feat: Add UUID integration for bans, whitelist and ops

src/main/java/com/legacyminecraft/poseidon/PoseidonConfig.java

@@ -57,6 +57,7 @@ private void write() {
 //        generateConfigOption("settings.allow-graceful-uuids", true);
         generateConfigOption("settings.delete-duplicate-uuids", false);
         generateConfigOption("settings.save-playerdata-by-uuid", true);
+        generateConfigOption("settings.use-uuid-based-player-lists", false);
         // Log management and rotation
         generateConfigOption("settings.per-day-log-file.info", "This setting causes the server to create a new log file each day. This is useful for log rotation and log file management.");
         generateConfigOption("settings.per-day-log-file.enabled", false);

src/main/java/com/legacyminecraft/poseidon/util/UUIDPlayerList.java

@@ -0,0 +1,119 @@
+package com.legacyminecraft.poseidon.util;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.reflect.TypeToken;
+
+import java.io.*;
+import java.lang.reflect.Type;
+import java.util.*;
+import java.util.logging.Logger;
+
+/**
+ * Dual-indexed player list storing entries by both UUID and lowercase name.
+ * Used for UUID-based ops, bans, and whitelist storage.
+ */
+public class UUIDPlayerList {
+
+    private static final Logger logger = Logger.getLogger("Minecraft");
+    private static final Gson gson = new GsonBuilder().setPrettyPrinting().create();
+    private static final Type LIST_TYPE = new TypeToken<List<PlayerListEntry>>() {}.getType();
+
+    private final Map<UUID, PlayerListEntry> byUUID = new LinkedHashMap<>();
+    private final Map<String, PlayerListEntry> byName = new LinkedHashMap<>();
+
+    public static class PlayerListEntry {
+        public UUID uuid;
+        public String name;
+
+        public PlayerListEntry() {}
+
+        public PlayerListEntry(UUID uuid, String name) {
+            this.uuid = uuid;
+            this.name = name;
+        }
+    }
+
+    public boolean containsUUID(UUID uuid) {
+        return byUUID.containsKey(uuid);
+    }
+
+    public boolean containsName(String name) {
+        return byName.containsKey(name.toLowerCase());
+    }
+
+    public void add(UUID uuid, String name) {
+        PlayerListEntry entry = new PlayerListEntry(uuid, name);
+        // Remove any existing entry with this UUID or name to avoid duplicates
+        removeByUUID(uuid);
+        removeByName(name);
+        byUUID.put(uuid, entry);
+        byName.put(name.toLowerCase(), entry);
+    }
+
+    public void removeByUUID(UUID uuid) {
+        PlayerListEntry entry = byUUID.remove(uuid);
+        if (entry != null) {
+            byName.remove(entry.name.toLowerCase());
+        }
+    }
+
+    public void removeByName(String name) {
+        PlayerListEntry entry = byName.remove(name.toLowerCase());
+        if (entry != null) {
+            byUUID.remove(entry.uuid);
+        }
+    }
+
+    public Set<String> getNames() {
+        Set<String> names = new HashSet<>();
+        for (PlayerListEntry entry : byUUID.values()) {
+            names.add(entry.name.toLowerCase());
+        }
+        return names;
+    }
+
+    public Collection<PlayerListEntry> entries() {
+        return Collections.unmodifiableCollection(byUUID.values());
+    }
+
+    public void clear() {
+        byUUID.clear();
+        byName.clear();
+    }
+
+    public boolean loadFromJson(File file) {
+        if (!file.exists()) {
+            return false;
+        }
+        try (Reader reader = new FileReader(file)) {
+            List<PlayerListEntry> entries = gson.fromJson(reader, LIST_TYPE);
+            if (entries != null) {
+                clear();
+                for (PlayerListEntry entry : entries) {
+                    if (entry.uuid != null && entry.name != null) {
+                        byUUID.put(entry.uuid, entry);
+                        byName.put(entry.name.toLowerCase(), entry);
+                    }
+                }
+            }
+            return true;
+        } catch (Exception e) {
+            logger.warning("Failed to load UUID player list from " + file.getName() + ": " + e);
+            return false;
+        }
+    }
+
+    public void saveToJson(File file) {
+        try (Writer writer = new FileWriter(file)) {
+            List<PlayerListEntry> entries = new ArrayList<>(byUUID.values());
+            gson.toJson(entries, LIST_TYPE, writer);
+        } catch (Exception e) {
+            logger.warning("Failed to save UUID player list to " + file.getName() + ": " + e);
+        }
+    }
+
+    public int size() {
+        return byUUID.size();
+    }
+}