using AcDream.App.Rendering;
using Xunit;

namespace AcDream.App.Tests.Rendering;

/// <summary>
/// Campaign V slice V6l: the portal depth mask is the one renderer whose two arms
/// do NOT share a shader source, and this is the tripwire that stops them
/// drifting.
///
/// <para>Every other RHI arm in the campaign compiles the same GLSL file the GL
/// arm does. This one cannot: its clip planes would have to travel in the
/// <c>TerrainClip</c> uniform block at binding 2, and on GL that binding is held
/// globally by <c>ClipFrame</c> for terrain — a portal draw that rebound it would
/// leave every later terrain draw in the frame reading the wrong region. So the
/// GL arm keeps its inline program, the RHI arm compiles
/// <c>Rendering/Shaders/portal_depth.vert</c>, and the numbers that decide where
/// depth lands are asserted to appear in both.</para>
///
/// <para>Deleted with the GL arm at V11, when the inline string goes.</para>
/// </summary>
public class PortalDepthShaderParityTests
{
    private static string PortalDepthVertexSource() =>
        File.ReadAllText(Path.Combine(
            AppContext.BaseDirectory,
            "Rendering",
            "Shaders",
            "portal_depth.vert"));

    [Fact]
    public void BothArmsPunchWithRetailsFarZConstant()
    {
        // 0.99999988 is retail's own value at the tail of
        // D3DPolyRender::DrawPortalPolyInternal (0x0059bc90). It decides where
        // the punched depth lands, so the two arms agreeing on it is the whole
        // point of this file.
        const string FarZ = "0.99999988";
        Assert.Contains(FarZ, PortalDepthMaskRenderer.VertSrc, StringComparison.Ordinal);
        Assert.Contains(FarZ, PortalDepthVertexSource(), StringComparison.Ordinal);
    }

    [Fact]
    public void BothArmsApplyTheSameEyeCappedMarkBias()
    {
        // #129's capped bias: min(bias, cap / max(w*w, 1e-6)), then z -= bias*w.
        // Spelled with different identifier names on the two arms — the RHI arm
        // reads the shared push block's uParamA/uParamB — so the assertion is on
        // the SHAPE that decides the result rather than on the text.
        string rhi = PortalDepthVertexSource();
        Assert.Contains("max(clipPos.w * clipPos.w, 1e-6)", PortalDepthMaskRenderer.VertSrc, StringComparison.Ordinal);
        Assert.Contains("max(clipPos.w * clipPos.w, 1e-6)", rhi, StringComparison.Ordinal);
        Assert.Contains("clipPos.z -= biasNdc * clipPos.w", PortalDepthMaskRenderer.VertSrc, StringComparison.Ordinal);
        Assert.Contains("clipPos.z -= biasNdc * clipPos.w", rhi, StringComparison.Ordinal);
    }

    [Fact]
    public void BothArmsClipAgainstEightHalfPlanes()
    {
        // The plane budget is ClipFrame.MaxPlanes and GL's guaranteed
        // GL_MAX_CLIP_DISTANCES; a shader that looped to a different number
        // would clip a differently-shaped region than the one the CPU published.
        Assert.Equal(8, ClipFrame.MaxPlanes);
        Assert.Contains("for (int i = 0; i < 8; i++)", PortalDepthMaskRenderer.VertSrc, StringComparison.Ordinal);
        Assert.Contains("for (int i = 0; i < 8; i++)", PortalDepthVertexSource(), StringComparison.Ordinal);
    }

    [Fact]
    public void TheRhiArmReadsTheClipPlanesFromTheSharedTerrainClipBlock()
    {
        string rhi = PortalDepthVertexSource();
        Assert.Contains("uniform TerrainClip", rhi, StringComparison.Ordinal);
        Assert.Contains("binding = 2", rhi, StringComparison.Ordinal);
        // And the block is the one ClipFrame already packs for terrain and sky:
        // an int count padded to 16 bytes, then eight vec4 planes.
        Assert.Equal(144, ClipFrame.TerrainUboBytes);
        Assert.Equal(2u, ClipFrame.TerrainClipUboBinding);
    }
}