Syntriax.Engine/Engine.Integration/Engine.Integration.MonoGame/Behaviours/LoadContentManager.cs

using System.Collections.Generic;

using Engine.Core;

namespace Engine.Integration.MonoGame;

public class LoadContentManager : Behaviour, IEnterUniverse, IExitUniverse, IFirstFrameUpdate
{
    // 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, ILoadContent> loadContents = new(GetPriority(), SortByAscendingPriority());
    private readonly List<ILoadContent> toCallLoadContents = new(32);

    private MonoGameWindowContainer monoGameWindowContainer = null!;

    public void FirstActiveFrame()
    {
        monoGameWindowContainer = Universe.FindRequiredBehaviour<MonoGameWindowContainer>();
    }

    public void EnterUniverse(IUniverse universe)
    {
        loadContents.Assign(universe);

        universe.OnPreUpdate.AddListener(OnPreUpdate);
    }

    public void ExitUniverse(IUniverse universe)
    {
        loadContents.Unassign();

        universe.OnPreUpdate.RemoveListener(OnPreUpdate);
    }

    private void OnPreUpdate(IUniverse sender, IUniverse.UpdateArguments args)
    {
        for (int i = toCallLoadContents.Count - 1; i >= 0; i--)
        {
            toCallLoadContents[i].LoadContent(monoGameWindowContainer.Window.Content);
            toCallLoadContents.RemoveAt(i);
        }
    }

    private void OnFirstFrameCollected(IBehaviourCollector<ILoadContent> sender, IBehaviourCollector<ILoadContent>.BehaviourCollectedArguments args)
    {
        toCallLoadContents.Add(args.BehaviourCollected);
    }

    public LoadContentManager()
    {
        loadContents.OnCollected.AddListener(OnFirstFrameCollected);
    }
}