/*
* This file is part of the Echo Web Application Framework (hereinafter "Echo").
* Copyright (C) 2002-2009 NextApp, Inc.
*
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (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.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*/
package echo2example.chatserver;
/**
* A store for posted <code>Message</code>s.
*/
public class MessageStore {
private static final int MAX_MESSAGES = 1000;
private static final int RECENT_MESSAGES = 15;
private long[] messageIds = new long[MAX_MESSAGES];
private Message[] messages = new Message[MAX_MESSAGES];
private int firstMessageIndex = 0;
private int messageCount = 0;
/**
* Creates a new <code>MessageStore</code>.
*/
public MessageStore() {
super();
}
/**
* Returns the message at the specified index.
*
* @param index the index
* @return the message
*/
private Message getMessage(int index) {
return messages[(firstMessageIndex + index) % MAX_MESSAGES];
}
/**
* Retrieves all messages with ids greater than the specified id.
*
* @param lastRetrievedId the id of the last message retrieved
* @return an array containing messages posted after the message identified
*/
public Message[] getMessages(long lastRetrievedId) {
int startIndex = 0;
while (startIndex < messageCount) {
Message message = getMessage(startIndex);
if (message.getId() > lastRetrievedId) {
break;
}
++startIndex;
}
Message[] matchingMessages = new Message[messageCount - startIndex];
for (int i = startIndex; i < messageCount; ++i) {
matchingMessages[i - startIndex] = getMessage(i);
}
return matchingMessages;
}
/**
* Returns an array of recently posted messages.
* This method is queried by clients that have just joined the chat room
* to retrieve context on the chat.
*
* @return the recently posted messages
*/
public Message[] getRecentMessages() {
Message[] matchingMessages = new Message[messageCount < RECENT_MESSAGES ? messageCount : RECENT_MESSAGES];
for (int i = 0; i < matchingMessages.length; ++i) {
matchingMessages[i] = getMessage(messageCount - matchingMessages.length + i);
}
return matchingMessages;
}
/**
* Posts a message.
*
* @param userName the name of the user
* @param messageContent the message content to post
*/
public synchronized void post(String userName, String messageContent) {
int messageIndex = (firstMessageIndex + messageCount) % MAX_MESSAGES;
Message message = new Message(userName, messageContent);
messages[messageIndex] = message;
messageIds[messageIndex] = message.getId();
if (messageCount < MAX_MESSAGES) {
++messageCount;
} else {
firstMessageIndex = (firstMessageIndex + 1) % MAX_MESSAGES;
}
}
}