001/**
002 * Copyright 2015 DuraSpace, Inc.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.fcrepo.kernel.impl.observer.eventmappings;
017
018import static com.google.common.collect.Multimaps.index;
019import static org.slf4j.LoggerFactory.getLogger;
020import static java.util.Arrays.asList;
021import static javax.jcr.observation.Event.PROPERTY_ADDED;
022import static javax.jcr.observation.Event.PROPERTY_CHANGED;
023import static javax.jcr.observation.Event.PROPERTY_REMOVED;
024
025import java.util.Iterator;
026import java.util.List;
027
028import javax.jcr.RepositoryException;
029import javax.jcr.observation.Event;
030
031import org.fcrepo.kernel.exception.RepositoryRuntimeException;
032import org.fcrepo.kernel.observer.FedoraEvent;
033import org.fcrepo.kernel.observer.eventmappings.InternalExternalEventMapper;
034
035import org.slf4j.Logger;
036
037import com.google.common.base.Function;
038import com.google.common.collect.Multimap;
039
040/**
041 * Maps all JCR {@link Event}s concerning one JCR node to one
042 * {@link FedoraEvent}. Adds the types of those JCR events together to calculate
043 * the final type of the emitted FedoraEvent. TODO stop aggregating events in
044 * the heap and make this a purely iterative algorithm, if possible
045 *
046 * @author ajs6f
047 * @since Feb 27, 2014
048 */
049public class AllNodeEventsOneEvent implements InternalExternalEventMapper {
050
051    private static final List<Integer> PROPERTY_EVENT_TYPES = asList(PROPERTY_ADDED, PROPERTY_CHANGED,
052            PROPERTY_REMOVED);
053
054    /**
055     * Extracts the node identifier from a JCR {@link Event}.
056     */
057    private static final Function<Event, String> EXTRACT_NODE_ID = new Function<Event, String>() {
058
059        @Override
060        public String apply(final Event ev) {
061            try {
062                final String id = ev.getIdentifier();
063                log.debug("Sorting an event by identifier: {}", id);
064                return id;
065            } catch (final RepositoryException e) {
066                throw new RepositoryRuntimeException(e);
067            }
068        }
069    };
070
071    @Override
072    public Iterator<FedoraEvent> apply(final Iterator<Event> events) {
073
074        return new Iterator<FedoraEvent>() {
075
076            // sort JCR events into a Multimap keyed by the node ID involved
077            final Multimap<String, Event> sortedEvents = index(events, EXTRACT_NODE_ID);
078
079            final Iterator<String> nodeIds = sortedEvents.keySet().iterator();
080
081            @Override
082            public boolean hasNext() {
083                return nodeIds.hasNext();
084            }
085
086            @Override
087            public FedoraEvent next() {
088                final Iterator<Event> nodeSpecificEvents = sortedEvents.get(nodeIds.next()).iterator();
089                // we can safely call next() immediately on nodeSpecificEvents
090                // because if
091                // there was no event at all, there would appear no entry in our
092                // Multimap under this key
093                final Event firstEvent = nodeSpecificEvents.next();
094                final FedoraEvent fedoraEvent = new FedoraEvent(firstEvent);
095
096                addProperty(fedoraEvent, firstEvent);
097                while (nodeSpecificEvents.hasNext()) {
098                    // add the event type and property name to the event we are building up to emit
099                    // we could aggregate other information here if that seems useful
100                    final Event otherEvent = nodeSpecificEvents.next();
101                    fedoraEvent.addType(otherEvent.getType());
102                    addProperty(fedoraEvent, otherEvent);
103                }
104                return fedoraEvent;
105            }
106
107            @Override
108            public void remove() {
109                // the underlying Multimap is immutable anyway
110                throw new UnsupportedOperationException();
111            }
112
113            private void addProperty( final FedoraEvent fedoraEvent, final Event ev ) {
114                try {
115                    if (PROPERTY_EVENT_TYPES.contains(ev.getType())) {
116                        final String eventPath = ev.getPath();
117                        fedoraEvent.addProperty(eventPath.substring(eventPath.lastIndexOf("/") + 1));
118                    } else {
119                        log.trace("Not adding non-event property: {}, {}", fedoraEvent, ev);
120                    }
121                } catch (final RepositoryException e) {
122                    throw new RepositoryRuntimeException(e);
123                }
124            }
125        };
126    }
127
128    private final static Logger log = getLogger(AllNodeEventsOneEvent.class);
129}