package service

import (
	"bytes"
	"image"
	"image/color"
	"image/jpeg"
	"image/png"
	"testing"
)

// makeTestImage 生成指定尺寸的 jpg/png 测试图
func makeTestImage(t *testing.T, w, h int, pngFmt bool) []byte {
	t.Helper()
	img := image.NewRGBA(image.Rect(0, 0, w, h))
	for y := 0; y < h; y++ {
		for x := 0; x < w; x++ {
			img.Set(x, y, color.RGBA{R: uint8(x % 256), G: uint8(y % 256), B: 128, A: 255})
		}
	}
	var buf bytes.Buffer
	if pngFmt {
		if err := png.Encode(&buf, img); err != nil {
			t.Fatal(err)
		}
	} else {
		if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 92}); err != nil {
			t.Fatal(err)
		}
	}
	return buf.Bytes()
}

// decodeSize 解码并返回宽高
func decodeSize(t *testing.T, data []byte) (int, int) {
	t.Helper()
	img, _, err := image.Decode(bytes.NewReader(data))
	if err != nil {
		t.Fatalf("解码失败: %v", err)
	}
	return img.Bounds().Dx(), img.Bounds().Dy()
}

func TestResizeCover(t *testing.T) {
	cases := []struct {
		name string
		w, h int
		png  bool
	}{
		{"标准16:9大图", 3000, 1688, false},
		{"超宽图", 4000, 1000, false},
		{"超窄图", 800, 3000, false},
		{"接近目标尺寸", 1280, 720, false},
		{"小于目标尺寸", 800, 600, false},
		{"PNG透明通道", 2000, 1500, true},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			out, err := resizeCover(makeTestImage(t, c.w, c.h, c.png))
			if err != nil {
				t.Fatalf("resizeCover 失败: %v", err)
			}
			gotW, gotH := decodeSize(t, out)
			if gotW != coverWidth || gotH != coverHeight {
				t.Fatalf("尺寸错误: got %dx%d, want %dx%d", gotW, gotH, coverWidth, coverHeight)
			}
		})
	}
}