package G4ip;

import java.applet.*;

import java.awt.*;

import G4ip.Sequent.*;

import G4ip.Prover.*;

import G4ip.Parser.*;

/** The applet for the prover.

  * @author      Christian Urban

  */

public class ProverApplet extends Applet {

  Prover prover;

  Parser parser;

  Button start;           

  Button clear;           

  Button next;            

  Button stop;           

  TextField lhs_text;     // place for the program formulae

  TextField rhs_text;     // place for the goal formula

  /** A field for various messages (e.g. error messages).

    */

  public Label messages;  // to be verbose   

  public void init() {

    setLayout(new BorderLayout());

    // NORTH

    Panel textfields = new Panel();

    add("North", textfields);

       // the parameters LHS_size and RHS_size are given in the html-file

    int LHS_size = Integer.parseInt(this.getParameter("LHS_size"));

    int RHS_size = Integer.parseInt(this.getParameter("RHS_size"));

    lhs_text = new TextField(LHS_size);    // program textfield

    rhs_text = new TextField(RHS_size);    // goal textfield

    Label separation = new Label("=>");    // for separation

    if (LHS_size > 0) {     // if someone prefears only single side sequents 

    textfields.add(lhs_text);   }         

    textfields.add(separation);

    textfields.add(rhs_text);

    // CENTER

    Panel buttonfield = new Panel();

    add("Center", buttonfield);

    start = new Button("Start");         

    clear = new Button("Clear");         

    next  = new Button("Next");          

    stop  = new Button("Stop");            

    switch_into_input_mode();   // start in input mode

    buttonfield.add(start);

    buttonfield.add(clear);

    buttonfield.add(next);

    buttonfield.add(stop);

    // SOUTH

    messages = new Label("");   // for any kind of message

    messages.setAlignment(Label.CENTER);

    add("South",messages);

  }

  /** When start is pressed; 

    * start and clear button are disabled;

    * next and stop button are enabled. 

    */

  public void switch_into_prove_mode() { 

      start.disable();    next.enable();

      clear.disable();    stop.enable();

      repaint();

    }

  /** When start is pressed 

    * and (hopefully) when prover finishes. 

    */  

  public void switch_into_input_mode() { 

      start.enable();    next.disable(); 

      clear.enable();    stop.disable();

      repaint();

    }

  /** Initiates the parse and prove process. 

    */  

  void initiate_proving() {

      Sequent sequ;

      messages.setText(""); 

      messages.repaint();

      repaint(); 

      Parser rhs_parser = new Parser(rhs_text.getText());

      Parser lhs_parser = new Parser(lhs_text.getText());

      try {                          // try to parse the input 

	sequ = new Sequent(lhs_parser.parseFormulae(),

			   rhs_parser.parseFormula());

      }

      catch (Exception exc) {        // there was a parser exception 

	messages.setText(exc.getMessage()); 

	messages.repaint();

	repaint(); 

	return;                     // in case there was an exception

      }                             // don't run the following code

      System.out.println(sequ.G.internalString()); 

      switch_into_prove_mode();

      prover = new Prover(sequ,this);

      prover.start();

  }

  /** Forces the prover to dispose all open frames.

    */

  public void destroy() {  

    if (prover != null && prover.isAlive()) { 

      prover.stop(); 

      prover.finalize();

    }

  }

  /** The actions for the buttons:

    * this bit of code would be different in Java 1.1

    */

  public boolean action(Event e, Object arg) {

    // clear button has been pressed

    if (e.target == clear) {

      messages.setText(""); 

      lhs_text.setText("");

      rhs_text.setText(""); 

      messages.repaint();

      repaint(); 

    }

    // start button has been pressed

    if (e.target == start) {

      initiate_proving();

      return true; 

    }

    // stop button has been pressed

    if (e.target == stop) {

      switch_into_input_mode();

      if (prover != null && prover.isAlive()) { prover.stop();  }

      return true; 

    }

    // next button has been pressed

    if (e.target == next) {

      if (prover != null && prover.isAlive()) { prover.resume();} 

      return true; 

    }

    return false;

  }

}