path: root/projects/net.wotonomy.persistence/src/main/java/net/wotonomy/control/EOEditingContext.java

/*
Wotonomy: OpenStep design patterns for pure Java applications.
Copyright (C) 2001 Michael Powers

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see http://www.gnu.org
*/

package net.wotonomy.control;

import java.lang.ref.WeakReference;
import java.util.Collection;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

import net.wotonomy.foundation.NSArray;
import net.wotonomy.foundation.NSDictionary;
import net.wotonomy.foundation.NSMutableArray;
import net.wotonomy.foundation.NSMutableDictionary;
import net.wotonomy.foundation.NSNotification;
import net.wotonomy.foundation.NSNotificationCenter;
import net.wotonomy.foundation.NSRunLoop;
import net.wotonomy.foundation.NSSelector;
import net.wotonomy.foundation.internal.WotonomyException;

// swing dependency for undo manager
//import javax.swing.undo.UndoManager;

/**
 * EOEditingContext provides transactional support for fetching, editing, and
 * committing changes made on a collection of objects to a parent object store.
 * <br>
 * <br>
 *
 * EOEditingContext is itself a subclass of EOObjectStore, and this means that
 * EOEditingContexts can use other EOEditingContexts as their parent. However,
 * there still must exist an EOObjectStore as the root of the editing hierarchy
 * that can maintain persistent state.
 *
 * @author michael@mpowers.net
 * @author $Author: cgruber $
 * @version $Revision: 894 $
 */
public class EOEditingContext extends EOObjectStore implements EOObserving {
	/**
	 * Key for the NSNotification posted after this editing context saves changes.
	 * Object of the notification will be this editing context, and user info will
	 * contain InsertedKey, UpdatedKey, and DeletedKey (keys are defined in
	 * EOObjectStore).
	 */
	public static final String EditingContextDidSaveChangesNotification = "EOEditingContextDidSaveChangesNotification";

	/**
	 * Key for the NSNotification posted after this editing context observes
	 * changes. Object of the notification will be this editing context, and user
	 * info will contain InsertedKey, UpdatedKey, InvalidatedKey, and DeletedKey
	 * (keys are defined in EOObjectStore), however the objects in the corresponding
	 * Lists will be the actual objects, not their ids.
	 */
	public static final String ObjectsChangedInEditingContextNotification = "EOObjectsChangedInEditingContextNotification";

	/**
	 * The default run loop ordering processes recent changes before delayed
	 * observers are notified and before dispatching the AWT event queue.
	 */
	public static int EditingContextFlushChangesRunLoopOrdering = 300000;

	private static NSSelector runLaterSelector = new NSSelector("flushRecentChanges", new Class[] { Object.class });

	private static EOObjectStore defaultParentObjectStore = null;
	private static double defaultFetchTimestampLag = 0;
	private static boolean retainsRegisteredObjects = true;

	private EOObjectStore parentStore;
	private WeakReference delegate;
	private WeakReference messageHandler;
	private List<WeakReference<EOEditingContext.Editor>> editorSet;
	private double fetchTimestamp;
	private boolean lockBeforeModify;
	private boolean propagateDeletesAfterEvent;
	private boolean stopValidationAfterError;
	private NSMutableArray<Object> insertedObjects;
	private NSMutableArray<Object> insertedObjectsBuffer;
	private NSArray<Object> insertedObjectsProxy;
	private NSMutableArray<Object> updatedObjects;
	private NSMutableArray<Object> updatedObjectsBuffer;
	private NSArray<Object> updatedObjectsProxy;
	private NSMutableArray<Object> deletedObjects;
	private NSMutableArray<Object> deletedObjectsBuffer;
	private NSArray<Object> deletedObjectsProxy;
	// TODO I think this is EOGlobalID but not certain
	private NSMutableArray<Object> deletedIDsBuffer;
	private NSMutableArray<Object> invalidatedObjectsBuffer;
	private NSMutableArray<EOGlobalID> invalidatedIDsBuffer;
	private Registrar registrar;
//    private UndoManager undoManager;

	// so we don't have to trouble EOObserverCenter
	private boolean ignoreChanges;

	// for delayed handling of processRecentChanges
	private boolean willRunLater;

	// for handling of notifications posted
	// while we're in the saveChanges method
	private boolean isInvalidating;

	// for i18n or other customization
	static protected String MessageChangeConflict = "Another user changed an object you are editing: ";

	/**
	 * Default constructor creates a new editing context that uses the default
	 * object store. If the default object store has not been set, an exception is
	 * thrown.
	 */
	public EOEditingContext() {
		this(defaultParentObjectStore());
	}

	/**
	 * Creates a new editing context that uses the specified object store as its
	 * parent object store.
	 */
	public EOEditingContext(EOObjectStore anObjectStore) {
		if (anObjectStore == null) {
			throw new IllegalArgumentException("A parent object store must be specified.");
		}

		parentStore = anObjectStore;
		delegate = null;
		messageHandler = null;
		editorSet = new LinkedList<>();
		fetchTimestamp = 0;
		lockBeforeModify = false;
		propagateDeletesAfterEvent = true;
		stopValidationAfterError = true;
		insertedObjects = new NSMutableArray();
		insertedObjectsBuffer = new NSMutableArray();
		insertedObjectsProxy = NSArray.arrayBackedByList(insertedObjects);
		updatedObjects = new NSMutableArray();
		updatedObjectsBuffer = new NSMutableArray();
		updatedObjectsProxy = NSArray.arrayBackedByList(updatedObjects);
		deletedObjects = new NSMutableArray();
		deletedObjectsBuffer = new NSMutableArray();
		deletedObjectsProxy = NSArray.arrayBackedByList(deletedObjects);
		deletedIDsBuffer = new NSMutableArray();
		invalidatedObjectsBuffer = new NSMutableArray();
		invalidatedIDsBuffer = new NSMutableArray();

		if (instancesRetainRegisteredObjects()) {
			registrar = new Registrar(this);
		} else {
			registrar = new WeakRegistrar(this);
		}

		ignoreChanges = false;
		willRunLater = false;
		isInvalidating = false;

		// create undo manager
		// TODO: this should be NSUndoManager
//        undoManager = new UndoManager();

		// register for notifications
		NSSelector handleNotification = new NSSelector("handleNotification", new Class[] { NSNotification.class });
		// any from parent store
		NSNotificationCenter.defaultCenter().addObserver(this, handleNotification, null, parentStore);
		// global id change from any
		NSNotificationCenter.defaultCenter().addObserver(this, handleNotification,
				EOGlobalID.GlobalIDChangedNotification, null);
//new net.wotonomy.ui.swing.NotificationInspector( null, parentStore );                
	}

	/**
	 * Registers the specified object as an editor for this context. The object is
	 * expected to implement EOEditingContext.Editor.
	 */
	public void addEditor(EOEditingContext.Editor anEditor) {
		if (anEditor == null)
			return;
		editorSet.add(new WeakReference<>(anEditor));
	}

	/**
	 * Returns a read-only List of objects associated with the object with the
	 * specified id for the specified property relationship, or may return a
	 * placeholder array that will defer the fetch until needed (aka an array
	 * fault). All objects must be registered in the specified editing context. This
	 * implementation calls to its parent object store's implementation if the
	 * requested source object is not registered in this editing context. The
	 * specified relationship key must produce a result of type Collection for the
	 * source object or an exception is thrown.
	 */
	@Override
	public NSArray arrayFaultWithSourceGlobalID(EOGlobalID aGlobalID, String aRelationshipKey,
			EOEditingContext aContext) {
		NSArray result = null;
		Object source = registrar.objectForGlobalID(aGlobalID);

		// if not registered in our context
		if (source == null) {
			// get the object registered into our context
			result = parentStore.arrayFaultWithSourceGlobalID(aGlobalID, aRelationshipKey, this);
		} else // source is registered in our context
		{
			// get existing value
			Object value;
			if (source instanceof EOKeyValueCoding) {
				value = ((EOKeyValueCoding) source).storedValueForKey(aRelationshipKey);
			} else // handle directly
			{
				value = EOKeyValueCodingSupport.storedValueForKey(source, aRelationshipKey);
			}

			if (value == null) {
				// do the same as if the source was null
				result = parentStore.arrayFaultWithSourceGlobalID(aGlobalID, aRelationshipKey, this);
			} else if (value instanceof NSArray) {
				result = (NSArray) value;
			} else // not NSArray
			if (value instanceof Collection) {
				// convert to NSArray
				result = new NSArray((Collection) value);
			} else {
				throw new WotonomyException(
						"Relationship key did not return a collection: " + aGlobalID + " : " + aRelationshipKey);
			}
		}

		// if our context is not the specified context
		if (aContext != this) {
			result = (NSArray) clone(this, result, aContext);
		}

		return result;
	}

	/**
	 * Returns a snapshot of the specified object as it existed when it was last
	 * read or committed to the parent object store.
	 */
	public NSDictionary committedSnapshotForObject(Object anObject) {
		byte[] snapshot = (byte[]) registrar.getCommitSnapshot(anObject);
		if (snapshot == null) {
			// this object not modified: take a current snapshot
			snapshot = takeSnapshot(anObject);
		}
		return convertSnapshotToDictionary(snapshot);
	}

	/**
	 * Returns a snapshot of the specified object as it existed before the edits
	 * triggered by the current event loop were processed.
	 */
	public NSDictionary currentEventSnapshotForObject(Object anObject) {
		byte[] result = (byte[]) registrar.getCurrentSnapshot(anObject);
		if (result == null) {
			return committedSnapshotForObject(anObject);
		}
		return convertSnapshotToDictionary(result);
	}

	/**
	 * Returns the delegate for this editing context, or null if no delegate has
	 * been set.
	 */
	public Object delegate() {
		if (delegate == null)
			return null;
		return delegate.get();
	}

	/**
	 * Deletes the specified object from this editing context. The editing context
	 * marks the object as deleted and will notify the parent store when changes are
	 * committed.
	 */
	public void deleteObject(Object anObject) {
		willChange();

		int i;
		// remove from added objects if necessary
		i = insertedObjects.indexOfIdenticalObject(anObject);
		if (i != NSArray.NotFound) {
			insertedObjects.removeObjectAtIndex(i);

			// if in the inserted objects buffer
			int index = insertedObjectsBuffer.indexOfIdenticalObject(anObject);
			if (index != NSArray.NotFound) {
				// remove from inserted objects buffer
				insertedObjectsBuffer.removeObjectAtIndex(index);
			}

			// now forget the object ever existed.
			forgetObject(anObject);

			// we're done
			return;
		} else // otherwise add to deleted objects list
		{
			deletedObjects.addObject(anObject);
		}

		// remove from updated objects if necessary
		i = updatedObjects.indexOfIdenticalObject(anObject);
		if (i != NSArray.NotFound) {
			updatedObjects.removeObjectAtIndex(i);
		}

		// add to buffer
		deletedObjectsBuffer.addObject(anObject);
		deletedIDsBuffer.addObject(globalIDForObject(anObject));
	}

	/**
	 * Returns a read-only List of all objects marked as deleted in this editing
	 * context.
	 */
	public NSArray deletedObjects() {
		return deletedObjectsProxy;
	}

	/**
	 * Called by child editing contexts when they no longer need to track the
	 * specified id. This implementation forwards the call to the parent store.
	 */
	@Override
	public void editingContextDidForgetObjectWithGlobalID(EOEditingContext aContext, EOGlobalID aGlobalID) {
		parentStore.editingContextDidForgetObjectWithGlobalID(aContext, aGlobalID);
	}

	/**
	 * Returns a read-only List of registered editors of this editing context.
	 */
	public NSArray editors() {
		NSMutableArray result = new NSMutableArray();
		Object o;
		Iterator<WeakReference<Editor>> i = editorSet.iterator();
		while (i.hasNext()) {
			o = i.next().get();
			if (o != null) {
				result.addObject(o);
			} else {
				i.remove();
			}
		}
		return result;
	}

	/*
	 * public static void encodeObjectWithCoder ( Object anObject, NSCoder aCoder )
	 * { throw new net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 */

	/**
	 * Returns the object for the specified id. If the object is registered in in
	 * this context but not in the specified context, this implementation will
	 * create a copy of the object and register it in the specified context.
	 * Otherwise it will forward the call to the parent object store.
	 */
	@Override
	public /* EOEnterpriseObject */ Object faultForGlobalID(EOGlobalID aGlobalID, EOEditingContext aContext) {
		Object result = registrar.objectForGlobalID(aGlobalID);

		// if not registered in our context
		if (result == null) {
			// get the object registered into our context
			result = parentStore.faultForGlobalID(aGlobalID, this);
		}

		// if our context is not the specified context
		if (aContext != this) {
			result = registerClone(aGlobalID, this, result, aContext);
		}

		return result;
	}

	/**
	 * Returns a fault representing an object of the specified entity type with
	 * values from the specified dictionary. This implementation calls
	 * faultForRawRow on the parent store.
	 */
	public Object faultForRawRow(Map aDictionary, String anEntityName) {
		return parentStore.faultForRawRow(aDictionary, anEntityName, this);
	}

	/**
	 * Returns a fault representing an object of the specified entity type with
	 * values from the specified dictionary. The fault should belong to the
	 * specified editing context. This implementation forwards the call to the
	 * parent store.
	 */
	@Override
	public /* EOEnterpriseObject */ Object faultForRawRow(Map aDictionary, String anEntityName,
			EOEditingContext aContext) {
		return parentStore.faultForRawRow(aDictionary, anEntityName, aContext);
	}

	/**
	 * Returns the fetch timestamp for this editing context.
	 */
	public double fetchTimestamp() {
		return fetchTimestamp;
	}

	/**
	 * Unregisters the specified object from this editing context, removing all
	 * references to it. Use this method to remove an object from the context
	 * without marking it for deletion.
	 */
	public void forgetObject(Object anObject) {
		EOGlobalID id = registrar.globalIDForObject(anObject);
		if (id == null) {
			System.err.println("EOEditingContext.forgetObject: not registered: " + anObject);
			return;
		}

		// unregister object
		registrar.forgetObject(anObject);

		// remove from all, inserted, updated, and deleted lists
		int index;
		index = updatedObjects.indexOfIdenticalObject(anObject);
		if (index != NSArray.NotFound) {
			updatedObjects.removeObjectAtIndex(index);
		}
		index = insertedObjects.indexOfIdenticalObject(anObject);
		if (index != NSArray.NotFound) {
			insertedObjects.removeObjectAtIndex(index);
			return;
		}
		index = deletedObjects.indexOfIdenticalObject(anObject);
		if (index != NSArray.NotFound) {
			deletedObjects.removeObjectAtIndex(index);
			return;
		}

		// notify parent context
		parentStore.editingContextDidForgetObjectWithGlobalID(this, id);
	}

	/**
	 * Returns the id for the specified object, or null if the object is not
	 * registered in this context.
	 */
	public EOGlobalID globalIDForObject(Object anObject) {
		return registrar.globalIDForObject(anObject);
	}

	/**
	 * Returns an array of ids for an array of objects.
	 */
	private NSArray globalIDsForObjects(List<Object> anObjectList) {
		NSMutableArray result = new NSMutableArray();
		for (Object obj : anObjectList) {
			result.add(globalIDForObject(obj));
		}
		return result;
	}

	/**
	 * Returns whether this editing context has changes that have not yet been
	 * committed to the parent object store.
	 */
	public boolean hasChanges() {
		if (updatedObjects.count() > 0)
			return true;
		if (insertedObjects.count() > 0)
			return true;
		if (deletedObjects.count() > 0)
			return true;
		return false;
	}

	/**
	 * Given a newly instantiated object, this method initializes its properties to
	 * values appropriate for the specified id. The object should already belong to
	 * the specified editing context. This method is called to populate faults. This
	 * implementation will try to apply the values from an object with a matching id
	 * in this editing context if possible, calling to the parent object store only
	 * if such an object is not found.
	 */
	@Override
	public void initializeObject(/* EOEnterpriseObject */ Object anObject, EOGlobalID aGlobalID,
			EOEditingContext aContext) {
		Object existingObject = registrar.objectForGlobalID(aGlobalID);

		// if not registered in our context
		if (existingObject == null) {
			// get the object registered into our context
			existingObject = parentStore.faultForGlobalID(aGlobalID, this);
		}

		if (aContext == this) {
			// initialize the object
			parentStore.initializeObject(/* (EOEnterpriseObject) */existingObject, aGlobalID, this);
		} else // ( aContext != this )
		{
			// translates child relationships
			copy(this, existingObject, aContext, anObject);
		}

		aContext.registrar.setCommitSnapshot(anObject, null);
		aContext.registrar.setCurrentSnapshot(anObject, null);
	}

	/**
	 * Inserts the specified object into this editing context. This implementation
	 * calls insertObjectWithGlobalID with an EOTemporaryGlobalID.
	 */
	public void insertObject(Object anObject) {
		insertObjectWithGlobalID(anObject, new EOTemporaryGlobalID());
	}

	/**
	 * Inserts the specified object into this editing context with the specified id,
	 * which is expected to be a temporary id.
	 */
	public void insertObjectWithGlobalID(Object anObject, EOGlobalID aGlobalID) {
		willChange();

		// if this object was marked for deletion
		int index = deletedObjects.indexOfIdenticalObject(anObject);
		if (index != NSArray.NotFound) {
			// don't need to re-register: just update the lists

			// remove from deleted list
			deletedObjects.removeObjectAtIndex(index);

			// if in the deleted ids buffer
			// TODO is this 
			index = deletedIDsBuffer.indexOfIdenticalObject(anObject);
			if (index != NSArray.NotFound) {
				// remove from deleted ids buffer
				deletedIDsBuffer.removeObjectAtIndex(index);
			}

			// if in the deleted objects buffer
			index = deletedObjectsBuffer.indexOfIdenticalObject(anObject);
			if (index != NSArray.NotFound) {
				// remove from deleted objects buffer
				deletedObjectsBuffer.removeObjectAtIndex(index);
			} else // not in the deleted objects buffer
			{
				// add to the inserted objects buffer
				insertedObjectsBuffer.addObject(anObject);
			}

			// we're done
			return;
		}

		// make sure object is not already in editing context
		if (objectForGlobalID(aGlobalID) != null) {
			throw new WotonomyException("Tried to insert but object was already registered:" + aGlobalID);
		}

		// register object
		recordObject(anObject, aGlobalID);

		// add to inserted list
		insertedObjects.addObject(anObject);
		// add to buffer
		insertedObjectsBuffer.addObject(anObject);
	}

	/**
	 * Returns a read-only List of the objects that have been inserted into this
	 * editing context.
	 */
	public NSArray insertedObjects() {
		return insertedObjectsProxy;
	}

	/**
	 * Turn all objects in this editing context into faults, so that they will be
	 * fetched the next time they are accessed, and calls
	 * invalidateObjectsWithGlobalIDs on the parent object store.
	 */
	@Override
	public void invalidateAllObjects() {
		// register change so processRecentChanges is called
		willChange();

		invalidateAllObjectsQuietly();

		// post notification
		NSNotificationCenter.defaultCenter()
				.postNotification(new NSNotification(InvalidatedAllObjectsInStoreNotification, this));
	}

	/**
	 * Only refaults all objects, does not notify will change nor post notification,
	 * but does call parent store. Called by invalidateAllObjects() and
	 * handleNotification().
	 */
	private void invalidateAllObjectsQuietly() {
		// remember the ids
		NSMutableArray ids = new NSMutableArray(registrar.registeredGlobalIDs());

		// track of discarded IDs (from inserted objects)
		NSMutableArray discardedIDs = new NSMutableArray();

		// refault all objects
		EOGlobalID id;
		Object o;
		Enumeration<EOGlobalID> e = ids.objectEnumerator();
		while (e.hasMoreElements()) {
			id = e.nextElement();
			o = objectForGlobalID(id);

			// some objects may have been manually discarded
			if (o != null) {
				// don't refault newly inserted objects
				if (insertedObjects.indexOfIdenticalObject(o) == NSArray.NotFound) {
					refaultObject(o, id, this);
				} else {
					// discard inserted objects
					forgetObject(o);
					discardedIDs.add(id);
				}
				invalidatedObjectsBuffer.add(o);
			}
			invalidatedIDsBuffer.add(id);
		}
		ids.removeAll(discardedIDs);

		// call to parent store (should call this after posting instead?)
		isInvalidating = true;
		parentStore.invalidateObjectsWithGlobalIDs(ids);
		isInvalidating = false;
	}

	/**
	 * Turns the objects with the specified ids into faults, so that they will be
	 * fetched the next time they are accessed, and forwards the call to the parent
	 * object store.
	 */
	@Override
	public void invalidateObjectsWithGlobalIDs(List anArray) {
		// register change so processRecentChanges is called
		willChange();

		// call to parent to invalidate objects
		parentStore.invalidateObjectsWithGlobalIDs(anArray);

		Object o;
		EOGlobalID id;
		Iterator<EOGlobalID> it = anArray.iterator();
		while (it.hasNext()) {
			id = it.next();
			if (id != null) {
				o = objectForGlobalID(id);
				if (o != null) {
					Object result = notifyDelegate("editingContextShouldInvalidateObject",
							new Class[] { EOEditingContext.class, Object.class, EOGlobalID.class },
							new Object[] { this, o, id });
					if ((result == null) || (Boolean.TRUE.equals(result))) {
						// refault the object
						refaultObject(o, id, this);
						invalidatedObjectsBuffer.add(o);
						invalidatedIDsBuffer.add(id);
					}
				}
			} else {
				throw new WotonomyException("Attempted to invalidate a null global id: " + anArray);
			}
		}

	}

	/*
	 * public boolean invalidatesObjectsWhenFinalized ( ) { throw new
	 * net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 * 
	 * public boolean invalidatesObjectsWhenFreed ( ) { throw new
	 * net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 */
	/**
	 * Returns whether the object referenced by the specified id is locked. This
	 * implementation simply forwards the call to the parent object store.
	 */
	@Override
	public boolean isObjectLockedWithGlobalID(EOGlobalID aGlobalID, EOEditingContext aContext) {
		return parentStore.isObjectLockedWithGlobalID(aGlobalID, aContext);
	}

	/*
	 * public void lock () { throw new
	 * net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 */
	/**
	 * Locks the specified object in this editing context by calling
	 * lockObjectWithGlobalID on the parent store.
	 */
	public void lockObject(Object anObject) {
		parentStore.lockObjectWithGlobalID(globalIDForObject(anObject), this);
	}

	/**
	 * Locks the object referenced by the specified id in the specified editing
	 * context. This implementation simply forwards the call to the parent object
	 * store.
	 */
	@Override
	public void lockObjectWithGlobalID(EOGlobalID aGlobalID, EOEditingContext aContext) {
		parentStore.lockObjectWithGlobalID(aGlobalID, aContext);
	}

	/**
	 * Returns whether this editing context attempts to lock objects when they are
	 * first modified.
	 */
	public boolean locksObjectsBeforeFirstModification() {
		return lockBeforeModify;
	}

	/**
	 * Returns the message handler for this editing context, or null if no message
	 * handler has been set.
	 */
	public Object messageHandler() {
		if (messageHandler == null)
			return null;
		return messageHandler.get();
	}

	/**
	 * Returns the object registered in this editing context for the specified id,
	 * or null if that id is not registered.
	 */
	public Object objectForGlobalID(EOGlobalID aGlobalID) {
		return registrar.objectForGlobalID(aGlobalID);
	}

	/**
	 * Returns a read-only List of objects associated with the object with the
	 * specified id for the specified property relationship. This method may not
	 * return an array fault because array faults call this method to fetch on
	 * demand. All objects must be registered the specified editing context. The
	 * specified relationship key must produce a result of type Collection for the
	 * source object or an exception is thrown.
	 */
	@Override
	public NSArray objectsForSourceGlobalID(EOGlobalID aGlobalID, String aRelationshipKey, EOEditingContext aContext) {
//System.out.println( "EOEditingContext.objectsForSourceGlobalID: " 
//+ aGlobalID + " : " + aRelationshipKey );        

		NSArray result = null;

		if (aContext == this) {
			throw new WotonomyException("Assert failed: calling objectsForSourceGlobalID on ourself.");
		}
		Object source = registrar.objectForGlobalID(aGlobalID);

		// if not registered in our context
		if (source == null) {
			// get the object registered into our context
			result = parentStore.objectsForSourceGlobalID(aGlobalID, aRelationshipKey, this);
		} else // source is registered in our context
		{
			// get existing value
			Object value;
			if (source instanceof EOKeyValueCoding) {
				value = ((EOKeyValueCoding) source).storedValueForKey(aRelationshipKey);
			} else // handle directly
			{
				value = EOKeyValueCodingSupport.storedValueForKey(source, aRelationshipKey);
			}

			// if we don't have a valid value on our object
			if ((value == null) || ((value instanceof ArrayFault) && (!((ArrayFault) value).isFetched()))) {
				// do the same as if the source was null
				result = parentStore.objectsForSourceGlobalID(aGlobalID, aRelationshipKey, this);

				// set our value since we have it
				if (source instanceof EOKeyValueCoding) {
					((EOKeyValueCoding) source).takeStoredValueForKey(result, aRelationshipKey);
				} else // handle directly
				{
					EOKeyValueCodingSupport.takeStoredValueForKey(source, result, aRelationshipKey);
				}
			} else if ((value instanceof ArrayFault) && (!((ArrayFault) value).isFetched())) {
				// do the same as if the source was null
				result = parentStore.objectsForSourceGlobalID(aGlobalID, aRelationshipKey, this);
			} else if (value instanceof NSArray) {
				result = (NSArray) value;
			} else // not NSArray
			if (value instanceof Collection) {
				// convert to NSArray
				result = new NSArray((Collection<?>) value);
			} else {
				throw new WotonomyException(
						"Relationship key did not return a collection: " + aGlobalID + " : " + aRelationshipKey);
			}
		}

		// if our context is not the specified context
		if (aContext != this) {
			result = (NSArray) clone(this, result, aContext);
		}

		return result;
	}

	/**
	 * Returns a read-only List of objects the meet the criteria of the supplied
	 * specification. This method simply calls objectsWithFetchSpecification on this
	 * editing context with this editing context as the parameter.
	 */
	public NSArray objectsWithFetchSpecification(EOFetchSpecification aFetchSpec) {
		return objectsWithFetchSpecification(aFetchSpec, this);
	}

	/**
	 * Returns a read-only List of objects the meet the criteria of the supplied
	 * specification. Faults are not allowed in the array. If any objects are
	 * already fetched, they should not be refetched. All objects should belong to
	 * the specified editing context. This implementation forwards the call to the
	 * parent object store, which will register each object in the specified editing
	 * context only if it does not already exist.
	 */
	@Override
	public NSArray objectsWithFetchSpecification(EOFetchSpecification aFetchSpec, EOEditingContext aContext) {
		if (aContext == this) {
			Object result = notifyDelegate("editingContextShouldFetchObjects",
					new Class[] { EOEditingContext.class, EOFetchSpecification.class },
					new Object[] { aContext, aFetchSpec });
			if (result instanceof NSArray)
				return (NSArray) result;
		}
		return parentStore.objectsWithFetchSpecification(aFetchSpec, aContext);
	}

	/**
	 * Returns the parent object store for this editing context. The result will not
	 * be null.
	 */
	public EOObjectStore parentObjectStore() {
		return parentStore;
	}

	/**
	 * Updates the inserted, updated, and deleted objects lists, and posts
	 * notifications about which objects have been changed. This method is called at
	 * the end of an event loop in which objects were modified. This method is
	 * additionally called by saveChanges() so that any changes in the same event
	 * loop will be processed correctly before calling to the parent object store.
	 * This implementation updates those lists immediately, but only posts
	 * notifications when this method is called.
	 */
	public void processRecentChanges() { // System.out.println( "EOEditingContext.processRecentChanges: " +
											// invalidatedObjectsBuffer );

		/*
		 * This implementation actually updates those lists immediately, but keeps a
		 * separate buffer of changes in the current event loop for the purposes of
		 * posting a notification. NOTE: to reenable buffering, uncomment lines from
		 * this method body and reenable the RecentChangesObserver in the constructor.
		 */

		// broadcast ObjectsChangedInStoreNotification
		// for the benefit of child editing contexts

		boolean postStoreInfo = (insertedObjectsBuffer.size() + updatedObjectsBuffer.size() + deletedIDsBuffer.size()
				+ invalidatedIDsBuffer.size() > 0);

		NSMutableDictionary<String, NSArray> storeInfo = new NSMutableDictionary<>();
		if (postStoreInfo) {
			storeInfo.setObjectForKey(globalIDsForObjects(insertedObjectsBuffer),
					// globalIDsForObjects( insertedObjects ),
					EOObjectStore.InsertedKey);
			storeInfo.setObjectForKey(globalIDsForObjects(updatedObjectsBuffer),
					// globalIDsForObjects( updatedObjects ),
					EOObjectStore.UpdatedKey);
			storeInfo.setObjectForKey(new NSArray((Collection<?>) deletedIDsBuffer),
					// globalIDsForObjects( deletedObjects ),
					EOObjectStore.DeletedKey);
			storeInfo.setObjectForKey(new NSArray((Collection<?>) invalidatedIDsBuffer), EOObjectStore.InvalidatedKey);
		}

		// broadcast ObjectsChangedInEditingContextNotification
		// for the benefit of attached display groups

		boolean postContextInfo = (insertedObjectsBuffer.size() + updatedObjectsBuffer.size()
				+ deletedObjectsBuffer.size() + invalidatedObjectsBuffer.size() > 0);

		NSMutableDictionary<String, NSArray> contextInfo = new NSMutableDictionary<>();

		if (postContextInfo) {

			contextInfo.setObjectForKey(new NSArray((Collection<?>) insertedObjectsBuffer),
					// new NSArray( (Collection) insertedObjects ),
					EOObjectStore.InsertedKey);
			contextInfo.setObjectForKey(new NSArray((Collection<?>) updatedObjectsBuffer),
					// new NSArray( (Collection) updatedObjects ),
					EOObjectStore.UpdatedKey);
			contextInfo.setObjectForKey(new NSArray((Collection<?>) deletedObjectsBuffer),
					// new NSArray( (Collection) deletedObjects ),
					EOObjectStore.DeletedKey);
			contextInfo.setObjectForKey(new NSArray((Collection<?>) invalidatedObjectsBuffer),
					EOObjectStore.InvalidatedKey);
		}

		// update the current snapshots

		Object o;
		Iterator<Object> it;
		it = insertedObjectsBuffer.iterator();
		while (it.hasNext()) {
			o = it.next();
			registrar.setCurrentSnapshot(o, takeSnapshot(o));
		}
		it = updatedObjectsBuffer.iterator();
		while (it.hasNext()) {
			o = it.next();
			registrar.setCurrentSnapshot(o, takeSnapshot(o));
		}

		// clear buffers

		insertedObjectsBuffer.removeAllObjects();
		updatedObjectsBuffer.removeAllObjects();
		deletedObjectsBuffer.removeAllObjects();
		deletedIDsBuffer.removeAllObjects();
		invalidatedObjectsBuffer.removeAllObjects();
		invalidatedIDsBuffer.removeAllObjects();

		// post notifications (does order matter?)

		if (postStoreInfo) {
			NSNotificationCenter.defaultCenter()
					.postNotification(new NSNotification(ObjectsChangedInStoreNotification, this, storeInfo));
		}

		if (postContextInfo) {
			NSNotificationCenter.defaultCenter().postNotification(
					new NSNotification(ObjectsChangedInEditingContextNotification, this, contextInfo));
		}

	}

	/**
	 * Returns whether this editing context propagates deletes immediately after the
	 * event that triggered the delete. Otherwise, propagation occurs only before
	 * commit.
	 */
	public boolean propagatesDeletesAtEndOfEvent() {
		return propagateDeletesAfterEvent;
	}

	/**
	 * Registers the specified object in this editing context for the specified id.
	 * This method is called by an object store when fetching objects for a display
	 * group, or when objects are inserted into a display group. This implementation
	 * will re-register the object under the new id if it is already registered
	 * under a different id.
	 */
	public void recordObject(Object anObject, EOGlobalID aGlobalID) {
		// find state for re-registration
		boolean inserted = false;
		boolean updated = false;
		boolean deleted = false;

		// is the object already registered?
		EOGlobalID existingID = globalIDForObject(anObject);
		if (existingID != null) {
			// remember object state
			int index;
			index = insertedObjects.indexOfIdenticalObject(anObject);
			if (index != NSArray.NotFound)
				inserted = true;
			index = updatedObjects.indexOfIdenticalObject(anObject);
			if (index != NSArray.NotFound)
				updated = true;
			index = deletedObjects.indexOfIdenticalObject(anObject);
			if (index != NSArray.NotFound)
				deleted = true;
			// forget the object
			forgetObject(anObject);
		}

		// is the global id already in use?
		Object existingObject = objectForGlobalID(aGlobalID);
		if (existingObject != null) {
			// forget it (don't worry about state?)
			forgetObject(existingObject);
		}

		registrar.registerObject(anObject, aGlobalID);

		// restore state if necessary
		if (inserted)
			insertedObjects.addObject(anObject);
		if (updated)
			updatedObjects.addObject(anObject);
		if (deleted)
			deletedObjects.addObject(anObject);
	}

	/**
	 * Undoes the last undo operation.
	 */
	public void redo() {
		// TODO: not supported yet
		throw new UnsupportedOperationException("Not implemented yet.");
	}

	/**
	 * Refaults this editing context, turning all unmodified objects into faults.
	 * This implementation calls editingContextWillSaveChanges() on all editors, and
	 * then calls refaultObjects().
	 */
	public void refault() {
		fireWillSaveChanges();
		refaultObjects();
	}

	/**
	 * Refaults the specified object, turning it into a fault for the specified
	 * global id in the specified context.
	 */
	@Override
	public void refaultObject(Object anObject, EOGlobalID aGlobalID, EOEditingContext aContext) {
		aContext.registrar.setCurrentSnapshot(anObject, null);

		ignoreChanges = true;
		parentStore.refaultObject(anObject, aGlobalID, aContext);
		ignoreChanges = false;

		// remove from updated objects if necessary
		int i = updatedObjects.indexOfIdenticalObject(anObject);
		if (i != NSArray.NotFound) {
			updatedObjects.removeObjectAtIndex(i);
		}

		// add to invalidated notification queue
		invalidatedObjectsBuffer.addObject(anObject);
		invalidatedIDsBuffer.addObject(aGlobalID);
	}

	/**
	 * Turns all unmodified objects into faults, calling processRecentChanges() and
	 * then refaultObject() for each unmodified object.
	 */
	public void refaultObjects() {
		// is this call really needed?
		// processRecentChanges();

		Object o;
		EOGlobalID id;
		Iterator<Object> it = registeredObjects().iterator();
		while (it.hasNext()) {
			o = it.next();
			if ((updatedObjects.indexOfIdenticalObject(o) == NSArray.NotFound)
					&& (insertedObjects.indexOfIdenticalObject(o) == NSArray.NotFound)
					&& (deletedObjects.indexOfIdenticalObject(o) == NSArray.NotFound)) {
				id = globalIDForObject(o);
				refaultObject(o, id, this);
			}
		}
	}

	/**
	 * Calls editingContextWillSaveChanges() on all editors, and then calls
	 * invalidateAllObjects().
	 */
	public void refetch() {
		fireWillSaveChanges();
		invalidateAllObjects();
	}

	/**
	 * Returns a read-only List of all objects registered in this editing context.
	 */
	public NSArray registeredObjects() {
		return registrar.registeredObjects();
	}

	/**
	 * Unregisters the specified editor with this editing context.
	 */
	public void removeEditor(Object anObject) {
		if (anObject == null)
			return;

		Object o;
		Iterator<WeakReference<Editor>> i = editorSet.iterator();
		while (i.hasNext()) {
			o = i.next().get();
			if ((o == null) || (o == anObject)) {
				i.remove();
			}
		}
	}

	/**
	 * Unregisters all objects from this editing context, and resets the fetch
	 * timestamp.
	 */
	public void reset() {
		Iterator<Object> it = registeredObjects().iterator();
		while (it.hasNext()) {
			forgetObject(it.next());
		}
		fetchTimestamp = 0; // FIXME: reset timestamp properly
	}

	/**
	 * Reverts the objects in this editing context to their original state. Calls
	 * editingContextWillSaveChanges on all editors, discards all inserted objects,
	 * restores deleted objects, and applies the fetch snapshot to all registered
	 * objects.
	 */
	public void revert() {
		willChange();
		fireWillSaveChanges();

		Iterator<Object> it;

		// forget inserted objects
		it = new NSArray(insertedObjects).iterator();
		while (it.hasNext()) {
			forgetObject(it.next());
		}

		Object o;
		byte[] snapshot;

		// re-initialize updated objects
		it = new NSArray(updatedObjects).iterator();
		while (it.hasNext()) {
			o = it.next();
			snapshot = (byte[]) registrar.getCommitSnapshot(o);
			if (snapshot != null) {
				applySnapshot(snapshot, o);
			}
			registrar.setCommitSnapshot(o, null);
			updatedObjectsBuffer.addObject(o);
		}

		// re-initialize deleted objects
		it = new NSArray(deletedObjects).iterator();
		while (it.hasNext()) {
			o = it.next();
			snapshot = (byte[]) registrar.getCommitSnapshot(o);
			if (snapshot != null) {
				applySnapshot(snapshot, o);
			}
			registrar.setCommitSnapshot(o, null);
			updatedObjectsBuffer.addObject(o);
		}

		// reset lists
		insertedObjects.removeAllObjects(); // unneccessary?
		deletedObjects.removeAllObjects();
		updatedObjects.removeAllObjects();

		// post notification
		processRecentChanges();
	}

	/**
	 * Returns the root object store, which is the parent of all parent object
	 * stores of this editing context.
	 */
	public EOObjectStore rootObjectStore() {
		EOObjectStore parent = parentObjectStore();
		while (parent instanceof EOEditingContext) {
			parent = ((EOEditingContext) parent).parentObjectStore();
		}
		return parent;
	}

	/**
	 * Calls editingContextWillSaveChanges on all editors, and commits all changes
	 * in this editing context to the parent editing context by calling
	 * saveChangesInEditingContext to the parent. Then posts
	 * EditingContextDidSaveChangeNotification.
	 */
	public void saveChanges() {
//System.out.println( "EOEditingContext.saveChanges: " + this );        
		willChange();

		// process any changes
		processRecentChanges();

		// set up user info for notification to be posted.
		NSMutableDictionary<String, NSArray> userInfo = new NSMutableDictionary<>();
		userInfo.setObjectForKey(new NSArray((Collection<?>) insertedObjects), EOObjectStore.InsertedKey);
		userInfo.setObjectForKey(new NSArray((Collection<?>) updatedObjects), EOObjectStore.UpdatedKey);
		userInfo.setObjectForKey(new NSArray((Collection<?>) deletedObjects), EOObjectStore.DeletedKey);

		// notify the editors
		fireWillSaveChanges();

		// notify the delegate
		notifyDelegate("editingContextWillSaveChanges", new Class[] { EOEditingContext.class }, new Object[] { this });

		// needed for notification handling
		isInvalidating = true;
		try {
			// ask parent to save us
			parentStore.saveChangesInEditingContext(this);
		} catch (RuntimeException e) {
			// unset save flag and rethrow
			isInvalidating = false;
			throw e;
		}
		isInvalidating = false;

		// no exceptions: proceed!

		Object o;
		Iterator<Object> it;

		// update the committed snapshots
		it = insertedObjects.iterator();
		while (it.hasNext()) {
			o = it.next();
			registrar.setCommitSnapshot(o, null);
			registrar.setCurrentSnapshot(o, null);
		}
		it = updatedObjects.iterator();
		while (it.hasNext()) {
			o = it.next();
			registrar.setCommitSnapshot(o, null);
			registrar.setCurrentSnapshot(o, null);
		}

		// clear the lists
		updatedObjects.removeAllObjects();
		insertedObjects.removeAllObjects();
		it = new NSArray(deletedObjects()).iterator();
		while (it.hasNext()) { // parent is doing this as well?
			forgetObject(it.next());
		}

		// post notification
		NSNotificationCenter.defaultCenter()
				.postNotification(new NSNotification(EditingContextDidSaveChangesNotification, this, userInfo));
	}

	/**
	 * Commits all changes in the specified editing context to this one. Called by
	 * child editing contexts in their saveChanges() method.
	 */
	@Override
	public void saveChangesInEditingContext(EOEditingContext aContext) {
		Object o;
		Iterator<Object> it;

		// process deletes
		List<Object> deletes = new NSArray(aContext.deletedObjects());
		it = deletes.iterator();
		while (it.hasNext()) {
			o = it.next();
			EOGlobalID id = aContext.globalIDForObject(o);
			Object localVersion = objectForGlobalID(id);
			if (localVersion == null) {
				// make a local copy and register it
				localVersion = registerClone(id, aContext, o, this);
				if (localVersion == null) {
					throw new WotonomyException("Deleted object could not be serialized: " + id + " : " + o);
				}
			} else // we have a local version, copy changes
			{
				copy(aContext, o, this, localVersion);
				// copy marks the object as updated: will be on both lists
			}
			// delete our copy -- marks context as changed
			deleteObject(localVersion);
		}

		// process inserts - all inserts are new objects
		List<Object> inserts = new NSArray(aContext.insertedObjects());
		it = inserts.iterator();
		while (it.hasNext()) {
			o = it.next();
			// make a local copy and register it
			EOGlobalID id = aContext.globalIDForObject(o);
			willChange(); // need to mark editing context as changed
			Object localVersion = registerClone(id, aContext, o, this);
			if (localVersion == null) {
				throw new WotonomyException("Inserted object could not be serialized: " + o);
			}
			// insert our copy manually so a new id is not generated
			insertedObjects.addObject(localVersion);
			insertedObjectsBuffer.addObject(localVersion);
		}

		// process updates
		List<Object> updates = new NSArray(aContext.updatedObjects());
		it = updates.iterator();
		while (it.hasNext()) {
			willChange(); // need to mark editing context as changed
			o = it.next();
			EOGlobalID id = aContext.globalIDForObject(o);
			Object localVersion = objectForGlobalID(id);
			if (localVersion == null) {
				// make a local copy and register it
				localVersion = registerClone(id, aContext, o, this);
				if (localVersion == null) {
					throw new WotonomyException("Updated object could not be serialized: " + id + " : " + o);
				}
				if (id.isTemporary()) {
					// mark this object as inserted
					insertedObjects.addObject(localVersion);
					insertedObjectsBuffer.addObject(localVersion);
				} else {
					// mark this object as updated
					updatedObjects.addObject(localVersion);

					// notify of update only if not on deleted list
					if (deletedObjectsBuffer.indexOfIdenticalObject(localVersion) == NSArray.NotFound) {
						updatedObjectsBuffer.addObject(localVersion);
					}
				}
			} else // we have a local version, copy changes
			{
				copy(aContext, o, this, localVersion);
				// copy marks the object as updated
			}
		}

	}

	/**
	 * Sets the delegate for this editing context. Note: this implementation retains
	 * only a weak reference to the specified object.
	 */
	public void setDelegate(Object anObject) {
		if (anObject == null)
			delegate = null;
		delegate = new WeakReference<>(anObject);
	}

	/**
	 * Sets the fetch timestamp for this editing context.
	 */
	public void setFetchTimestamp(double aDouble) {
		fetchTimestamp = aDouble;
	}

	/*
	 * public void setInvalidatesObjectsWhenFinalized ( boolean invalidatesObjects )
	 * { throw new net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 * 
	 * public void setInvalidatesObjectsWhenFreed ( boolean invalidatesObjects ) {
	 * throw new net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 */
	/**
	 * Sets whether this editing context attempts to lock objects when they are
	 * first modified. Default is false.
	 */
	public void setLocksObjectsBeforeFirstModification(boolean locksObjects) {
		lockBeforeModify = locksObjects;
	}

	/**
	 * Sets the message handler for this editing context. Note: this implementation
	 * retains only a weak reference to the specified object.
	 */
	public void setMessageHandler(Object anObject) {
		if (anObject == null)
			messageHandler = null;
		messageHandler = new WeakReference(anObject);
	}

	/**
	 * Sets whether this editing context propagates deletes immediately after the
	 * event that triggered the delete. Otherwise, propagation occurs only before
	 * commit. Default is true.
	 */
	public void setPropagatesDeletesAtEndOfEvent(boolean propagatesDeletes) {
		propagateDeletesAfterEvent = propagatesDeletes;
	}

	/*
	 * public void setSharedEditingContext ( EOSharedEditingContext
	 * aSharedEditingContext ) { throw new
	 * net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 */
	/**
	 * Sets whether validation is stopped after the first error occurs. Otherwise,
	 * validation will continue for all other objects. Default is true.
	 */
	public void setStopsValidationAfterFirstError(boolean stopsValidation) {
		stopValidationAfterError = stopsValidation;
	}

	/**
	 * Sets the undo manager to be used for this context. Note: This is currently
	 * javax.swing.undo.UndoManager, until we have a implementation of
	 * NSUndoManager.
	 */
	/*
	 * public void setUndoManager ( UndoManager anUndoManager ) { undoManager =
	 * anUndoManager; }
	 */
	/*
	 * public EOSharedEditingContext sharedEditingContext () { throw new
	 * net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 */
	/**
	 * Returns whether validation is stopped after the first error occurs.
	 * Otherwise, validation will continue for all other objects.
	 */
	public boolean stopsValidationAfterFirstError() {
		return stopValidationAfterError;
	}

	/**
	 * Reverts the last change on the undo stack.
	 */
	public void undo() {
		// TODO: not supported yet
		throw new UnsupportedOperationException("Not implemented yet.");
	}

	/*
	 * public NSUndoManager undoManager () { throw new
	 * net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 */
	/**
	 * public void unlock () { throw new net.wotonomy.util.WotonomyException("Not
	 * implemented yet."); }
	 */
	/**
	 * Returns a read-only list of all objects marked as modified, but not inserted
	 * or deleted, in this editing context.
	 */
	public NSArray updatedObjects() {
		return updatedObjectsProxy;
	}

	/**
	 * Notify editors of changes.
	 */
	private void fireWillSaveChanges() {
		Object o = null;
		Iterator<WeakReference<EOEditingContext.Editor>> i = editors().iterator();
		while (i.hasNext()) {
			try {
				o = i.next();
				NSSelector.invoke("editingContextWillSaveChanges", new Class[] { EOEditingContext.class }, o, this);
			} catch (NoSuchMethodException e) {
				// ignore: not implemented
			} catch (Exception exc) {
				// log to standard error
				System.err.println("Error while notifying editor of pending save: " + o);
				exc.printStackTrace();
			}
		}
	}

	/**
	 * Handles notifications from parent store, looking for
	 * InvalidatedAllObjectsInStoreNotification and
	 * ObjectsChangedInStoreNotification. The former causes all objects in this
	 * store to be invalidated. The latter refaults the invalidated ids, merges
	 * changes from the updated ids, and forgets the deleted ids, then posts a
	 * ObjectsChangedInStoreNotification. Note: This method is not in the public
	 * specification.
	 */
	public void handleNotification(NSNotification aNotification) { // System.out.println( "EOEditingContext: " + this +
																	// " : " + aNotification );

		willChange();
		if (InvalidatedAllObjectsInStoreNotification.equals(aNotification.name())) {
			refaultObjects();

			// relay notification
			NSNotificationCenter.defaultCenter()
					.postNotification(new NSNotification(InvalidatedAllObjectsInStoreNotification, this));
		} else if (EOGlobalID.GlobalIDChangedNotification.equals(aNotification.name())) {
			NSDictionary<EOGlobalID, ?> userInfo = aNotification.userInfo();

			// if any keys in userInfo are registered ids,
			// re-register with new permanent values.

			Object o;
			EOGlobalID id;
			Enumeration<EOGlobalID> e = userInfo.keyEnumerator();
			while (e.hasMoreElements()) {
				id = e.nextElement();
				o = objectForGlobalID(id);
				if (o != null) {
					// record object is assumed to handle key updates
					recordObject(o, (EOGlobalID) userInfo.objectForKey(id));
				}
			}
		} else if (EOObjectStore.ObjectsChangedInStoreNotification.equals(aNotification.name())) {
			// System.out.println( "EOEditingContext.handleNotification: " + aNotification +
			// " : " + this );
			// post so child contexts are notified
			willChange();

			Object o;
			EOGlobalID id;
			Enumeration<EOGlobalID> e;
			NSDictionary<String, NSArray<EOGlobalID>> userInfo = (NSDictionary<String, NSArray<EOGlobalID>>) aNotification.userInfo();

			// inserted objects are ignored

			// existing deleted objects are removed
			NSArray<EOGlobalID> deletes = userInfo.objectForKey(EOObjectStore.DeletedKey);
			e = deletes.objectEnumerator();
			while (e.hasMoreElements()) {
				id = e.nextElement();
				o = objectForGlobalID(id);
				if (o != null) {
					// System.out.println( "EOEditingContext: deleted: " + id );
					forgetObject(o);
					deletedObjectsBuffer.addObject(o);
					deletedIDsBuffer.addObject(id);
				}
			}

			// existing updated objects are merged
			NSArray<EOGlobalID> updates = userInfo.objectForKey(EOObjectStore.UpdatedKey);
			e = updates.objectEnumerator();
			while (e.hasMoreElements()) {
				id = e.nextElement();
				o = objectForGlobalID(id);
				if (o != null) {
					// System.out.println( "EOEditingContext: updated: " + id );
					if (updatedObjects // only update if unchanged
							.indexOfIdenticalObject(o) == NSArray.NotFound) {
						refaultObject(o, id, this);
						updatedObjectsBuffer.addObject(o);
					} else {
						// notify user and/or merge
						handleUpdateConflict(id, o);
					}
				}
			}

			// existing invalidated objects are refaulted
			NSArray<EOGlobalID> invalidates = userInfo.objectForKey(EOObjectStore.InvalidatedKey);
			e = invalidates.objectEnumerator();
			while (e.hasMoreElements()) {
				id = e.nextElement();
				o = objectForGlobalID(id);
				if (o != null) {
					if (updatedObjects // only invalidate if unchanged
							.indexOfIdenticalObject(o) == NSArray.NotFound) {
						refaultObject(o, id, this);
					} else {
						// notify user and/or merge
						handleUpdateConflict(id, o);
					}
					if (invalidatedObjectsBuffer.indexOfIdenticalObject(o) == NSArray.NotFound) {
						invalidatedObjectsBuffer.addObject(o);
					}
					if (invalidatedIDsBuffer.indexOfIdenticalObject(id) == NSArray.NotFound) {
						invalidatedIDsBuffer.addObject(id);
					}
				}
			}

		}
	}

	/**
	 * Called by handleNotification to resolve the case where we have received
	 * notification that another user or context has updated an object that is
	 * currently marked as edited in this context. This implementation first asks
	 * the delegate if it should merge. If true or no delegate, the changes are
	 * merged. True or false, the delegate is then sent
	 * editingContextDidMergeChanges.
	 */
	private void handleUpdateConflict(EOGlobalID anID, Object anObject) {
		// if we're causing the invalidation, ignore
		// (this is probably better handled by the caller...)
		if (isInvalidating) {
			ignoreChanges = true;
			parentStore.refaultObject(anObject, anID, this);
			ignoreChanges = false;
			return;
		}

		Boolean result = (Boolean) notifyDelegate("editingContextShouldMergeChangesForObject",
				new Class[] { EOEditingContext.class, Object.class }, new Object[] { this, anObject });

		if ((result == null) || (Boolean.TRUE.equals(result))) {
			// do merge
			mergeExternalChanges(anID, anObject);
		} else // Boolean.FALSE
		{
			// do nothing: don't lose the user's changes
		}

		// notify merge did happen
		notifyDelegate("editingContextDidMergeChanges", new Class[] { EOEditingContext.class }, new Object[] { this });
	}

	/**
	 * For the currently modified object with the specified global id, this method
	 * merges changes with the updated version in the parent object store. This
	 * implementation looks at the fetch snapshot to determine which changes where
	 * made by the user, fetches the updated version of the object, and then
	 * determine what external changes were made. If the changes do not overlap, the
	 * original changes are applied to the updated version. If there is a conflict,
	 * notifies the user of the conflict.
	 */
	private boolean mergeExternalChanges(EOGlobalID anID, Object anObject) {
		try {
			Iterator i;
			Object key;

			// get fetch snapshot
			Map fetchSnapshot = committedSnapshotForObject(anObject);

			// get current snapshot
			Map currentSnapshot = currentEventSnapshotForObject(anObject);

			// diff against fetch snapshot
			Map currentDiff = new HashMap();
			i = currentSnapshot.keySet().iterator();
			while (i.hasNext()) {
				key = i.next();
				if (!currentSnapshot.get(key).equals(fetchSnapshot.get(key))) {
					currentDiff.put(key, currentSnapshot.get(key));
				}
			}

			// refault
			ignoreChanges = true;
			parentStore.refaultObject(anObject, anID, this);
			ignoreChanges = false;

			// get updated snapshot
			Map updatedSnapshot = convertSnapshotToDictionary(takeSnapshot(anObject));

			// diff against fetch snapshot
			Map updatedDiff = new HashMap();
			i = updatedSnapshot.keySet().iterator();
			while (i.hasNext()) {
				key = i.next();
				if (!updatedSnapshot.get(key).equals(fetchSnapshot.get(key))) {
					updatedDiff.put(key, updatedSnapshot.get(key));
				}
			}

			// determine if there's a conflict
			boolean proceed = true;
			Set updatedKeys = updatedDiff.keySet();
			i = currentDiff.keySet().iterator();
			while (i.hasNext()) {
				if (updatedKeys.contains(i.next())) {
					proceed = false;
					break;
				}
			}

			// if no conflicts, apply original diff to current object and exit
			if (proceed) {
				KeyValueCodingUtilities.takeStoredValuesFromDictionary(anObject, currentDiff);
				return true; // exit!
			}
		} catch (Exception exc) {
			// log error to standard out
			exc.printStackTrace();
		}

		// notify user we're unable to merge
		notifyMessageHandler(MessageChangeConflict + anObject);
		return false;
	}

	/**
	 * Sends the specified message to the message handler.
	 */
	private void notifyMessageHandler(String aMessage) {
		Object handler = null;
		try {
			handler = messageHandler();
			if (handler == null)
				return;
			NSSelector.invoke("editingContextPresentErrorMessage", new Class[] { EOEditingContext.class, String.class },
					handler, this, aMessage);
		} catch (NoSuchMethodException e) {
			// ignore: not implemented
		} catch (Exception exc) {
			// log to standard error
			System.err.println("Error while notifying message handler: " + handler + " : " + aMessage);
			exc.printStackTrace();
		}
	}

	/**
	 * Sends the specified message to the delegate. Returns the return value of the
	 * method, or null if no return value or no delegate or no implementation.
	 */
	private Object notifyDelegate(String aMethodName, Class[] types, Object[] params) {
		try {
			Object delegate = delegate();
			if (delegate == null)
				return null;
			return NSSelector.invoke(aMethodName, types, delegate, params);
		} catch (NoSuchMethodException e) {
			// ignore: not implemented
		} catch (Exception exc) {
			// log to standard error
			System.err.println("Error while messaging delegate: " + delegate + " : " + aMethodName);
			exc.printStackTrace();
		}

		return null;
	}

	// interface EOObserving

	/**
	 * Implementation of the EOObserving interface. Called before objects are
	 * modified.
	 */
	@Override
	public void objectWillChange(Object anObject) {
		if (ignoreChanges)
			return;
//NSNotificationCenter.defaultCenter().postNotification( "objectWillChange", this, new NSDictionary( "object", anObject ) );
//new RuntimeException().printStackTrace();

		willChange();

		// mark as updated if not marked already
		int i = updatedObjects.indexOfIdenticalObject(anObject);
		if (i == NSArray.NotFound) {
			// don't mark inserted objects as updated
			i = insertedObjects.indexOfIdenticalObject(anObject);
			if (i == NSArray.NotFound) {
				i = deletedObjects.indexOfIdenticalObject(anObject);
				if (i == NSArray.NotFound) {
					// add object
					updatedObjects.addObject(anObject);

					// record revert snapshot
					registrar.setCommitSnapshot(anObject, takeSnapshot(anObject));
				}
			}
		}

		// add to buffer
		if (updatedObjectsBuffer.indexOfIdenticalObject(anObject) == NSArray.NotFound) {
			updatedObjectsBuffer.addObject(anObject);
		}
	}

	// static methods

	public static double defaultFetchTimestampLag() {
		return defaultFetchTimestampLag;
	}

	/**
	 * Returns the default parent object store for all object stores created with
	 * the parameterless constructor.
	 */
	public static EOObjectStore defaultParentObjectStore() {
		return defaultParentObjectStore;
	}

	/*
	 * public static Object initObjectWithCoder ( Object anObject, NSCoder aCoder )
	 * { throw new net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 */

	/**
	 * Returns whether editing contexts are configured to retain strong references
	 * to their registered objects. If false, editing contexts will only retain weak
	 * references to their registered objects.
	 */
	public static boolean instancesRetainRegisteredObjects() {
		return retainsRegisteredObjects;
	}

	/**
	 * Sets the global default fetch timestamp lag.
	 */
	public static void setDefaultFetchTimestampLag(double aDouble) {
		defaultFetchTimestampLag = aDouble;
	}

	/**
	 * Sets the global default parent object store, used for the parameterless
	 * constructor.
	 */
	public static void setDefaultParentObjectStore(EOObjectStore anObjectStore) {
		defaultParentObjectStore = anObjectStore;
	}

	public static void setInstancesRetainRegisteredObjects(boolean retainsObjects) {
		retainsRegisteredObjects = retainsObjects;
	}

	/*
	 * public static void setSubstitutionEditingContext ( EOEditingContext aContext)
	 * { throw new net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 * 
	 * public static void setUsesContextRelativeEncoding ( boolean
	 * usesRelativeEncoding ) { throw new
	 * net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 * 
	 * public static EOEditingContext substitutionEditingContext () { throw new
	 * net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 * 
	 * public static boolean usesContextRelativeEncoding () { throw new
	 * net.wotonomy.util.WotonomyException("Not implemented yet."); }
	 */

	@Override
	public String toString() {
		return "[EOEditingContext@" + Integer.toHexString(System.identityHashCode(this)) + ":" + " inserted="
				+ idsForObjects(insertedObjects) + " updated=" + idsForObjects(updatedObjects) + " deleted="
				+ idsForObjects(deletedObjects) + " registered=" + registrar.registeredGlobalIDs() + " ]";
	}

	private List idsForObjects(List objects) {
		List result = new LinkedList();
		Iterator i = objects.iterator();
		while (i.hasNext())
			result.add(globalIDForObject(i.next()));
		return result;
	}

	// snapshots

	/**
	 * Returns a NSDictionary containing only the mutable properties for the
	 * specified object and deep clones of their values. Nulls are represented by
	 * NSNull.nullValue().
	 */
	private byte[] takeSnapshot(Object anObject) { // System.out.println( "takeSnapshot: " + anObject );
		return KeyValueCodingUtilities.freeze(anObject, this, anObject, true);
	}

	/**
	 * Applies the map of properties and values to the specified object. Null values
	 * for properties must be represented by the NSNull.nullValue(). Posts a
	 * willChange event before applying changes.
	 */
	private void applySnapshot(byte[] aSnapshot, Object anObject) {
		// must clone snapshot to avoid changing existing snapshot
		NSDictionary values = convertSnapshotToDictionary(aSnapshot);

//System.out.println( "applySnapshot: " + aSnapshot + " : " + values );
//ignoreChanges = true;        
		willChange();
		KeyValueCodingUtilities.takeStoredValuesFromDictionary(anObject, values);
//ignoreChanges = false;        
	}

	/**
	 * Snapshots are stored internally in binary format, but exposed to the user as
	 * NSDictionaries.
	 */
	private NSDictionary convertSnapshotToDictionary(byte[] aSnapshot) {
		// get the object
		Object clone = KeyValueCodingUtilities.thaw(aSnapshot, this, true);
		// get all keys for this object
		EOClassDescription classDesc = EOClassDescription.classDescriptionForClass(clone.getClass());
		List keys = new LinkedList();
		keys.addAll(classDesc.attributeKeys());
		keys.addAll(classDesc.toOneRelationshipKeys());
		keys.addAll(classDesc.toManyRelationshipKeys());

		return KeyValueCodingUtilities.valuesForKeys(clone, keys);
	}

	/**
	 * Creates a deep clone of the specified object. (Object.clone() only creates a
	 * shallow clone.) Returns null if operation fails.
	 */
	static private Object clone(EOEditingContext aSourceContext, Object aSource, EOEditingContext aDestinationContext) { // System.out.println(
																															// "clone:
																															// "
																															// +
																															// aSource
																															// );
		return KeyValueCodingUtilities.clone(aSourceContext, aSource, aDestinationContext);
	}

	/**
	 * Creates a deep clone of the specified object. but does not transpose
	 * references. This allows us to register an object before transposing
	 * references so that child objects will be able to resolve references to their
	 * parent. After recording the object, we copy the source object into the clone,
	 * which does transpose and resolve properly. Returns null if operation fails.
	 */
	static private Object registerClone(EOGlobalID aGlobalID, EOEditingContext aSourceContext, Object aSource,
			EOEditingContext aDestinationContext) {
		// while we'd like to just transpose/clone at the same time
		// we must record a clone without transposing: this
		// avoids a endless loop if the object graph has a cycle
		Object clone = KeyValueCodingUtilities.thaw(
				KeyValueCodingUtilities.freeze(aSource, aSourceContext, aSource, false), aDestinationContext, false);

		aDestinationContext.recordObject(clone, aGlobalID);

		// need to copy to transpose references into this context
		// while preserving the same instance of the object
		aDestinationContext.ignoreChanges = true;
		copy(aSourceContext, aSource, aDestinationContext, clone);
		aDestinationContext.ignoreChanges = false;

		// return our clone
		return clone;
	}

	/**
	 * Copies values from one object to another. Returns the destination object, or
	 * throws exception if operation fails.
	 */
	static private Object copy(EOEditingContext aSourceContext, Object aSource, EOEditingContext aDestinationContext,
			Object aDestination) { // System.out.println( "copy: " );
		EOObserverCenter.notifyObserversObjectWillChange(aDestination);
		KeyValueCodingUtilities.copy(aSourceContext, aSource, aDestinationContext, aDestination);
		return aDestination;
	}

	// process recent changes

	/**
	 * Called to notify observers of changes. Also calls runLater().
	 */
	private void willChange() {
		EOObserverCenter.notifyObserversObjectWillChange(this);
		runLater();
	}

	/**
	 * Called to ensure that processRecentChanges will be called on the next event
	 * loop.
	 */
	private void runLater() {
		if (!willRunLater) {
			willRunLater = true;
			NSRunLoop.currentRunLoop().performSelectorWithOrder(runLaterSelector, this, null,
					EditingContextFlushChangesRunLoopOrdering, null);
		}
	}

	/**
	 * This method is called by the event queue run loop and calls
	 * processRecentChanges. NOTE: This method is not part of the specification.
	 */
	public void flushRecentChanges(Object anObject) {
//System.out.println( "EODelayedObserverQueue: running" );		
		processRecentChanges();
		willRunLater = false;
	}

	// inner classes

	/**
	 * Gatekeeper for all access to registered objects.
	 */
	static private class Registrar {
		EOEditingContext context;
		NSMutableDictionary IDsToObjects;
		NSMutableDictionary objectsToIDs;
		NSMutableDictionary objectsToCommitSnapshots;
		NSMutableDictionary objectsToCurrentSnapshots;

		ReferenceKey comparisonKey; // FIXME not thread safe!

		public Registrar(EOEditingContext aContext) {
			context = aContext;
			IDsToObjects = new NSMutableDictionary();
			objectsToIDs = new NSMutableDictionary();
			objectsToCommitSnapshots = new NSMutableDictionary();
			objectsToCurrentSnapshots = new NSMutableDictionary();
			comparisonKey = new ReferenceKey();
		}

		public NSArray registeredObjects() {
			return IDsToObjects.allValues();
		}

		public NSArray registeredGlobalIDs() {
			return IDsToObjects.allKeys();
		}

		public Object objectForGlobalID(EOGlobalID aGlobalID) {
			return IDsToObjects.objectForKey(aGlobalID);
		}

		public EOGlobalID globalIDForObject(Object anObject) {
			comparisonKey.set(anObject);
			return (EOGlobalID) objectsToIDs.objectForKey(comparisonKey);
		}

		public byte[] getCommitSnapshot(Object anObject) {
			comparisonKey.set(anObject);
			return (byte[]) objectsToCommitSnapshots.objectForKey(comparisonKey);
		}

		public void setCommitSnapshot(Object anObject, byte[] aSnapshot) {
			if (aSnapshot == null) {
				comparisonKey.set(anObject);
				objectsToCommitSnapshots.removeObjectForKey(comparisonKey);
			} else {
				objectsToCommitSnapshots.setObjectForKey(aSnapshot, new ReferenceKey(anObject));
			}
		}

		public byte[] getCurrentSnapshot(Object anObject) {
			comparisonKey.set(anObject);
			return (byte[]) objectsToCurrentSnapshots.objectForKey(comparisonKey);
		}

		public void setCurrentSnapshot(Object anObject, byte[] aSnapshot) {
			if (aSnapshot == null) {
				comparisonKey.set(anObject);
				objectsToCurrentSnapshots.removeObjectForKey(comparisonKey);
			} else {
				objectsToCurrentSnapshots.setObjectForKey(aSnapshot, new ReferenceKey(anObject));
			}
		}

		public void registerObject(Object anObject, EOGlobalID aGlobalID) {
			IDsToObjects.setObjectForKey(anObject, aGlobalID);
			objectsToIDs.setObjectForKey(aGlobalID, new ReferenceKey(anObject));
			EOObserverCenter.addObserver(context, anObject);
		}

		public void forgetObject(Object anObject) {
			comparisonKey.set(anObject);
			Object id = objectsToIDs.objectForKey(comparisonKey);
			IDsToObjects.removeObjectForKey(id);
			objectsToIDs.removeObjectForKey(comparisonKey);
			EOObserverCenter.removeObserver(context, anObject);
		}

		public void disposeSnapshots(Object anObject) {
			setCommitSnapshot(anObject, null);
			setCurrentSnapshot(anObject, null);
		}

	}

	/**
	 * Registrar that uses only WeakReferences. Used if retainsRegisteredObjects is
	 * false.
	 */
	static private class WeakRegistrar extends Registrar {
		private WeakReferenceKey weakComparisonKey; // FIXME not thread safe!

		public WeakRegistrar(EOEditingContext aContext) {
			super(aContext);
			weakComparisonKey = new WeakReferenceKey();
		}

		@Override
		public NSArray registeredObjects() {
			Object object;
			WeakReferenceKey weakKey;
			NSMutableArray result = new NSMutableArray();
			Enumeration e = new NSArray(objectsToIDs.allKeys()).objectEnumerator();
			while (e.hasMoreElements()) {
				weakKey = (WeakReferenceKey) e.nextElement();
				object = weakKey.get();
				if (object != null) {
					result.addObject(object);
				} else {
					// object has been released: perform cleanup
					disposeObject(null, weakKey);
				}
			}
			return result;
		}

		@Override
		public Object objectForGlobalID(EOGlobalID aGlobalID) {
			WeakReference ref = (WeakReference) super.objectForGlobalID(aGlobalID);
			if (ref == null)
				return null;
			Object result = ref.get();
			if (result == null) {
				// clean up manually
				IDsToObjects.removeObjectForKey(aGlobalID);
				Iterator i = new LinkedList(objectsToIDs.allKeysForObject(ref)).iterator();
				while (i.hasNext()) {
					objectsToIDs.removeObjectForKey(i.next());
				}
				disposeSnapshots(aGlobalID);
			}
			return result;
		}

		@Override
		public byte[] getCommitSnapshot(Object anObject) {
			weakComparisonKey.set(anObject);
			return (byte[]) objectsToCommitSnapshots.objectForKey(weakComparisonKey);
		}

		@Override
		public void setCommitSnapshot(Object anObject, byte[] aSnapshot) {
			if (aSnapshot == null) {
				weakComparisonKey.set(anObject);
				objectsToCommitSnapshots.removeObjectForKey(weakComparisonKey);
			} else {
				objectsToCommitSnapshots.setObjectForKey(aSnapshot, new WeakReferenceKey(anObject));
			}
		}

		@Override
		public byte[] getCurrentSnapshot(Object anObject) {
			weakComparisonKey.set(anObject);
			return (byte[]) objectsToCurrentSnapshots.objectForKey(weakComparisonKey);
		}

		@Override
		public void setCurrentSnapshot(Object anObject, byte[] aSnapshot) {
			if (aSnapshot == null) {
				weakComparisonKey.set(anObject);
				objectsToCurrentSnapshots.removeObjectForKey(weakComparisonKey);
			} else {
				objectsToCurrentSnapshots.setObjectForKey(aSnapshot, new WeakReferenceKey(anObject));
			}
		}

		@Override
		public void registerObject(Object anObject, EOGlobalID aGlobalID) { // new
																			// net.wotonomy.ui.swing.ReferenceInspector(
																			// anObject );
			IDsToObjects.setObjectForKey(new WeakReference(anObject), aGlobalID);
			objectsToIDs.setObjectForKey(aGlobalID, new WeakReferenceKey(anObject));
			EOObserverCenter.addObserver(context, anObject);
		}

		@Override
		public void forgetObject(Object anObject) {
			disposeObject(anObject, null);
		}

		// must specify one or the other
		private void disposeObject(Object anObject, WeakReferenceKey key) {
			if (key == null)
				key = new WeakReferenceKey(anObject);
			EOGlobalID id = (EOGlobalID) objectsToIDs.objectForKey(key);
			if (id != null)
				IDsToObjects.removeObjectForKey(id);
			objectsToIDs.removeObjectForKey(key);
			disposeSnapshots(id);
			if (anObject != null) {
				EOObserverCenter.removeObserver(context, anObject);
			}
		}
	}

	/**
	 * Private class used to force a hashmap to perform key comparisons by
	 * reference.
	 */
	static private class ReferenceKey {
		int hashCode;
		Object referent;

		public ReferenceKey() {
			referent = null;
			hashCode = -1;
		}

		public ReferenceKey(Object anObject) {
			set(anObject);
		}

		public Object get() {
			return referent;
		}

		public void set(Object anObject) {
			referent = anObject;
			hashCode = anObject.hashCode();
		}

		/**
		 * Returns the actual key's hash code.
		 */
		@Override
		public int hashCode() {
			return hashCode;
		}

		/**
		 * Compares by reference.
		 */
		@Override
		public boolean equals(Object anObject) {
			if (anObject == this)
				return true;
			if (anObject instanceof ReferenceKey) {
				return ((ReferenceKey) anObject).get() == referent;
			}
			return false;
		}
	}

	/**
	 * Private class used to force a hashmap to perform key comparisons by
	 * reference.
	 */
	static private class WeakReferenceKey extends ReferenceKey {
		public WeakReferenceKey() {
			super();
		}

		public WeakReferenceKey(Object anObject) {
			super(anObject);
		}

		@Override
		public Object get() {
			return ((WeakReference) referent).get();
		}

		@Override
		public void set(Object anObject) {
			referent = new WeakReference(anObject);
			hashCode = anObject.hashCode();
		}

		/**
		 * Compares by reference.
		 */
		@Override
		public boolean equals(Object anObject) {
			if (anObject == this)
				return true;
			if (anObject instanceof ReferenceKey) {
				return ((ReferenceKey) anObject).get() == get();
			}
			return false;
		}
	}

	/**
	 * Key combining an object with a string. Object is compared by reference.
	 */
	static private class CompoundKey {
		private Object object;
		private String string;
		private int hashCode;

		/**
		 * Creates compound key. Neither name nor object may be null.
		 */
		public CompoundKey(Object anObject, String aString) {
			object = anObject;
			string = aString;
			hashCode = object.hashCode() + string.hashCode();
		}

		@Override
		public int hashCode() {
			return hashCode;
		}

		@Override
		public boolean equals(Object anObject) {
			if (anObject instanceof CompoundKey) {
				CompoundKey key = (CompoundKey) anObject;
				return ((key.object == object) && (key.string.equals(string)));
			}
			return false;
		}

		@Override
		public String toString() {
			return "[CompoundKey:" + object + ":" + string + "]";
		}
	}

	/**
	 * Used by EditingContext to delegate behavior to another class. Note that
	 * EditingContext doesn't require its delegates to implement this interface:
	 * rather, this interface defines the methods that EditingContext will attempt
	 * to invoke dynamically on its delegate. The delegate may choose to implement
	 * only a subset of the methods on the interface.
	 */
	public interface Delegate {
		/**
		 * Called after the editing context has completed merge operations on one or
		 * more objects after receiving an ObjectChangedInStore notification.
		 */
		void editingContextDidMergeChanges(EOEditingContext anEditingContext);

		/**
		 * Called by objectsWithFetchSpecification. If null, the editing context will
		 * pass the fetch specification on to its parent store, as normal. Otherwise,
		 * the context will use the returned array to service the request.
		 */
		NSArray editingContextShouldFetchObjects(EOEditingContext anEditingContext,
				EOFetchSpecification fetchSpecification);

		/**
		 * Called to determine whether an object should be invalidated. Return false to
		 * prevent the object from being invalidated. Default is true.
		 */
		boolean editingContextShouldInvalidateObject(EOEditingContext anEditingContext, Object anObject,
				EOGlobalID aGlobalID);

		/**
		 * Called to determine whether the editing context should attempt to merge
		 * changes in the specified object that the parent store says has changed via an
		 * ObjectChangedInStore notification. Default is true. Return false if you wish
		 * to handle the merge yourself, by extracting the values in the object now and
		 * comparing them to the values when editingContextDidMergeChanges is called.
		 */
		boolean editingContextShouldMergeChangesForObject(EOEditingContext anEditingContext, Object anObject);

		/**
		 * Returns whether the editing context should ask its message handler to display
		 * a message. Return false if the delegate will display the error. Default is
		 * true.
		 */
		boolean editingContextShouldPresentException(EOEditingContext anEditingContext, Throwable exception);

		/**
		 * Returns whether the editing context should undo the most recent set of
		 * changes that resulted in a validation failure. Default is true.
		 */
		boolean editingContextShouldUndoUserActionsAfterFailure(EOEditingContext anEditingContext);

		/**
		 * Returns whether the editing context should validate the most recent set of
		 * changes. Default is true.
		 */
		boolean editingContextShouldValidateChanges(EOEditingContext anEditingContext);

		/**
		 * Called before the editing context saves its changes to the parent object
		 * store.
		 */
		void editingContextWillSaveChanges(EOEditingContext anEditingContext);

	}

	/**
	 * Editors register themselves with the editing context so that they may receive
	 * notification before the context commits changes. This is useful for
	 * associations whose components do not immediately commit their changes to the
	 * object they are editing.
	 */
	public interface Editor {
		/**
		 * Called before the editing context saves its changes to the parent object
		 * store.
		 */
		void editingContextWillSaveChanges(EOEditingContext anEditingContext);

		/**
		 * Called to determine whether this editor has changes that have not been
		 * committed to the object in the context.
		 */
		boolean editorHasChangesForEditingContext(EOEditingContext anEditingContext);

	}

	/**
	 * Used by EditingContext to delegate messaging handling to another class,
	 * typically the display group that has the currently active association. Note
	 * that EditingContext doesn't require its message handlers to implement this
	 * interface: rather, this interface defines the methods that EditingContext
	 * will attempt to invoke dynamically on its delegate. The delegate may choose
	 * to implement only a subset of the methods on the interface.
	 */
	public interface MessageHandler {
		/**
		 * Called to display a message for an error that occurred in the specified
		 * editing context.
		 */
		void editingContextPresentErrorMessage(EOEditingContext anEditingContext, String aMessage);

		/**
		 * Called by the specified object store to determine whether fetching should
		 * continue, where count is the current count and limit is the limit as
		 * specified by the fetch specification. Default is false.
		 */
		boolean editingContextShouldContinueFetching(EOEditingContext anEditingContext, int count, int limit,
				EOObjectStore anObjectStore);

	}

}

/*
 * $Log$ Revision 1.2 2006/02/16 16:47:14 cgruber Move some classes in to
 * "internal" packages and re-work imports, etc.
 *
 * Also use UnsupportedOperationExceptions where appropriate, instead of
 * WotonomyExceptions.
 *
 * Revision 1.1 2006/02/16 13:19:57 cgruber Check in all sources in
 * eclipse-friendly maven-enabled packages.
 *
 * Revision 1.86 2003/12/18 15:37:38 mpowers Changes to retain ability to work
 * with objects that don't necessarily implement EOEnterpriseObject. I would
 * still like to preserve this case for general usage, however the access
 * package is free to assume that those objects will be EOs and cast
 * appropriately.
 *
 * Revision 1.85 2003/08/19 01:53:12 chochos EOObjectStore had some incompatible
 * return types (Object instead of EOEnterpriseObject, in fault methods mostly).
 * It's internally consistent but I hope it doesn't break anything based on
 * this, even though fault methods mostly throw exceptions for now.
 *
 * Revision 1.84 2003/08/06 23:07:52 chochos general code cleanup (mostly,
 * removing unused imports)
 *
 * Revision 1.83 2003/02/13 15:24:33 mpowers hasChanges is now derived, not
 * tracked. refaultObject now more consistently removes object from updated
 * list.
 *
 * Revision 1.82 2002/12/16 15:46:00 mpowers Major refactoring to implement
 * setInstancesRetainRegisteredObjects().
 *
 * Revision 1.81 2002/11/18 22:10:58 mpowers Now resetting hasChanges flag on
 * reset.
 *
 * Revision 1.80 2002/10/24 21:15:33 mpowers New implementations of NSArray and
 * subclasses.
 *
 * Revision 1.79 2002/10/24 18:18:12 mpowers NSArray's are now considered
 * read-only, so we can return our internal representation to reduce unnecessary
 * object allocation.
 *
 * Revision 1.78 2002/06/21 21:44:33 mpowers No longer marking deleted objects
 * as updated (thanks to dwang).
 *
 * Revision 1.77 2002/05/20 15:10:17 mpowers No longer refaulting if delegate
 * does not wish to handle the merge.
 *
 * Revision 1.76 2002/03/26 21:46:06 mpowers Contributing EditingContext as a
 * java-friendly convenience.
 *
 * Revision 1.75 2002/03/06 16:14:57 mpowers More attempts at ignoring update
 * conflicts that come from ourself.
 *
 * Revision 1.74 2002/02/21 21:57:50 mpowers Implemented default merge behavior.
 *
 * Revision 1.73 2002/02/20 16:46:54 mpowers Implemented better support for
 * EOEditingContext.Delegate.
 *
 * Revision 1.70 2002/02/19 22:26:05 mpowers Implemented
 * EOEditingContext.MessageHandler support.
 *
 * Revision 1.69 2002/02/19 16:33:42 mpowers Implemented support for
 * EditingContext.Editor
 *
 * Revision 1.68 2002/02/13 22:00:34 mpowers Fixed: invalidateAllObjects tries
 * to invalidate inserted objects, typically causing class cast exceptions
 * involving EOTemporaryGlobalID.
 *
 * Revision 1.67 2002/02/06 21:15:35 mpowers No longer refaulting a dirty object
 * when we receive an invalidation notif.
 *
 * Revision 1.66 2002/01/08 19:31:03 mpowers refaultObject now correctly
 * refaults the object.
 *
 * Revision 1.65 2001/12/20 18:56:15 mpowers Refinements to snapshotting and
 * calling processRecentChanges.
 *
 * Revision 1.64 2001/12/10 15:11:41 mpowers Now only tracking a commit snapshot
 * after an object has been modified.
 *
 * Revision 1.63 2001/11/14 00:08:10 mpowers Now marking context changed when
 * objects are inserted or deleted and when child contexts save their changes
 * into this context.
 *
 * Revision 1.62 2001/11/07 14:49:31 mpowers invalidateAllObjects now handles
 * objects manually discarded in the course of invalidation.
 *
 * Revision 1.61 2001/10/26 20:02:49 mpowers No longer using
 * NSNotificationQueue: all notifications are posted immed.
 *
 * Revision 1.60 2001/10/26 18:37:50 mpowers Now using NSRunLoop to correctly
 * flush recent changes before delayed observers and AWT events.
 *
 * Revision 1.59 2001/10/23 22:29:59 mpowers Now posting notifications
 * immediately. Recent changes are flushed at ObserverPrioritySixth, soon to
 * change.
 *
 * Revision 1.58 2001/09/10 14:16:51 mpowers EditingContexts now relay
 * InvalidatedAllObjectsInStore notifications.
 *
 * Revision 1.57 2001/06/18 14:11:15 mpowers Inserting a deleted object simply
 * cancels the delete operation.
 *
 * Revision 1.56 2001/06/07 22:07:59 mpowers Now handling delete notifications
 * before update notifications. Eliminated the case where deleted objects were
 * also being put on the updated list when notifying child contexts.
 *
 * Revision 1.55 2001/05/18 21:04:33 mpowers Reimplemented
 * EditingContext.initializeObject.
 *
 * Revision 1.54 2001/05/05 23:05:42 mpowers Implemented Array Faults.
 *
 * Revision 1.53 2001/05/05 15:00:06 mpowers Tested load-on-demand: still works.
 * Now using registerClone for consistency. Editing context is temporarily
 * posting notification on objectWillChange.
 *
 * Revision 1.52 2001/05/05 14:11:48 mpowers Implemented registerClone.
 *
 * Revision 1.51 2001/05/04 16:57:56 mpowers Now correctly transposing
 * references to editing contexts when cloning/copying between editing contexts.
 *
 * Revision 1.50 2001/05/02 17:58:41 mpowers Removed debugging code, added
 * comments.
 *
 * Revision 1.49 2001/05/02 15:47:40 mpowers Fixed the pernicious problem with
 * reverts: recordObject was recording a snapshot of the clone before the
 * transposition-copy happened, so the revert object would lose all of its
 * transposed relationships.
 *
 * Revision 1.48 2001/05/02 12:39:05 mpowers Fixed a nasty problem with
 * transpose-cloning and faultForGlobalID. Now we're forced to create a deep
 * clone, registered it, and then transpose it after it has been registered.
 *
 * Revision 1.47 2001/04/30 13:15:24 mpowers Child contexts re-initializing
 * objects invalidated in parent now propery transpose relationships.
 *
 * Revision 1.46 2001/04/29 22:02:45 mpowers Work on id transposing between
 * editing contexts.
 *
 * Revision 1.45 2001/04/29 02:29:31 mpowers Debugging relationship faulting.
 *
 * Revision 1.44 2001/04/28 16:18:44 mpowers Implementing relationships.
 *
 * Revision 1.43 2001/04/28 14:12:23 mpowers Refactored cloning/copying into
 * KeyValueCodingUtilities.
 *
 * Revision 1.42 2001/04/27 00:27:11 mpowers Provided description to
 * not-implemented exceptions.
 *
 * Revision 1.41 2001/04/26 01:16:44 mpowers Major bug fix so we no longer
 * accumulate objects in the all objects list with every
 * InvalidateAllObjectsInStore.
 *
 * Revision 1.40 2001/04/21 23:07:49 mpowers Now only broadcasts notifications
 * if there's actually a change.
 *
 * Revision 1.39 2001/04/13 16:33:11 mpowers Corrected the refaulting behavior.
 *
 * Revision 1.38 2001/04/09 21:42:10 mpowers Debugging and optimizing
 * notifications.
 *
 * Revision 1.37 2001/04/08 20:59:47 mpowers objectsForFetchSpecification now
 * relies on faultForGlobalID.
 *
 * Revision 1.36 2001/04/03 20:36:01 mpowers Fixed
 * refaulting/reverting/invalidating to be self-consistent.
 *
 * Revision 1.35 2001/03/29 03:29:49 mpowers Now using KeyValueCoding and
 * Support instead of Introspector.
 *
 * Revision 1.34 2001/03/28 14:06:29 mpowers Implemented snapshots. Revert now
 * uses snapshots.
 *
 * Revision 1.33 2001/03/20 23:20:33 mpowers invalidating all objects now sets
 * the dirty flag to false.
 *
 * Revision 1.32 2001/03/19 21:44:36 mpowers Reverts reinitialize for now.
 * Testing for inserted objects instead of temp id when invalidating object.
 *
 * Revision 1.31 2001/03/15 21:10:26 mpowers Implemented global id
 * re-registration for newly saved inserts.
 *
 * Revision 1.30 2001/03/13 21:41:34 mpowers Broadcasting willChange for any
 * change to hasChanges. Fixed major bug with inserted objects treated as
 * updated objects in child display groups.
 *
 * Revision 1.29 2001/03/09 22:10:30 mpowers Fine tuned initializeObject.
 *
 * Revision 1.28 2001/03/06 23:23:55 mpowers objectForGlobalID now returns null
 * if not found. objectsForFetchSpecification again does things the old way, for
 * now.
 *
 * Revision 1.27 2001/03/02 16:31:45 mpowers Trying to better handle fetches
 * from child contexts. No longer trying to invalidate temporary objects.
 *
 * Revision 1.26 2001/02/28 16:25:19 mpowers Now calling globalIDForObject
 * internally.
 *
 * Revision 1.25 2001/02/27 17:36:55 mpowers Objects inserted from child now
 * preserve the existing temporary id.
 *
 * Revision 1.24 2001/02/27 02:11:17 mpowers Now throwing exception when cloning
 * fails. Removed debugging printlns.
 *
 * Revision 1.23 2001/02/26 22:41:51 mpowers Implemented null placeholder
 * classes. Duplicator now uses NSNull. No longer catching base exception class.
 *
 * Revision 1.22 2001/02/26 21:18:45 mpowers Now marking edited objects from
 * child contexts that were not already recorded in parent as changed in
 * saveChangesInEditingContext.
 *
 * Revision 1.21 2001/02/26 15:53:22 mpowers Fine-tuning notification firing.
 * Child display groups now update properly after parent save or invalidate.
 *
 * Revision 1.20 2001/02/24 17:03:22 mpowers Implemented the notification queue,
 * and changed editing context to use it.
 *
 * Revision 1.19 2001/02/23 23:44:15 mpowers Fine-tuning notification handling.
 *
 * Revision 1.18 2001/02/22 22:56:57 mpowers Only refaulting edited objects on
 * parent store invalidateAll.
 *
 * Revision 1.17 2001/02/22 20:54:39 mpowers Implemented notification handling.
 *
 * Revision 1.16 2001/02/21 22:10:55 mpowers Editing context is now posting
 * appropriate notifications.
 *
 * Revision 1.15 2001/02/21 21:17:32 mpowers Now retaining a reference to the
 * recent changes observer. Better documented need to retain reference. Started
 * implementing notifications.
 *
 * Revision 1.14 2001/02/20 17:24:22 mpowers Now using reference keys in
 * objectToID.
 *
 * Revision 1.13 2001/02/20 16:45:36 mpowers Child data sources now accept a
 * data source instead of an editing context for more flexibility. Child data
 * sources now forward relationship methods to parent source.
 *
 * Revision 1.12 2001/02/16 22:51:29 mpowers Now deep-cloning objects passed
 * between editing contexts.
 *
 * Revision 1.11 2001/02/16 18:34:19 mpowers Implementing nested contexts.
 *
 * Revision 1.9 2001/02/15 21:13:30 mpowers First draft implementation is
 * complete. Now on to debugging.
 *
 * Revision 1.7 2001/02/13 23:24:29 mpowers Implementing more of editing
 * context.
 *
 * Revision 1.4 2001/02/09 22:09:34 mpowers Completed implementation of
 * EOObjectStore.
 *
 * Revision 1.3 2001/02/06 15:24:11 mpowers Widened parameters on abstract
 * method to fix build.
 *
 * Revision 1.2 2001/02/05 03:45:37 mpowers Starting work on EOEditingContext.
 *
 * Revision 1.1.1.1 2000/12/21 15:46:42 mpowers Contributing wotonomy.
 *
 */