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/*
 * This file is part of the OWL API.
 *
 * The contents of this file are subject to the LGPL License, Version 3.0.
 *
 * Copyright (C) 2011, The University of Manchester
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see http://www.gnu.org/licenses/.
 *
 *
 * Alternatively, the contents of this file may be used under the terms of the Apache License, Version 2.0
 * in which case, the provisions of the Apache License Version 2.0 are applicable instead of those above.
 *
 * Copyright 2011, University of Manchester
 *
 * 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 org.semanticweb.owlapi.util;

import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.semanticweb.owlapi.model.OWLEntity;

/** Author: Matthew Horridge

 * The University Of Manchester

 * Bio-Health Informatics Group

 * Date: 18-Apr-2007

 * 

 * 
 * A bidirectional short form provider that caches entity short forms. The
 * provider has various methods to add, remove, update entities in the cache and
 * also to rebuild the cache from scratch. */
public abstract class CachingBidirectionalShortFormProvider implements
        BidirectionalShortFormProvider {
    private final Map> shortForm2EntityMap;
    private final Map entity2ShortFormMap;

    protected CachingBidirectionalShortFormProvider() {
        shortForm2EntityMap = new HashMap>();
        entity2ShortFormMap = new HashMap();
    }

    /** Generates the short form for the specified entity. This short form will
     * be cached so that it can be retrieved efficiently and so that the entity
     * can be obtained from the short form. If the short form for the entity
     * changes then the cach must explicilty be updated using the
     * update method.
     * 
     * @param entity
     *            The entity whose short form should be generated. */
    protected abstract String generateShortForm(OWLEntity entity);

    @Override
    public Set getShortForms() {
        return CollectionFactory
                .getCopyOnRequestSetFromMutableCollection(shortForm2EntityMap.keySet());
    }

    /** Rebuilds the cache using entities obtained from the specified entity set
     * provider.
     * 
     * @param entitySetProvider
     *            The OWLEntitySetProvider that should be used to
     *            obtain the entities whose short forms will be cached. */
    // XXX not in the interface
    @Deprecated
    public void rebuild(OWLEntitySetProvider entitySetProvider) {
        shortForm2EntityMap.clear();
        entity2ShortFormMap.clear();
        for (OWLEntity entity : entitySetProvider.getEntities()) {
            add(entity);
        }
    }

    /** Adds an entity to the cache.
     * 
     * @param entity
     *            The entity to be added to the cache - the short form will
     *            automatically be generated and added to the cache. */
    public void add(OWLEntity entity) {
        String shortForm = generateShortForm(entity);
        entity2ShortFormMap.put(entity, shortForm);
        Set entities = shortForm2EntityMap.get(shortForm);
        if (entities == null) {
            // XXX what's the use of size 1? How likely it is to grow large?
            entities = new HashSet(1);
        }
        entities.add(entity);
        shortForm2EntityMap.put(shortForm, entities);
    }

    /** Removes an entity and its short form from the cache.
     * 
     * @param entity
     *            The entity to be removed. */
    // XXX not in the interface
    @Deprecated
    public void remove(OWLEntity entity) {
        String shortForm = entity2ShortFormMap.remove(entity);
        if (shortForm != null) {
            shortForm2EntityMap.remove(shortForm);
        }
    }

    /** If the short form for a cached entity has changed then this method may be
     * used to update the cached short form mapping for the entity.
     * 
     * @param entity
     *            The entity whose short form should be updated. */
    // XXX not in the interface
    @Deprecated
    public void update(OWLEntity entity) {
        remove(entity);
        add(entity);
    }

    @Override
    public Set getEntities(String shortForm) {
        Set entities = shortForm2EntityMap.get(shortForm);
        if (entities != null) {
            return CollectionFactory.getCopyOnRequestSetFromImmutableCollection(entities);
        } else {
            return Collections.emptySet();
        }
    }

    @Override
    public OWLEntity getEntity(String shortForm) {
        Set entities = shortForm2EntityMap.get(shortForm);
        if (entities != null) {
            if (!entities.isEmpty()) {
                return entities.iterator().next();
            } else {
                return null;
            }
        } else {
            return null;
        }
    }

    @Override
    public String getShortForm(OWLEntity entity) {
        String sf = entity2ShortFormMap.get(entity);
        if (sf != null) {
            return sf;
        } else {
            return generateShortForm(entity);
        }
    }

    @Override
    public void dispose() {
        shortForm2EntityMap.clear();
        entity2ShortFormMap.clear();
    }
}