import java.io.*;
import java.net.*;

/**
 * Vernetzte Systeme, Uebung 6, Aufgabe 25
 * @author Markus Keller
 */
public class FTPClient {

	public static final boolean OK = true;
	public static final boolean TERMINATED = false;

	public static int state = 0;
	public static Socket socket;
	public static PrintWriter out;
	public static BufferedReader in;

	/**
	 * Implements the finite state machine (endlicher Zustandsautomat).
	 * @param	s	a reply line from the FTP-Server
	 * @return	OK or TERMINATED
	 */
	public static boolean handleInput (String s) {
		// certainly not a state code (too short)
		if (s.length() < 3) return OK;

		if (!Character.isDigit (s.charAt(0))) return OK;

		// is it a comment? ('-' after state code)
		if (s.charAt(3) == '-') return OK;

		String code = s.substring(0,3);

		switch(state) {
		case 0:
			if (code.equals("220")) {
				send("USER ftp");
				state = 1;
				return OK;
			} else {
				error(code);
				state = 5;
				return TERMINATED;
			}
			
		case 1:
			if (code.equals("331")) {
				send("PASS foo@inf.ethz.ch");
				state = 2;
			} else {
				send("QUIT");
				state = 4;
			}
			return OK;
				
		case 2:
			if (code.equals("230")) {
				send("STAT");
				state = 3;
			} else {
				send("QUIT");
				state = 4;
			}
			return OK;
			
		case 3:
			if (code.equals("211")) {
				send("QUIT");
				state = 4;
			} else {
				send("QUIT");
				state = 4;
			} // exercice: shorten case 3 ;-)
			return OK;

		case 4:
			if (code.equals("221")) {
				state = 5;
			} else {
				error(code);
				state = 5;
			}
			return TERMINATED;
			
		case 5:
			System.out.println("normal beendet.");
			return TERMINATED;
	
		default:
			System.out.println("illegaler Zustand: " + code);
			return TERMINATED;
		}
	}
	
	
	static void send(String ftpCommand) {
		out.println(ftpCommand);
		System.out.print("state " + state);	// may be commented out...
		System.out.println("> " + ftpCommand);
	}
	
	
	static void error(String inLine) {
		System.err.println("falsche Eingabe: " + inLine);
	}
	
	
	/**
	 * Usage: java FTPClient <FTP-Server>
	 */
	public static void main(String[] args) throws Exception {
		socket = new Socket(args[0], 21);
		out = new PrintWriter(socket.getOutputStream(), true);
		in = new BufferedReader(
				new InputStreamReader(socket.getInputStream()));

		String fromServer;

		while ((fromServer = in.readLine()) != null) {
		    //System.out.println("Server: " + fromServer);
			System.out.println(fromServer);
			if (handleInput(fromServer) == TERMINATED) {
				break;
			}
		}

		out.close();
		in.close();
		socket.close();
	}

}