using AcDream.App.Streaming;
using AcDream.App.World;
using AcDream.App.Rendering.Vfx;
using AcDream.Core.Net;
using AcDream.Core.Net.Messages;
using AcDream.Core.Physics;
using AcDream.Core.Vfx;
using AcDream.Core.World;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Types;
using DatPhysicsScript = DatReaderWriter.DBObjs.PhysicsScript;

namespace AcDream.App.Tests.World;

public sealed class LiveEntityRuntimeTests
{
    private sealed class RecordingResources : ILiveEntityResourceLifecycle
    {
        public int RegisterCount { get; private set; }
        public int UnregisterCount { get; private set; }
        public void Register(WorldEntity entity) => RegisterCount++;
        public void Unregister(WorldEntity entity) => UnregisterCount++;
    }

    private sealed class AnimationRuntime(WorldEntity entity) : ILiveEntityAnimationRuntime
    {
        public WorldEntity Entity { get; } = entity;
    }

    private sealed class EffectProfile : ILiveEntityEffectProfile { }

    private sealed class FailingRegisterResources : ILiveEntityResourceLifecycle
    {
        public int RegisterCount { get; private set; }
        public int UnregisterCount { get; private set; }

        public void Register(WorldEntity entity)
        {
            RegisterCount++;
            throw new InvalidOperationException("fixture registration failure");
        }

        public void Unregister(WorldEntity entity) => UnregisterCount++;
    }

    private sealed class FailingUnregisterResources(uint failingGuid) : ILiveEntityResourceLifecycle
    {
        public int UnregisterCount { get; private set; }

        public void Register(WorldEntity entity) { }

        public void Unregister(WorldEntity entity)
        {
            UnregisterCount++;
            if (entity.ServerGuid == failingGuid)
                throw new InvalidOperationException("fixture unregister failure");
        }
    }

    [Fact]
    public void RegisterRebucketWithdrawAndRestore_UsesOneLogicalCreate()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        spatial.AddLandblock(EmptyLandblock(0x0102FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(0x70000001u, 1, 1, 0x01010001u);

        LiveEntityRegistrationResult registered = runtime.RegisterLiveEntity(spawn);
        WorldEntity? entity = runtime.MaterializeLiveEntity(
            spawn.Guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, spawn.Guid));
        runtime.SetAnimationRuntime(spawn.Guid, new AnimationRuntime(entity!));

        Assert.True(registered.LogicalRegistrationCreated);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Single(spatial.Entities);
        Assert.True(runtime.RebucketLiveEntity(spawn.Guid, 0x01020001u));
        Assert.Equal(1, resources.RegisterCount);
        Assert.Single(spatial.Entities);
        Assert.True(runtime.WithdrawLiveEntityProjection(spawn.Guid));
        Assert.Empty(spatial.Entities);
        Assert.Empty(runtime.WorldEntities);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);
        Assert.True(runtime.TryGetAnimationRuntime(entity!.Id, out _));
        Assert.True(runtime.RebucketLiveEntity(spawn.Guid, 0x01010001u));
        Assert.Single(spatial.Entities);
        Assert.Equal(1, resources.RegisterCount);
        Assert.True(runtime.TryGetAnimationRuntime(entity!.Id, out _));
    }

    [Fact]
    public void EffectProfile_SurvivesRebucketAndClearsWithLogicalTeardown()
    {
        const uint guid = 0x70000030u;
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        spatial.AddLandblock(EmptyLandblock(0x0102FFFFu));
        var runtime = new LiveEntityRuntime(spatial, new RecordingResources());
        WorldSession.EntitySpawn spawn = Spawn(guid, 6, 1, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);
        var profile = new EffectProfile();
        runtime.SetEffectProfile(guid, profile);
        runtime.MaterializeLiveEntity(
            guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, guid));

        Assert.True(runtime.RebucketLiveEntity(guid, 0x01020001u));
        Assert.True(runtime.TryGetEffectProfile(guid, out var retained));
        Assert.Same(profile, retained);

        Assert.True(runtime.UnregisterLiveEntity(
            new DeleteObject.Parsed(guid, spawn.InstanceSequence),
            isLocalPlayer: false));
        Assert.False(runtime.TryGetEffectProfile(guid, out _));
    }

    [Fact]
    public void InitialChildCreate_PreservesParentEventQueuedForMissingChild()
    {
        const uint parentGuid = 0x70000020u;
        const uint childGuid = 0x70000021u;
        var runtime = new LiveEntityRuntime(new GpuWorldState(), new RecordingResources());
        runtime.RegisterLiveEntity(Spawn(parentGuid, 9, 1, 0x01010001u));
        runtime.ParentAttachments.Enqueue(new ParentEvent.Parsed(
            parentGuid, childGuid, 1, 2, 9, 5));
        ResolveParent(runtime, childGuid);

        runtime.RegisterLiveEntity(Spawn(childGuid, 3, 4, 0x01010001u));
        ResolveParent(runtime, childGuid);

        Assert.True(runtime.ParentAttachments.TryGetProjection(
            childGuid, out ParentAttachmentRelation relation));
        Assert.Equal(parentGuid, relation.ParentGuid);
        Assert.True(runtime.TryGetSnapshot(childGuid, out WorldSession.EntitySpawn child));
        Assert.Null(child.Position);
    }

    [Fact]
    public void InitialParentCreate_PreservesCreateObjectRelationWaitingForParent()
    {
        const uint parentGuid = 0x70000022u;
        const uint childGuid = 0x70000023u;
        var runtime = new LiveEntityRuntime(new GpuWorldState(), new RecordingResources());
        runtime.RegisterLiveEntity(Spawn(childGuid, 3, 4, 0x01010001u));
        runtime.ParentAttachments.AcceptCreateObjectRelation(new ParentAttachmentRelation(
            parentGuid, childGuid, 1, 2, 9, 4));

        runtime.RegisterLiveEntity(Spawn(parentGuid, 9, 1, 0x01010001u));

        Assert.True(runtime.ParentAttachments.TryGetProjection(
            childGuid, out ParentAttachmentRelation relation));
        Assert.Equal(parentGuid, relation.ParentGuid);
    }

    [Fact]
    public void SameGenerationCreate_DoesNotReconstructProjection()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn first = Spawn(0x70000002u, 4, 10, 0x01010001u);
        runtime.RegisterLiveEntity(first);
        WorldEntity original = runtime.MaterializeLiveEntity(
            first.Guid,
            first.Position!.Value.LandblockId,
            id => Entity(id, first.Guid))!;

        LiveEntityRegistrationResult refresh = runtime.RegisterLiveEntity(
            Spawn(first.Guid, 4, 11, 0x01010001u));
        WorldEntity retained = runtime.MaterializeLiveEntity(
            first.Guid,
            first.Position.Value.LandblockId,
            _ => throw new InvalidOperationException("same generation reconstructed"))!;

        Assert.False(refresh.LogicalRegistrationCreated);
        Assert.Same(original, retained);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);
    }

    [Fact]
    public void NewGeneration_TearsDownExactlyOnceAndReusesNoLocalIdentity()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        int runtimeTearDowns = 0;
        var runtime = new LiveEntityRuntime(
            spatial,
            resources,
            _ => runtimeTearDowns++);
        const uint guid = 0x70000003u;

        runtime.RegisterLiveEntity(Spawn(guid, 9, 1, 0x01010001u));
        WorldEntity old = runtime.MaterializeLiveEntity(
            guid, 0x01010001u, id => Entity(id, guid))!;
        LiveEntityRegistrationResult replacement = runtime.RegisterLiveEntity(
            Spawn(guid, 10, 1, 0x01010001u));
        WorldEntity current = runtime.MaterializeLiveEntity(
            guid, 0x01010001u, id => Entity(id, guid))!;

        Assert.True(replacement.ReplacedExistingGeneration);
        Assert.NotEqual(old.Id, current.Id);
        Assert.Equal(2, resources.RegisterCount);
        Assert.Equal(1, resources.UnregisterCount);
        Assert.Equal(1, runtimeTearDowns);
        Assert.Single(spatial.Entities);
        Assert.Same(current, spatial.Entities[0]);
        Assert.False(runtime.TryGetServerGuid(old.Id, out _));
        Assert.True(runtime.TryGetServerGuid(current.Id, out uint mapped));
        Assert.Equal(guid, mapped);
    }

    [Fact]
    public void AppearanceUpdate_MutatesSnapshotWithoutChangingIdentity()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(0x70000004u, 2, 3, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);
        WorldEntity entity = runtime.MaterializeLiveEntity(
            spawn.Guid, 0x01010001u, id => Entity(id, spawn.Guid))!;

        var update = new ObjDescEvent.Parsed(
            spawn.Guid,
            new CreateObject.ModelData(
                0x04000001u,
                Array.Empty<CreateObject.SubPaletteSwap>(),
                Array.Empty<CreateObject.TextureChange>(),
                Array.Empty<CreateObject.AnimPartChange>()),
            InstanceSequence: 2,
            ObjDescSequence: 2);
        Assert.True(runtime.TryApplyObjDesc(update, out _));

        Assert.True(runtime.TryGetRecord(spawn.Guid, out LiveEntityRecord record));
        Assert.Same(entity, record.WorldEntity);
        Assert.Equal((uint)0x04000001u, record.Snapshot.BasePaletteId);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);
    }

    [Fact]
    public void DeleteAndGuidReuse_HaveSeparateLogicalLifetimes()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        const uint guid = 0x70000005u;
        runtime.RegisterLiveEntity(Spawn(guid, 3, 1, 0x01010001u));
        WorldEntity first = runtime.MaterializeLiveEntity(
            guid, 0x01010001u, id => Entity(id, guid))!;

        Assert.True(runtime.UnregisterLiveEntity(
            new DeleteObject.Parsed(guid, 3),
            isLocalPlayer: false));
        Assert.Empty(spatial.Entities);
        Assert.False(runtime.TryGetRecord(guid, out _));

        runtime.RegisterLiveEntity(Spawn(guid, 3, 1, 0x01010001u));
        WorldEntity second = runtime.MaterializeLiveEntity(
            guid, 0x01010001u, id => Entity(id, guid))!;

        Assert.NotEqual(first.Id, second.Id);
        Assert.Equal(2, resources.RegisterCount);
        Assert.Equal(1, resources.UnregisterCount);
    }

    [Fact]
    public void AttachedProjection_RendersWithoutEnteringTopLevelWorldIndex()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(0x70000006u, 3, 1, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);

        WorldEntity attached = runtime.MaterializeLiveEntity(
            spawn.Guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, spawn.Guid),
            LiveEntityProjectionKind.Attached)!;

        Assert.Single(spatial.Entities);
        Assert.Empty(runtime.WorldEntities);
        Assert.False(runtime.TryMarkWorldSpawnPublished(spawn.Guid));
        Assert.True(runtime.TryGetWorldEntity(spawn.Guid, out WorldEntity resolved));
        Assert.Same(attached, resolved);
        Assert.Equal(1, resources.RegisterCount);

        WorldEntity same = runtime.MaterializeLiveEntity(
            spawn.Guid,
            spawn.Position.Value.LandblockId,
            _ => throw new InvalidOperationException("attachment reconstructed"),
            LiveEntityProjectionKind.World)!;

        Assert.Same(attached, same);
        Assert.Same(attached, Assert.Single(runtime.WorldEntities).Value);
        Assert.True(runtime.TryMarkWorldSpawnPublished(spawn.Guid));
        Assert.False(runtime.TryMarkWorldSpawnPublished(spawn.Guid));
        Assert.Equal(1, resources.RegisterCount);
    }

    [Fact]
    public void PendingToLoadedTransition_DoesNotReplayLogicalRegistration()
    {
        var spatial = new GpuWorldState();
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(0x70000007u, 1, 1, 0x01020001u);
        runtime.RegisterLiveEntity(spawn);
        WorldEntity entity = runtime.MaterializeLiveEntity(
            spawn.Guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, spawn.Guid))!;

        Assert.Empty(spatial.Entities);
        Assert.Equal(1, spatial.PendingLiveEntityCount);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Empty(runtime.WorldEntities);
        Assert.Same(entity, Assert.Single(runtime.MaterializedWorldEntities).Value);

        spatial.AddLandblock(EmptyLandblock(0x0102FFFFu));
        Assert.Same(entity, Assert.Single(spatial.Entities));
        Assert.Same(entity, Assert.Single(runtime.WorldEntities).Value);
        Assert.True(runtime.RebucketLiveEntity(spawn.Guid, 0x01020001u));
        Assert.Same(entity, Assert.Single(spatial.Entities));
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);
    }

    [Fact]
    public void PendingProjection_RemainsCanonicalAcrossAuthoritativeUpdatesWithoutReregister()
    {
        const uint guid = 0x70000025u;
        var spatial = new GpuWorldState();
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(guid, 2, 1, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);
        WorldEntity entity = runtime.MaterializeLiveEntity(
            guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, guid))!;

        Assert.Empty(runtime.WorldEntities);
        Assert.Same(entity, Assert.Single(runtime.MaterializedWorldEntities).Value);
        Assert.True(runtime.TryApplyVector(
            new VectorUpdate.Parsed(
                guid,
                new System.Numerics.Vector3(2f, 3f, 4f),
                System.Numerics.Vector3.Zero,
                spawn.InstanceSequence,
                2),
            out _));
        var positionUpdate = new WorldSession.EntityPositionUpdate(
            guid,
            new CreateObject.ServerPosition(
                0x01020001u, 20f, 30f, 6f, 1f, 0f, 0f, 0f),
            null,
            null,
            true,
            spawn.InstanceSequence,
            2,
            0,
            0);
        Assert.True(runtime.TryApplyPosition(
            positionUpdate,
            isLocalPlayer: false,
            forcePositionRotation: null,
            currentLocalVelocity: null,
            out PositionTimestampDisposition disposition,
            out WorldSession.EntitySpawn accepted,
            out _));
        Assert.Equal(PositionTimestampDisposition.Apply, disposition);
        Assert.True(runtime.RebucketLiveEntity(guid, accepted.Position!.Value.LandblockId));

        Assert.Empty(runtime.WorldEntities);
        Assert.Same(entity, Assert.Single(runtime.MaterializedWorldEntities).Value);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);
        Assert.Equal(1, spatial.PendingLiveEntityCount);
    }

    [Fact]
    public void PickupLeaveWorld_PreservesOwnersButPausesRootUntilPositionReentry()
    {
        const uint guid = 0x70000026u;
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(guid, 4, 10, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);
        WorldEntity entity = runtime.MaterializeLiveEntity(
            guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, guid))!;
        var animation = new AnimationRuntime(entity);
        runtime.SetAnimationRuntime(guid, animation);
        uint localId = entity.Id;
        Assert.True(runtime.TryMarkWorldSpawnPublished(guid));

        Assert.True(runtime.TryApplyPickup(
            new PickupEvent.Parsed(guid, spawn.InstanceSequence, 11),
            out _));
        Assert.True(runtime.WithdrawLiveEntityProjection(guid));

        Assert.True(runtime.TryGetRecord(guid, out LiveEntityRecord record));
        Assert.Equal(0u, record.FullCellId);
        Assert.Equal(0u, record.CanonicalLandblockId);
        Assert.False(runtime.ShouldAdvanceRootRuntime(guid));
        Assert.True(runtime.TryGetAnimationRuntime(localId, out var retainedAnimation));
        Assert.Same(animation, retainedAnimation);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);

        var positionUpdate = new WorldSession.EntityPositionUpdate(
            guid,
            new CreateObject.ServerPosition(
                0x01010002u, 30f, 40f, 7f, 1f, 0f, 0f, 0f),
            null,
            null,
            true,
            spawn.InstanceSequence,
            12,
            0,
            0);
        Assert.True(runtime.TryApplyPosition(
            positionUpdate,
            isLocalPlayer: false,
            forcePositionRotation: null,
            currentLocalVelocity: null,
            out PositionTimestampDisposition disposition,
            out WorldSession.EntitySpawn accepted,
            out _));
        Assert.Equal(PositionTimestampDisposition.Apply, disposition);
        WorldEntity same = runtime.MaterializeLiveEntity(
            guid,
            accepted.Position!.Value.LandblockId,
            _ => throw new InvalidOperationException("re-entry reconstructed the projection"))!;

        Assert.Same(entity, same);
        Assert.Equal(localId, same.Id);
        Assert.False(runtime.TryMarkWorldSpawnPublished(guid));
        Assert.True(runtime.ShouldAdvanceRootRuntime(guid));
        Assert.Equal(0x01010002u, record.FullCellId);
        Assert.True(runtime.TryGetAnimationRuntime(localId, out retainedAnimation));
        Assert.Same(animation, retainedAnimation);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);
    }

    [Fact]
    public void RootRuntimePausesWhilePendingOrFrozenAndResumesInVisibleCell()
    {
        const uint guid = 0x70000027u;
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var runtime = new LiveEntityRuntime(spatial, new RecordingResources());
        WorldSession.EntitySpawn spawn = Spawn(guid, 1, 1, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);
        runtime.MaterializeLiveEntity(
            guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, guid));

        Assert.True(runtime.ShouldAdvanceRootRuntime(guid));
        Assert.True(runtime.RebucketLiveEntity(guid, 0x02020001u));
        Assert.False(runtime.ShouldAdvanceRootRuntime(guid));

        spatial.AddLandblock(EmptyLandblock(0x0202FFFFu));
        Assert.True(runtime.ShouldAdvanceRootRuntime(guid));

        Assert.True(runtime.TryApplyState(
            new SetState.Parsed(
                guid,
                (uint)(PhysicsStateFlags.ReportCollisions | PhysicsStateFlags.Frozen),
                1,
                2),
            out _));
        Assert.False(runtime.ShouldAdvanceRootRuntime(guid));

        Assert.True(runtime.TryApplyState(
            new SetState.Parsed(
                guid,
                (uint)PhysicsStateFlags.ReportCollisions,
                1,
                3),
            out _));
        Assert.True(runtime.ShouldAdvanceRootRuntime(guid));
    }

    [Fact]
    public void LandblockUnload_HidesTopLevelViewAndReloadRestoresSameIdentity()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(0x70000024u, 1, 1, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);
        WorldEntity entity = runtime.MaterializeLiveEntity(
            spawn.Guid,
            0x01010001u,
            id => Entity(id, spawn.Guid))!;

        spatial.RemoveLandblock(0x0101FFFFu);

        Assert.Empty(runtime.WorldEntities);
        Assert.True(runtime.TryGetRecord(spawn.Guid, out LiveEntityRecord record));
        Assert.True(record.IsSpatiallyProjected);
        Assert.False(record.IsSpatiallyVisible);
        Assert.Equal(1, spatial.PendingLiveEntityCount);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);

        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        Assert.Same(entity, Assert.Single(runtime.WorldEntities).Value);
        Assert.True(record.IsSpatiallyVisible);
        Assert.Equal(1, resources.RegisterCount);
    }

    [Fact]
    public void LoadedToPendingToLoaded_RemovesOldDrawSlotWithoutLogicalRecreate()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(0x70000009u, 1, 1, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);
        WorldEntity entity = runtime.MaterializeLiveEntity(
            spawn.Guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, spawn.Guid))!;

        Assert.Same(entity, Assert.Single(spatial.Entities));
        Assert.True(runtime.RebucketLiveEntity(spawn.Guid, 0x01020001u));
        Assert.Empty(spatial.Entities);
        Assert.Equal(1, spatial.PendingLiveEntityCount);
        Assert.Equal(1, resources.RegisterCount);

        spatial.AddLandblock(EmptyLandblock(0x0102FFFFu));
        Assert.Same(entity, Assert.Single(spatial.Entities));
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);
    }

    [Fact]
    public void SessionClear_IsSymmetricAndIdempotent()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        int runtimeTearDowns = 0;
        var runtime = new LiveEntityRuntime(spatial, resources, _ => runtimeTearDowns++);
        WorldSession.EntitySpawn spawn = Spawn(0x70000008u, 1, 1, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);
        runtime.MaterializeLiveEntity(
            spawn.Guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, spawn.Guid));

        runtime.Clear();
        runtime.Clear();

        Assert.Equal(0, runtime.Count);
        Assert.Empty(runtime.WorldEntities);
        Assert.Empty(spatial.Entities);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(1, resources.UnregisterCount);
        Assert.Equal(1, runtimeTearDowns);
    }

    [Fact]
    public void ResourceRegistrationFailure_RollsBackMaterializedIdentityAndSpatialState()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new FailingRegisterResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(0x7000000Au, 1, 1, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);

        Assert.Throws<InvalidOperationException>(() => runtime.MaterializeLiveEntity(
            spawn.Guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, spawn.Guid)));

        Assert.True(runtime.TryGetRecord(spawn.Guid, out LiveEntityRecord record));
        Assert.Null(record.WorldEntity);
        Assert.Equal(0, runtime.MaterializedCount);
        Assert.Empty(runtime.WorldEntities);
        Assert.Empty(spatial.Entities);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(1, resources.UnregisterCount);
    }

    [Fact]
    public void SessionClear_AttemptsEveryTeardownAndClearsIdentityWhenOneResourceFails()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new FailingUnregisterResources(0x7000000Bu);
        var runtime = new LiveEntityRuntime(spatial, resources);
        foreach (uint guid in new[] { 0x7000000Bu, 0x7000000Cu })
        {
            WorldSession.EntitySpawn spawn = Spawn(guid, 1, 1, 0x01010001u);
            runtime.RegisterLiveEntity(spawn);
            runtime.MaterializeLiveEntity(
                guid,
                spawn.Position!.Value.LandblockId,
                id => Entity(id, guid));
        }

        Assert.Throws<AggregateException>(() => runtime.Clear());

        Assert.Equal(2, resources.UnregisterCount);
        Assert.Equal(0, runtime.Count);
        Assert.Equal(0, runtime.MaterializedCount);
        Assert.Empty(runtime.WorldEntities);
        Assert.Empty(spatial.Entities);
    }

    [Fact]
    public void GenerationReplacement_InstallsNewRecordBeforeReportingOldCleanupFailure()
    {
        const uint guid = 0x7000000Eu;
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new FailingUnregisterResources(guid);
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn first = Spawn(guid, 1, 1, 0x01010001u);
        runtime.RegisterLiveEntity(first);
        runtime.MaterializeLiveEntity(
            guid,
            first.Position!.Value.LandblockId,
            id => Entity(id, guid));

        LiveEntityRegistrationResult replacement = runtime.RegisterLiveEntity(
            Spawn(guid, 2, 1, 0x01010001u));

        Assert.NotNull(replacement.PriorGenerationCleanupFailure);
        Assert.True(runtime.TryGetRecord(guid, out LiveEntityRecord record));
        Assert.Equal((ushort)2, record.Generation);
        Assert.Null(record.WorldEntity);
        WorldEntity installed = runtime.MaterializeLiveEntity(
            guid,
            0x01010001u,
            id => Entity(id, guid))!;
        Assert.Equal(guid, installed.ServerGuid);
        Assert.Single(spatial.Entities);
    }

    [Fact]
    public void CanonicalOnlyRebucket_DoesNotOverwriteAuthoritativeFullCell()
    {
        const uint guid = 0x7000000Fu;
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        spatial.AddLandblock(EmptyLandblock(0x0102FFFFu));
        var runtime = new LiveEntityRuntime(spatial, new RecordingResources());
        runtime.RegisterLiveEntity(Spawn(guid, 1, 1, 0x01010022u));
        runtime.MaterializeLiveEntity(guid, 0x01010022u, id => Entity(id, guid));

        runtime.RebucketLiveEntity(guid, 0x0102FFFFu);

        Assert.True(runtime.TryGetRecord(guid, out LiveEntityRecord record));
        Assert.Equal(0x01010022u, record.FullCellId);
        Assert.Equal(0x0102FFFFu, record.CanonicalLandblockId);

        runtime.RebucketLiveEntity(guid, 0x01020033u);
        Assert.Equal(0x01020033u, record.FullCellId);
    }

    [Fact]
    public void AttachedProjection_CrossesLandblocksWithoutChangingIdentityOrResources()
    {
        const uint guid = 0x70000010u;
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        spatial.AddLandblock(EmptyLandblock(0x0102FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        runtime.RegisterLiveEntity(Spawn(guid, 1, 1, 0x01010001u));
        WorldEntity attached = runtime.MaterializeLiveEntity(
            guid,
            0x01010001u,
            id => Entity(id, guid),
            LiveEntityProjectionKind.Attached)!;

        runtime.RebucketLiveEntity(guid, 0x01020001u);

        Assert.Same(attached, Assert.Single(spatial.Entities));
        Assert.Empty(runtime.WorldEntities);
        Assert.Equal(1, resources.RegisterCount);
        Assert.Equal(0, resources.UnregisterCount);
        var destination = Assert.Single(
            spatial.LandblockEntries,
            entry => entry.LandblockId == 0x0102FFFFu);
        Assert.Same(attached, Assert.Single(destination.Entities));
    }

    [Fact]
    public void LocalIdAllocator_WrapsInsideLiveNamespaceWithoutReturningZero()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var runtime = new LiveEntityRuntime(
            spatial,
            new RecordingResources(),
            firstLocalEntityId: LiveEntityRuntime.LastLiveEntityId);
        WorldSession.EntitySpawn first = Spawn(0x70000011u, 1, 1, 0x01010001u);
        WorldSession.EntitySpawn second = Spawn(0x70000012u, 1, 1, 0x01010001u);
        runtime.RegisterLiveEntity(first);
        runtime.RegisterLiveEntity(second);

        WorldEntity firstEntity = runtime.MaterializeLiveEntity(
            first.Guid, 0x01010001u, id => Entity(id, first.Guid))!;
        WorldEntity secondEntity = runtime.MaterializeLiveEntity(
            second.Guid, 0x01010001u, id => Entity(id, second.Guid))!;

        Assert.Equal(LiveEntityRuntime.LastLiveEntityId, firstEntity.Id);
        Assert.Equal(LiveEntityRuntime.FirstLiveEntityId, secondEntity.Id);
        Assert.NotEqual(0u, secondEntity.Id);
        Assert.True(runtime.TryGetLocalEntityId(second.Guid, out uint resolved));
        Assert.Equal(secondEntity.Id, resolved);
        Assert.Throws<ArgumentOutOfRangeException>(() => new LiveEntityRuntime(
            new GpuWorldState(),
            new RecordingResources(),
            firstLocalEntityId: uint.MaxValue));
    }

    [Fact]
    public void Delete_CleansLogicalRecordEvenWhenPreTeardownCallbackFails()
    {
        var spatial = new GpuWorldState();
        spatial.AddLandblock(EmptyLandblock(0x0101FFFFu));
        var resources = new RecordingResources();
        var runtime = new LiveEntityRuntime(spatial, resources);
        WorldSession.EntitySpawn spawn = Spawn(0x7000000Du, 4, 1, 0x01010001u);
        runtime.RegisterLiveEntity(spawn);
        runtime.MaterializeLiveEntity(
            spawn.Guid,
            spawn.Position!.Value.LandblockId,
            id => Entity(id, spawn.Guid));

        Assert.Throws<AggregateException>(() => runtime.UnregisterLiveEntity(
            new DeleteObject.Parsed(spawn.Guid, spawn.InstanceSequence),
            isLocalPlayer: false,
            beforeTeardown: () => throw new InvalidOperationException("fixture callback failure")));

        Assert.Equal(0, runtime.Count);
        Assert.Empty(runtime.WorldEntities);
        Assert.Empty(spatial.Entities);
        Assert.Equal(1, resources.UnregisterCount);
    }

    private static LoadedLandblock EmptyLandblock(uint canonicalId) =>
        new(canonicalId, new LandBlock(), Array.Empty<WorldEntity>());

    private static void ResolveParent(LiveEntityRuntime runtime, uint childGuid) =>
        runtime.ParentAttachments.Resolve(
            childGuid,
            guid => runtime.TryGetSnapshot(guid, out _),
            guid => runtime.TryGetSnapshot(guid, out WorldSession.EntitySpawn spawn)
                ? spawn.InstanceSequence
                : null,
            update => runtime.TryApplyParent(update, out _));

    private static WorldEntity Entity(uint id, uint guid) => new()
    {
        Id = id,
        ServerGuid = guid,
        SourceGfxObjOrSetupId = 0x02000001u,
        Position = System.Numerics.Vector3.Zero,
        Rotation = System.Numerics.Quaternion.Identity,
        MeshRefs = Array.Empty<MeshRef>(),
    };

    private static WorldSession.EntitySpawn Spawn(
        uint guid,
        ushort instance,
        ushort positionSequence,
        uint cell)
    {
        var position = new CreateObject.ServerPosition(
            cell, 10f, 10f, 5f, 1f, 0f, 0f, 0f);
        var timestamps = new PhysicsTimestamps(
            positionSequence, 1, 1, 1, 0, 1, 0, 1, instance);
        var physics = new PhysicsSpawnData(
            RawState: (uint)PhysicsStateFlags.ReportCollisions,
            Position: position,
            Movement: null,
            AnimationFrame: null,
            SetupTableId: 0x02000001u,
            MotionTableId: 0x09000001u,
            SoundTableId: null,
            PhysicsScriptTableId: null,
            Parent: null,
            Children: null,
            Scale: null,
            Friction: null,
            Elasticity: null,
            Translucency: null,
            Velocity: null,
            Acceleration: null,
            AngularVelocity: null,
            DefaultScriptType: null,
            DefaultScriptIntensity: null,
            Timestamps: timestamps);
        return new WorldSession.EntitySpawn(
            guid,
            position,
            0x02000001u,
            Array.Empty<CreateObject.AnimPartChange>(),
            Array.Empty<CreateObject.TextureChange>(),
            Array.Empty<CreateObject.SubPaletteSwap>(),
            null,
            null,
            "fixture",
            null,
            null,
            0x09000001u,
            PhysicsState: (uint)PhysicsStateFlags.ReportCollisions,
            InstanceSequence: instance,
            MovementSequence: 1,
            ServerControlSequence: 1,
            PositionSequence: positionSequence,
            Physics: physics);
    }
}