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

/**
 *  The JExceptionDialog class provides easy-to-use, single-call methods
 *  for displaying error dialogs based on an exception. The dialogs
 *  will contain a "Show Details" button that shows the exception's
 *  stack trace when clicked. <br /><br />
 *  
 *  There are two variants of the dialog showing method: showDialog
 *  and showFatalDialog. The latter should be used if your program
 *  cannot recover from the exception and needs to shut down. <br /><br />
 *  
 *  Example usage:<br /><br />
 *  
 *  try {<br />
		// Dangerous code here<br />
	} catch (SomeException e) {<br />
		JExceptionDialog.showDialog(e, null) ;<br />
	}<br /><br />
	
 *  JExceptionDialog also provides a method for getting the String
 *  that would be printed to System.err if an exception's printStackTrace method
 *  was called as a String.
 *  
 *  @author Michael Davies (coolguy5678)
 */
public class JExceptionDialog extends JDialog {
	
	private Exception baseException ;
	
	private JButton okButton ;
	private JButton detailsButton ;
	
	private JTextArea detailsArea ;
	private JScrollPane detailsScroll ;
	
	private boolean detailsIsActive ;
	
	/**
	 *  The title of any exception dialogs that are displayed
	 *  without specifying a title. You may want to set
	 *  this to the name of your application. <br /><br />
	 *  
	 *  The default value is "Error".
	 */
	public static String defaultTitle = "Error" ;
	
	/**
	 *  The error message of any exception dialogs that are displayed
	 *  without specifying a message. <br /><br />
	 *  
	 *  The default value is "An unexpected error has occurred.".
	 */
	public static String defaultErrorMessage = "An unexpected error has occurred." ;
	
	/**
	 *  The error message of any fatal exception dialogs that are displayed
	 *  without specifying a message. <br /><br />
	 *  
	 *  The default value is
	 *  "An unexpected fatal error has occurred, and the program must close."
	 */
	public static String defaultFatalErrorMessage = "A fatal error has occurred, " +
	                                                "and the program must close.";
	/**
	 *  The Icon that is used on the dialogs. <br /> <br />
	 *  
	 *  
	 *  The default is the "error" Icon from
	 *  the look and feel.
	 */
	public static Icon errorIcon = UIManager.getLookAndFeel().getDefaults().getIcon("OptionPane.errorIcon") ;
	
	//----------
	
	private JExceptionDialog(Exception baseException, Frame owner, String title, String error, String okTitle) {
		
		super(owner, title, true) ;
		
		this.baseException = baseException ;
		detailsIsActive = false ;
		
		// Set up the content pane
		JPanel cp = new JPanel() ;
		cp.setLayout(new BoxLayout(cp, BoxLayout.Y_AXIS)) ;
		
		// Add some padding
		cp.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
		
		// Add the error message
		JLabel label = new JLabel(error, errorIcon, JLabel.CENTER) ;
		label.setAlignmentX(Component.CENTER_ALIGNMENT) ;
		cp.add(label) ;
		cp.add(Box.createRigidArea(new Dimension(0, 10))) ;
		
		// Set up the panel for the buttons
		JPanel buttonPanel = new JPanel() ;
		buttonPanel.setLayout(new BoxLayout(buttonPanel, BoxLayout.X_AXIS)) ;
		buttonPanel.add(Box.createHorizontalGlue()) ; // Place buttons on the right edge
		
		// Set up the OK button
		okButton = new JButton(okTitle) ;
		okButton.addActionListener(list) ;
		okButton.setActionCommand("ok") ;
		buttonPanel.add(okButton) ;
		
		buttonPanel.add(Box.createRigidArea(new Dimension(10, 0))) ;
		
		// Set up the Details button
		detailsButton = new JButton("Show Details") ;
		detailsButton.addActionListener(list) ;
		detailsButton.setActionCommand("details") ;
		buttonPanel.add(detailsButton) ;
		
		// Add the button panel
		buttonPanel.add(Box.createRigidArea(new Dimension(10, 0))) ;
		cp.add(buttonPanel) ;
		cp.add(Box.createRigidArea(new Dimension(0, 10))) ;
		
		// Set up the details text area
		detailsArea = new JTextArea(getExceptionStackTrace(baseException)) ;
		detailsArea.setEditable(false) ;
		detailsScroll = new JScrollPane(detailsArea) ;
		
		// Final things
		setContentPane(cp) ;
		setResizable(false) ;
		pack() ;
		
		// Set size of details to our width by 100
		detailsScroll.setMinimumSize(new Dimension(getWidth(), 100)) ;
		detailsScroll.setPreferredSize(new Dimension(getWidth(), 100)) ;
		detailsScroll.setMaximumSize(new Dimension(getWidth(), 100)) ;
	}
	
	//----------
	
	private ActionListener list = new ActionListener() {
		public void actionPerformed(ActionEvent e) {
			
			// Go away if OK was pressed
			if (e.getActionCommand().equals("ok")) {
				setVisible(false) ;
				dispose() ;
			}
			
			// Or toggle the details
			else if (e.getActionCommand().equals("details")) {
				
				detailsIsActive = !detailsIsActive ;
				
				if (detailsIsActive) {
					getContentPane().add(detailsScroll) ;
					detailsButton.setText("Hide Details") ;
				} else {
					getContentPane().remove(detailsScroll) ;
					detailsButton.setText("Show Details") ;
				}
				
				pack() ;
			}
		}
	} ;
	
	//----------
	
	/**
	 *  Get the text that would be printed to System.err
	 *  if e.printStackTrace() was called, as a String.
	 *  
	 *  @param e the Throwable to get the stack trace String of
	 *  @return the String description of the stack trace
	 */
	public static String getExceptionStackTrace(Throwable e) {
		
		StringBuffer s = new StringBuffer() ;
		
		// Borrowed this code from Throwable.printStackTrace
		s.append(e + "\n") ;
		StackTraceElement[] trace = e.getStackTrace() ;
		for (int i = 0 ; i < trace.length ; i++) s.append("\tat " + trace[i] + "\n") ;
		
		Throwable ourCause = e.getCause() ;
		if (ourCause != null) appendStackTraceAsCause(ourCause, trace, s) ;
		
		return s.toString() ;
	}
	
	private static void appendStackTraceAsCause(Throwable e, StackTraceElement[] causedTrace, StringBuffer s) {
		
		// Borrowed this code from Throwable.printStackTraceAsCause
		StackTraceElement[] trace = e.getStackTrace() ;
		int m = trace.length - 1, n = causedTrace.length - 1 ;
		while (m >= 0 && n >= 0 && trace[m].equals(causedTrace[n])) {
			m-- ; n-- ;
		}
		
		int framesInCommon = trace.length - 1 - m ;
		
		s.append("Caused by: " + e + "\n") ;
		for (int i = 0 ; i <= m ; i++) s.append("\tat " + trace[i] + "\n") ;
		if (framesInCommon != 0) s.append("\t... " + framesInCommon + " more\n") ;
		
		Throwable ourCause = e.getCause() ;
		if (ourCause != null) appendStackTraceAsCause(ourCause, trace, s) ;
    }
	
	/**
	 *  Display an error dialog.
	 *  
	 *  @param baseException the exception on which to base the dialog
	 *  @param owner the owner of the exception dialog (can be null)
	 *  @param title the title of the dialog
	 *  @param errorMessage the error message to display on the dialog
	 *  @throws NullPointerException if either baseException, title or errorMessage is null
	 */
	public static void showDialog(Exception baseException, Frame owner, String title, String errorMessage) {
		
		if (baseException == null || title == null || errorMessage == null) {
			
			throw new NullPointerException() ;
		}
		
		new JExceptionDialog(baseException, owner, title, errorMessage, "OK").setVisible(true) ;
	}
	
	/**
	 *  Display an error dialog, using the default title and error message.
	 *  
	 *  @param baseException the exception on which to base the dialog
	 *  @param owner the owner of the exception dialog (can be null)
	 *  @throws NullPointerException if either argument is null
	 */
	public static void showDialog(Exception baseException, Frame owner) {
		
		showDialog(baseException, owner, defaultTitle, defaultErrorMessage) ;
	}
	
	/**
	 *  Display an error dialog for a fatal error, and exit.
	 *  
	 *  @param baseException the exception on which to base the dialog
	 *  @param owner the owner of the exception dialog (can be null)
	 *  @param title the title of the dialog
	 *  @param errorMessage the error message to display on the dialog
	 *  @param errorCode the error code to exit with
	 *  @throws NullPointerException if either baseException, title or errorMessage is null
	 */
	public static void showFatalDialog(Exception baseException, Frame owner, String title, String errorMessage, int errorCode) {
		
		if (baseException == null || title == null || errorMessage == null) {
			
			throw new NullPointerException() ;
		}
		
		new JExceptionDialog(baseException, owner, title, errorMessage, "Exit").setVisible(true) ;
		System.exit(errorCode) ;
	}
	
	/**
	 *  Display an error dialog for a fatal error, and exit, using the default title, error message,
	 *  and an error code of -1.
	 *  
	 *  @param baseException the exception on which to base the dialog
	 *  @param owner the owner of the exception dialog (can be null)
	 *  @throws NullPointerException if either argument is null
	 */
	public static void showFatalDialog(Exception baseException, Frame owner) {
		
		showFatalDialog(baseException, owner, defaultTitle, defaultFatalErrorMessage, -1) ;
	}
}