/*******************************************************************************
 * Copyright (c) 2001, 2004 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
 *     Jens Lukowski/Innoopract - initial renaming/restructuring
 *     
 *******************************************************************************/
package org.eclipse.wst.sse.ui.views.contentoutline;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.OperationCanceledException;
import org.eclipse.core.runtime.Platform;
import org.eclipse.core.runtime.Status;
import org.eclipse.core.runtime.jobs.Job;
import org.eclipse.jface.viewers.StructuredViewer;
import org.eclipse.swt.widgets.Display;
import org.eclipse.ui.PlatformUI;
import org.eclipse.wst.sse.ui.internal.SSEUIPlugin;
import org.w3c.dom.Document;
import org.w3c.dom.Node;

/**
 * This job holds a queue of updates (affected nodes) for the outline.
 * When a new request comes in, the current run is canceled, the new 
 * request is added to the queue, then the job is re-scheduled.
 * 
 * @author pavery
 */
public class RefreshOutlineJob extends Job {

	private static final long UPDATE_DELAY = 200;
	/** List of refresh requests (Nodes)*/
	private final List fRequests;
	/** the tree viewer */
	private final StructuredViewer fViewer;
	/** debug flag */
	private static final boolean DEBUG;
	static {
		String value = Platform.getDebugOption("org.eclipse.wst.sse.ui/debug/outline"); //$NON-NLS-1$
		DEBUG = value != null && value.equalsIgnoreCase("true"); //$NON-NLS-1$
	}
	
	public RefreshOutlineJob(StructuredViewer viewer) {
		
		// might need a different label, like "Refreshing Outline"
		super(SSEUIPlugin.getResourceString("%JFaceNodeAdapter.0"));
		setPriority(Job.LONG);
		setSystem(true);
		fRequests = new ArrayList(1);
		fViewer = viewer;
	}
	/**
	 * Adds the given resource to the set of resources that need refreshing.
	 * Synchronized in order to protect the collection during add.
	 * @param resource
	 */
	private synchronized void addRequest(Node node) {
		
		// if we already have a request which contains the new request,
		// discare the new request
		int size = fRequests.size();
		for (int i=0; i<size; i++) {
			if(contains((Node)fRequests.get(i), node))
				return;
		}
		// if new request is contains any existing requests,
		// remove those
		for (Iterator it = fRequests.iterator(); it.hasNext();) {
			if(contains(node, (Node)it.next()))
				it.remove();
		}
		fRequests.add(node);
	}
	/**
	 * This method also synchronized because it accesses the fRequests queue
	 * @return an array of the currently requested Nodes to refresh
	 */
	private synchronized Node[] getRequests() {
		
		Node[] toRefresh = (Node[]) fRequests.toArray(new Node[fRequests.size()]);
		fRequests.clear();
		return toRefresh;
	}
	
	/**
	 * Invoke a refresh on the viewer on the given node.
	 * @param node
	 */
	public void refresh(Node node) {
		
		if (node == null)
			return;
		
		cancel();
		addRequest(node);	
		schedule(UPDATE_DELAY);
	}
	
	/**
	 * @return if the root is parent of possible, return true, otherwise
	 *         return false
	 */
	private boolean contains(Node root, Node possible) {

		if (DEBUG) {
			System.out.println("==============================================================================================================");
			System.out.println("recursive call w/ root: " + root.getNodeName() + " and possible: " + possible);
			System.out.println("--------------------------------------------------------------------------------------------------------------");
		}
		
		// the following checks are important
		// #document node will break the algorithm otherwise
		
		// can't contain the parent if it's null
		if (root == null) {
		    if (DEBUG) System.out.println("returning false: root is null");
			return false;
		}
		// nothing can be parent of Document node
		if (possible instanceof Document) {
		    if (DEBUG) System.out.println("returning false: possible is Document node");
		    return false;
		}
		// document contains everything
		if(root instanceof Document) {
		    if (DEBUG) System.out.println("returning true: root is Document node");
		    return true;
		}
		
		// depth first
		Node current = root;
		// loop siblings
		while (current != null) {
			if (DEBUG) System.out.println("   -> iterating sibling (" + current.getNodeName() + ")");
			// found it
			if (possible.equals(current)) {		    
				if (DEBUG) System.out.println("   !!! found: " + possible.getNodeName() + " in subtree for: " + root.getNodeName());
				return true;
			}
			// drop one level deeper if necessary
			if (current.getFirstChild() != null) {
				return contains(current.getFirstChild(), possible);
			}
			current = current.getNextSibling();
		}
		// never found it
		return false;
	}
	
	protected IStatus run(IProgressMonitor monitor) {
		IStatus status = Status.OK_STATUS;
		try {
			Node[] toRefresh = getRequests();
			for (int i = 0; i < toRefresh.length; i++) {
				if (monitor.isCanceled())
					throw new OperationCanceledException();
				doRefresh(toRefresh[i]);
			}
		}
		finally {
			monitor.done();
		}
		return status;
	}
	
	/**
	 * Refresh must be on UI thread because it's on a SWT widget.
	 * @param node
	 */
	private void doRefresh(final Node node) {
		final Display display = PlatformUI.getWorkbench().getDisplay();
		display.asyncExec(new Runnable() {
			public void run() {
			    
			    if(DEBUG)
			        System.out.println("refresh on: [" +node.getNodeName()+ "]");
			        
			    if(node instanceof Document)
			        fViewer.refresh();
			    else
			        fViewer.refresh(node);
			}
		});
	}

}