package envoy.client.net;

import java.io.Closeable;
import java.io.IOException;
import java.net.Socket;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeoutException;
import java.util.logging.Logger;

import envoy.client.data.Cache;
import envoy.client.data.ClientConfig;
import envoy.client.data.LocalDB;
import envoy.client.event.SendEvent;
import envoy.data.*;
import envoy.event.*;
import envoy.event.contact.ContactOperationEvent;
import envoy.event.contact.ContactSearchResult;
import envoy.util.EnvoyLog;
import envoy.util.SerializationUtils;

/**
 * Establishes a connection to the server, performs a handshake and delivers
 * certain objects to the server.<br>
 * <br>
 * Project: <strong>envoy-client</strong><br>
 * File: <strong>Client.java</strong><br>
 * Created: <strong>28 Sep 2019</strong><br>
 *
 * @author Kai S. K. Engelbart
 * @author Maximilian K&auml;fer
 * @author Leon Hofmeister
 * @since Envoy Client v0.1-alpha
 */
public class Client implements Closeable {

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

	// Asynchronously initialized during handshake
	private volatile User					sender;
	private volatile Set<? extends Contact>	contacts;
	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();

	/**
	 * 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 receivedMessageCache a message cache containing all unread messages
	 *                             from the server that can be relayed after
	 *                             initialization
	 * @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, Cache<Message> receivedMessageCache)
			throws TimeoutException, IOException, InterruptedException {
		if (online) throw new IllegalStateException("Handshake has already been performed successfully");
		// Establish TCP connection
		logger.finer(String.format("Attempting connection to server %s:%d...", config.getServer(), config.getPort()));
		socket = new Socket(config.getServer(), config.getPort());
		logger.fine("Successfully established TCP connection to server");

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

		// Register user creation processor, contact list processor and message cache
		receiver.registerProcessor(User.class, sender -> { this.sender = sender; contacts = sender.getContacts(); });
		receiver.registerProcessor(Message.class, receivedMessageCache);
		receiver.registerProcessor(HandshakeRejectionEvent.class, evt -> { rejected = true; eventBus.dispatch(evt); });

		rejected = false;

		// Start receiver
		receiver.start();

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

		// Wait for a maximum of five seconds to acquire the sender object
		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) throw new TimeoutException("Did not log in after 5 seconds");
			Thread.sleep(500);
		}

		online = true;

		// Remove user creation processor
		receiver.removeAllProcessors();

		logger.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 receivedMessageCache a message cache containing all unread messages
	 *                             from the server that can be relayed after
	 *                             initialization
	 * @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, Cache<Message> receivedMessageCache) throws IOException {
		checkOnline();

		// Process incoming messages
		final ReceivedMessageProcessor receivedMessageProcessor = new ReceivedMessageProcessor();
		receiver.registerProcessor(Message.class, receivedMessageProcessor);

		// Relay cached unread messages
		receivedMessageCache.setProcessor(receivedMessageProcessor);

		// Process message status changes
		receiver.registerProcessor(MessageStatusChangeEvent.class, new MessageStatusChangeEventProcessor());

		// Process user status changes
		receiver.registerProcessor(UserStatusChangeEvent.class, new UserStatusChangeProcessor(localDB));

		// Process message ID generation
		receiver.registerProcessor(IDGenerator.class, localDB::setIDGenerator);

		// Process name changes
		receiver.registerProcessor(NameChangeEvent.class, evt -> { localDB.replaceContactName(evt); eventBus.dispatch(evt); });

		// Process contact searches
		receiver.registerProcessor(ContactSearchResult.class, eventBus::dispatch);

		receiver.registerProcessor(Contact.class,
				contacts -> eventBus.dispatch(new ContactOperationEvent(contacts.getContacts().iterator().next(), ElementOperation.ADD)));

		// Process group size changes
		receiver.registerProcessor(GroupResizeEvent.class, evt -> { localDB.updateGroup(evt); eventBus.dispatch(evt); });

		// Send event
		eventBus.register(SendEvent.class, evt -> {
			try {
				sendEvent(evt.get());
			} catch (IOException e) {
				e.printStackTrace();
			}
		});

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

	/**
	 * Creates a new write proxy that uses this client to communicate with the
	 * server.
	 *
	 * @param localDB the local database that the write proxy will use to access
	 *                caches
	 * @return a new write proxy
	 * @since Envoy Client v0.3-alpha
	 */
	public WriteProxy createWriteProxy(LocalDB localDB) { return new WriteProxy(this, localDB); }

	/**
	 * Sends a message to the server. The message's status will be incremented once
	 * it was delivered successfully.
	 *
	 * @param message the message to send
	 * @throws IOException if the message does not reach the server
	 * @since Envoy Client v0.3-alpha
	 */
	public void sendMessage(Message message) throws IOException {
		writeObject(message);
		message.nextStatus();
	}

	/**
	 * Sends an event to the server.
	 *
	 * @param evt the event to send
	 * @throws IOException if the event did not reach the server
	 */
	public void sendEvent(Event<?> evt) throws IOException { writeObject(evt); }

	/**
	 * Requests a new {@link IDGenerator} from the server.
	 *
	 * @throws IOException if the request does not reach the server
	 * @since Envoy Client v0.3-alpha
	 */
	public void requestIdGenerator() throws IOException {
		logger.info("Requesting new id generator...");
		writeObject(new IDGeneratorRequest());
	}

	/**
	 * @return a {@code Map<String, User>} of all users on the server with their
	 *         user names as keys
	 * @since Envoy Client v0.2-alpha
	 */
	public Map<String, Contact> getUsers() {
		checkOnline();
		Map<String, Contact> users = new HashMap<>();
		contacts.forEach(u -> users.put(u.getName(), u));
		users.put(sender.getName(), sender);
		return users;
	}

	@Override
	public void close() throws IOException { if (online) socket.close(); }

	private void writeObject(Object obj) throws IOException {
		checkOnline();
		logger.fine("Sending " + obj);
		SerializationUtils.writeBytesWithLength(obj, socket.getOutputStream());
	}

	private void checkOnline() { if (!online) throw new IllegalStateException("Client is not online"); }

	/**
	 * @return the sender object that represents this client.
	 * @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) { this.sender = clientUser; }

	/**
	 * @return the {@link Receiver} used by this {@link Client}
	 */
	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; }

	/**
	 * @return the contacts of this {@link Client}
	 * @since Envoy Client v0.3-alpha
	 */
	public Set<? extends Contact> getContacts() { return contacts; }

	/**
	 * @param contacts the contacts to set
	 * @since Envoy Client v0.3-alpha
	 */
	public void setContacts(Set<? extends Contact> contacts) { this.contacts = contacts; }
}