using MrGameEng.Core;
using MrGameEng.Graphics;

namespace MrGameEng.Tilemaps;

/// <summary>Wires the tilemaps module into a <see cref="Scene"/>.</summary>
public static class SceneTilemapExtensions
{
    /// <summary>
    /// Adds <see cref="TilemapRenderSystem"/> to the scene's draw phase, right before the
    /// renderer flush. Call from <c>OnLoad</c> after <c>UseRenderer2D()</c>.
    /// </summary>
    public static void UseTilemaps(this Scene scene)
    {
        var renderer =
            scene.Context.Services.GetOrDefault<Renderer2D>()
            ?? throw new InvalidOperationException(
                "UseTilemaps requires UseRenderer2D to be called first."
            );

        var systems = scene.DrawSystems.ChildSystems;
        for (var i = 0; i < systems.Count; i++)
        {
            if (systems[i] is RenderFlushSystem)
            {
                scene.DrawSystems.Insert(i, new TilemapRenderSystem(renderer));
                return;
            }
        }

        throw new InvalidOperationException(
            "RenderFlushSystem not found (is UseRenderer2D wired on this scene?)."
        );
    }
}