AppsheetEpplus/FormulaParsing/ExcelUtilities/NumericExpressionEvaluator.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       		        2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
 *******************************************************************************/

using System;
using System.Text.RegularExpressions;

namespace AppsheetEpplus;

public class NumericExpressionEvaluator {
  private readonly ValueMatcher _valueMatcher;
  private readonly CompileResultFactory _compileResultFactory;

  public NumericExpressionEvaluator()
      : this(new(), new()) {}

  public NumericExpressionEvaluator(
      ValueMatcher valueMatcher,
      CompileResultFactory compileResultFactory) {
    _valueMatcher = valueMatcher;
    _compileResultFactory = compileResultFactory;
  }

  private string GetNonNumericStartChars(string expression) {
    if (!string.IsNullOrEmpty(expression)) {
      if (Regex.IsMatch(expression, @"^([^\d]{2})")) {
        return expression.Substring(0, 2);
      }
      if (Regex.IsMatch(expression, @"^([^\d]{1})")) {
        return expression.Substring(0, 1);
      }
    }
    return null;
  }

  public double? OperandAsDouble(object op) {
    if (op is double || op is int) {
      return Convert.ToDouble(op);
    }
    if (op != null) {
      if (double.TryParse(op.ToString(), out var output)) {
        return output;
      }
    }
    return null;
  }

  public bool Evaluate(object left, string expression) {
    var operatorCandidate = GetNonNumericStartChars(expression);
    var leftNum = OperandAsDouble(left);
    if (!string.IsNullOrEmpty(operatorCandidate) && leftNum != null) {
      if (OperatorsDict.Instance.TryGetValue(operatorCandidate, out var op)) {
        var numericCandidate = expression.Replace(operatorCandidate, string.Empty);
        if (double.TryParse(numericCandidate, out var d)) {
          var leftResult = _compileResultFactory.Create(leftNum);
          var rightResult = _compileResultFactory.Create(d);
          var result = op.Apply(leftResult, rightResult);
          if (result.DataType != DataType.Boolean) {
            throw new ArgumentException("Illegal operator in expression");
          }
          return (bool)result.Result;
        }
      }
    }
    return _valueMatcher.IsMatch(left, expression) == 0;
  }
}