/*******************************************************************************
 * Copyright (c) 2000, 2006 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.debug.internal.ui.actions;


import java.util.Iterator;

import org.eclipse.core.runtime.MultiStatus;
import org.eclipse.debug.core.DebugException;
import org.eclipse.debug.internal.ui.DebugUIPlugin;
import org.eclipse.jface.action.IAction;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.StructuredSelection;
import org.eclipse.swt.custom.BusyIndicator;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.ui.IActionDelegate2;
import org.eclipse.ui.IViewActionDelegate;
import org.eclipse.ui.IViewPart;
import org.eclipse.ui.IWorkbenchWindow;

public abstract class AbstractDebugActionDelegate implements IViewActionDelegate, IActionDelegate2 {
	
	/**
	 * The underlying action for this delegate
	 */
	private IAction fAction;
	/**
	 * This action's view part, or <code>null</code>
	 * if not installed in a view.
	 */
	private IViewPart fViewPart;
	
	/**
	 * Cache of the most recent seletion
	 */
	private IStructuredSelection fSelection = StructuredSelection.EMPTY;
	
	/**
	 * Whether this delegate has been initialized
	 */
	private boolean fInitialized = false;
	
	/**
	 * It's crucial that delegate actions have a zero-arg constructor so that
	 * they can be reflected into existence when referenced in an action set
	 * in the plugin's plugin.xml file.
	 */
	public AbstractDebugActionDelegate() {
	}
	
	/* (non-Javadoc)
	 * @see org.eclipse.ui.IWorkbenchWindowActionDelegate#dispose()
	 */
	public void dispose(){
        fSelection= null;
	}

	/* (non-Javadoc)
	 * @see org.eclipse.ui.IActionDelegate#run(org.eclipse.jface.action.IAction)
	 */
	public void run(IAction action){
	    if (action.isEnabled()) {
			IStructuredSelection selection = getSelection();
			// disable the action so it cannot be run again until an event or selection change
			// updates the enablement
			action.setEnabled(false);
			runInForeground(selection);
	    }
	}
	
	/**
	 * Runs this action in the UI thread.
	 */
	private void runInForeground(final IStructuredSelection selection) {
	    final MultiStatus status= 
			new MultiStatus(DebugUIPlugin.getUniqueIdentifier(), DebugException.REQUEST_FAILED, getStatusMessage(), null); 	    
		BusyIndicator.showWhile(Display.getCurrent(), new Runnable() {
			public void run() {
			    Iterator selectionIter = selection.iterator();
				while (selectionIter.hasNext()) {
					Object element= selectionIter.next();
					try {
						// Action's enablement could have been changed since
						// it was last enabled.  Check that the action is still
						// enabled before running the action.
						if (isEnabledFor(element))
							doAction(element);
					} catch (DebugException e) {
						status.merge(e.getStatus());
					}
				}
			}
		});
		reportErrors(status);
	}

	private void reportErrors(final MultiStatus ms) {
		if (!ms.isOK()) {
			IWorkbenchWindow window= DebugUIPlugin.getActiveWorkbenchWindow();
			if (window != null) {
				DebugUIPlugin.errorDialog(window.getShell(), ActionMessages.AbstractDebugActionDelegate_0, getErrorDialogMessage(), ms);
			} else {
				DebugUIPlugin.log(ms);
			}
		}
	}

	/* (non-Javadoc)
	 * @see org.eclipse.ui.IActionDelegate#selectionChanged(org.eclipse.jface.action.IAction, org.eclipse.jface.viewers.ISelection)
	 */
	public void selectionChanged(IAction action, ISelection s) {
		boolean wasInitialized= initialize(action, s);		
		if (!wasInitialized) {
			if (getView() != null) {
				update(action, s);
			}
		}
	}
	
	protected void update(IAction action, ISelection s) {
		if (s instanceof IStructuredSelection) {
			IStructuredSelection ss = (IStructuredSelection)s;
			action.setEnabled(getEnableStateForSelection(ss));
			setSelection(ss);
		} else {
			action.setEnabled(false);
			setSelection(StructuredSelection.EMPTY);
		}
	}
	
	/**
	 * Performs the specific action on this element.
	 */
	protected abstract void doAction(Object element) throws DebugException;

	/**
	 * Returns the String to use as an error dialog message for
	 * a failed action. This message appears as the "Message:" in
	 * the error dialog for this action.
	 * Default is to return null.
	 */
	protected String getErrorDialogMessage(){
		return null;
	}
	/**
	 * Returns the String to use as a status message for
	 * a failed action. This message appears as the "Reason:"
	 * in the error dialog for this action.
	 * Default is to return the empty String.
	 */
	protected String getStatusMessage(){
		return ""; //$NON-NLS-1$
	}

	/* (non-Javadoc)
	 * @see org.eclipse.ui.IViewActionDelegate#init(org.eclipse.ui.IViewPart)
	 */
	public void init(IViewPart view) {
		fViewPart = view;
	}
	
	/**
	 * Returns this action's view part, or <code>null</code>
	 * if not installed in a view.
	 * 
	 * @return view part or <code>null</code>
	 */
	protected IViewPart getView() {
		return fViewPart;
	}

	/**
	 * Initialize this delegate, updating this delegate's
	 * presentation.
	 * As well, all of the flavors of AbstractDebugActionDelegates need to 
	 * have the initial enabled state set with a call to update(IAction, ISelection).
	 * 
	 * @param action the presentation for this action
	 * @return whether the action was initialized
	 */
	protected boolean initialize(IAction action, ISelection selection) {
		if (!isInitialized()) {
			setAction(action);
			update(action, selection);
			setInitialized(true);
			return true;
		}
		return false;
	}

	/**
	 * Returns the most recent selection
	 * 
	 * @return structured selection
	 */	
	protected IStructuredSelection getSelection() {
		return fSelection;
	}
	
	/**
	 * Sets the most recent selection
	 * 
	 * @parm selection structured selection
	 */	
	private void setSelection(IStructuredSelection selection) {
		fSelection = selection;
	}	
	
	protected void setAction(IAction action) {
		fAction = action;
	}

	protected IAction getAction() {
		return fAction;
	}
	
	protected boolean isInitialized() {
		return fInitialized;
	}

	protected void setInitialized(boolean initialized) {
		fInitialized = initialized;
	}
	
	/**
	 * Return whether the action should be enabled or not based on the given selection.
	 */
	protected boolean getEnableStateForSelection(IStructuredSelection selection) {
		if (selection.size() == 0) {
			return false;
		}
		Iterator itr= selection.iterator();
		while (itr.hasNext()) {
			Object element= itr.next();
			if (!isEnabledFor(element)) {
				return false;
			}
		}
		return true;		
	}

	protected boolean isEnabledFor(Object element) {
		return true;
	}

	/* (non-Javadoc)
	 * @see org.eclipse.ui.IActionDelegate2#runWithEvent(org.eclipse.jface.action.IAction, org.eclipse.swt.widgets.Event)
	 */
	public void runWithEvent(IAction action, Event event) {
		run(action);
	}

	/* (non-Javadoc)
	 * @see org.eclipse.ui.IActionDelegate2#init(org.eclipse.jface.action.IAction)
	 */
	public void init(IAction action) {
		fAction = action;
	}

}