using System.Linq;
using AcDream.App.Rendering;
using AcDream.App.Rendering.Gpu;
using AcDream.App.Tests.Rendering.Gpu;
using Xunit;

namespace AcDream.App.Tests.Rendering;

/// <summary>
/// Campaign LA gate round 2 (register AD-98 filtering fidelity, 2026-08-15):
/// pins <see cref="TextureCache.GetOrCreateLinearUiTwin"/> — the GPU-table half
/// of the fixed-canvas jagged-text fix (<c>TextRendererLinearTwinTests</c> pins
/// the renderer-side handle swap this method feeds).
///
/// <para>
/// Uses <see cref="TextureCache.UploadRgba8"/> rather than
/// <see cref="TextureCache.GetOrUploadRenderSurface"/> to get a nearest-sampled
/// handle without any DAT fixture — <c>UploadRgba8</c> never touches the injected
/// <c>IDatReaderWriter</c>, so the simple <c>TextureCache(device, dats)</c>
/// constructor can run with <see langword="null"/>/<see cref="RecordingGpuDevice"/>
/// and no live GPU, matching this suite's existing renderer-test-double idiom.
/// </para>
/// </summary>
public sealed class TextureCacheLinearTwinTests
{
    private static (RecordingGpuDevice device, TextureCache cache) Build()
    {
        var device = new RecordingGpuDevice();
        // UploadRgba8/GetOrCreateLinearUiTwin/Dispose never touch the dats
        // reference — see the class doc comment.
        var cache = new TextureCache(device, dats: null!);
        // RecordingGpuDevice's own constructor registers a 1x1 default-white
        // placeholder (DefaultTextureSlot) — clear that registration out of the
        // recorded call log so each test's assertions only see the
        // registrations IT caused. Clear() only wipes the call log, not the
        // slot/sampler state, so DefaultTextureSlot itself is untouched.
        device.Clear();
        return (device, cache);
    }

    [Fact]
    public void UnknownHandle_ReturnsUnchanged()
    {
        // Chrome/background art (never registered nearest) and any handle this
        // cache never saw (including UiTextureTableHandle.None == 0) pass
        // through untouched — there is nothing to swap.
        (_, TextureCache cache) = Build();

        Assert.Equal(0u, cache.GetOrCreateLinearUiTwin(0u));
        Assert.Equal(12345u, cache.GetOrCreateLinearUiTwin(12345u));
    }

    [Fact]
    public void NearestHandle_GetsADifferentTwinHandle_SampledLinear()
    {
        (RecordingGpuDevice device, TextureCache cache) = Build();
        byte[] rgba = new byte[4 * 4 * 4];
        uint nearestHandle = cache.UploadRgba8(rgba, 4, 4, nearest: true);

        uint twinHandle = cache.GetOrCreateLinearUiTwin(nearestHandle);

        Assert.NotEqual(0u, twinHandle);
        Assert.NotEqual(nearestHandle, twinHandle);

        // The SECOND registration recorded against the device (the first is the
        // original nearest upload) must carry a linear filter — the whole point
        // of the twin.
        var registrations = device.OfKind<GpuRecordedTextureRegistration>().ToList();
        Assert.Equal(2, registrations.Count);
        Assert.Equal(GpuFilter.Nearest, registrations[0].Sampler.MinFilter);
        Assert.Equal(GpuFilter.Linear, registrations[1].Sampler.MinFilter);
        Assert.Equal(GpuFilter.Linear, registrations[1].Sampler.MagFilter);

        // Both registrations name the SAME underlying texture — the twin reuses
        // the original decoded pixels rather than re-uploading.
        Assert.Equal(registrations[0].TextureName, registrations[1].TextureName);
    }

    [Fact]
    public void NearestHandle_RepeatedRequest_ReturnsTheSameCachedTwin()
    {
        (RecordingGpuDevice device, TextureCache cache) = Build();
        byte[] rgba = new byte[4 * 4 * 4];
        uint nearestHandle = cache.UploadRgba8(rgba, 4, 4, nearest: true);

        uint first = cache.GetOrCreateLinearUiTwin(nearestHandle);
        uint second = cache.GetOrCreateLinearUiTwin(nearestHandle);

        Assert.Equal(first, second);
        // Exactly one twin registration — the second request must not create
        // another device-table slot.
        Assert.Equal(2, device.OfKind<GpuRecordedTextureRegistration>().Count());
    }

    [Fact]
    public void NonNearestUpload_HasNoTwin()
    {
        // UploadRgba8's default (nearest: false) mirrors chrome/background art:
        // it already samples GpuSamplerDescription.WorldRepeat (linear), so it
        // never enters the nearest-source table and GetOrCreateLinearUiTwin
        // hands the same handle straight back.
        (_, TextureCache cache) = Build();
        byte[] rgba = new byte[4 * 4 * 4];
        uint linearHandle = cache.UploadRgba8(rgba, 4, 4, nearest: false);

        Assert.Equal(linearHandle, cache.GetOrCreateLinearUiTwin(linearHandle));
    }

    [Fact]
    public void Dispose_ReleasesTheTwinSlot()
    {
        (RecordingGpuDevice device, TextureCache cache) = Build();
        byte[] rgba = new byte[4 * 4 * 4];
        uint nearestHandle = cache.UploadRgba8(rgba, 4, 4, nearest: true);
        uint twinHandle = cache.GetOrCreateLinearUiTwin(nearestHandle);
        GpuTextureSlot twinSlot = UiTextureTableHandle.ToSlot(twinHandle);

        cache.Dispose();

        Assert.Contains(
            device.OfKind<GpuRecordedTextureRelease>(),
            release => release.Slot == twinSlot.Index);
    }
}