/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/

package com.badlogic.gdx;

import com.badlogic.gdx.utils.Clipboard;

/** <p>
 * An <code>Application</code> is the main entry point of your project. It sets up a window and rendering surface and manages the
 * different aspects of your application, namely {@link Graphics}, {@link Audio}, {@link Input} and {@link Files}. Think of an
 * Application being equivalent to Swing's <code>JFrame</code> or Android's <code>Activity</code>.
 * </p>
 * 
 * <p>
 * An application can be an instance of any of the following:
 * <ul>
 * <li>a desktop application (see <code>JglfwApplication</code> found in gdx-backends-jglfw.jar)</li>
 * <li>an Android application (see <code>AndroidApplication</code> found in gdx-backends-android.jar)</li>
 * <li>a HTML5 application (see <code>GwtApplication</code> found in gdx-backends-gwt.jar)</li>
 * <li>an iOS application (see <code>IOSApplication</code> found in gdx-backends-iosmonotouch.jar)</li>
 * </ul>
 * Each application class has it's own startup and
 * initialization methods. Please refer to their documentation for more information.
 * </p>
 * 
 * <p>
 * While game programmers are used to having a main loop, libgdx employs a different concept to accommodate the event based nature
 * of Android applications a little more. You application logic must be implemented in a {@link ApplicationListener} which has
 * methods that get called by the Application when the application is created, resumed, paused, disposed or rendered. As a
 * developer you will simply implement the ApplicationListener interface and fill in the functionality accordingly. The
 * ApplicationListener is provided to a concrete Application instance as a parameter to the constructor or another initialization
 * method. Please refer to the documentation of the Application implementations for more information. Note that the
 * ApplicationListener can be provided to any Application implementation. This means that you only need to write your program
 * logic once and have it run on different platforms by passing it to a concrete Application implementation.
 * </p>
 * 
 * <p>
 * The Application interface provides you with a set of modules for graphics, audio, input and file i/o.
 * </p>
 * 
 * <p>
 * {@link Graphics} offers you various methods to output visuals to the screen. This is achieved via OpenGL ES 1.0, 1.1 or 2.0
 * depending on what's available an the platform. On the desktop the features of OpenGL ES 2.0 are emulated via desktop OpenGL. On
 * Android the functionality of the Java OpenGL ES bindings is used.
 * </p>
 * 
 * <p>
 * {@link Audio} offers you various methods to output and record sound and music. This is achieved via the Java Sound API on the
 * desktop. On Android the Android media framework is used.
 * </p>
 * 
 * <p>
 * {@link Input} offers you various methods to poll user input from the keyboard, touch screen, mouse and accelerometer.
 * Additionally you can implement an {@link InputProcessor} and use it with {@link Input#setInputProcessor(InputProcessor)} to
 * receive input events.
 * </p>
 * 
 * <p>
 * {@link Files} offers you various methods to access internal and external files. An internal file is a file that is stored near
 * your application. On Android internal files are equivalent to assets. On the desktop the classpath is first scanned for the
 * specified file. If that fails then the root directory of your application is used for a look up. External files are resources
 * you create in your application and write to an external storage. On Android external files reside on the SD-card, on the
 * desktop external files are written to a users home directory. If you know what you are doing you can also specify absolute file names.
 * Absolute filenames are not portable, so take great care when using this feature.
 * </p>
 * 
 * <p>
 * {@link Net} offers you various methods to perform network operations, such as performing HTTP requests, or creating server and
 * client sockets for more elaborate network programming.
 * </p>
 * 
 * <p>
 * The <code>Application</code> also has a set of methods that you can use to query specific information such as the operating
 * system the application is currently running on and so forth. This allows you to have operating system dependent code paths. It
 * is however not recommended to use this facilities.
 * </p>
 * 
 * <p>
 * The <code>Application</code> also has a simple logging method which will print to standard out on the desktop and to logcat on
 * Android.
 * </p>
 * 
 * @author mzechner */
public interface Application {
	/** Enumeration of possible {@link Application} types
	 * 
	 * @author mzechner */
	public enum ApplicationType {
		Android, Desktop, Applet, WebGL, iOS
	}

	public static final int LOG_NONE = 0;
	public static final int LOG_DEBUG = 3;
	public static final int LOG_INFO = 2;
	public static final int LOG_ERROR = 1;

	/** @return the {@link ApplicationListener} instance */ 
	public ApplicationListener getApplicationListener ();
	
	/** @return the {@link Graphics} instance */
	public Graphics getGraphics ();

	/** @return the {@link Audio} instance */
	public Audio getAudio ();

	/** @return the {@link Input} instance */
	public Input getInput ();

	/** @return the {@link Files} instance */
	public Files getFiles ();

	/** @return the {@link Net} instance */
	public Net getNet ();

	/** Logs a message to the console or logcat */
	public void log (String tag, String message);

	/** Logs a message to the console or logcat */
	public void log (String tag, String message, Exception exception);

	/** Logs an error message to the console or logcat */
	public void error (String tag, String message);

	/** Logs an error message to the console or logcat */
	public void error (String tag, String message, Throwable exception);

	/** Logs a debug message to the console or logcat */
	public void debug (String tag, String message);

	/** Logs a debug message to the console or logcat */
	public void debug (String tag, String message, Throwable exception);

	/** Sets the log level. {@link #LOG_NONE} will mute all log output. {@link #LOG_ERROR} will only let error messages through.
	 * {@link #LOG_INFO} will let all non-debug messages through, and {@link #LOG_DEBUG} will let all messages through.
	 * @param logLevel {@link #LOG_NONE}, {@link #LOG_ERROR}, {@link #LOG_INFO}, {@link #LOG_DEBUG}. */
	public void setLogLevel (int logLevel);

	/** Gets the log level. */
	public int getLogLevel();

	/** @return what {@link ApplicationType} this application has, e.g. Android or Desktop */
	public ApplicationType getType ();

	/** @return the Android API level on Android, the major OS version on iOS (5, 6, 7, ..), or 0 on the desktop. */
	public int getVersion ();

	/** @return the Java heap memory use in bytes */
	public long getJavaHeap ();

	/** @return the Native heap memory use in bytes */
	public long getNativeHeap ();

	/** Returns the {@link Preferences} instance of this Application. It can be used to store application settings across runs.
	 * @param name the name of the preferences, must be useable as a file name.
	 * @return the preferences. */
	public Preferences getPreferences (String name);

	public Clipboard getClipboard ();

	/** Posts a {@link Runnable} on the main loop thread.
	 * 
	 * @param runnable the runnable. */
	public void postRunnable (Runnable runnable);

	/** Schedule an exit from the application. On android, this will cause a call to pause() and dispose() some time in the future, it will not
	 * immediately finish your application. */
	public void exit ();
	
	/**
	 * Adds a new {@link LifecycleListener} to the application. This can be
	 * used by extensions to hook into the lifecycle more easily. The
	 * {@link ApplicationListener} methods are sufficient for application
	 * level development.
	 * @param listener
	 */
	public void addLifecycleListener(LifecycleListener listener);
	
	/**
	 * Removes the {@link LifecycleListener}.
	 * @param listener
	 */
	public void removeLifecycleListener(LifecycleListener listener);
}
