import java.awt.*;
import java.awt.event.*;

/**
 * QueryClient.java runs MPE program via Telnet and provides GUI front-end.
 *
 * This is a quick & dirty prototype, but it helps to "get the idea".
 *
 * It uses the Java Telnet implementation from the Java Telnet Applet
 * available at "http://www.first.gmd.de/persons/leo/java/Telnet".
 */
class QueryClient {

  /*
   * The host connectivity.
   */
  static HostIO host;

  /*
   * The GUI I/O elements.
   */
  static Choice ch;
  static TextField tf;
  static List ls;

  /**
   * Main program opens telnet connection to host, logs on and launches the
   * MPE program to be interacted with, opens GUI window for the user and
   * then translates user actions to appropriate transactions with the host
   * application.
   */
  public static void main(String[] args) throws Exception {

    // Lots of hardcoded stuff to keep the example simple and short. There
    // should also be a better error handling and more resilient parsing of
    // host responses in a "real world" version.

    host = new HostIO();

    host.open("my3000.grc.hp.com");

    host.answerTo(
      "MPE/iX:", "hello java,user.test/pw ;info='run query.pub.sys' ;parm=1"
    );
    host.answerTo(">", "base=music");
    host.answerTo("PASSWORD = >>", ";");
    host.answerTo("MODE = >>", "5");
    host.answerTo(">", "set=composers");
    
    Frame fr = new Frame("Remote MPE Invocation");
    fr.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        exitProgram();
      }
    });
    fr.setLayout(new BorderLayout());
    
    ch = new Choice();
    ch.add("Find composer starting with...");
    ch.add("Find composer containing...");

    tf = new TextField(20);
    tf.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        performQuery();
      }
    });

    Panel pn = new Panel();
    pn.add(ch);
    pn.add(tf);

    ls = new List(5);

    fr.add(pn, "North");
    fr.add(ls, "Center");

    fr.pack(); fr.setVisible(true);
  }

  /**
   * Exit host application when user closes window.
   */
  static void exitProgram() {
    host.answerTo(">", "exit");
    host.skipUntilStartsWith("CPU=");
    try { host.close(); } catch (Exception e) { /* ignore */ };
    System.exit(0);
  }

  /**
   * Perform host transaction depending on query type selected by user
   */
  static void performQuery() {
    switch (ch.getSelectedIndex()) {
      case 0:
        performFindAndReport(
          "find composername matching \"" + tf.getText() + "?*\""
        );
        break;
      case 1:
        performFindAndReport(
          "find composername matching \"?*" + tf.getText() + "?*\""
        );
        break;
    }
  }

  /**
   * Trigger QUERY FIND and parse resulting REPORT, if entries are found
   */
  static void performFindAndReport(String findCmd) {
    ls.removeAll();  // empty result in gui
    host.answerTo(">", findCmd);
    host.skipUntilEndsWith("ENTRIES QUALIFIED");
    if (! host.getLine().startsWith("0 ")) {
      host.answerTo(">", "report d,composername,16; d,birthplace,58; end");
      host.skipLines(1+9);  // 1x echo plus 9x heading
      while (! host.readln().equals(">")) {
        ls.add(host.getLine());  // add item to gui
      }
      host.pushBack();  // for next skip-to-prompt
    }
  }
}