* Licensed to the Apache Software Foundation (ASF) under one

* or more contributor license agreements.  See the NOTICE file

* distributed with this work for additional information

* regarding copyright ownership.  The ASF licenses this file

* to you 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.

*/

* This class implements {@link com.hp.hpl.jena.graph.Graph} basing

* on a {@link org.apache.clerezza.rdf.core.TripleCollection}. A <code>JenaGraph</code>

* can be instanciated using mutable <code>TripleCollection</code>s

* (i.e. <code>MGraph</code>S) as well as immutable ones (i.e. <code>Graph</code>),

* an attempt to add or remove triples to a <code>JenaGraph</code> based on

* an immutable <code>TripleCollection</code> will result in

* a <code>UnsupportedOperationException</code> being thrown by the

* underlying <code>TripleCollection</code>.

*

* Typically an instance of this class is passed as argument

* to {@link com.hp.hpl.jena.rdf.model.ModelFactory#createModelForGraph} to

* get a <code>Model</code>.

*

* @author reto

*/

    final TripleCollection graph;

    final BidiMap<BNode, Node> tria2JenaBNodes = new BidiMapImpl<BNode, Node>();

    final Jena2TriaUtil jena2TriaUtil =

            new Jena2TriaUtil(tria2JenaBNodes.inverse());

    final Tria2JenaUtil tria2JenaUtil =

            new Tria2JenaUtil(tria2JenaBNodes);

    public JenaGraph(TripleCollection graph) {

        this.graph = graph;

    }

    @Override

    public void performAdd(com.hp.hpl.jena.graph.Triple triple) {

        graph.add(jena2TriaUtil.convertTriple(triple));

    }

    @Override

    public void performDelete(com.hp.hpl.jena.graph.Triple triple) {

        Triple clerezzaTriple = jena2TriaUtil.convertTriple(triple);

        if (clerezzaTriple != null) {

            graph.remove(clerezzaTriple);

        }

    }

    private Iterator<com.hp.hpl.jena.graph.Triple> convert(

            final Iterator<Triple> base) {

        return new Iterator<com.hp.hpl.jena.graph.Triple>() {

            Triple lastReturned = null;

            @Override

            public boolean hasNext() {

                return base.hasNext();

            }

            @Override

            public com.hp.hpl.jena.graph.Triple next() {

                Triple baseNext = base.next();

                lastReturned = baseNext;

                return (baseNext == null) ? null : tria2JenaUtil.convertTriple(baseNext, true);

            }

            @Override

            public void remove() {

                graph.remove(lastReturned);

            }

        };

    }

    /**

     * An iterator (over a filtered TripleCollection) that can return its next element as a triple. As parameter a tripleMatch is required.

     * Triple matches are defined by subject, predicate, and object.

     * @param m

     * @return TripleCollection

     */

    private Iterator<Triple> filter(TripleMatch m) {

        NonLiteral subject = null;

        UriRef predicate = null;

        Resource object = null;

        if (m.getMatchSubject() != null) {

            if (m.getMatchSubject().isLiteral()) {

                return Collections.EMPTY_SET.iterator();

            }

            subject = jena2TriaUtil.convertNonLiteral(m.getMatchSubject());

            if (subject == null) {

                return Collections.EMPTY_SET.iterator();

            }

        }

        if (m.getMatchObject() != null) {

            object = jena2TriaUtil.convertJenaNode2Resource(m.getMatchObject());

            if (object == null) {

                return Collections.EMPTY_SET.iterator();

            }

        }       

        if (m.getMatchPredicate() != null) {

            if (!m.getMatchPredicate().isURI()) {

                return Collections.EMPTY_SET.iterator();

            }

            predicate = jena2TriaUtil.convertJenaUri2UriRef(m.getMatchPredicate());

        }

        try {

            return graph.filter(subject, predicate, object);

        } catch (IllegalArgumentException e) {

            //jena serializers are known to query with invalid URIs

            //see http://tech.groups.yahoo.com/group/jena-dev/message/37221

            //an invalid Uris hould not be in the graph and thus lead to an

            //empty result

            return new HashSet<Triple>().iterator();

        }

    }

    @Override

    protected ExtendedIterator graphBaseFind(TripleMatch m) {

        return new TrackingTripleIterator(convert(filter(m)));

    }

}