/* 
 * Hibernate, Relational Persistence for Idiomatic Java
 * 
 * JBoss, Home of Professional Open Source
 * Copyright 2012 Red Hat Inc. and/or its affiliates and other contributors
 * as indicated by the @authors tag. All rights reserved.
 * See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * 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, v. 2.1.
 * This program is distributed in the hope that it will be useful, but WITHOUT A
 * 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,
 * v.2.1 along with this distribution; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA  02110-1301, USA.
 */
package org.hibernate.ogm.service.impl;

import java.util.Map;

import org.antlr.runtime.ANTLRStringStream;
import org.antlr.runtime.CommonTokenStream;
import org.antlr.runtime.RecognitionException;
import org.antlr.runtime.TokenStream;
import org.antlr.runtime.tree.CommonTree;
import org.antlr.runtime.tree.CommonTreeNodeStream;
import org.hibernate.HibernateException;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.search.FullTextQuery;
import org.hibernate.search.FullTextSession;
import org.hibernate.search.Search;
import org.hibernate.search.engine.spi.SearchFactoryImplementor;
import org.hibernate.search.query.DatabaseRetrievalMethod;
import org.hibernate.search.query.ObjectLookupMethod;
import org.hibernate.service.spi.ServiceRegistryImplementor;
import org.hibernate.sql.ast.origin.hql.parse.HQLLexer;
import org.hibernate.sql.ast.origin.hql.parse.HQLParser;
import org.hibernate.sql.ast.origin.hql.resolve.EntityNamesResolver;
import org.hibernate.sql.ast.origin.hql.resolve.LuceneJPQLWalker;


/**
 * QueryParserService using the ANTLR3-powered LuceneJPQLWalker.
 * Expects the targeted entities and used attributes to be indexed via Hibernate Search,
 * transforming HQL and JPQL in Lucene Queries.
 * 
 * @author Sanne Grinovero <sanne@hibernate.org> (C) 2012 Red Hat Inc.
 */
public class LuceneBasedQueryParserService implements QueryParserService {

	private final ServiceRegistryImplementor registry;
	private volatile SessionFactoryEntityNamesResolver entityNamesResolver;

	public LuceneBasedQueryParserService(ServiceRegistryImplementor registry, Map configurationValues) {
		this.registry = registry;
		//TODO: make it possible to lookup the SearchFactoryImplementor at initialization time
		//searchFactoryImplementor = lookupSearchFactory( registry );
	}

	@Override
	public Query getParsedQueryExecutor(Session session, String queryString, Map<String, Object> namedParameters) {
		HQLLexer lexed = new HQLLexer( new ANTLRStringStream( queryString ) );
		TokenStream tokens = new CommonTokenStream( lexed );
		HQLParser parser = new HQLParser( tokens );
		try {
			//TODO move the following logic into the hibernate-jpql-parser project?
			//needs to consider usage of a parsed query plans cache

			// parser#statement() is the entry point for evaluation of any kind of statement
			HQLParser.statement_return r = parser.statement();
			CommonTree tree = (CommonTree) r.getTree();
			// To walk the resulting tree we need a treenode stream:
			CommonTreeNodeStream treeStream = new CommonTreeNodeStream( tree );
			// AST nodes have payloads referring to the tokens from the Lexer:
			treeStream.setTokenStream( tokens );
			EntityNamesResolver entityNamesResolver = getDefinedEntityNames( session.getSessionFactory() );
			FullTextSession fullTextSession = Search.getFullTextSession( session );
			SearchFactoryImplementor searchFactory = (SearchFactoryImplementor) fullTextSession.getSearchFactory();
			// Finally create the treewalker:
			LuceneJPQLWalker walker = new LuceneJPQLWalker( treeStream, searchFactory, entityNamesResolver, namedParameters );
			walker.statement();
			org.apache.lucene.search.Query luceneQuery = walker.getLuceneQuery();
			Class targetEntity = walker.getTargetEntity();
			FullTextQuery fullTextQuery = fullTextSession.createFullTextQuery( luceneQuery, targetEntity );
			//Following options are mandatory to load matching entities without using a query
			//(chicken and egg problem)
			fullTextQuery.initializeObjectsWith( ObjectLookupMethod.SKIP, DatabaseRetrievalMethod.FIND_BY_ID );
			return fullTextQuery;
		}
		catch (RecognitionException e) {
			throw new HibernateException( "Invalid query syntax", e );
		}
	}

	private EntityNamesResolver getDefinedEntityNames(SessionFactory sessionFactory) {
		if ( entityNamesResolver == null ) {
			entityNamesResolver = new SessionFactoryEntityNamesResolver( sessionFactory );
		}
		return entityNamesResolver;
	}

}