From 74809121fa16b7561749de1d474ba9e2e47dbbea Mon Sep 17 00:00:00 2001
From: Danny van Heumen <danny@dannyvanheumen.nl>
Date: Sat, 16 Aug 2014 01:52:04 +0200
Subject: [PATCH] Timer now activates to clean up outdated chat room list
 cache.

---
 .../impl/protocol/irc/IrcStack.java           | 112 +++++++++++++++++-
 1 file changed, 109 insertions(+), 3 deletions(-)

diff --git a/src/net/java/sip/communicator/impl/protocol/irc/IrcStack.java b/src/net/java/sip/communicator/impl/protocol/irc/IrcStack.java
index 60308eadb..4d336afe5 100644
--- a/src/net/java/sip/communicator/impl/protocol/irc/IrcStack.java
+++ b/src/net/java/sip/communicator/impl/protocol/irc/IrcStack.java
@@ -40,6 +40,18 @@
  */
 public class IrcStack
 {
+    /**
+     * Clean-up delay. The clean up task clears any remaining chat room list
+     * cache. Since there's no pointing in timing it exactly, delay the clean up
+     * until after expiration.
+     */
+    private static final long CACHE_CLEAN_UP_DELAY = 1000L;
+
+    /**
+     * Ratio of milliseconds to nanoseconds for conversions.
+     */
+    private static final long RATIO_MILLISECONDS_TO_NANOSECONDS = 1000000L;
+
     /**
      * Expiration time for chat room list cache.
      */
@@ -519,10 +531,11 @@ public List<String> getServerChatRoomList()
                 }
                 list = listSignal.getValue();
                 this.channellist.set(list);
-                // TODO Set a timer for past channel expiration delay and clean
-                // up outdated cached channel list. Because it won't be cleaned
-                // up if a user won't list server chat rooms again.
                 LOGGER.trace("Finished retrieving server chat room list.");
+
+                // Set timer to clean up the cache after use, since otherwise it
+                // could stay in memory for a long time.
+                createCleanUpJob(this.channellist);
             }
             else
             {
@@ -532,6 +545,24 @@ public List<String> getServerChatRoomList()
         }
     }
 
+    /**
+     * Create a clean up job that checks the container after the cache has
+     * expired. If the container is still populated, then remove it. This clean
+     * up makes sure that there are no references left to an otherwise useless
+     * list of channels.
+     *
+     * @param channellist the container carrying the list of channel names
+     */
+    private static void createCleanUpJob(
+        final Container<List<String>> channellist)
+    {
+        final Timer cleanUpJob = new Timer();
+        final long timestamp = channellist.getTimestamp();
+        cleanUpJob.schedule(new ChannelListCacheCleanUpTask(channellist,
+            timestamp), CHAT_ROOM_LIST_CACHE_EXPIRATION
+            / RATIO_MILLISECONDS_TO_NANOSECONDS + CACHE_CLEAN_UP_DELAY);
+    }
+
     /**
      * Join a particular chat room.
      *
@@ -2409,5 +2440,80 @@ public void set(final T instance)
             this.instance = instance;
             this.time = System.nanoTime();
         }
+
+        /**
+         * Get the timestamp from when the instance was set.
+         *
+         * @return returns the timestamp
+         */
+        public long getTimestamp()
+        {
+            return this.time;
+        }
+    }
+
+    /**
+     * Task for cleaning up old channel list caches.
+     *
+     * @author Danny van Heumen
+     */
+    private static final class ChannelListCacheCleanUpTask
+        extends TimerTask
+    {
+        /**
+         * Expected timestamp on which the list cache was created. It is used as
+         * an indicator to see whether the cache has been refreshed in the mean
+         * time.
+         */
+        private final long timestamp;
+
+        /**
+         * Container holding the channel list cache.
+         */
+        private final Container<List<String>> container;
+
+        /**
+         * Construct new clean up job definition.
+         *
+         * @param listContainer container that holds the channel list cache
+         * @param timestamp expected timestamp of list cache creation
+         */
+        private ChannelListCacheCleanUpTask(
+            final Container<List<String>> listContainer, final long timestamp)
+        {
+            if (listContainer == null)
+            {
+                throw new IllegalArgumentException(
+                    "listContainer cannot be null");
+            }
+            this.container = listContainer;
+            this.timestamp = timestamp;
+        }
+
+        /**
+         * Remove the list reference from the container. But only if the
+         * timestamp matches. This makes sure that only one clean up job will
+         * clean up a list.
+         */
+        @Override
+        public void run()
+        {
+            synchronized (this.container)
+            {
+                // Only clean up old cache if this is the dedicated task for it.
+                // If the timestamp has changed, another job is responsible for
+                // the clean up.
+                if (this.container.getTimestamp() != this.timestamp)
+                {
+                    LOGGER.trace("Not cleaning up channel list cache. The "
+                        + "timestamp does not match.");
+                    return;
+                }
+                this.container.set(null);
+            }
+            // We cannot clear the list itself, since the contents might still
+            // be in use by the UI, inside the immutable wrapper.
+            LOGGER.debug("Old channel list cache has been cleared.");
+        }
     }
 }