GodotComponentTest/systems/InteractionSystem.cs

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

public class InteractionSystem : Node
{
    private List<NodePair> _interactionPairs;

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


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

        List<NodePair> invalidInteractionPairs = new List<NodePair>();

        foreach (Tuple<Node, Node> pair in _interactionPairs)
        {
            Node nodeA = pair.Item1;
            Node nodeB = pair.Item2;

            if (nodeA == null || nodeA.IsQueuedForDeletion() || nodeB == null || nodeB.IsQueuedForDeletion()) {
                invalidInteractionPairs.Add(pair);
            }
            
            if (nodeA == null || nodeA.IsQueuedForDeletion())
            {
                IInteractionInterface interactableB = nodeB as IInteractionInterface;
                if (interactableB != null)
                {
                    interactableB.OnInteractionEnd();
                }
            }

            if (nodeB == null || nodeB.IsQueuedForDeletion())
            {
                IInteractionInterface interactableA = nodeA as IInteractionInterface;
                if (interactableA != null)
                {
                    interactableA.OnInteractionEnd();
                }
            }


        }

        foreach (NodePair pair in invalidInteractionPairs)
        {
            _interactionPairs.Remove(pair);
        }
    }

    public void OnStartInteraction(Node nodeA, Node nodeB)
    {
        IInteractionInterface interactableA = nodeA as IInteractionInterface;
        if (interactableA != null)
        {
            interactableA.OnInteractionStart();
        }

        IInteractionInterface interactableB = nodeB as IInteractionInterface;
        if (interactableB != null)
        {
            interactableB.OnInteractionStart();
        }

        NodePair pair = new NodePair(nodeA, nodeB);
        _interactionPairs.Add(new NodePair(nodeA, nodeB));
    }
}