Add commands listing command (!command)

core/src/main/java/sciwhiz12/janitor/commands/CmdListCommand.java

@@ -0,0 +1,34 @@
+package sciwhiz12.janitor.commands;
+
+import com.google.common.collect.Lists;
+import com.mojang.brigadier.builder.LiteralArgumentBuilder;
+import net.dv8tion.jda.api.events.message.MessageReceivedEvent;
+import sciwhiz12.janitor.api.command.BaseCommand;
+
+import static sciwhiz12.janitor.api.config.CoreConfigs.COMMAND_PREFIX;
+import static sciwhiz12.janitor.api.utils.CommandHelper.literal;
+
+public class CmdListCommand extends BaseCommand {
+    public CmdListCommand(CommandRegistryImpl registry) {
+        super(registry);
+    }
+
+    @Override
+    public LiteralArgumentBuilder<MessageReceivedEvent> getNode() {
+        return literal("commands")
+            .executes(ctx -> {
+                messages().<String>getListingMessage("general/commands_listing")
+                    .amountPerPage(12)
+                    .with("commands_prefix", () -> config(ctx.getSource()).forGuild(COMMAND_PREFIX))
+                    .setEntryApplier((command, subs) -> subs.with("command", () -> command))
+                    .build(ctx.getSource().getChannel(), getBot(), ctx.getSource().getMessage(),
+                        Lists.newArrayList(getRegistry().registry.keySet()));
+                return 1;
+            });
+    }
+
+    @Override
+    public CommandRegistryImpl getRegistry() {
+        return (CommandRegistryImpl) super.getRegistry();
+    }
+}

core/src/main/java/sciwhiz12/janitor/commands/CommandRegistryImpl.java

@@ -3,6 +3,7 @@ package sciwhiz12.janitor.commands;
 import com.mojang.brigadier.CommandDispatcher;
 import com.mojang.brigadier.ParseResults;
 import com.mojang.brigadier.StringReader;
+import com.mojang.brigadier.builder.LiteralArgumentBuilder;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 import net.dv8tion.jda.api.events.GenericEvent;
 import net.dv8tion.jda.api.events.message.MessageReceivedEvent;
@@ -27,7 +28,7 @@ import static sciwhiz12.janitor.api.Logging.JANITOR;
 
 public class CommandRegistryImpl implements CommandRegistry, EventListener {
     private final JanitorBotImpl bot;
-    private final Map<String, Command> registry = new HashMap<>();
+    final Map<String, Command> registry = new HashMap<>();
     private final CommandDispatcher<MessageReceivedEvent> dispatcher;
 
     public CommandRegistryImpl(JanitorBotImpl bot) {
@@ -39,6 +40,7 @@ public class CommandRegistryImpl implements CommandRegistry, EventListener {
         addCommand(OKCommand::new);
         addCommand(HelloCommand::new);
         addCommand(ShutdownCommand::new);
+        addCommand((reg) -> new CmdListCommand((CommandRegistryImpl) reg));
     }
 
     @Override
@@ -52,8 +54,15 @@ public class CommandRegistryImpl implements CommandRegistry, EventListener {
     }
 
     @Override
-    public void addCommand(Function<CommandRegistry, Command> command) {
-        dispatcher.register(command.apply(this).getNode());
+    public void addCommand(Function<CommandRegistry, Command> commandCreate) {
+        final Command command = commandCreate.apply(this);
+        final LiteralArgumentBuilder<MessageReceivedEvent> node = command.getNode();
+        final String literal = node.getLiteral();
+        if (registry.containsKey(literal)) {
+            throw new IllegalArgumentException("Command " + literal + " already exists");
+        }
+        dispatcher.register(node);
+        registry.put(literal, command);
     }
 
     @Override

core/src/main/resources/messages/general/commands_listing.json

@@ -0,0 +1,11 @@
+{
+  "type": "listing",
+  "author": {
+    "name": "List of Commands (Page ${page.current}/${page.max})"
+  },
+  "entry": {
+    "type": "description",
+    "text": "${commands_prefix}${command}"
+  },
+  "empty": "_**No commands listed.** Please report this to your bot maintainer/administrator."
+}

core/src/main/resources/messages/messages.json

@@ -1,4 +1,5 @@
 [
+  "general/commands_listing",
   "general/error/ambiguous_member",
   "general/error/guild_only_command",
   "general/error/insufficient_permissions",