Add a Discord Commands framework, and some basic commands as an example.

src/main/java/tk/sciwhiz12/concord/ChatBot.java

@@ -37,6 +37,8 @@
 import net.minecraftforge.common.MinecraftForge;
 import org.slf4j.Marker;
 import org.slf4j.MarkerFactory;
+import tk.sciwhiz12.concord.command.ConcordDiscordCommand;
+import tk.sciwhiz12.concord.command.discord.CommandDispatcher;
 import tk.sciwhiz12.concord.msg.MessageListener;
 import tk.sciwhiz12.concord.msg.Messaging;
 import tk.sciwhiz12.concord.msg.PlayerListener;
@@ -56,6 +58,7 @@ public class ChatBot extends ListenerAdapter {
     private final MessageListener msgListener;
     private final PlayerListener playerListener;
     private final StatusListener statusListener;
+    private final CommandDispatcher dispatcher;
 
     ChatBot(JDA discord, MinecraftServer server) {
         this.discord = discord;
@@ -65,6 +68,12 @@ public class ChatBot extends ListenerAdapter {
         playerListener = new PlayerListener(this);
         statusListener = new StatusListener(this);
 
+        // Initialize Discord-side commands
+        dispatcher = new CommandDispatcher();
+        discord.addEventListener(dispatcher);
+
+        ConcordDiscordCommand.initialize(dispatcher);
+
         // Prevent any mentions not explicitly specified
         MessageAction.setDefaultMentions(Collections.emptySet());
     }
@@ -77,6 +86,8 @@ public MinecraftServer getServer() {
         return server;
     }
 
+    public CommandDispatcher getDispatcher() { return dispatcher; }
+
     @Override
     public void onReady(ReadyEvent event) {
         discord.getPresence().setPresence(OnlineStatus.ONLINE, Activity.playing("some Minecraft"));

src/main/java/tk/sciwhiz12/concord/Concord.java

@@ -45,6 +45,7 @@
 import tk.sciwhiz12.concord.command.ConcordCommand;
 import tk.sciwhiz12.concord.command.EmoteCommandHook;
 import tk.sciwhiz12.concord.command.ReportCommand;
+import tk.sciwhiz12.concord.command.ConcordDiscordCommand;
 import tk.sciwhiz12.concord.command.SayCommandHook;
 import tk.sciwhiz12.concord.msg.Messaging;
 import tk.sciwhiz12.concord.util.Messages;
@@ -76,7 +77,7 @@ public Concord() {
         MinecraftForge.EVENT_BUS.addListener(EmoteCommandHook::onRegisterCommands);
     }
 
-    
+
     public void onServerStarting(ServerStartingEvent event) {
         if (!event.getServer().isDedicatedServer() && !ConcordConfig.ENABLE_INTEGRATED.get()) {
             LOGGER.info("Discord integration for integrated servers is disabled in server config.");
@@ -146,6 +147,7 @@ public static void enable(MinecraftServer server) {
         try {
             final JDA jda = jdaBuilder.build();
             BOT = new ChatBot(jda, server);
+            ConcordDiscordCommand.postInit();
         } catch (LoginException e) {
             LOGGER.error("Error while trying to login to Discord; integration will not be enabled.", e);
         }

src/main/java/tk/sciwhiz12/concord/ConcordConfig.java

@@ -39,6 +39,7 @@ public class ConcordConfig {
 
     public static final ForgeConfigSpec.ConfigValue<String> TOKEN;
     public static final ForgeConfigSpec.ConfigValue<String> GUILD_ID;
+    public static final ForgeConfigSpec.ConfigValue<String> MODERATOR_ROLE_ID;
     public static final ForgeConfigSpec.ConfigValue<String> CHAT_CHANNEL_ID;
     public static final ForgeConfigSpec.ConfigValue<String> REPORT_CHANNEL_ID;
 
@@ -110,6 +111,10 @@ public static void register() {
             REPORT_CHANNEL_ID = builder.comment("The snowflake ID of the channel where this bot will post reports from in-game users.",
                             "If empty, reports will be disabled.")
                     .define("report_channel_id", "");
+            MODERATOR_ROLE_ID = builder.comment("The snowflake ID of the role that will be treated as a moderator role.",
+                            "This role will be able to use Concord's Moderation slash commands on Discord - /kick, /ban, etc.",
+                            "This should not be treated as an alternative to proper Discord permissions configuration, but exists as a safeguard so that random users may not ban you while you're setting up.")
+                    .define("moderator_role_id", "");
 
             builder.pop();
         }

src/main/java/tk/sciwhiz12/concord/command/ConcordDiscordCommand.java

@@ -0,0 +1,118 @@
+package tk.sciwhiz12.concord.command;
+
+import net.dv8tion.jda.api.EmbedBuilder;
+import net.dv8tion.jda.api.JDA;
+import net.dv8tion.jda.api.events.interaction.SlashCommandEvent;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.Mth;
+import net.minecraftforge.api.distmarker.Dist;
+import net.minecraftforge.fml.loading.FMLLoader;
+import tk.sciwhiz12.concord.Concord;
+import tk.sciwhiz12.concord.command.discord.BanCommand;
+import tk.sciwhiz12.concord.command.discord.CommandDispatcher;
+import tk.sciwhiz12.concord.command.discord.KickCommand;
+import tk.sciwhiz12.concord.command.discord.WhitelistCommand;
+
+import java.awt.*;
+import java.time.Instant;
+
+/**
+ * The Discord command hub.
+ *
+ * Has several sub-commands, some of which are usable by everyone:
+ *  - list; lists players on the connected server.
+ *  - tps; displays ticks per second in a format similar to /forge tps.
+ *  - help; displays help autogenerated from the registered commands.
+ * Some commands are only usable by administrators:
+ *  - kick <user> [reason]; remove a user from the server, optionally with the specified reason. See @link{KickCommand}.
+ *  - ban <user> [reason]; ban a user from the server, optionally with the specified reason. See @link{BanCommand}
+ *  - whitelist <remove|add> <user>; add or remove a user from the server's whitelist. See @link{WhitelistCommand}
+ *      The above commands are implemented separately, due to requirements of the option system.
+ *  - stop; stop and shutdown the connected server. Disabled on singleplayer worlds.
+ *
+ * @author Curle
+ */
+public class ConcordDiscordCommand {
+    private static JDA bot;
+    private static MinecraftServer server;
+
+    private static void tpsCommand(SlashCommandEvent tpsEvent) {
+        double meanTickTime = Mth.average(server.tickTimes) * 1.0E-6D;
+        double meanTPS = Math.min(1000.0/meanTickTime, 20);
+
+        StringBuilder builder = new StringBuilder();
+
+        for (ServerLevel dim : server.getAllLevels()) {
+            long[] times = server.getTickTime(dim.dimension());
+
+            if (times == null)
+                times = new long[]{0};
+
+            double worldTickTime = Mth.average(times) * 1.0E-6D;
+            double worldTPS = Math.min(1000.0 / worldTickTime, 20);
+
+            builder.append(dim.dimension().location()).append(": Mean tick time: ").append(worldTickTime).append(" ms. Mean TPS: ").append(worldTPS).append("\n");
+        }
+
+        tpsEvent.replyEmbeds(new EmbedBuilder()
+                .setTitle("Concord integrations")
+                .setDescription("TPS Performance Report")
+                .addField("Overall performance", "Mean tick time: " + meanTickTime + " ms. Mean TPS: " + meanTPS, false)
+                .addField("Performance per dimension", builder.toString(), false)
+                .setColor(Color.ORANGE)
+                .setTimestamp(Instant.now())
+                .build()
+        ).setEphemeral(true).queue();
+    }
+
+    private static void helpCommand(SlashCommandEvent helpEvent) {
+        var dispatcher = Concord.BOT.getDispatcher();
+        var commands = dispatcher.getCommands();
+
+        var builder = new EmbedBuilder().setTitle("Concord Commands")
+                .setDescription("There are " + commands.size() + " registered commands.");
+
+        for (var command : commands) {
+            builder.addField(command.getName(), command.getHelpString(), true);
+        }
+
+        helpEvent.replyEmbeds(builder.setTimestamp(Instant.now()).setColor(Color.GREEN).build()).setEphemeral(false).queue();
+    }
+
+    public static void initialize(CommandDispatcher dispatcher) {
+        dispatcher.registerSingle("list", "List all online users.", "Show a count of online users, and their names.", (listEvent) -> {
+            listEvent.replyEmbeds(new EmbedBuilder()
+                    .setTitle("Concord Integrations")
+                    .setDescription("There are currently " + server.getPlayerCount() + " people online.")
+                    .addField("Online Players", String.join("\n", server.getPlayerNames()), false)
+                    .setTimestamp(Instant.now())
+                    .setColor(Color.CYAN)
+                    .build()
+            ).setEphemeral(true).queue();
+        });
+
+        dispatcher.registerSingle("tps", "Show the performance of the server.", "Display a breakdown of server performance, in current, average and separated by dimension.", ConcordDiscordCommand::tpsCommand);
+        dispatcher.registerSingle("help", "Show detailed information about every single available command.", "Show the help information you are currently reading.", ConcordDiscordCommand::helpCommand);
+        dispatcher.registerSingle("stop", "Shut down your Minecraft server.", "Immediately schedule the shutdown of the Minecraft server, akin to /stop from in-game.", (event) -> {
+            // Short-circuit if on integrated server
+            if(FMLLoader.getDist() == Dist.CLIENT) {
+                event.reply("Sorry! This command is disabled on Integrated servers.").setEphemeral(true).queue();
+                return;
+            }
+
+            event.reply("Shutting the server down..").queue();
+            Concord.BOT.getServer().halt(false);
+        });
+
+
+        dispatcher.registerSingle(KickCommand.INSTANCE);
+        dispatcher.registerSingle(BanCommand.INSTANCE);
+        dispatcher.registerSingle(WhitelistCommand.INSTANCE);
+    }
+
+    public static void postInit() {
+        bot = Concord.BOT.getDiscord();
+        server = Concord.BOT.getServer();
+    }
+}

src/main/java/tk/sciwhiz12/concord/command/discord/BanCommand.java

@@ -0,0 +1,108 @@
+package tk.sciwhiz12.concord.command.discord;
+
+import net.dv8tion.jda.api.events.interaction.SlashCommandEvent;
+import net.dv8tion.jda.api.interactions.commands.OptionType;
+import net.dv8tion.jda.api.interactions.commands.build.OptionData;
+import net.dv8tion.jda.api.requests.restaction.CommandCreateAction;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.players.UserBanListEntry;
+import net.minecraftforge.api.distmarker.Dist;
+import net.minecraftforge.fml.loading.FMLLoader;
+import tk.sciwhiz12.concord.Concord;
+import tk.sciwhiz12.concord.ConcordConfig;
+
+import java.util.Date;
+import java.util.List;
+
+
+/**
+ * This command takes the form:
+ *  /ban <user> [reason]
+ *
+ * It removes a user from the server and prevents them from joining again (known as a ban, or kickban),
+ *  optionally with the specified reason.
+ *
+ * @author Curle
+ */
+public class BanCommand extends SlashCommand {
+    private static final OptionData USER_OPTION = new OptionData(OptionType.STRING, "user", "The name of the user to ban from the server", true);
+    private static final OptionData REASON_OPTION = new OptionData(OptionType.STRING, "reason", "The reason for the user to be banned.", false);
+
+    public static BanCommand INSTANCE = new BanCommand();
+
+    public BanCommand() {
+        setName("ban");
+        setDescription("Ban a player from your Minecraft server");
+        setHelpString("Remove a player from the server, and prevent them from joining again, optionally with a reason. The reason is for moderation purposes, and is not shown to the user.");
+    }
+
+    @Override
+    public void execute(SlashCommandEvent event) {
+        var roleConfig = ConcordConfig.MODERATOR_ROLE_ID.get();
+        if (!roleConfig.isEmpty()) {
+            var role = Concord.BOT.getDiscord().getRoleById(roleConfig);
+            // If no role, then it's non-empty and invalid; disable the command
+            if (role == null) {
+                event.reply("Sorry, but this command is disabled by configuration. Check the moderator_role_id option in the config.").setEphemeral(true).queue();
+                return;
+            } else {
+                // If the member doesn't have the moderator role, then deny them the ability to use the command.
+                if (!event.getMember().getRoles().contains(role)) {
+                    event.reply("Sorry, but you don't have permission to use this command.").setEphemeral(true).queue();
+                    return;
+                }
+                // Fall-through; member has the role, so they can use the command.
+            }
+            // Fall-through; the role is empty, so all permissions are handled by Discord.
+        }
+
+        var user = event.getOption(USER_OPTION.getName()).getAsString();
+        var server = Concord.BOT.getServer();
+
+
+        // Short-circuit for integrated servers.
+        if (!ConcordConfig.ENABLE_INTEGRATED.get() && FMLLoader.getDist() == Dist.CLIENT) {
+            event.reply("Sorry, but this command is disabled on Integrated Servers. Check the enable_integrated option in the Concord Config.").setEphemeral(true).queue();
+            return;
+        }
+
+        var reasonMapping = event.getOption(REASON_OPTION.getName());
+
+        // The Reason Option is optional, so default to "Reason Not Specified" if it isn't.
+        var reason = "";
+        if (reasonMapping == null)
+            reason = "Reason Not Specified";
+        else
+            reason = reasonMapping.getAsString();
+
+
+        if (List.of(server.getPlayerNames()).contains(user)) {
+            var player = server.getPlayerList().getPlayerByName(user);
+            var profile = player.getGameProfile();
+
+            // If they're not already banned..
+            if (!server.getPlayerList().getBans().isBanned(profile)) {
+                // Prevent them from rejoining
+                UserBanListEntry userbanlistentry = new UserBanListEntry(profile, (Date) null, "Discord User " + event.getMember().getEffectiveName(), (Date) null, reason);
+                server.getPlayerList().getBans().add(userbanlistentry);
+                // Kick them
+                player.connection.disconnect(
+                        reasonMapping == null ?
+                                Component.translatable("multiplayer.disconnect.banned") :
+                                Component.literal(reasonMapping.getAsString())
+                );
+
+                event.reply("User " + user + " banned successfully.").queue();
+                return;
+            }
+            event.reply("The user " + user + " is already banned on this server.").setEphemeral(true).queue();
+            return;
+        }
+        event.reply("The user " + user + " is not connected to the server.").setEphemeral(true).queue();
+    }
+
+    @Override
+    public CommandCreateAction setup(CommandCreateAction action) {
+        return action.addOptions(USER_OPTION, REASON_OPTION);
+    }
+}