/*
 * GameThread.cs - Controls the main loop which executes opcodes of a Level9
 *                 game.
 *
 * Copyright (C) 2004 - 2011 Andreas Scherrer
 *
 * This is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this software; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
 * USA.
 */

using System;
using System.Threading;

namespace Level9
{
	/// <summary>
	/// Controls the main loop which executes opcodes of a Level 9 game.
	/// </summary>
	public class GameThread
	{
		// -- Attributes -----------------------------------------------------

		/// <summary>
		/// The current game thread instance.
		/// </summary>
		static Thread gameThread = null;

		/// <summary>
		/// This property indicates whether the game thread is running.
		/// </summary>
		static bool isRunning = false;

		/// <summary>
		/// This property indicates whether the game thread is sleeping.
		/// </summary>
		static bool isSleeping = false;

		/// <summary>
		/// This property indicates whether the game thread should be stopped.
		/// </summary>
		static bool stopRequest = false;

		// -- Methods --------------------------------------------------------

		/// <summary>
		/// Starts a new game thread.
		/// </summary>
		public static void Start()
		{
			if (gameThread == null) {
				gameThread  = new Thread(new ThreadStart(ThreadProc));
				isRunning   = true;
				isSleeping  = false;
				stopRequest = false;
				gameThread.Start();
				Logger.Log(typeof(GameThread), "Start");
			}
		}

		/// <summary>
		/// Stops a game thread.
		/// </summary>
		public static void Stop()
		{
			if (gameThread != null) {
				Logger.Log(typeof(GameThread), "Stop: "
					+ gameThread.ThreadState + " -> Stop");
				stopRequest = true;
				Interpreter.StopGame();
				if (isSleeping) {
					Resume();
				}
			}
		}

		/// <summary>
		/// Interrupts a running game thread.
		/// </summary>
		public static void Sleep()
		{
			if (gameThread != null && !isSleeping) {
				Logger.Log(typeof(GameThread), "Sleep: "
					+ gameThread.ThreadState + " -> Sleep");
				try {
					isSleeping = true;
					Thread.Sleep(Timeout.Infinite);
				}
				catch (ThreadInterruptedException) {
					isSleeping = false;
					Logger.Log(typeof(GameThread), "Sleep: Interrupted");
				}
			}
		}

		/// <summary>
		/// Resumes a sleeping game thread.
		/// </summary>
		public static void Resume()
		{
			if (gameThread != null && isSleeping) {
				Logger.Log(typeof(GameThread), "Resume: "
					+ gameThread.ThreadState + " -> Resume");
				gameThread.Interrupt();
			}
		}

		/// <summary>
		/// Joins a game thread.
		/// </summary>
		public static void Join()
		{
			if (gameThread != null) {
				gameThread.Join();
			}
		}

		/// <summary>
		/// The thread procedure.
		/// </summary>
		static void ThreadProc()
		{
			while(Interpreter.RunGame());
			isRunning = false;
			gameThread = null;
			Interpreter.os_flush();
			Logger.Log(typeof(GameThread), "ThreadProc: Exit");
		}

		// -- Accessors ------------------------------------------------------

		/// <summary>
		/// Gets a value that indicates whether the game thread should be
		/// stopped.
		/// </summary>
		public static bool StopRequest
		{
			get {
				return stopRequest;
			}
		}

		/// <summary>
		/// Gets a value that indicates whether the game thread is running.
		/// </summary>
		public static bool IsRunning
		{
			get {
				return isRunning;
			}
		}

		/// <summary>
		/// Gets a value that indicates whether the game thread is sleeping.
		/// </summary>
		public static bool IsSleeping
		{
			get {
				return isSleeping;
			}
		}
	}
}