using System.Collections.Generic;

using Microsoft.Xna.Framework.Graphics;

using Engine.Core;

namespace Engine.Integration.MonoGame;

public class SpriteBatcher : Behaviour, IFirstFrameUpdate, IDraw
{
    private static Comparer<int> SortByPriority() => Comparer<int>.Create((x, y) => y.CompareTo(x));
    private static System.Func<IBehaviour, int> GetPriority() => (b) => b.Priority;

    private ISpriteBatch spriteBatch = null!;
    private MonoGameCamera2D camera2D = null!;

    private readonly RasterizerState rasterizerState = new() { CullMode = CullMode.CullClockwiseFace };
    private readonly ActiveBehaviourCollectorOrdered<int, IDrawableSprite> drawableSprites = new(GetPriority(), SortByPriority());

    public void FirstActiveFrame()
    {
        MonoGameWindowContainer windowContainer = Universe.FindRequiredBehaviour<MonoGameWindowContainer>();
        camera2D = Universe.FindRequiredBehaviour<MonoGameCamera2D>();

        spriteBatch = new SpriteBatchWrapper(windowContainer.Window.GraphicsDevice);
        drawableSprites.Unassign();
        drawableSprites.Assign(Universe);
    }

    public void Draw()
    {
        Matrix4x4 transformMatrix = Matrix4x4.Identity
            .ApplyTranslation(new Vector2D(camera2D.Viewport.X, camera2D.Viewport.Y) * .5f)
            .ApplyScale(new Vector3D(1f, -1f, 1f))
            .ApplyMatrix(camera2D.ViewMatrix)
            .Transposed;

        spriteBatch.Begin(transformMatrix: transformMatrix.ToXnaMatrix(), rasterizerState: rasterizerState);
        for (int i = 0; i < drawableSprites.Count; i++)
            drawableSprites[i].Draw(spriteBatch);
        spriteBatch.End();
    }
}