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

import envoy.server.data.PersistenceManager;
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)
				try {
					authenticated = PersistenceManager
						.getInstance().getUserByID(((AuthenticatedRequest<?>) obj).getUserID())
						.getID() == ConnectionManager.getInstance()
							.getUserIDBySocketID(message.socketId);

					// Class cast exception and NullPointerException are valid here and signify a
					// failed authentication
				} catch (ClassCastException | NullPointerException e) {} finally {
					obj = ((AuthenticatedRequest<?>) obj).getRequest();
				}
			logger.log(Level.INFO,
				"Received " + (authenticated ? "" : "un") + "authenticated " + obj);

			refer(message.socketId, writeProxy, obj, authenticated);
		} catch (IOException | ClassNotFoundException e) {
			logger.log(Level.WARNING,
				"An exception occurred when reading in an object: " + e);
		}
	}

	/**
	 * 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);
				}
			}
		}
	}
}