package world

import (
	"image"
	"image/color"
	"testing"

	"github.com/stretchr/testify/require"
)

type bgTheme struct {
	img image.Image
}

func (t bgTheme) ID() string   { return "bg" }
func (t bgTheme) Name() string { return "bg" }

func (t bgTheme) BackgroundColor() color.Color { return color.RGBA{A: 255} }
func (t bgTheme) BackgroundImage() image.Image { return t.img }

func (t bgTheme) BackgroundTileMode() BackgroundTileMode     { return BackgroundTileRepeat }
func (t bgTheme) BackgroundScaleMode() BackgroundScaleMode   { return BackgroundScaleNone }
func (t bgTheme) BackgroundAnchorMode() BackgroundAnchorMode { return BackgroundAnchorViewport }

func (t bgTheme) PointStyle() Style { return Style{FillColor: color.RGBA{A: 255}, PointRadiusPx: 2} }
func (t bgTheme) LineStyle() Style  { return Style{StrokeColor: color.RGBA{A: 255}, StrokeWidthPx: 1} }
func (t bgTheme) CircleStyle() Style {
	return Style{FillColor: color.RGBA{A: 255}, StrokeColor: color.RGBA{A: 255}, StrokeWidthPx: 1}
}

func (t bgTheme) PointClassOverride(PointClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}
func (t bgTheme) LineClassOverride(LineClassID) (StyleOverride, bool) { return StyleOverride{}, false }
func (t bgTheme) CircleClassOverride(CircleClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}

func TestRender_BackgroundImage_DrawsBeforePrimitives_FullRedraw(t *testing.T) {
	t.Parallel()

	w := NewWorld(10, 10)
	w.resetGrid(2 * SCALE)

	// 4x4 opaque image
	img := image.NewRGBA(image.Rect(0, 0, 4, 4))
	w.SetTheme(bgTheme{img: img})

	_, err := w.AddPoint(5, 5)
	require.NoError(t, err)
	for _, obj := range w.objects {
		w.indexObject(obj)
	}

	params := RenderParams{
		ViewportWidthPx:  10,
		ViewportHeightPx: 10,
		MarginXPx:        2,
		MarginYPx:        2,
		CameraXWorldFp:   5 * SCALE,
		CameraYWorldFp:   5 * SCALE,
		CameraZoom:       1.0,
	}

	d := &fakePrimitiveDrawer{}
	require.NoError(t, w.Render(d, params))

	cmds := d.Commands()
	iClear := indexOfFirstName(cmds, "ClearAllTo")
	iBg := indexOfFirstName(cmds, "DrawImage")
	iPrim := indexOfFirstName(cmds, "AddPoint")

	require.NotEqual(t, -1, iClear)
	require.NotEqual(t, -1, iBg)
	require.NotEqual(t, -1, iPrim)
	require.Less(t, iClear, iBg)
	require.Less(t, iBg, iPrim)
}

func TestRender_BackgroundImage_RedrawnInDirtyRects_OnIncrementalShift(t *testing.T) {
	t.Parallel()

	w := NewWorld(10, 10)
	w.resetGrid(2 * SCALE)

	img := image.NewRGBA(image.Rect(0, 0, 4, 4))
	w.SetTheme(bgTheme{img: img})

	// Ensure state: first full render commits.
	params := RenderParams{
		ViewportWidthPx:  10,
		ViewportHeightPx: 10,
		MarginXPx:        2,
		MarginYPx:        2,
		CameraXWorldFp:   5 * SCALE,
		CameraYWorldFp:   5 * SCALE,
		CameraZoom:       1.0,
		Options: &RenderOptions{
			Incremental: &IncrementalPolicy{
				AllowShiftOnly:   false,
				MaxCatchUpAreaPx: 0,
				RenderBudgetMs:   0,
				CoalesceUpdates:  false,
			},
		},
	}

	d := &fakePrimitiveDrawer{}
	require.NoError(t, w.Render(d, params))

	// Move camera by 1px right in world (zoom=1 => 1px == 1 unit).
	params2 := params
	params2.CameraXWorldFp += 1 * SCALE

	d2 := &fakePrimitiveDrawer{}
	require.NoError(t, w.Render(d2, params2))

	// In incremental shift path we must see ClearRectTo and DrawImage.
	require.NotEmpty(t, d2.CommandsByName("CopyShift"))
	require.NotEmpty(t, d2.CommandsByName("ClearRectTo"))
	require.NotEmpty(t, d2.CommandsByName("DrawImage"))
}