EDIT

// $Id$

/**

 * Copyright (C) 2014 EDIT

 * European Distributed Institute of Taxonomy

 * http://www.e-taxonomy.eu

 *

 * The contents of this file are subject to the Mozilla Public License Version 1.1

 * See LICENSE.TXT at the top of this package for the full license terms.

 */

package eu.etaxonomy.taxeditor.remoting.cache;

import java.util.ArrayList;

import java.util.Collection;

import java.util.HashSet;

import java.util.List;

import java.util.Map;

import java.util.Set;

import net.sf.ehcache.Cache;

import net.sf.ehcache.CacheManager;

import net.sf.ehcache.Element;

import net.sf.ehcache.Status;

import net.sf.ehcache.config.CacheConfiguration;

import net.sf.ehcache.config.SizeOfPolicyConfiguration;

import net.sf.ehcache.statistics.LiveCacheStatistics;

import org.apache.log4j.Logger;

import eu.etaxonomy.cdm.api.application.CdmApplicationState;

import eu.etaxonomy.cdm.api.cache.CdmServiceCacher;

import eu.etaxonomy.cdm.api.service.UpdateResult;

import eu.etaxonomy.cdm.api.service.dto.CdmEntityIdentifier;

import eu.etaxonomy.cdm.model.ICdmCacher;

import eu.etaxonomy.cdm.model.common.CdmBase;

import eu.etaxonomy.taxeditor.session.ICdmEntitySessionManager;

/**

 *

 * This cache guarantees that

 *  - all objects put will be ancestors of CdmBase

 *  - all CdmBase objects in the cache will be already de-proxied

 *  - after any CdmBase object is put in the cache,

 *  all non-null / non-proxy CdmBase objects in the sub-graph

 *  will also be present in the cache.

 *

 * @author cmathew

 * @date 14 Oct 2014

 *

 */

public class CdmTransientEntityCacher implements ICdmCacher {

    private static final Logger logger = Logger.getLogger(CdmTransientEntityCacher.class);

    private final ICdmEntitySessionManager cdmEntitySessionManager;

    private static CdmServiceCacher cdmServiceCacher;

    private final String cacheId;

    private final Cache cache;

    private final CacheLoader cacheLoader;

    public CdmTransientEntityCacher(String cacheId, ICdmEntitySessionManager cdmEntitySessionManager) {

        this.cacheId = cacheId;

        cache = new Cache(getEntityCacheConfiguration(cacheId));

        CacheManager.create().addCache(cache);

        this.cdmEntitySessionManager = cdmEntitySessionManager;

        cacheLoader = new CacheLoader(this);

    }

    public CdmTransientEntityCacher(Object sessionOwner, ICdmEntitySessionManager cdmEntitySessionManager) {

        this(generateCacheId(sessionOwner), cdmEntitySessionManager);

    }

    public static String generateCacheId(Object sessionOwner) {

        return sessionOwner.getClass().getName() +  String.valueOf(sessionOwner.hashCode());

    }

    /**

     * Returns the default cache configuration.

     *

     * @return

     */

    private CacheConfiguration getEntityCacheConfiguration(String cacheId) {

        SizeOfPolicyConfiguration sizeOfConfig = new SizeOfPolicyConfiguration();

        sizeOfConfig.setMaxDepth(10000);

        sizeOfConfig.setMaxDepthExceededBehavior("abort");

        return new CacheConfiguration(cacheId, 0)

        .eternal(true)

        .statistics(true)

        .sizeOfPolicy(sizeOfConfig)

        .overflowToOffHeap(false);

    }

    public static void setDefaultCacher(CdmServiceCacher css) {

        cdmServiceCacher = css;

    }

    public LiveCacheStatistics getCacheStatistics() {

        if(cache.getStatus() == Status.STATUS_ALIVE) {

            return cache.getLiveCacheStatistics();

        }

        return null;

    }

    /**

     * Returns the cache corresponding to the cache id

     *

     * @param cacheId

     * @return

     */

    private Cache getCache() {

        return  CacheManager.create().getCache(cacheId);

    }

    public <T extends Object> T load(T obj, boolean update) {

        return cacheLoader.load(obj, true, update);

    }

    public <T extends Object> Map<T,T> load(Map<T,T> map, boolean update){

        return cacheLoader.load(map, true, update);

    }

    public <T extends Object> Collection<T> load(Collection<T> collection, boolean update){

        return cacheLoader.load(collection, true, update);

    }

    public CdmBase load(CdmBase cdmEntity, boolean update) {

        return cacheLoader.load(cdmEntity, true, update);

    }

    private CdmBase load(CdmEntityIdentifier cei, boolean update) {

        return CdmApplicationState.getCommonService().findWithUpdate(cei.getCdmClass(), cei.getId());

    }

    public UpdateResult load(UpdateResult result, boolean update) {

        // probably a good time to broadcast to other sessions

        Set<CdmBase> updatedObjects = result.getUpdatedObjects();

        Set<CdmBase> reloadedObjects = new HashSet<CdmBase>();

        Set<CdmEntityIdentifier> updatedCdmIds = result.getUpdatedCdmIds();

        boolean updatedCdmIdsIsEmpty = updatedCdmIds.isEmpty();

        // if the cdm identifier set contains identifiers of objects already

        // present in the updated objects set reomve them

        for(CdmBase updatedObject : updatedObjects) {

            if(updatedObject != null && exists(new CdmEntityCacheKey(updatedObject.getClass(), updatedObject.getId()))) {

                CdmEntityIdentifier cdmEntityIdentifier = new CdmEntityIdentifier(updatedObject.getId(), updatedObject.getClass());

                if(!updatedCdmIdsIsEmpty && updatedCdmIds.contains(cdmEntityIdentifier)) {

                    updatedCdmIds.remove(cdmEntityIdentifier);

                }

                reloadedObjects.add(cacheLoader.load(updatedObject, true, update));

            }

        }

        // remote load cdm identifiers of objects which already exist

        // in the cache

        for(CdmEntityIdentifier cei : updatedCdmIds) {

            if(exists(new CdmEntityCacheKey(cei.getCdmClass(), cei.getId()))) {

                reloadedObjects.add(load(cei, update));

            }

        }

        updatedObjects.clear();

        result.addUpdatedObjects(reloadedObjects);

        return result;

    }

    public CdmModelFieldPropertyFromClass getFromCdmlibModelCache(String className) {

        return cacheLoader.getFromCdmlibModelCache(className);

    }

    @Override

    public void put(CdmBase cdmEntity) {

        CdmBase cachedCdmEntity = cdmServiceCacher.load(cdmEntity);

        if(cachedCdmEntity != null) {

            logger.info("Cdm Entity with id : " + cdmEntity.getId() + " already exists in permanent cache. Ignoring put.");

            return;

        }

        CdmEntityCacheKey id = new CdmEntityCacheKey(cdmEntity);

        cachedCdmEntity = getFromCache(id);

        if(cachedCdmEntity == null) {

            getCache().put(new Element(id, cdmEntity));

            cdmEntity.initListener();

            logger.info(" - object of type " + cdmEntity.getClass().getName() + " with id " + cdmEntity.getId() + " put in cache");

            return;

        }

        logger.info(" - object of type " + cdmEntity.getClass().getName() + " with id " + cdmEntity.getId() + " already exists");

    }

    private Element getCacheElement(CdmEntityCacheKey key) {

        return getCache().get(key);

    }

    public CdmBase getFromCache(CdmEntityCacheKey id) {

        Element e = getCacheElement(id);

        if (e == null) {

            return null;

        } else {

            return (CdmBase) e.getObjectValue();

        }

    }

    public CdmBase getFromCache(Class<? extends CdmBase> clazz, int id) {

        CdmEntityCacheKey cacheId = generateKey(clazz,id);

        return getFromCache(cacheId);

    }

    @Override

    public CdmBase getFromCache(CdmBase cdmBase) {

        CdmEntityCacheKey cacheId = generateKey((CdmBase)ProxyUtils.deproxy(cdmBase));

        // first try this cache

        CdmBase  cachedCdmEntity = getFromCache(cacheId);

        if(cachedCdmEntity == null) {

            // ... then try the permanent cache

            cachedCdmEntity = cdmServiceCacher.getFromCache(cdmBase.getUuid());

        }

        return cachedCdmEntity;

    }

    public CdmBase getFromCache(CdmBase cdmBase, Class<? extends CdmBase> clazz) {

        cdmBase = CdmBase.deproxy(cdmBase, clazz);

        return getFromCache(cdmBase);

    }

    public List<CdmBase> getAllEntities() {

        List<CdmBase> entities = new ArrayList<CdmBase>();

        Map<String, CdmBase> elementsMap = getCache().getAllWithLoader(getCache().getKeys(), null);

        for (Map.Entry<String, CdmBase> entry : elementsMap.entrySet()) {

            entities.add(entry.getValue());

        }

        return entities;

    }

    public boolean exists(CdmEntityCacheKey key) {

        return (getCacheElement(key) != null);

    }

    public boolean existsAndIsNotNull(CdmEntityCacheKey id) {

        return getFromCache(id) != null;

    }

    public void clear() {

        cache.removeAll();

    }

    public void dispose() {

        CacheManager.create().removeCache(cache.getName());

        cache.dispose();

    }

    public static CdmEntityCacheKey generateKey(Class<? extends CdmBase> clazz, int id) {

        return new CdmEntityCacheKey(clazz, id);

    }

    public static CdmEntityCacheKey generateKey(CdmBase cdmBase) {

        Class<? extends CdmBase> entityClass = cdmBase.getClass();

        int id = cdmBase.getId();

        return new CdmEntityCacheKey(entityClass, id);

    }

    /* (non-Javadoc)

     * @see eu.etaxonomy.cdm.model.ICdmCacher#load(eu.etaxonomy.cdm.model.common.CdmBase)

     */

    @Override

    public CdmBase load(CdmBase cdmEntity) {

        return load(cdmEntity, true);

    }

    /* (non-Javadoc)

     * @see eu.etaxonomy.cdm.model.ICdmCacher#isCachable(eu.etaxonomy.cdm.model.common.CdmBase)

     */

    @Override

    public boolean isCachable(CdmBase cdmEntity) {

        return true;

    }

    /* (non-Javadoc)

     * @see eu.etaxonomy.cdm.model.ICdmCacher#exists(eu.etaxonomy.cdm.model.common.CdmBase)

     */

    @Override

    public boolean exists(CdmBase cdmBase) {

        return exists(generateKey(cdmBase));

    }

}