import javax.swing.*;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.Rectangle;
import edu.jsu.leathrum.mathlets.shared.*;

public class DerivCalc extends AMathlet {

class MenuGroup extends JPanel implements ActionListener, FieldHandler {

  MLabel l = new MLabel("variable:");
  JPopupMenu m = new JPopupMenu();
  JMenuItem j = null;
  JButton b = new JButton("  ");
  String[] labels = {"","x","y","z", "r", "s", "t", "u", "v"};
  int i=0;
  Box b1 = new Box(BoxLayout.X_AXIS);

  MenuGroup() {
    setLayout(new FlowLayout());
    add(l);
    add(b);
    setOpaque(false);
    b.setOpaque(false);
    b.addActionListener(this);
    m.setBackground(Color.white);
  }
  
  public void initmenu() {
    l.setText(AMathlet.getProperty("DerivCalc.variable"));
    for (i=1; i<labels.length; i++) {
      j = new JMenuItem(AMathlet.getProperty("DerivCalc."+labels[i]));
      j.setOpaque(false);
      m.add(j);
      j.addActionListener(this);
    }  
  }
  
  private int index = 0;
  private int defindex = 0;
  
  private void setFromIndex() {
    if (index == 0) b.setText("  ");
    else b.setText(AMathlet.getProperty("DerivCalc."+labels[index]));
  }

  public void actionPerformed(ActionEvent e) {
    if (e.getSource() == b) {
      m.pack();
      Rectangle brect = b.getBounds();
      m.show(this,brect.x,brect.y+brect.height);
    }
    else { 
      for (i=1; i<labels.length; i++)
        if (((JMenuItem) e.getSource()).getText().compareTo(AMathlet.getProperty("DerivCalc."+labels[i]))==0)
          index = i;
      setFromIndex();
    }
  }

  public void setDefault(String dval) {
    for (i=0; i<labels.length; i++) 
      if (dval.compareTo(labels[i])==0) 
        defindex = i;
  }

  public void setToDefault() {
    index = defindex;
    setFromIndex();
  }

  public void setField(String val) {
    for (i=0; i<labels.length; i++) 
      if (val.compareTo(labels[i])==0) 
        index = i;
    setFromIndex();
  }

  public String getField() {
    return labels[index];
  }
}

  TParserInputSet inputField = new TParserInputSet("",50);
  FixedWidthLabel answer = new FixedWidthLabel(400);
  MenuGroup mg = new MenuGroup();
  JButton compButton = new JButton("compute");
  JButton appButton = new JButton("apply");
  JButton clearButton = new JButton("clear");
  Box b1, b2;

  public DerivCalc() {
    this.getContentPane().setBackground(Color.white);
    this.getContentPane().setLayout(new FlowLayout());
    b1 = new Box(BoxLayout.Y_AXIS);

    b1.add(inputField);
    
    b2 = new Box(BoxLayout.X_AXIS);
    b2.add(Box.createHorizontalGlue());
    b2.add(Box.createVerticalStrut(20));
    b2.add(answer);
    b2.add(Box.createHorizontalGlue());
    b1.add(b2);

    b2 = new Box(BoxLayout.X_AXIS);
    b2.add(Box.createHorizontalGlue());
    b2.add(compButton);
    compButton.setOpaque(false);
    b2.add(appButton);
    appButton.setOpaque(false);
    b2.add(mg);
    b2.add(clearButton);
    clearButton.setOpaque(false);
    b2.add(Box.createHorizontalGlue());

    b1.add(b2);
    this.getContentPane().add(b1);
  }
  
  class ApplyAction implements ActionWrapper {
    public void doThis() {
      String ss = inputField.getInput();
      inputField.setInputText("D"+mg.getField()+"["+ss+"]");
      inputField.setDirty();
    }
  }

  public void localinit() {
    registerInputSet(inputField);
    registerGraphButton(compButton);
    compButton.setText(AMathlet.getProperty("compute")); // overrides "Graph"
    // also need to register appButton with action
    registerButtonAction(appButton, new ApplyAction());
    appButton.setText(AMathlet.getProperty("apply"));
    registerClearButton(clearButton);
    setHandler("expr",inputField);
    mg.initmenu();
    setHandler("var",mg);
  }

  public void draw() {
    if (inputField.getInput().compareTo("") == 0) {
      inputField.setInputText("");
      inputField.setDirty();
      answer.setText("");
    }
    else {
      String s = inputField.evaluatef();
      if (s != "") {
        inputField.setInputText(s);
        inputField.setDirty();
      }
      answer.setText(inputField.getMsgString());
    }
  }

  public void localclear() {
    draw();
  }
}