/*
	Chapter 6:   Java Calculator
	Programmer:  Heather Jacob
	Date:        October 13, 2010
	Filename:    Calculator.java
	Purpose:     This program creates a calculator with a menu
*/

import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.text.DecimalFormat;
import javax.swing.JOptionPane;

public class Calculator extends Frame implements ActionListener
{
	private Button keys[];
		//An array of buttons numbered 0-15 to represent the numbers and operators of the calculator
	private Panel keypad;
		//A panel to display the buttons
	private TextField lcd;
		//A textfield across the top that will display the numbers as they're entered
	private double op1;
	private boolean first;
	private boolean foundKey;
	private boolean clearText;
	private int lastOp;
	private DecimalFormat calcPattern;

	public Calculator()
	{
		//Create an instance of the menu
		MenuBar mnuBar = new MenuBar();
		setMenuBar(mnuBar);

		//Construct and populate the File Menu
		Menu mnuFile = new Menu("File", true);
		mnuBar.add(mnuFile);
			MenuItem mnuFileExit = new MenuItem("Exit");
			mnuFile.add(mnuFileExit);

		//Construct and populate the Edit menu
		Menu mnuEdit = new Menu("Edit", true);
		mnuBar.add(mnuEdit);
			MenuItem mnuEditClear = new MenuItem("Clear");
			mnuEdit.add(mnuEditClear);
			mnuEdit.insertSeparator(1);
			MenuItem mnuEditCopy = new MenuItem("Copy");
			mnuEdit.add(mnuEditCopy);
			MenuItem mnuEditPaste = new MenuItem("Paste");
			mnuEdit.add(mnuEditPaste);

		//Construct and populate the About menu
		Menu mnuAbout = new Menu("About", true);
		mnuBar.add(mnuAbout);
			MenuItem mnuAboutCalculator = new MenuItem("About Calculator");
			mnuAbout.add(mnuAboutCalculator);

		//Add the ActionListener to each menu item
		mnuFileExit.addActionListener(this);
		mnuEditClear.addActionListener(this);
		mnuEditCopy.addActionListener(this);
		mnuEditPaste.addActionListener(this);
		mnuAboutCalculator.addActionListener(this);

		//Assign an ActionCommand to each menu item. When the user clicks the component, the getActionCommand() method retrieves the keyword and assigns it to a string variable, then the variable is used to search for a matching action.
		mnuFileExit.setActionCommand("Exit");
		mnuEditClear.setActionCommand("Clear");
		mnuEditCopy.setActionCommand("Copy");
		mnuEditPaste.setActionCommand("Paste");
		mnuAboutCalculator.setActionCommand("About");

		//Construct components and initialize beginning values
		lcd = new TextField(20);
			lcd.setEditable(false);
		keypad = new Panel();
		keys = new Button[16];
		first = true;
		op1 = 0.0;
		clearText = true;
		lastOp = 0;
		calcPattern = new DecimalFormat("########.########");

		//Construct and assign captions to the Buttons
		for (int i=0; i<=9; i++)
			keys[i] = new Button(String.valueOf(i));

		keys[10] = new Button("/");
		keys[11] = new Button("*");
		keys[12] = new Button("-");
		keys[13] = new Button("+");
		keys[14] = new Button("=");
		keys[15] = new Button(".");

		//Set Frame and keypad layout to grid layout
		setLayout(new BorderLayout());
		keypad.setLayout(new GridLayout(4,4,10,10));

		for (int i=7; i<=10; i++) // 7, 8, 9, divide
			keypad.add(keys[i]);

		for (int i=4; i<=6; i++) //4, 5, 6
			keypad.add(keys[i]);

		keypad.add(keys[11]); //multiply

		for (int i=1; i<=3; i++) //1, 2, 3
			keypad.add(keys[i]);

		keypad.add(keys[12]); //subtract

		keypad.add(keys[0]); // 0 key

		for (int i=15; i>=13; i--)
			keypad.add(keys[i]); // decimal point, =, +

		// Add ActionListener to each button in the array
		for (int i=0; i<keys.length; i++)
			keys[i].addActionListener(this);

		add(lcd, BorderLayout.NORTH);
		add(keypad, BorderLayout.CENTER);

		addWindowListener(
			new WindowAdapter()
			{
				public void windowClosing(WindowEvent e)
				{
					System.exit(0);
				}
			}
			);
	}// end of constructor method

    //When the user clicks one of the menu items or one of the buttons on the keypad, the ActionListener aactivates the actionPerformed() method where the action takes place.
 	public void actionPerformed(ActionEvent e)
 	{
		// Test for menu item clicks. Gets the variable from the getActionCommand() method in lines 67-71 and tries to find a match.
		String arg = e.getActionCommand();
		if (arg == "Exit")
			System.exit(0);
		if (arg == "Clear")
		{
			clearText = true;
			first = true;
			op1 = 0.0;
			lcd.setText("");
			lcd.requestFocus();
		}

		if (arg == "Copy")
		{
			Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();
			StringSelection contents = new StringSelection(lcd.getText());
			cb.setContents(contents, null);
			// contents is the string to be copied, the second argument is the owner of the
			// clipboard. null defaults to the current system and user
		}

		if (arg == "Paste")
		{
			Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();
			Transferable content = cb.getContents(this);
			try
			{
				String s = (String)content.getTransferData(DataFlavor.stringFlavor);
				lcd.setText(calcPattern.format(Double.parseDouble(s)));
			}
			catch (Throwable exc)
			{
				lcd.setText("");
			}
		}

		if (arg == "About")
		{
			String message = "Calculator ver. 1.0\nOpenExhibit Software\nCopyright 2007\nAll rights reserved";
			JOptionPane.showMessageDialog(null, message, "About Calculator", JOptionPane.INFORMATION_MESSAGE);
		}

		//Test for button clicks
		foundKey = false;

		// Search for the clicked key by going through the array one item at a time.
		for (int i=0; i<keys.length && !foundKey; i++)
		{
			// if the source of the click matches one of the keys in the array, foundkey is true and the index of that key becomes the variable used in the switch statement
			if(e.getSource() == keys[i])
			{
				foundKey = true;
				switch(i)
				{
					//number and decimal point buttons
					case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8: case 9: case 15:
						if(clearText)
						{
							lcd.setText(""); //Text in lcd is cleared
							clearText = false;
						}
						//concatenates the numbers to make one bigger number instead of several single digits
						lcd.setText(lcd.getText() + keys[i].getLabel());
						break;

						//operator buttons
						case 10: case 11: case 12: case 13: case 14:
							clearText = true; //Clears the text field after the user clicks an operator button (+,-,*,/,=) and allows the next number to be added

							if (first) // first operand
							{
								if(lcd.getText().length()==0) op1 = 0.0;
								else op1 = Double.parseDouble(lcd.getText());

								first = false;
								clearText = true;
								lastOp = i; // save last operator
							}
							else // second operand
							{
								switch(lastOp)
								{
									case 10:
										op1 /= Double.parseDouble(lcd.getText());
										break;
									case 11:
										op1 *= Double.parseDouble(lcd.getText());
										break;
									case 12:
										op1 -= Double.parseDouble(lcd.getText());
										break;
									case 13:
										op1 += Double.parseDouble(lcd.getText());
										break;
								} // end of switch(lastOp)
								lcd.setText(calcPattern.format(op1));
								clearText = true;

								if(i==14) first = true;
								else lastOp = i;
							} //end else
							break;
					} // end of switch
				} // end of if
			} // end of for
		} // end of ActionPerformed

	public static void main(String args[])
	{
		// set frame properties
		Calculator f = new Calculator();
		f.setTitle("Calculator Application");
		f.setBounds(200,200,300,300); // (width, height, top, left)
		f.setVisible(true);

		// set image properties and add to frame. Adds a little calculator icon to the titlebar
		Image icon = Toolkit.getDefaultToolkit().getImage("calcImage.gif");
		f.setIconImage(icon);
	} // end of main
} // end of class