package com.onaro.sanscreen.client;

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.util.Stack;

import javax.swing.Icon;

import com.onaro.client.ClientUIUtils;
import com.onaro.client.ProblemState;

/**
 * This class receives messages from external processes and save them in a stack-type-of container
 * to be published to subscriber of this class later on.  
 * <p>
 * The policy of how these messages are advertised is as follow:
 * <ol>
 * <li>Using {@link #setMessage(String)} a new message is added into a stack-like container
 * {@link IndexedRemovalStack}.
 *  <li>The top most message saved in the stack is the one being advertised.
 *  <li> If a message is cleared up from the stack (not necessary from the top) the top most message
 *  is displayed.
 *  <li> The process that add a new message is responsible to clean it by calling {@link #cleanMessage(com.onaro.sanscreen.client.MessageManager.Message)}
 * </ol>
 * 
 * 
 * We use this class in {@link SanscreenStatusBar} which is a subscriber to display messages in the 
 * status area, please see {@link SanscreenStatusBar#createMessageStatusJPanel} 
 * 
 * @since 5/6/2008
 * @author john.cohen
 * 
 */
public final class MessageManager {
	public static final String PROP_CURRENT_MESSAGE = "currentMessage"; //$NON-NLS-1$
	private Stack<Message> stack;
	private PropertyChangeSupport subscribers;

	
	public MessageManager(){
		stack = new Stack<Message>();
		subscribers = new PropertyChangeSupport(this);
	}
	
    public synchronized void addPropertyChangeListener(PropertyChangeListener listener) {
    	subscribers.addPropertyChangeListener(listener);
    }

    public synchronized void removePropertyChangeListener(PropertyChangeListener listener) {
    	subscribers.removePropertyChangeListener(listener);
    }
    
    public Message addErrorMessage(final String message) {
    	return addMessage(message, ProblemState.ERROR);
    }
    
    public Message addWarnMessage(final String message) {
    	return addMessage(message, ProblemState.WARNING);
    }
    
    public Message addInfoMessage(final String message) {
    	return addMessage(message, ProblemState.INFO);
    }

    public Message getLastMessage() {
        if (!stack.isEmpty()) {
            return stack.peek();
        }
        return null;
    }
    
    /**
     * Adds a message to be advertised.
     * 
     * @param message message to be advertised.
     * @return Message class that is being used to later on cleared up the message from the stack.
     */
	private Message addMessage(final String message, final ProblemState category) {
		Message oldMessage = null; 
		if (!stack.isEmpty())
			oldMessage = stack.peek();
		
		final Message newMessage = new Message(message, category);
		stack.push(newMessage);
		synchronized(subscribers){
			subscribers.firePropertyChange(PROP_CURRENT_MESSAGE, oldMessage, newMessage);
		}
		return newMessage;
	}

	/**
     * Removes a message from the stack.  It uses the object returned by {@link #setMessage(String)}
     * 
     * @param Message message to be deleted.
     */	
	private void cleanMessage(final Message oldMessage){
		stack.remove(oldMessage);

		Message newMessage = null; 
		if (!stack.isEmpty())
			newMessage = stack.peek();

		synchronized(subscribers){
			subscribers.firePropertyChange(PROP_CURRENT_MESSAGE, oldMessage, newMessage);
		}
	}

	

	/**
	 * Immutable thread safe class.  It represents a message to be displayed.<br>
	 * Instances of this class are managed by {@link MessageManager}
	 */
	public class Message {
		private final String message;
		private final Icon icon;

		public Message(final String message, final ProblemState category) {
			this.message = message;
			this.icon = ClientUIUtils.getProblemStateIcon(category);
		}

		public String getMessage() {
			return message;
		}

		public Icon getIcon(){
			return icon;
		}

		public void clean(){
			cleanMessage(this);
		}		
	}
}