Fixed search results getting added to queue on wrong thread.

src/main/java/dev/logal/logalbot/Main.java

@@ -31,7 +31,7 @@ import net.dv8tion.jda.core.AccountType;
 import net.dv8tion.jda.core.JDA;
 import net.dv8tion.jda.core.JDABuilder;
 
-public final class Main {
+public final class Main implements Runnable {
 	private static final Logger logger = LoggerFactory.getLogger(Main.class);
 
 	private static final String token = System.getenv("TOKEN");
@@ -42,6 +42,11 @@ public final class Main {
 	}
 
 	public static final void main(final String[] arguments) {
+		MainThread.scheduleImmediately(new Main());
+	}
+
+	@Override
+	public final void run() {
 		logger.info("Beginning setup of LogalBot...");
 
 		logger.info("Verifying connection to Redis...");
@@ -89,6 +94,11 @@ public final class Main {
 		CommandManager.registerCommand("help", new Help(), false);
 
 		// Fun Commands
+		CommandManager.registerCommand("dice", new Dice(), false);
+		CommandManager.registerCommandAlias("die", "dice");
+		CommandManager.registerCommandAlias("random", "dice");
+		CommandManager.registerCommandAlias("rng", "dice");
+		CommandManager.registerCommandAlias("roll", "dice");
 		CommandManager.registerCommand("8ball", new EightBall(), false);
 
 		// Audio Commands

src/main/java/dev/logal/logalbot/MainThread.java

@@ -0,0 +1,61 @@
+package dev.logal.logalbot;
+
+// Copyright 2019 Logan Fick
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+
+import net.dv8tion.jda.core.utils.Checks;
+
+public final class MainThread {
+    private static final ScheduledExecutorService mainThread = Executors
+            .newSingleThreadScheduledExecutor(new MainThreadFactory());
+
+    public static final void scheduleImmediately(final Runnable task) {
+        Checks.notNull(task, "Task");
+
+        mainThread.schedule(task, 0, TimeUnit.MICROSECONDS);
+    }
+
+    public static final ScheduledFuture<?> scheduleLater(final Runnable task, final long delay, final TimeUnit unit) {
+        Checks.notNull(task, "Task");
+        Checks.notNegative(delay, "Delay");
+        Checks.notNull(unit, "Unit");
+
+        return mainThread.schedule(task, delay, unit);
+    }
+
+    public static final ScheduledFuture<?> scheduleRepeatedlyAtFixedRate(final Runnable task, final long initialDelay,
+            final long period, final TimeUnit unit) {
+        Checks.notNull(task, "Task");
+        Checks.notNegative(initialDelay, "Initial Delay");
+        Checks.notNegative(period, "Period");
+        Checks.notNull(unit, "Unit");
+
+        return mainThread.scheduleAtFixedRate(task, initialDelay, period, unit);
+    }
+
+    public static final ScheduledFuture<?> scheduleRepeatedlyWithFixedDelay(final Runnable task,
+            final long initialDelay, final long period, final TimeUnit unit) {
+        Checks.notNull(task, "Task");
+        Checks.notNegative(initialDelay, "Initial Delay");
+        Checks.notNegative(period, "Period");
+        Checks.notNull(unit, "Unit");
+
+        return mainThread.scheduleWithFixedDelay(task, initialDelay, period, unit);
+    }
+}

src/main/java/dev/logal/logalbot/MainThreadFactory.java

@@ -0,0 +1,30 @@
+package dev.logal.logalbot;
+
+// Copyright 2019 Logan Fick
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import java.util.concurrent.ThreadFactory;
+
+import net.dv8tion.jda.core.utils.Checks;
+
+public final class MainThreadFactory implements ThreadFactory {
+    @Override
+    public final Thread newThread(final Runnable runnable) {
+        Checks.notNull(runnable, "Runnable");
+
+        final Thread newThread = new Thread(runnable);
+        newThread.setName("Main Thread");
+        return newThread;
+    }
+}

src/main/java/dev/logal/logalbot/audio/TrackLoadHandler.java

@@ -26,7 +26,9 @@ import com.sedmelluq.discord.lavaplayer.track.AudioTrackInfo;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import dev.logal.logalbot.MainThread;
 import dev.logal.logalbot.commands.CommandResponse;
+import dev.logal.logalbot.tasks.TrackAdditionTask;
 import dev.logal.logalbot.utils.AudioUtil;
 import dev.logal.logalbot.utils.PermissionManager;
 import dev.logal.logalbot.utils.TrackUtil;
@@ -54,7 +56,8 @@ public final class TrackLoadHandler implements AudioLoadResultHandler {
         Checks.notNull(track, "Track");
 
         final CommandResponse response;
-        final TrackScheduler scheduler = AudioUtil.getTrackScheduler(this.channel.getGuild());
+        final Guild guild = this.channel.getGuild();
+        final TrackScheduler scheduler = AudioUtil.getTrackScheduler(guild);
 
         final AudioTrackInfo info = track.getInfo();
         if (info.isStream) {
@@ -83,7 +86,7 @@ public final class TrackLoadHandler implements AudioLoadResultHandler {
         }
 
         final RequestedTrack requestedTrack = new RequestedTrack(track, requester);
-        scheduler.addToQueue(requestedTrack);
+        MainThread.scheduleImmediately(new TrackAdditionTask(guild, requestedTrack));
         response = new CommandResponse("notes",
                 this.requester.getAsMention() + " added the following track to the queue:");
         response.attachEmbed(TrackUtil.trackInfoEmbed(requestedTrack));
@@ -95,7 +98,8 @@ public final class TrackLoadHandler implements AudioLoadResultHandler {
         Checks.notNull(playlist, "Playlist");
 
         CommandResponse response;
-        final TrackScheduler scheduler = AudioUtil.getTrackScheduler(this.channel.getGuild());
+        final Guild guild = this.channel.getGuild();
+        final TrackScheduler scheduler = AudioUtil.getTrackScheduler(guild);
 
         final AudioTrack selectedTrack = playlist.getSelectedTrack();
         final AudioTrack track;
@@ -127,7 +131,7 @@ public final class TrackLoadHandler implements AudioLoadResultHandler {
 
             if ((info.length >= 60000 && info.length <= 900000) || PermissionManager.isWhitelisted(this.requester)) {
                 final RequestedTrack requestedTrack = new RequestedTrack(track, requester);
-                scheduler.addToQueue(requestedTrack);
+                MainThread.scheduleImmediately(new TrackAdditionTask(guild, requestedTrack));
                 response = new CommandResponse("notes",
                         this.requester.getAsMention() + " added the following track to the queue:");
                 response.attachEmbed(TrackUtil.trackInfoEmbed(requestedTrack));
@@ -141,20 +145,19 @@ public final class TrackLoadHandler implements AudioLoadResultHandler {
             }
         } else {
             if (PermissionManager.isWhitelisted(this.requester)) {
-                final LinkedList<RequestedTrack> addedTracks = new LinkedList<>();
+                final LinkedList<RequestedTrack> tracksToAdd = new LinkedList<>();
+                int count = 0;
                 for (final AudioTrack playlistTrack : playlist.getTracks()) {
-                    if (!scheduler.isQueueFull()) {
+                    if (count++ != 250) {
                         if (!scheduler.isQueued(playlistTrack) && !playlistTrack.getInfo().isStream) {
-                            final RequestedTrack requestedTrack = new RequestedTrack(track, requester);
-                            scheduler.addToQueue(requestedTrack);
-                            addedTracks.add(requestedTrack);
+                            tracksToAdd.add(new RequestedTrack(playlistTrack, requester));
                         }
                     } else {
                         break;
                     }
                 }
 
-                if (addedTracks.size() == 0) {
+                if (tracksToAdd.size() == 0) {
                     response = new CommandResponse("x",
                             "Sorry " + this.requester.getAsMention()
                                     + ", but none of the tracks in that playlist could be added to the queue.")
@@ -162,9 +165,10 @@ public final class TrackLoadHandler implements AudioLoadResultHandler {
                     response.sendResponse(this.channel);
                 }
 
+                MainThread.scheduleImmediately(new TrackAdditionTask(guild, tracksToAdd));
                 response = new CommandResponse("notes",
                         this.requester.getAsMention() + " added the following tracks from a playlist to the queue:");
-                response.attachEmbed(TrackUtil.trackListInfoEmbed(addedTracks, false));
+                response.attachEmbed(TrackUtil.trackListInfoEmbed(tracksToAdd, false));
                 response.sendResponse(this.channel);
             } else {
                 response = new CommandResponse("x",

src/main/java/dev/logal/logalbot/audio/TrackScheduler.java

@@ -27,11 +27,13 @@ import com.sedmelluq.discord.lavaplayer.track.AudioTrackEndReason;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import dev.logal.logalbot.tasks.IdleDisconnectTask;
+import dev.logal.logalbot.MainThread;
+import dev.logal.logalbot.tasks.CloseAudioConnectionTask;
+import dev.logal.logalbot.tasks.OpenAudioConnectionTask;
+import dev.logal.logalbot.tasks.PlayNextTrackTask;
 import dev.logal.logalbot.utils.AudioUtil;
 import dev.logal.logalbot.utils.DataManager;
 import dev.logal.logalbot.utils.PermissionManager;
-import dev.logal.logalbot.utils.Scheduler;
 import dev.logal.logalbot.utils.SkipTracker;
 import dev.logal.logalbot.utils.VoiceChannelUtil;
 import net.dv8tion.jda.core.entities.Guild;
@@ -46,7 +48,7 @@ public final class TrackScheduler extends AudioEventAdapter {
     private final Guild guild;
     private final LinkedList<RequestedTrack> queue = new LinkedList<>();
     private boolean queueLocked = false;
-    private ScheduledFuture<?> idleLogoutTask;
+    private ScheduledFuture<?> closeAudioConnectionTask;
 
     public TrackScheduler(final Guild guild) {
         Checks.notNull(guild, "Guild");
@@ -71,16 +73,21 @@ public final class TrackScheduler extends AudioEventAdapter {
         logger.info(user.getName() + " (" + user.getId() + ") added '" + track.getInfo().title + "' to the queue in "
                 + this.guild.getName() + " (" + this.guild.getId() + ").");
 
-        if (!AudioUtil.isTrackLoaded(this.guild)) {
-            AudioUtil.openAudioConnection(VoiceChannelUtil.getVoiceChannelMemberIsConnectedTo(requester));
-            AudioUtil.playTrack(this.guild, requestedTrack);
-        } else {
-            this.queue.add(requestedTrack);
+        final VoiceChannel targetChannel = VoiceChannelUtil.getVoiceChannelMemberIsConnectedTo(requester);
+        if (!AudioUtil.isAudioConnectionOpen(this.guild)
+                || targetChannel != AudioUtil.getVoiceChannelConnectedTo(this.guild)) {
+            MainThread.scheduleImmediately(
+                    new OpenAudioConnectionTask(VoiceChannelUtil.getVoiceChannelMemberIsConnectedTo(requester)));
         }
+
+        if (!AudioUtil.isTrackLoaded(this.guild) && this.queue.size() == 0) {
+            MainThread.scheduleImmediately(new PlayNextTrackTask(this.guild));
+        }
+        this.queue.add(requestedTrack);
     }
 
     public final void removeFromQueue(final int index) {
-        Checks.notNull(index, "Index");
+        Checks.notNegative(index, "Index");
 
         logger.info("Track '" + queue.remove(index).getTrack().getInfo().title + "' has been removed from the queue in "
                 + this.guild.getName() + " (" + this.guild.getId() + ").");
@@ -110,8 +117,6 @@ public final class TrackScheduler extends AudioEventAdapter {
     }
 
     public final void setQueueLocked(final boolean locked) {
-        Checks.notNull(locked, "Locked");
-
         this.queueLocked = locked;
     }
 
@@ -123,7 +128,13 @@ public final class TrackScheduler extends AudioEventAdapter {
         Collections.shuffle(this.queue);
     }
 
+    public final RequestedTrack popFromQueue() {
+        return this.queue.remove(0);
+    }
+
     public final int occupiedSlotCount(Member member) {
+        Checks.notNull(member, "Member");
+
         int count = 0;
         for (RequestedTrack requestedTrack : this.queue) {
             if (requestedTrack.getRequester().equals(member)) {
@@ -152,10 +163,10 @@ public final class TrackScheduler extends AudioEventAdapter {
 
         logger.info("Track '" + track.getInfo().title + "' in " + this.guild.getName() + " (" + this.guild.getId()
                 + ") has started.");
-        if (this.idleLogoutTask != null && !this.idleLogoutTask.isDone()) {
+        if (this.closeAudioConnectionTask != null && !this.closeAudioConnectionTask.isDone()) {
             logger.info("A track has started in " + this.guild.getName() + " (" + this.guild.getId()
                     + "). Cancelling scheduled disconnect.");
-            this.idleLogoutTask.cancel(true);
+            this.closeAudioConnectionTask.cancel(true);
         }
         SkipTracker.resetVotes(this.guild);
     }
@@ -170,7 +181,7 @@ public final class TrackScheduler extends AudioEventAdapter {
         logger.info("Track '" + track.getInfo().title + "' in " + this.guild.getName() + " (" + this.guild.getId()
                 + ") has stopped.");
         if ((endReason.mayStartNext || endReason == AudioTrackEndReason.STOPPED) && this.queue.size() >= 1) {
-            AudioUtil.playTrack(this.guild, this.queue.remove(0));
+            MainThread.scheduleImmediately(new PlayNextTrackTask(this.guild));
         } else {
             try {
                 AudioUtil.setVolume(this.guild, Integer.parseInt(DataManager.getGuildValue(guild, "defaultVolume")));
@@ -182,7 +193,8 @@ public final class TrackScheduler extends AudioEventAdapter {
             final VoiceChannel currentChannel = AudioUtil.getVoiceChannelConnectedTo(this.guild);
             logger.info("Disconnecting from " + currentChannel.getName() + " (" + currentChannel.getId() + ") in "
                     + this.guild.getName() + " (" + this.guild.getId() + ") in 1 minute...");
-            this.idleLogoutTask = Scheduler.schedule(new IdleDisconnectTask(this.guild), 1, TimeUnit.MINUTES);
+            this.closeAudioConnectionTask = MainThread.scheduleLater(new CloseAudioConnectionTask(this.guild), 1,
+                    TimeUnit.MINUTES);
         }
         SkipTracker.resetVotes(this.guild);
     }

src/main/java/dev/logal/logalbot/commands/CommandResponse.java

@@ -21,10 +21,10 @@ import java.util.concurrent.TimeUnit;
 import com.vdurmont.emoji.Emoji;
 import com.vdurmont.emoji.EmojiManager;
 
+import dev.logal.logalbot.MainThread;
 import dev.logal.logalbot.tasks.MessageDeleteTask;
 import dev.logal.logalbot.tasks.ReactionCallbackExpireTask;
 import dev.logal.logalbot.utils.ReactionCallbackManager;
-import dev.logal.logalbot.utils.Scheduler;
 import net.dv8tion.jda.core.MessageBuilder;
 import net.dv8tion.jda.core.entities.Member;
 import net.dv8tion.jda.core.entities.Message;
@@ -44,10 +44,11 @@ public final class CommandResponse {
     private TimeUnit deletionDelayUnit, expireDelayUnit;
 
     public CommandResponse(final String emoji, final String response) {
-        Checks.notNull(emoji, "Emoji");
-        Checks.notNull(response, "Response");
+        Checks.notEmpty(emoji, "Emoji");
+        Checks.notEmpty(response, "Response");
 
         this.emoji = EmojiManager.getForAlias(emoji);
+        Checks.notNull(this.emoji, "Valid Emoji");
         this.response = response;
     }
 
@@ -59,7 +60,7 @@ public final class CommandResponse {
     }
 
     public final CommandResponse setDeletionDelay(final long delay, final TimeUnit unit) {
-        Checks.notNull(delay, "Delay");
+        Checks.notNegative(delay, "Delay");
         Checks.notNull(unit, "Unit");
 
         this.deletionDelay = delay;
@@ -68,7 +69,7 @@ public final class CommandResponse {
     }
 
     public final CommandResponse addReactionCallback(final String emoji, final ReactionCallback callback) {
-        Checks.notNull(emoji, "Emoji");
+        Checks.notEmpty(emoji, "Emoji");
         Checks.notNull(callback, "Callback");
 
         this.callbacks.put(EmojiManager.getForAlias(emoji), callback);
@@ -83,7 +84,7 @@ public final class CommandResponse {
     }
 
     public final CommandResponse setReactionCallbackExpireDelay(final long delay, final TimeUnit unit) {
-        Checks.notNull(delay, "Delay");
+        Checks.notNegative(delay, "Delay");
         Checks.notNull(unit, "Unit");
 
         this.expireDelay = delay;
@@ -106,9 +107,9 @@ public final class CommandResponse {
 
     private final void handleResponseCreation(final Message message) {
         if ((this.deletionDelay != 0) && (this.deletionDelayUnit != null)) {
-            Scheduler.schedule(new MessageDeleteTask(message), this.deletionDelay, this.deletionDelayUnit);
+            MainThread.scheduleLater(new MessageDeleteTask(message), this.deletionDelay, this.deletionDelayUnit);
         } else if ((this.expireDelay != 0) && (this.expireDelayUnit != null)) {
-            Scheduler.schedule(new ReactionCallbackExpireTask(message), this.expireDelay, this.expireDelayUnit);
+            MainThread.scheduleLater(new ReactionCallbackExpireTask(message), this.expireDelay, this.expireDelayUnit);
         }
 
         for (final Map.Entry<Emoji, ReactionCallback> callback : callbacks.entrySet()) {

src/main/java/dev/logal/logalbot/commands/audio/Queue.java

@@ -17,11 +17,12 @@ package dev.logal.logalbot.commands.audio;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 
+import dev.logal.logalbot.MainThread;
 import dev.logal.logalbot.audio.RequestedTrack;
 import dev.logal.logalbot.commands.Command;
 import dev.logal.logalbot.commands.CommandResponse;
+import dev.logal.logalbot.tasks.CommandExecutionTask;
 import dev.logal.logalbot.utils.AudioUtil;
-import dev.logal.logalbot.utils.CommandManager;
 import dev.logal.logalbot.utils.ReactionCallbackManager;
 import dev.logal.logalbot.utils.TrackUtil;
 import net.dv8tion.jda.core.entities.Guild;
@@ -56,14 +57,16 @@ public final class Queue implements Command {
         if (page != 1) {
             response.addReactionCallback("arrow_left", (reactor, message) -> {
                 ReactionCallbackManager.unregisterMessage(message, true);
-                CommandManager.executeCommand(("queue " + (page - 1)).split(" "), reactor, channel);
+                MainThread.scheduleImmediately(
+                        new CommandExecutionTask(("queue " + (page - 1)).split(" "), reactor, channel));
             });
         }
 
         if (TrackUtil.doesGreaterPageExist(queue, page)) {
             response.addReactionCallback("arrow_right", (reactor, message) -> {
                 ReactionCallbackManager.unregisterMessage(message, true);
-                CommandManager.executeCommand(("queue " + (page + 1)).split(" "), reactor, channel);
+                MainThread.scheduleImmediately(
+                        new CommandExecutionTask(("queue " + (page + 1)).split(" "), reactor, channel));
             });
         }
 

src/main/java/dev/logal/logalbot/commands/audio/Remove.java

@@ -16,12 +16,13 @@ package dev.logal.logalbot.commands.audio;
 
 import java.util.concurrent.TimeUnit;
 
+import dev.logal.logalbot.MainThread;
 import dev.logal.logalbot.audio.RequestedTrack;
 import dev.logal.logalbot.audio.TrackScheduler;
 import dev.logal.logalbot.commands.Command;
 import dev.logal.logalbot.commands.CommandResponse;
+import dev.logal.logalbot.tasks.CommandExecutionTask;
 import dev.logal.logalbot.utils.AudioUtil;
-import dev.logal.logalbot.utils.CommandManager;
 import dev.logal.logalbot.utils.ReactionCallbackManager;
 import dev.logal.logalbot.utils.StringUtil;
 import dev.logal.logalbot.utils.TrackUtil;
@@ -69,7 +70,8 @@ public final class Remove implements Command {
                 response.addReactionCallback(StringUtil.intToKeycapEmoji(trackNumber).getAliases().get(0),
                         (reactor, message) -> {
                             ReactionCallbackManager.unregisterMessage(message, true);
-                            CommandManager.executeCommand(("remove " + trackNumber).split(" "), reactor, channel);
+                            MainThread.scheduleImmediately(
+                                    new CommandExecutionTask(("remove " + trackNumber).split(" "), reactor, channel));
                         });
             }
 

src/main/java/dev/logal/logalbot/commands/audio/Shuffle.java

@@ -44,6 +44,6 @@ public final class Shuffle implements Command {
         }
 
         scheduler.shuffleQueue();
-        return new CommandResponse("salad", executor.getAsMention() + " shuffled the queue.");
+        return new CommandResponse("green_salad", executor.getAsMention() + " shuffled the queue.");
     }
 }

src/main/java/dev/logal/logalbot/commands/fun/Dice.java

@@ -0,0 +1,53 @@
+package dev.logal.logalbot.commands.fun;
+
+// Copyright 2019 Logan Fick
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import java.security.SecureRandom;
+import java.util.concurrent.TimeUnit;
+
+import dev.logal.logalbot.commands.Command;
+import dev.logal.logalbot.commands.CommandResponse;
+import net.dv8tion.jda.core.entities.Member;
+import net.dv8tion.jda.core.entities.TextChannel;
+
+public final class Dice implements Command {
+    private final SecureRandom rng = new SecureRandom();
+
+    @Override
+    public CommandResponse execute(String[] arguments, Member executor, TextChannel channel) {
+        if (arguments.length == 0) {
+            return new CommandResponse("game_die",
+                    executor.getAsMention() + ", the dice rolled **" + (rng.nextInt(6) + 1) + "**.");
+        } else {
+            final int maximumRange;
+            try {
+                maximumRange = Integer.parseInt(arguments[0]);
+            } catch (final NumberFormatException exception) {
+                return new CommandResponse("x",
+                        "Sorry " + executor.getAsMention() + ", but the maximum range must be an integer.")
+                                .setDeletionDelay(30, TimeUnit.SECONDS);
+            }
+
+            if (maximumRange < 1) {
+                return new CommandResponse("x",
+                        "Sorry " + executor.getAsMention() + ", but the maximum range must be at least 1.")
+                                .setDeletionDelay(30, TimeUnit.SECONDS);
+            }
+
+            return new CommandResponse("game_die",
+                    executor.getAsMention() + ", the dice rolled **" + (rng.nextInt(maximumRange) + 1) + "**.");
+        }
+    }
+}

src/main/java/dev/logal/logalbot/events/GuildMessageReactionAdd.java

@@ -14,7 +14,8 @@ package dev.logal.logalbot.events;
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-import dev.logal.logalbot.utils.ReactionCallbackManager;
+import dev.logal.logalbot.MainThread;
+import dev.logal.logalbot.tasks.ReactionCallbackExecutionTask;
 import net.dv8tion.jda.core.events.message.guild.react.GuildMessageReactionAddEvent;
 import net.dv8tion.jda.core.hooks.ListenerAdapter;
 import net.dv8tion.jda.core.utils.Checks;
@@ -25,8 +26,8 @@ public final class GuildMessageReactionAdd extends ListenerAdapter {
         Checks.notNull(event, "Event");
 
         if (!event.getUser().equals(event.getJDA().getSelfUser())) {
-            ReactionCallbackManager.executeCallback(event.getMessageIdLong(), event.getChannel(), event.getMember(),
-                    event.getReactionEmote().getName());
+            MainThread.scheduleImmediately(new ReactionCallbackExecutionTask(event.getMessageIdLong(),
+                    event.getChannel(), event.getMember(), event.getReactionEmote().getName()));
         }
     }
 }

src/main/java/dev/logal/logalbot/events/GuildMessageReceived.java

@@ -17,7 +17,8 @@ package dev.logal.logalbot.events;
 import java.util.Arrays;
 import java.util.List;
 
-import dev.logal.logalbot.utils.CommandManager;
+import dev.logal.logalbot.MainThread;
+import dev.logal.logalbot.tasks.CommandExecutionTask;
 import dev.logal.logalbot.utils.DataManager;
 import net.dv8tion.jda.core.Permission;
 import net.dv8tion.jda.core.entities.Guild;
@@ -55,7 +56,7 @@ public final class GuildMessageReceived extends ListenerAdapter {
                 if (self.hasPermission(channel, Permission.MESSAGE_MANAGE)) {
                     message.delete().reason("LogalBot Command Execution").queue();
                 }
-                CommandManager.executeCommand(command, author, channel);
+                MainThread.scheduleImmediately(new CommandExecutionTask(command, author, channel));
             }
         } else {
             final String commandCharacter = DataManager.getGuildValue(guild, "commandCharacter");
@@ -70,7 +71,7 @@ public final class GuildMessageReceived extends ListenerAdapter {
                 if (self.hasPermission(channel, Permission.MESSAGE_MANAGE)) {
                     message.delete().reason("LogalBot Command Execution").queue();
                 }
-                CommandManager.executeCommand(command, author, channel);
+                MainThread.scheduleImmediately(new CommandExecutionTask(command, author, channel));
             }
         }
     }

src/main/java/dev/logal/logalbot/events/GuildVoiceLeave.java

@@ -19,6 +19,8 @@ import java.util.List;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import dev.logal.logalbot.MainThread;
+import dev.logal.logalbot.tasks.ResetAudioPlayerTask;
 import dev.logal.logalbot.utils.AudioUtil;
 import net.dv8tion.jda.core.entities.Guild;
 import net.dv8tion.jda.core.entities.Member;
@@ -55,10 +57,7 @@ public final class GuildVoiceLeave extends ListenerAdapter {
             if (members.size() == 1 && members.get(0).getUser().equals(event.getJDA().getSelfUser())) {
                 logger.info("All listeners left " + leftChannel.getName() + " (" + leftChannel.getId() + ") in "
                         + guild.getName() + " (" + guild.getId() + ").");
-                AudioUtil.getTrackScheduler(guild).clearQueue();
-                if (AudioUtil.isTrackLoaded(guild)) {
-                    AudioUtil.stopTrack(guild);
-                }
+                MainThread.scheduleImmediately(new ResetAudioPlayerTask(guild));
             }
         }
     }

src/main/java/dev/logal/logalbot/events/GuildVoiceMove.java

@@ -19,6 +19,8 @@ import java.util.List;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import dev.logal.logalbot.MainThread;
+import dev.logal.logalbot.tasks.ResetAudioPlayerTask;
 import dev.logal.logalbot.utils.AudioUtil;
 import net.dv8tion.jda.core.entities.Guild;
 import net.dv8tion.jda.core.entities.Member;
@@ -55,10 +57,7 @@ public final class GuildVoiceMove extends ListenerAdapter {
             if (members.size() == 1 && members.get(0).getUser().equals(event.getJDA().getSelfUser())) {
                 logger.info("All listeners left " + leftChannel.getName() + " (" + leftChannel.getId() + ") in "
                         + guild.getName() + " (" + guild.getId() + ").");
-                AudioUtil.getTrackScheduler(guild).clearQueue();
-                if (AudioUtil.isTrackLoaded(guild)) {
-                    AudioUtil.stopTrack(guild);
-                }
+                MainThread.scheduleImmediately(new ResetAudioPlayerTask(guild));
             }
         }
     }

src/main/java/dev/logal/logalbot/tasks/CloseAudioConnectionTask.java

@@ -18,10 +18,10 @@ import dev.logal.logalbot.utils.AudioUtil;
 import net.dv8tion.jda.core.entities.Guild;
 import net.dv8tion.jda.core.utils.Checks;
 
-public final class IdleDisconnectTask implements Runnable {
+public final class CloseAudioConnectionTask implements Runnable {
     private final Guild guild;
 
-    public IdleDisconnectTask(final Guild guild) {
+    public CloseAudioConnectionTask(final Guild guild) {
         Checks.notNull(guild, "Guild");
 
         this.guild = guild;

src/main/java/dev/logal/logalbot/tasks/CommandExecutionTask.java

@@ -0,0 +1,41 @@
+package dev.logal.logalbot.tasks;
+
+// Copyright 2019 Logan Fick
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License. 
+
+import dev.logal.logalbot.utils.CommandManager;
+import net.dv8tion.jda.core.entities.Member;
+import net.dv8tion.jda.core.entities.TextChannel;
+import net.dv8tion.jda.core.utils.Checks;
+
+public final class CommandExecutionTask implements Runnable {
+    private final String[] command;
+    private final Member executor;
+    private final TextChannel channel;
+
+    public CommandExecutionTask(final String[] command, final Member executor, final TextChannel channel) {
+        Checks.noneNull(command, "Command");
+        Checks.notNull(executor, "Executor");
+        Checks.notNull(channel, "Channel");
+
+        this.command = command;
+        this.executor = executor;
+        this.channel = channel;
+    }
+
+    @Override
+    public final void run() {
+        CommandManager.executeCommand(this.command, this.executor, this.channel);
+    }
+}

src/main/java/dev/logal/logalbot/tasks/MessageDeleteTask.java

@@ -30,6 +30,5 @@ public final class MessageDeleteTask implements Runnable {
     @Override
     public final void run() {
         ReactionCallbackManager.unregisterMessage(messageToDelete, true);
-        messageToDelete.delete().queue();
     }
 }

src/main/java/dev/logal/logalbot/tasks/OpenAudioConnectionTask.java

@@ -0,0 +1,34 @@
+package dev.logal.logalbot.tasks;
+
+// Copyright 2019 Logan Fick
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import dev.logal.logalbot.utils.AudioUtil;
+import net.dv8tion.jda.core.entities.VoiceChannel;
+import net.dv8tion.jda.core.utils.Checks;
+
+public final class OpenAudioConnectionTask implements Runnable {
+    private final VoiceChannel channel;
+
+    public OpenAudioConnectionTask(final VoiceChannel channel) {
+        Checks.notNull(channel, "Channel");
+
+        this.channel = channel;
+    }
+
+    @Override
+    public void run() {
+        AudioUtil.openAudioConnection(channel);
+    }
+}

src/main/java/dev/logal/logalbot/tasks/PlayNextTrackTask.java

@@ -0,0 +1,34 @@
+package dev.logal.logalbot.tasks;
+
+// Copyright 2019 Logan Fick
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import dev.logal.logalbot.utils.AudioUtil;
+import net.dv8tion.jda.core.entities.Guild;
+import net.dv8tion.jda.core.utils.Checks;
+
+public final class PlayNextTrackTask implements Runnable {
+    private final Guild guild;
+
+    public PlayNextTrackTask(final Guild guild) {
+        Checks.notNull(guild, "Guild");
+
+        this.guild = guild;
+    }
+
+    @Override
+    public void run() {
+        AudioUtil.playNextTrack(this.guild);
+    }
+}

src/main/java/dev/logal/logalbot/tasks/ReactionCallbackExecutionTask.java

@@ -0,0 +1,45 @@
+package dev.logal.logalbot.tasks;
+
+// Copyright 2019 Logan Fick
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import dev.logal.logalbot.utils.ReactionCallbackManager;
+import net.dv8tion.jda.core.entities.Member;
+import net.dv8tion.jda.core.entities.TextChannel;
+import net.dv8tion.jda.core.utils.Checks;
+
+public final class ReactionCallbackExecutionTask implements Runnable {
+    private final long messageID;
+    private final TextChannel channel;
+    private final Member executor;
+    private final String emoji;
+
+    public ReactionCallbackExecutionTask(final long messageID, final TextChannel channel, final Member executor,
+            final String emoji) {
+        Checks.notNegative(messageID, "Message ID");
+        Checks.notNull(channel, "Channel");
+        Checks.notNull(executor, "Executor");
+        Checks.notEmpty(emoji, "Emoji");
+
+        this.messageID = messageID;
+        this.channel = channel;
+        this.executor = executor;
+        this.emoji = emoji;
+    }
+
+    @Override
+    public void run() {
+        ReactionCallbackManager.executeCallback(this.messageID, this.channel, this.executor, this.emoji);
+    }
+}

src/main/java/dev/logal/logalbot/tasks/ResetAudioPlayerTask.java

@@ -0,0 +1,35 @@
+package dev.logal.logalbot.tasks;
+
+// Copyright 2019 Logan Fick
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import dev.logal.logalbot.utils.AudioUtil;
+import net.dv8tion.jda.core.entities.Guild;
+import net.dv8tion.jda.core.utils.Checks;
+
+public final class ResetAudioPlayerTask implements Runnable {
+    private final Guild guild;
+
+    public ResetAudioPlayerTask(final Guild guild) {
+        Checks.notNull(guild, "Guild");
+
+        this.guild = guild;
+    }
+
+    @Override
+    public void run() {
+        AudioUtil.getTrackScheduler(guild).clearQueue();
+        AudioUtil.stopTrack(guild);
+    }
+}

src/main/java/dev/logal/logalbot/tasks/TrackAdditionTask.java

@@ -0,0 +1,54 @@
+package dev.logal.logalbot.tasks;
+
+// Copyright 2019 Logan Fick
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+// https://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import java.util.LinkedList;
+import java.util.List;
+
+import dev.logal.logalbot.audio.RequestedTrack;
+import dev.logal.logalbot.audio.TrackScheduler;
+import dev.logal.logalbot.utils.AudioUtil;
+import net.dv8tion.jda.core.entities.Guild;
+import net.dv8tion.jda.core.utils.Checks;
+
+public final class TrackAdditionTask implements Runnable {
+    private final Guild guild;
+    private final LinkedList<RequestedTrack> tracks;
+
+    public TrackAdditionTask(final Guild guild, final RequestedTrack track) {
+        Checks.notNull(guild, "Guild");
+        Checks.notNull(track, "Track");
+
+        this.guild = guild;
+        tracks = new LinkedList<RequestedTrack>();
+        tracks.add(track);
+    }
+
+    public TrackAdditionTask(final Guild guild, final List<RequestedTrack> tracks) {
+        Checks.notNull(guild, "Guild");
+        Checks.noneNull(tracks, "Tracks");
+
+        this.guild = guild;
+        this.tracks = (LinkedList<RequestedTrack>) tracks;
+    }
+
+    @Override
+    public final void run() {
+        final TrackScheduler scheduler = AudioUtil.getTrackScheduler(this.guild);
+        for (final RequestedTrack track : this.tracks) {
+            scheduler.addToQueue(track);
+        }
+    }
+}

src/main/java/dev/logal/logalbot/utils/AudioUtil.java

@@ -106,11 +106,20 @@ public final class AudioUtil {
         loadedTracks.put(guild.getIdLong(), track);
     }
 
+    public static final void playNextTrack(final Guild guild) {
+        Checks.notNull(guild, "Guild");
+
+        final RequestedTrack track = schedulers.get(guild.getIdLong()).popFromQueue();
+        if (track != null) {
+            playTrack(guild, track);
+        }
+    }
+
     public static final void stopTrack(final Guild guild) {
         Checks.notNull(guild, "Guild");
 
-        players.get(guild.getIdLong()).stopTrack();
         loadedTracks.remove(guild.getIdLong());
+        players.get(guild.getIdLong()).stopTrack();
     }
 
     public static final boolean isTrackLoaded(final Guild guild) {
@@ -132,7 +141,6 @@ public final class AudioUtil {
 
     public static final void setPausedState(final Guild guild, final boolean pausedState) {
         Checks.notNull(guild, "Guild");
-        Checks.notNull(pausedState, "Paused state");
 
         guild.getAudioManager().setSelfMuted(pausedState);
         players.get(guild.getIdLong()).setPaused(pausedState);
@@ -166,7 +174,7 @@ public final class AudioUtil {
     }
 
     public static final void findTrack(final String query, final Member requester, final TextChannel channel) {
-        Checks.notNull(query, "Query");
+        Checks.notEmpty(query, "Query");
         Checks.notNull(requester, "Requester");
         Checks.notNull(channel, "Channel");
 

src/main/java/dev/logal/logalbot/utils/ReactionCallbackManager.java

@@ -49,8 +49,8 @@ public final class ReactionCallbackManager {
     }
 
     public static final void setCallbackTarget(final Message message, final User user) {
-        Checks.notNull(user, "User");
         Checks.notNull(message, "Messsage");
+        Checks.notNull(user, "User");
 
         targetDictionary.put(message.getIdLong(), user.getIdLong());
     }
@@ -58,19 +58,22 @@ public final class ReactionCallbackManager {
     public static final void unregisterMessage(final Message message, final boolean delete) {
         Checks.notNull(message, "Message");
 
-        callbackDictionary.remove(message.getIdLong());
-        targetDictionary.remove(message.getIdLong());
-
         if (delete) {
             message.delete().queue();
         } else {
-            message.addReaction(EmojiManager.getForAlias("no_entry").getUnicode()).queue();
+            if (callbackDictionary.containsKey(message.getIdLong())) {
+                message.addReaction(EmojiManager.getForAlias("no_entry").getUnicode()).queue();
+            }
         }
+
+        callbackDictionary.remove(message.getIdLong());
+        targetDictionary.remove(message.getIdLong());
     }
 
     public static final void executeCallback(final long messageID, final TextChannel channel, final Member reactor,
             final String emoji) {
-        Checks.notNull(messageID, "Message ID");
+        Checks.notNegative(messageID, "Message ID");
+        Checks.notNull(channel, "Channel");
         Checks.notNull(reactor, "Reactor");
         Checks.notEmpty(emoji, "Emoji");
 

src/main/java/dev/logal/logalbot/utils/Scheduler.java

@@ -1,48 +0,0 @@
-package dev.logal.logalbot.utils;
-
-// Copyright 2019 Logan Fick
-
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-
-// https://www.apache.org/licenses/LICENSE-2.0
-
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.ScheduledFuture;
-import java.util.concurrent.TimeUnit;
-
-import net.dv8tion.jda.core.utils.Checks;
-
-public final class Scheduler {
-    private static final ScheduledExecutorService pool = Executors.newScheduledThreadPool(1);
-
-    private Scheduler() {
-        // Static access only.
-    }
-
-    public static final ScheduledFuture<?> schedule(final Runnable runnable, final long delay, final TimeUnit unit) {
-        Checks.notNull(runnable, "Runnable");
-        Checks.notNull(delay, "Delay");
-        Checks.notNull(unit, "Unit");
-
-        return pool.schedule(runnable, delay, unit);
-    }
-
-    public static final ScheduledFuture<?> scheduleRepeating(final Runnable runnable, final long initialDelay,
-            final long period, final TimeUnit unit) {
-        Checks.notNull(runnable, "Runnable");
-        Checks.notNull(initialDelay, "Initial delay");
-        Checks.notNull(period, "Period");
-        Checks.notNull(unit, "Unit");
-
-        return pool.scheduleAtFixedRate(runnable, initialDelay, period, unit);
-    }
-}

src/main/java/dev/logal/logalbot/utils/StringUtil.java

@@ -81,7 +81,7 @@ public final class StringUtil {
     }
 
     public static final String formatTime(final long milliseconds) {
-        Checks.notNull(milliseconds, "Milliseconds");
+        Checks.notNegative(milliseconds, "Milliseconds");
 
         final long second = (milliseconds / 1000) % 60;
         final long minute = (milliseconds / (1000 * 60)) % 60;

src/main/java/dev/logal/logalbot/utils/TrackUtil.java

@@ -65,7 +65,6 @@ public final class TrackUtil {
 
     public static final MessageEmbed trackListInfoEmbed(final List<RequestedTrack> tracks, final boolean numbered) {
         Checks.notNull(tracks, "Tracks");
-        Checks.notNull(numbered, "Numbered");
 
         final EmbedBuilder builder = new EmbedBuilder();
         for (int i = 0; i < tracks.size(); i++) {
@@ -94,7 +93,6 @@ public final class TrackUtil {
 
     public static final MessageEmbed pagedTrackListInfoEmbed(final List<RequestedTrack> tracks, int page) {
         Checks.notNull(tracks, "Tracks");
-        Checks.notNull(page, "Page");
 
         final EmbedBuilder builder = new EmbedBuilder();
         if (page < 1) {
@@ -124,7 +122,6 @@ public final class TrackUtil {
 
     public static final boolean doesGreaterPageExist(final List<RequestedTrack> tracks, int page) {
         Checks.notNull(tracks, "Tracks");
-        Checks.notNull(page, "Page");
 
         final int pages = (int) Math.ceil(tracks.size() / 10d);
         return (page < pages);