EPPlus/FormulaParsing/LexicalAnalysis/TokenSeparatorHandlers/MultipleCharSeparatorHandler.cs

/*******************************************************************************
 * You may amend and distribute as you like, but don't remove this header!
 *
 * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
 * See http://www.codeplex.com/EPPlus for details.
 *
 * Copyright (C) 2011  Jan Källman
 *
 * 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.
 *
 * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
 * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
 *
 * All code and executables are provided "as is" with no warranty either express or implied. 
 * The author accepts no liability for any damage or loss of business that this product may cause.
 *
 * Code change notes:
 * 
 * Author							Change						Date
 * ******************************************************************************
 * Mats Alm   		                Added       		        2015-12-28
 *******************************************************************************/
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;

namespace OfficeOpenXml.FormulaParsing.LexicalAnalysis.TokenSeparatorHandlers
{
    public class MultipleCharSeparatorHandler : SeparatorHandler
    {
        ITokenSeparatorProvider _tokenSeparatorProvider;

        public MultipleCharSeparatorHandler()
            : this(new TokenSeparatorProvider())
        {

        }
        public MultipleCharSeparatorHandler(ITokenSeparatorProvider tokenSeparatorProvider)
        {
            _tokenSeparatorProvider = tokenSeparatorProvider;
        }
        public override bool Handle(char c, Token tokenSeparator, TokenizerContext context, ITokenIndexProvider tokenIndexProvider)
        {
            // two operators in sequence could be "<=" or ">="
            if (IsPartOfMultipleCharSeparator(context, c))
            {
                var sOp = context.LastToken.Value + c.ToString(CultureInfo.InvariantCulture);
                var op = _tokenSeparatorProvider.Tokens[sOp];
                context.ReplaceLastToken(op);
                context.NewToken();
                return true;
            }
            return false;
        }

        private bool IsPartOfMultipleCharSeparator(TokenizerContext context, char c)
        {
            var lastToken = context.LastToken != null ? context.LastToken.Value : string.Empty;
            return _tokenSeparatorProvider.IsOperator(lastToken)
                && _tokenSeparatorProvider.IsPossibleLastPartOfMultipleCharOperator(c.ToString(CultureInfo.InvariantCulture))
                && !context.CurrentTokenHasValue;
        }
    }
}