using System.Collections.Generic;
using System.Numerics;
using AcDream.App.Rendering.Wb;
using AcDream.Core.Meshing;
using Xunit;

namespace AcDream.Core.Tests.Rendering.Wb;

public class EntityClassificationCacheTests
{
    [Fact]
    public void TryGet_EmptyCache_ReturnsFalse()
    {
        var cache = new EntityClassificationCache();
        bool found = cache.TryGet(entityId: 42, out var entry);
        Assert.False(found);
        Assert.Null(entry);
    }

    [Fact]
    public void Populate_ThenTryGet_ReturnsBatchesInOrder()
    {
        var cache = new EntityClassificationCache();
        var batches = new[]
        {
            MakeCachedBatch(ibo: 1, firstIndex: 0, indexCount: 6, texHandle: 0xAA),
            MakeCachedBatch(ibo: 1, firstIndex: 6, indexCount: 6, texHandle: 0xBB),
        };

        cache.Populate(entityId: 100, landblockHint: 0xA9B40000u, batches);

        Assert.True(cache.TryGet(100, out var entry));
        Assert.NotNull(entry);
        Assert.Equal(100u, entry!.EntityId);
        Assert.Equal(0xA9B40000u, entry.LandblockHint);
        Assert.Equal(batches, entry.Batches);
    }

    [Fact]
    public void Populate_OverridesExistingEntry()
    {
        var cache = new EntityClassificationCache();
        cache.Populate(100, 0u, new[] { MakeCachedBatch(1, 0, 6, 0xAA) });
        cache.Populate(100, 0u, new[] { MakeCachedBatch(2, 0, 12, 0xCC) });

        Assert.True(cache.TryGet(100, out var entry));
        Assert.NotNull(entry);
        Assert.Single(entry!.Batches);
        Assert.Equal(0xCCu, entry.Batches[0].BindlessTextureHandle);
    }

    [Fact]
    public void Count_TracksLiveEntries()
    {
        var cache = new EntityClassificationCache();
        Assert.Equal(0, cache.Count);

        cache.Populate(1, 0u, new[] { MakeCachedBatch(1, 0, 6, 0xAA) });
        Assert.Equal(1, cache.Count);

        cache.Populate(2, 0u, new[] { MakeCachedBatch(2, 0, 6, 0xAA) });
        Assert.Equal(2, cache.Count);

        // Re-populate same id — should not double-count.
        cache.Populate(1, 0u, new[] { MakeCachedBatch(3, 0, 6, 0xBB) });
        Assert.Equal(2, cache.Count);
    }

    [Fact]
    public void Populate_WithEmptyBatches_StoresEmptyEntry()
    {
        var cache = new EntityClassificationCache();
        cache.Populate(entityId: 7, landblockHint: 0u, System.Array.Empty<CachedBatch>());

        Assert.True(cache.TryGet(7, out var entry));
        Assert.NotNull(entry);
        Assert.Empty(entry!.Batches);
    }

    [Fact]
    public void Populate_SetupMultiPart_StoresFlatBatchPerSubPart()
    {
        // Synthetic Setup with 3 subParts × 2 batches each = 6 flat entries.
        // This pins the spec §3 Q4 decision: pre-flatten Setup multi-parts at
        // populate time so the per-frame hot path is branchless.
        var cache = new EntityClassificationCache();
        var batches = new CachedBatch[6];
        for (int subPart = 0; subPart < 3; subPart++)
        for (int b = 0; b < 2; b++)
        {
            batches[subPart * 2 + b] = MakeCachedBatch(
                ibo: (uint)(subPart + 1),
                firstIndex: (uint)(b * 6),
                indexCount: 6,
                texHandle: (ulong)(0x100 + subPart * 2 + b));
        }
        cache.Populate(99, 0u, batches);

        Assert.True(cache.TryGet(99, out var entry));
        Assert.NotNull(entry);
        Assert.Equal(6, entry!.Batches.Length);
        Assert.Equal(0x100u, entry.Batches[0].BindlessTextureHandle);
        Assert.Equal(0x105u, entry.Batches[5].BindlessTextureHandle);
    }

    private static CachedBatch MakeCachedBatch(
        uint ibo, uint firstIndex, int indexCount, ulong texHandle)
    {
        var key = new GroupKey(
            Ibo: ibo,
            FirstIndex: firstIndex,
            BaseVertex: 0,
            IndexCount: indexCount,
            BindlessTextureHandle: texHandle,
            TextureLayer: 0,
            Translucency: TranslucencyKind.Opaque);
        return new CachedBatch(key, texHandle, Matrix4x4.Identity);
    }
}