/*******************************************************************************
 * Copyright (c) 2000, 2018 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
 *
 *******************************************************************************/
package org.eclipse.dltk.ui.viewsupport;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Stack;

import org.eclipse.core.resources.IResource;
import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.dltk.core.IModelElement;
import org.eclipse.dltk.core.ISourceModule;
import org.eclipse.swt.widgets.Item;
import org.eclipse.swt.widgets.Widget;

/**
 * Helper class for updating error markers and other decorators that work on
 * resources. Items are mapped to their element's underlying resource. Method
 * <code>resourceChanged</code> updates all items that are affected from the
 * changed elements.
 */
public class ResourceToItemsMapper {

	public static interface IContentViewerAccessor {
		public void doUpdateItem(Widget item);
	}

	private static final int NUMBER_LIST_REUSE = 10;

	// map from resource to item
	private HashMap fResourceToItem;
	private Stack fReuseLists;

	private IContentViewerAccessor fContentViewerAccess;

	public ResourceToItemsMapper(IContentViewerAccessor viewer) {
		fResourceToItem = new HashMap();
		fReuseLists = new Stack();

		fContentViewerAccess = viewer;
	}

	/**
	 * Must be called from the UI thread.
	 *
	 * @param changedResource
	 *                            Changed resource
	 */
	public void resourceChanged(IResource changedResource) {
		Object obj = fResourceToItem.get(changedResource);
		if (obj == null) {
			// not mapped
		} else if (obj instanceof Item) {
			updateItem((Item) obj);
		} else { // List of Items
			List list = (List) obj;
			for (int k = 0; k < list.size(); k++) {
				updateItem((Item) list.get(k));
			}
		}
	}

	private void updateItem(Item item) {
		if (!item.isDisposed()) {
			fContentViewerAccess.doUpdateItem(item);
		}
	}

	/**
	 * Adds a new item to the map.
	 *
	 * @param element
	 *                    Element to map
	 * @param item
	 *                    The item used for the element
	 */
	public void addToMap(Object element, Item item) {
		IResource resource = getCorrespondingResource(element);
		if (resource != null) {
			Object existingMapping = fResourceToItem.get(resource);
			if (existingMapping == null) {
				fResourceToItem.put(resource, item);
			} else if (existingMapping instanceof Item) {
				if (existingMapping != item) {
					List list = getNewList();
					list.add(existingMapping);
					list.add(item);
					fResourceToItem.put(resource, list);
				}
			} else { // List
				List list = (List) existingMapping;
				if (!list.contains(item)) {
					list.add(item);
				}
			}
		}
	}

	/**
	 * Removes an element from the map.
	 *
	 * @param element
	 *                    The data element
	 * @param item
	 *                    The table or tree item
	 */
	public void removeFromMap(Object element, Item item) {
		IResource resource = getCorrespondingResource(element);
		if (resource != null) {
			Object existingMapping = fResourceToItem.get(resource);
			if (existingMapping == null) {
				return;
			} else if (existingMapping instanceof Item) {
				fResourceToItem.remove(resource);
			} else { // List
				List list = (List) existingMapping;
				list.remove(item);
				if (list.isEmpty()) {
					fResourceToItem.remove(list);
					releaseList(list);
				}
			}
		}
	}

	private List getNewList() {
		if (!fReuseLists.isEmpty()) {
			return (List) fReuseLists.pop();
		}
		return new ArrayList(2);
	}

	private void releaseList(List list) {
		if (fReuseLists.size() < NUMBER_LIST_REUSE) {
			fReuseLists.push(list);
		}
	}

	/**
	 * Clears the map.
	 */
	public void clearMap() {
		fResourceToItem.clear();
	}

	/**
	 * Tests if the map is empty
	 *
	 * @return Returns if there are mappings
	 */
	public boolean isEmpty() {
		return fResourceToItem.isEmpty();
	}

	private static IResource getCorrespondingResource(IModelElement elem) {
		IResource res = elem.getResource();
		if (res == null) {
			ISourceModule cu = (ISourceModule) elem
					.getAncestor(IModelElement.SOURCE_MODULE);
			if (cu != null) {
				// elements in compilation units are mapped to the underlying
				// resource of the original cu
				res = cu.getResource();
			}
		}
		return res;
	}

	/**
	 * Method that decides which elements can have error markers Returns null if
	 * an element can not have error markers.
	 *
	 * @param element
	 *                    The input element
	 * @return Returns the corresponding resource or null
	 */
	private static IResource getCorrespondingResource(Object element) {
		if (element instanceof IModelElement) {
			return getCorrespondingResource((IModelElement) element);
		} else if (element instanceof IResource) {
			return (IResource) element;
		} else if (element instanceof IAdaptable) {
			IModelElement elem = ((IAdaptable) element)
					.getAdapter(IModelElement.class);
			if (elem != null) {
				return getCorrespondingResource(elem);
			}
			return (((IAdaptable) element).getAdapter(IResource.class));
		}
		return null;
	}

}