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());

    private readonly List<IEnterUniverse> toCallEnterUniverses = new(32);
    private readonly List<IExitUniverse> toCallExitUniverses = new(32);

    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);

        foreach (IUniverseObject universeObject in universe.UniverseObjects)
            OnUniverseObjectRegistered(universe, new(universeObject));

        universe.OnUniverseObjectRegistered.AddListener(OnUniverseObjectRegistered);
        universe.OnUniverseObjectUnRegistered.AddListener(OnUniverseObjectUnRegistered);
    }

    protected override void OnExitedUniverse(IUniverse universe)
    {
        enterUniverses.Unassign();
        exitUniverses.Unassign();

        foreach (IUniverseObject universeObject in universe.UniverseObjects)
            OnUniverseObjectUnRegistered(universe, new(universeObject));

        universe.OnUniverseObjectRegistered.RemoveListener(OnUniverseObjectRegistered);
        universe.OnUniverseObjectUnRegistered.RemoveListener(OnUniverseObjectUnRegistered);
    }

    private void OnUniverseObjectUnRegistered(IUniverse sender, IUniverse.UniverseObjectUnRegisteredArguments args)
    {
        for (int i = toCallExitUniverses.Count - 1; i >= 0; i--)
        {
            IExitUniverse exitUniverse = toCallExitUniverses[i];
            toCallExitUniverses.RemoveAt(i);
            exitUniverse.ExitUniverse(Universe);
        }
    }

    private void OnUniverseObjectRegistered(IUniverse sender, IUniverse.UniverseObjectRegisteredArguments args)
    {
        for (int i = toCallEnterUniverses.Count - 1; i >= 0; i--)
        {
            IEnterUniverse enterUniverse = toCallEnterUniverses[i];
            toCallEnterUniverses.RemoveAt(i);
            enterUniverse.EnterUniverse(Universe);
        }
    }

    private void OnEnterUniverseCollected(IBehaviourCollector<IEnterUniverse> sender, IBehaviourCollector<IEnterUniverse>.BehaviourCollectedArguments args)
    {
        toCallEnterUniverses.Add(args.BehaviourCollected);
    }

    private void OnExitUniverseCollected(IBehaviourCollector<IExitUniverse> sender, IBehaviourCollector<IExitUniverse>.BehaviourCollectedArguments args)
    {
        toCallExitUniverses.Add(args.BehaviourCollected);
    }

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