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.rdf.impl;
017
018import static com.google.common.collect.Lists.newArrayList;
019import static com.hp.hpl.jena.rdf.model.ResourceFactory.createResource;
020
021import com.google.common.base.Converter;
022import com.google.common.collect.Lists;
023
024import org.fcrepo.kernel.models.FedoraResource;
025import org.fcrepo.kernel.exception.RepositoryRuntimeException;
026import org.fcrepo.kernel.identifiers.IdentifierConverter;
027
028import com.hp.hpl.jena.rdf.model.Resource;
029
030import org.fcrepo.kernel.impl.identifiers.HashConverter;
031import org.fcrepo.kernel.impl.identifiers.NamespaceConverter;
032import org.fcrepo.kernel.impl.identifiers.NodeResourceConverter;
033
034import javax.jcr.RepositoryException;
035import javax.jcr.Session;
036
037import java.util.List;
038
039/**
040 * A very simple {@link IdentifierConverter} which translates JCR paths into Fedora subjects with
041 * a configurable resource namespace (e.g., a baseURL).  When a REST API context is available for
042 * constructing URIs, org.fcrepo.http.commons.api.rdf.HttpResourceConverter should be used instead.
043 *
044 * @author barmintor
045 * @author ajs6f
046 * @author escowles
047 * @since 2015-04-24
048 */
049public class PrefixingIdentifierTranslator extends IdentifierConverter<Resource, FedoraResource> {
050
051
052    private static final NodeResourceConverter nodeResourceConverter = new NodeResourceConverter();
053
054    private final String resourceNamespace;
055    private final Session session;
056
057    /**
058     * Construct the graph with the provided resource namespace, which will translate JCR paths into
059     * URIs prefixed with that namespace.  Should only be used when a REST API context is not available
060     * for constructing URIs.
061     * @param session Session to lookup nodes
062     * @param resourceNamespace Resource namespace (i.e., base URL)
063    **/
064    public PrefixingIdentifierTranslator(final Session session, final String resourceNamespace) {
065        this.session = session;
066        this.resourceNamespace = resourceNamespace;
067        setTranslationChain();
068    }
069
070
071    protected Converter<String, String> forward = identity();
072    protected Converter<String, String> reverse = identity();
073
074    /*
075     * TODO: much of what happens with chains of translators inside these converters should be factored
076     * out into some abstract class, or post Java 8, default implementation.
077     */
078    private void setTranslationChain() {
079
080        for (final Converter<String, String> t : minimalTranslationChain) {
081            forward = forward.andThen(t);
082        }
083        for (final Converter<String, String> t : Lists.reverse(minimalTranslationChain)) {
084            reverse = reverse.andThen(t.reverse());
085        }
086    }
087
088
089    @SuppressWarnings("unchecked")
090    private static final List<Converter<String, String>> minimalTranslationChain =
091            newArrayList((Converter<String, String>) new NamespaceConverter(),
092                    (Converter<String, String>) new HashConverter()
093            );
094
095    @Override
096    protected FedoraResource doForward(final Resource subject) {
097        try {
098            if (!inDomain(subject)) {
099                throw new RepositoryRuntimeException("Subject " + subject + " is not in this repository");
100            }
101
102            return nodeResourceConverter.convert(session.getNode(asString(subject)));
103        } catch (final RepositoryException e) {
104            throw new RepositoryRuntimeException(e);
105        }
106    }
107
108    @Override
109    protected Resource doBackward(final FedoraResource resource) {
110        final String absPath = resource.getPath();
111
112        return toDomain(absPath);
113    }
114
115    @Override
116    public boolean inDomain(final Resource subject) {
117        return subject.isURIResource() && subject.getURI().startsWith(resourceNamespace);
118    }
119
120    @Override
121    public Resource toDomain(final String absPath) {
122        final String relativePath;
123
124        if (absPath.startsWith("/")) {
125            relativePath = absPath.substring(1);
126        } else {
127            relativePath = absPath;
128        }
129        return createResource(resourceNamespace + reverse.convert(relativePath));
130    }
131
132    @Override
133    public String asString(final Resource subject) {
134        if (!inDomain(subject)) {
135            return null;
136        }
137
138        final String path = subject.getURI().substring(resourceNamespace.length() - 1);
139
140        final String absPath = forward.convert(path);
141
142        if (absPath.isEmpty()) {
143            return "/";
144        }
145        return absPath;
146    }
147
148}