package envoy.server;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import com.jenkov.nioserver.ISocketIdListener;

import envoy.data.User.UserStatus;
import envoy.server.database.PersistenceManager;
import envoy.server.processors.UserStatusChangeProcessor;

/**
 * Project: <strong>envoy-server-standalone</strong><br>
 * File: <strong>ConnectionManager.java</strong><br>
 * Created: <strong>03.01.2020</strong><br>
 *
 * @author Kai S. K. Engelbart
 * @since Envoy Server Standalone v0.1-alpha
 */
public class ConnectionManager implements ISocketIdListener {

	/**
	 * Contains all socket IDs that have not yet performed a handshake / acquired
	 * their corresponding user ID.
	 *
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	private Set<Long> pendingSockets = new HashSet<>();

	/**
	 * Contains all socket IDs that have acquired a user ID as keys to these IDs.
	 *
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	private Map<Long, Long> sockets = new HashMap<>();

	private static ConnectionManager connectionManager = new ConnectionManager();

	private ConnectionManager() {}

	/**
	 * @return a singleton instance of this object
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public static ConnectionManager getInstance() { return connectionManager; }

	@Override
	public void socketCancelled(long socketId) {
		if (!pendingSockets.remove(socketId)) {
			// notifying contacts of this users offline-going
			envoy.server.data.User user = PersistenceManager.getPersistenceManager().getUserById(getUserIdBySocketId(socketId));
			user.setStatus(UserStatus.OFFLINE);
			user.setLastSeen(new Date());
			UserStatusChangeProcessor.updateUserStatus(user);

			// removing the socket
			sockets.entrySet().stream().filter(e -> e.getValue() == socketId).forEach(e -> sockets.remove(e.getValue()));
		}
	}

	@Override
	public void socketRegistered(long socketId) { pendingSockets.add(socketId); }

	/**
	 * Associates a socket ID with a user ID.
	 *
	 * @param userId   the user ID
	 * @param socketId the socket ID
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public void registerUser(long userId, long socketId) {
		sockets.put(userId, socketId);
		pendingSockets.remove(socketId);
	}

	/**
	 * @param userId the ID of the user registered at a socket
	 * @return the ID of the socket
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public long getSocketId(long userId) { return sockets.get(userId); }

	/**
	 * @param socketId the id of the socket whose User is needed
	 * @return the userId associated with this socketId
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public long getUserIdBySocketId(long socketId) {
		return sockets.entrySet().stream().filter((entry) -> entry.getValue().equals(socketId)).findFirst().get().getKey();
	}

	/**
	 * @param userId the ID of the user to check for
	 * @return {@code true} if the user is online
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public boolean isOnline(long userId) { return sockets.containsKey(userId); }

	/**
	 * @return the userId of all users who are currently online
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public List<Long> getOnlineUsers() {
		List<Long> onlineUsers = new ArrayList<>();
		sockets.forEach((userId, unimportant) -> onlineUsers.add(userId));
		return onlineUsers;
	}
}