/**
  * Text entry field and + - adjustment buttons for 'c' for CtrlPanl.class
    re DifEqnAp.class
  * @author Robert John Morton UK-YE572246C
  * @version 27 November 1997 modified 07 August 2009, 18 April 2012 */

/*  This class contains a text entry field in which the user may enter a new 
    value for the constant c in the currently selected difference equation. 
    It also contains two buttons + and - for incrementing and decrementing 
    the current value of the constant c in the selected difference equation.*/

import java.awt.*;        // for graphics operations (GUI)
import java.awt.event.*;  // for the new-fangled 1.1 event handling
import javax.swing.*;     // library for constructing Swing GUI


public class cval extends JPanel {
  private setbutt sb;       // instance reference to Start/Stop/Reset panel
  private formula F;        // instance reference to the formula class
  private JLabel L;         // label for the text field
  private JTextField t;     // text field to hold and set c
  private JButton a, b;     // 2 button id's and references
  private double c = 3.68;  // value for access by main panel

  private static final double 
    D[] = {+0.1, -0.1};  // increment/decrement amounts

  private boolean EqnFlag = false;  // which equation is in force


  cval(setbutt sb, formula F, Color pc) {
    this.sb = sb;       // instance ref of setbutt panel to local variable
    this.F = F;         // instance ref of formula class to local variable
    setLayout(null);    // NOTE: this panel is 100 by 50 pixels
    setBackground(pc);  // set panel colour

    /* Create an instance of the panel's title label, add it to this
    panel, then set its position within the panel and its size. */

    L = new JLabel("Adjust c"); add(L); L.setBounds(0, 0, 70, 25);

    /* Create an instance of the '+' button, label it, add it to this
    panel, set its position within the panel and its size, set button's
    annotation margins to minimum and create a listener to detect when
    it has been pressed. */

    a = new JButton(); a.setText("+"); add(a); a.setBounds(95, 0, 30, 24);
    a.setMargin(new Insets(3,3,3,3)); a.addActionListener(new cbut(0,this));

    /* Create an instance of the '-' button, label it, add it to this
    panel, set its position within the panel and its size, set button's
    annotation margins to minimum and create a listener to detect when
    it has been pressed. */

    b = new JButton(); b.setText("-"); add(b); b.setBounds(95, 27, 30, 24);
    b.setMargin(new Insets(3,3,3,3)); b.addActionListener(new cbut(1,this));

    /* Create an instance of text entry field, add it to this panel,
    set its position within the panel and its size, create and set a
    font for its text and create a listener to detect when a carriage-
    return has been entered. */

    t = new JTextField(); add(t); t.setBounds(0, 25, 90, 25);
    t.setFont(new Font("Sans", Font.BOLD, 14));
    t.addActionListener(new cbut(3, this));

    // display the initial value of c in the text field
    t.setText(String.valueOf(c));
  }


  void setEF(boolean b) {EqnFlag = b;}   //set which equation is to be used


  void initCval() {  // TO SET c DEFAULT VALUES [also called by seleqn]
    if(EqnFlag)      // if using x = x**2 + c
      c = -1.5;      // set appropriate default value for c
    else             // else x = cx(1 - x) is in use 
      c = +3.68;     // set appropriate default value for c
    ShowReset();     // see below
  }


  private void CheckLimits() {  // ENSURE c IS WITHIN GRAPH LIMITS
    if(EqnFlag) {               // if using x = x**2 + c
      if(c > +2.5) c = +2.5;    // set appropriate limits for c
      if(c < -2.5) c = -2.5;
    } else {                    // else if using x = cx(1 - x)
      if(c > 4.1) c =  4.1;     // set appropriate limits for c
      if(c < 0.1) c = .1;
    }
    ShowReset();                // see below
  }


  private void ShowReset() {       // for local code economy
    F.setC(c);                     // update the c-value in the formula class
    String s = String.valueOf(c);  // convert c-value to string

    /* If string is more than 9 characters,
    chop its end off after the 9th character. */

    if(s.length() > 9) s = s.substring(0,9);

    t.setText(s);  // display c in the text field
    sb.reset();    // 'hit' the reset button
  }


  /* EVENT HANDLERS ONLY CALLED BY THE LISTENER CLASS BELOW
  Add the increment to current value of 'c' and ensure that
  it is still within the limits of the graph. */

  void incC(int i) { c += D[i]; CheckLimits(); }


  void setC() {    // SET THE VALUE OF 'C' THAT WAS TYPED INTO THE TEXT FIELD
    double x = c;  // preserve the original value of c

    /* Try to parse a number from the entered text by creating a Double
    Double object of the numeric value of the string in the text field
    then extracting its value as an ordinary double. */

    try { c = Double.valueOf(t.getText()).doubleValue(); }

    /* If a valid number cannot be parsed from the text currently con-
    tained in the field, put the original value of c back in text field. */

    catch(NumberFormatException f) { c = x; }

    CheckLimits();  // ensure entered value was within limits
  }
}


// LISTENS FOR THE + - BUTTONS & C/R FROM TEXT FIELD
class cbut implements ActionListener {
  int id;   // one of the above events
  cval cv;  // the application that called: always the above class

  /* Constructor for a new checkbox event: sets 'id' number of
  the event type and the reference to the instance of the above
  class from which it came. (there will only be one instance). */

  public cbut(int id, cval cv) { this.id = id; this.cv = cv; }

  // a checkbox event has occurred from checkbox 'id'
  public void actionPerformed(ActionEvent e) {
    switch(id) {
       case 0: cv.incC(0); break;  // + button pressed
       case 1: cv.incC(1); break;  // - button pressed
       case 2: cv.setC();  break;  // C/R from text field
    }
  }
}