Add Guild#retrieveMetaData (#1171)

* Lazy load member limits for guilds
* Improve implementation of update handler
* Add Guild#retrieveMetaData

src/main/java/net/dv8tion/jda/api/entities/Guild.java

@@ -519,6 +519,8 @@ default int getMaxEmotes()
      * @return The maximum amount of members
      *
      * @since  4.0.0
+     *
+     * @see    #retrieveMetaData()
      */
     int getMaxMembers();
 
@@ -530,9 +532,22 @@ default int getMaxEmotes()
      * @return The maximum amount of connected members this guild can have
      *
      * @since  4.0.0
+     *
+     * @see    #retrieveMetaData()
      */
     int getMaxPresences();
 
+    /**
+     * Loads {@link MetaData} for this guild instance.
+     *
+     * @return {@link RestAction} - Type: {@link MetaData}
+     *
+     * @since  4.2.0
+     */
+    @Nonnull
+    @CheckReturnValue
+    RestAction<MetaData> retrieveMetaData();
+
     /**
      * Provides the {@link net.dv8tion.jda.api.entities.VoiceChannel VoiceChannel} that has been set as the channel
      * which {@link net.dv8tion.jda.api.entities.Member Members} will be moved to after they have been inactive in a
@@ -4607,4 +4622,67 @@ public String toString()
             return "GuildBan:" + user + (reason == null ? "" : '(' + reason + ')');
         }
     }
+
+    /**
+     * Meta-Data for a Guild
+     *
+     * @since 4.2.0
+     */
+    class MetaData
+    {
+        private final int memberLimit;
+        private final int presenceLimit;
+        private final int approximatePresences;
+        private final int approximateMembers;
+
+        public MetaData(int memberLimit, int presenceLimit, int approximatePresences, int approximateMembers)
+        {
+            this.memberLimit = memberLimit;
+            this.presenceLimit = presenceLimit;
+            this.approximatePresences = approximatePresences;
+            this.approximateMembers = approximateMembers;
+        }
+
+        /**
+         * The active member limit for this guild.
+         * <br>This limit restricts how many users can be member for this guild at once.
+         *
+         * @return The member limit
+         */
+        public int getMemberLimit()
+        {
+            return memberLimit;
+        }
+
+        /**
+         * The active presence limit for this guild.
+         * <br>This limit restricts how many users can be connected/online for this guild at once.
+         *
+         * @return The presence limit
+         */
+        public int getPresenceLimit()
+        {
+            return presenceLimit;
+        }
+
+        /**
+         * The approximate number of online members in this guild.
+         *
+         * @return The approximate presence count
+         */
+        public int getApproximatePresences()
+        {
+            return approximatePresences;
+        }
+
+        /**
+         * The approximate number of members in this guild.
+         *
+         * @return The approximate member count
+         */
+        public int getApproximateMembers()
+        {
+            return approximateMembers;
+        }
+    }
 }

src/main/java/net/dv8tion/jda/internal/entities/GuildImpl.java

@@ -289,6 +289,24 @@ public int getMaxPresences()
         return maxPresences;
     }
 
+    @Nonnull
+    @Override
+    public RestAction<MetaData> retrieveMetaData()
+    {
+        Route.CompiledRoute route = Route.Guilds.GET_GUILD.compile(getId());
+        route = route.withQueryParams("with_counts", "true");
+        return new RestActionImpl<>(getJDA(), route, (response, request) -> {
+            DataObject json = response.getObject();
+            int memberLimit = json.getInt("max_members", 0);
+            int presenceLimit = json.getInt("max_presences", 5000);
+            this.maxMembers = memberLimit;
+            this.maxPresences = presenceLimit;
+            int approxMembers = json.getInt("approximate_member_count", this.memberCount);
+            int approxPresence = json.getInt("approximate_presence_count", 0);
+            return new MetaData(memberLimit, presenceLimit, approxPresence, approxMembers);
+        });
+    }
+
     @Override
     public VoiceChannel getAfkChannel()
     {

src/main/java/net/dv8tion/jda/internal/handle/GuildUpdateHandler.java

@@ -55,13 +55,17 @@ protected Long handleInternally(DataObject content)
             return null;
         }
 
-        //////////////
-        //  WARNING //
-        //Do not rely on allContent past this point, this method is also called from GuildCreateHandler!
-        //////////////
-        long ownerId = content.getLong("owner_id");
+        //When member limits aren't initialized we don't fire an update event for them
         int maxMembers = content.getInt("max_members", 0);
         int maxPresences = content.getInt("max_presences", 5000);
+        if (guild.getMaxMembers() == 0)
+        {
+            // Initialize member limits to avoid unwanted update events
+            guild.setMaxPresences(maxPresences);
+            guild.setMaxMembers(maxMembers);
+        }
+
+        long ownerId = content.getLong("owner_id");
         int boostCount = content.getInt("premium_subscription_count", 0);
         int boostTier = content.getInt("premium_tier", 0);
         String description = content.getString("description", null);