package envoy.client.net;

import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;

import envoy.client.data.LocalDB;
import envoy.data.Message;
import envoy.event.MessageStatusChangeEvent;
import envoy.util.EnvoyLog;

/**
 * Implements methods to send {@link Message}s and
 * {@link MessageStatusChangeEvent}s to the server or cache them inside a
 * {@link LocalDB} depending on the online status.<br>
 * <br>
 * Project: <strong>envoy-client</strong><br>
 * File: <strong>WriteProxy.java</strong><br>
 * Created: <strong>6 Feb 2020</strong><br>
 *
 * @author Kai S. K. Engelbart
 * @since Envoy Client v0.3-alpha
 */
public class WriteProxy {

	private final Client	client;
	private final LocalDB	localDB;

	private static final Logger logger = EnvoyLog.getLogger(WriteProxy.class);

	/**
	 * Initializes a write proxy using a client and a local database. The
	 * corresponding cache processors are injected into the caches.
	 *
	 * @param client  the client used to send messages and message status change
	 *                events
	 * @param localDB the local database used to cache messages and message status
	 *                change events
	 * @since Envoy Client v0.3-alpha
	 */
	public WriteProxy(Client client, LocalDB localDB) {
		this.client		= client;
		this.localDB	= localDB;

		// Initialize cache processors for messages and message status change events
		localDB.getMessageCache().setProcessor(msg -> {
			try {
				logger.finer("Sending cached " + msg);
				client.sendMessage(msg);

				// Update message state to SENT in localDB
				localDB.getMessage(msg.getID()).ifPresent(Message::nextStatus);
			} catch (IOException e) {
				logger.log(Level.SEVERE, "Could not send cached message", e);
			}
		});
		localDB.getStatusCache().setProcessor(evt -> {
			logger.finer("Sending cached " + evt);
			try {
				client.sendEvent(evt);
			} catch (IOException e) {
				logger.log(Level.SEVERE, "Could not send cached message status change event", e);
			}
		});
	}

	/**
	 * Sends cached {@link Message}s and {@link MessageStatusChangeEvent}s to the
	 * server.
	 *
	 * @since Envoy Client v0.3-alpha
	 */
	public void flushCache() {
		// Send messages
		localDB.getMessageCache().relay();

		// Send message status change events
		localDB.getStatusCache().relay();
	}

	/**
	 * Delivers a message to the server if online. Otherwise the message is cached
	 * inside the local database.
	 *
	 * @param message the message to send
	 * @throws IOException if the message could not be sent
	 * @since Envoy Client v0.3-alpha
	 */
	public void writeMessage(Message message) throws IOException {
		if (client.isOnline()) client.sendMessage(message);
		else localDB.getMessageCache().accept(message);
	}

	/**
	 * Delivers a message status change event to the server if online. Otherwise the
	 * event is cached inside the local database.
	 *
	 * @param evt the event to send
	 * @throws IOException if the event could not be sent
	 * @since Envoy Client v0.3-alpha
	 */
	public void writeMessageStatusChangeEvent(MessageStatusChangeEvent evt) throws IOException {
		if (client.isOnline()) client.sendEvent(evt);
		else localDB.getStatusCache().accept(evt);
	}
}