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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) 2014 Simon Chenery
 *
 *  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 SQLTrimFunction extends Expression
{
	public enum Type { LEADING, TRAILING, BOTH }

	Expression expression;
	Expression trimChars;
	Type trimType;

	public SQLTrimFunction(Expression expression, Expression trimChars, Type trimType)
	{
		this.expression = expression;
		this.trimChars = trimChars;
		this.trimType = trimType;
	}
	@Override
	public Object eval(Map env) throws SQLException
	{
		Object retval = expression.eval(env);
		if (retval != null)
		{
			String str = retval.toString();
			if (trimChars != null)
			{
				Object o = trimChars.eval(env);
				if (o != null)
				{
					String trim = o.toString();
					int startIndex = 0;
					if (trimType == Type.LEADING || trimType == Type.BOTH)
					{
						while (startIndex < str.length() && trim.indexOf(str.charAt(startIndex)) >= 0)
							startIndex++;
					}

					int endIndex = str.length() - 1;
					if (trimType == Type.TRAILING || trimType == Type.BOTH)
					{
						while (endIndex >= startIndex && trim.indexOf(str.charAt(endIndex)) >= 0)
							endIndex--;
					}

					if (endIndex >= startIndex)
						retval = str.substring(startIndex, endIndex + 1);
					else
						retval = "";
				}
				else
				{
					retval = null;
				}
			}
			else
			{
				/*
				 * Trim whitespace by default.
				 */
				if (trimType == Type.BOTH)
				{
					retval = str.trim();
				}
				else if (trimType == Type.LEADING)
				{
					int startIndex = 0;
					while (startIndex < str.length() && Character.isWhitespace(str.charAt(startIndex)))
						startIndex++;
					retval = str.substring(startIndex, str.length());
				}
				else // Type.TRAILING
				{
					int endIndex = str.length() - 1;
					while (endIndex >= 0 && Character.isWhitespace(str.charAt(endIndex)))
						endIndex--;
					retval = str.substring(0, endIndex + 1);
				}
			}
		}
		return retval;
	}
	@Override
	public String toString()
	{
		if (trimType == Type.LEADING)
			return "LTRIM("+expression+")";
		else if (trimType == Type.TRAILING)
			return "RTRIM("+expression+")";
		else
			return "TRIM("+expression+")";
	}
	@Override
	public List usedColumns(Set availableColumns)
	{
		List result = new LinkedList<>();
		result.addAll(expression.usedColumns(availableColumns));
		if (trimChars != null)
			result.addAll(trimChars.usedColumns(availableColumns));
		return result;
	}
	@Override
	public List aggregateFunctions()
	{
		List result = new LinkedList<>();
		result.addAll(expression.aggregateFunctions());
		if (trimChars != null)
			result.addAll(trimChars.aggregateFunctions());
		return result;
	}
}