using AcDream.App.UI;

namespace AcDream.App.Tests.UI;

public class IconComposerTests
{
    private static byte[] Solid(int w, int h, byte r, byte g, byte b, byte a)
    {
        var px = new byte[w * h * 4];
        for (int i = 0; i < w * h; i++) { px[i*4]=r; px[i*4+1]=g; px[i*4+2]=b; px[i*4+3]=a; }
        return px;
    }

    [Fact]
    public void Compose_alphaOver_topOpaqueLayerWins()
    {
        var bottom = (Solid(2, 2, 255, 0, 0, 255), 2, 2); // red, opaque
        var top    = (Solid(2, 2, 0, 0, 255, 255), 2, 2); // blue, opaque
        var (rgba, w, h) = IconComposer.Compose(new[] { bottom, top });
        Assert.Equal(2, w); Assert.Equal(2, h);
        Assert.Equal(0,   rgba[0]); // R
        Assert.Equal(0,   rgba[1]); // G
        Assert.Equal(255, rgba[2]); // B — top layer won
        Assert.Equal(255, rgba[3]); // A
    }

    [Fact]
    public void Compose_alphaOver_transparentTopKeepsBottom()
    {
        var bottom = (Solid(1, 1, 255, 0, 0, 255), 1, 1);
        var top    = (Solid(1, 1, 0, 0, 255, 0), 1, 1); // fully transparent blue
        var (rgba, _, _) = IconComposer.Compose(new[] { bottom, top });
        Assert.Equal(255, rgba[0]); // bottom red preserved
        Assert.Equal(0,   rgba[2]);
    }
}