using System.Collections.Generic;

namespace Engine.Core;

public class UniverseEntranceManager : Internal.BehaviourIndependent
{
    // We use Ascending order because we are using reverse for loop to call them
    private static Comparer<int> SortByAscendingPriority() => Comparer<int>.Create((x, y) => x.CompareTo(y));
    private static System.Func<IBehaviour, int> GetPriority() => (b) => b.Priority;

    private readonly ActiveBehaviourCollectorOrdered<int, IEnterUniverse> enterUniverses = new(GetPriority(), SortByAscendingPriority());
    private readonly ActiveBehaviourCollectorOrdered<int, IExitUniverse> exitUniverses = new(GetPriority(), SortByAscendingPriority());

    protected override void OnEnteredUniverse(IUniverse universe)
    {
        // FIXME: This causes an issue when the UniverseEntranceManager is already attached to a UniverseObject then registered into a Universe,
        // the enter/exit universe collectors call OnUniverseObjectRegistered internally on Assign, but since the Universe calls the OnUniverseObjectRegistered
        // event it tries to call OnUniverseObjectRegistered again on the same object, causing a duplicate entry error.
        Debug.Assert.AssertTrue(BehaviourController.Count == 1, $"{nameof(UniverseEntranceManager)} must be in it's own {nameof(IUniverseObject)} with no other {nameof(IBehaviour)}s attached at the moment. Failing to do so might cause instantiation or serialization issues.");
        enterUniverses.Assign(universe);
        exitUniverses.Assign(universe);
    }

    protected override void OnExitedUniverse(IUniverse universe)
    {
        enterUniverses.Unassign();
        exitUniverses.Unassign();
    }
    private void OnEnterUniverseCollected(IBehaviourCollector<IEnterUniverse> sender, IBehaviourCollector<IEnterUniverse>.BehaviourCollectedArguments args)
        => args.BehaviourCollected.EnterUniverse(Universe);

    private void OnExitUniverseRemoved(IBehaviourCollector<IExitUniverse> sender, IBehaviourCollector<IExitUniverse>.BehaviourRemovedArguments args)
        => args.BehaviourRemoved.ExitUniverse(Universe);

    public UniverseEntranceManager()
    {
        enterUniverses.OnCollected.AddListener(OnEnterUniverseCollected);
        exitUniverses.OnRemoved.AddListener(OnExitUniverseRemoved);
    }
}