GodotComponentTest/systems/InteractionSystem.cs

using System.Collections.Generic;
using Godot;
using GodotComponentTest.components;
using GodotComponentTest.entities;
using NodePair = System.Tuple<Godot.Node, Godot.Node>;

public class InteractionSystem : Node {
    private List<InteractionComponent> _activeInteractions;

    // Called when the node enters the scene tree for the first time.
    public override void _Ready() {
        _activeInteractions = new List<InteractionComponent>();
    }

    public override void _Process(float delta) {
        base._Process(delta);

        List<InteractionComponent> endedInteractions = new();

        foreach (InteractionComponent interaction in _activeInteractions) {
            Spatial owningEntity = interaction.OwningEntity;
            Spatial targetEntity = interaction.TargetEntity;

            if (owningEntity == null || owningEntity.IsQueuedForDeletion() || targetEntity == null ||
                targetEntity.IsQueuedForDeletion()) {
                interaction.hasStopped = true;
            }

            if (interaction.hasStopped) {
                IInteractionInterface interactableA = owningEntity as IInteractionInterface;
                if (interactableA != null) {
                    interactableA.OnInteractionEnd();
                    interactableA.InteractionComponent = null;
                }

                IInteractionInterface interactableB = targetEntity as IInteractionInterface;
                if (interactableB != null) {
                    interactableB.OnInteractionEnd();
                    interactableB.InteractionComponent = null;
                }

                endedInteractions.Add(interaction);
            }
        }

        foreach (InteractionComponent interaction in endedInteractions)
            _activeInteractions.Remove(interaction);
    }

    public void OnStartInteraction(Entity owningEntity, Entity targetEntity) {
        InteractionComponent interactionComponent = new();
        interactionComponent.OwningEntity = owningEntity;
        interactionComponent.TargetEntity = targetEntity;

        ConnectInteractionSignals(owningEntity, interactionComponent);
        ConnectInteractionSignals(targetEntity, interactionComponent);

        interactionComponent.EmitSignal("InteractionStart");

        _activeInteractions.Add(interactionComponent);
    }

    private static void ConnectInteractionSignals(Entity entity, InteractionComponent interactionComponent) {
        IInteractionInterface interactable = entity as IInteractionInterface;
        if (interactable != null) {
            interactable.InteractionComponent = interactionComponent;
            interactionComponent.Connect("InteractionStart", entity, nameof(interactable.OnInteractionStart));
            interactionComponent.Connect("InteractionEnd", entity, nameof(interactable.OnInteractionEnd));
        }
    }
}