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a Java JDBC driver for reading comma-separated-value files

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/*
 *  CsvJdbc - a JDBC driver for CSV files
 *  Copyright (C) 2008  Mario Frasca
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library 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 library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package org.relique.jdbc.csv;

import java.sql.SQLException;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

class LikeExpression extends LogicalExpression
{
	Expression arg1, arg2;
	Expression escapeArg;
	public LikeExpression(Expression arg1, Expression arg2, Expression escapeArg)
	{
		this.arg1 = arg1;
		this.arg2 = arg2;
		this.escapeArg = escapeArg;
	}
	@Override
	public Boolean isTrue(Map env) throws SQLException
	{
		Object left = arg1.eval(env);
		Object right = arg2.eval(env);
		String escape = LikePattern.DEFAULT_ESCAPE_STRING;
		
		if (escapeArg != null)
		{
			escape = "";
			Object o = escapeArg.eval(env);
			if (o != null)
			{
				String s = o.toString();
				if (s.length() > 0)
					escape = s.substring(0, 1);
			}	
		}

		Boolean result = null;
		if (left != null && right != null)
			result = Boolean.valueOf(LikePattern.matches(right.toString(), escape, left.toString()));
		return result;
	}
	@Override
	public String toString()
	{
		StringBuilder sb = new StringBuilder();
		sb.append("L ");
		sb.append(arg1);
		sb.append(" ");
		sb.append(arg2);
		if (escapeArg != null)
		{
			sb.append(" ESCAPE ");
			sb.append(escapeArg);
		}
		return sb.toString();
	}
	@Override
	public List usedColumns(Set availableColumns)
	{
		List result = new LinkedList<>();
		result.addAll(arg1.usedColumns(availableColumns));
		result.addAll(arg2.usedColumns(availableColumns));
		if (escapeArg != null)
			result.addAll(escapeArg.usedColumns(availableColumns));
		return result;
	}
	@Override
	public List aggregateFunctions()
	{
		List result = new LinkedList<>();
		result.addAll(arg1.aggregateFunctions());
		result.addAll(arg2.aggregateFunctions());
		if (escapeArg != null)
			result.addAll(escapeArg.aggregateFunctions());
		return result;
	}
}