段允许的源格式
func AllowedUploadMIME(contentType string) bool {
	switch contentType {
	case "image/jpeg", "image/png", "image/gif", "image/webp":
		return true
	default:
		return false
	}
}