Added an event for handling duplicate logins (#2430)

src/pocketmine/event/player/PlayerDuplicateLoginEvent.php

@@ -0,0 +1,71 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\event\player;
+
+use pocketmine\event\Cancellable;
+use pocketmine\event\Event;
+use pocketmine\network\mcpe\NetworkSession;
+
+/**
+ * Called when a player connects with a username or UUID that is already used by another player on the server.
+ * If cancelled, the newly connecting session will be disconnected; otherwise, the existing player will be disconnected.
+ */
+class PlayerDuplicateLoginEvent extends Event implements Cancellable{
+
+	/** @var NetworkSession */
+	private $connectingSession;
+	/** @var NetworkSession */
+	private $existingSession;
+	/** @var string */
+	private $disconnectMessage = "Logged in from another location";
+
+	public function __construct(NetworkSession $connectingSession, NetworkSession $existingSession){
+		$this->connectingSession = $connectingSession;
+		$this->existingSession = $existingSession;
+	}
+
+	public function getConnectingSession() : NetworkSession{
+		return $this->connectingSession;
+	}
+
+	public function getExistingSession() : NetworkSession{
+		return $this->existingSession;
+	}
+
+	/**
+	 * Returns the message shown to the session which gets disconnected.
+	 *
+	 * @return string
+	 */
+	public function getDisconnectMessage() : string{
+		return $this->disconnectMessage;
+	}
+
+	/**
+	 * @param string $message
+	 */
+	public function setDisconnectMessage(string $message) : void{
+		$this->disconnectMessage = $message;
+	}
+}