Syntriax.Engine/Engine.Physics2D/Collider2DBase.cs

using Engine.Core;

namespace Engine.Physics2D;

public abstract class Collider2DBase : Behaviour2D, ICollider2D
{
    public Event<ICollider2D, CollisionDetectionInformation> OnCollisionDetected { get; } = new();
    public Event<ICollider2D, CollisionDetectionInformation> OnCollisionResolved { get; } = new();
    public Event<ICollider2D, ICollider2D> OnTriggered { get; } = new();

    private readonly Event<IBehaviourController, IBehaviourController.BehaviourAddedArguments>.EventHandler delegateOnBehaviourAddedToController = null!;
    private readonly Event<IBehaviourController, IBehaviourController.BehaviourRemovedArguments>.EventHandler delegateOnBehaviourRemovedFromController = null!;
    private readonly Event<ITransform2D, ITransform2D.PositionChangedArguments>.EventHandler delegateSetNeedsRecalculationFromPosition = null!;
    private readonly Event<ITransform2D, ITransform2D.RotationChangedArguments>.EventHandler delegateSetNeedsRecalculationFromRotation = null!;
    private readonly Event<ITransform2D, ITransform2D.ScaleChangedArguments>.EventHandler delegateSetNeedsRecalculationFromScale = null!;
    private readonly Event<IUniverseObject, IUniverseObject.ParentChangedArguments>.EventHandler delegateUpdateRigidBody2D = null!;

    protected bool NeedsRecalculation { get; set; } = true;
    protected IRigidBody2D? _rigidBody2D = null;

    protected Collider2DBase()
    {
        delegateOnBehaviourAddedToController = OnBehaviourAddedToController;
        delegateOnBehaviourRemovedFromController = OnBehaviourRemovedFromController;
        delegateSetNeedsRecalculationFromPosition = SetNeedsRecalculationFromPosition;
        delegateSetNeedsRecalculationFromRotation = SetNeedsRecalculationFromRotation;
        delegateSetNeedsRecalculationFromScale = SetNeedsRecalculationFromScale;
        delegateUpdateRigidBody2D = UpdateRigidBody2D;
    }

    public IRigidBody2D? RigidBody2D => _rigidBody2D;
    public bool IsTrigger { get; set; } = false;

    public void Recalculate()
    {
        if (!NeedsRecalculation)
            return;

        CalculateCollider();
        NeedsRecalculation = false;
    }

    public abstract void CalculateCollider();

    protected override void OnInitialize()
    {
        base.OnInitialize();

        BehaviourController.TryGetBehaviourInParent(out _rigidBody2D);

        BehaviourController.OnBehaviourAdded.AddListener(delegateOnBehaviourAddedToController);
        BehaviourController.OnBehaviourRemoved.AddListener(delegateOnBehaviourRemovedFromController);

        Transform.OnPositionChanged.AddListener(delegateSetNeedsRecalculationFromPosition);
        Transform.OnRotationChanged.AddListener(delegateSetNeedsRecalculationFromRotation);
        Transform.OnScaleChanged.AddListener(delegateSetNeedsRecalculationFromScale);
        UniverseObject.OnParentChanged.AddListener(delegateUpdateRigidBody2D);
    }

    private void UpdateRigidBody2D(IUniverseObject sender, IUniverseObject.ParentChangedArguments args)
    {
        BehaviourController.TryGetBehaviourInParent(out _rigidBody2D);
    }

    private void OnBehaviourAddedToController(IBehaviourController sender, IBehaviourController.BehaviourAddedArguments args)
    {
        if (args.BehaviourAdded is IRigidBody2D rigidBody)
            _rigidBody2D = rigidBody;
    }

    private void OnBehaviourRemovedFromController(IBehaviourController sender, IBehaviourController.BehaviourRemovedArguments args)
    {
        if (args.BehaviourRemoved is IRigidBody2D)
            _rigidBody2D = null;
    }

    private void SetNeedsRecalculationFromPosition(ITransform2D sender, ITransform2D.PositionChangedArguments args) => NeedsRecalculation = true;
    private void SetNeedsRecalculationFromScale(ITransform2D sender, ITransform2D.ScaleChangedArguments args) => NeedsRecalculation = true;
    private void SetNeedsRecalculationFromRotation(ITransform2D sender, ITransform2D.RotationChangedArguments args) => NeedsRecalculation = true;

    protected override void OnFinalize()
    {
        base.OnFinalize();

        BehaviourController.OnBehaviourAdded.RemoveListener(delegateOnBehaviourAddedToController);
        BehaviourController.OnBehaviourRemoved.RemoveListener(delegateOnBehaviourRemovedFromController);
        Transform.OnScaleChanged.RemoveListener(delegateSetNeedsRecalculationFromScale);

        Transform.OnPositionChanged.RemoveListener(delegateSetNeedsRecalculationFromPosition);
        Transform.OnRotationChanged.RemoveListener(delegateSetNeedsRecalculationFromRotation);
    }

    public void Detect(CollisionDetectionInformation collisionDetectionInformation) => OnCollisionDetected?.Invoke(this, collisionDetectionInformation);
    public void Resolve(CollisionDetectionInformation collisionDetectionInformation) => OnCollisionResolved?.Invoke(this, collisionDetectionInformation);
    public void Trigger(ICollider2D initiator) => OnTriggered?.Invoke(this, initiator);
}