/*******************************************************************************
 * Copyright (c) 2003, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.internal.ide;

import java.text.MessageFormat;

import org.eclipse.jface.dialogs.IDialogConstants;
import org.eclipse.jface.dialogs.MessageDialog;
import org.eclipse.jface.window.Window;
import org.eclipse.osgi.util.NLS;
import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTError;
import org.eclipse.swt.widgets.MessageBox;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.ui.application.IWorkbenchConfigurer;
import org.eclipse.ui.internal.ide.dialogs.InternalErrorDialog;

/**
 * Handles exception while running the event loop.
 * <p>
 * In case of a "simpler" exception such as NPE, log the exception,
 * open a dialog to inform the user and try to keep running.
 * In case of a exception like OutOfMemory and SWTError, log the exception,
 * open a dialog to ask the user to decide if the workbench should 
 * be terminated.
 * </p>
 */
public final class IDEExceptionHandler {

    private int exceptionCount = 0;

    private InternalErrorDialog dialog;

    private Shell defaultParent = new Shell();

    private boolean closing = false;

    private IWorkbenchConfigurer workbenchConfigurer;

    //Pre-load all Strings trying to run as light as possible in case of fatal errors.
    private static String MSG_OutOfMemoryError = IDEWorkbenchMessages.FatalError_OutOfMemoryError;

    private static String MSG_StackOverflowError = IDEWorkbenchMessages.FatalError_StackOverflowError;

    private static String MSG_VirtualMachineError = IDEWorkbenchMessages.FatalError_VirtualMachineError;

    private static String MSG_SWTError = IDEWorkbenchMessages.FatalError_SWTError;

    private static String MSG_FATAL_ERROR = IDEWorkbenchMessages.FatalError;

    private static String MSG_FATAL_ERROR_Recursive = IDEWorkbenchMessages.FatalError_RecursiveError;

    private static String MSG_FATAL_ERROR_RecursiveTitle = IDEWorkbenchMessages.Internal_error;

    /**
     * Creates the exception handle for the IDE application
     * 
     * @param configurer an object for configuring the workbench
     */
    public IDEExceptionHandler(IWorkbenchConfigurer configurer) {
        super();
        workbenchConfigurer = configurer;
    }

    /**
     * Handles an event loop exception
     * 
     * @param t the exception to handle
     */
    public void handleException(Throwable t) {
        try {
            exceptionCount++;
            if (exceptionCount > 1) {
                if (closing) {
                    return;
                }
                Shell parent = defaultParent;
                if (dialog != null && dialog.getShell() != null
                        && !dialog.getShell().isDisposed())
                    parent = dialog.getShell();
                MessageBox box = new MessageBox(parent, SWT.ICON_ERROR
                        | SWT.YES | SWT.NO | SWT.SYSTEM_MODAL);
                box.setText(MSG_FATAL_ERROR_RecursiveTitle);
                box.setMessage(MessageFormat.format(MSG_FATAL_ERROR,
                        new Object[] { MSG_FATAL_ERROR_Recursive }));
                int result = box.open();
                if (result == SWT.YES) {
                    closeWorkbench();
                }
            } else {
                if (openQuestionDialog(t)) {
                    closeWorkbench();
                }
            }
        } finally {
            exceptionCount--;
        }
    }

    /**
     * Close the workbench and make sure all exceptions are handled.
     */
    private void closeWorkbench() {
        if (closing) {
            return;
        }

        try {
            closing = true;
            if (dialog != null && dialog.getShell() != null
                    && !dialog.getShell().isDisposed())
                dialog.close();
            workbenchConfigurer.emergencyClose();
        } catch (RuntimeException re) {
            // Workbench may be in such bad shape (no OS handles left, out of memory, etc)
            // that is cannot even close. Just bail out now.
            System.err
                    .println("Fatal runtime error happened during workbench emergency close."); //$NON-NLS-1$
            re.printStackTrace();
            throw re;
        } catch (Error e) {
            // Workbench may be in such bad shape (no OS handles left, out of memory, etc)
            // that is cannot even close. Just bail out now.
            System.err
                    .println("Fatal error happened during workbench emergency close."); //$NON-NLS-1$
            e.printStackTrace();
            throw e;
        }
    }

    /**
     * Inform the user about a fatal error. Return true if the user decide to 
     * exit workbench or if another fatal error happens while reporting it.
     */
    private boolean openQuestionDialog(Throwable internalError) {
        try {
            String msg = null;
            if (internalError instanceof OutOfMemoryError) {
                msg = MSG_OutOfMemoryError;
            } else if (internalError instanceof StackOverflowError) {
                msg = MSG_StackOverflowError;
            } else if (internalError instanceof VirtualMachineError) {
                msg = MSG_VirtualMachineError;
            } else if (internalError instanceof SWTError) {
                msg = MSG_SWTError;
            } else {
                if (internalError.getMessage() == null) {
                    msg = IDEWorkbenchMessages.InternalErrorNoArg;
                } else {
                    msg = NLS.bind(IDEWorkbenchMessages.InternalErrorOneArg, internalError.getMessage());
                }
                if (Policy.DEBUG_OPEN_ERROR_DIALOG)
                    return openQuestion(null, IDEWorkbenchMessages.Internal_error, msg, internalError, 1);
                return false;
            }
            // Always open the dialog in case of major error but do not show the
            // detail button if not in debug mode.
            Throwable detail = internalError;
            if (!Policy.DEBUG_OPEN_ERROR_DIALOG)
                detail = null;
            return InternalErrorDialog
                    .openQuestion(null, IDEWorkbenchMessages.Internal_error,
                            MessageFormat.format(MSG_FATAL_ERROR,
                                    new Object[] { msg }), detail, 1);
        } catch (Throwable th) {
            // Workbench may be in such bad shape (no OS handles left, out of memory, etc)
            // that is cannot show a message to the user. Just bail out now.
            System.err
                    .println("Error while informing user about event loop exception:"); //$NON-NLS-1$
            internalError.printStackTrace();
            System.err.println("Dialog open exception:"); //$NON-NLS-1$
            th.printStackTrace();
            return true;
        }
    }

    private boolean openQuestion(Shell parent, String title, String message,
            Throwable detail, int defaultIndex) {
        String[] labels;
        if (detail == null)
            labels = new String[] { IDialogConstants.YES_LABEL,
                    IDialogConstants.NO_LABEL };
        else
            labels = new String[] { IDialogConstants.YES_LABEL,
                    IDialogConstants.NO_LABEL,
                    IDialogConstants.SHOW_DETAILS_LABEL };

        dialog = new InternalErrorDialog(parent, title, null, message, detail,
                MessageDialog.QUESTION, labels, defaultIndex);

        if (detail != null)
            dialog.setDetailButton(2);
        boolean result = dialog.open() == Window.OK;
        dialog = null;
        return result;
    }
}