using AcDream.App.Rendering;
using Xunit;

namespace AcDream.App.Tests.Rendering;

/// <summary>
/// Campaign V slice V2 (2026-07-27): pure-CPU proof of
/// <see cref="GlBindlessHandleTable"/>'s bookkeeping — the handle→slot
/// allocator each Campaign V-touched renderer (WbDrawDispatcher,
/// EnvCellRenderer, TerrainModernRenderer, ParticleRenderer) owns to back its
/// own binding=9 GL texture table.
/// </summary>
public class GlBindlessHandleTableTests
{
    [Fact]
    public void GetOrAdd_FirstHandle_AssignsSlotZero_AndMarksDirty()
    {
        var table = new GlBindlessHandleTable();

        uint slot = table.GetOrAdd(0xDEADBEEFu);

        Assert.Equal(0u, slot);
        Assert.True(table.Dirty);
        Assert.Equal(new ulong[] { 0xDEADBEEFu }, table.Handles.ToArray());
    }

    [Fact]
    public void GetOrAdd_SameHandleTwice_ReturnsSameSlot_AndDoesNotDuplicate()
    {
        var table = new GlBindlessHandleTable();

        uint first = table.GetOrAdd(111ul);
        table.MarkFlushed();
        uint second = table.GetOrAdd(111ul);

        Assert.Equal(first, second);
        Assert.False(table.Dirty); // no NEW handle was registered
        Assert.Single(table.Handles.ToArray());
    }

    [Fact]
    public void GetOrAdd_DistinctHandles_AssignStableIncreasingSlots()
    {
        var table = new GlBindlessHandleTable();

        uint a = table.GetOrAdd(1ul);
        uint b = table.GetOrAdd(2ul);
        uint c = table.GetOrAdd(3ul);
        // Re-querying an already-registered handle must not shift anyone else's slot.
        uint aAgain = table.GetOrAdd(1ul);

        Assert.Equal(0u, a);
        Assert.Equal(1u, b);
        Assert.Equal(2u, c);
        Assert.Equal(a, aAgain);
        Assert.Equal(new ulong[] { 1ul, 2ul, 3ul }, table.Handles.ToArray());
    }

    [Fact]
    public void ZeroHandle_IsRegisteredLikeAnyOther_NotSpecialCased()
    {
        // The pre-V2 behaviour let a batch/pass carry a literal zero bindless
        // handle through to the shader unchanged (an existing "no texture"
        // edge case some batches hit). V2 must reproduce that bit-for-bit: a
        // zero handle gets a real slot whose table entry is uvec2(0,0) — the
        // same value the shader would have received directly before V2.
        var table = new GlBindlessHandleTable();

        uint slot = table.GetOrAdd(0ul);

        Assert.Equal(0u, table.Handles[(int)slot]);
    }

    [Fact]
    public void MarkFlushed_ClearsDirty_UntilNextNewHandle()
    {
        var table = new GlBindlessHandleTable();
        table.GetOrAdd(42ul);
        Assert.True(table.Dirty);

        table.MarkFlushed();
        Assert.False(table.Dirty);

        table.GetOrAdd(42ul); // already known — must NOT re-dirty
        Assert.False(table.Dirty);

        table.GetOrAdd(43ul); // genuinely new — must re-dirty
        Assert.True(table.Dirty);
    }

    [Fact]
    public void GetOrAdd_GrowsPastInitialCapacity_WithoutLosingEarlierSlots()
    {
        var table = new GlBindlessHandleTable();
        const int count = 200; // exceeds the 64-entry initial backing array
        for (int i = 0; i < count; i++)
        {
            uint slot = table.GetOrAdd((ulong)i + 1000ul);
            Assert.Equal((uint)i, slot);
        }

        for (int i = 0; i < count; i++)
            Assert.Equal((ulong)i + 1000ul, table.Handles[i]);
    }
}