AbstractDatastreamEnhancementService.java

/**
 * Copyright 2008 The University of North Carolina at Chapel Hill
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package edu.unc.lib.dl.cdr.services;

import static edu.unc.lib.dl.util.JMSMessageUtil.ServicesActions.APPLY_SERVICE;
import static edu.unc.lib.dl.util.JMSMessageUtil.ServicesActions.APPLY_SERVICE_STACK;

import java.util.regex.Pattern;

import edu.unc.lib.dl.cdr.services.exception.EnhancementException;
import edu.unc.lib.dl.cdr.services.model.EnhancementMessage;
import edu.unc.lib.dl.cdr.services.model.FedoraEventMessage;
import edu.unc.lib.dl.fedora.FedoraException;
import edu.unc.lib.dl.fedora.PID;
import edu.unc.lib.dl.util.ContentModelHelper;
import edu.unc.lib.dl.util.ContentModelHelper.Datastream;
import edu.unc.lib.dl.util.JMSMessageUtil;
import edu.unc.lib.dl.util.JMSMessageUtil.FedoraActions;

public abstract class AbstractDatastreamEnhancementService extends AbstractIrodsObjectEnhancementService {

	protected String derivativeDatastream;
	protected Pattern mimetypePattern;
	
	private final static String OCTET_STREAM_MIMETYPE = "application/octet-stream"; 
	
	@Override
	public boolean prefilterMessage(EnhancementMessage message) throws EnhancementException {
		String action = message.getQualifiedAction();

		if (JMSMessageUtil.ServicesActions.APPLY_SERVICE_STACK.equals(action))
			return true;
		if (JMSMessageUtil.ServicesActions.APPLY_SERVICE.equals(action))
			return this.getClass().getName().equals(message.getServiceName());

		// If its not a Fedora message at this point, then its not going to match anything else
		if (!(message instanceof FedoraEventMessage))
			return false;

		if (JMSMessageUtil.FedoraActions.INGEST.equals(action))
			return true;
		if (!JMSMessageUtil.FedoraActions.MODIFY_DATASTREAM_BY_REFERENCE.equals(action)
				&& !JMSMessageUtil.FedoraActions.ADD_DATASTREAM.equals(action)
				&& !JMSMessageUtil.FedoraActions.MODIFY_DATASTREAM_BY_VALUE.equals(action))
			return false;
		String datastream = ((FedoraEventMessage) message).getDatastream();

		return ContentModelHelper.Datastream.DATA_FILE.equals(datastream);
	}
	
	/**
	 * Applicability check which verifies that the data file is of an appropriate type and is either not present or newer
	 * than the derivative to be generated
	 * 
	 * @param pid
	 * @return
	 * @throws FedoraException
	 */
	protected boolean isDatastreamApplicable(PID pid) throws FedoraException {
		edu.unc.lib.dl.fedora.types.Datastream dataDoc
				= managementClient.getDatastream(pid, Datastream.DATA_FILE.getName());
		
		// Don't process if there is no original data
		if (dataDoc == null) {
			return false;
		}

		// Filter out objects with non-applicable mimetypes
		if (!isMimetypeApplicable(pid, dataDoc)) {
			return false;
		}
		
		edu.unc.lib.dl.fedora.types.Datastream derivDoc
				= managementClient.getDatastream(pid, derivativeDatastream);
		
		// No derivative present
		if (derivDoc == null) {
			return true;
		}
		
		// Derivative is older than the original data, need to reperform the enhancement
		// Dates are in iso8601/UTC format, so lexographic string comparison is sufficient
		return dataDoc.getCreateDate().compareTo(derivDoc.getCreateDate()) > 0;
	}

	/**
	 * Applicability check which only verifies that the data file exists and is of a mimetype appropriate for this
	 * service.
	 * 
	 * @param pid
	 * @return
	 * @throws FedoraException
	 */
	protected boolean isApplicableType(PID pid) throws FedoraException {
		edu.unc.lib.dl.fedora.types.Datastream dataDoc
				= managementClient.getDatastream(pid, Datastream.DATA_FILE.getName());

		// Don't process if there is no original data
		if (dataDoc == null) {
			return false;
		}
		
		// Filter out objects with non-applicable mimetypes
		return isMimetypeApplicable(pid, dataDoc);
	}
	
	protected boolean isMimetypeApplicable(PID pid, edu.unc.lib.dl.fedora.types.Datastream dataDoc) {
		// Filter out objects with non-applicable mimetypes
		if (mimetypePattern != null) {
			String mimetype = dataDoc.getMIMEType();
			// If the mimetype from fedora isn't informative, retrieve source mimetype instead
			if (OCTET_STREAM_MIMETYPE.equals(mimetype)) {
				mimetype = tripleStoreQueryService.fetchFirstBySubjectAndPredicate(pid, 
						ContentModelHelper.CDRProperty.hasSourceMimeType.toString());
			}
			
			if (!mimetypePattern.matcher(mimetype).matches()){
				return false;
			}
		}
		
		return true;
	}
	
	@Override
	public boolean isApplicable(EnhancementMessage message) throws EnhancementException {
		String action = message.getQualifiedAction();
		
		// Only need to check further if this is an ingest message or the DATA_FILE was changed
		if (!(FedoraActions.INGEST.equals(action)
				|| FedoraActions.MODIFY_DATASTREAM_BY_REFERENCE.equals(action)
				|| FedoraActions.ADD_DATASTREAM.equals(action)
				|| FedoraActions.MODIFY_DATASTREAM_BY_VALUE.equals(action)
				|| APPLY_SERVICE_STACK.equals(action)
				|| (APPLY_SERVICE.equals(action) && getClass().getName()
						.equals(message.getServiceName())))) {
			return false;
		}
		
		try {
			// For a forced message, only check if the datastream is of an applicable type
			if (message.isForce()) {
				return isApplicableType(message.getPid());
			}
			
			// For other messages, determine whether the derivative exists or is stale
			return isDatastreamApplicable(message.getPid());
		} catch (FedoraException e) {
			throw new EnhancementException("Failed to check if enhancement was applicable for " + message.getPid(), e);
		}
	}

}