/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2012, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.engine.internal;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.hibernate.AssertionFailure;
import org.hibernate.cache.spi.NaturalIdCacheKey;
import org.hibernate.cache.spi.access.NaturalIdRegionAccessStrategy;
import org.hibernate.engine.spi.PersistenceContext;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.engine.spi.SessionImplementor;
import org.hibernate.persister.entity.EntityPersister;
import org.hibernate.type.Type;

import org.jboss.logging.Logger;

Maintains a PersistenceContext-level 2-way cross-reference (xref) between the identifiers and natural ids of entities associated with the PersistenceContext. 
 Most operations resolve the proper NaturalIdResolutionCache to use based on the persister and simply delegate calls there. 
Author:
Steve Ebersole/**
 * Maintains a {@link org.hibernate.engine.spi.PersistenceContext}-level 2-way cross-reference (xref) between the 
 * identifiers and natural ids of entities associated with the PersistenceContext.
 * <p/>
 * Most operations resolve the proper {@link NaturalIdResolutionCache} to use based on the persister and 
 * simply delegate calls there.
 * 
 * @author Steve Ebersole
 */
public class NaturalIdXrefDelegate {
	private static final Logger LOG = Logger.getLogger( NaturalIdXrefDelegate.class );

	private final StatefulPersistenceContext persistenceContext;
	private final ConcurrentHashMap<EntityPersister, NaturalIdResolutionCache> naturalIdResolutionCacheMap = new ConcurrentHashMap<EntityPersister, NaturalIdResolutionCache>();

	
Constructs a NaturalIdXrefDelegate
Params:
persistenceContext – The persistence context that owns this delegate/**
	 * Constructs a NaturalIdXrefDelegate
	 *
	 * @param persistenceContext The persistence context that owns this delegate
	 */
	public NaturalIdXrefDelegate(StatefulPersistenceContext persistenceContext) {
		this.persistenceContext = persistenceContext;
	}

	
Access to the session (via the PersistenceContext) to which this delegate ultimately belongs.
Returns:
The session/**
	 * Access to the session (via the PersistenceContext) to which this delegate ultimately belongs.
	 *
	 * @return The session
	 */
	protected SessionImplementor session() {
		return persistenceContext.getSession();
	}

	
Creates needed cross-reference entries between the given primary (pk) and natural (naturalIdValues) key values for the given persister. Returns an indication of whether entries were actually made. If those values already existed as an entry, false would be returned here. 
Params:
persister – The persister representing the entity type.
pk – The primary key value
naturalIdValues – The natural id value(s)
Returns:
true if a new entry was actually added; false otherwise./**
	 * Creates needed cross-reference entries between the given primary (pk) and natural (naturalIdValues) key values
	 * for the given persister.  Returns an indication of whether entries were actually made.  If those values already
	 * existed as an entry, {@code false} would be returned here.
	 *
	 * @param persister The persister representing the entity type.
	 * @param pk The primary key value
	 * @param naturalIdValues The natural id value(s)
	 *
	 * @return {@code true} if a new entry was actually added; {@code false} otherwise.
	 */
	public boolean cacheNaturalIdCrossReference(EntityPersister persister, Serializable pk, Object[] naturalIdValues) {
		validateNaturalId( persister, naturalIdValues );

		NaturalIdResolutionCache entityNaturalIdResolutionCache = naturalIdResolutionCacheMap.get( persister );
		if ( entityNaturalIdResolutionCache == null ) {
			entityNaturalIdResolutionCache = new NaturalIdResolutionCache( persister );
			NaturalIdResolutionCache previousInstance = naturalIdResolutionCacheMap.putIfAbsent( persister, entityNaturalIdResolutionCache );
			if ( previousInstance != null ) {
				entityNaturalIdResolutionCache = previousInstance;
			}
		}
		return entityNaturalIdResolutionCache.cache( pk, naturalIdValues );
	}

	
Handle removing cross reference entries for the given natural-id/pk combo
Params:
persister – The persister representing the entity type.
pk – The primary key value
naturalIdValues – The natural id value(s)
Returns:
The cached values, if any.  May be different from incoming values./**
	 * Handle removing cross reference entries for the given natural-id/pk combo
	 *
	 * @param persister The persister representing the entity type.
	 * @param pk The primary key value
	 * @param naturalIdValues The natural id value(s)
	 * 
	 * @return The cached values, if any.  May be different from incoming values.
	 */
	public Object[] removeNaturalIdCrossReference(EntityPersister persister, Serializable pk, Object[] naturalIdValues) {
		persister = locatePersisterForKey( persister );
		validateNaturalId( persister, naturalIdValues );

		final NaturalIdResolutionCache entityNaturalIdResolutionCache = naturalIdResolutionCacheMap.get( persister );
		Object[] sessionCachedNaturalIdValues = null;
		if ( entityNaturalIdResolutionCache != null ) {
			final CachedNaturalId cachedNaturalId = entityNaturalIdResolutionCache.pkToNaturalIdMap
					.remove( pk );
			if ( cachedNaturalId != null ) {
				entityNaturalIdResolutionCache.naturalIdToPkMap.remove( cachedNaturalId );
				sessionCachedNaturalIdValues = cachedNaturalId.getValues();
			}
		}

		if ( persister.hasNaturalIdCache() ) {
			final NaturalIdRegionAccessStrategy naturalIdCacheAccessStrategy = persister
					.getNaturalIdCacheAccessStrategy();
			final NaturalIdCacheKey naturalIdCacheKey = new NaturalIdCacheKey( naturalIdValues, persister, session() );
			naturalIdCacheAccessStrategy.evict( naturalIdCacheKey );

			if ( sessionCachedNaturalIdValues != null
					&& !Arrays.equals( sessionCachedNaturalIdValues, naturalIdValues ) ) {
				final NaturalIdCacheKey sessionNaturalIdCacheKey = new NaturalIdCacheKey( sessionCachedNaturalIdValues, persister, session() );
				naturalIdCacheAccessStrategy.evict( sessionNaturalIdCacheKey );
			}
		}

		return sessionCachedNaturalIdValues;
	}

	
Are the naturals id values cached here (if any) for the given persister+pk combo the same as the given values?
Params:
persister – The persister representing the entity type.
pk – The primary key value
naturalIdValues – The natural id value(s) to check
Returns:
true if the given naturalIdValues match the current cached values; false otherwise./**
	 * Are the naturals id values cached here (if any) for the given persister+pk combo the same as the given values?
	 *
	 * @param persister The persister representing the entity type.
	 * @param pk The primary key value
	 * @param naturalIdValues The natural id value(s) to check
	 * 
	 * @return {@code true} if the given naturalIdValues match the current cached values; {@code false} otherwise.
	 */
	public boolean sameAsCached(EntityPersister persister, Serializable pk, Object[] naturalIdValues) {
		final NaturalIdResolutionCache entityNaturalIdResolutionCache = naturalIdResolutionCacheMap.get( persister );
		return entityNaturalIdResolutionCache != null
				&& entityNaturalIdResolutionCache.sameAsCached( pk, naturalIdValues );
	}

	
It is only valid to define natural ids at the root of an entity hierarchy.  This method makes sure we are 
using the root persister.
Params:
persister – The persister representing the entity type.
Returns:
The root persister./**
	 * It is only valid to define natural ids at the root of an entity hierarchy.  This method makes sure we are 
	 * using the root persister.
	 *
	 * @param persister The persister representing the entity type.
	 * 
	 * @return The root persister.
	 */
	protected EntityPersister locatePersisterForKey(EntityPersister persister) {
		return persistenceContext.getSession().getFactory().getEntityPersister( persister.getRootEntityName() );
	}

	
Invariant validate of the natural id.  Checks include

    
that the entity defines a natural id
    
the number of natural id values matches the expected number

Params:
persister – The persister representing the entity type.
naturalIdValues – The natural id values/**
	 * Invariant validate of the natural id.  Checks include<ul>
	 *     <li>that the entity defines a natural id</li>
	 *     <li>the number of natural id values matches the expected number</li>
	 * </ul>
	 *
	 * @param persister The persister representing the entity type.
	 * @param naturalIdValues The natural id values
	 */
	protected void validateNaturalId(EntityPersister persister, Object[] naturalIdValues) {
		if ( !persister.hasNaturalIdentifier() ) {
			throw new IllegalArgumentException( "Entity did not define a natrual-id" );
		}
		if ( persister.getNaturalIdentifierProperties().length != naturalIdValues.length ) {
			throw new IllegalArgumentException( "Mismatch between expected number of natural-id values and found." );
		}
	}

	
Given a persister and primary key, find the locally cross-referenced natural id.
Params:
persister – The persister representing the entity type.
pk – The entity primary key
Returns:
The corresponding cross-referenced natural id values, or null if none/**
	 * Given a persister and primary key, find the locally cross-referenced natural id.
	 *
	 * @param persister The persister representing the entity type.
	 * @param pk The entity primary key
	 * 
	 * @return The corresponding cross-referenced natural id values, or {@code null} if none 
	 */
	public Object[] findCachedNaturalId(EntityPersister persister, Serializable pk) {
		persister = locatePersisterForKey( persister );
		final NaturalIdResolutionCache entityNaturalIdResolutionCache = naturalIdResolutionCacheMap.get( persister );
		if ( entityNaturalIdResolutionCache == null ) {
			return null;
		}

		final CachedNaturalId cachedNaturalId = entityNaturalIdResolutionCache.pkToNaturalIdMap.get( pk );
		if ( cachedNaturalId == null ) {
			return null;
		}

		return cachedNaturalId.getValues();
	}

	
Given a persister and natural-id value(s), find the locally cross-referenced primary key. Will return NaturalIdHelper.INVALID_NATURAL_ID_REFERENCE if the given natural ids are known to be invalid (see stashInvalidNaturalIdReference). 
Params:
persister – The persister representing the entity type.
naturalIdValues – The natural id value(s)
Returns:
The corresponding cross-referenced primary key, NaturalIdHelper.INVALID_NATURAL_ID_REFERENCE, or null if none/**
	 * Given a persister and natural-id value(s), find the locally cross-referenced primary key.  Will return
	 * {@link PersistenceContext.NaturalIdHelper#INVALID_NATURAL_ID_REFERENCE} if the given natural ids are known to
	 * be invalid (see {@link #stashInvalidNaturalIdReference}).
	 *
	 * @param persister The persister representing the entity type.
	 * @param naturalIdValues The natural id value(s)
	 * 
	 * @return The corresponding cross-referenced primary key, 
	 * 		{@link PersistenceContext.NaturalIdHelper#INVALID_NATURAL_ID_REFERENCE},
	 * 		or {@code null} if none 
	 */
	public Serializable findCachedNaturalIdResolution(EntityPersister persister, Object[] naturalIdValues) {
		persister = locatePersisterForKey( persister );
		validateNaturalId( persister, naturalIdValues );

		NaturalIdResolutionCache entityNaturalIdResolutionCache = naturalIdResolutionCacheMap.get( persister );

		Serializable pk;
		final CachedNaturalId cachedNaturalId = new CachedNaturalId( persister, naturalIdValues );
		if ( entityNaturalIdResolutionCache != null ) {
			pk = entityNaturalIdResolutionCache.naturalIdToPkMap.get( cachedNaturalId );

			// Found in session cache
			if ( pk != null ) {
				if ( LOG.isTraceEnabled() ) {
					LOG.trace(
							"Resolved natural key -> primary key resolution in session cache: " +
									persister.getRootEntityName() + "#[" +
									Arrays.toString( naturalIdValues ) + "]"
					);
				}

				return pk;
			}

			// if we did not find a hit, see if we know about these natural ids as invalid...
			if ( entityNaturalIdResolutionCache.containsInvalidNaturalIdReference( naturalIdValues ) ) {
				return PersistenceContext.NaturalIdHelper.INVALID_NATURAL_ID_REFERENCE;
			}
		}

		// Session cache miss, see if second-level caching is enabled
		if ( !persister.hasNaturalIdCache() ) {
			return null;
		}

		// Try resolution from second-level cache
		final NaturalIdCacheKey naturalIdCacheKey = new NaturalIdCacheKey( naturalIdValues, persister, session() );

		final NaturalIdRegionAccessStrategy naturalIdCacheAccessStrategy = persister.getNaturalIdCacheAccessStrategy();
		pk = CacheHelper.fromSharedCache( session(), naturalIdCacheKey, naturalIdCacheAccessStrategy );

		// Found in second-level cache, store in session cache
		final SessionFactoryImplementor factory = session().getFactory();
		if ( pk != null ) {
			if ( factory.getStatistics().isStatisticsEnabled() ) {
				factory.getStatisticsImplementor().naturalIdCacheHit(
						naturalIdCacheAccessStrategy.getRegion().getName()
				);
			}

			if ( LOG.isTraceEnabled() ) {
				// protected to avoid Arrays.toString call unless needed
				LOG.tracef(
						"Found natural key [%s] -> primary key [%s] xref in second-level cache for %s",
						Arrays.toString( naturalIdValues ),
						pk,
						persister.getRootEntityName()
				);
			}

			if ( entityNaturalIdResolutionCache == null ) {
				entityNaturalIdResolutionCache = new NaturalIdResolutionCache( persister );
				NaturalIdResolutionCache existingCache = naturalIdResolutionCacheMap.putIfAbsent( persister, entityNaturalIdResolutionCache );
				if ( existingCache != null ) {
					entityNaturalIdResolutionCache = existingCache;
				}
			}

			entityNaturalIdResolutionCache.pkToNaturalIdMap.put( pk, cachedNaturalId );
			entityNaturalIdResolutionCache.naturalIdToPkMap.put( cachedNaturalId, pk );
		}
		else if ( factory.getStatistics().isStatisticsEnabled() ) {
			factory.getStatisticsImplementor().naturalIdCacheMiss( naturalIdCacheAccessStrategy.getRegion().getName() );
		}

		return pk;
	}

	
Return all locally cross-referenced primary keys for the given persister.  Used as part of load
synchronization process.
Params:
persister – The persister representing the entity type.
See Also:
NaturalIdLoadAccess.setSynchronizationEnabled
Returns:
The primary keys/**
	 * Return all locally cross-referenced primary keys for the given persister.  Used as part of load
	 * synchronization process.
	 *
	 * @param persister The persister representing the entity type.
	 * 
	 * @return The primary keys
	 * 
	 * @see org.hibernate.NaturalIdLoadAccess#setSynchronizationEnabled
	 */
	public Collection<Serializable> getCachedPkResolutions(EntityPersister persister) {
		persister = locatePersisterForKey( persister );

		Collection<Serializable> pks = null;

		final NaturalIdResolutionCache entityNaturalIdResolutionCache = naturalIdResolutionCacheMap.get( persister );
		if ( entityNaturalIdResolutionCache != null ) {
			pks = entityNaturalIdResolutionCache.pkToNaturalIdMap.keySet();
		}

		if ( pks == null || pks.isEmpty() ) {
			return java.util.Collections.emptyList();
		}
		else {
			return java.util.Collections.unmodifiableCollection( pks );
		}
	}

	
As part of "load synchronization process", if a particular natural id is found to have changed we need to track
its invalidity until after the next flush.  This method lets the "load synchronization process" indicate
when it has encountered such changes.
Params:
persister – The persister representing the entity type.
invalidNaturalIdValues – The "old" natural id values.
See Also:
NaturalIdLoadAccess.setSynchronizationEnabled/**
	 * As part of "load synchronization process", if a particular natural id is found to have changed we need to track
	 * its invalidity until after the next flush.  This method lets the "load synchronization process" indicate
	 * when it has encountered such changes.
	 *
	 * @param persister The persister representing the entity type.
	 * @param invalidNaturalIdValues The "old" natural id values.
	 *
	 * @see org.hibernate.NaturalIdLoadAccess#setSynchronizationEnabled
	 */
	public void stashInvalidNaturalIdReference(EntityPersister persister, Object[] invalidNaturalIdValues) {
		persister = locatePersisterForKey( persister );

		final NaturalIdResolutionCache entityNaturalIdResolutionCache = naturalIdResolutionCacheMap.get( persister );
		if ( entityNaturalIdResolutionCache == null ) {
			throw new AssertionFailure( "Expecting NaturalIdResolutionCache to exist already for entity " + persister.getEntityName() );
		}

		entityNaturalIdResolutionCache.stashInvalidNaturalIdReference( invalidNaturalIdValues );
	}

	
Again, as part of "load synchronization process" we need to also be able to clear references to these
known-invalid natural-ids after flush.  This method exposes that capability.
/**
	 * Again, as part of "load synchronization process" we need to also be able to clear references to these
	 * known-invalid natural-ids after flush.  This method exposes that capability.
	 */
	public void unStashInvalidNaturalIdReferences() {
		for ( NaturalIdResolutionCache naturalIdResolutionCache : naturalIdResolutionCacheMap.values() ) {
			naturalIdResolutionCache.unStashInvalidNaturalIdReferences();
		}
	}

	
Used to put natural id values into collections.  Useful mainly to apply equals/hashCode implementations.
/**
	 * Used to put natural id values into collections.  Useful mainly to apply equals/hashCode implementations.
	 */
	private static class CachedNaturalId implements Serializable {
		private final EntityPersister persister;
		private final Object[] values;
		private final Type[] naturalIdTypes;
		private int hashCode;

		public CachedNaturalId(EntityPersister persister, Object[] values) {
			this.persister = persister;
			this.values = values;

			final int prime = 31;
			int hashCodeCalculation = 1;
			hashCodeCalculation = prime * hashCodeCalculation + persister.hashCode();

			final int[] naturalIdPropertyIndexes = persister.getNaturalIdentifierProperties();
			naturalIdTypes = new Type[ naturalIdPropertyIndexes.length ];
			int i = 0;
			for ( int naturalIdPropertyIndex : naturalIdPropertyIndexes ) {
				final Type type = persister.getPropertyType( persister.getPropertyNames()[ naturalIdPropertyIndex ] );
				naturalIdTypes[i] = type;
				final int elementHashCode = values[i] == null ? 0 :type.getHashCode( values[i], persister.getFactory() );
				hashCodeCalculation = prime * hashCodeCalculation + elementHashCode;
				i++;
			}

			this.hashCode = hashCodeCalculation;
		}

		public Object[] getValues() {
			return values;
		}

		@Override
		public int hashCode() {
			return this.hashCode;
		}

		@Override
		public boolean equals(Object obj) {
			if ( this == obj ) {
				return true;
			}
			if ( obj == null ) {
				return false;
			}
			if ( getClass() != obj.getClass() ) {
				return false;
			}

			final CachedNaturalId other = (CachedNaturalId) obj;
			return persister.equals( other.persister ) && isSame( other.values );
		}

		private boolean isSame(Object[] otherValues) {
			// lengths have already been verified at this point
			for ( int i = 0; i < naturalIdTypes.length; i++ ) {
				if ( ! naturalIdTypes[i].isEqual( values[i], otherValues[i], persister.getFactory() ) ) {
					return false;
				}
			}
			return true;
		}
	}

	
Represents the persister-specific cross-reference cache.
/**
	 * Represents the persister-specific cross-reference cache.
	 */
	private static class NaturalIdResolutionCache implements Serializable {
		private final EntityPersister persister;
		private final Type[] naturalIdTypes;

		private Map<Serializable, CachedNaturalId> pkToNaturalIdMap = new ConcurrentHashMap<Serializable, CachedNaturalId>();
		private Map<CachedNaturalId, Serializable> naturalIdToPkMap = new ConcurrentHashMap<CachedNaturalId, Serializable>();

		private List<CachedNaturalId> invalidNaturalIdList;

		private NaturalIdResolutionCache(EntityPersister persister) {
			this.persister = persister;

			final int[] naturalIdPropertyIndexes = persister.getNaturalIdentifierProperties();
			naturalIdTypes = new Type[ naturalIdPropertyIndexes.length ];
			int i = 0;
			for ( int naturalIdPropertyIndex : naturalIdPropertyIndexes ) {
				naturalIdTypes[i++] = persister.getPropertyType( persister.getPropertyNames()[ naturalIdPropertyIndex ] );
			}
		}

		public EntityPersister getPersister() {
			return persister;
		}

		public boolean sameAsCached(Serializable pk, Object[] naturalIdValues) {
			if ( pk == null ) {
				return false;
			}
			final CachedNaturalId initial = pkToNaturalIdMap.get( pk );
			if ( initial != null ) {
				if ( initial.isSame( naturalIdValues ) ) {
					return true;
				}
			}
			return false;
		}

		public boolean cache(Serializable pk, Object[] naturalIdValues) {
			if ( pk == null ) {
				return false;
			}
			final CachedNaturalId initial = pkToNaturalIdMap.get( pk );
			if ( initial != null ) {
				if ( initial.isSame( naturalIdValues ) ) {
					return false;
				}
				naturalIdToPkMap.remove( initial );
			}

			final CachedNaturalId cachedNaturalId = new CachedNaturalId( persister, naturalIdValues );
			pkToNaturalIdMap.put( pk, cachedNaturalId );
			naturalIdToPkMap.put( cachedNaturalId, pk );
			
			return true;
		}

		public void stashInvalidNaturalIdReference(Object[] invalidNaturalIdValues) {
			if ( invalidNaturalIdList == null ) {
				invalidNaturalIdList = new ArrayList<CachedNaturalId>();
			}
			invalidNaturalIdList.add( new CachedNaturalId( persister, invalidNaturalIdValues ) );
		}

		public boolean containsInvalidNaturalIdReference(Object[] naturalIdValues) {
			return invalidNaturalIdList != null
					&& invalidNaturalIdList.contains( new CachedNaturalId( persister, naturalIdValues ) );
		}

		public void unStashInvalidNaturalIdReferences() {
			if ( invalidNaturalIdList != null ) {
				invalidNaturalIdList.clear();
			}
		}
	}

	
Clear the resolution cache
/**
	 * Clear the resolution cache
	 */
	public void clear() {
		naturalIdResolutionCacheMap.clear();
	}
}