acdream/src/AcDream.App/Rendering/Selection/RetailSelectionScene.cs

using System.Numerics;
using AcDream.App.Rendering.Scene;
using AcDream.Core.Selection;
using AcDream.Core.World;

namespace AcDream.App.Rendering.Selection;

/// <summary>
/// Render-thread owner of the last complete set of visible selectable parts.
/// The renderer builds one frame while input queries the previously completed
/// frame, avoiding partial visibility state during multi-slice portal drawing.
/// </summary>
internal interface IWorldSceneSelectionFrame
{
    void BeginFrame();

    void CompleteFrame();

    void AbortFrame();
}

internal sealed class RetailSelectionScene :
    IRetailSelectionRenderSink,
    IRetailSelectionLightingSource,
    IWorldSceneSelectionFrame
{
    private readonly IRetailSelectionGeometrySource _geometry;
    private readonly RetailSelectionLightingPulse _lightingPulse;
    private List<RetailSelectionPart> _building = new();
    private List<RetailSelectionPart> _published = new();
    private readonly HashSet<PartKey> _buildingKeys = new();
    private FrustumPlanes? _viewFrustum;
    private ICurrentRenderSelectionObserver? _currentRenderSceneObserver;

    private readonly record struct PartKey(uint LocalEntityId, int PartIndex, uint GfxObjId);

    public RetailSelectionScene(
        IRetailSelectionGeometrySource geometry,
        RetailSelectionLightingPulse? lightingPulse = null)
    {
        _geometry = geometry ?? throw new ArgumentNullException(nameof(geometry));
        _lightingPulse = lightingPulse ?? new RetailSelectionLightingPulse();
    }

    /// <summary>
    /// Starts retail's SmartBox click pulse independently of persistent target
    /// selection. Examine, use, and targeted-use clicks receive the same pulse.
    /// </summary>
    public void BeginLightingPulse(uint serverGuid, uint localEntityId)
        => _lightingPulse.Start(serverGuid, localEntityId);

    public void TickLighting()
        => _lightingPulse.Tick();

    public bool TryGetLighting(
        uint serverGuid,
        uint localEntityId,
        out RetailSelectionLighting lighting)
        => _lightingPulse.TryGet(serverGuid, localEntityId, out lighting);

    internal void SetCurrentRenderSceneObserver(
        ICurrentRenderSelectionObserver? observer) =>
        _currentRenderSceneObserver = observer;

    /// <summary>Clears every session-owned frame and material pulse.</summary>
    public void Reset()
    {
        _currentRenderSceneObserver?.AbortSelectionFrame();
        _building.Clear();
        _published.Clear();
        _buildingKeys.Clear();
        _viewFrustum = null;
        _lightingPulse.Clear();
    }

    public void BeginFrame()
    {
        _building.Clear();
        _buildingKeys.Clear();
        _viewFrustum = null;
        _currentRenderSceneObserver?.BeginSelectionFrame();
    }

    /// <summary>
    /// Supplies retail DrawMesh's current view-cone gate. Animated entities
    /// deliberately bypass acdream's coarse entity-AABB CPU cull, so this
    /// per-part drawing sphere check is the load-bearing retail equivalent.
    /// </summary>
    public void SetViewFrustum(FrustumPlanes viewFrustum)
        => _viewFrustum = viewFrustum;

    public void AddVisiblePart(
        WorldEntity entity,
        int partIndex,
        uint gfxObjId,
        Matrix4x4 partWorld)
    {
        if (entity.ServerGuid == 0u)
            return;

        if (!_buildingKeys.Add(new PartKey(entity.Id, partIndex, gfxObjId)))
            return;
        RetailSelectionMesh? mesh = _geometry.Resolve(gfxObjId);
        if (mesh is null)
            return;
        if (_viewFrustum is not { } frustum
            || !DrawingSphereIntersectsFrustum(mesh, partWorld, frustum))
            return;

        _building.Add(new RetailSelectionPart(
            entity.ServerGuid,
            entity.Id,
            partIndex,
            partWorld,
            mesh));
        _currentRenderSceneObserver?.ObserveSelectionPart(
            entity.ServerGuid,
            entity.Id,
            partIndex,
            gfxObjId,
            partWorld,
            mesh);
    }

    public void CompleteFrame()
    {
        (_published, _building) = (_building, _published);
        _currentRenderSceneObserver?.CompleteSelectionFrame();
    }

    /// <summary>Discards the incomplete building frame and preserves the last
    /// completely published selection product.</summary>
    public void AbortFrame()
    {
        _currentRenderSceneObserver?.AbortSelectionFrame();
        _building.Clear();
        _buildingKeys.Clear();
        _viewFrustum = null;
    }

    public RetailSelectionHit? Pick(
        float mouseX,
        float mouseY,
        Vector2 viewport,
        Matrix4x4 view,
        Matrix4x4 projection,
        uint skipServerGuid)
    {
        if (viewport.X <= 0f || viewport.Y <= 0f)
            return null;
        var ray = WorldPicker.BuildRay(
            mouseX, mouseY, viewport.X, viewport.Y, view, projection);
        return RetailWorldPicker.Pick(
            ray.Origin, ray.Direction, _published, skipServerGuid);
    }

    internal static bool DrawingSphereIntersectsFrustum(
        RetailSelectionMesh mesh,
        Matrix4x4 localToWorld,
        FrustumPlanes frustum)
    {
        Vector3 center = Vector3.Transform(mesh.SphereCenter, localToWorld);
        float scaleX = new Vector3(localToWorld.M11, localToWorld.M12, localToWorld.M13).Length();
        float scaleY = new Vector3(localToWorld.M21, localToWorld.M22, localToWorld.M23).Length();
        float scaleZ = new Vector3(localToWorld.M31, localToWorld.M32, localToWorld.M33).Length();
        float radius = mesh.SphereRadius * MathF.Max(scaleX, MathF.Max(scaleY, scaleZ));
        return TestPlane(frustum.Left, center, radius)
            && TestPlane(frustum.Right, center, radius)
            && TestPlane(frustum.Bottom, center, radius)
            && TestPlane(frustum.Top, center, radius)
            && TestPlane(frustum.Near, center, radius)
            && TestPlane(frustum.Far, center, radius);
    }

    private static bool TestPlane(Vector4 plane, Vector3 center, float radius)
        => plane.X * center.X + plane.Y * center.Y + plane.Z * center.Z + plane.W >= -radius;
}