using System.Collections.Generic;
using System.Numerics;
using AcDream.App.Rendering;
using Xunit;

namespace AcDream.App.Tests.Rendering;

public class ClipFrameAssemblerTests
{
    private static ViewPolygon Square(float cx, float cy, float half) => new(new[]
    {
        new Vector2(cx - half, cy - half),
        new Vector2(cx + half, cy - half),
        new Vector2(cx + half, cy + half),
        new Vector2(cx - half, cy + half),
    });

    private static CellView ViewOf(params ViewPolygon[] polys)
    {
        var view = new CellView();
        foreach (var p in polys)
            view.Add(p);
        return view;
    }

    [Fact]
    public void TwoVisibleCells_PlusOutsideView_ProducesCorrectSlotMapAndCounts()
    {
        const uint cellA = 0xA9B40100;
        const uint cellB = 0xA9B40101;

        var pv = new PortalVisibilityFrame();
        pv.CellViews[cellA] = ViewOf(Square(-0.3f, 0f, 0.3f));
        pv.CellViews[cellB] = ViewOf(Square(0.3f, 0f, 0.2f));
        pv.OrderedVisibleCells.Add(cellA);
        pv.OrderedVisibleCells.Add(cellB);
        pv.OutsideView.Add(Square(0f, 0.5f, 0.25f));

        var asm = ClipFrameAssembler.Assemble(ClipFrame.NoClip(), pv);

        Assert.Equal(4, asm.Frame.SlotCount); // slot 0 + two cells + one outside slice
        Assert.Contains(cellA, asm.CellIdToSlot.Keys);
        Assert.Contains(cellB, asm.CellIdToSlot.Keys);
        Assert.NotEqual(0, asm.CellIdToSlot[cellA]);
        Assert.NotEqual(0, asm.CellIdToSlot[cellB]);
        Assert.NotEqual(asm.CellIdToSlot[cellA], asm.CellIdToSlot[cellB]);
        Assert.Equal(4, asm.PerCellPlaneCounts[cellA]);
        Assert.Equal(4, asm.PerCellPlaneCounts[cellB]);

        Assert.True(asm.OutdoorVisible);
        Assert.NotEqual(0, asm.OutdoorSlot);
        Assert.Single(asm.OutsideViewSlices);
        Assert.Equal(asm.OutdoorSlot, asm.OutsideViewSlices[0].Slot);
        Assert.Equal(TerrainClipMode.Planes, asm.TerrainMode);
        Assert.Equal(4, asm.OutsidePlaneCount);
        Assert.Equal(0, asm.ScissorFallbacks);
    }

    [Fact]
    public void NothingVisibleCell_IsExcludedFromSlotMap_AndNotAppended()
    {
        const uint cellA = 0xA9B40100;
        const uint cellB = 0xA9B40101;

        var pv = new PortalVisibilityFrame();
        pv.CellViews[cellA] = ViewOf(Square(0f, 0f, 0.3f));
        pv.CellViews[cellB] = new CellView();
        pv.OrderedVisibleCells.Add(cellA);
        pv.OrderedVisibleCells.Add(cellB);

        var asm = ClipFrameAssembler.Assemble(ClipFrame.NoClip(), pv);

        Assert.Equal(2, asm.Frame.SlotCount);
        Assert.Contains(cellA, asm.CellIdToSlot.Keys);
        Assert.DoesNotContain(cellB, asm.CellIdToSlot.Keys);
        Assert.False(asm.OutdoorVisible);
        Assert.Empty(asm.OutsideViewSlices);
        Assert.Equal(TerrainClipMode.Skip, asm.TerrainMode);
        Assert.Equal(0, asm.OutsidePlaneCount);
    }

    [Fact]
    public void OutsideViewMultiPolygon_PreservesRetailSlices()
    {
        const uint cellA = 0xA9B40100;

        var pv = new PortalVisibilityFrame();
        pv.CellViews[cellA] = ViewOf(Square(0f, 0f, 0.3f));
        pv.OrderedVisibleCells.Add(cellA);
        pv.OutsideView.Add(Square(-0.5f, 0f, 0.1f));
        pv.OutsideView.Add(Square(0.5f, 0f, 0.1f));

        var asm = ClipFrameAssembler.Assemble(ClipFrame.NoClip(), pv);

        Assert.True(asm.OutdoorVisible);
        Assert.NotEqual(0, asm.OutdoorSlot);
        Assert.Equal(2, asm.OutsideViewSlices.Length);
        Assert.NotEqual(asm.OutsideViewSlices[0].Slot, asm.OutsideViewSlices[1].Slot);
        Assert.Equal(TerrainClipMode.Planes, asm.TerrainMode);
        Assert.Equal(4, asm.OutsidePlaneCount);
        Assert.Equal(0, asm.ScissorFallbacks);
        Assert.Equal(4, asm.Frame.SlotCount); // slot 0 + cell + two outside slices
        Assert.Equal(Vector4.Zero, asm.TerrainScissorNdcAabb);
    }

    [Fact]
    public void CellMultiPolygonView_PreservesRetailViewSlices()
    {
        const uint cellA = 0xA9B40100;

        var pv = new PortalVisibilityFrame();
        pv.CellViews[cellA] = ViewOf(
            Square(-0.4f, 0f, 0.1f),
            Square(0.4f, 0f, 0.1f));
        pv.OrderedVisibleCells.Add(cellA);
        pv.OutsideView.Add(Square(0f, 0f, 0.3f));

        var asm = ClipFrameAssembler.Assemble(ClipFrame.NoClip(), pv);

        Assert.True(asm.CellIdToSlot[cellA] > 0);
        Assert.Equal(2, asm.CellIdToViewSlots[cellA].Length);
        Assert.Equal(2, asm.CellIdToViewSlices[cellA].Length);
        Assert.NotEqual(asm.CellIdToViewSlots[cellA][0], asm.CellIdToViewSlots[cellA][1]);
        Assert.Equal(4, asm.PerCellPlaneCounts[cellA]);
        Assert.Single(asm.OutsideViewSlices);
        Assert.Equal(4, asm.Frame.SlotCount); // slot 0 + two cell slices + outside slice
        Assert.Equal(0, asm.ScissorFallbacks);
        Assert.Equal(TerrainClipMode.Planes, asm.TerrainMode);
    }

    [Fact]
    public void Assemble_OutsideViewWithExitPortal_HasOutsideViewTrue_AabbMatchesBounds()
    {
        var pv = new PortalVisibilityFrame();
        pv.OutsideView.Add(Square(-0.3f, 0.2f, 0.25f));

        var asm = ClipFrameAssembler.Assemble(ClipFrame.NoClip(), pv);

        Assert.True(asm.HasOutsideView);
        Assert.Equal(TerrainClipMode.Planes, asm.TerrainMode);
        Assert.Single(asm.OutsideViewSlices);

        var expected = new Vector4(
            pv.OutsideView.MinX, pv.OutsideView.MinY,
            pv.OutsideView.MaxX, pv.OutsideView.MaxY);
        Assert.Equal(expected, asm.OutsideViewNdcAabb);
    }

    [Fact]
    public void Assemble_OutsideViewMultiPolygon_PreservesSlicesAndUnionAabb()
    {
        var pv = new PortalVisibilityFrame();
        pv.OutsideView.Add(Square(-0.6f, 0f, 0.15f));
        pv.OutsideView.Add(Square(0.6f, 0f, 0.15f));

        var asm = ClipFrameAssembler.Assemble(ClipFrame.NoClip(), pv);

        Assert.True(asm.HasOutsideView);
        Assert.Equal(TerrainClipMode.Planes, asm.TerrainMode);
        Assert.Equal(2, asm.OutsideViewSlices.Length);

        var expected = new Vector4(
            pv.OutsideView.MinX, pv.OutsideView.MinY,
            pv.OutsideView.MaxX, pv.OutsideView.MaxY);
        Assert.Equal(expected, asm.OutsideViewNdcAabb);
        Assert.Equal(Vector4.Zero, asm.TerrainScissorNdcAabb);
    }

    [Fact]
    public void Assemble_EmptyOutsideView_HasOutsideViewFalse_AabbZero()
    {
        const uint cellA = 0xA9B40100;
        var pv = new PortalVisibilityFrame();
        pv.CellViews[cellA] = ViewOf(Square(0f, 0f, 0.3f));
        pv.OrderedVisibleCells.Add(cellA);

        var asm = ClipFrameAssembler.Assemble(ClipFrame.NoClip(), pv);

        Assert.False(asm.HasOutsideView);
        Assert.Equal(TerrainClipMode.Skip, asm.TerrainMode);
        Assert.Equal(Vector4.Zero, asm.OutsideViewNdcAabb);
    }

    [Fact]
    public void Reset_ReusesFrame_NoSlotLeakAcrossAssemblies()
    {
        var frame = ClipFrame.NoClip();

        var pv1 = new PortalVisibilityFrame();
        pv1.CellViews[0xA9B40100] = ViewOf(Square(-0.3f, 0f, 0.2f));
        pv1.CellViews[0xA9B40101] = ViewOf(Square(0.3f, 0f, 0.2f));
        pv1.OrderedVisibleCells.Add(0xA9B40100);
        pv1.OrderedVisibleCells.Add(0xA9B40101);
        pv1.OutsideView.Add(Square(0f, 0.4f, 0.2f));
        var asm1 = ClipFrameAssembler.Assemble(frame, pv1);
        Assert.Equal(4, asm1.Frame.SlotCount);

        var pv2 = new PortalVisibilityFrame();
        pv2.CellViews[0xA9B40200] = ViewOf(Square(0f, 0f, 0.25f));
        pv2.OrderedVisibleCells.Add(0xA9B40200);
        var asm2 = ClipFrameAssembler.Assemble(frame, pv2);

        Assert.Equal(2, asm2.Frame.SlotCount);
        Assert.Contains(0xA9B40200, asm2.CellIdToSlot.Keys);
        Assert.DoesNotContain(0xA9B40100, asm2.CellIdToSlot.Keys);
        Assert.False(asm2.OutdoorVisible);
        Assert.Equal(TerrainClipMode.Skip, asm2.TerrainMode);
    }

    [Fact]
    public void Assemble_ReusedAssembly_ClearsStateAndReusesExactLengthArrays()
    {
        const uint firstCell = 0xA9B40100;
        const uint secondCell = 0xA9B40200;
        var frame = ClipFrame.NoClip();
        var reuse = new ClipFrameAssembly();

        var first = new PortalVisibilityFrame();
        first.CellViews[firstCell] = ViewOf(
            Square(-0.4f, 0f, 0.15f),
            Square(0.4f, 0f, 0.15f));
        first.OrderedVisibleCells.Add(firstCell);
        first.OutsideView.Add(Square(0f, 0.5f, 0.2f));
        ClipFrameAssembly firstResult = ClipFrameAssembler.Assemble(frame, first, reuse);
        Assert.Same(reuse, firstResult);
        int sliceAllocations = reuse.SliceArrayAllocationCount;
        int slotAllocations = reuse.SlotArrayAllocationCount;

        var second = new PortalVisibilityFrame();
        second.CellViews[secondCell] = ViewOf(
            Square(-0.4f, 0f, 0.15f),
            Square(0.4f, 0f, 0.15f));
        second.OrderedVisibleCells.Add(secondCell);
        second.OutsideView.Add(Square(0f, 0.5f, 0.2f));

        for (int i = 0; i < 12; i++)
        {
            ClipFrameAssembly actual = ClipFrameAssembler.Assemble(frame, second, reuse);
            Assert.Same(reuse, actual);
            Assert.DoesNotContain(firstCell, actual.CellIdToViewSlices.Keys);
            Assert.Contains(secondCell, actual.CellIdToViewSlices.Keys);
            Assert.Equal(2, actual.CellIdToViewSlices[secondCell].Length);
            Assert.Equal(2, actual.CellIdToViewSlots[secondCell].Length);
            Assert.Single(actual.OutsideViewSlices);
            Assert.Equal(sliceAllocations, reuse.SliceArrayAllocationCount);
            Assert.Equal(slotAllocations, reuse.SlotArrayAllocationCount);
        }

        var empty = new PortalVisibilityFrame();
        ClipFrameAssembly cleared = ClipFrameAssembler.Assemble(frame, empty, reuse);
        Assert.Empty(cleared.CellIdToSlot);
        Assert.Empty(cleared.CellIdToViewSlots);
        Assert.Empty(cleared.CellIdToViewSlices);
        Assert.Empty(cleared.PerCellPlaneCounts);
        Assert.Empty(cleared.OutsideViewSlices);
        Assert.Equal(TerrainClipMode.Skip, cleared.TerrainMode);
    }

    [Fact]
    public void Assemble_ReusedAssembly_ChangingCardinalityStaysBoundedThenReachesSteadyState()
    {
        const uint cellId = 0xA9B40100;
        var frame = ClipFrame.NoClip();
        var reuse = new ClipFrameAssembly();

        static PortalVisibilityFrame FrameWithSlices(uint id, int count)
        {
            var portalFrame = new PortalVisibilityFrame();
            var view = new CellView();
            for (int i = 0; i < count; i++)
            {
                // The assembler consumes the retail view_poly list directly. Distinct placement is
                // irrelevant to this cache-cardinality stress; avoid CellView dedup collapsing it.
                view.Polygons.Add(Square(i * 0.001f, 0f, 0.0004f));
            }
            portalFrame.CellViews[id] = view;
            portalFrame.OrderedVisibleCells.Add(id);
            return portalFrame;
        }

        for (int count = 1; count <= 180; count++)
            ClipFrameAssembler.Assemble(frame, FrameWithSlices(cellId, count), reuse);

        // Flush the final live arrays into the cache too.
        ClipFrameAssembler.Assemble(frame, new PortalVisibilityFrame(), reuse);
        Assert.InRange(reuse.RetainedSliceItems, 0, ClipFrameAssembly.MaxRetainedSliceItems);
        Assert.InRange(reuse.RetainedSlotItems, 0, ClipFrameAssembly.MaxRetainedSlotItems);
        Assert.InRange(reuse.RetainedSliceArrays, 0, ClipFrameAssembly.MaxRetainedArraysPerPool);
        Assert.InRange(reuse.RetainedSlotArrays, 0, ClipFrameAssembly.MaxRetainedArraysPerPool);

        PortalVisibilityFrame steady = FrameWithSlices(cellId, 73);
        ClipFrameAssembler.Assemble(frame, steady, reuse);
        int sliceAllocations = reuse.SliceArrayAllocationCount;
        int slotAllocations = reuse.SlotArrayAllocationCount;
        for (int i = 0; i < 16; i++)
        {
            ClipFrameAssembler.Assemble(frame, steady, reuse);
            Assert.Equal(sliceAllocations, reuse.SliceArrayAllocationCount);
            Assert.Equal(slotAllocations, reuse.SlotArrayAllocationCount);
        }
    }
}