/*******************************************************************************
 * Copyright (c) 2005 The Regents of the University of California. 
 * This material was produced under U.S. Government contract W-7405-ENG-36 
 * for Los Alamos National Laboratory, which is operated by the University 
 * of California for the U.S. Department of Energy. The U.S. Government has 
 * rights to use, reproduce, and distribute this software. NEITHER THE 
 * GOVERNMENT NOR THE UNIVERSITY MAKES ANY WARRANTY, EXPRESS OR IMPLIED, OR 
 * ASSUMES ANY LIABILITY FOR THE USE OF THIS SOFTWARE. If software is modified 
 * to produce derivative works, such modified software should be clearly marked, 
 * so as not to confuse it with the version available from LANL.
 * 
 * Additionally, 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
 * 
 * LA-CC 04-115
 *******************************************************************************/
package org.eclipse.ptp.debug.internal.ui.actions;

import java.util.Iterator;

import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.MultiStatus;
import org.eclipse.core.runtime.jobs.Job;
import org.eclipse.debug.core.DebugException;
import org.eclipse.debug.ui.IDebugUIConstants;
import org.eclipse.jface.action.IAction;
import org.eclipse.jface.dialogs.ErrorDialog;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.StructuredSelection;
import org.eclipse.ptp.debug.ui.PTPDebugUIPlugin;
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.INullSelectionListener;
import org.eclipse.ui.ISelectionListener;
import org.eclipse.ui.IViewActionDelegate;
import org.eclipse.ui.IViewPart;
import org.eclipse.ui.IWorkbenchPage;
import org.eclipse.ui.IWorkbenchPart;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.IWorkbenchWindowActionDelegate;

/**
 * @author Clement chu
 */
public abstract class AbstractDebugActionDelegate implements IWorkbenchWindowActionDelegate, IViewActionDelegate, IActionDelegate2, ISelectionListener, INullSelectionListener {
	/**
	 * 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;

	/**
	 * The window associated with this action delegate May be <code>null</code>
	 */
	protected IWorkbenchWindow fWindow;

	/**
	 * Background job for this action, or <code>null</code> if none.
	 */
	private DebugRequestJob fBackgroundJob = null;

	class DebugRequestJob extends Job {
		private Object[] fElements = null;
		/**
		 * Constructs a new job to perform a debug request (for example, step) in the background.
		 * 
		 * @param name
		 *            job name
		 */
		public DebugRequestJob(String name) {
			super(name);
			setPriority(Job.INTERACTIVE);
		}

		/*
		 * (non-Javadoc)
		 * 
		 * @see org.eclipse.core.runtime.jobs.Job#run(org.eclipse.core.runtime.IProgressMonitor)
		 */
		protected IStatus run(IProgressMonitor monitor) {
			MultiStatus status = new MultiStatus(PTPDebugUIPlugin.getUniqueIdentifier(), DebugException.REQUEST_FAILED, getStatusMessage(), null);
			for (int i = 0; i < fElements.length; i++) {
				Object element = fElements[i];
				try {
					doAction(element);
				} catch (DebugException e) {
					status.merge(e.getStatus());
				}
			}
			return status;
		}

		/**
		 * Sets the selection to operate on.
		 * 
		 * @param elements
		 */
		public void setTargets(Object[] elements) {
			fElements = elements;
		}

	}

	/**
	 * 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() {
		if (getWindow() != null) {
			getWindow().getSelectionService().removeSelectionListener(IDebugUIConstants.ID_DEBUG_VIEW, this);
		}
		fBackgroundJob = null;
		fSelection = null;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.IWorkbenchWindowActionDelegate#init(org.eclipse.ui.IWorkbenchWindow)
	 */
	public void init(IWorkbenchWindow window) {
		// listen to selection changes in the debug view
		setWindow(window);
		window.getSelectionService().addSelectionListener(IDebugUIConstants.ID_DEBUG_VIEW, this);
	}

	/*
	 * (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);
			if (isRunInBackground()) {
				runInBackground(action, selection);
			} else {
				runInForeground(selection);
			}
		}
	}

	/**
	 * Runs this action in a background job.
	 */
	private void runInBackground(IAction action, IStructuredSelection selection) {
		if (fBackgroundJob == null) {
			fBackgroundJob = new DebugRequestJob(action.getText());
		}
		fBackgroundJob.setTargets(selection.toArray());
		fBackgroundJob.schedule();
	}

	/**
	 * Runs this action in the UI thread.
	 */
	private void runInForeground(final IStructuredSelection selection) {
		final MultiStatus status = new MultiStatus(PTPDebugUIPlugin.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 {
						doAction(element);
					} catch (DebugException e) {
						status.merge(e.getStatus());
					}
				}
			}
		});
		reportErrors(status);
	}

	private void reportErrors(final MultiStatus ms) {
		if (!ms.isOK()) {
			IWorkbenchWindow window = PTPDebugUIPlugin.getActiveWorkbenchWindow();
			if (window != null) {
				ErrorDialog.openError(window.getShell(), getErrorDialogTitle(), getErrorDialogMessage(), ms);
			} else {
				PTPDebugUIPlugin.log(ms);
			}
		}
	}

	/**
	 * Returns whether or not this action should be run in the background. Subclasses may override.
	 * 
	 * @return whether or not this action should be run in the background
	 */
	protected boolean isRunInBackground() {
		return false;
	}

	/**
	 * AbstractDebugActionDelegates come in 2 flavors: IViewActionDelegate, IWorkbenchWindowActionDelegate delegates.
	 * </p>
	 * <ul>
	 * <li>IViewActionDelegate delegate: getView() != null</li>
	 * <li>IWorkbenchWindowActionDelegate: getView == null</li>
	 * </ul>
	 * <p>
	 * Only want to call update(action, selection) for IViewActionDelegates. An initialize call to update(action, selection) is made for all flavors to set the initial enabled state of the underlying action. IWorkbenchWindowActionDelegate's listen to selection changes in the debug view only.
	 * </p>
	 * 
	 * @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 title for a failed action. Default is to return null.
	 */
	protected String getErrorDialogTitle() {
		return null;
	}

	/**
	 * 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-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);
			if (getView() == null) {
				// update on the selection in the debug view
				IWorkbenchWindow window = getWindow();
				if (window != null && window.getShell() != null && !window.getShell().isDisposed()) {
					IWorkbenchPage page = window.getActivePage();
					if (page != null) {
						selection = page.getSelection(IDebugUIConstants.ID_DEBUG_VIEW);
					}
				}
			}
			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;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.ISelectionListener#selectionChanged(org.eclipse.ui.IWorkbenchPart, org.eclipse.jface.viewers.ISelection)
	 */
	public void selectionChanged(IWorkbenchPart part, ISelection selection) {
		update(getAction(), selection);
	}

	protected void setAction(IAction action) {
		fAction = action;
	}

	protected IAction getAction() {
		return fAction;
	}

	protected void setView(IViewPart viewPart) {
		fViewPart = viewPart;
	}

	protected boolean isInitialized() {
		return fInitialized;
	}

	protected void setInitialized(boolean initialized) {
		fInitialized = initialized;
	}

	protected IWorkbenchWindow getWindow() {
		return fWindow;
	}

	protected void setWindow(IWorkbenchWindow window) {
		fWindow = window;
	}

	/**
	 * 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) {
	}
}