package envoy.server.net;

import java.io.*;
import java.lang.reflect.ParameterizedType;
import java.util.Set;
import java.util.logging.*;

import com.jenkov.nioserver.*;
import com.jenkov.nioserver.Message;

import envoy.data.AuthenticatedRequest;
import envoy.util.EnvoyLog;

import envoy.server.data.*;
import envoy.server.processors.ObjectProcessor;

/**
 * Handles incoming objects.
 *
 * @author Kai S. K. Engelbart
 * @since Envoy Server Standalone v0.1-alpha
 */
public final class ObjectMessageProcessor implements IMessageProcessor {

	private final Set<ObjectProcessor<?>> processors;

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

	/**
	 * The constructor to set the {@link ObjectProcessor}s.
	 *
	 * @param processors the {@link ObjectProcessor} to set
	 * @since Envoy Server Standalone v0.1-alpha
	 */
	public ObjectMessageProcessor(Set<ObjectProcessor<?>> processors) {
		this.processors = processors;
	}

	@Override
	public void process(Message message, WriteProxy writeProxy) {
		try (ObjectInputStream in =
			new ObjectInputStream(new ByteArrayInputStream(message.sharedArray, message.offset + 4,
				message.length - 4))) {
			Object obj = in.readObject();
			if (obj == null) {
				logger.warning("Received a null object");
				return;
			}

			// authenticate requests if necessary
			boolean authenticated = false;

			if (obj instanceof AuthenticatedRequest) {
				Contact contact = PersistenceManager.getInstance()
					.getContactByID(((AuthenticatedRequest<?>) obj).getUserID());

				// Validating the authenticity of the request
				if (contact == null || contact instanceof Group
					|| !((AuthenticatedRequest<?>) obj).getAuthentication()
						.equals(((User) contact).getAuthToken())) {

					// Invalid request
					logger.log(Level.INFO,
						"A user tried to perform an authenticated request but could not identify himself. Discarding request.");
					return;
				}

				// Valid request
				logger.log(Level.INFO, "A user successfully authenticated a request for " + obj);
				authenticated	= true;
				obj				= ((AuthenticatedRequest<?>) obj).getRequest();
			} else
				logger.log(Level.FINE, "Received unauthenticated " + obj);

			refer(message.socketId, writeProxy, obj, authenticated);
		} catch (IOException | ClassNotFoundException e) {
			e.printStackTrace();
		}
	}

	/**
	 * Executes the appropriate {@link ObjectProcessor} for the given input ({@code obj}), if any is
	 * present.
	 */
	@SuppressWarnings("unchecked")
	private void refer(long socketID, WriteProxy writeProxy, Object obj, boolean authenticated) {

		// Get processor and input class and process object
		for (@SuppressWarnings("rawtypes")
		ObjectProcessor p : processors) {
			Class<?> c = (Class<?>) ((ParameterizedType) p.getClass().getGenericInterfaces()[0])
				.getActualTypeArguments()[0];
			if (c.equals(obj.getClass())) {
				if (!authenticated && p.isAuthenticationRequired()) {
					logger.log(Level.INFO,
						"Discarding request as no authentication has been provided");
					return;
				}

				try {
					p.process(c.cast(obj), socketID, new ObjectWriteProxy(writeProxy));
					break;
				} catch (IOException e) {
					logger.log(Level.SEVERE, "Exception during processor execution: ", e);
				}
			}
		}
	}
}