package be.nikiroo.utils.serial.server;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;

import be.nikiroo.utils.TraceHandler;

/**
 * This class implements a simple server that can listen for connections and
 * send/receive objects.
 * <p>
 * Note: this {@link Server} has to be discarded after use (cannot be started
 * twice).
 * 
 * @author niki
 */
abstract class Server implements Runnable {
	protected final String key;
	protected long id = 0;

	private final String name;
	private final Object lock = new Object();
	private final Object counterLock = new Object();

	private ServerSocket ss;
	private int port;

	private boolean started;
	private boolean exiting = false;
	private int counter;

	private long bytesReceived;
	private long bytesSent;

	private TraceHandler tracer = new TraceHandler();

	/**
	 * Create a new {@link ConnectActionServer} to handle a request.
	 * 
	 * @param s
	 *            the socket to service
	 * 
	 * @return the action
	 */
	abstract ConnectActionServer createConnectActionServer(Socket s);

	/**
	 * Create a new server that will start listening on the network when
	 * {@link Server#start()} is called.
	 * 
	 * @param port
	 *            the port to listen on, or 0 to assign any unallocated port
	 *            found (which can later on be queried via
	 *            {@link Server#getPort()}
	 * @param key
	 *            an optional key to encrypt all the communications (if NULL,
	 *            everything will be sent in clear text)
	 * 
	 * @throws IOException
	 *             in case of I/O error
	 * @throws UnknownHostException
	 *             if the IP address of the host could not be determined
	 * @throws IllegalArgumentException
	 *             if the port parameter is outside the specified range of valid
	 *             port values, which is between 0 and 65535, inclusive
	 */
	public Server(int port, String key) throws IOException {
		this((String) null, port, key);
	}

	/**
	 * Create a new server that will start listening on the network when
	 * {@link Server#start()} is called.
	 * <p>
	 * All the communications will happen in plain text.
	 * 
	 * @param name
	 *            the server name (only used for debug info and traces)
	 * @param port
	 *            the port to listen on
	 * 
	 * @throws IOException
	 *             in case of I/O error
	 * @throws UnknownHostException
	 *             if the IP address of the host could not be determined
	 * @throws IllegalArgumentException
	 *             if the port parameter is outside the specified range of valid
	 *             port values, which is between 0 and 65535, inclusive
	 */
	public Server(String name, int port) throws IOException {
		this(name, port, null);
	}

	/**
	 * Create a new server that will start listening on the network when
	 * {@link Server#start()} is called.
	 * 
	 * @param name
	 *            the server name (only used for debug info and traces)
	 * @param port
	 *            the port to listen on
	 * @param key
	 *            an optional key to encrypt all the communications (if NULL,
	 *            everything will be sent in clear text)
	 * 
	 * @throws IOException
	 *             in case of I/O error
	 * @throws UnknownHostException
	 *             if the IP address of the host could not be determined
	 * @throws IllegalArgumentException
	 *             if the port parameter is outside the specified range of valid
	 *             port values, which is between 0 and 65535, inclusive
	 */
	public Server(String name, int port, String key) throws IOException {
		this.name = name;
		this.port = port;
		this.key = key;
		this.ss = new ServerSocket(port);

		if (this.port == 0) {
			this.port = this.ss.getLocalPort();
		}
	}

	/**
	 * The traces handler for this {@link Server}.
	 * 
	 * @return the traces handler
	 */
	public TraceHandler getTraceHandler() {
		return tracer;
	}

	/**
	 * The traces handler for this {@link Server}.
	 * 
	 * @param tracer
	 *            the new traces handler
	 */
	public void setTraceHandler(TraceHandler tracer) {
		if (tracer == null) {
			tracer = new TraceHandler(false, false, false);
		}

		this.tracer = tracer;
	}

	/**
	 * The name of this {@link Server} if any.
	 * <p>
	 * Used for traces and debug purposes only.
	 * 
	 * @return the name or NULL
	 */
	public String getName() {
		return name;
	}

	/**
	 * Return the assigned port.
	 * 
	 * @return the assigned port
	 */
	public int getPort() {
		return port;
	}

	/**
	 * The total amount of bytes received.
	 * 
	 * @return the amount of bytes received
	 */
	public long getBytesReceived() {
		return bytesReceived;
	}

	/**
	 * The total amount of bytes sent.
	 * 
	 * @return the amount of bytes sent
	 */
	public long getBytesSent() {
		return bytesSent;
	}

	/**
	 * Start the server (listen on the network for new connections).
	 * <p>
	 * Can only be called once.
	 * <p>
	 * This call is asynchronous, and will just start a new {@link Thread} on
	 * itself (see {@link Server#run()}).
	 */
	public void start() {
		new Thread(this).start();
	}

	/**
	 * Start the server (listen on the network for new connections).
	 * <p>
	 * Can only be called once.
	 * <p>
	 * You may call it via {@link Server#start()} for an asynchronous call, too.
	 */
	@Override
	public void run() {
		ServerSocket ss = null;
		boolean alreadyStarted = false;
		synchronized (lock) {
			ss = this.ss;
			if (!started && ss != null) {
				started = true;
			} else {
				alreadyStarted = started;
			}
		}

		if (alreadyStarted) {
			tracer.error(name + ": cannot start server on port " + port
					+ ", it is already started");
			return;
		}

		if (ss == null) {
			tracer.error(name + ": cannot start server on port " + port
					+ ", it has already been used");
			return;
		}

		try {
			tracer.trace(name + ": server starting on port " + port + " ("
					+ (key != null ? "encrypted" : "plain text") + ")");

			while (started && !exiting) {
				count(1);
				final Socket s = ss.accept();
				new Thread(new Runnable() {
					@Override
					public void run() {
						ConnectActionServer action = null;
						try {
							action = createConnectActionServer(s);
							action.connect();
						} finally {
							count(-1);
							if (action != null) {
								bytesReceived += action.getBytesReceived();
								bytesSent += action.getBytesSent();
							}
						}
					}
				}).start();
			}

			// Will be covered by @link{Server#stop(long)} for timeouts
			while (counter > 0) {
				Thread.sleep(10);
			}
		} catch (Exception e) {
			if (counter > 0) {
				onError(e);
			}
		} finally {
			try {
				ss.close();
			} catch (Exception e) {
				onError(e);
			}

			this.ss = null;

			started = false;
			exiting = false;
			counter = 0;

			tracer.trace(name + ": client terminated on port " + port);
		}
	}

	/**
	 * Will stop the server, synchronously and without a timeout.
	 */
	public void stop() {
		tracer.trace(name + ": stopping server");
		stop(0, true);
	}

	/**
	 * Stop the server.
	 * 
	 * @param timeout
	 *            the maximum timeout to wait for existing actions to complete,
	 *            or 0 for "no timeout"
	 * @param wait
	 *            wait for the server to be stopped before returning
	 *            (synchronous) or not (asynchronous)
	 */
	public void stop(final long timeout, final boolean wait) {
		if (wait) {
			stop(timeout);
		} else {
			new Thread(new Runnable() {
				@Override
				public void run() {
					stop(timeout);
				}
			}).start();
		}
	}

	/**
	 * Stop the server (synchronous).
	 * 
	 * @param timeout
	 *            the maximum timeout to wait for existing actions to complete,
	 *            or 0 for "no timeout"
	 */
	private void stop(long timeout) {
		tracer.trace(name + ": server stopping on port " + port);
		synchronized (lock) {
			if (started && !exiting) {
				exiting = true;

				try {
					getConnectionToMe().connect();
					long time = 0;
					while (ss != null && timeout > 0 && timeout > time) {
						Thread.sleep(10);
						time += 10;
					}
				} catch (Exception e) {
					if (ss != null) {
						counter = 0; // will stop the main thread
						onError(e);
					}
				}
			}
		}

		// return only when stopped
		while (started || exiting) {
			try {
				Thread.sleep(10);
			} catch (InterruptedException e) {
			}
		}
	}

	/**
	 * Return a connection to this server (used by the Exit code to send an exit
	 * message).
	 * 
	 * @return the connection
	 * 
	 * @throws UnknownHostException
	 *             the host should always be NULL (localhost)
	 * @throws IOException
	 *             in case of I/O error
	 */
	abstract protected ConnectActionClient getConnectionToMe()
			throws UnknownHostException, IOException;

	/**
	 * Change the number of currently serviced actions.
	 * 
	 * @param change
	 *            the number to increase or decrease
	 * 
	 * @return the current number after this operation
	 */
	private int count(int change) {
		synchronized (counterLock) {
			counter += change;
			return counter;
		}
	}

	/**
	 * This method will be called on errors.
	 * <p>
	 * By default, it will only call the trace handler (so you may want to call
	 * super {@link Server#onError} if you override it).
	 * 
	 * @param e
	 *            the error
	 */
	protected void onError(Exception e) {
		tracer.error(e);
	}

	/**
	 * Return the next ID to use.
	 * 
	 * @return the next ID
	 */
	protected synchronized long getNextId() {
		return id++;
	}

	/**
	 * Method called when
	 * {@link ServerObject#onRequest(ConnectActionServerObject, Object, long)}
	 * has successfully finished.
	 * <p>
	 * Can be used to know how much data was transmitted.
	 * 
	 * @param id
	 *            the ID used to identify the request
	 * @param bytesReceived
	 *            the bytes received during the request
	 * @param bytesSent
	 *            the bytes sent during the request
	 */
	@SuppressWarnings("unused")
	protected void onRequestDone(long id, long bytesReceived, long bytesSent) {
	}
}