/* Copyright 2000 Charles G. Wright
 * This software may be distributed under the terms of the
 * GNU General Public License.
 *
 * $Id: InputField.java,v 1.1 2000-06-15 10:14:59-05 chuckles Exp chuckles $
 */

import java.math.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;

/** A suped up text field, containing a label, a text box
 * increment and decrement buttons, and a unit label.
 * Includes a UnitConverter, and handles conversions
 * to/from metric automatically.*/

public class InputField extends Panel implements ActionListener, Observer {
  private double increment;
  private UnitConverter uc;
  private java.awt.Label name;
  private java.awt.Label label;
  private TextField tf;
  private double value;
  private ActionListener parent;
  private ActionEvent ae;

  private Button bleft;
  private Button bright;

  String text_value;

  /** <p>Create an InputField. Arguments are
  * <ul><li>unitType - the type of unit being specified in the
  * input, as defined in class UnitConverter.
  * <li>increment - the amount that the field will be incremented or
  * decremented when these respective buttons are clicked.*/

  public InputField(int unitType, double initialValue, double increment){
    setLayout(new FlowLayout(FlowLayout.LEFT, 2, 2));
    // not used yet...
    this.increment = increment;
    uc = new UnitConverter(unitType);
    uc.addObserver(this);
    value = initialValue;
    text_value = Double.toString(uc.getConvertedValue(initialValue));
    name = new Label(uc.getName());	      
    add(name);
    bleft = new Button("<");
    bleft.addActionListener(this);
    add(bleft);
    bright = new Button(">");
    bright.addActionListener(this);
    add(bright);
    tf = new TextField(text_value, 6);
    tf.addActionListener(this);
    add(tf);
    label = new Label(uc.getLabel());
    add(label);

    ae = new ActionEvent(this, 0, uc.getName());
  }
  
  public void setNameText(String text){
    name.setText(text);
  }

  public void setLabelText(String text){
    label.setText(text);
  }

  public double getValue(){
    return(uc.getMetricValue(Double.valueOf(tf.getText()).doubleValue()));
  }

  /** Called as a result of the unit system being
   * changed. This object is added as an Observer of the
   * UnitConverter object contained herein. It will call
   * this update() method when the unit system changes. */

  public void update(Observable obs, Object arg){
    System.out.println("updating units in InputField object");
    setLabelText(uc.getLabel());
    tf.setText(Double.toString(uc.getConvertedValue(value)));
  }

  // This method is called after this object is created,
  // to register the object that provides the actionPerformed()
  // method. I might have just passed "parent" in the
  // constructor, but this gives the flexibility to
  // put the event handler elsewhere, such as in a
  // central event handler object.
  // Also, this should handle multiple action listeners
  // instead of just one, but...

  public void addActionListener(ActionListener parent){
    this.parent = parent;
  }
   
  /** Here is where we come when the enter key is pressed in the text field. */
  public void actionPerformed(ActionEvent e){
    Object source = e.getSource();
    if (source == tf) {
      try{
	value = uc.getMetricValue(Double.valueOf(tf.getText()).doubleValue());

	// If we are here, the value is a valid number. Save the
	// String for next time, to restore in the case of a bad value.
	text_value = tf.getText();
	// Call action listener, to act on new value.
	parent.actionPerformed(ae);
      } catch (NumberFormatException nfe){
	// Restore last good value.
	// Should probably also flash error message...
	tf.setText(text_value);
      }
    } else if (source == bleft){
      value = uc.getConvertedValue(value - increment);
      text_value = Double.toString(value);
      tf.setText(text_value);
      parent.actionPerformed(ae);
    } else if (source == bright){
      value = uc.getConvertedValue(value + increment);
      text_value = Double.toString(value);
      tf.setText(text_value);
      parent.actionPerformed(ae);
    }
  }
}