acdream/tests/AcDream.Core.Tests/Physics/CellGraphMembershipTests.cs

using System.Collections.Generic;
using System.Numerics;
using AcDream.Core.Physics;
using DatReaderWriter.Types;
using Xunit;
using DatEnvCell = DatReaderWriter.DBObjs.EnvCell;

namespace AcDream.Core.Tests.Physics;

// 2026-06-03 blue-hole fix: CellGraph.CurrCell IS "the player's cell" (CellGraph.cs:19) — it roots
// the indoor render (GameWindow.OnRender). It is written ONLY by the player-only
// PhysicsEngine.UpdatePlayerCurrCell (called from PlayerMovementController.UpdateCellId, the single
// player chokepoint for CellId), NOT by the per-entity ResolveCellId / ResolveWithTransition. Before
// the fix, those per-entity paths wrote CurrCell, so a Holtburg NPC jump-looping near the cottage
// doorway clobbered the player's render root every tick → the render rooted at the NPC's tiny
// connector cell → the cottage doorway "blue-hole" flap.
public class CellGraphMembershipTests
{
    private static PhysicsEngine MakeEngineWithCell(uint cellId)
    {
        var engine = new PhysicsEngine();
        var cache = new PhysicsDataCache();
        engine.DataCache = cache;

        var cs = new CellStruct
        {
            VertexArray = new VertexArray { Vertices = new Dictionary<ushort, SWVertex>() },
            Polygons = new Dictionary<ushort, Polygon>(),
            PhysicsBSP = null,
        };
        var dat = new DatEnvCell
        {
            Flags = (DatReaderWriter.Enums.EnvCellFlags)0,
            CellPortals = new List<DatReaderWriter.Types.CellPortal>(),
            VisibleCells = new List<ushort>(),
        };
        cache.CacheCellStruct(cellId, dat, cs, Matrix4x4.Identity);  // registers in the graph (W1)
        return engine;
    }

    [Fact]
    public void UpdatePlayerCurrCell_Resolved_WritesCurrCellTrackingTheId()
    {
        var engine = MakeEngineWithCell(0xA9B40174u);

        engine.UpdatePlayerCurrCell(0xA9B40174u);

        Assert.NotNull(engine.DataCache!.CellGraph.CurrCell);
        Assert.Equal(0xA9B40174u, engine.DataCache.CellGraph.CurrCell!.Id);
    }

    [Fact]
    public void UpdatePlayerCurrCell_UnresolvableId_LeavesCurrCellUnchanged()
    {
        var engine = MakeEngineWithCell(0xA9B40174u);
        engine.UpdatePlayerCurrCell(0xA9B40174u);   // CurrCell = 0174

        engine.UpdatePlayerCurrCell(0xDEADBEEFu);   // not in the graph → stale beats null

        Assert.NotNull(engine.DataCache!.CellGraph.CurrCell);
        Assert.Equal(0xA9B40174u, engine.DataCache.CellGraph.CurrCell!.Id);
    }

    // Guards the blue-hole fix: the per-entity ResolveCellId must NOT touch the render root.
    // (Only the player's UpdatePlayerCurrCell does.) Before the fix this wrote CurrCell, so a
    // nearby NPC's ResolveCellId/ResolveWithTransition clobbered the player's render root.
    [Fact]
    public void ResolveCellId_DoesNotWriteTheRenderRoot()
    {
        var engine = MakeEngineWithCell(0xA9B40174u);

        uint result = engine.ResolveCellId(new Vector3(0, 0, 0), 0.5f, 0xA9B40174u);

        Assert.Equal(0xA9B40174u, result);                    // still resolves the cell correctly
        Assert.Null(engine.DataCache!.CellGraph.CurrCell);    // but does NOT write the render root
    }
}