package world

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

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

type themeA struct{}

func (themeA) ID() string                                 { return "A" }
func (themeA) Name() string                               { return "A" }
func (themeA) BackgroundColor() color.Color               { return color.RGBA{A: 255} }
func (themeA) BackgroundImage() image.Image               { return nil }
func (themeA) BackgroundTileMode() BackgroundTileMode     { return BackgroundTileNone }
func (themeA) BackgroundScaleMode() BackgroundScaleMode   { return BackgroundScaleNone }
func (themeA) BackgroundAnchorMode() BackgroundAnchorMode { return BackgroundAnchorWorld }
func (themeA) PointStyle() Style {
	return Style{FillColor: color.RGBA{R: 10, A: 255}, PointRadiusPx: 2}
}
func (themeA) LineStyle() Style {
	return Style{StrokeColor: color.RGBA{G: 10, A: 255}, StrokeWidthPx: 1}
}
func (themeA) CircleStyle() Style {
	return Style{FillColor: color.RGBA{B: 10, A: 255}, StrokeColor: color.RGBA{A: 255}, StrokeWidthPx: 1}
}
func (themeA) PointClassOverride(PointClassID) (StyleOverride, bool)   { return StyleOverride{}, false }
func (themeA) LineClassOverride(LineClassID) (StyleOverride, bool)     { return StyleOverride{}, false }
func (themeA) CircleClassOverride(CircleClassID) (StyleOverride, bool) { return StyleOverride{}, false }

type themeB struct{}

func (themeB) ID() string                                 { return "B" }
func (themeB) Name() string                               { return "B" }
func (themeB) BackgroundColor() color.Color               { return color.RGBA{A: 255} }
func (themeB) BackgroundImage() image.Image               { return nil }
func (themeB) BackgroundTileMode() BackgroundTileMode     { return BackgroundTileNone }
func (themeB) BackgroundScaleMode() BackgroundScaleMode   { return BackgroundScaleNone }
func (themeB) BackgroundAnchorMode() BackgroundAnchorMode { return BackgroundAnchorWorld }
func (themeB) PointStyle() Style {
	return Style{FillColor: color.RGBA{R: 99, A: 255}, PointRadiusPx: 5}
}
func (themeB) LineStyle() Style {
	return Style{StrokeColor: color.RGBA{G: 99, A: 255}, StrokeWidthPx: 3}
}
func (themeB) CircleStyle() Style {
	return Style{FillColor: color.RGBA{B: 99, A: 255}, StrokeColor: color.RGBA{A: 255}, StrokeWidthPx: 4}
}
func (themeB) PointClassOverride(PointClassID) (StyleOverride, bool)   { return StyleOverride{}, false }
func (themeB) LineClassOverride(LineClassID) (StyleOverride, bool)     { return StyleOverride{}, false }
func (themeB) CircleClassOverride(CircleClassID) (StyleOverride, bool) { return StyleOverride{}, false }

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

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

	id, err := w.AddPoint(1, 1) // default => theme-managed
	require.NoError(t, err)

	p := w.objects[id].(Point)
	styleBefore := p.StyleID

	w.SetTheme(themeB{})

	p2 := w.objects[id].(Point)
	styleAfter := p2.StyleID

	require.NotEqual(t, styleBefore, styleAfter)

	s, ok := w.styles.Get(styleAfter)
	require.True(t, ok)
	// From themeB point style
	require.Equal(t, 5.0, s.PointRadiusPx)
}

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

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

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

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

	c1 := w.objects[id].(Circle)
	s1, ok := w.styles.Get(c1.StyleID)
	require.True(t, ok)

	// Stroke overridden to white, fill from themeA (B=10).
	require.Equal(t, uint32(0xffff), alphaOf(s1.StrokeColor))
	require.Equal(t, u16FromU8(10), blueOf(s1.FillColor))

	w.SetTheme(themeB{})

	c2 := w.objects[id].(Circle)
	s2, ok := w.styles.Get(c2.StyleID)
	require.True(t, ok)

	// Still white stroke, but fill should now come from themeB (B=99).
	require.Equal(t, uint32(0xffff), alphaOf(s2.StrokeColor))
	require.Equal(t, u16FromU8(99), blueOf(s2.FillColor))
}

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

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

	sw := 2.0
	fixed := w.AddStyleCircle(StyleOverride{
		FillColor:     color.RGBA{A: 0},
		StrokeColor:   color.RGBA{R: 1, A: 255},
		StrokeWidthPx: &sw,
	})

	id, err := w.AddCircle(5, 5, 2, CircleWithStyleID(fixed))
	require.NoError(t, err)

	c1 := w.objects[id].(Circle)
	require.Equal(t, fixed, c1.StyleID)

	w.SetTheme(themeB{})

	c2 := w.objects[id].(Circle)
	require.Equal(t, fixed, c2.StyleID)
}

func alphaOf(c color.Color) uint32 {
	_, _, _, a := c.RGBA()
	return a
}
func blueOf(c color.Color) uint32 {
	_, _, b, _ := c.RGBA()
	return b
}

// u16FromU8 converts an 8-bit channel value to the 16-bit value returned by color.Color.RGBA().
// The standard conversion is v * 257 (0x0101) so that 0xAB becomes 0xABAB.
func u16FromU8(v uint8) uint32 {
	return uint32(v) * 257
}