Fix compilation errors, NPE, help visibility, auto-complete, click-to-copy, file path rename

Co-authored-by: Xujiayao <58985541+Xujiayao@users.noreply.github.com>

README.md

@@ -61,8 +61,8 @@ DMCC 所有运行模式都基于一个统一的通信模型，该模型包含两
 
 - **一个 Discord 账户可关联多个 Minecraft 账户**（方便玩家管理大号与小号）。
 - **一个 Minecraft 账户只能关联一个 Discord 账户**（确保游戏内身份的绝对唯一性）。
-- **数据持久化**: 绑定关系作为永久数据存储在 `Server` 端的 `account_linking/linked_accounts.json` 中，以 Discord ID 为主键。
-- **存储约束**: `linked_accounts.json` 中仅存储绑定关系最小必要字段（Discord ID、Minecraft UUID、添加时间），**不得额外存储**
+- **数据持久化**: 绑定关系作为永久数据存储在 `Server` 端的 `account_linking/links.json` 中，以 Discord ID 为主键。
+- **存储约束**: `links.json` 中仅存储绑定关系最小必要字段（Discord ID、Minecraft UUID、添加时间），**不得额外存储**
   Discord 用户名或 Minecraft 玩家名；显示名称在查询时实时解析。
 
 ### 4.2 安全绑定工作流 (严格的 MC 优先原则)
@@ -75,7 +75,7 @@ DMCC 所有运行模式都基于一个统一的通信模型，该模型包含两
     - 若该玩家存在未过期验证码，返回同一验证码并将过期时间重置为“当前时间 + 5 分钟”；
     - 若验证码已过期或不存在，生成并返回新验证码（同样 5 分钟有效）。
 4. **确认所有权**: 玩家前往 Discord，使用斜杠命令 `/link A7X9P2`。
-5. **完成绑定**: Server 验证代码有效后，将该 Discord ID 与 MC UUID 写入 `linked_accounts.json`，并使该验证码失效。
+5. **完成绑定**: Server 验证代码有效后，将该 Discord ID 与 MC UUID 写入 `links.json`，并使该验证码失效。
 
 ### 4.3 解绑与查询工作流
 
@@ -138,7 +138,7 @@ Discord 用户的身份将通过以下规则在 Server 端结算为一个具体
 
 1. **全量同步原则**: 每次同步均执行“全量重算 + 全量应用”，而非增量补丁。
 2. **强制覆盖原则**: DMCC 将重置 Minecraft 服务器当前 OP 列表，并依据 DMCC 配置中的映射规则重新分配。
-3. **绑定缺失回退**: 若某玩家解除绑定后在 `linked_accounts.json` 中不再出现，则在下一次全量同步中该玩家 OP 等级将被重置为 0。
+3. **绑定缺失回退**: 若某玩家解除绑定后在 `links.json` 中不再出现，则在下一次全量同步中该玩家 OP 等级将被重置为 0。
 4. **关闭时不干预**: 若 `sync_op_level_to_minecraft=false`，解绑不触发 OP 回收，服务器维持原样。
 5. **与原生 `/op` 的关系**: 开启后，管理员在游戏内使用原生命令 `/op` 手动授予的结果会在下一次 DMCC 全量同步时被覆盖，这是预期行为。
 

core/src/main/java/com/xujiayao/discord_mc_chat/commands/Command.java

@@ -53,6 +53,19 @@ public interface Command {
 		return false;
 	}
 
+	/**
+	 * Whether this command should appear in auto-complete suggestions for the execute command.
+	 * <p>
+	 * Commands that are only meaningful for specific sender types (e.g., link/unlink
+	 * which require player or Discord context) should return false.
+	 * This does NOT affect whether the command can be executed — only its auto-complete visibility.
+	 *
+	 * @return true if this command should appear in auto-complete, false otherwise.
+	 */
+	default boolean isAutoCompletable() {
+		return true;
+	}
+
 	/**
 	 * Whether this command should be visible in help listings for the given sender.
 	 * <p>

core/src/main/java/com/xujiayao/discord_mc_chat/commands/CommandAutoCompleter.java

@@ -68,6 +68,7 @@ public class CommandAutoCompleter {
 
 			CommandManager.getCommands().stream()
 					.filter(cmd -> cmd.name().startsWith(commandName))
+					.filter(Command::isAutoCompletable)
 					.sorted(Comparator.comparing(Command::name))
 					.forEach(cmd -> addCommandIfAuthorized(cmd, opLevel, suggestions));
 
@@ -308,6 +309,9 @@ public class CommandAutoCompleter {
 	 * @param suggestions The list to append to.
 	 */
 	private static void addCommandIfAuthorized(Command cmd, int opLevel, List<String> suggestions) {
+		if (!cmd.isAutoCompletable()) {
+			return;
+		}
 		int requiredOp = ConfigManager.getInt("command_permission_levels." + cmd.name(), 4);
 		if (opLevel >= requiredOp) {
 			StringBuilder builder = new StringBuilder();

core/src/main/java/com/xujiayao/discord_mc_chat/commands/impl/LinkCommand.java

@@ -7,6 +7,8 @@ import com.xujiayao.discord_mc_chat.network.packets.commands.link.LinkRequestPac
 import com.xujiayao.discord_mc_chat.server.linking.LinkedAccountManager;
 import com.xujiayao.discord_mc_chat.server.linking.VerificationCodeManager;
 import com.xujiayao.discord_mc_chat.utils.config.ModeManager;
+import com.xujiayao.discord_mc_chat.utils.events.CoreEvents;
+import com.xujiayao.discord_mc_chat.utils.events.EventManager;
 import com.xujiayao.discord_mc_chat.utils.i18n.I18nManager;
 
 /**
@@ -106,10 +108,15 @@ public class LinkCommand implements Command {
 		return I18nManager.getDmccTranslation("commands.link.description");
 	}
 
+	@Override
+	public boolean isAutoCompletable() {
+		return false;
+	}
+
 	@Override
 	public boolean isVisibleInHelp(CommandSender sender) {
-		// Always visible - link is available to players and Discord users
-		return true;
+		// Only show link in help for Minecraft players or Discord users
+		return (sender instanceof PlayerContextProvider) || (sender instanceof DiscordUserContextProvider);
 	}
 
 	@Override
@@ -148,11 +155,13 @@ public class LinkCommand implements Command {
 				if (LinkedAccountManager.isMinecraftUuidLinked(uuid)) {
 					String discordId = LinkedAccountManager.getDiscordIdByMinecraftUuid(uuid);
 					String discordName = LinkedAccountManager.resolveDiscordName(discordId);
-					sender.reply(I18nManager.getDmccTranslation("commands.link.already_linked", discordName));
+					// Post event so Minecraft module can display with rich formatting
+					EventManager.post(new CoreEvents.LinkCodeResponseEvent(uuid, null, true, discordName));
 					return;
 				}
 				String code = VerificationCodeManager.generateOrRefreshCode(uuid, name);
-				sender.reply(I18nManager.getDmccTranslation("commands.link.code_generated", code));
+				// Post event so Minecraft module can display with click-to-copy
+				EventManager.post(new CoreEvents.LinkCodeResponseEvent(uuid, code, false, ""));
 			}
 			case "multi_server_client" -> {
 				// Send request to standalone server via network

core/src/main/java/com/xujiayao/discord_mc_chat/commands/impl/UnlinkCommand.java

@@ -33,10 +33,15 @@ public class UnlinkCommand implements Command {
 		return I18nManager.getDmccTranslation("commands.unlink.description");
 	}
 
+	@Override
+	public boolean isAutoCompletable() {
+		return false;
+	}
+
 	@Override
 	public boolean isVisibleInHelp(CommandSender sender) {
-		// Always visible - unlink is available to players and Discord users
-		return true;
+		// Only show unlink in help for Minecraft players or Discord users
+		return (sender instanceof LinkCommand.PlayerContextProvider) || (sender instanceof LinkCommand.DiscordUserContextProvider);
 	}
 
 	@Override
@@ -57,6 +62,11 @@ public class UnlinkCommand implements Command {
 		String uuid = player.getPlayerUuid();
 		String name = player.getPlayerName();
 
+		if (uuid == null) {
+			sender.reply(I18nManager.getDmccTranslation("commands.unlink.not_available"));
+			return;
+		}
+
 		switch (ModeManager.getMode()) {
 			case "single_server" -> {
 				// Look up the linked Discord ID before unlinking so we can show it

core/src/main/java/com/xujiayao/discord_mc_chat/server/linking/LinkedAccountManager.java

@@ -22,13 +22,13 @@ import static com.xujiayao.discord_mc_chat.Constants.LOGGER;
  * <p>
  * One Discord account can link multiple Minecraft accounts (1:N).
  * One Minecraft account can only link to one Discord account (N:1 uniqueness).
- * Data is stored in {@code account_linking/linked_accounts.json} in the DMCC config directory.
+ * Data is stored in {@code account_linking/links.json} in the DMCC config directory.
  *
  * @author Xujiayao
  */
 public class LinkedAccountManager {
 
-	private static final Path LINKS_FILE = Paths.get("./config/discord_mc_chat/account_linking/linked_accounts.json");
+	private static final Path LINKS_FILE = Paths.get("./config/discord_mc_chat/account_linking/links.json");
 
 	private static final ConcurrentHashMap<String, List<LinkEntry>> LINKED_ACCOUNTS = new ConcurrentHashMap<>();
 
@@ -127,7 +127,7 @@ public class LinkedAccountManager {
 	 * Clears all linked accounts from memory without writing to disk.
 	 * <p>
 	 * This intentionally does NOT save to disk, so users can manually edit
-	 * {@code linked_accounts.json} while DMCC is running and reload to apply their changes.
+	 * {@code links.json} while DMCC is running and reload to apply their changes.
 	 * Any in-memory changes that were not yet persisted via {@link #save()} will be lost.
 	 * In practice, all mutations (link/unlink) call {@link #save()} immediately,
 	 * so no data is lost under normal operation.
@@ -195,6 +195,10 @@ public class LinkedAccountManager {
 	 * @return The Discord user ID that was unlinked from, or null if the UUID was not linked.
 	 */
 	public static synchronized String unlinkByMinecraftUuid(String minecraftUuid, String minecraftName) {
+		if (minecraftUuid == null) {
+			return null;
+		}
+
 		String discordId = UUID_TO_DISCORD.remove(minecraftUuid);
 		if (discordId == null) {
 			return null;

core/src/main/resources/lang/en_us.yml

@@ -273,6 +273,7 @@ linking:
   player_join:
     not_linked: "Your Minecraft account is not linked to Discord. Use /dmcc link to get a verification code."
     code_hint: "Use /link {} on Discord within 5 minutes to link your account."
+    click_to_copy: "Click to copy verification code"
 
 minecraft:
   translations:

core/src/main/resources/lang/zh_cn.yml

@@ -273,6 +273,7 @@ linking:
   player_join:
     not_linked: "你的 Minecraft 账户尚未绑定 Discord。使用 /dmcc link 获取验证码。"
     code_hint: "在 5 分钟内在 Discord 上使用 /link {} 来绑定你的账户。"
+    click_to_copy: "点击复制验证码"
 
 minecraft:
   translations:

minecraft/src/main/java/com/xujiayao/discord_mc_chat/minecraft/events/MinecraftEventHandler.java

@@ -23,16 +23,22 @@ import com.xujiayao.discord_mc_chat.utils.events.CoreEvents;
 import com.xujiayao.discord_mc_chat.utils.events.EventManager;
 import com.xujiayao.discord_mc_chat.utils.i18n.I18nManager;
 import net.minecraft.advancements.DisplayInfo;
+import net.minecraft.ChatFormatting;
 import net.minecraft.commands.CommandSource;
 import net.minecraft.commands.CommandSourceStack;
 import net.minecraft.core.Holder;
 import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.network.chat.ClickEvent;
 import net.minecraft.network.chat.Component;
+import net.minecraft.network.chat.HoverEvent;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.ServerTickRateManager;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.server.players.NameAndId;
+import net.minecraft.server.players.PlayerList;
+import net.minecraft.server.players.ServerOpList;
+import net.minecraft.server.players.ServerOpListEntry;
 import net.minecraft.stats.StatType;
 import net.minecraft.util.TimeUtil;
 import net.minecraft.world.level.GameRules;
@@ -162,6 +168,7 @@ public class MinecraftEventHandler {
 								I18nManager.getDmccTranslation("linking.player_join.not_linked")));
 						sp.sendSystemMessage(Component.literal(
 								I18nManager.getDmccTranslation("linking.player_join.code_hint", code)));
+						sp.sendSystemMessage(buildClickableCode(code));
 					}
 				}
 				case "multi_server_client" -> {
@@ -369,7 +376,8 @@ public class MinecraftEventHandler {
 									I18nManager.getDmccTranslation("commands.link.already_linked", event.discordName())));
 						} else if (event.code() != null) {
 							player.sendSystemMessage(Component.literal(
-									I18nManager.getDmccTranslation("linking.player_join.code_hint", event.code())));
+									I18nManager.getDmccTranslation("commands.link.code_generated", event.code())));
+							player.sendSystemMessage(buildClickableCode(event.code()));
 						}
 					}
 				} catch (Exception ignored) {
@@ -405,17 +413,16 @@ public class MinecraftEventHandler {
 
 			serverInstance.execute(() -> {
 				try {
-					net.minecraft.server.players.PlayerList playerList = serverInstance.getPlayerList();
-					net.minecraft.server.players.ServerOpList opList = playerList.getOps();
+					PlayerList playerList = serverInstance.getPlayerList();
+					ServerOpList opList = playerList.getOps();
 
 					// Step 1: De-op all currently opped players
 					// Copy the list to avoid ConcurrentModificationException
-					List<net.minecraft.server.players.ServerOpListEntry> currentOps =
-							new ArrayList<>(opList.getEntries());
-					for (net.minecraft.server.players.ServerOpListEntry op : currentOps) {
-						com.mojang.authlib.GameProfile profile = op.getUser();
-						if (profile != null) {
-							playerList.deop(profile);
+					List<ServerOpListEntry> currentOps = new ArrayList<>(opList.getEntries());
+					for (ServerOpListEntry op : currentOps) {
+						NameAndId nameAndId = op.getUser();
+						if (nameAndId != null) {
+							playerList.deop(nameAndId);
 						}
 					}
 
@@ -427,15 +434,15 @@ public class MinecraftEventHandler {
 
 						try {
 							UUID uuid = UUID.fromString(uuidStr);
-							com.mojang.authlib.GameProfile profile = serverInstance.getProfileCache()
-									.get(uuid).orElse(null);
-							if (profile == null) {
-								// Profile not in cache; skip this entry as we can't op without a valid profile
+							Optional<NameAndId> nameAndIdOpt = serverInstance.services().nameToIdCache().get(uuid);
+							if (nameAndIdOpt.isEmpty()) {
+								// Profile not in cache; skip this entry
 								continue;
 							}
+							NameAndId nameAndId = nameAndIdOpt.get();
 							// Add the OP entry with the exact desired level
-							opList.add(new net.minecraft.server.players.ServerOpListEntry(
-									profile, opLevel, opList.canBypassPlayerLimit(profile)));
+							opList.add(new ServerOpListEntry(
+									nameAndId, opLevel, opList.canBypassPlayerLimit(nameAndId)));
 						} catch (Exception ignored) {
 						}
 					}
@@ -534,6 +541,22 @@ public class MinecraftEventHandler {
 		}
 	}
 
+	/**
+	 * Builds a clickable Component for a verification code.
+	 * When clicked, the code is copied to the player's clipboard.
+	 *
+	 * @param code The verification code.
+	 * @return A clickable Component.
+	 */
+	private static Component buildClickableCode(String code) {
+		return Component.literal("[" + code + "]").withStyle(style -> style
+				.withClickEvent(new ClickEvent(ClickEvent.Action.COPY_TO_CLIPBOARD, code))
+				.withHoverEvent(new HoverEvent(HoverEvent.Action.SHOW_TEXT,
+						Component.literal(I18nManager.getDmccTranslation("linking.player_join.click_to_copy"))))
+				.withColor(ChatFormatting.GREEN)
+				.withBold(true));
+	}
+
 	/**
 	 * Builds an InfoResponsePacket containing real-time metrics of the Minecraft server.
 	 *