/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.proxy.pojo;

import java.io.Serializable;
import java.lang.reflect.Method;

import org.hibernate.engine.spi.EntityKey;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.internal.util.MarkerObject;
import org.hibernate.proxy.AbstractLazyInitializer;
import org.hibernate.type.CompositeType;

/**
 * Lazy initializer for POJOs
 *
 * @author Gavin King
 */
public abstract class BasicLazyInitializer extends AbstractLazyInitializer {

	protected static final Object INVOKE_IMPLEMENTATION = new MarkerObject( "INVOKE_IMPLEMENTATION" );

	protected final Class persistentClass;
	protected final Method getIdentifierMethod;
	protected final Method setIdentifierMethod;
	protected final boolean overridesEquals;
	protected final CompositeType componentIdType;

	private Object replacement;

	protected BasicLazyInitializer(
			String entityName,
			Class persistentClass,
			Serializable id,
			Method getIdentifierMethod,
			Method setIdentifierMethod,
			CompositeType componentIdType,
			SharedSessionContractImplementor session,
			boolean overridesEquals) {
		super( entityName, id, session );
		this.persistentClass = persistentClass;
		this.getIdentifierMethod = getIdentifierMethod;
		this.setIdentifierMethod = setIdentifierMethod;
		this.componentIdType = componentIdType;
		this.overridesEquals = overridesEquals;
	}

	protected abstract Object serializableProxy();

	protected final Object invoke(Method method, Object[] args, Object proxy) throws Throwable {
		String methodName = method.getName();
		int params = args.length;

		if ( params == 0 ) {
			if ( "writeReplace".equals( methodName ) ) {
				return getReplacement();
			}
			else if ( !overridesEquals && "hashCode".equals( methodName ) ) {
				return System.identityHashCode( proxy );
			}
			else if ( isUninitialized() && method.equals( getIdentifierMethod ) ) {
				return getIdentifier();
			}
			else if ( "getHibernateLazyInitializer".equals( methodName ) ) {
				return this;
			}
		}
		else if ( params == 1 ) {
			if ( !overridesEquals && "equals".equals( methodName ) ) {
				return args[0] == proxy;
			}
			else if ( method.equals( setIdentifierMethod ) ) {
				initialize();
				setIdentifier( (Serializable) args[0] );
				return INVOKE_IMPLEMENTATION;
			}
		}

		//if it is a property of an embedded component, invoke on the "identifier"
		if ( componentIdType != null && componentIdType.isMethodOf( method ) ) {
			return method.invoke( getIdentifier(), args );
		}

		// otherwise:
		return INVOKE_IMPLEMENTATION;

	}

	private Object getReplacement() {
		final SharedSessionContractImplementor session = getSession();
		if ( isUninitialized() && session != null && session.isOpen() ) {
			final EntityKey key = session.generateEntityKey(
					getIdentifier(),
					session.getFactory().getMetamodel().entityPersister( getEntityName() )
			);
			final Object entity = session.getPersistenceContext().getEntity( key );
			if ( entity != null ) {
				setImplementation( entity );
			}
		}

		if ( isUninitialized() ) {
			if ( replacement == null ) {
				replacement = serializableProxy();
			}
			return replacement;
		}
		else {
			return getTarget();
		}

	}

	public final Class getPersistentClass() {
		return persistentClass;
	}

}