using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using DatReaderWriter.Enums;
using DatReaderWriter.Types;
using AcDream.Core.Physics;
using Xunit;

namespace AcDream.Core.Tests.Physics;

public class CellTransitFindCellSetTests
{
    // ──────────────────────────────────────────────────────────────────
    // Helpers — mirror CellTransitFindTransitCellsSphereTests.cs pattern
    // ──────────────────────────────────────────────────────────────────

    private static CellPhysics MakeCellWithPortalAtRightWall(
        Matrix4x4 worldTransform, uint otherCellId, ushort flags)
    {
        var portalPoly = new ResolvedPolygon
        {
            Vertices  = new[]
            {
                new Vector3(2.5f, -2.5f,  0f),
                new Vector3(2.5f,  2.5f,  0f),
                new Vector3(2.5f,  2.5f,  5f),
                new Vector3(2.5f, -2.5f,  5f),
            },
            Plane     = new Plane(new Vector3(1, 0, 0), -2.5f),  // x = 2.5
            NumPoints = 4,
            SidesType = CullMode.None,
        };

        Matrix4x4.Invert(worldTransform, out var inv);
        return new CellPhysics
        {
            WorldTransform        = worldTransform,
            InverseWorldTransform = inv,
            Resolved              = new Dictionary<ushort, ResolvedPolygon>(),
            PortalPolygons        = new Dictionary<ushort, ResolvedPolygon> { [10] = portalPoly },
            Portals               = new[]
            {
                new PortalInfo(otherCellId: (ushort)otherCellId, polygonId: 10, flags: flags),
            },
            CellBSP = new CellBSPTree
            {
                Root = new CellBSPNode { Type = BSPNodeType.Leaf },
            }
        };
    }

    // ──────────────────────────────────────────────────────────────────
    // Tests
    // ──────────────────────────────────────────────────────────────────

    [Fact]
    public void Sphere_FullyInsidePrimaryCell_ReturnsOnlyPrimary()
    {
        var cellA = MakeCellWithPortalAtRightWall(Matrix4x4.Identity, otherCellId: 0x0101, flags: 0);
        var cache = new PhysicsDataCache();
        cache.RegisterCellStructForTest(0xA9B40100u, cellA);

        // Sphere far from any portal — local x=-1, reach to x=-0.5; portal at x=2.5.
        var sphereCenter = new Vector3(-1.0f, 0f, 2.5f);

        uint containing = CellTransit.FindCellSet(
            cache, sphereCenter, sphereRadius: 0.5f,
            currentCellId: 0xA9B40100u,
            out var cellSet);

        Assert.Equal(0xA9B40100u, containing);
        Assert.Single(cellSet);
        Assert.Contains(0xA9B40100u, cellSet);
    }

    [Fact]
    public void Sphere_StraddlingPortal_ReturnsBothCells()
    {
        var cellA = MakeCellWithPortalAtRightWall(Matrix4x4.Identity, otherCellId: 0x0101, flags: 0);
        var cellBT = Matrix4x4.CreateTranslation(new Vector3(5f, 0f, 0f));
        Matrix4x4.Invert(cellBT, out var cellBInv);
        var cellB = new CellPhysics
        {
            WorldTransform        = cellBT,
            InverseWorldTransform = cellBInv,
            Resolved              = new Dictionary<ushort, ResolvedPolygon>(),
            CellBSP = new CellBSPTree
            {
                Root = new CellBSPNode { Type = BSPNodeType.Leaf },
            }
        };

        var cache = new PhysicsDataCache();
        cache.RegisterCellStructForTest(0xA9B40100u, cellA);
        cache.RegisterCellStructForTest(0xA9B40101u, cellB);

        // Sphere center at local x=2.0, radius=0.5 → reaches x=2.5 = portal plane.
        var sphereCenter = new Vector3(2.0f, 0f, 2.5f);

        uint containing = CellTransit.FindCellSet(
            cache, sphereCenter, sphereRadius: 0.5f,
            currentCellId: 0xA9B40100u,
            out var cellSet);

        Assert.Contains(0xA9B40100u, cellSet);
        Assert.Contains(0xA9B40101u, cellSet);
    }

    [Fact]
    public void FindCellSet_OutdoorSeed_IncludesNeighbourLandcells()
    {
        var cache = new PhysicsDataCache();
        // Outdoor seed near a cell boundary — expand to neighbours via
        // AddAllOutsideCells. Landcells have no CellPhysics in cache, so
        // they appear in the set but the containing-cell loop falls back
        // to currentCellId. The point of this test: the SET captures
        // them even though FindCellList's single-uint return cannot.
        //
        // World coords for landblock 0xA9B4FFFF: origin at
        // (0xA9*192, 0xB4*192) = (32448, 34560). Cell grid(0,0) covers
        // world XY in [(32448,34560), (32472,34584)). Place the sphere
        // center near the east boundary of grid(0,0) so AddAllOutsideCells
        // adds the east neighbour grid(1,0).
        uint lbPrefix = 0xA9B40000u;
        float lbX = ((lbPrefix >> 24) & 0xFFu) * 192f;
        float lbY = ((lbPrefix >> 16) & 0xFFu) * 192f;
        var sphereCenter = new Vector3(lbX + 23.8f, lbY + 12f, 0f);

        uint containing = CellTransit.FindCellSet(
            cache, sphereCenter, sphereRadius: 0.5f,
            currentCellId: 0xA9B40001u,  // outdoor cell, low byte < 0x100
            out var cellSet);

        Assert.Equal(0xA9B40001u, containing);
        Assert.True(cellSet.Count >= 2, $"Expected ≥2 cells in set (primary + east neighbour), got {cellSet.Count}");
    }
}