Syntriax.Engine/Engine.Core/Systems/DrawManager.cs

namespace Syntriax.Engine.Core;

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

    private readonly ActiveBehaviourCollectorSorted<IPreDraw> preDrawEntities = new() { SortBy = SortByPriority() };
    private readonly ActiveBehaviourCollectorSorted<IDraw> drawEntities = new() { SortBy = SortByPriority() };
    private readonly ActiveBehaviourCollectorSorted<IPostDraw> postDrawEntities = new() { SortBy = SortByPriority() };

    private void OnPreDraw(IUniverse sender)
    {
        for (int i = preDrawEntities.Count - 1; i >= 0; i--)
            preDrawEntities[i].PreDraw();
    }

    private void OnDraw(IUniverse sender)
    {
        for (int i = drawEntities.Count - 1; i >= 0; i--)
            drawEntities[i].Draw();
    }

    private void OnPostDraw(IUniverse sender)
    {
        for (int i = postDrawEntities.Count - 1; i >= 0; i--)
            postDrawEntities[i].PostDraw();
    }

    protected override void OnEnteringUniverse(IUniverse universe)
    {
        preDrawEntities.Assign(universe);
        drawEntities.Assign(universe);
        postDrawEntities.Assign(universe);

        universe.OnPreDraw.AddListener(OnPreDraw);
        universe.OnDraw.AddListener(OnDraw);
        universe.OnPostDraw.AddListener(OnPostDraw);
    }

    protected override void OnExitingUniverse(IUniverse universe)
    {
        preDrawEntities.Unassign();
        drawEntities.Unassign();
        postDrawEntities.Unassign();

        universe.OnPreDraw.RemoveListener(OnPreDraw);
        universe.OnDraw.RemoveListener(OnDraw);
        universe.OnPostDraw.RemoveListener(OnPostDraw);
    }
}