using System;
using AcDream.App.Rendering.Gpu;
using AcDream.App.Rendering.Gpu.Vk;
using Silk.NET.Vulkan;

namespace AcDream.App.Tests.Rendering.Gpu.Vk;

/// <summary>
/// Campaign V slice V6c — the coordinate reconciliation (plan §3.3, §4.7,
/// §4.10).
///
/// <para>Renderers speak GL: viewport origin bottom-left, front faces
/// counter-clockwise. The Vulkan backend renders with a NEGATIVE viewport
/// height, which mirrors framebuffer space vertically and therefore also
/// reverses winding, so the front face is inverted to compensate. The two flips
/// are exact inverses and must always travel together — which is why they live
/// in one file, and why these tests assert them together.</para>
///
/// <para>The scissor is the trap. It does NOT flip with the viewport:
/// <c>vkCmdSetScissor</c> is always top-left-origin regardless of viewport sign,
/// while <c>NdcScissorRect.ToPixels</c> emits GL bottom-left rectangles. The V3
/// audit flagged this explicitly as a V6 acceptance item, and getting it wrong
/// shows up as a doorway aperture clipped from the wrong edge — which only a
/// scene containing one would reveal.</para>
/// </summary>
public sealed class VulkanViewportMappingTests
{
    [Fact]
    public void FullViewportBecomesANegativeHeightRectangleAnchoredAtTheBottom()
    {
        Viewport viewport = VulkanViewportMapping.ToVulkan(0, 0, 1280, 720, attachmentHeight: 720);

        Assert.Equal(0f, viewport.X);
        // Y is the BOTTOM edge in Vulkan's top-left space, and the height runs
        // upward from it. Together they mirror clip space.
        Assert.Equal(720f, viewport.Y);
        Assert.Equal(1280f, viewport.Width);
        Assert.Equal(-720f, viewport.Height);
        Assert.Equal(0f, viewport.MinDepth);
        Assert.Equal(1f, viewport.MaxDepth);
    }

    [Fact]
    public void AnOffsetViewportKeepsItsGlBottomLeftMeaning()
    {
        // A 100x50 viewport whose bottom edge sits 30 px above the bottom of a
        // 720 px attachment.
        Viewport viewport = VulkanViewportMapping.ToVulkan(10, 30, 100, 50, attachmentHeight: 720);

        Assert.Equal(10f, viewport.X);
        Assert.Equal(690f, viewport.Y);
        Assert.Equal(-50f, viewport.Height);
    }

    [Fact]
    public void ScissorFlipsAgainstTheAttachmentBecauseTheViewportSignDoesNotDoItForUs()
    {
        // GL rectangle: 100 px wide, 50 px tall, bottom edge 30 px up.
        Rect2D scissor = VulkanViewportMapping.ScissorToVulkan(10, 30, 100, 50, attachmentHeight: 720);

        Assert.Equal(10, scissor.Offset.X);
        // Top edge measured from the top: 720 - (30 + 50).
        Assert.Equal(640, scissor.Offset.Y);
        Assert.Equal(100u, scissor.Extent.Width);
        Assert.Equal(50u, scissor.Extent.Height);
    }

    [Fact]
    public void AFullAttachmentScissorIsUnchangedByTheFlip()
    {
        Rect2D scissor = VulkanViewportMapping.ScissorToVulkan(0, 0, 1280, 720, attachmentHeight: 720);

        Assert.Equal(0, scissor.Offset.X);
        Assert.Equal(0, scissor.Offset.Y);
        Assert.Equal(1280u, scissor.Extent.Width);
        Assert.Equal(720u, scissor.Extent.Height);
    }

    [Fact]
    public void AScissorStraddlingTheTopEdgeIsClampedRatherThanRejected()
    {
        // Bottom edge 700 px up in a 720 px attachment, 50 px tall: 30 px of it
        // is off the top. GL silently clips this; a driver error here would turn
        // a harmless off-screen aperture into a crash.
        Rect2D scissor = VulkanViewportMapping.ScissorToVulkan(0, 700, 100, 50, attachmentHeight: 720);

        Assert.Equal(0, scissor.Offset.Y);
        Assert.Equal(20u, scissor.Extent.Height);
    }

    /// <summary>
    /// Campaign V slice V6j: the winding a renderer declares is the winding
    /// Vulkan gets. V6c inverted it on the standard negative-viewport argument;
    /// the world arm — the mapping's first culling consumer — measured that the
    /// inversion culls terrain outright and turns every closed building shell
    /// inside-out. See <c>VulkanViewportMapping</c>'s remarks for the captures.
    /// </summary>
    [Fact]
    public void FrontFacePassesThroughSoRenderersDeclareTheGlWinding()
    {
        Assert.Equal(
            FrontFace.CounterClockwise,
            VulkanViewportMapping.ToVulkan(GpuFrontFace.CounterClockwise));
        Assert.Equal(
            FrontFace.Clockwise,
            VulkanViewportMapping.ToVulkan(GpuFrontFace.Clockwise));
    }

    [Fact]
    public void TheViewportFlipTravelsAloneAndTheWindingIsUntouched()
    {
        // The viewport still mirrors — that is what puts GL-authored geometry
        // the right way up with no matrix change. What it does NOT do is drag a
        // winding inversion along with it. A later change that reintroduces one
        // fails here and, more usefully, fails visibly on any single-sided
        // surface.
        Viewport once = VulkanViewportMapping.ToVulkan(0, 0, 640, 480, attachmentHeight: 480);
        Assert.Equal(-480f, once.Height);
        Assert.Equal(480f, once.Y);

        Assert.Equal(
            FrontFace.CounterClockwise,
            VulkanViewportMapping.ToVulkan(GpuFrontFace.CounterClockwise));
    }

    [Fact]
    public void CullModesMapStraightAcross()
    {
        Assert.Equal(CullModeFlags.None, VulkanViewportMapping.ToVulkan(GpuCullMode.None));
        Assert.Equal(CullModeFlags.BackBit, VulkanViewportMapping.ToVulkan(GpuCullMode.Back));
        Assert.Equal(CullModeFlags.FrontBit, VulkanViewportMapping.ToVulkan(GpuCullMode.Front));
    }

    [Fact]
    public void AllThreeRetailBlendModesAreRepresentable()
    {
        Assert.Equal(
            (BlendFactor.SrcAlpha, BlendFactor.OneMinusSrcAlpha),
            VulkanViewportMapping.BlendFactorsOf(GpuBlendMode.StraightAlpha));
        Assert.Equal(
            (BlendFactor.SrcAlpha, BlendFactor.One),
            VulkanViewportMapping.BlendFactorsOf(GpuBlendMode.Additive));
        // Retail's third mode, found at slice V4c. Mapping it onto straight
        // alpha would have silently changed how every inverse-alpha surface
        // composites.
        Assert.Equal(
            (BlendFactor.OneMinusSrcAlpha, BlendFactor.SrcAlpha),
            VulkanViewportMapping.BlendFactorsOf(GpuBlendMode.InverseAlpha));
    }

    [Fact]
    public void IntegerVertexAttributesTakeAUintFormatNotANormalisedOne()
    {
        Assert.Equal(Format.R8G8B8A8Unorm, VulkanViewportMapping.ToVulkan(GpuVertexFormat.UByte4Normalized));
        // terrain_modern.vert reads locations 2-5 as uvec4; those packed bytes
        // carry terrain-type, road and split-direction codes, so normalising
        // them would not be an approximation - it would be garbage.
        Assert.Equal(Format.R8G8B8A8Uint, VulkanViewportMapping.ToVulkan(GpuVertexFormat.UByte4UInt));
    }

    [Fact]
    public void ResolveIsExpressedByAResolveTargetRatherThanAStoreOp()
    {
        // There is no VK_ATTACHMENT_STORE_OP_RESOLVE; a resolving attachment
        // discards its multisampled contents and names a resolve image instead.
        Assert.Equal(AttachmentStoreOp.DontCare, VulkanViewportMapping.ToVulkan(GpuStoreOp.Resolve));
        Assert.Equal(AttachmentStoreOp.Store, VulkanViewportMapping.ToVulkan(GpuStoreOp.Store));
        Assert.Equal(AttachmentStoreOp.DontCare, VulkanViewportMapping.ToVulkan(GpuStoreOp.DontCare));
    }

    [Fact]
    public void PipelineCacheHeaderValidationRejectsAnotherDevicesBlob()
    {
        byte[] uuid = new byte[16];
        for (int i = 0; i < 16; i++)
            uuid[i] = (byte)(i + 1);

        byte[] blob = new byte[64];
        BitConverter.GetBytes(32u).CopyTo(blob, 0);
        BitConverter.GetBytes(1u).CopyTo(blob, 4);
        BitConverter.GetBytes(0x1002u).CopyTo(blob, 8);
        BitConverter.GetBytes(0x7550u).CopyTo(blob, 12);
        uuid.CopyTo(blob, 16);

        Assert.NotNull(VulkanPipelineCache.ValidateHeader(blob, 0x1002, 0x7550, uuid));
        // A driver update changes the cache UUID, and feeding the old blob back
        // is exactly the case the header exists to catch.
        uuid[0] = 0xFF;
        Assert.Null(VulkanPipelineCache.ValidateHeader(blob, 0x1002, 0x7550, uuid));
    }

    [Fact]
    public void PipelineCacheHeaderValidationRejectsTruncatedAndForeignBlobs()
    {
        byte[] uuid = new byte[16];
        Assert.Null(VulkanPipelineCache.ValidateHeader(null, 1, 1, uuid));
        Assert.Null(VulkanPipelineCache.ValidateHeader(new byte[8], 1, 1, uuid));

        byte[] blob = new byte[32];
        BitConverter.GetBytes(32u).CopyTo(blob, 0);
        BitConverter.GetBytes(1u).CopyTo(blob, 4);
        BitConverter.GetBytes(0x8086u).CopyTo(blob, 8);
        Assert.Null(VulkanPipelineCache.ValidateHeader(blob, 0x1002, 0, uuid));
    }
}