Adds UUID fetching on player join. See #12

Whenever a player joins, their names will be checked against a map containing all names which need to be migrated to UUID. All portals the player has created which still use the player name will be updated.

src/main/java/net/knarcraft/stargate/utility/UUIDMigrationHelper.java

@@ -0,0 +1,111 @@
+package net.knarcraft.stargate.utility;
+
+import net.knarcraft.stargate.Stargate;
+import net.knarcraft.stargate.portal.Portal;
+import net.knarcraft.stargate.portal.PortalHandler;
+import net.knarcraft.stargate.portal.PortalOwner;
+import net.knarcraft.stargate.portal.PortalRegistry;
+import org.bukkit.OfflinePlayer;
+import org.bukkit.World;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+
+/**
+ * Helps migrate player names to UUID where necessary
+ */
+public class UUIDMigrationHelper {
+
+    private static Map<String, List<Portal>> playerNamesToMigrate;
+
+    /**
+     * Migrates the player's name to a UUID
+     *
+     * <p>If any portals are missing a UUID for their owner, and the given player is the owner of those portals, the
+     * given player's UUID will be used as UUID for the portals' owner.</p>
+     *
+     * @param player <p>The player to migrate</p>
+     */
+    public static void migrateUUID(OfflinePlayer player) {
+        Map<String, List<Portal>> playersToMigrate = getPlayersToMigrate();
+        String playerName = player.getName();
+
+        //Nothing to do
+        if (!playersToMigrate.containsKey(playerName)) {
+            return;
+        }
+
+        Stargate.debug("PlayerEventListener::migrateUUID", String.format("Migrating name to UUID for player %s",
+                playerName));
+        List<Portal> portalsOwned = playersToMigrate.get(playerName);
+        if (portalsOwned == null) {
+            return;
+        }
+
+        migratePortalsToUUID(portalsOwned, player.getUniqueId());
+
+        //Remove the player to prevent the migration to happen every time the player joins
+        playersToMigrate.remove(playerName);
+    }
+
+    /**
+     * Migrates a list of portals to use UUID instead of only player name
+     *
+     * @param portals  <p>The portals to migrate</p>
+     * @param uniqueId <p>The unique ID of the portals' owner</p>
+     */
+    private static void migratePortalsToUUID(List<Portal> portals, UUID uniqueId) {
+        Set<World> worldsToSave = new HashSet<>();
+
+        //Get the real portal from the copy and set UUID
+        for (Portal portalCopy : portals) {
+            Portal portal = PortalHandler.getByName(portalCopy.getName(), portalCopy.getNetwork());
+            if (portal != null) {
+                portal.getOwner().setUUID(uniqueId);
+                worldsToSave.add(portal.getWorld());
+            }
+        }
+
+        //Need to make sure the changes are saved
+        for (World world : worldsToSave) {
+            PortalFileHelper.saveAllPortals(world);
+        }
+    }
+
+    /**
+     * Gets all player names which need to be migrated to UUIDs
+     *
+     * @return <p>The player names to migrate</p>
+     */
+    private static Map<String, List<Portal>> getPlayersToMigrate() {
+        //Make sure to only go through portals once
+        if (playerNamesToMigrate != null) {
+            return playerNamesToMigrate;
+        }
+
+        playerNamesToMigrate = new HashMap<>();
+        for (Portal portal : PortalRegistry.getAllPortals()) {
+            PortalOwner owner = portal.getOwner();
+            String ownerName = owner.getName();
+
+            //If a UUID is missing, add the portal to the list owned by the player
+            if (owner.getUUID() == null) {
+                List<Portal> portalList = playerNamesToMigrate.get(ownerName);
+                if (portalList == null) {
+                    List<Portal> newList = new ArrayList<>();
+                    newList.add(portal);
+                    playerNamesToMigrate.put(ownerName, newList);
+                } else {
+                    portalList.add(portal);
+                }
+            }
+        }
+        return playerNamesToMigrate;
+    }
+
+}