/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008-2011, 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.bytecode.instrumentation.internal;

import java.util.HashSet;
import java.util.Set;

import org.hibernate.bytecode.instrumentation.internal.javassist.JavassistHelper;
import org.hibernate.bytecode.instrumentation.spi.FieldInterceptor;
import org.hibernate.engine.spi.SessionImplementor;

Helper class for dealing with enhanced entity classes. These operations are expensive. They are only meant to be used when code does not have access to a SessionFactory (namely from the instrumentation tasks). When code has access to a SessionFactory, EntityInstrumentationMetadata should be used instead to query the instrumentation state. EntityInstrumentationMetadata is accessed from the EntityPersister via the EntityPersister.getInstrumentationMetadata() method. 
Author:
Steve Ebersole/**
 * Helper class for dealing with enhanced entity classes.
 *
 * These operations are expensive.  They are only meant to be used when code does not have access to a
 * SessionFactory (namely from the instrumentation tasks).  When code has access to a SessionFactory,
 * {@link org.hibernate.bytecode.spi.EntityInstrumentationMetadata} should be used instead to query the
 * instrumentation state.  EntityInstrumentationMetadata is accessed from the
 * {@link org.hibernate.persister.entity.EntityPersister} via the
 * {@link org.hibernate.persister.entity.EntityPersister#getInstrumentationMetadata()} method.
 *
 * @author Steve Ebersole
 */
public class FieldInterceptionHelper {
	private static final Set<Delegate> INSTRUMENTATION_DELEGATES = buildInstrumentationDelegates();

	private static Set<Delegate> buildInstrumentationDelegates() {
		final HashSet<Delegate> delegates = new HashSet<Delegate>();
		delegates.add( JavassistDelegate.INSTANCE );
		return delegates;
	}

	
Utility to check to see if a given entity class is instrumented.
Params:
entityClass – The entity class to check
Returns:
true if it has been instrumented; false otherwise/**
	 * Utility to check to see if a given entity class is instrumented.
	 *
	 * @param entityClass The entity class to check
	 *
	 * @return {@code true} if it has been instrumented; {@code false} otherwise
	 */
	public static boolean isInstrumented(Class entityClass) {
		for ( Delegate delegate : INSTRUMENTATION_DELEGATES ) {
			if ( delegate.isInstrumented( entityClass ) ) {
				return true;
			}
		}
		return false;
	}

	
Utility to check to see if a given object is an instance of an instrumented class. If the instance is null, the check returns false 
Params:
object – The object to check
Returns:
true if it has been instrumented; false otherwise/**
	 * Utility to check to see if a given object is an instance of an instrumented class.  If the instance
	 * is {@code null}, the check returns {@code false}
	 *
	 * @param object The object to check
	 *
	 * @return {@code true} if it has been instrumented; {@code false} otherwise
	 */
	public static boolean isInstrumented(Object object) {
		return object != null && isInstrumented( object.getClass() );
	}

	
Assuming the given object is an enhanced entity, extract and return its interceptor. Will return null if object is null, or if the object was deemed to not be instrumented 
Params:
object – The object from which to extract the interceptor
Returns:
The extracted interceptor, or null/**
	 * Assuming the given object is an enhanced entity, extract and return its interceptor.  Will
	 * return {@code null} if object is {@code null}, or if the object was deemed to not be
	 * instrumented
	 *
	 * @param object The object from which to extract the interceptor
	 *
	 * @return The extracted interceptor, or {@code null}
	 */
	public static FieldInterceptor extractFieldInterceptor(Object object) {
		if ( object == null ) {
			return null;
		}
		FieldInterceptor interceptor = null;
		for ( Delegate delegate : INSTRUMENTATION_DELEGATES ) {
			interceptor = delegate.extractInterceptor( object );
			if ( interceptor != null ) {
				break;
			}
		}
		return interceptor;
	}

	
Assuming the given object is an enhanced entity, inject a field interceptor.
Params:
entity – The entity instance
entityName – The entity name
uninitializedFieldNames – The names of any uninitialized fields
session – The session
Returns:
The injected interceptor/**
	 * Assuming the given object is an enhanced entity, inject a field interceptor.
	 *
	 * @param entity The entity instance
	 * @param entityName The entity name
	 * @param uninitializedFieldNames The names of any uninitialized fields
	 * @param session The session
	 *
	 * @return The injected interceptor
	 */
	public static FieldInterceptor injectFieldInterceptor(
			Object entity,
			String entityName,
			Set uninitializedFieldNames,
			SessionImplementor session) {
		if ( entity == null ) {
			return null;
		}
		FieldInterceptor interceptor = null;
		for ( Delegate delegate : INSTRUMENTATION_DELEGATES ) {
			interceptor = delegate.injectInterceptor( entity, entityName, uninitializedFieldNames, session );
			if ( interceptor != null ) {
				break;
			}
		}
		return interceptor;
	}

	private static interface Delegate {
		public boolean isInstrumented(Class classToCheck);
		public FieldInterceptor extractInterceptor(Object entity);
		public FieldInterceptor injectInterceptor(Object entity, String entityName, Set uninitializedFieldNames, SessionImplementor session);
	}

	private static class JavassistDelegate implements Delegate {
		public static final JavassistDelegate INSTANCE = new JavassistDelegate();
		public static final String MARKER = "org.hibernate.bytecode.internal.javassist.FieldHandled";

		@Override
		public boolean isInstrumented(Class classToCheck) {
			for ( Class definedInterface : classToCheck.getInterfaces() ) {
				if ( MARKER.equals( definedInterface.getName() ) ) {
					return true;
				}
			}
			return false;
		}

		@Override
		public FieldInterceptor extractInterceptor(Object entity) {
			for ( Class definedInterface : entity.getClass().getInterfaces() ) {
				if ( MARKER.equals( definedInterface.getName() ) ) {
					return JavassistHelper.extractFieldInterceptor( entity );
				}
			}
			return null;
		}

		@Override
		public FieldInterceptor injectInterceptor(
				Object entity,
				String entityName,
				Set uninitializedFieldNames,
				SessionImplementor session) {
			for ( Class definedInterface : entity.getClass().getInterfaces() ) {
				if ( MARKER.equals( definedInterface.getName() ) ) {
					return JavassistHelper.injectFieldInterceptor( entity, entityName, uninitializedFieldNames, session );
				}
			}
			return null;
		}
	}

	private FieldInterceptionHelper() {
	}

}