source: trunk/JavaHelperLib/src/de/ugoe/cs/util/console/Console.java @ 8

package de.ugoe.cs.util.console;

import java.util.ArrayList;
import java.util.List;

import de.ugoe.cs.util.StringTools;


/**
 * <p>
 * This class provides an interface for communication with the user without have
 * to rely on a specific user interface. Thus, it can be used to decouple the
 * programs logic from its user interface.
 * </p>
 * <p>
 * {@link Command} objects can be used to execute behavior.
 * </p>
 * <p>
 * To send output to the user interface, the Observer pattern is used. The
 * Console is an observable, the concrete user interfaces are the observers. The
 * interface for the observers is {@link ConsoleObserver}.
 * </p>
 * 
 * @author Steffen Herbold
 */
public final class Console {

        /**
         * <p>
         * List of observers.
         * </p>
         */
        private List<ConsoleObserver> observers;

        /**
         * <p>
         * Handle of the Console instance.
         * </p>
         */
        private static Console theInstance = null;

        /**
         * <p>
         * Returns the instance of Console. If no instances exists yet, a new one is
         * created.
         * </p>
         * 
         * @return instance of this class
         */
        public static Console getInstance() {
                if (theInstance == null) {
                        theInstance = new Console();
                }
                return theInstance;
        }

        /**
         * <p>
         * Creates a new Console. Private to prevent multiple instances (Singleton).
         * </p>
         */
        private Console() {
                observers = new ArrayList<ConsoleObserver>();
        }

        /**
         * <p>
         * Register a new observer.
         * </p>
         * 
         * @param observer
         *            observer to be added
         */
        public void registerObserver(ConsoleObserver observer) {
                observers.add(observer);
        }

        /**
         * <p>
         * Remove an observer. If the observer is not found, nothing is done.
         * </p>
         * 
         * @param observer
         *            observer to be removed
         */
        public void deleteObserver(ConsoleObserver observer) {
                observers.remove(observer);
        }

        /**
         * <p>
         * Sends a message to all observers containing the message that was passed
         * to this function.
         * </p>
         * 
         * @param msg
         *            message that is send to the console
         */
        public static void print(String msg) {
                if (theInstance == null) {
                        getInstance();
                }
                for (ConsoleObserver observer : theInstance.observers) {
                        observer.updateText(msg);
                }
        }

        /**
         * <p>
         * Sends a message to all observers containing the message that was passed
         * to this function and adds an endline to the message.
         * </p>
         * 
         * @param msg
         *            message that is send to the observers
         */
        public static void println(String msg) {
                if (theInstance == null) {
                        getInstance();
                }
                for (ConsoleObserver observer : theInstance.observers) {
                        observer.updateText(msg
                                        + StringTools.ENDLINE);
                }
        }

        /**
         * <p>
         * Sends an error message to all observers containing the message that was
         * passed to this function.
         * </p>
         * 
         * @param errMsg
         *            message that is send to the observers
         */
        public static void printerr(String errMsg) {
                if (theInstance == null) {
                        getInstance();
                }
                for (ConsoleObserver observer : theInstance.observers) {
                        observer.errStream(errMsg);
                }
        }

        /**
         * <p>
         * Sends an error message to all observers containing the message that was
         * passed to this function and adds an endline to the message.
         * </p>
         * 
         * @param errMsg
         *            message that is send to the observers
         */
        public static void printerrln(String errMsg) {
                if (theInstance == null) {
                        getInstance();
                }
                for (ConsoleObserver observer : theInstance.observers) {
                        observer.errStream(errMsg
                                        + StringTools.ENDLINE);
                }
        }

        /**
         * <p>
         * Sends an exception to all observers to print its stack trace.
         * </p>
         * 
         * @param e
         *            exception whose stack trace is to be printed
         */
        public static void printStacktrace(Exception e) {
                if (theInstance == null) {
                        getInstance();
                }
                for (ConsoleObserver observer : theInstance.observers) {
                        observer.printStacktrace(e);
                }
        }

        /**
         * <p>
         * Sends a debug message to all observers containing the message that was
         * passed to this function.
         * </p>
         * 
         * @param traceMsg
         *            message that is send to the observers
         */
        public static void trace(String traceMsg) {
                if (theInstance == null) {
                        getInstance();
                }
                for (ConsoleObserver observer : theInstance.observers) {
                        observer.trace(traceMsg);
                }
        }

        /**
         * <p>
         * Sends a debug message to all observers containing the message that was
         * passed to this function and adds an endline to the message.
         * </p>
         * 
         * @param traceMsg
         *            message that is send to the observers
         */
        public static void traceln(String traceMsg) {
                if (theInstance == null) {
                        getInstance();
                }
                for (ConsoleObserver observer : theInstance.observers) {
                        observer.trace(traceMsg
                                        + StringTools.ENDLINE);
                }
        }

}