EpplusFormulaParser/ExpressionGraph/Expression.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.Collections.Generic;
using System.Linq;

namespace EpplusFormulaParser;

public abstract class Expression {
  public string ExpressionString { get; private set; }

  private readonly List<Expression> _children;

  public IReadOnlyList<Expression> Children { get; }

  public Expression? Next { get; set; }

  public Expression? Prev { get; set; }

  public IOperator? Operator { get; set; }

  public abstract bool IsGroupedExpression { get; }

  protected Expression()
      : this("") {}

  protected Expression(string expression) {
    ExpressionString = expression;
    _children = [];
    Children = _children.AsReadOnly();
  }

  public virtual bool ParentIsLookupFunction { get; set; }

  public virtual bool HasChildren => _children.Count != 0;

  internal virtual Expression PrepareForNextChild() {
    return this;
  }

  public virtual Expression AddChild(Expression child) {
    if (_children.Count != 0) {
      var last = _children.Last();
      child.Prev = last;
      last.Next = child;
    }
    _children.Add(child);
    return child;
  }
}