using System.Numerics;
using AcDream.App.Rendering;

namespace AcDream.App.Tests.Rendering;

public sealed class RetailAlphaQueueTests
{
    [Fact]
    public void Flush_InterleavesRenderersInDescendingCyptOrder()
    {
        var log = new List<string>();
        var objects = new RecordingSource("object", log);
        var particles = new RecordingSource("particle", log);
        var queue = new RetailAlphaQueue();

        queue.BeginFrame();
        queue.Submit(objects, token: 0, viewerDistance: 10f);    // near crystal
        queue.Submit(particles, token: 0, viewerDistance: 30f);  // far smoke
        queue.Submit(objects, token: 1, viewerDistance: 25f);
        queue.Submit(particles, token: 1, viewerDistance: 20f);
        queue.Submit(objects, token: 2, viewerDistance: 5f);
        queue.EndFrame();

        Assert.Equal(
            new[]
            {
                "particle:0",
                "object:1",
                "particle:1",
                "object:0",
                "object:2",
            },
            log);
        Assert.Equal(1, objects.ResetCount);
        Assert.Equal(1, particles.ResetCount);
        Assert.Equal(1, objects.PrepareCount);
        Assert.Equal(1, particles.PrepareCount);
    }

    [Fact]
    public void Flush_EqualDistancePreservesSubmissionOrderAcrossRenderers()
    {
        var log = new List<string>();
        var objects = new RecordingSource("object", log);
        var particles = new RecordingSource("particle", log);
        var queue = new RetailAlphaQueue();

        queue.BeginFrame();
        queue.Submit(objects, 7, 12f);
        queue.Submit(particles, 4, 12f);
        queue.Submit(objects, 8, 12f);
        queue.EndFrame();

        Assert.Equal(new[] { "object:7", "particle:4", "object:8" }, log);
    }

    [Fact]
    public void Flush_KeepsFrameOpenForPostDepthClearScope()
    {
        var log = new List<string>();
        var source = new RecordingSource("alpha", log);
        var queue = new RetailAlphaQueue();

        queue.BeginFrame();
        queue.Submit(source, 1, 8f);
        queue.Flush();

        Assert.True(queue.IsCollecting);
        Assert.Equal(0, queue.PendingCount);
        queue.Submit(source, 2, 3f);
        queue.EndFrame();

        Assert.False(queue.IsCollecting);
        Assert.Equal(new[] { "alpha:1", "alpha:2" }, log);
        Assert.Equal(2, source.ResetCount);
    }

    [Fact]
    public void Flush_BatchesOnlyAdjacentEntriesFromSameRenderer()
    {
        var log = new List<string>();
        var objects = new RecordingSource("object", log);
        var particles = new RecordingSource("particle", log);
        var queue = new RetailAlphaQueue();

        queue.BeginFrame();
        queue.Submit(objects, 0, 40f);
        queue.Submit(objects, 1, 35f);
        queue.Submit(particles, 0, 30f);
        queue.Submit(objects, 2, 25f);
        queue.EndFrame();

        Assert.Equal(new[] { 2, 1 }, objects.BatchSizes);
        Assert.Equal(new[] { 1 }, particles.BatchSizes);
    }

    [Fact]
    public void Flush_LargeInputMatchesStableDescendingRetailOrder()
    {
        var log = new List<string>();
        var source = new RecordingSource("alpha", log);
        var queue = new RetailAlphaQueue();
        var random = new Random(0xAC2013);
        float[] distances = new float[4_096];

        queue.BeginFrame();
        for (int i = 0; i < distances.Length; i++)
        {
            distances[i] = i % 127 switch
            {
                0 => float.NaN,
                1 => float.PositiveInfinity,
                2 => -0f,
                3 => -1f,
                _ => random.Next(0, 64),
            };
            queue.Submit(source, i, distances[i]);
        }
        queue.EndFrame();

        int[] expected = Enumerable.Range(0, distances.Length)
            .OrderByDescending(i => NormalizeForReference(distances[i]))
            .ToArray();
        Assert.Equal(expected, source.PreparedTokens);
    }

    [Fact]
    public void Flush_ExtremeFloatKeysMatchNormalizedRetailOrder()
    {
        var log = new List<string>();
        var source = new RecordingSource("alpha", log);
        var queue = new RetailAlphaQueue();
        float[] distances =
        [
            1f,
            float.BitIncrement(1f),
            float.BitDecrement(1f),
            float.Epsilon,
            float.MaxValue,
            0f,
            -0f,
            float.NaN,
            float.PositiveInfinity,
            float.NegativeInfinity,
            -float.Epsilon,
            1f,
        ];

        queue.BeginFrame();
        for (int i = 0; i < distances.Length; i++)
            queue.Submit(source, i, distances[i]);
        queue.EndFrame();

        int[] expected = Enumerable.Range(0, distances.Length)
            .OrderByDescending(i => NormalizeForReference(distances[i]))
            .ToArray();
        Assert.Equal(expected, source.PreparedTokens);
    }

    [Fact]
    public void Flush_EqualDistanceOrderStartsFreshInEachFrameScope()
    {
        var log = new List<string>();
        var source = new RecordingSource("alpha", log);
        var queue = new RetailAlphaQueue();

        queue.BeginFrame();
        queue.Submit(source, 1, 12f);
        queue.Submit(source, 2, 12f);
        queue.EndFrame();

        queue.BeginFrame();
        queue.Submit(source, 9, 12f);
        queue.Submit(source, 8, 12f);
        queue.EndFrame();

        Assert.Equal(
            ["alpha:1", "alpha:2", "alpha:9", "alpha:8"],
            log);
    }

    [Fact]
    public void ComputeViewerDistance_UsesTransformedGfxSortCenter()
    {
        // Retail CPhysicsPart::UpdateViewerDistance 0x0050E030 applies scale,
        // orientation, and translation to gfxobj.sort_center before CYpt.
        var model = Matrix4x4.CreateScale(2f)
                    * Matrix4x4.CreateRotationZ(MathF.PI / 2f)
                    * Matrix4x4.CreateTranslation(10f, 20f, 30f);
        Vector3 localSortCenter = new(1f, 0f, 0f);
        Vector3 camera = new(10f, 20f, 30f);

        float cypt = RetailAlphaOrdering.ComputeViewerDistance(
            localSortCenter,
            model,
            camera);

        Assert.Equal(2f, cypt, precision: 5);
    }

    private static float NormalizeForReference(float value)
        => float.IsFinite(value) && value > 0f ? value : 0f;

    private sealed class RecordingSource(string name, List<string> log) : IRetailAlphaDrawSource
    {
        public List<int> BatchSizes { get; } = new();
        public int ResetCount { get; private set; }
        public int PrepareCount { get; private set; }
        public IReadOnlyList<int> PreparedTokens => _prepared;
        private int[] _prepared = [];

        public void PrepareAlphaDraws(ReadOnlySpan<int> tokens)
        {
            PrepareCount++;
            _prepared = tokens.ToArray();
        }

        public void DrawPreparedAlphaBatch(int firstPreparedDraw, int drawCount)
        {
            BatchSizes.Add(drawCount);
            for (int i = 0; i < drawCount; i++)
                log.Add($"{name}:{_prepared[firstPreparedDraw + i]}");
        }

        public void ResetAlphaSubmissions() => ResetCount++;
    }
}