package application

import (
	"bytes"
	"context"
	"encoding/base64"
	"image"
	"image/color"
	"image/png"
	"testing"
	"time"

	"img_infinite_canvas/internal/domain/design"
	"img_infinite_canvas/internal/infrastructure/memory"
)

func TestMergeLayersFlattensImagesInProjectLayerOrder(t *testing.T) {
	ctx := context.Background()
	repo := memory.NewProjectRepository()
	service := NewDesignService(repo, nil, nil, nil, nil)
	project := design.Project{
		ID:        "project-merge-layers",
		Title:     "Merge layers",
		Status:    design.StatusReady,
		UpdatedAt: time.Now(),
		Nodes: []design.Node{
			{
				ID:      "red",
				Type:    design.NodeTypeImage,
				Title:   "Red",
				X:       0,
				Y:       0,
				Width:   2,
				Height:  2,
				Content: testPNGDataURL(color.NRGBA{R: 255, A: 255}, 2, 2),
				Status:  "success",
			},
			{
				ID:      "blue",
				Type:    design.NodeTypeImage,
				Title:   "Blue",
				X:       1,
				Y:       0,
				Width:   2,
				Height:  2,
				Content: testPNGDataURL(color.NRGBA{B: 255, A: 255}, 2, 2),
				Status:  "success",
			},
		},
	}
	if err := repo.Save(ctx, project); err != nil {
		t.Fatal(err)
	}

	merged, err := service.MergeLayers(ctx, project.ID, []string{"blue", "red"}, "Merged")
	if err != nil {
		t.Fatal(err)
	}
	if len(merged.Nodes) != 3 {
		t.Fatalf("expected source layers plus async placeholder, got %#v", merged.Nodes)
	}
	placeholder := merged.Nodes[2]
	if placeholder.Status != "generating" || placeholder.LayerRole != "merge-layer" || placeholder.Content != "" {
		t.Fatalf("expected async merge placeholder, got %#v", merged.Nodes)
	}

	merged = waitForMergedProject(t, repo, project.ID)
	if len(merged.Nodes) != 1 {
		t.Fatalf("expected one merged node, got %d", len(merged.Nodes))
	}
	node := merged.Nodes[0]
	if node.Title != "Merged" || node.X != 0 || node.Y != 0 || node.Width != 3 || node.Height != 2 {
		t.Fatalf("unexpected merged node geometry: %#v", node)
	}

	imageData, _, _, ok, err := decodeDataImage(node.Content)
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatalf("expected merged content data URL, got %s", node.Content)
	}
	decoded, err := png.Decode(bytes.NewReader(imageData))
	if err != nil {
		t.Fatal(err)
	}
	assertPixel(t, decoded, 0, 0, color.NRGBA{R: 255, A: 255})
	assertPixel(t, decoded, 1, 0, color.NRGBA{B: 255, A: 255})
	assertPixel(t, decoded, 2, 0, color.NRGBA{B: 255, A: 255})
}

func TestMergeLayersFlattensTextOverImage(t *testing.T) {
	ctx := context.Background()
	repo := memory.NewProjectRepository()
	service := NewDesignService(repo, nil, nil, nil, nil)
	project := design.Project{
		ID:        "project-merge-text",
		Title:     "Merge text",
		Status:    design.StatusReady,
		UpdatedAt: time.Now(),
		Nodes: []design.Node{
			{ID: "image", Type: design.NodeTypeImage, Content: testPNGDataURL(color.NRGBA{R: 255, G: 255, B: 255, A: 255}, 120, 60), Width: 120, Height: 60, Status: "success"},
			{ID: "text", Type: design.NodeTypeText, Content: "123", X: 0, Y: 0, Width: 120, Height: 60, Status: "draft", FontSize: 28, Color: "#000000", TextAlign: "center"},
		},
	}
	if err := repo.Save(ctx, project); err != nil {
		t.Fatal(err)
	}

	_, err := service.MergeLayers(ctx, project.ID, []string{"image", "text"}, "")
	if err != nil {
		t.Fatal(err)
	}

	merged := waitForMergedProject(t, repo, project.ID)
	imageData, _, _, ok, err := decodeDataImage(merged.Nodes[0].Content)
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatalf("expected merged content data URL, got %s", merged.Nodes[0].Content)
	}
	decoded, err := png.Decode(bytes.NewReader(imageData))
	if err != nil {
		t.Fatal(err)
	}
	if countNonWhitePixels(decoded) == 0 {
		t.Fatal("expected text layer to be painted into merged image")
	}
}

func TestMergeLayersPreservesTransparentPixels(t *testing.T) {
	ctx := context.Background()
	repo := memory.NewProjectRepository()
	service := NewDesignService(repo, nil, nil, nil, nil)
	transparentLayer := image.NewNRGBA(image.Rect(0, 0, 3, 2))
	transparentLayer.SetNRGBA(1, 0, color.NRGBA{R: 255, A: 255})
	project := design.Project{
		ID:        "project-merge-transparent",
		Title:     "Merge transparent",
		Status:    design.StatusReady,
		UpdatedAt: time.Now(),
		Nodes: []design.Node{
			{
				ID:      "transparent",
				Type:    design.NodeTypeImage,
				Title:   "Transparent",
				X:       0,
				Y:       0,
				Width:   3,
				Height:  2,
				Content: testPNGDataURLFromImage(transparentLayer),
				Status:  "success",
			},
			{
				ID:      "blue",
				Type:    design.NodeTypeImage,
				Title:   "Blue",
				X:       2,
				Y:       1,
				Width:   1,
				Height:  1,
				Content: testPNGDataURL(color.NRGBA{B: 255, A: 255}, 1, 1),
				Status:  "success",
			},
		},
	}
	if err := repo.Save(ctx, project); err != nil {
		t.Fatal(err)
	}

	if _, err := service.MergeLayers(ctx, project.ID, []string{"transparent", "blue"}, "Transparent merge"); err != nil {
		t.Fatal(err)
	}

	merged := waitForMergedProject(t, repo, project.ID)
	node := merged.Nodes[0]
	if node.Tone != "transparent-image" {
		t.Fatalf("expected transparent merged image tone, got %q", node.Tone)
	}
	imageData, _, _, ok, err := decodeDataImage(node.Content)
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatalf("expected merged content data URL, got %s", node.Content)
	}
	decoded, err := png.Decode(bytes.NewReader(imageData))
	if err != nil {
		t.Fatal(err)
	}
	assertPixel(t, decoded, 0, 0, color.NRGBA{})
	assertPixel(t, decoded, 1, 0, color.NRGBA{R: 255, A: 255})
	assertPixel(t, decoded, 2, 1, color.NRGBA{B: 255, A: 255})
}

func waitForMergedProject(t *testing.T, repo design.Repository, projectID string) design.Project {
	t.Helper()
	deadline := time.After(2 * time.Second)
	ticker := time.NewTicker(10 * time.Millisecond)
	defer ticker.Stop()
	for {
		select {
		case <-deadline:
			t.Fatal("timed out waiting for async layer merge")
		case <-ticker.C:
			project, err := repo.Get(context.Background(), projectID)
			if err != nil {
				t.Fatal(err)
			}
			if project.Status == design.StatusReady && len(project.Nodes) == 1 && project.Nodes[0].Status == "success" {
				return project
			}
			if project.Status == design.StatusFailed {
				t.Fatalf("merge failed: %#v", project.Messages)
			}
		}
	}
}

func testPNGDataURL(fill color.NRGBA, width int, height int) string {
	img := image.NewNRGBA(image.Rect(0, 0, width, height))
	for y := 0; y < height; y++ {
		for x := 0; x < width; x++ {
			img.SetNRGBA(x, y, fill)
		}
	}
	return testPNGDataURLFromImage(img)
}

func testPNGDataURLFromImage(img image.Image) string {
	var buf bytes.Buffer
	if err := png.Encode(&buf, img); err != nil {
		panic(err)
	}
	return "data:image/png;base64," + base64.StdEncoding.EncodeToString(buf.Bytes())
}

func assertPixel(t *testing.T, img image.Image, x int, y int, expected color.NRGBA) {
	t.Helper()
	got := color.NRGBAModel.Convert(img.At(x, y)).(color.NRGBA)
	if got != expected {
		t.Fatalf("pixel(%d,%d): got %#v, want %#v", x, y, got, expected)
	}
}

func countNonWhitePixels(img image.Image) int {
	bounds := img.Bounds()
	count := 0
	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
		for x := bounds.Min.X; x < bounds.Max.X; x++ {
			pixel := color.NRGBAModel.Convert(img.At(x, y)).(color.NRGBA)
			if pixel.A > 0 && (pixel.R < 245 || pixel.G < 245 || pixel.B < 245) {
				count++
			}
		}
	}
	return count
}