package world

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

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

type cacheTheme struct{}

func (cacheTheme) ID() string                                 { return "cache" }
func (cacheTheme) Name() string                               { return "cache" }
func (cacheTheme) BackgroundColor() color.Color               { return color.RGBA{A: 255} }
func (cacheTheme) BackgroundImage() image.Image               { return nil }
func (cacheTheme) BackgroundTileMode() BackgroundTileMode     { return BackgroundTileNone }
func (cacheTheme) BackgroundScaleMode() BackgroundScaleMode   { return BackgroundScaleNone }
func (cacheTheme) BackgroundAnchorMode() BackgroundAnchorMode { return BackgroundAnchorWorld }
func (cacheTheme) PointStyle() Style                          { return Style{FillColor: color.RGBA{A: 255}, PointRadiusPx: 2} }
func (cacheTheme) LineStyle() Style                           { return Style{StrokeColor: color.RGBA{A: 255}, StrokeWidthPx: 1} }
func (cacheTheme) CircleStyle() Style {
	return Style{FillColor: color.RGBA{A: 255}, StrokeColor: color.RGBA{A: 255}, StrokeWidthPx: 1}
}
func (cacheTheme) PointClassOverride(PointClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}
func (cacheTheme) LineClassOverride(LineClassID) (StyleOverride, bool) { return StyleOverride{}, false }
func (cacheTheme) CircleClassOverride(CircleClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}

type cacheTheme2 struct{ cacheTheme }

func (cacheTheme2) ID() string   { return "cache2" }
func (cacheTheme2) Name() string { return "cache2" }
func (cacheTheme2) CircleStyle() Style {
	return Style{FillColor: color.RGBA{B: 200, A: 255}, StrokeColor: color.RGBA{A: 255}, StrokeWidthPx: 3}
}
func (cacheTheme2) PointClassOverride(PointClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}
func (cacheTheme2) LineClassOverride(LineClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}
func (cacheTheme2) CircleClassOverride(CircleClassID) (StyleOverride, bool) {
	return StyleOverride{}, false
}

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

	w := NewWorld(10, 10)
	w.SetTheme(cacheTheme{})

	before := w.styles.Count()

	white := color.RGBA{R: 255, G: 255, B: 255, A: 255}
	ov := StyleOverride{StrokeColor: white}

	id1, err := w.AddCircle(5, 5, 2, CircleWithStyleOverride(ov))
	require.NoError(t, err)
	id2, err := w.AddCircle(6, 5, 2, CircleWithStyleOverride(ov))
	require.NoError(t, err)

	c1 := w.objects[id1].(Circle)
	c2 := w.objects[id2].(Circle)
	require.Equal(t, c1.StyleID, c2.StyleID, "same override must reuse derived style ID")

	afterAdd := w.styles.Count()
	require.Equal(t, before+1, afterAdd, "only one derived style should be added for identical overrides")

	// Change theme: derived cache is cleared and new base IDs are created; override must still be applied,
	// and both objects should again share one derived style for the new base.
	w.SetTheme(cacheTheme2{})

	c1b := w.objects[id1].(Circle)
	c2b := w.objects[id2].(Circle)
	require.Equal(t, c1b.StyleID, c2b.StyleID)

	afterTheme := w.styles.Count()
	// Theme change creates 3 new theme default styles + 1 new derived for the override.
	require.GreaterOrEqual(t, afterTheme, afterAdd+4)
}