package photos

import (
	"context"
	"image"
	"image/color"
	"image/jpeg"
	"image/png"
	"os"
	"path/filepath"
	"testing"

	"github.com/mithral/vellum/internal/media"
)

func writePNG(t *testing.T, w, h int) string {
	t.Helper()
	p := filepath.Join(t.TempDir(), "photo.png")
	f, err := os.Create(p)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()

	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{uint8(x % 256), uint8(y % 256), 128, 255})
		}
	}
	if err := png.Encode(f, img); err != nil {
		t.Fatal(err)
	}
	return p
}

func decode(t *testing.T, path string) image.Image {
	t.Helper()
	f, err := os.Open(path)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()
	img, _, err := image.Decode(f)
	if err != nil {
		t.Fatal(err)
	}
	return img
}

func TestExtractCoverDownscales(t *testing.T) {
	src := writePNG(t, 1000, 1500)
	cacheDir := t.TempDir()
	item := media.Item{ID: 7, Kind: Kind}

	out, err := ExtractCover(context.Background(), nil, item, src, cacheDir)
	if err != nil {
		t.Fatalf("ExtractCover: %v", err)
	}
	if out == "" {
		t.Fatal("no thumbnail produced")
	}

	img := decode(t, out)
	b := img.Bounds()
	if b.Dx() > thumbMax || b.Dy() > thumbMax {
		t.Errorf("thumbnail is %dx%d, exceeds %d", b.Dx(), b.Dy(), thumbMax)
	}
	// Aspect ratio must be preserved: 1000x1500 -> 341x512.
	if b.Dy() != thumbMax {
		t.Errorf("long edge = %d, want %d", b.Dy(), thumbMax)
	}
	if b.Dx() != 341 {
		t.Errorf("short edge = %d, want 341", b.Dx())
	}

	// It must actually be a JPEG.
	f, err := os.Open(out)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()
	if _, err := jpeg.Decode(f); err != nil {
		t.Errorf("output is not a JPEG: %v", err)
	}
}

func TestExtractCoverLeavesSmallImagesAlone(t *testing.T) {
	src := writePNG(t, 100, 80)
	out, err := ExtractCover(context.Background(), nil, media.Item{ID: 1, Kind: Kind}, src, t.TempDir())
	if err != nil {
		t.Fatalf("ExtractCover: %v", err)
	}
	img := decode(t, out)
	if img.Bounds().Dx() != 100 || img.Bounds().Dy() != 80 {
		t.Errorf("small image was resized to %v", img.Bounds())
	}
}

func TestExtractCoverIgnoresNonImage(t *testing.T) {
	p := filepath.Join(t.TempDir(), "not-an-image.jpg")
	if err := os.WriteFile(p, []byte("definitely not an image"), 0o644); err != nil {
		t.Fatal(err)
	}
	out, err := ExtractCover(context.Background(), nil, media.Item{ID: 1, Kind: Kind}, p, t.TempDir())
	if err != nil {
		t.Fatalf("a non-image must not error: %v", err)
	}
	if out != "" {
		t.Errorf("expected no thumbnail, got %q", out)
	}
}