package gov.jdaccs.comm;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import com.jcraft.jsch.*;

/**
 * SecureShellChannel is a class that creates a Java Secure Channel using the
 * JCraft JSch library.
 * 
 * @author Jonathon Sanders
 * @version 2.0.0
 */
public abstract class SecureShellChannel
{
	protected static final int PORT = 22;
	protected static final int TIMEOUT_MILLISECONDS = 60000;

	protected String host;
	protected Properties config;
	protected JSch ssh;
	protected Session session;
	protected Channel channel;

	/**
	 * Creates a SecureShellChannel to connect to the specified host.
	 * 
	 * @param host
	 *            the host to connect to through the secure channel.
	 */
	public SecureShellChannel(String host)
	{
		this.host = host;
		config = new Properties();
		// Example says this should be for testing only.
		config.put("StrictHostKeyChecking", "no");
		ssh = new JSch();
	}

	/**
	 * Application specific way to prompt user for credentials to create and log
	 * into SSH session.
	 */
	public abstract void promptUser();

	/**
	 * Creates the SSH session.
	 * 
	 * @param username
	 *            username.
	 * @param password
	 *            password.
	 * @throws JSchException
	 */
	public void createSession(String username, char[] password)
			throws JSchException
	{
		String key = "";

		for (int n = 0; n < password.length; n++)
		{
			key += password[n];
		}

		session = ssh.getSession(username, host, PORT);
		session.setPassword(key);
		session.setConfig(config);

		// Force Garbage collector to run to get rid of password.
		System.gc();
	}

	/**
	 * Connects to the SSH session.
	 * 
	 * @throws JSchException
	 */
	public void connect() throws JSchException
	{
		// Check if Session exists.
		if (session == null) throw new NullPointerException(
				"Session is null, call createSession(username, password)!");

		session.connect(TIMEOUT_MILLISECONDS);
	}

	/**
	 * Returns if the Session is connected.
	 * 
	 * @return true if connected, false otherwise.
	 */
	public boolean isConnected()
	{
		// Check if Session exists.
		if (session == null) return false;

		return session.isConnected();
	}

	/**
	 * Sends commands to the host through a secure channel.
	 * 
	 * @param command
	 *            the command to send.
	 * @return the output returned from the command.
	 * @throws IOException
	 * @throws JSchException
	 * @throws NullPointerException
	 */
	public String sendCommand(String command) throws IOException,
			JSchException, NullPointerException
	{
		// Check if Session exists
		if (session == null) throw new NullPointerException(
				"Session is null, call createSession(username, password), then connect()!");

		if (!session.isConnected())
		{
			System.out.println("connect again");
			session.connect(TIMEOUT_MILLISECONDS);
		}

		System.out.println("String Builder");
		StringBuilder output = new StringBuilder();

		System.out.println("Create Channel");
		channel = session.openChannel("exec");
		System.out.println("Sending command: " + command);
		((ChannelExec) channel).setCommand(command);
		InputStream commandOutput = channel.getInputStream();
		channel.connect();

		try
		{
			Thread.sleep(500);
		}
		catch (InterruptedException ie)
		{
			ie.printStackTrace();
		}

		int readByte = commandOutput.read();

		while (readByte != 0xffffffff)
		{
			output.append((char) readByte);
			readByte = commandOutput.read();
		}

		// close Channel
		channel.disconnect();

		// close Session
		session.disconnect();
		
		return output.toString();
	}

	/**
	 * Closes the SSH session.
	 */
	public void shutdown()
	{
		// close Session
		if (session != null)
		{
			// close Session
			session.disconnect();
		}
	}
}