// Copyright 2018 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package atlas_test

import (
	"image"
	"image/color"
	"runtime"
	"testing"
	"time"
	"unsafe"

	"github.com/hajimehoshi/ebiten/v2/internal/atlas"
	"github.com/hajimehoshi/ebiten/v2/internal/graphics"
	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
	t "github.com/hajimehoshi/ebiten/v2/internal/testing"
	"github.com/hajimehoshi/ebiten/v2/internal/ui"
)

const (
	minSourceImageSizeForTesting      = 1024
	minDestinationImageSizeForTesting = 256
	maxImageSizeForTesting            = 4096
)

func TestMain(m *testing.M) {
	atlas.SetImageSizeForTesting(minSourceImageSizeForTesting, minDestinationImageSizeForTesting, maxImageSizeForTesting)
	defer atlas.ResetImageSizeForTesting()
	t.MainWithRunLoop(m)
}

func quadVertices(sw, sh, x, y int, scalex float32) []float32 {
	dx0 := float32(x)
	dy0 := float32(y)
	dx1 := float32(x) + float32(sw)*scalex
	dy1 := float32(y) + float32(sh)
	sx0 := float32(0)
	sy0 := float32(0)
	sx1 := float32(sw)
	sy1 := float32(sh)
	vs := make([]float32, 4*graphics.VertexFloatCount)
	graphics.QuadVerticesFromDstAndSrc(vs, dx0, dy0, dx1, dy1, sx0, sy0, sx1, sy1, 1, 1, 1, 1)
	return vs
}

const bigSize = 2049

func TestEnsureIsolatedFromSourceBackend(t *testing.T) {
	// Create img1 and img2 with this size so that the next images are allocated
	// with non-upper-left location.
	img1 := atlas.NewImage(bigSize, 100, atlas.ImageTypeRegular)
	defer img1.Deallocate()
	// Ensure img1's region is allocated.
	img1.WritePixels(make([]byte, 4*bigSize*100), image.Rect(0, 0, bigSize, 100))

	img2 := atlas.NewImage(100, bigSize, atlas.ImageTypeRegular)
	defer img2.Deallocate()
	img2.WritePixels(make([]byte, 4*100*bigSize), image.Rect(0, 0, 100, bigSize))

	const size = 32

	img3 := atlas.NewImage(size/2, size/2, atlas.ImageTypeRegular)
	defer img3.Deallocate()
	img3.WritePixels(make([]byte, (size/2)*(size/2)*4), image.Rect(0, 0, size/2, size/2))

	img4 := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer img4.Deallocate()

	img5 := atlas.NewImage(size/2, size/2, atlas.ImageTypeRegular)
	defer img3.Deallocate()

	pix := make([]byte, size*size*4)
	for j := range size {
		for i := range size {
			pix[4*(i+j*size)] = byte(i + j)
			pix[4*(i+j*size)+1] = byte(i + j)
			pix[4*(i+j*size)+2] = byte(i + j)
			pix[4*(i+j*size)+3] = byte(i + j)
		}
	}
	img4.WritePixels(pix, image.Rect(0, 0, size, size))

	const (
		dx0 = size / 4
		dy0 = size / 4
		dx1 = size * 3 / 4
		dy1 = size * 3 / 4
	)
	// img4.ensureIsolatedFromSource() should be called.
	vs := quadVertices(size/2, size/2, size/4, size/4, 1)
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, size, size)
	sr := image.Rect(0, 0, size/2, size/2)
	img4.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img3}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
	if got, want := img4.IsOnSourceBackendForTesting(), false; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}

	// img5 is not allocated now, but is allocated at DrawTriangles.
	vs = quadVertices(0, 0, size/2, size/2, 1)
	dr = image.Rect(0, 0, size/2, size/2)
	sr = image.Rect(0, 0, size/2, size/2)
	img3.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img5}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
	if got, want := img3.IsOnSourceBackendForTesting(), false; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}

	pix = make([]byte, 4*size*size)
	ok, err := img4.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, size, size))
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("ReadPixels failed")
	}
	for j := range size {
		for i := range size {
			r := pix[4*(size*j+i)]
			g := pix[4*(size*j+i)+1]
			b := pix[4*(size*j+i)+2]
			a := pix[4*(size*j+i)+3]
			got := color.RGBA{R: r, G: g, B: b, A: a}
			var want color.RGBA
			if i < dx0 || dx1 <= i || j < dy0 || dy1 <= j {
				c := byte(i + j)
				want = color.RGBA{R: c, G: c, B: c, A: c}
			}
			if got != want {
				t.Errorf("at(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	// Check further drawing doesn't cause panic.
	// This bug was fixed by 03dcd948.
	vs = quadVertices(0, 0, size/2, size/2, 1)
	dr = image.Rect(0, 0, size, size)
	sr = image.Rect(0, 0, size/2, size/2)
	img4.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img3}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
}

func TestReputOnSourceBackend(t *testing.T) {
	const size = 16

	img0 := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer img0.Deallocate()
	img0.WritePixels(make([]byte, 4*size*size), image.Rect(0, 0, size, size))

	img1 := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer img1.Deallocate()
	img1.WritePixels(make([]byte, 4*size*size), image.Rect(0, 0, size, size))
	if got, want := img1.IsOnSourceBackendForTesting(), true; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}

	img2 := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer img2.Deallocate()
	pix := make([]byte, 4*size*size)
	for j := range size {
		for i := range size {
			pix[4*(i+j*size)] = byte(i + j)
			pix[4*(i+j*size)+1] = byte(i + j)
			pix[4*(i+j*size)+2] = byte(i + j)
			pix[4*(i+j*size)+3] = byte(i + j)
		}
	}
	img2.WritePixels(pix, image.Rect(0, 0, size, size))

	// Create an unmanaged image. This should always be on a non-source backend.
	img3 := atlas.NewImage(size, size, atlas.ImageTypeUnmanaged)
	defer img3.Deallocate()
	img3.WritePixels(make([]byte, 4*size*size), image.Rect(0, 0, size, size))
	if got, want := img3.IsOnSourceBackendForTesting(), false; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}

	// Use img1 as a render target.
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, size, size)
	sr := image.Rect(0, 0, size, size)
	// Render onto img1. The count should not matter.
	for range 5 {
		vs := quadVertices(size, size, 0, 0, 1)
		img1.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
			t.Errorf("got: %v, want: %v", got, want)
		}
	}

	// Use img1 as a render source.
	// Use the doubled count since img1 was on a texture atlas and became an isolated image once.
	// Then, img1 requires longer time to recover to be on a texture atlas again.
	for range atlas.BaseCountToPutOnSourceBackend * 2 {
		atlas.PutImagesOnSourceBackendForTesting()
		vs := quadVertices(size, size, 0, 0, 1)
		img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
			t.Errorf("got: %v, want: %v", got, want)
		}
	}
	// Finally, img1 is on a source backend.
	atlas.PutImagesOnSourceBackendForTesting()
	vs := quadVertices(size, size, 0, 0, 1)
	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
	if got, want := img1.IsOnSourceBackendForTesting(), true; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}
	atlas.PutImagesOnSourceBackendForTesting()

	pix = make([]byte, 4*size*size)
	ok, err := img1.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, size, size))
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("ReadPixels failed")
	}
	for j := range size {
		for i := range size {
			want := color.RGBA{R: byte(i + j), G: byte(i + j), B: byte(i + j), A: byte(i + j)}
			r := pix[4*(size*j+i)]
			g := pix[4*(size*j+i)+1]
			b := pix[4*(size*j+i)+2]
			a := pix[4*(size*j+i)+3]
			got := color.RGBA{R: r, G: g, B: b, A: a}
			if got != want {
				t.Errorf("At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	vs = quadVertices(size, size, 0, 0, 1)
	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
	if got, want := img1.IsOnSourceBackendForTesting(), true; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}

	pix = make([]byte, 4*size*size)
	ok, err = img1.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, size, size))
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("ReadPixels failed")
	}
	for j := range size {
		for i := range size {
			want := color.RGBA{R: byte(i + j), G: byte(i + j), B: byte(i + j), A: byte(i + j)}
			r := pix[4*(size*j+i)]
			g := pix[4*(size*j+i)+1]
			b := pix[4*(size*j+i)+2]
			a := pix[4*(size*j+i)+3]
			got := color.RGBA{R: r, G: g, B: b, A: a}
			if got != want {
				t.Errorf("At(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	// Use img1 as a render target again. The count should not matter.
	for range 5 {
		vs := quadVertices(size, size, 0, 0, 1)
		img1.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
			t.Errorf("got: %v, want: %v", got, want)
		}
	}

	// Use img1 as a render source, but call WritePixels.
	// Now use 4x count as img1 became an isolated image again.
	for range atlas.BaseCountToPutOnSourceBackend * 4 {
		atlas.PutImagesOnSourceBackendForTesting()
		img1.WritePixels(make([]byte, 4*size*size), image.Rect(0, 0, size, size))
		vs := quadVertices(size, size, 0, 0, 1)
		img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
			t.Errorf("got: %v, want: %v", got, want)
		}
	}
	atlas.PutImagesOnSourceBackendForTesting()

	// img1 is not on an atlas due to WritePixels.
	vs = quadVertices(size, size, 0, 0, 1)
	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
	if got, want := img1.IsOnSourceBackendForTesting(), false; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}

	// Use img3 as a render source. As img3 is unmanaged, img3 is never on an atlas.
	for range atlas.BaseCountToPutOnSourceBackend * 2 {
		atlas.PutImagesOnSourceBackendForTesting()
		vs := quadVertices(size, size, 0, 0, 1)
		img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img3}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		if got, want := img3.IsOnSourceBackendForTesting(), false; got != want {
			t.Errorf("got: %v, want: %v", got, want)
		}
	}

	runtime.GC()
}

func TestExtend(t *testing.T) {
	const w0, h0 = 100, 100
	img0 := atlas.NewImage(w0, h0, atlas.ImageTypeRegular)
	defer img0.Deallocate()

	p0 := make([]byte, 4*w0*h0)
	for i := range w0 * h0 {
		p0[4*i] = byte(i)
		p0[4*i+1] = byte(i)
		p0[4*i+2] = byte(i)
		p0[4*i+3] = byte(i)
	}
	img0.WritePixels(p0, image.Rect(0, 0, w0, h0))

	const w1, h1 = minSourceImageSizeForTesting + 1, 100
	img1 := atlas.NewImage(w1, h1, atlas.ImageTypeRegular)
	defer img1.Deallocate()

	p1 := make([]byte, 4*w1*h1)
	for i := range w1 * h1 {
		p1[4*i] = byte(i)
		p1[4*i+1] = byte(i)
		p1[4*i+2] = byte(i)
		p1[4*i+3] = byte(i)
	}
	// Ensure to allocate
	img1.WritePixels(p1, image.Rect(0, 0, w1, h1))

	pix0 := make([]byte, 4*w0*h0)
	ok, err := img0.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix0, image.Rect(0, 0, w0, h0))
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("ReadPixels failed")
	}
	for j := range h0 {
		for i := range w0 {
			r := pix0[4*(w0*j+i)]
			g := pix0[4*(w0*j+i)+1]
			b := pix0[4*(w0*j+i)+2]
			a := pix0[4*(w0*j+i)+3]
			got := color.RGBA{R: r, G: g, B: b, A: a}
			c := byte(i + w0*j)
			want := color.RGBA{R: c, G: c, B: c, A: c}
			if got != want {
				t.Errorf("at(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}

	pix1 := make([]byte, 4*w1*h1)
	ok, err = img1.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix1, image.Rect(0, 0, w1, h1))
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("ReadPixels failed")
	}
	for j := range h1 {
		for i := range w1 {
			r := pix1[4*(w1*j+i)]
			g := pix1[4*(w1*j+i)+1]
			b := pix1[4*(w1*j+i)+2]
			a := pix1[4*(w1*j+i)+3]
			got := color.RGBA{R: r, G: g, B: b, A: a}
			c := byte(i + w1*j)
			want := color.RGBA{R: c, G: c, B: c, A: c}
			if got != want {
				t.Errorf("at(%d, %d): got: %v, want: %v", i, j, got, want)
			}
		}
	}
}

func TestWritePixelsAfterDrawTriangles(t *testing.T) {
	const w, h = 256, 256
	src := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer src.Deallocate()
	dst := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer dst.Deallocate()

	pix := make([]byte, 4*w*h)
	for i := range w * h {
		pix[4*i] = byte(i)
		pix[4*i+1] = byte(i)
		pix[4*i+2] = byte(i)
		pix[4*i+3] = byte(i)
	}
	src.WritePixels(pix, image.Rect(0, 0, w, h))

	vs := quadVertices(w, h, 0, 0, 1)
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, w, h)
	sr := image.Rect(0, 0, w, h)
	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
	dst.WritePixels(pix, image.Rect(0, 0, w, h))

	pix = make([]byte, 4*w*h)
	ok, err := dst.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, w, h))
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("ReadPixels failed")
	}
	for j := range h {
		for i := range w {
			r := pix[4*(w*j+i)]
			g := pix[4*(w*j+i)+1]
			b := pix[4*(w*j+i)+2]
			a := pix[4*(w*j+i)+3]
			got := color.RGBA{R: r, G: g, B: b, A: a}
			c := byte(i + w*j)
			want := color.RGBA{R: c, G: c, B: c, A: c}
			if got != want {
				t.Errorf("at(%d, %d): got %v, want: %v", i, j, got, want)
			}
		}
	}
}

// Issue #887
func TestSmallImages(t *testing.T) {
	const w, h = 4, 8
	src := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer src.Deallocate()
	dst := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer dst.Deallocate()

	pix := make([]byte, 4*w*h)
	for i := range w * h {
		pix[4*i] = 0xff
		pix[4*i+1] = 0xff
		pix[4*i+2] = 0xff
		pix[4*i+3] = 0xff
	}
	src.WritePixels(pix, image.Rect(0, 0, w, h))

	vs := quadVertices(w, h, 0, 0, 1)
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, w, h)
	sr := image.Rect(0, 0, w, h)
	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)

	pix = make([]byte, 4*w*h)
	ok, err := dst.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, w, h))
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("ReadPixels failed")
	}
	for j := range h {
		for i := range w {
			r := pix[4*(w*j+i)]
			a := pix[4*(w*j+i)+3]
			if got, want := r, byte(0xff); got != want {
				t.Errorf("at(%d, %d) red: got: %d, want: %d", i, j, got, want)
			}
			if got, want := a, byte(0xff); got != want {
				t.Errorf("at(%d, %d) alpha: got: %d, want: %d", i, j, got, want)
			}
		}
	}
}

// Issue #887
func TestLongImages(t *testing.T) {
	const w, h = 1, 6
	src := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer src.Deallocate()

	const dstW, dstH = 256, 256
	dst := atlas.NewImage(dstW, dstH, atlas.ImageTypeRegular)
	defer dst.Deallocate()

	pix := make([]byte, 4*w*h)
	for i := range w * h {
		pix[4*i] = 0xff
		pix[4*i+1] = 0xff
		pix[4*i+2] = 0xff
		pix[4*i+3] = 0xff
	}
	src.WritePixels(pix, image.Rect(0, 0, w, h))

	const scale = 120
	vs := quadVertices(w, h, 0, 0, scale)
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, dstW, dstH)
	sr := image.Rect(0, 0, w, h)
	dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendSourceOver, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)

	pix = make([]byte, 4*dstW*dstH)
	ok, err := dst.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, dstW, dstH))
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("ReadPixels failed")
	}
	for j := range h {
		for i := range w * scale {
			r := pix[4*(dstW*j+i)]
			a := pix[4*(dstW*j+i)+3]
			if got, want := r, byte(0xff); got != want {
				t.Errorf("at(%d, %d) red: got: %d, want: %d", i, j, got, want)
			}
			if got, want := a, byte(0xff); got != want {
				t.Errorf("at(%d, %d) alpha: got: %d, want: %d", i, j, got, want)
			}
		}
	}
}

func TestDeallocateImmediately(t *testing.T) {
	// This tests ClearPixels is called but WritePixels is not called.

	img0 := atlas.NewImage(16, 16, atlas.ImageTypeRegular)
	img0.EnsureIsolatedFromSourceForTesting(nil)
	defer img0.Deallocate()

	img1 := atlas.NewImage(16, 16, atlas.ImageTypeRegular)
	img1.EnsureIsolatedFromSourceForTesting(nil)
	defer img1.Deallocate()

	// img0 and img1 should share the same backend in 99.9999% possibility.
}

// Issue #1028
func TestExtendWithBigImage(t *testing.T) {
	img0 := atlas.NewImage(1, 1, atlas.ImageTypeRegular)
	defer img0.Deallocate()

	img0.WritePixels(make([]byte, 4*1*1), image.Rect(0, 0, 1, 1))

	img1 := atlas.NewImage(minSourceImageSizeForTesting+1, minSourceImageSizeForTesting+1, atlas.ImageTypeRegular)
	defer img1.Deallocate()

	img1.WritePixels(make([]byte, 4*(minSourceImageSizeForTesting+1)*(minSourceImageSizeForTesting+1)), image.Rect(0, 0, minSourceImageSizeForTesting+1, minSourceImageSizeForTesting+1))
}

// Issue #1217
func TestMaxImageSize(t *testing.T) {
	img0 := atlas.NewImage(1, 1, atlas.ImageTypeRegular)
	defer img0.Deallocate()
	paddingSize := img0.PaddingSizeForTesting()

	// This tests that a too-big image is allocated correctly.
	s := maxImageSizeForTesting - 2*paddingSize
	img1 := atlas.NewImage(s, s, atlas.ImageTypeRegular)
	defer img1.Deallocate()
	img1.WritePixels(make([]byte, 4*s*s), image.Rect(0, 0, s, s))
}

// Issue #1217 (disabled)
func Disable_TestMinImageSize(t *testing.T) {
	// The backend cannot be reset. If this is necessary, sync the state with the images (#1756).
	// ResetBackendsForTesting()

	// This tests that extending a backend works correctly.
	// Though the image size is minimum size of the backend, extending the backend happens due to the paddings.
	s := minSourceImageSizeForTesting
	img := atlas.NewImage(s, s, atlas.ImageTypeRegular)
	defer img.Deallocate()
	img.WritePixels(make([]byte, 4*s*s), image.Rect(0, 0, s, s))
}

func TestMaxImageSizeJust(t *testing.T) {
	s := maxImageSizeForTesting
	// An unmanaged image never belongs to an atlas and doesn't have its paddings.
	// TODO: Should we allow such this size for ImageTypeRegular?
	img := atlas.NewImage(s, s, atlas.ImageTypeUnmanaged)
	defer img.Deallocate()
	img.WritePixels(make([]byte, 4*s*s), image.Rect(0, 0, s, s))
}

func TestMaxImageSizeExceeded(t *testing.T) {
	// This tests that a too-big image is allocated correctly.
	s := maxImageSizeForTesting
	img := atlas.NewImage(s+1, s, atlas.ImageTypeRegular)
	defer img.Deallocate()

	defer func() {
		if err := recover(); err == nil {
			t.Errorf("WritePixels must panic but not")
		}
	}()

	img.WritePixels(make([]byte, 4*(s+1)*s), image.Rect(0, 0, s+1, s))
}

// Issue #1421
func TestDeallocatedAndReputOnSourceBackend(t *testing.T) {
	const size = 16

	src := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer src.Deallocate()
	src2 := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer src2.Deallocate()
	dst := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer dst.Deallocate()

	// Use src as a render target so that src is not on an atlas.
	vs := quadVertices(size, size, 0, 0, 1)
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, size, size)
	sr := image.Rect(0, 0, size, size)
	src.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
	if got, want := src.IsOnSourceBackendForTesting(), false; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}

	// Use src as a render source.
	for range atlas.BaseCountToPutOnSourceBackend / 2 {
		atlas.PutImagesOnSourceBackendForTesting()
		vs := quadVertices(size, size, 0, 0, 1)
		dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		if got, want := src.IsOnSourceBackendForTesting(), false; got != want {
			t.Errorf("got: %v, want: %v", got, want)
		}
	}

	// Before PutImagesOnSourceBackendForTesting, deallocate the image.
	src.Deallocate()

	// Confirm that PutImagesOnSourceBackendForTesting doesn't panic.
	atlas.PutImagesOnSourceBackendForTesting()
}

// Issue #1456
func TestImageIsNotReputOnSourceBackendWithoutUsingAsSource(t *testing.T) {
	const size = 16

	src := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer src.Deallocate()
	src2 := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer src2.Deallocate()
	dst := atlas.NewImage(size, size, atlas.ImageTypeRegular)
	defer dst.Deallocate()

	// Use src as a render target so that src is not on an atlas.
	vs := quadVertices(size, size, 0, 0, 1)
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, size, size)
	sr := image.Rect(0, 0, size, size)

	// Use src2 as a rendering target, and make src2 on a destination backend.
	//
	// Call DrawTriangles multiple times.
	// The number of DrawTriangles doesn't matter as long as these are called in one frame.
	for range 2 {
		src2.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
	}
	if got, want := src2.IsOnSourceBackendForTesting(), false; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}

	// Update the count without using src2 as a rendering source.
	// This should not affect whether src2 is on an atlas or not.
	for range atlas.BaseCountToPutOnSourceBackend {
		atlas.PutImagesOnSourceBackendForTesting()
		if got, want := src2.IsOnSourceBackendForTesting(), false; got != want {
			t.Errorf("got: %v, want: %v", got, want)
		}
	}

	// Update the count with using src2 as a rendering source.
	for range atlas.BaseCountToPutOnSourceBackend {
		atlas.PutImagesOnSourceBackendForTesting()
		vs := quadVertices(size, size, 0, 0, 1)
		dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src2}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		if got, want := src2.IsOnSourceBackendForTesting(), false; got != want {
			t.Errorf("got: %v, want: %v", got, want)
		}
	}

	atlas.PutImagesOnSourceBackendForTesting()
	if got, want := src2.IsOnSourceBackendForTesting(), true; got != want {
		t.Errorf("got: %v, want: %v", got, want)
	}
}

func TestImageWritePixelsModify(t *testing.T) {
	for _, typ := range []atlas.ImageType{atlas.ImageTypeRegular, atlas.ImageTypeUnmanaged} {
		const size = 16
		img := atlas.NewImage(size, size, typ)
		defer img.Deallocate()
		pix := make([]byte, 4*size*size)
		for j := range size {
			for i := range size {
				pix[4*(i+j*size)] = byte(i + j)
				pix[4*(i+j*size)+1] = byte(i + j)
				pix[4*(i+j*size)+2] = byte(i + j)
				pix[4*(i+j*size)+3] = byte(i + j)
			}
		}
		img.WritePixels(pix, image.Rect(0, 0, size, size))

		// Modify pix after WritePixels.
		for j := range size {
			for i := range size {
				pix[4*(i+j*size)] = 0
				pix[4*(i+j*size)+1] = 0
				pix[4*(i+j*size)+2] = 0
				pix[4*(i+j*size)+3] = 0
			}
		}

		// Check the pixels are the original ones.
		pix = make([]byte, 4*size*size)
		ok, err := img.ReadPixels(ui.Get().GraphicsDriverForTesting(), pix, image.Rect(0, 0, size, size))
		if err != nil {
			t.Fatal(err)
		}
		if !ok {
			t.Fatal("ReadPixels failed")
		}
		for j := range size {
			for i := range size {
				want := color.RGBA{R: byte(i + j), G: byte(i + j), B: byte(i + j), A: byte(i + j)}
				r := pix[4*(size*j+i)]
				g := pix[4*(size*j+i)+1]
				b := pix[4*(size*j+i)+2]
				a := pix[4*(size*j+i)+3]
				got := color.RGBA{R: r, G: g, B: b, A: a}
				if got != want {
					t.Errorf("Type: %d, At(%d, %d): got: %v, want: %v", typ, i, j, got, want)
				}
			}
		}
	}
}

func TestPowerOf2(t *testing.T) {
	testCases := []struct {
		In  int
		Out int
	}{
		{
			In:  1023,
			Out: 512,
		},
		{
			In:  1024,
			Out: 1024,
		},
		{
			In:  1025,
			Out: 1024,
		},
		{
			In:  10000,
			Out: 8192,
		},
		{
			In:  16384,
			Out: 16384,
		},
		{
			In:  1,
			Out: 1,
		},
		{
			In:  0,
			Out: 0,
		},
		{
			In:  -1,
			Out: 0,
		},
	}

	for _, tc := range testCases {
		got := atlas.FloorPowerOf2(tc.In)
		want := tc.Out
		if got != want {
			t.Errorf("packing.FloorPowerOf2(%d): got: %d, want: %d", tc.In, got, want)
		}
	}
}

func TestDestinationCountOverflow(t *testing.T) {
	const w, h = 256, 256
	src := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer src.Deallocate()
	dst0 := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer dst0.Deallocate()
	dst1 := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer dst1.Deallocate()

	vs := quadVertices(w, h, 0, 0, 1)
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, w, h)
	sr := image.Rect(0, 0, w, h)

	// Use dst0 as a destination for a while.
	for range 31 {
		dst0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		atlas.PutImagesOnSourceBackendForTesting()
	}

	// Use dst0 as a source for a while.
	// As dst0 is used as a destination too many times (31 is a maximum), dst0's backend should never be a source backend.
	for i := range 100 {
		dst1.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{dst0}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		atlas.PutImagesOnSourceBackendForTesting()
		if dst0.IsOnSourceBackendForTesting() {
			t.Errorf("dst0 cannot be on a source backend: %d", i)
		}
	}
}

// Issue #2729
func TestIteratingImagesToPutOnSourceBackend(t *testing.T) {
	const w, h = 16, 16
	src := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer src.Deallocate()
	srcs := make([]*atlas.Image, 10)
	for i := range srcs {
		srcs[i] = atlas.NewImage(w, h, atlas.ImageTypeRegular)
		defer srcs[i].Deallocate()
	}
	dst := atlas.NewImage(w, h, atlas.ImageTypeRegular)
	defer dst.Deallocate()

	// Use srcs as destinations once.
	vs := quadVertices(w, h, 0, 0, 1)
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, w, h)
	sr := image.Rect(0, 0, w, h)
	for _, img := range srcs {
		img.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
	}
	atlas.PutImagesOnSourceBackendForTesting()

	// Use srcs as sources. This will register an image to imagesToPutOnSourceBackend.
	// Check iterating the registered image works correctly.
	for range 100 {
		for _, src := range srcs {
			dst.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{src}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)
		}
		atlas.PutImagesOnSourceBackendForTesting()
	}
}

func ensureGC() {
	// Use a pointer to avoid tinyalloc. A tinyalloc-ed object's finalizer might not called immediately.
	// See runtime/mfinal_test.go.
	x := new(unsafe.Pointer)
	ch := make(chan struct{})
	runtime.AddCleanup(x, func(_ struct{}) { close(ch) }, struct{}{})
	runtime.KeepAlive(x)
	runtime.GC()
	<-ch

	// Add a little sleep to wait for other finalizers.
	// TODO: Is there a better way?
	time.Sleep(time.Millisecond)
}

func TestGC(t *testing.T) {
	img := atlas.NewImage(16, 16, atlas.ImageTypeRegular)
	img.WritePixels(make([]byte, 4*16*16), image.Rect(0, 0, 16, 16))

	// Ensure other objects are GCed, as GC appends deferred functions for collected objects.
	ensureGC()

	// Get the difference of the number of deferred functions before and after img is GCed.
	c := atlas.DeferredFuncCountForTesting()
	runtime.KeepAlive(img)
	ensureGC()

	diff := atlas.DeferredFuncCountForTesting() - c
	if got, want := diff, 1; got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}
}

func TestDallocateUnmanagedImageBackends(t *testing.T) {
	const w, h = 16, 16
	img0 := atlas.NewImage(w, h, atlas.ImageTypeUnmanaged)
	img1 := atlas.NewImage(w, h, atlas.ImageTypeUnmanaged)

	// Call DrawTriangles to ensure the images are on backends.
	vs := quadVertices(w, h, 0, 0, 1)
	is := graphics.QuadIndices()
	dr := image.Rect(0, 0, w, h)
	sr := image.Rect(0, 0, w, h)
	img0.DrawTriangles([graphics.ShaderSrcImageCount]*atlas.Image{img1}, vs, is, graphicsdriver.BlendCopy, dr, [graphics.ShaderSrcImageCount]image.Rectangle{sr}, atlas.NearestFilterShader, nil)

	// Get the difference of the number of backends before and after the images are deallocated.
	c := atlas.BackendCountForTesting()
	img0.Deallocate()
	img1.Deallocate()

	diff := c - atlas.BackendCountForTesting()
	if got, want := diff, 2; got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}
}

// TODO: Add tests to extend image on an atlas out of the main loop
