﻿/* 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		                2013-12-03
 *******************************************************************************/

using System;
using System.Collections.Generic;

namespace AppsheetEpplus;

public class Floor : ExcelFunction {
  public override CompileResult Execute(
      IEnumerable<FunctionArgument> arguments,
      ParsingContext context) {
    ValidateArguments(arguments, 2);
    var number = ArgToDecimal(arguments, 0);
    var significance = ArgToDecimal(arguments, 1);
    ValidateNumberAndSign(number, significance);
    if (significance < 1 && significance > 0) {
      var floor = System.Math.Floor(number);
      var rest = number - floor;
      var nSign = (int)(rest / significance);
      return CreateResult(floor + (nSign * significance), DataType.Decimal);
    }
    if (significance == 1) {
      return CreateResult(System.Math.Floor(number), DataType.Decimal);
    }
    double result;
    if (number > 1) {
      result = number - (number % significance) + significance;
    } else {
      result = number - (number % significance);
    }
    return CreateResult(result, DataType.Decimal);
  }

  private void ValidateNumberAndSign(double number, double sign) {
    if (number > 0d && sign < 0) {
      var values = string.Format("num: {0}, sign: {1}", number, sign);
      throw new InvalidOperationException(
          "Floor cannot handle a negative significance when the number is positive" + values);
    }
  }
}