package speiger.src.coreengine.rendering.shader;

import java.util.List;
import java.util.function.Consumer;
import java.util.function.Supplier;

import org.lwjgl.opengl.GL20;

import speiger.src.collections.objects.lists.ObjectArrayList;
import speiger.src.coreengine.assets.AssetManager;
import speiger.src.coreengine.assets.reloader.IReloadableResource;

public class ShaderTracker implements IReloadableResource
{
	public static final ShaderTracker INSTANCE = new ShaderTracker();
	List<ReloadReference<?>> programs = new ObjectArrayList<>();
	int activeShader = 0;
	boolean reloading = false;
	AssetManager assets;
	
	public void init(AssetManager assets)
	{
		this.assets = assets;
	}
	
	public <T extends ShaderProgram> T register(Supplier<T> creator, Consumer<T> reloader)
	{
		T result = creator.get();
		result.init();
		programs.add(new ReloadReference<>(result, creator, reloader));
		return result;
	}
	
	protected AssetManager getAssets()
	{
		return assets;
	}
	
	void startNextShader(ShaderProgram shader)
	{
		if(shader.getShaderID() == activeShader)
		{
			return;
		}
		activeShader = shader.getShaderID();
		GL20.glUseProgram(activeShader);
	}
	
	void stopShader(ShaderProgram shader)
	{
		if(activeShader == 0)
		{
			return;
		}
		activeShader = 0;
		GL20.glUseProgram(activeShader);
	}
	
	public void stopShader()
	{
		if(activeShader == 0)
		{
			return;
		}
		activeShader = 0;
		GL20.glUseProgram(activeShader);
	}
	
	public boolean isShaderActive()
	{
		return activeShader > 0;
	}
	
	@Override
	public void reload()
	{
		for(int i = 0,m = programs.size();i<m;i++)
		{
			programs.get(i).reload();
		}
	}
	
	@Override
	public void destroy()
	{
		reloading = true;
		for(int i = 0,m = programs.size();i<m;i++)
		{
			programs.get(i).destroy();
		}
		programs.clear();
		reloading = false;
	}
		
	class ReloadReference<T extends ShaderProgram>
	{
		T program;
		Supplier<T> creator;
		Consumer<T> listener;
		
		public ReloadReference(T value, Supplier<T> creator, Consumer<T> listener)
		{
			this.program = value;
			this.creator = creator;
			this.listener = listener;
			program.setReference(this);
		}
		
		private void destroy()
		{
			if(program == null || reloading)
			{
				return;
			}
			program.removeShader();
			program = null;
			listener.accept(null);
		}
		
		public void removeReference()
		{
			destroy();
			if(reloading)
			{
				return;
			}
			programs.remove(this);
		}
		
		public void reload()
		{
			reloading = true;
			program.removeShader();
			program = creator.get();
			program.init();
			program.setReference(this);
			listener.accept(program);
			reloading = false;
		}
	}
}