using System.Runtime.InteropServices;
using AcDream.App.Rendering;

namespace AcDream.App.Tests.Rendering;

public sealed class ParticleBindlessInstanceTests
{
    [Fact]
    public void BillboardGpuInstance_MatchesVertexAttributeAbi()
    {
        Assert.Equal(72, Marshal.SizeOf<ParticleRenderer.BillboardGpuInstance>());
        Assert.Equal(
            new IntPtr(64),
            Marshal.OffsetOf<ParticleRenderer.BillboardGpuInstance>(
                nameof(ParticleRenderer.BillboardGpuInstance.TextureHandleLow)));
        Assert.Equal(
            new IntPtr(68),
            Marshal.OffsetOf<ParticleRenderer.BillboardGpuInstance>(
                nameof(ParticleRenderer.BillboardGpuInstance.TextureHandleHigh)));
    }

    [Fact]
    public void BillboardShaders_ConsumeOneBindlessTextureHandlePerInstance()
    {
        string shadersDirectory = Path.Combine(
            AppContext.BaseDirectory,
            "Rendering",
            "Shaders");
        string vertex = File.ReadAllText(Path.Combine(shadersDirectory, "particle.vert"));
        string fragment = File.ReadAllText(Path.Combine(shadersDirectory, "particle.frag"));

        Assert.Contains("layout(location = 6) in uvec2 aTextureHandle;", vertex);
        Assert.Contains("flat out uvec2 vTextureHandle;", vertex);
        Assert.Contains("#extension GL_ARB_bindless_texture : require", fragment);
        Assert.Contains("sampler2DArray(vTextureHandle)", fragment);
        Assert.DoesNotContain("uniform sampler2D uParticleTexture", fragment);
    }
}