Syntriax.Engine/Engine.Core/Systems/UpdateManager.cs

using System.Collections.Generic;

namespace Syntriax.Engine.Core;

public class UpdateManager : UniverseObject
{
    private static System.Comparison<IBehaviour> SortByPriority() => (x, y) => y.Priority.CompareTo(x.Priority);

    private readonly ActiveBehaviourCollectorSorted<IFirstFrameUpdate> firstFrameUpdates = new() { SortBy = SortByPriority() };
    private readonly ActiveBehaviourCollectorSorted<IPreUpdate> preUpdateEntities = new() { SortBy = SortByPriority() };
    private readonly ActiveBehaviourCollectorSorted<IUpdate> updateEntities = new() { SortBy = SortByPriority() };
    private readonly ActiveBehaviourCollectorSorted<IPostUpdate> postUpdateEntities = new() { SortBy = SortByPriority() };

    private readonly List<IFirstFrameUpdate> toCallFirstFrameUpdates = new(32);

    protected override void OnEnteringUniverse(IUniverse universe)
    {
        firstFrameUpdates.Assign(universe);
        preUpdateEntities.Assign(universe);
        updateEntities.Assign(universe);
        postUpdateEntities.Assign(universe);

        universe.OnPreUpdate += OnPreUpdate;
        universe.OnUpdate += OnUpdate;
        universe.OnPostUpdate += OnPostUpdate;
    }

    protected override void OnExitingUniverse(IUniverse universe)
    {
        firstFrameUpdates.Unassign();
        preUpdateEntities.Unassign();
        updateEntities.Unassign();
        postUpdateEntities.Unassign();

        universe.OnPreUpdate -= OnPreUpdate;
        universe.OnUpdate -= OnUpdate;
        universe.OnPostUpdate -= OnPostUpdate;
    }

    private void OnPreUpdate(IUniverse sender, UniverseTime engineTime)
    {
        for (int i = toCallFirstFrameUpdates.Count - 1; i >= 0; i--)
        {
            toCallFirstFrameUpdates[i].FirstActiveFrame();
            toCallFirstFrameUpdates.RemoveAt(i);
        }

        for (int i = preUpdateEntities.Count - 1; i >= 0; i--)
            preUpdateEntities[i].PreUpdate();
    }

    private void OnUpdate(IUniverse sender, UniverseTime engineTime)
    {
        for (int i = updateEntities.Count - 1; i >= 0; i--)
            updateEntities[i].Update();
    }

    private void OnPostUpdate(IUniverse sender, UniverseTime engineTime)
    {
        for (int i = postUpdateEntities.Count - 1; i >= 0; i--)
            postUpdateEntities[i].PostUpdate();
    }

    private void OnFirstFrameCollected(IBehaviourCollector<IFirstFrameUpdate> sender, IFirstFrameUpdate behaviourCollected)
    {
        toCallFirstFrameUpdates.Add(behaviourCollected);
    }

    public UpdateManager()
    {
        firstFrameUpdates.OnCollected += OnFirstFrameCollected;
    }
}