Add greeting command, and basic user argument

src/main/java/sciwhiz12/janitor/commands/CommandRegistry.java

@@ -8,6 +8,7 @@ import org.javacord.api.event.message.MessageCreateEvent;
 import org.javacord.api.listener.message.MessageCreateListener;
 import sciwhiz12.janitor.JanitorBot;
 import sciwhiz12.janitor.commands.bot.ShutdownCommand;
+import sciwhiz12.janitor.commands.misc.HelloCommand;
 import sciwhiz12.janitor.commands.misc.OKCommand;
 import sciwhiz12.janitor.commands.misc.PingCommand;
 import sciwhiz12.janitor.utils.Util;
@@ -34,10 +35,10 @@ public class CommandRegistry implements MessageCreateListener {
         addCommand(new PingCommand(this, "ping", "Pong!"));
         addCommand(new PingCommand(this, "pong", "Ping!"));
         addCommand(new OKCommand(this));
+        addCommand(new HelloCommand(this));
         if (bot.getConfig().getOwnerID().isPresent()) {
             addCommand(new ShutdownCommand(this, bot.getConfig().getOwnerID().get()));
         }
-
     }
 
     public CommandDispatcher<MessageCreateEvent> getDispatcher() {
@@ -56,15 +57,18 @@ public class CommandRegistry implements MessageCreateListener {
     public void onMessageCreate(MessageCreateEvent event) {
         String msg = event.getMessage().getContent();
         if (!msg.startsWith(this.prefix)) return;
+        JANITOR.debug(COMMANDS, "Received message starting with valid command prefix. Author: {}, full message: {}",
+            Util.toString(event.getMessageAuthor().asUser().orElse(null)), msg);
         try {
             StringReader command = new StringReader(msg.substring(this.prefix.length()));
             ParseResults<MessageCreateEvent> parseResults = this.dispatcher.parse(command, event);
             if (parseResults.getReader().canRead()) {
                 // Parsing did not succeed, i.e. command not found
                 // TODO: add separate code path when insufficient permissions / requires fails
+                JANITOR.error(COMMANDS, "Error while parsing command: {}", parseResults.getExceptions().values());
                 return;
             }
-            JANITOR.debug(COMMANDS, "Received command and executing. Author: {}, full message: {}", Util.toString(event.getMessageAuthor().asUser().orElse(null)), msg);
+            JANITOR.debug(COMMANDS, "Executing command.");
             dispatcher.execute(parseResults);
         } catch (CommandSyntaxException ex) {
             JANITOR.error(COMMANDS, "Error while parsing message and executing command", ex);

src/main/java/sciwhiz12/janitor/commands/arguments/UserArgument.java

@@ -0,0 +1,64 @@
+package sciwhiz12.janitor.commands.arguments;
+
+import com.google.common.collect.ImmutableList;
+import com.mojang.brigadier.LiteralMessage;
+import com.mojang.brigadier.StringReader;
+import com.mojang.brigadier.arguments.ArgumentType;
+import com.mojang.brigadier.context.CommandContext;
+import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import com.mojang.brigadier.exceptions.SimpleCommandExceptionType;
+import org.javacord.api.DiscordApi;
+import org.javacord.api.entity.user.User;
+
+import java.util.Collection;
+import java.util.concurrent.CompletableFuture;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class UserArgument implements ArgumentType<UserArgument.IUserProvider> {
+    public static final SimpleCommandExceptionType UNKNOWN_USER_IDENTIFIER = new SimpleCommandExceptionType(new LiteralMessage("Unknown user identifier"));
+    public static final Pattern USER_IDENTIFIER_PATTERN = Pattern.compile("<@!([0-9]+)>");
+
+    public static UserArgument user() {
+        return new UserArgument();
+    }
+
+    public static IUserProvider getUser(String name, CommandContext<?> ctx) {
+        return ctx.getArgument(name, IUserProvider.class);
+    }
+
+    @Override
+    public IUserProvider parse(StringReader reader) throws CommandSyntaxException {
+        if (reader.peek() == '<') { // Expecting a possible user identifier
+            int start = reader.getCursor();
+            reader.readStringUntil('>');
+            Matcher matcher = USER_IDENTIFIER_PATTERN.matcher(reader.getString().substring(start, reader.getCursor()));
+            if (matcher.matches()) {
+                return new NumericalProvider(Long.parseLong(matcher.group(1)));
+            }
+        }
+        throw UNKNOWN_USER_IDENTIFIER.create();
+    }
+
+    @Override
+    public Collection<String> getExamples() {
+        return ImmutableList.of("<@!607058472709652501>", "<@750291676764962816>");
+    }
+
+    public interface IUserProvider {
+        CompletableFuture<User> getUsers(DiscordApi api);
+    }
+
+    static class NumericalProvider implements IUserProvider {
+        private final long snowflakeID;
+
+        NumericalProvider(long snowflakeID) {
+            this.snowflakeID = snowflakeID;
+        }
+
+        @Override
+        public CompletableFuture<User> getUsers(DiscordApi api) {
+            return api.getUserById(snowflakeID);
+        }
+    }
+}

src/main/java/sciwhiz12/janitor/commands/misc/HelloCommand.java

@@ -0,0 +1,43 @@
+package sciwhiz12.janitor.commands.misc;
+
+import com.mojang.brigadier.builder.LiteralArgumentBuilder;
+import com.mojang.brigadier.context.CommandContext;
+import org.javacord.api.event.message.MessageCreateEvent;
+import sciwhiz12.janitor.commands.BaseCommand;
+import sciwhiz12.janitor.commands.CommandRegistry;
+import sciwhiz12.janitor.commands.arguments.UserArgument;
+import sciwhiz12.janitor.utils.Util;
+
+import static sciwhiz12.janitor.Logging.JANITOR;
+import static sciwhiz12.janitor.utils.CommandHelper.argument;
+import static sciwhiz12.janitor.utils.CommandHelper.literal;
+
+public class HelloCommand extends BaseCommand {
+    public HelloCommand(CommandRegistry registry) {
+        super(registry);
+    }
+
+    public LiteralArgumentBuilder<MessageCreateEvent> getNode() {
+        return literal("greet")
+            .then(
+                argument("user", UserArgument.user())
+                    .executes(this::run)
+            );
+    }
+
+    int run(final CommandContext<MessageCreateEvent> ctx) {
+        UserArgument.getUser("user", ctx).getUsers(ctx.getSource().getApi())
+            .thenCompose(user ->
+                ctx.getSource()
+                    .getMessage()
+                    .getChannel()
+                    .sendMessage("Hello " + user.getMentionTag() + " !")
+            )
+            .whenCompleteAsync(Util.handle(
+                success -> JANITOR.debug("Sent greeting message to {}", Util.toString(ctx.getSource().getMessageAuthor())),
+                err -> JANITOR.error("Error while sending greeting message to {}", Util.toString(ctx.getSource().getMessageAuthor()))
+                )
+            );
+        return 1;
+    }
+}

src/main/java/sciwhiz12/janitor/utils/CommandHelper.java

@@ -1,10 +1,16 @@
 package sciwhiz12.janitor.utils;
 
+import com.mojang.brigadier.arguments.ArgumentType;
 import com.mojang.brigadier.builder.LiteralArgumentBuilder;
+import com.mojang.brigadier.builder.RequiredArgumentBuilder;
 import org.javacord.api.event.message.MessageCreateEvent;
 
 public class CommandHelper {
     public static LiteralArgumentBuilder<MessageCreateEvent> literal(String command) {
         return LiteralArgumentBuilder.literal(command);
     }
+
+    public static <Arg> RequiredArgumentBuilder<MessageCreateEvent, Arg> argument(String command, ArgumentType<Arg> argument) {
+        return RequiredArgumentBuilder.argument(command, argument);
+    }
 }