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

/**
 * The Finger application connects to a TCP Finger daemon as a client.  
 *
 * @version 1.0
 * @author Sean M. Graham <grahams {of} csh [dot] rit [dot] educational>
 *
 */
public class Finger
{
    /**
     * This is a simple app, so it only really requires a main().
     *
     * @param   args    The command line arguments
     */
    public static void main( String[] args ) {
        String command; // The finger command to send to the remote server
        String host;    // The host we will connect to
        int atIndex;    // The index of the @ in args[0] (-1 if none)

        command = null;
        host = null;
        atIndex = -1;

        // If there were no command-line arguments, we are looking for a 
        // listing of users on the local machine.
        if( args.length > 1 ) {
            System.out.println( "Finger: Too Many Arguments" );
            System.exit(-1);
        }
        else if( args.length > 0 ) {
            command = args[0];

            // An interesting "feature" of the finger protocol is that 
            // according to the RFC, the following is valid:
            // 
            // finger grahams@example.com@iron.cs.rit.edu
            // 
            // As odd as this sounds, most finger servers support this, so
            // we will look for the index of the LAST @ sign to determine
            // where the hostname starts.
            atIndex = command.lastIndexOf( "@" );
            command = command.trim();
        }
        else {
            command = "";
            atIndex = -1;
        }

        // If there is an '@' in the command string, then we need to query a
        // remote server, otherwise we are querying the local machine
        if( atIndex == -1 ) {
            host = "localhost";
        }
        else {
            host = command.substring( atIndex + 1 );
            command = command.substring( 0, atIndex );
        }

        try {
            Socket s = new Socket( host, 79 );
            PrintWriter out = new PrintWriter(s.getOutputStream(), true);
            BufferedReader in = new BufferedReader( 
                                new InputStreamReader(s.getInputStream()));

            boolean more = true;

            // Send the 'finger command' to the remote side.
            out.println( command );

            // For as long as the other side shoves data at us, print it.
            while( more ) {
                String line = in.readLine();
                if( line == null ) {
                    more = false;
                }
                else {
                    System.out.println( line );
                }
            }

            // Be a good little application and close our streams
            out.close();
            in.close();
            s.close();
        }
        catch( UnknownHostException e) {
            System.out.println( "Finger: Invalid Machine Name (" + 
                                 args[0] + ")" );
        }
        catch( IOException e ) {
            System.out.println( "Finger: " + e );
        }
    }
}