/** 
  * Iterated Difference Equation Demonstrator Applet
  * @author Robert J Morton
  * @version 27 November 1997 
  * @modified 07 August 2009, 18 April 2012 
  * Converted to a JFramed application  Mon 20 Feb 2017 */

/* Open a terminal and change directory to where this file is loacated.
   To compile this program, enter the terminal command: javac difeqn.java
   To run this program, enter the terminal command: java difeqn */

import javax.swing.*;
import java.awt.Dimension;  // to be able to set the preferred JFrame size
import java.awt.Color;      // to be able to set JFrame background colour

public class difeqn extends JFrame {

  private int  // Integer values which are private to this class
    XE = 570,  // Horizontal extent of window and JFrame. 545
    YE = 415;  // Vertical extent of window and JFrame.   365

  private static String[] 
    SW = {"-en","-pt"},
    Title = {
      "Iterated Difference Equation Demonstrator",
      "Demonstrador de Equações de Diferença Iteradas"
    };

  private static int ls = 0;

  /* Declare a reference to an instance of the child class.Beware:
  an instance of the child class cannot be created here because
  this must be done within the invokeAndWait environment. */
  private difeqnap LG; 

  public difeqn() {    // construct an instance of this extended JFrame
    super(Title[ls]);  // set window frame title on title bar

    /* Set up the window listener to listen for the window close command which
    occurs when the user clicks on the X control in the window's title bar.*/
    setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

    /* Set the initial size of the extended JFrame. This is the area INSIDE 
    the frame. It does not include the border or the title bar areas. */
    setPreferredSize(new Dimension(XE, YE));

    setBounds(0,0,XE,YE);          // of area inside window frame
    setBackground(Color.black);    // default background colour of JFrame
    LG = new difeqnap(XE,YE, ls);  // Create new instance of difeqn class
    getContentPane().add(LG);      // add it to the extended JFrame's pane.
    pack();                        // automatically packs to fill JFrame
    setVisible(true);              // make this extended JFrame visible
  }


  public static void main(final String[] args) {

    if(argsValid(args)) {

      /* Initiate the creation of a new instance of this extended
      JFrame and then wait until the building process has completely
      finished before giving the new instance of the child class
      permission to commence running. */

      try {
        javax.swing.SwingUtilities.invokeAndWait(
          new Runnable() {public void run() {new difeqn();}}
        );
      } catch(Exception e) {
        System.out.println("Couldn't create Swing GUI.");
        System.out.println("There's probably an error in the constructor");
        System.out.println("code of one of this class's child classes.");
        System.out.println(e);
        System.out.println(e.getCause());
      }

      /* The above try-catch sequence is necessary for the following reason. 
      The statement "new difeqn();" is a request to Swing to create a GUI
      instance of this application. It includes, in effect, all the state-
      ments in the constructor methods of all this class's child classes.
      All these requests are made on this, the main() program thread. 

      However, these requests are carried out [ie the actual constructing is 
      done] by the underlying Swing system on the Event Despatching Thread. 
      The constructing process necessarily takes longer to do than the mere
      task of REQUESTING that the constructing be done. This means that the
      main() thread will set the run() thread in motion before the GUI has 
      finished being constructed. Hence trouble.

      The solution is to force the main() thread to withhold permission for 
      the run() thread to start its job until the Event Despatching Thread 
      has completely finished constructing the GUI. */

      /* NOTE: This class inherits a paint() method from the JFrame class
      that it extends. This method automatically calls the paint() method
      of the child [extended JPanel] class when necessary. */

    }  // end of if(argsValid)
  }    // end of main()


  private static boolean argsValid(String[] args) {
    int L = args.length;     // number of command-line arguments
    if(L == 0) return true;  // if command line has no arguments
    String s = args[0];      // the first command line argument

    if(s.indexOf("help") != -1) {
      System.out.println("This program accepts command line arguments to");
      System.out.println("set the annotation language of the application:");
      System.out.println("-en = show annotations in English.");
      System.out.println("-pt = mostre anotações no português.");
      return false;
    }
    if(s.equals("-pt")) ls = 1;  // window title in Portuguese
    return true;
  }

}  // end of difeqn class