/*
Wotonomy: OpenStep design patterns for pure Java applications.
Copyright (C) 2000 Blacksmith, Inc.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see http://www.gnu.org
*/

package net.wotonomy.ui.swing.components;

import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.event.KeyEvent;

import javax.swing.JPasswordField;

/**
 * SmartPasswordField is an extention of JPasswordField. It does everything a
 * JPassword does, as well as limit the number of characters. The user of this
 * class can specify that a password can only have a maximum of 10 characters
 * for instance.
 *
 * @author rob@straylight.princeton.com
 * @author $Author: cgruber $
 * @version $Revision: 904 $
 */
public class SmartPasswordField extends JPasswordField {

	/*******************************
	 * CONSTANTS
	 *******************************/
	private static final int BACKSPACE = 8;
	private static final int DELETE = 127;
	private static final int SPACE = 32;
	private static final int DASH = 45;
	private static final int UNDERSCORE = 95;
	private static final int PERIOD = 46;
	private static final int PASTE = 22; // Ctl-V

	private int passwordLength = Integer.MAX_VALUE;

	/*******************************
	 * PUBLIC METHODS
	 *******************************/

	/**
	 * Default constructor.
	 */
	public SmartPasswordField() {
		super();
	}

	/**
	 * This constructor allows the user to set the maximum length of the password.
	 * 
	 * @param aLength The maximum length of the password.
	 */
	public SmartPasswordField(int aLength) {
		this();
		setPasswordLength(aLength);
	}

	/**
	 * Sets the maximum lenght of the password. The value must be 0 or greater. If
	 * the length specified is less than 0, then no action occurs.
	 * 
	 * @param aLength The maximum lenght of the password.
	 */
	public void setPasswordLength(int aLength) {
		if (aLength >= 0) {
			passwordLength = aLength;
		}
	}

	/**
	 * Returns the current maximum length of the password.
	 * 
	 * @return The current maximum length of the password.
	 */
	public int getPasswordLength() {
		return passwordLength;
	}

	/**
	 * This method processes a key event. This event is generated by input from the
	 * keyboard when this text field has the focus. This method is called for every
	 * key that is pressed and released on the keyboard. This includes modifier keys
	 * like the shift and alt keys. This class looks at the key and determines if
	 * the key is valid input given the restrictions of this class. <BR>
	 * <BR>
	 * 
	 * @param e A key event generated by a keyboard action.
	 */
	public void processKeyEvent(KeyEvent e) {
		String currentText = "";
		String testString = "";
		char newChar = e.getKeyChar();
		int currentLength = 0;
		int selectionStart = 0;
		int selectionEnd = 0;
		int endOfHead = 0;
		int startOfTail = 0;
		boolean backspace = false;
		boolean delete = false;
		boolean paste = false;
		boolean insertionPoint = false;
		boolean selectionAtStart = false;
		boolean selectionAtEnd = false;

		backspace = (newChar == BACKSPACE);
		delete = (newChar == DELETE);
		paste = (newChar == PASTE);

		if ((e.getKeyCode() == KeyEvent.VK_UNDEFINED) || ((backspace) || (delete) || (paste))) // A "key-typed" event
		{
			if (isValidCharacter(newChar)) {

				if ((isPrintableCharacter(newChar)) || (backspace) || (delete) || (paste)) {
					// Analyze the current contents of the field
					currentText = new String(getPassword());
					currentLength = currentText.length();

					selectionStart = getSelectionStart();
					selectionEnd = getSelectionEnd();

					insertionPoint = (selectionStart == selectionEnd);
					selectionAtStart = (selectionStart == 0);
					selectionAtEnd = (selectionEnd >= currentLength);
					if (selectionEnd > currentLength) {
						setSelectionEnd(currentLength);
					}

					// Generate new string
					if (selectionStart > 0) // Create head of test string
					{
						endOfHead = selectionStart;
						if (insertionPoint && backspace) {
							endOfHead -= 1;
						}
						testString += currentText.substring(0, endOfHead);
					}

					if (!(backspace || delete || paste)) // Add the new character
					{
						testString += newChar;
					}

					if (paste) // Add the string from the clipboard
					{
						Transferable data = getToolkit().getSystemClipboard().getContents(this);
						if (data != null) {
							try {
								String clipString = (String) data.getTransferData(DataFlavor.stringFlavor);
								testString += clipString;
							} catch (java.io.IOException ioe) {
								// Do nothing
							} catch (UnsupportedFlavorException ufe) {
								// Do nothing
							}
						}
					}

					if (selectionEnd < currentLength) // Add the tail of the string
					{
						startOfTail = selectionEnd;
						if (insertionPoint && delete) {
							startOfTail += 1;
						}
						testString += currentText.substring(startOfTail);
					}

				}

				if (testString.compareTo("") != 0) // Null string is OK
				{
					if (!(isValidString(testString))) {
						e.consume();
					}
				}
			} else {
				e.consume();
			}
		}
		super.processKeyEvent(e);

		postProcessing();
	}

	/*******************************
	 * PROTECTED METHODS
	 *******************************/

	/**
	 * Returns whether the inputted character is valid or not. In this case all
	 * characters are valid input.
	 * 
	 * @param aChar A character to perform the validity test with.
	 * @return True if the character is valid for this subclassed text field. <BR>
	 *         False is the character is not valid.
	 */
	protected boolean isValidCharacter(char aChar) {
		return true;
	}

	/**
	 * Returns whether a string is valid for this text field. As the user types from
	 * the keyboard, this method is called to determine if the new string in the
	 * text field is valid based upon the restriction of this class. The length of
	 * the new string is checked against the maximum password length.
	 * 
	 * @param aString The string to perform the validity check with.
	 * @return True if the length of the string is less than or equal to the maximum
	 *         length. False if the character is not valud.
	 */
	protected boolean isValidString(String aString) {
		if (aString.length() > passwordLength) {
			return false;
		}

		return true;
	}

	/**
	 * This class does not need any post processing.
	 */
	protected void postProcessing() {
		/* Do Nothing */
	}

	/*******************************
	 * PRIVATE METHODS
	 *******************************/

	private boolean isPrintableCharacter(char inputChar) {
		if ((inputChar >= ' ') && (inputChar <= '~')) {
			return true;
		}
		return false;
	}

}