User: use a stably-ordered queue for long-polling

If the AJAX request for LongPollServlet happens with enough of a delay,
there may be two stateful messages in the queue -- I have observed two
GAME_STATE_CHANGE messages enqueued simultaneously when the Card Czar
does not long-poll while the other players progress the game through
PLAYING to JUDGING.  The JS code overwrites the state as it iterates the
list, so the "last state wins".  But PriorityQueue<E> explicitly does
not guarantee any particular ordering among elements that compare
"equal", causing the client to think the game is PLAYING.

src/main/java/net/socialgamer/cah/data/ConnectedUsers.java

@@ -269,8 +269,7 @@ public class ConnectedUsers {
    * @param broadcastTo
    *          List of users to broadcast the message to.
    * @param type
-   *          Type of message to broadcast. This determines the order the messages are returned by
+   *          Type of message to broadcast.
-   *          priority.
    * @param masterData
    *          Message data to broadcast.
    */

src/main/java/net/socialgamer/cah/data/Game.java

@@ -463,8 +463,7 @@ public class Game {
    * Broadcast a message to all players in this game.
    *
    * @param type
-   *          Type of message to broadcast. This determines the order the messages are returned by
+   *          Type of message to broadcast.
-   *          priority.
    * @param masterData
    *          Message data to broadcast.
    */

src/main/java/net/socialgamer/cah/data/QueuedMessage.java

@@ -33,7 +33,7 @@ import net.socialgamer.cah.Constants.ReturnableData;
  * 
  * @author Andy Janata (ajanata@socialgamer.net)
  */
-public class QueuedMessage implements Comparable<QueuedMessage> {
+public class QueuedMessage {
 
   private final MessageType messageType;
   private final Map<ReturnableData, Object> data;
@@ -42,8 +42,7 @@ public class QueuedMessage implements Comparable<QueuedMessage> {
    * Create a new queued message.
    * 
    * @param messageType
-   *          Type of message to be queued. The type influences the priority in returning messages
+   *          Type of message to be queued.
-   *          to the client.
    * @param data
    *          The data of the message to be queued.
    */
@@ -66,15 +65,6 @@ public class QueuedMessage implements Comparable<QueuedMessage> {
     return data;
   }
 
-  /**
-   * This is not guaranteed to be consistent with .equals() since we do not care about the data for
-   * ordering.
-   */
-  @Override
-  public int compareTo(final QueuedMessage qm) {
-    return this.messageType.getWeight() - qm.messageType.getWeight();
-  }
-
   @Override
   public String toString() {
     return messageType.toString() + "_" + data.toString();
@@ -92,9 +82,5 @@ public class QueuedMessage implements Comparable<QueuedMessage> {
     MessageType(final int weight) {
       this.weight = weight;
     }
-
-    public int getWeight() {
-      return weight;
-    }
   }
 }

src/main/java/net/socialgamer/cah/data/User.java

@@ -26,7 +26,8 @@ package net.socialgamer.cah.data;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Date;
-import java.util.concurrent.PriorityBlockingQueue;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
 
 import javax.annotation.Nullable;
 
@@ -54,7 +55,7 @@ public class User {
 
   private final String idCode;
 
-  private final PriorityBlockingQueue<QueuedMessage> queuedMessages;
+  private final BlockingQueue<QueuedMessage> queuedMessages;
 
   private final Object queuedMessageSynchronization = new Object();
 
@@ -121,7 +122,7 @@ public class User {
     this.sessionId = sessionId;
     this.clientLanguage = clientLanguage == null ? "" : clientLanguage;
     agent = UADetectorServiceFactory.getResourceModuleParser().parse(clientAgent);
-    queuedMessages = new PriorityBlockingQueue<QueuedMessage>();
+    queuedMessages = new LinkedBlockingQueue<QueuedMessage>();
   }
 
   public interface Factory {