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;
    }
  }
}