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.*;
import envoy.data.*;
import envoy.event.*;
import envoy.event.Event;
import envoy.event.contact.*;
import envoy.util.*;

import dev.kske.eventbus.*;

/**
 * Establishes a connection to the server, performs a handshake and delivers
 * certain objects to the server.
 * <p>
 * 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 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");

		// 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());
		receiver.registerProcessor(HandshakeRejection.class, evt -> { rejected = true; eventBus.dispatch(evt); });
		receiver.registerProcessor(NewAuthToken.class, eventBus::dispatch);

		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
		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) 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();

		// Process incoming messages
		final var	receivedMessageProcessor			= new ReceivedMessageProcessor();
		final var	receivedGroupMessageProcessor		= new ReceivedGroupMessageProcessor();
		final var	messageStatusChangeProcessor		= new MessageStatusChangeProcessor();
		final var	groupMessageStatusChangeProcessor	= new GroupMessageStatusChangeProcessor();

		receiver.registerProcessor(GroupMessage.class, receivedGroupMessageProcessor);
		receiver.registerProcessor(Message.class, receivedMessageProcessor);
		receiver.registerProcessor(MessageStatusChange.class, messageStatusChangeProcessor);
		receiver.registerProcessor(GroupMessageStatusChange.class, groupMessageStatusChangeProcessor);

		// Relay cached messages and message status changes
		cacheMap.get(Message.class).setProcessor(receivedMessageProcessor);
		cacheMap.get(GroupMessage.class).setProcessor(receivedGroupMessageProcessor);
		cacheMap.get(MessageStatusChange.class).setProcessor(messageStatusChangeProcessor);
		cacheMap.get(GroupMessageStatusChange.class).setProcessor(groupMessageStatusChangeProcessor);

		// Process user status changes
		receiver.registerProcessor(UserStatusChange.class, eventBus::dispatch);

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

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

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

		// Process contact operations
		receiver.registerProcessor(ContactOperation.class, eventBus::dispatch);

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

		// Process IsTyping events
		receiver.registerProcessor(IsTyping.class, eventBus::dispatch);

		// Process PasswordChangeResults
		receiver.registerProcessor(PasswordChangeResult.class, eventBus::dispatch);

		// Process ProfilePicChanges
		receiver.registerProcessor(ProfilePicChange.class, eventBus::dispatch);

		// Process requests to not send any more attachments as they will not be shown
		// to other users
		receiver.registerProcessor(NoAttachments.class, eventBus::dispatch);

		// Process group creation results - they might have been disabled on the server
		receiver.registerProcessor(GroupCreationResult.class, 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 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 { if (online) 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.log(Level.INFO, "Requesting new id generator...");
		writeObject(new IDGeneratorRequest());
	}

	/**
	 * Sends the value of a send event to the server.
	 *
	 * @param evt the send event to extract the value from
	 * @since Envoy Client v0.2-beta
	 */
	@dev.kske.eventbus.Event
	private void onSendEvent(SendEvent evt) {
		try {
			sendEvent(evt.get());
		} catch (final IOException e) {
			logger.log(Level.WARNING, "An error occurred when trying to send " + evt, e);
		}
	}

	@Override
	@dev.kske.eventbus.Event(eventType = EnvoyCloseEvent.class, priority = 800)
	public void close() {
		if (online) {
			logger.log(Level.INFO, "Closing connection...");
			try {
				socket.close();
			} catch (final IOException e) {}
		}
	}

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

	private void checkOnline() { 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}
	 */
	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; }
}