using System.Collections.Generic;
using System.Numerics;
using AcDream.Core.Physics;
using Xunit;

namespace AcDream.Core.Tests.Physics;

public class CellTransitCheckBuildingTransitTests
{
    [Fact]
    public void BuildingPortalWithUnloadedCellBSP_NoCandidateAdded()
    {
        // Verifies the null-CellBSP guard: when the destination interior cell
        // is cached but its CellBSP isn't yet loaded (or is structurally absent),
        // CheckBuildingTransit must NOT add the cell to candidates — even though
        // PointInsideCellBsp(null, _) returns true.
        //
        // Happy-path (CellBSP present, sphere inside) requires a synthetic
        // CellBSPTree which is non-trivial to construct from DatReaderWriter
        // types. Deferred to visual verification.

        // Building at world origin. One portal to interior cell 0xA9B40100.
        var building = new BuildingPhysics
        {
            WorldTransform = Matrix4x4.Identity,
            InverseWorldTransform = Matrix4x4.Identity,
            Portals = new[]
            {
                new BldPortalInfo(
                    otherCellId: 0xA9B40100u,
                    otherPortalId: 0,
                    flags: 0),
            },
        };

        // Interior cell with null CellBSP — PointInsideCellBsp(null, _) returns true,
        // but CheckBuildingTransit guards on CellBSP?.Root being non-null, so this
        // cell is skipped.
        var interiorCell = new CellPhysics
        {
            WorldTransform = Matrix4x4.Identity,
            InverseWorldTransform = Matrix4x4.Identity,
            Resolved = new Dictionary<ushort, ResolvedPolygon>(),
        };

        var cache = new PhysicsDataCache();
        cache.RegisterCellStructForTest(0xA9B40100u, interiorCell);

        var candidates = new HashSet<uint>();
        CellTransit.CheckBuildingTransit(
            cache, building,
            worldSphereCenter: new Vector3(0, 0, 0),
            sphereRadius: 0.5f,
            candidates);

        // CellBSP is null → containment guard (otherCell?.CellBSP?.Root is null)
        // skips this cell. No candidate added.
        Assert.Empty(candidates);
    }

    // A second test that uses a synthetic CellBSP whose Root.Type == BSPNodeType.Leaf
    // (which PointInsideCellBsp short-circuits as "inside") would verify the
    // happy path. Constructing a CellBSPTree by hand from DatReaderWriter
    // types is awkward; deferred to integration testing at visual-verify time.
}