command: Respond to direct messages

src/main/java/org/togetherjava/discordbot/commands/CommandListener.java

@@ -11,23 +11,27 @@
 import net.dv8tion.jda.api.events.message.MessageReceivedEvent;
 import net.dv8tion.jda.api.hooks.ListenerAdapter;
 import org.togetherjava.discordbot.commands.CommandContext.JdaRequestContext;
+import org.togetherjava.discordbot.util.Messages;
 
 /**
  * A command listener for JDA. It is responsible for listening to messages an invoking commands.
  */
 @Singleton
 public class CommandListener extends ListenerAdapter {
 
-  private JdaExecutor executor;
+  private final JdaExecutor executor;
+  private final Messages messages;
 
   /**
    * Creates a new command listener.
    *
    * @param executor the jda executor
+   * @param messages the messages container
    */
   @Inject
-  public CommandListener(JdaExecutor executor) {
+  public CommandListener(JdaExecutor executor, Messages messages) {
     this.executor = executor;
+    this.messages = messages;
   }
 
   @Override
@@ -44,6 +48,9 @@ public void onMessageReceived(@Nonnull MessageReceivedEvent event) {
       );
       executor.execute(content, context);
     } catch (CommandNotFoundException | NoSeparatorException ignored) {
+      if (event.getMessage().getMentionedUsers().contains(event.getJDA().getSelfUser())) {
+        event.getChannel().sendMessage(messages.tr("commands.on-mention.response")).queue();
+      }
     } catch (ParseException | AbnormalCommandResultException | CommandException e) {
       if (e.getCause() != null && e.getCause().getMessage() != null) {
         event.getChannel()

src/main/resources/messages.yml

@@ -14,4 +14,6 @@ commands:
     usage: "ban <id|mention> <duration in days> [reason]"
   free:
     short-description: "Shows the time since the last message in help channels."
-    usage: "free"
+    usage: "free"
+  on-mention:
+    response: "I'm available! Please use '>help' to get a list of commands."