/* ********************************************************************** **
** Copyright notice **
** **
** (c) 2005-2009 RSSOwl Development Team **
** http://www.rssowl.org/ **
** **
** 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.rssowl.org/legal/epl-v10.html **
** **
** A copy is found in the file epl-v10.html and important notices to the **
** license from the team is found in the textfile LICENSE.txt distributed **
** in this package. **
** **
** This copyright notice MUST APPEAR in all copies of the file! **
** **
** Contributors: **
** RSSOwl Development Team - initial API and implementation **
** **
** ********************************************************************** */
package org.rssowl.core.util;
import org.rssowl.core.internal.persist.ComplexMergeResult;
import org.rssowl.core.persist.IEntity;
import org.rssowl.core.persist.IPersistable;
import org.rssowl.core.persist.MergeCapable;
import org.rssowl.core.persist.Reparentable;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
/**
* Some useful methods for dealing with MergeCapable objects.,
*
* @author Ismael Juma (ismael@juma.me.uk)
*/
public class MergeUtils {
/* Set of Properties to ignore during merge */
private static final Set<String> EXCLUDE_PROPERTIES = new HashSet<String>(Arrays.asList(SyncUtils.GOOGLE_MARKED_READ, SyncUtils.GOOGLE_MARKED_UNREAD, SyncUtils.GOOGLE_LABELS));
/**
* Helper method that simply does:
* <code>o1 == null ? o2 == null : o1.equals(o2)</code> This is useful because
* it handles nulls and it forces {@code o2} to be assignable to {@code o1}.
*
* @param <T> The type of the first object being compared.
* @param <U> The type of the second object being compared.
* @param o1 First object being compared.
* @param o2 Second object being compared.
* @return <code>true</code> if both objects are equal or if both objects are
* <code>null</code>.
*/
public static <T, U extends T> boolean equals(T o1, U o2) {
return o1 == null ? o2 == null : o1.equals(o2);
}
/**
* Merges origin into destination. This is mostly useful because it deals with
* the case where one of the items is null.
*
* @param <T>
* @param destination
* @param origin
* @return an object where the origin was merged into the destination.
*/
public static final <T extends MergeCapable<T>> ComplexMergeResult<T> merge(T destination, T origin) {
if (destination == null) {
ComplexMergeResult<T> mergeResult;
if (origin == null)
mergeResult = ComplexMergeResult.create(null);
else
mergeResult = ComplexMergeResult.create(origin, true);
return mergeResult;
}
if (origin == null)
return ComplexMergeResult.create(null, true);
ComplexMergeResult<T> mergeResult = ComplexMergeResult.create(destination);
mergeResult.addAll(destination.merge(origin));
return mergeResult;
}
/**
* Convenience method that calls
* {@link #merge(List, List, Comparator, IPersistable)} with a Comparator that
* uses equals().
*
* @param <T>
* @param existingList
* @param newList
* @param newParent
* @return ListMergeResult indicating the results of the merge operation.
*/
public static final <T extends MergeCapable<T>> ComplexMergeResult<List<T>> merge(List<T> existingList, List<T> newList, IPersistable newParent) {
return merge(existingList, newList, new Comparator<T>() {
public int compare(T o1, T o2) {
if ((o1 == null ? o2 == null : o1.equals(o2))) {
return 0;
}
return -1;
}
}, newParent);
}
/**
* Merges the contents of <code>newList</code> into <code>existingList</code>
* and returns a ListMergeResult indications the operations performed.
*
* @param <T>
* @param existingList
* @param newList
* @param comparator
* @param newParent
* @return ListMergeResult indicating the results of the merge operation.
*/
public static final <T extends MergeCapable<T>> ComplexMergeResult<List<T>> merge(List<T> existingList, List<T> newList, Comparator<T> comparator, IPersistable newParent) {
if ((existingList == null) && (newList == null || newList.isEmpty()))
return ComplexMergeResult.create(null);
if (newList == null && existingList != null) {
existingList.clear();
return ComplexMergeResult.create(existingList, true);
}
/* Defensive copy */
List<T> newListCopy = new ArrayList<T>(newList);
if (existingList == null) {
ComplexMergeResult<List<T>> mergeResult = ComplexMergeResult.create(newListCopy, true);
for (T item : newListCopy) {
reparent(item, newParent);
mergeResult.addUpdatedObject(item);
}
return mergeResult;
}
ComplexMergeResult<List<T>> mergeResult = ComplexMergeResult.create(existingList);
Iterator<T> existingIt = existingList.iterator();
while (existingIt.hasNext()) {
T existingItem = existingIt.next();
boolean matchFound = false;
for (Iterator<T> newItemsIt = newListCopy.iterator(); newItemsIt.hasNext();) {
T newItem = newItemsIt.next();
/*
* If the existing List already has an item that matches this new item,
* then remove it from the List of new items, set the matchFound flag
* and break from the loop.
*/
if (comparator.compare(newItem, existingItem) == 0) {
newItemsIt.remove();
mergeResult.addAll(existingItem.merge(newItem));
matchFound = true;
break;
}
}
/*
* If this existing item does not match any item in the newItems List then
* remove it from the existing items List.
*/
if (!matchFound) {
mergeResult.setStructuralChange(true);
mergeResult.addRemovedObject(existingItem);
existingIt.remove();
}
}
/*
* Add all the items left in newList to the existing container and change
* parent to new parent, if necessary
*/
for (T item : newListCopy) {
reparent(item, newParent);
existingList.add(item);
mergeResult.addUpdatedObject(item);
mergeResult.setStructuralChange(true);
}
return mergeResult;
}
@SuppressWarnings("unchecked")
private static void reparent(Object object, IPersistable newParent) {
if (newParent == null)
return;
if (object instanceof Reparentable) {
((Reparentable<IPersistable>) object).setParent(newParent);
} else {
throw new IllegalArgumentException("if newParent is non-null, the elements " + //$NON-NLS-1$
"of the list must implement the IReparentable interface."); //$NON-NLS-1$
}
}
/**
* Merges the properties of the newType into the existingType.
*
* @param existingType
* @param newType
* @return ListMergeResult indicating the operations performed as part of the
* merge.
*/
public static final ComplexMergeResult<?> mergeProperties(IEntity existingType, IEntity newType) {
ComplexMergeResult<Object> mergeResult = ComplexMergeResult.create(null);
Map<String, Serializable> existingProperties = existingType.getProperties();
Map<String, Serializable> newProperties = newType.getProperties();
/* Add / Update Properties from New Type */
for (Map.Entry<String, Serializable> entry : newProperties.entrySet()) {
String key = entry.getKey();
if (EXCLUDE_PROPERTIES.contains(key))
continue;
Serializable value = entry.getValue();
Serializable existingValue = existingProperties.get(key);
if (!value.equals(existingValue)) {
if (existingValue != null)
mergeResult.addRemovedObject(existingValue);
existingType.setProperty(key, value);
mergeResult.setStructuralChange(true);
}
}
/* Remove Properties from Old Type */
List<Map.Entry<String, ?>> entries = new ArrayList<Map.Entry<String, ?>>(existingProperties.entrySet());
for (Map.Entry<String, ?> entry : entries) {
String key = entry.getKey();
if (EXCLUDE_PROPERTIES.contains(key))
continue;
Object value = newProperties.get(key);
if (value == null) {
existingType.removeProperty(key);
mergeResult.addRemovedObject(entry.getValue());
mergeResult.setStructuralChange(true);
}
}
return mergeResult;
}
}