acdream/src/AcDream.App/Physics/LiveEntityCollisionBuilder.cs

using System.Numerics;
using AcDream.App.World;
using AcDream.Core.Items;
using AcDream.Core.Net;
using AcDream.Core.Physics;
using AcDream.Core.World;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Types;

namespace AcDream.App.Physics;

/// <summary>
/// Immutable input to the canonical shadow registry for one live object.
/// Building is DAT/physics-only and therefore testable without a window or GL
/// context; registration remains one explicit commit.
/// </summary>
internal sealed record LiveEntityCollisionRegistration(
    uint EntityId,
    uint SourceId,
    Vector3 EntityWorldPosition,
    Quaternion EntityWorldRotation,
    IReadOnlyList<ShadowShape> Shapes,
    uint State,
    EntityCollisionFlags Flags,
    float WorldOffsetX,
    float WorldOffsetY,
    uint LandblockId,
    uint SeedCellId);

/// <summary>
/// Ports the live-object collision-shape policy used by
/// <c>CPhysicsObj::FindObjCollisions</c> (0x0050f050), which DISPATCHES
/// rather than unions: every physics-BSP part, ELSE the Setup's CylSpheres,
/// ELSE its Spheres, else nothing (AP-152). The gate itself lives in
/// <see cref="ShadowShapeBuilder.FromSetup"/>.
/// </summary>
/// <remarks>
/// A Setup that yields no shape produces no registration. Retail synthesizes
/// nothing for a shapeless object: <c>CPhysicsObj::FindObjCollisions</c>
/// (0x0050f050) walks CylSpheres or Spheres or the physics BSP, and when
/// <c>CPartArray::GetNumSphere</c> returns zero it branches straight to the
/// epilogue (<c>0x0050f22f je 0x50f31b</c>) returning the seeded
/// <c>OK_TS</c>. <c>CPartArray::GetRadius</c> (0x005180a0) and
/// <c>GetHeight</c> (0x005180b0) are absent from that function's entire call
/// set — <c>Setup.Radius</c>/<c>Height</c> serve attack cones,
/// <c>cylinder_distance</c>, and MoveTo, never collision geometry.
/// </remarks>
internal sealed class LiveEntityCollisionBuilder
{
    private readonly Func<uint, ShadowPartGeometry?> _physicsBspBounds;
    /// <summary>
    /// The dispatch gate, derived from <see cref="_physicsBspBounds"/> so the
    /// two can never disagree (AP-156), and cached once so <see cref="Build"/>
    /// allocates no closure per call — Slice I1's 0 B/resolve budget.
    /// </summary>
    private readonly Func<uint, bool> _hasPhysicsBsp;
    private readonly LiveEntityDefaultPoseResolver _defaultPose;

    public LiveEntityCollisionBuilder(
        PhysicsDataCache physicsData,
        LiveEntityDefaultPoseResolver defaultPose)
        : this(
            id =>
            {
                FlatGfxObjCollisionAsset? asset = physicsData.GetFlatGfxObj(id);
                FlatPhysicsBsp? flat = asset?.PhysicsBsp;
                return flat is { RootIndex: >= 0 }
                    ? ShadowPartGeometry.Create(
                        flat.Nodes[flat.RootIndex].BoundingSphere,
                        asset!.VisualBounds)
                    : (ShadowPartGeometry?)null;
            },
            defaultPose)
    {
        ArgumentNullException.ThrowIfNull(physicsData);
    }

    /// <param name="physicsBspBounds">The part GfxObj's physics-BSP root
    /// bounding sphere AND its authored vertex-array box, or null when it has
    /// no physics BSP. ONE resolver answers every question the builder asks —
    /// "does this part dispatch as BSP?", "where and how big is its flood
    /// sphere?", and "what is its outdoor extent?" — so the dispatch gate and
    /// the emitted geometry cannot disagree, the sphere's radius cannot be
    /// carried while its origin is dropped (AP-156), and the outdoor extent
    /// walk cannot be left without a box (#334).</param>
    internal LiveEntityCollisionBuilder(
        Func<uint, ShadowPartGeometry?> physicsBspBounds,
        LiveEntityDefaultPoseResolver defaultPose)
    {
        _physicsBspBounds = physicsBspBounds
            ?? throw new ArgumentNullException(nameof(physicsBspBounds));
        _hasPhysicsBsp = id => _physicsBspBounds(id) is not null;
        _defaultPose = defaultPose
            ?? throw new ArgumentNullException(nameof(defaultPose));
    }

    /// <summary>
    /// Resolves collision slot zero for every post-AnimPartChanged identity.
    /// This intentionally has no visual-LOD option or Setup-type input.
    /// </summary>
    public static uint[] ResolveEffectivePartIdentities(
        IReadOnlyList<uint> postAnimPartGfxObjIds,
        Func<uint, uint> resolveSlotZero)
    {
        ArgumentNullException.ThrowIfNull(postAnimPartGfxObjIds);
        ArgumentNullException.ThrowIfNull(resolveSlotZero);
        var result = new uint[postAnimPartGfxObjIds.Count];
        for (int i = 0; i < result.Length; i++)
            result[i] = resolveSlotZero(postAnimPartGfxObjIds[i]);
        return result;
    }

    public LiveEntityCollisionRegistration? Build(
        WorldEntity entity,
        Setup setup,
        IReadOnlyList<uint> effectivePartGfxObjIds,
        WorldSession.EntitySpawn spawn,
        LiveEntityRecord exactRecord,
        Vector3 worldOrigin,
        bool retainEmptyPayload = false)
    {
        ArgumentNullException.ThrowIfNull(entity);
        ArgumentNullException.ThrowIfNull(setup);
        ArgumentNullException.ThrowIfNull(effectivePartGfxObjIds);
        ArgumentNullException.ThrowIfNull(exactRecord);
        if (spawn.Position is not { } position)
            return null;
        if (spawn.Guid != exactRecord.ServerGuid
            || spawn.InstanceSequence != exactRecord.Generation
            || !ReferenceEquals(exactRecord.WorldEntity, entity))
        {
            throw new InvalidOperationException(
                "Live collision construction requires the exact materialized record.");
        }

        float scale = spawn.ObjScale ?? 1f;
        IReadOnlyList<Frame>? defaultPose = _defaultPose.Resolve(
            spawn.MotionTableId ?? 0u,
            setup.Parts.Count);
        // One resolver drives both the dispatch gate and the emitted BSP
        // geometry, and FromSetup applies the entity scale to radius and
        // center alike — there is no downstream substitution that could take
        // one and drop the other.
        IReadOnlyList<ShadowShape> shapes = ShadowShapeBuilder.FromSetup(
            setup,
            scale,
            _hasPhysicsBsp,
            partPoseOverride: defaultPose,
            effectivePartGfxObjIds: effectivePartGfxObjIds,
            physicsBspBounds: _physicsBspBounds);

        if (shapes.Count == 0 && !retainEmptyPayload)
            return null;

        EntityCollisionFlags flags = EntityCollisionFlags.HasWeenie;
        if (spawn.ObjectDescriptionFlags is { } descriptionFlags)
            flags |= EntityCollisionFlagsExt.FromPwdBitfield(descriptionFlags);
        if (spawn.ItemType == (uint)ItemType.Creature)
            flags |= EntityCollisionFlags.IsCreature;

        return new LiveEntityCollisionRegistration(
            entity.Id,
            entity.SourceGfxObjOrSetupId,
            entity.Position,
            entity.Rotation,
            shapes,
            (uint)exactRecord.FinalPhysicsState,
            flags,
            worldOrigin.X,
            worldOrigin.Y,
            position.LandblockId,
            position.LandblockId);
    }

    public static void Register(
        ShadowObjectRegistry registry,
        LiveEntityCollisionRegistration registration)
    {
        ArgumentNullException.ThrowIfNull(registry);
        ArgumentNullException.ThrowIfNull(registration);
        registry.RegisterMultiPart(
            registration.EntityId,
            registration.EntityWorldPosition,
            registration.EntityWorldRotation,
            registration.Shapes,
            registration.State,
            registration.Flags,
            registration.WorldOffsetX,
            registration.WorldOffsetY,
            registration.LandblockId,
            registration.SeedCellId,
            isStatic: false);

        if (!PhysicsDiagnostics.ProbeBuildingEnabled)
            return;

        int cylinders = 0;
        int bsps = 0;
        foreach (ShadowShape shape in registration.Shapes)
        {
            if (shape.CollisionType == ShadowCollisionType.Cylinder)
                cylinders++;
            else
                bsps++;
        }
        Console.WriteLine(FormattableString.Invariant(
            $"[entity-source] id=0x{registration.EntityId:X8} entityId=0x{registration.EntityId:X8} src=0x{registration.SourceId:X8} gfxObj=0x{registration.SourceId:X8} lb=0x{registration.LandblockId:X8} shapes=cyl{cylinders}+bsp{bsps} note=server-spawn-root state=0x{registration.State:X8} flags={registration.Flags}"));
    }

    /// <summary>
    /// Commits a retail ObjDesc part-array replacement. A shapeless result
    /// removes the prior payload; a shaped result replaces it without making
    /// a Hidden, parented, or cell-less object collide in world cells.
    /// </summary>
    public static void ReconcileAppearance(
        ShadowObjectRegistry registry,
        uint entityId,
        LiveEntityCollisionRegistration? registration,
        bool suspendIfNew)
    {
        ArgumentNullException.ThrowIfNull(registry);
        if (registration is null)
            return;

        if (registration.EntityId != entityId)
            throw new InvalidOperationException("Collision replacement belongs to a different live entity.");

        registry.ReplaceMultiPartPayload(
            registration.EntityId,
            registration.EntityWorldPosition,
            registration.EntityWorldRotation,
            registration.Shapes,
            registration.State,
            registration.Flags,
            registration.WorldOffsetX,
            registration.WorldOffsetY,
            registration.LandblockId,
            registration.SeedCellId,
            isStatic: false,
            suspendIfNew);
    }
}