using System.Collections.Generic;

using Engine.Core;

namespace Engine.Systems.Graphics;

public class TriangleBatcher : Behaviour, IFirstFrameUpdate, ILastFrameUpdate, IDraw
{
    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 BehaviourCollector<ITriangleBatch> triangleBatches = new();
    private readonly ActiveBehaviourCollectorOrdered<int, IDrawableTriangle> drawableShapes = new(GetPriority(), SortByAscendingPriority());

    public void FirstActiveFrame()
    {
        drawableShapes.Assign(Universe);
        triangleBatches.Assign(Universe);
    }

    public void Draw()
    {
        for (int i = 0; i < triangleBatches.Count; i++)
        {
            ITriangleBatch triangleBatch = triangleBatches[i];
            triangleBatch.Begin();
            for (int j = 0; j < drawableShapes.Count; j++)
                drawableShapes[j].Draw(triangleBatch);
            triangleBatch.End();
        }
    }

    public void LastActiveFrame()
    {
        triangleBatches.Unassign();
        drawableShapes.Unassign();
    }
}