package envoy.client.net;

import java.io.*;
import java.net.Socket;
import java.util.concurrent.TimeoutException;
import java.util.logging.*;

import envoy.client.data.*;
import envoy.client.event.EnvoyCloseEvent;
import envoy.data.*;
import envoy.event.*;
import envoy.util.*;

import dev.kske.eventbus.*;
import dev.kske.eventbus.Event;

/**
 * Establishes a connection to the server, performs a handshake and delivers
 * certain objects to the server.
 *
 * @author Kai S. K. Engelbart
 * @author Maximilian Käfer
 * @author Leon Hofmeister
 * @since Envoy Client v0.1-alpha
 */
public final class Client implements EventListener, Closeable {

	// Connection handling
	private Socket		socket;
	private Receiver	receiver;
	private boolean		online;

	// Asynchronously initialized during handshake
	private volatile User		sender;
	private volatile boolean	rejected;

	// Configuration, logging and event management
	private static final ClientConfig	config		= ClientConfig.getInstance();
	private static final Logger			logger		= EnvoyLog.getLogger(Client.class);
	private static final EventBus		eventBus	= EventBus.getInstance();

	/**
	 * Constructs a client and registers it as an event listener.
	 *
	 * @since Envoy Client v0.2-beta
	 */
	public Client() { eventBus.registerListener(this); }

	/**
	 * Enters the online mode by acquiring a user ID from the server. As a
	 * connection has to be established and a handshake has to be made, this method
	 * will block for up to 5 seconds. If the handshake does exceed this time limit,
	 * an exception is thrown.
	 *
	 * @param credentials the login credentials of the user
	 * @param cacheMap    the map of all caches needed
	 * @throws TimeoutException     if the server could not be reached
	 * @throws IOException          if the login credentials could not be written
	 * @throws InterruptedException if the current thread is interrupted while
	 *                              waiting for the handshake response
	 */
	public void performHandshake(LoginCredentials credentials, CacheMap cacheMap) throws TimeoutException, IOException, InterruptedException {
		if (online) throw new IllegalStateException("Handshake has already been performed successfully");
		rejected = false;

		// Establish TCP connection
		logger.log(Level.FINER, String.format("Attempting connection to server %s:%d...", config.getServer(), config.getPort()));
		socket = new Socket(config.getServer(), config.getPort());
		logger.log(Level.FINE, "Successfully established TCP connection to server");

		// Create object receiver
		receiver = new Receiver(socket.getInputStream());

		// Register user creation processor, contact list processor, message cache and
		// authentication token
		receiver.registerProcessor(User.class, sender -> this.sender = sender);
		receiver.registerProcessors(cacheMap.getMap());

		// Start receiver
		receiver.start();

		// Write login credentials
		SerializationUtils.writeBytesWithLength(credentials, socket.getOutputStream());

		// Wait for a maximum of five seconds to acquire the sender object
		final long start = System.currentTimeMillis();
		while (sender == null) {

			// Quit immediately after handshake rejection
			// This method can then be called again
			if (rejected) {
				socket.close();
				receiver.removeAllProcessors();
				return;
			}

			if (System.currentTimeMillis() - start > 5000) {
				rejected = true;
				throw new TimeoutException("Did not log in after 5 seconds");
			}
			Thread.sleep(500);
		}

		online = true;
		logger.log(Level.INFO, "Handshake completed.");
	}

	/**
	 * Initializes the {@link Receiver} used to process data sent from the server to
	 * this client.
	 *
	 * @param localDB  the local database used to persist the current
	 *                 {@link IDGenerator}
	 * @param cacheMap the map of all caches needed
	 * @throws IOException if no {@link IDGenerator} is present and none could be
	 *                     requested from the server
	 * @since Envoy Client v0.2-alpha
	 */
	public void initReceiver(LocalDB localDB, CacheMap cacheMap) throws IOException {
		checkOnline();

		// Remove all processors as they are only used during the handshake
		receiver.removeAllProcessors();

		// Relay cached messages and message status changes
		cacheMap.get(Message.class).setProcessor(eventBus::dispatch);
		cacheMap.get(GroupMessage.class).setProcessor(eventBus::dispatch);
		cacheMap.get(MessageStatusChange.class).setProcessor(eventBus::dispatch);
		cacheMap.get(GroupMessageStatusChange.class).setProcessor(eventBus::dispatch);

		// Request a generator if none is present or the existing one is consumed
		if (!localDB.hasIDGenerator() || !localDB.getIDGenerator().hasNext()) requestIDGenerator();

		// Relay caches
		cacheMap.getMap().values().forEach(Cache::relay);
	}

	/**
	 * Sends an object to the server.
	 *
	 * @param obj the object to send
	 * @throws IllegalStateException if the client is not online
	 * @throws RuntimeException      if the object serialization failed
	 * @since Envoy Client v0.2-beta
	 */
	public void send(Serializable obj) throws IllegalStateException, RuntimeException {
		checkOnline();
		logger.log(Level.FINE, "Sending " + obj);
		try {
			SerializationUtils.writeBytesWithLength(obj, socket.getOutputStream());
		} catch (final IOException e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * Sends a message to the server. The message's status will be incremented once
	 * it was delivered successfully.
	 *
	 * @param message the message to send
	 * @since Envoy Client v0.3-alpha
	 */
	public void sendMessage(Message message) {
		send(message);
		message.nextStatus();
	}

	/**
	 * Requests a new {@link IDGenerator} from the server.
	 *
	 * @since Envoy Client v0.3-alpha
	 */
	public void requestIDGenerator() {
		logger.log(Level.INFO, "Requesting new id generator...");
		send(new IDGeneratorRequest());
	}

	@Event(eventType = HandshakeRejection.class, priority = 1000)
	private void onHandshakeRejection() { rejected = true; }

	@Override
	@Event(eventType = EnvoyCloseEvent.class, priority = 50)
	public void close() {
		if (online) {
			logger.log(Level.INFO, "Closing connection...");
			try {

				// The sender must be reset as otherwise the handshake is immediately closed
				sender	= null;
				online	= false;
				socket.close();
			} catch (final IOException e) {
				logger.log(Level.WARNING, "Failed to close socket: ", e);
			}
		}
	}

	/**
	 * Ensured that the client is online.
	 *
	 * @throws IllegalStateException if the client is not online
	 * @since Envoy Client v0.3-alpha
	 */
	private void checkOnline() throws IllegalStateException { if (!online) throw new IllegalStateException("Client is not online"); }

	/**
	 * @return the {@link User} as which this client is logged in
	 * @since Envoy Client v0.1-alpha
	 */
	public User getSender() { return sender; }

	/**
	 * Sets the client user which is used to send messages.
	 *
	 * @param clientUser the client user to set
	 * @since Envoy Client v0.2-alpha
	 */
	public void setSender(User clientUser) { sender = clientUser; }

	/**
	 * @return the {@link Receiver} used by this {@link Client}
	 * @since v0.2-alpha
	 */
	public Receiver getReceiver() { return receiver; }

	/**
	 * @return {@code true} if a connection to the server could be established
	 * @since Envoy Client v0.2-alpha
	 */
	public boolean isOnline() { return online; }
}