package pt.iscte.ci.authentication;

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;

import net.sourceforge.fenixedu._development.PropertiesManager;
import net.sourceforge.fenixedu.applicationTier.Servico.ExcepcaoAutenticacao;
import net.sourceforge.fenixedu.domain.Person;

public class PopUtils {

    private static final String CHECK_POP_SERVER;

    private static final String POP_TIMEOUT = "pop.timeout";

    private final static String POP_SERVER = "pop.server";

    private final static String POP_PORT = "pop.port";

    private static String popServer = "pop.iscte.pt";

    private static int popPort = 110;

    private static final String BAD_AUTHENTICATION = "bad.authentication";

    private static final int SO_TIMEOUT = 60000;

    private static int popTimeOut = SO_TIMEOUT;

    static {
	CHECK_POP_SERVER = PropertiesManager.getProperty("pop.check.enabled");
	
	if (PropertiesManager.getProperty(POP_SERVER) != null)
	    popServer = PropertiesManager.getProperty(POP_SERVER);
	if (PropertiesManager.getProperty(POP_PORT) != null)
	    popPort = PropertiesManager.getIntegerProperty(POP_PORT);
	if (PropertiesManager.getProperty(POP_TIMEOUT) != null)
	    popTimeOut = PropertiesManager.getIntegerProperty(POP_TIMEOUT);
    }

    public static void authenticate(final Person person, final String username, final String password)
	    throws ExcepcaoAutenticacao {
	if (!checkPop()) {
	    return;
	}

	Socket popHost = null;
	PopComm popComm = null;
	try {
	    popHost = new Socket(popServer, popPort);
	    popComm = new PopComm(popHost, popTimeOut);
	    if (login(popComm, username, password)) {
		return;
	    }
	    throw new ExcepcaoAutenticacao(BAD_AUTHENTICATION + ": " + username);
	} catch (IOException e) {
	    throw new ExcepcaoAutenticacao("error.communication.with.pop", e);
	} finally {
	    if (popComm != null)
		popComm.endConversation();
	}
    }

    public static class PopComm {
	private Socket socket;

	private BufferedReader is;

	private BufferedOutputStream os;

	private static final String OK_MESSAGE = "+OK";

	private static final String ERR_MESSAGE = "-ERR";

	public PopComm(Socket socket, int timeoutReadWrite) throws IOException {
	    this.socket = socket;
	    this.is = new BufferedReader(new InputStreamReader(socket.getInputStream(), "us-ascii"));
	    this.os = new BufferedOutputStream(socket.getOutputStream());
	    socket.setKeepAlive(false);
	    socket.setTcpNoDelay(true);
	    socket.setSoTimeout(timeoutReadWrite);
	    // Read the first hello line and discard it
	    isResponseOK();
	}

	public void endConversation() {
	    try {
		sayToPop("quit");
	    } catch (Exception ignore) {
	    }
	    try {
		is.close();
	    } catch (Exception ignore) {
	    }
	    try {
		os.close();
	    } catch (Exception ignore) {
	    }
	    try {
		socket.close();
	    } catch (Exception ignore) {
	    }
	}

	private boolean isResponseOK() throws IOException {
	    String lineRead = null;
	    lineRead = is.readLine();
	    // System.out.println("read line "+lineRead);
	    // System.out.flush();
	    if (lineRead != null && lineRead.startsWith(OK_MESSAGE))
		return true;
	    else if (lineRead != null && lineRead.startsWith(ERR_MESSAGE))
		return false;
	    else
		throw new IOException("Unknown message '" + lineRead + "' received from pop server!");

	}

	private void writeMessage(String message) throws IOException {
	    // System.out.println("write line "+message);
	    // System.out.flush();
	    byte[] dataBytes = (message + "\r\n").getBytes("us-ascii");
	    os.write(dataBytes);
	    os.flush();
	}

	public boolean sayToPop(String message) throws IOException {
	    writeMessage(message);
	    return isResponseOK();
	}

    }

    // TODO: Access directly the database?
    private static boolean login(final PopComm popComm, final String username, final String password) throws IOException {

	if (!popComm.sayToPop("USER " + username))
	    return false;
	if (!popComm.sayToPop("PASS " + password))
	    return false;

	return true;
    }

    /**
     * 
     * @return Returns true if an access to the email server database should be
     *         performed. It returns false otherwise. This method returns the
     *         property set in the build configuration file, where one specifies
     *         if this should be enabled or not.
     */
    public static boolean checkPop() {
	return CHECK_POP_SERVER == null || "true".equals(CHECK_POP_SERVER);
    }
}