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

namespace AcDream.App.Tests.Rendering;

/// <summary>
/// Campaign FW4 slice 1 — <see cref="ClipFrameAssembler.ReassembleOutsideViewFromWalk"/>:
/// an interior root's outside-view slices come from the walk's OWN
/// <c>outside_view</c> (pixel screen points, origin top-left, +Y down),
/// converted to the assembler's standard-NDC <see cref="ViewPolygon"/>s.
/// </summary>
public class WalkOutsideViewReassemblyTests
{
    private const float W = 1024f, H = 720f;

    private sealed class StubRays : IWalkRayCaster
    {
        public Vector3 RayThrough(float screenX, float screenY) =>
            Vector3.Normalize(new Vector3(screenX - W / 2f, screenY - H / 2f, 1000f));
    }

    private static WalkPortalView WalkViewOfPixelQuads(params Vector2[][] pixelQuads)
    {
        var view = new WalkPortalView();
        var rays = new StubRays();
        foreach (Vector2[] quad in pixelQuads)
        {
            var pts = new WalkScreenPoint[quad.Length];
            for (int i = 0; i < quad.Length; i++)
                pts[i] = new WalkScreenPoint(quad[i].X, quad[i].Y, 0f, 1f);
            Assert.True(WalkCopyView.Append(view, pts, rays, Vector3.Zero));
        }
        return view;
    }

    private static ClipFrameAssembly AssembledWithOldOutside()
    {
        var pv = new PortalVisibilityFrame();
        pv.OutsideView.Add(new ViewPolygon(new[]
        {
            new Vector2(-0.9f, -0.9f), new Vector2(0.9f, -0.9f),
            new Vector2(0.9f, 0.9f), new Vector2(-0.9f, 0.9f),
        }));
        return ClipFrameAssembler.Assemble(ClipFrame.NoClip(), pv);
    }

    [Fact]
    public void PixelDoorway_MapsToExpectedNdcAabbAndPlanes()
    {
        ClipFrameAssembly asm = AssembledWithOldOutside();
        // Pixel quad x∈[256,512], y∈[180,360] → NDC x∈[-0.5,0], y∈[0,0.5]
        // (yNdc = 1 − 2·py/H flips the axis: py=180 → +0.5, py=360 → 0).
        WalkPortalView walkView = WalkViewOfPixelQuads(new[]
        {
            new Vector2(256f, 180f), new Vector2(512f, 180f),
            new Vector2(512f, 360f), new Vector2(256f, 360f),
        });

        ClipFrameAssembler.ReassembleOutsideViewFromWalk(asm, walkView, W, H);

        ClipViewSlice slice = Assert.Single(asm.OutsideViewSlices);
        Assert.Equal(TerrainClipMode.Planes, asm.TerrainMode);
        Assert.True(asm.OutdoorVisible);
        Assert.Equal(4, asm.OutsidePlaneCount);
        Assert.Equal(slice.Slot, asm.OutdoorSlot);
        Assert.NotEqual(0, slice.Slot);
        Assert.Equal(-0.5f, slice.NdcAabb.X, 3);
        Assert.Equal(0f, slice.NdcAabb.Y, 3);
        Assert.Equal(0f, slice.NdcAabb.Z, 3);
        Assert.Equal(0.5f, slice.NdcAabb.W, 3);
        Assert.Equal(slice.NdcAabb, asm.OutsideViewNdcAabb);

        // Every corner of the doorway satisfies every inward plane
        // (n·p + d >= 0), and a point far outside fails at least one.
        Vector2[] ndcCorners =
        {
            new(-0.5f, 0f), new(0f, 0f), new(0f, 0.5f), new(-0.5f, 0.5f),
        };
        foreach (Vector2 corner in ndcCorners)
        {
            foreach (Vector4 plane in slice.Planes)
                Assert.True(plane.X * corner.X + plane.Y * corner.Y + plane.W >= -1e-4f);
        }
        bool outsideFails = false;
        foreach (Vector4 plane in slice.Planes)
            outsideFails |= plane.X * 0.9f + plane.Y * -0.9f + plane.W < 0f;
        Assert.True(outsideFails);
    }

    [Fact]
    public void FullViewportWalkQuad_CoversFullNdc()
    {
        ClipFrameAssembly asm = AssembledWithOldOutside();
        var walkView = new WalkPortalView();
        Assert.True(WalkCopyView.AppendFullViewportQuad(
            walkView, new StubRays(), Vector3.Zero, W, H));

        ClipFrameAssembler.ReassembleOutsideViewFromWalk(asm, walkView, W, H);

        ClipViewSlice slice = Assert.Single(asm.OutsideViewSlices);
        Assert.Equal(new Vector4(-1f, -1f, 1f, 1f), slice.NdcAabb);
        Assert.Equal(TerrainClipMode.Planes, asm.TerrainMode);
    }

    [Fact]
    public void EmptyWalkView_YieldsSkipMode()
    {
        ClipFrameAssembly asm = AssembledWithOldOutside();
        Assert.True(asm.OutdoorVisible); // the old view was visible pre-cutover

        ClipFrameAssembler.ReassembleOutsideViewFromWalk(asm, new WalkPortalView(), W, H);

        Assert.Empty(asm.OutsideViewSlices);
        Assert.False(asm.OutdoorVisible);
        Assert.False(asm.HasOutsideView);
        Assert.Equal(TerrainClipMode.Skip, asm.TerrainMode);
        Assert.Equal(0, asm.OutsidePlaneCount);
        Assert.Equal(0, asm.OutdoorSlot);
    }

    [Fact]
    public void TwoWalkViews_ProduceTwoSlicesWithDistinctSlots()
    {
        ClipFrameAssembly asm = AssembledWithOldOutside();
        WalkPortalView walkView = WalkViewOfPixelQuads(
            new[]
            {
                new Vector2(100f, 100f), new Vector2(300f, 100f),
                new Vector2(300f, 300f), new Vector2(100f, 300f),
            },
            new[]
            {
                new Vector2(600f, 400f), new Vector2(900f, 400f),
                new Vector2(900f, 650f), new Vector2(600f, 650f),
            });

        ClipFrameAssembler.ReassembleOutsideViewFromWalk(asm, walkView, W, H);

        Assert.Equal(2, asm.OutsideViewSlices.Length);
        Assert.NotEqual(asm.OutsideViewSlices[0].Slot, asm.OutsideViewSlices[1].Slot);
        // The union AABB spans both doorways.
        Assert.True(asm.OutsideViewNdcAabb.X < asm.OutsideViewSlices[0].NdcAabb.Z);
        Assert.True(asm.OutsideViewNdcAabb.Z >= asm.OutsideViewSlices[1].NdcAabb.X);
    }
}