AppsheetEpplus/FormulaParsing/ExcelUtilities/ExpressionEvaluator.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 ExpressionEvaluator {
  private readonly WildCardValueMatcher _wildCardValueMatcher;
  private readonly CompileResultFactory _compileResultFactory;

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

  public ExpressionEvaluator(
      WildCardValueMatcher wildCardValueMatcher,
      CompileResultFactory compileResultFactory) {
    _wildCardValueMatcher = wildCardValueMatcher;
    _compileResultFactory = compileResultFactory;
  }

  private string GetNonAlphanumericStartChars(string expression) {
    if (!string.IsNullOrEmpty(expression)) {
      if (Regex.IsMatch(expression, "^([^a-zA-Z0-9]{2})")) {
        return expression.Substring(0, 2);
      }
      if (Regex.IsMatch(expression, "^([^a-zA-Z0-9]{1})")) {
        return expression.Substring(0, 1);
      }
    }
    return null;
  }

  private bool EvaluateOperator(object left, object right, IOperator op) {
    var leftResult = _compileResultFactory.Create(left);
    var rightResult = _compileResultFactory.Create(right);
    var result = op.Apply(leftResult, rightResult);
    if (result.DataType != DataType.Boolean) {
      throw new ArgumentException("Illegal operator in expression");
    }
    return (bool)result.Result;
  }

  public bool TryConvertToDouble(object op, out double d) {
    if (op is double || op is int) {
      d = Convert.ToDouble(op);
      return true;
    }
    if (op is DateTime time) {
      d = time.ToOADate();
      return true;
    }
    if (op != null) {
      if (double.TryParse(op.ToString(), out d)) {
        return true;
      }
    }
    d = 0;
    return false;
  }

  public bool Evaluate(object left, string expression) {
    if (expression == string.Empty) {
      return left == null;
    }
    var operatorCandidate = GetNonAlphanumericStartChars(expression);
    if (!string.IsNullOrEmpty(operatorCandidate) && operatorCandidate != "-") {
      if (OperatorsDict.Instance.TryGetValue(operatorCandidate, out var op)) {
        var right = expression.Replace(operatorCandidate, string.Empty);
        if (left == null && right == string.Empty) {
          return op.Operator == Operators.Equals;
        }
        if (left == null ^ right == string.Empty) {
          return op.Operator == Operators.NotEqualTo;
        }
        bool leftIsNumeric = TryConvertToDouble(left, out var leftNum);
        bool rightIsNumeric = double.TryParse(right, out var rightNum);
        bool rightIsDate = DateTime.TryParse(right, out var date);
        if (leftIsNumeric && rightIsNumeric) {
          return EvaluateOperator(leftNum, rightNum, op);
        }
        if (leftIsNumeric && rightIsDate) {
          return EvaluateOperator(leftNum, date.ToOADate(), op);
        }
        if (leftIsNumeric != rightIsNumeric) {
          return op.Operator == Operators.NotEqualTo;
        }
        return EvaluateOperator(left, right, op);
      }
    }
    return _wildCardValueMatcher.IsMatch(expression, left) == 0;
  }
}