/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2010, 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 jef.database.query.function;

import java.util.List;

import jef.database.jsqlparser.expression.Function;
import jef.database.jsqlparser.expression.LongValue;
import jef.database.jsqlparser.expression.Parenthesis;
import jef.database.jsqlparser.expression.operators.arithmetic.Addition;
import jef.database.jsqlparser.expression.operators.arithmetic.Subtraction;
import jef.database.jsqlparser.visitor.Expression;

/**
 * Emulation of <tt>locate()</tt> on PostgreSQL
 * @author Jiyi
 */
public class EmuLocateOnPostgres extends BaseArgumentSqlFunction{

	public String getName() {
		return "locate";
	}

	/**
	 *  模拟啊
	 */
	public Expression renderExpression(List<Expression> args){
		boolean threeArgs = args.size() > 2;
		Expression pattern = args.get(0);			//要查找的字串
		Expression string = args.get(1);			//被查找的字串
		Expression start = threeArgs ? args.get(2) : null;	//偏移

		
		Expression right=string;
		if(threeArgs){
			right=new Function("substring",string,start);
		}
		Function func=new Function("position",pattern,right);
		func.getParameters().setBetween(" in ");
		if(threeArgs){
			Addition add=new Addition(func,start);
			Subtraction sub=new Subtraction(add,new LongValue(1));
			return new Parenthesis(sub);
		}else{
			return func;
		}
	}


}