package ei.engine;

import org.lwjgl.Sys;
import org.lwjgl.input.Keyboard;
import org.lwjgl.input.Mouse;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GL11;

public class LWJGLGameWindow {
	private boolean exit = false;
	private int width;
	private int height;
	private int fps;
	private boolean fullscreen;
	private String title;

	public LWJGLGameWindow(String title){
		this(800, 600, 60, false, title);
	}
	
	public LWJGLGameWindow(int width, int height, int fps, boolean fullscreen, String title){
		this.width = width;
		this.height = height;
		this.fps = fps;
		this.fullscreen = fullscreen;
		this.title = title;
		
	    try {
	    	initDisplay();
	    	run();
	    } catch (Exception e) {
	    	e.printStackTrace(System.err);
	    	Sys.alert(title, "An error occured and the game will exit.");
	    } finally {
	    	cleanup();
	    }
	    System.exit(0);		
	}

	 
	/**
	 * Initialise the game
	 * @throws Exception if init fails
	 */
	private void initDisplay() throws Exception {		
		DisplayMode dm = new DisplayMode(width, height);
		Display.setDisplayMode(dm); 
		
		Display.setTitle(title);
		Display.setFullscreen(fullscreen);

		// grab the mouse, dont want that hideous cursor when we're playing!
		Mouse.setGrabbed(true);

		// enable textures since we're going to use these for our sprites
		GL11.glEnable(GL11.GL_TEXTURE_2D);
		
		// disable the OpenGL depth test since we're rendering 2D graphics
		GL11.glDisable(GL11.GL_DEPTH_TEST);		
		GL11.glMatrixMode(GL11.GL_PROJECTION);
		GL11.glLoadIdentity();
		
		// Enable vsync if we can (due to how OpenGL works, it cannot be guarenteed to always work)
		Display.setVSyncEnabled(true);

		// Create the display window
		Display.create();
	}

	/**
	 * Runs the game (the "main loop")
	 */
	private void run() {	 
		while (!exit) {
			// Always call Window.update(), all the time - it does some behind the
			// scenes work, and also displays the rendered output
			Display.update();

			// Check for close requests
			if (Display.isCloseRequested()) {
				exit = true;
			} 

			// The window is in the foreground, so we should play the game
			else if (Display.isActive()) {
				update();
				mainRender();
				Display.sync(fps);
			} 

			// The window is not in the foreground, so we can allow other stuff to run and
			// infrequently update
			else {
				try {
					Thread.sleep(100);
				} catch (InterruptedException e) {}
				update();

				// Only bother rendering if the window is visible or dirty
				if (Display.isVisible() || Display.isDirty()) {
					mainRender();
				}
			}
		}
	}

	/**
	 * Do any game-specific cleanup
	 */
	protected void cleanup() {
		// Close the window
		Display.destroy();
	}

	/**
	 * Do all calculations, handle input, etc.
	 */
	protected void update() {
		// Example input handler: we'll check for the ESC key and finish the game instantly when it's pressed
		if (Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) {
			exit = true;
		}
	}
	
	/**
	 * Render the current frame
	 */
	private void mainRender() {
		// clear the screen
		GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);
		GL11.glMatrixMode(GL11.GL_MODELVIEW);
		GL11.glLoadIdentity();
		
		render();

		Display.update();
	}
	
	protected void render(){
		
	}
	
}