package world

import (
	"image/color"
	"testing"

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

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

	dc := gg.NewContext(40, 20)
	d := &GGDrawer{DC: dc}

	// Fill background to white.
	d.ClearAllTo(color.RGBA{R: 255, G: 255, B: 255, A: 255})

	// Configure stroke to red and draw first line.
	d.SetStrokeColor(color.RGBA{R: 255, A: 255})
	d.SetLineWidth(2)
	d.AddLine(2, 5, 38, 5)
	d.Stroke()

	// Clear a rect in the middle with gray (must not affect stroke state).
	d.ClearRectTo(10, 0, 20, 20, color.RGBA{R: 200, G: 200, B: 200, A: 255})

	// Draw second line WITHOUT reapplying stroke style; it must still be red.
	d.AddLine(2, 15, 38, 15)
	d.Stroke()

	img := dc.Image()

	// Sample a pixel from the second line (y ~15). We expect red channel dominates.
	r, g, b, a := img.At(20, 15).RGBA()
	require.Greater(t, a, uint32(0), "pixel must not be fully transparent")
	require.Greater(t, r, g, "expected red-ish pixel after ClearRectTo")
	require.Greater(t, r, b, "expected red-ish pixel after ClearRectTo")
}