/* locationSelector.java
   Paul Carlisle
   
   This is a control panel which allows the user to enter their latitude
   and longitude. Entry consists of selecting individual digits in the
   appropriate range (0-90 for latitude, 0-180 for longitude) and selecting
   the modifier field (N/S for latitude, E/W for longitude.
   
   Both measures are stored internally in radian measure. South latitude
   are negative, north are positive. Eastern longitudes are negative, western
   are positive.
*/

import java.awt.*;
import java.lang.*;

public class locationSelector extends Panel
{
   private int Width;
   private int Height;
   private double Latitude;
   private double Longitude;
   private Choice latHi;
   private Choice latLow;
   private Choice latHemi;
   private Choice longHi;
   private Choice longMid;
   private Choice longLow;
   private Choice longHemi;
   private GridBagLayout mainLayout;
   private GridBagConstraints mainConstraints;


   public locationSelector(int width, int height, double latitude, double longitude,
						   Font inputFont, Font labelFont)
   {
	  setFont(inputFont);
	  
	  // Various choice lists for the digits and modifiers.
	  latHi = new Choice();
	  latLow = new Choice();
	  latHemi = new Choice();
	  longHi = new Choice();
	  longMid = new Choice();
	  longLow = new Choice();
	  longHemi = new Choice();
	  
	  latHi.setBackground(Color.white);
	  latLow.setBackground(Color.white);
	  latHemi.setBackground(Color.white);
	  longHi.setBackground(Color.white);
	  longMid.setBackground(Color.white);
	  longLow.setBackground(Color.white);
	  longHemi.setBackground(Color.white);
	  
	  latHemi.addItem("N");
	  latHemi.addItem("S");
	  
	  longHemi.addItem("E");
	  longHemi.addItem("W");
	  
	  // Add the digits common to all elements.
	  for (int i = 0; i <= 8; i++)
	  {
		 latLow.addItem(new String(Integer.toString(i)) );
		 latHi.addItem(new String(Integer.toString(i)) );
		 longLow.addItem(new String(Integer.toString(i)) );
		 longMid.addItem(new String(Integer.toString(i)) );
	  }
	  
	  // Fill in the rest manually.
	  latHi.addItem("9");
	  latLow.addItem("9");
	  
	  longLow.addItem("9");
	  longMid.addItem("9");
	  
	  longHi.addItem("0");
	  longHi.addItem("1");
	  
	  mainLayout = new GridBagLayout();
	  mainConstraints = new GridBagConstraints();
	  
	  setLayout(mainLayout);
	  
	  mainConstraints.gridy = 0;
	  mainConstraints.fill = GridBagConstraints.BOTH;
	  mainConstraints.anchor = GridBagConstraints.CENTER;
	  
	  Panel pad = new Panel();
	  mainConstraints.gridx = 0;
	  mainLayout.setConstraints(pad, mainConstraints);
	  add(pad);
	  
	  /* Latitude selector */
	  mainConstraints.gridx = 1;
	  mainLayout.setConstraints(latHi, mainConstraints);
	  add(latHi);
	  
	  mainConstraints.gridx = 2;
	  mainLayout.setConstraints(latLow, mainConstraints);
	  add(latLow);
	  
	  Label degree = new Label(" ", Label.CENTER);
	  degree.setFont(labelFont);
	  mainConstraints.gridx = 3;
	  mainLayout.setConstraints(degree, mainConstraints);
	  add(degree);
	  
	  mainConstraints.gridx = 4;
	  mainLayout.setConstraints(latHemi, mainConstraints);
	  add(latHemi);
	  
	  /* Spacer */
	  Label space = new Label("         ");
	  mainConstraints.gridx = 5;
	  mainLayout.setConstraints(space, mainConstraints);
	  add(space);
	  
	  /* Longitude selector */
	  mainConstraints.gridx = 6;
	  mainLayout.setConstraints(longHi, mainConstraints);
	  add(longHi);
	  
	  mainConstraints.gridx = 7;
	  mainLayout.setConstraints(longMid, mainConstraints);
	  add(longMid);
	  
	  mainConstraints.gridx = 8;
	  mainLayout.setConstraints(longLow, mainConstraints);
	  add(longLow);
	  
	  Label degree2 = new Label(" ", Label.CENTER);
	  degree2.setFont(labelFont);
	  mainConstraints.gridx = 9;
	  mainLayout.setConstraints(degree2, mainConstraints);
	  add(degree2);
	  
	  mainConstraints.gridx = 10;
	  mainLayout.setConstraints(longHemi, mainConstraints);
	  add(longHemi);
   }   
   // Event handling.
   public boolean action(Event e, Object what)
   {
	  // If the user changed a latitude digit...
	  if ( (e.target == latHi) ||
		   (e.target == latLow) ||
		   (e.target == latHemi) )
	  {
		 double temp = 10 * latHi.getSelectedIndex() + 
					   latLow.getSelectedIndex();
		 if (latHemi.getSelectedItem() == "S")
			temp = -temp;
		 setLatitude(degreesToRadians(temp));
	  }
	  else if ( (e.target == longHi) ||
				(e.target == longMid) ||
				(e.target == longLow) ||
				(e.target == longHemi) )
	  {
		 double temp = 100 * longHi.getSelectedIndex() +
					   10 * longMid.getSelectedIndex() +
					   longLow.getSelectedIndex();
		 if (longHemi.getSelectedItem() == "E")
			temp = -temp;
		 
		 setLongitude(degreesToRadians(temp));
	  }
	  
	  // Consume all events.
	  return false;
   }   
   // Utility functions.
   private double degreesToRadians(double degrees)
   {
	  return Math.PI * degrees / 180;
   }   
   // Returns the latitude, in radians.
   public double getLatitude()
   {
	  return Latitude;
   }   
   // Returns the longitude, in radians.
   public double getLongitude()
   {
	  return Longitude;
   }   
   private double radiansToDegrees(double radians)
   {
	  return 180 * radians / Math.PI;
   }   
  // Sets the Latitude and display to the passed value.
  // The value is in radians; display is set in degrees. 
   public void setLatitude(double latitude)
   {
	  if (Math.abs(latitude) > Math.PI/2)
	  {
		 double temp = Math.PI/2;
		 if (latitude < 0)
			temp = -temp;
			
		 latitude = temp;
	  }
	  
	  // We make a small adjustment here, to take care of an apparent
	  // bug in Java's comparison routines.  
	  if (latitude < 0)
		 latitude = latitude - (1e-7);
	  else
		 latitude = latitude + (1e-7);
	  
	  Latitude = latitude;
	  
	  double degrees = radiansToDegrees(Latitude);
	  
	  // Set the display.
	  latHi.select((int)Math.abs(degrees) / 10);
	  latLow.select((int)Math.abs(degrees) % 10);
	  
	  if (Latitude < 0)
		 latHemi.select("S");
	  else
		 latHemi.select("N");
   }   
   // Sets the longitude and display to the passed value.
   // The value is in radians; the display is set in degrees.
   public void setLongitude(double longitude)
   {
	  if (Math.abs(longitude) > Math.PI)
	  {
		 double temp = Math.PI;
		 if (longitude < 0)
			temp = -temp;
			
		 longitude = temp;
	  }
	  
	  Longitude = longitude;
	  
	  longitude = Math.abs(Longitude);
	  
	  double degrees = radiansToDegrees(longitude);
	  
	  longHi.select( (int)degrees / 100 );
	  longMid.select( ((int)degrees / 10) % 10);
	  longLow.select( (int)degrees % 10);
	  
	  if (Longitude < 0)
		 longHemi.select("E");
	  else
		 longHemi.select("W");
   }   
}