//Calculator.java
//needs WindowDestroyer.java



import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.lang.Math;

/***********************
* Square Root: for some reason the unicode \u221A
* 	displays a lowercase v in the button no matter
*	how big, so I have used "sqrt" instead
*	This is the same for Pi
*
*
* MS, MR, and MC buttons are used
*
* +/- toggle button is used
*
*
*
*************************/


public class Calculator {
	public static void main(String[] args) {
		new CalculatorFrame().show();
   }
}//end Calculator


class CalculatorFrame extends JFrame {
   public CalculatorFrame() {
      	setTitle("Calculator");
      	setLocation(100, 100);
     	setSize(300, 300);
	addWindowListener(new WindowDestroyer());
      	JTextField display = new JTextField("0.0");
	display.setHorizontalAlignment(JTextField.RIGHT); 
	display.setBackground(Color.white);
      	display.setEditable(false);
      	getContentPane().add(display, "North");
      	getContentPane().add(new CalculatorPanel(display), "Center");
   }
}//end CalculatorFrame

class CalculatorPanel extends JPanel {

   	public CalculatorPanel(JTextField display) {
      		this.display = display;
      		setLayout(new GridLayout(5, 5));
		
		JButton MC = new JButton("MC");
		add(MC);
		MC.addActionListener(listener);

		JButton MR = new JButton("MR");
		add(MR);
		MR.addActionListener(listener);

		JButton MS = new JButton("MS");
		add(MS);
		MS.addActionListener(listener);

		JButton sqR = new JButton("sqrt");
		add(sqR);
		sqR.addActionListener(listener);

		JButton C = new JButton("C");
		add(C);
		C.addActionListener(listener);

		JButton Pi = new JButton("Pi");
		add(Pi);
		Pi.addActionListener(listener);

		String buttons = "789/";
      		for (int i = 0; i < buttons.length(); ++i) {
         		JButton b = new JButton(buttons.substring(i, i + 1));
         		add(b);
         		b.addActionListener(listener);
      		}

		JButton plsMin = new JButton("+/-");
		add(plsMin);
		plsMin.addActionListener(listener);

 		buttons = "456*";
      		for (int i = 0; i < buttons.length(); ++i) {
         		JButton b = new JButton(buttons.substring(i, i + 1));
         		add(b);
         		b.addActionListener(listener);
      		}


		JButton Bk = new JButton("Bk");
		add(Bk);
		Bk.addActionListener(listener);

 		buttons = "123-";
      		for (int i = 0; i < buttons.length(); ++i) {
         		JButton b = new JButton(buttons.substring(i, i + 1));
         		add(b);
         		b.addActionListener(listener);
      		}

		JButton none = new JButton("Exit");
		add(none);
		none.addActionListener(listener);

      		buttons = "0.+=";
      		for (int i = 0; i < buttons.length(); ++i) {
         		JButton b = new JButton(buttons.substring(i, i + 1));
         		add(b);
         		b.addActionListener(listener);
      		}


	}//end CalculatorPanel

/*************************
*	  
* End Display 
*
*************
*
* Start Operations 
*
***************************/

	private JTextField display;

	private ActionListener listener = new ActionListener() {

		public void actionPerformed(ActionEvent event) {
			

			String command = event.getActionCommand();
			
			if(command.equals("Bk")){
				background = true;
			}//end bk

			if(command.equals("Exit")){
				System.exit(0);
			}//end exit
			
			if(command.equals("C")){
				reset();
				display.setText("0.0");
			}//end clear

			if(command.equals("Pi")){
				display.setText("3.14");
				reg = 3.14;
				register = true;
			}//end Pi

			if(command.charAt(0) >= '0' && command.charAt(0) <= '9'){
				if(!start){
					display.setText(display.getText() + command);
				}else{
					display.setText(""+command);
					start = false;
					numbers = true;
				}
			}//end numbers

			if(command.equals(".")){
				if(!decimal){
					if(!start){
						display.setText(display.getText() + command);
						decimal = true;
					}else{
						display.setText("0"+command);
						decimal = true;
						start = false;
						numbers = true;
					}
				}
			}//end decimal

			if(command.equals("+")||command.equals("-")||
				command.equals("*")||command.equals("/")||
				command.equals("=")){
				if(operator&&numbers){
					start = true;
					decimal = false;
					numbers = false;
					calculate();
					op = command;
					operator = true;
					display.setText(""+reg);
				}else{		
					op = command;
					operator = true;			
					start = true;
					decimal = false;
					reg = Double.parseDouble(display.getText());
				}
			}//end operations


			if(command.equals("sqrt")){
				if(0>Double.parseDouble(display.getText())){
					display.setText("ERROR");
				}else{
					
display.setText(""+Math.sqrt(Double.parseDouble(display.getText())));
				}
			}//end square root


			if(command.equals("+/-")){
				if(0<Double.parseDouble(display.getText())){
					display.setText("-"+display.getText());
				}else if(0>Double.parseDouble(display.getText())){
					
display.setText(""+(Double.parseDouble(display.getText())*-1.0));
				}					
			}//end plus minus toggle


/****************************************
*Memory Functions
*	MS puts input field into memory
*	MR puts memory into input field
*	MC sets memory to 0.0
*
****************************************/


			if(command.equals("MS")){
				memory = Double.parseDouble(display.getText());
			}
			if(command.equals("MC")){
				memory = 0.0;
			}
			if(command.equals("MR")){
				display.setText(""+memory);
			}

		printSettings();
		}//end actionPerformed

		//To seperate the "operations" from the "calculations"
		private void calculate(){
			if(op.equals("+")){
				reg = reg + Double.parseDouble(display.getText());
			}else if(op.equals("-")){
				reg = reg - Double.parseDouble(display.getText());
			}else if(op.equals("*")){
				reg = reg * Double.parseDouble(display.getText());
			}else if(op.equals("/")){
				reg = reg / Double.parseDouble(display.getText());
			}else if(op.equals("=")){
				reg = Double.parseDouble(display.getText());
			}
		}
		//reset the flags and registers
		private void reset(){
			decimal = false;
			operator = false;
			register = false;
			start = true;
			numbers = false;
			op = "=";
			reg = 0.0;
		}

		//show the status on demand
		private void printSettings(){
			if(background){
				System.out.println("settings: ");
				System.out.println(" decimal: "+decimal);
				System.out.println(" operator: "+operator);
				System.out.println(" register: "+register);
				System.out.println(" start: "+start);
				System.out.println(" numbers: "+numbers);
				System.out.println(" op: "+op);
				System.out.println(" reg: "+reg);
				System.out.println(" memory: "+	memory);
			}	
		}//end print settings

		//default settings
		//flags
		private boolean decimal = false; //is a decimal point entered
		private boolean operator = false; //is the operator entered
		private boolean register = true; //is there a previous value
		private boolean start = true; //is this the beginging of entry
		private boolean numbers = false; //are there numbers in the input
		private boolean background = false; //turn on command line output
		//stuff
		private String op = "="; //set default op to equals
		private double reg = 0.0; //register for previouly entered or calculated values
		private double memory = 0.0; //number memory

	};//end ActionListener 

}//end CalculatorPanel