import ifi.math.function.DiscreteFunction;

import java.applet.Applet;

import java.awt.*;
import java.awt.event.*;


/*
 * Applet which tests the PlotArea class.
 */

public class SimpleGraphApplet extends Applet implements KeyListener, ItemListener{
  // Range

  double start = 0.1;
  double stop  = 6.28;

  // GUI elements

  PlotArea plotarea = new PlotArea();
  Choice function_menu = new Choice();
  TextField start_prompt = new TextField(8);
  TextField stop_prompt  = new TextField(8);
  TextField arb_func  = new TextField(30);
  TextArea result_area = new TextArea("", 4, 30, TextArea.SCROLLBARS_VERTICAL_ONLY);

  /*
   * The init method builds the user interface. It is also responsible
   * for initializing the sampled functions.
   */

  public void init(){
    // BorderLayout is a good choice of LayoutManager for this
    // applet. We use the CENTER panel to hold the PlotArea, and the
    // the NORTH panel to hold the other components.

    setLayout(new BorderLayout());

    Panel north = new Panel();
    north.setLayout(new GridLayout(2, 3));
    add(north, BorderLayout.NORTH);

    north.add(new Label("Choose function: "));
    function_menu.add("Arbitrary function");
    function_menu.add("sin(x)");
    function_menu.add("cos(x)");
    function_menu.add("tan(x)");
    function_menu.add("atn(x)");
    function_menu.add("exp(x)");
    function_menu.add("log(x)");
    function_menu.add("sqrt(x)");
    function_menu.add("abs(x)");
    function_menu.select(1);

    north.add(function_menu);
    function_menu.addItemListener(this);

    north.add(new Label(" Function: "));
    north.add(arb_func);
    arb_func.addKeyListener(this);

    north.add(new Label(" start ="));
    start_prompt.setText("0.1");
    start_prompt.addKeyListener(this);
    north.add(start_prompt);

    north.add(new Label(" stop ="));
    stop_prompt.setText("6.28");
    stop_prompt.addKeyListener(this);
    north.add(stop_prompt);

    result_area.setEditable(false);
    add(result_area, BorderLayout.SOUTH);

    add(plotarea, BorderLayout.CENTER);


    // Calculate default function

    reComputeFunction();
  }

  public void keyPressed(KeyEvent event) {}
  public void keyTyped(KeyEvent event) {}

  public void keyReleased(KeyEvent event){
    // Check that the key-press came from the start_prompt,
    // and that the user pressed the enter key.

    if(event.getComponent() == start_prompt && event.getKeyCode() == KeyEvent.VK_ENTER){
      // Get start value from the prompt and recompute the function.
      try{
	start = Double.valueOf(start_prompt.getText()).doubleValue();
      }catch(Exception e){
	result_area.append("Illigal input in start_prompt!\n" + 
			   "  Please enter a valid number.\n\n");
	start_prompt.setText("0.1");
	return;
      }
      reComputeFunction();

    }else if(event.getComponent() == stop_prompt && event.getKeyCode() == KeyEvent.VK_ENTER){
      // Get stop value from the prompt and recompute the function.
      try{
	stop = Double.valueOf(stop_prompt.getText()).doubleValue();
      }catch(Exception e){
	result_area.append("Illigal input in stop_prompt!\n" + 
			   "  Please enter a valid number.\n\n");
	stop_prompt.setText("0.1");
	return;
      }
      reComputeFunction();
    }else if(event.getComponent() == arb_func && event.getKeyCode() == KeyEvent.VK_ENTER)
      reComputeFunction();
  }

  public void reComputeFunction(){

    //Fixed for simplisity, but could use:  = getSize().width - 120;
    int no_samples = 201;

    DiscreteFunction f = new DiscreteFunction(no_samples);
    double x, y, delta = (stop - start) / (no_samples - 1);

    // Get function type
    String function;
    if(function_menu.getSelectedIndex() == 0)
      function = arb_func.getText();
    else
      function = function_menu.getSelectedItem();

    //I use my Interpreter class
    try{
      function = Interpreter.parse(function);
    }catch(Exception e){
      result_area.append("Interpreter Exception: " + e.getMessage() + "\n");
      return;
    }

    // Compute y=F(x) for all samples
    for(int i = 0; i < no_samples; i++){
      x = start + i * delta;

      try{
	y = Interpreter.eval(function, x);
      }catch(Exception e){
	y = 0;
      }

      f.setX(i, x);
      f.setY(i, y);
    }

    // Substitute old plot with new.
    plotarea.removeAllFunctions();
    plotarea.addFunction(f);
    plotarea.repaint();
  }

  //Recompute when a different function is selected.
  public void itemStateChanged(ItemEvent e){
    reComputeFunction();
  }
}