/**
Calculator.java
a simple Calculator applet
@author	Jay Tomlin
@version	1.0
http://ezinfo.ucs.indiana.edu/~ltomlin/
Bloomington, Indiana, USA
December 1996
*/


import java.applet.*;
import java.awt.*;

public class Calculator extends Applet {

//
// Declare the class variables
//

double x, y;
Button Zero, One, Two, Three, Four, Five, Six, Seven, Eight, Nine;
Button Plus, Minus, Times, DividedBy, Sin, Cos, Tan, Log, Exp, Ran;
Button Clear, ClearEntry, Decimal, Equals;
Panel ButtonPanel, DisplayPanel;
TextField Display;
GridLayout grid1, grid2;
BorderLayout border;
boolean HasDecimal, ReplaceDisplay;
String CurrentFunction, FirstNumber;


public void init() {

	//
	// Size it to a nice Golden-ratio proportion
	//

	resize(120,174);
	
	//
	// Create the component objects
	//

	Display = new TextField(); // left blank so it stretches to fill panel
	Display.setEditable(false);  
	
	Zero = new Button("0");
	One = new Button("1");
	Two = new Button("2");
	Three = new Button("3");
	Four = new Button("4");
	Five = new Button("5");
	Six = new Button("6");
	Seven = new Button("7");
	Eight = new Button("8");
	Nine = new Button("9");
	Plus = new Button("+");
	Minus = new Button("-");
	Times = new Button("*");
	DividedBy = new Button("/");
	Sin = new Button("sin");
	Cos = new Button("cos");
	Tan = new Button("tan");
	Log = new Button("ln");
	Exp = new Button("e");
	Ran = new Button("ran");
	Clear = new Button("C");
	ClearEntry = new Button("CE");
	Decimal = new Button(".");
	Equals = new Button("=");
	
	
	ButtonPanel = new Panel();
	DisplayPanel = new Panel();

	//
	// 24 buttons go on a 6x4 grid
	//

	grid1 = new GridLayout(6, 4);
	ButtonPanel.setLayout(grid1);
	
	
	// and the Display gets a Panel of its own
	
	grid2 = new GridLayout(1, 1);
	DisplayPanel.setLayout(grid2);


	//
	// Add the elements to their respective Panels
	//
	
	DisplayPanel.add(Display);

	ButtonPanel.add(Ran);	
	ButtonPanel.add(Exp);	
	ButtonPanel.add(Log);	
	ButtonPanel.add(Clear);	
	ButtonPanel.add(Sin);	
	ButtonPanel.add(Cos);	
	ButtonPanel.add(Tan);	
	ButtonPanel.add(ClearEntry);	
	ButtonPanel.add(Seven);	
	ButtonPanel.add(Eight);	
	ButtonPanel.add(Nine);	
	ButtonPanel.add(DividedBy);	
	ButtonPanel.add(Four);	
	ButtonPanel.add(Five);	
	ButtonPanel.add(Six);	
	ButtonPanel.add(Times);	
	ButtonPanel.add(One);	
	ButtonPanel.add(Two);	
	ButtonPanel.add(Three);	
	ButtonPanel.add(Minus);	
	ButtonPanel.add(Zero);	
	ButtonPanel.add(Decimal);	
	ButtonPanel.add(Equals);	
	ButtonPanel.add(Plus);	

	//
	// Finally, add and show the Panels
	//
	
	border = new BorderLayout();
	this.setLayout(border);
	this.add("North", DisplayPanel);
	this.add("Center", ButtonPanel);
	this.show();

	}


public void start() {

	ReplaceDisplay = true;
	FirstNumber = "0";
	CurrentFunction = "nothing";
	HasDecimal = false;
	Display.setText("0");
	x = 0; y = 0;
	
	}
	
//	
// Handle user clicks.
// Choices are: it was a number, it was a unary operator, 
// or it was a binary operator
//	
	
public boolean handleEvent(Event e) { 

	switch(e.id) {
		case Event.ACTION_EVENT : {	// button clicks fall into this category
			if (e.target == Zero) numberClicked((String)e.arg);
			if (e.target == One) numberClicked((String)e.arg);
			if (e.target == Two) numberClicked((String)e.arg);
			if (e.target == Three) numberClicked((String)e.arg);
			if (e.target == Four) numberClicked((String)e.arg);
			if (e.target == Five) numberClicked((String)e.arg);
			if (e.target == Six) numberClicked((String)e.arg);
			if (e.target == Seven) numberClicked((String)e.arg);
			if (e.target == Eight) numberClicked((String)e.arg);
			if (e.target == Nine) numberClicked((String)e.arg);
			if (e.target == Decimal) {if(HasDecimal) {;} //do nothing 
				else {	HasDecimal = true;
					numberClicked((String)e.arg);}}
			
			if (e.target == Plus) binaryFunctionClicked((String)e.arg);
			if (e.target == Minus) binaryFunctionClicked((String)e.arg);
			if (e.target == Times) binaryFunctionClicked((String)e.arg);
			if (e.target == DividedBy) binaryFunctionClicked((String)e.arg);
			if (e.target == Sin) unaryFunctionClicked((String)e.arg);
			if (e.target == Cos) unaryFunctionClicked((String)e.arg);
			if (e.target == Tan) unaryFunctionClicked((String)e.arg);
			if (e.target == Log) unaryFunctionClicked((String)e.arg);
			if (e.target == Exp) unaryFunctionClicked((String)e.arg);
			if (e.target == Ran) unaryFunctionClicked((String)e.arg);
			if (e.target == Clear) unaryFunctionClicked((String)e.arg);
			if (e.target == ClearEntry) {	Display.setText("0");
							HasDecimal = false;
							ReplaceDisplay = true; }
			if (e.target == Equals) { 
				
				String SecondNumber = new String(Display.getText());
				equalsClicked(FirstNumber, CurrentFunction, SecondNumber); }
			
			}	// ends case Event.ACTION_EVENT
		default: 
	
		} // ends switch(e.id)

	return true;
	} // ends handleEvent()
	
	
public void numberClicked(String argument) {

	String currentNumber = Display.getText();
	if(ReplaceDisplay) { 		
	  if(argument.equals(".")) { Display.setText("0.");}
	    else { Display.setText(argument); } // ends if(argument.equals(".")
	ReplaceDisplay = false; } 
	  else { Display.setText(currentNumber + argument); } // ends if(ReplaceDisplay)
	
	} // ends numberClicked()


public void unaryFunctionClicked(String argument) {
	
	String currentDisplay = Display.getText();
	try {
		Double X = new Double(currentDisplay);
		x = X.doubleValue();
	} catch (NumberFormatException e) {
	
		x = 0;
	}
	
	
	if (argument.equals("sin")) y = Math.sin(x); 
	if (argument.equals("cos")) y = Math.cos(x); 
	if (argument.equals("tan")) y = Math.tan(x); 
	if (argument.equals("ln")) y = Math.log(x); 
	if (argument.equals("e")) y = Math.exp(x); 
	if (argument.equals("ran")) y = Math.random(); 
	if (argument.equals("C")) { 	x = 0; y = 0; 
					HasDecimal = false;
					FirstNumber = "0";
					CurrentFunction = "nothing";
					ReplaceDisplay = true; }
	
	Double Answer = new Double(y);
	Display.setText(Answer.toString());
	ReplaceDisplay = true;
	HasDecimal = false;

	} // ends unaryFunctionClicked
	
public void binaryFunctionClicked(String argument) {

	equalsClicked(FirstNumber, CurrentFunction, Display.getText());
	CurrentFunction = argument;
	ReplaceDisplay = true;

	} // ends binaryFunctionClicked

public void equalsClicked(String numberOne, String function, String numberTwo) {

	try {
		Double X = new Double(numberOne);
		x = X.doubleValue();
		} catch (NumberFormatException e) {
	
			x = 0;
		}
	
	try {
		Double Y = new Double(numberTwo);
		y = Y.doubleValue();
		} catch (NumberFormatException e) {
	
			y = 0;
		}

	// Now x and y should be valid doubles, ready for x + y and the like.
		
	double z = 0; // the result
	if (function.equals("+")) z = x + y;
	if (function.equals("-")) z = x - y;
	if (function.equals("*")) z = x * y;
	if (function.equals("/")) z = x / y;
	if (function.equals("nothing")) z = y;
	
	Double Answer = new Double(z);
	Display.setText(Answer.toString());
	FirstNumber = Answer.toString();
	ReplaceDisplay = true;
	HasDecimal = false;
	CurrentFunction = "nothing";

	} // ends equalsClicked 

} // ends class Calculator