﻿/* 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.Collections.Generic;
using System.Linq;

namespace AppsheetEpplus;

public class AverageIf : HiddenValuesHandlingFunction {
  private readonly NumericExpressionEvaluator _numericExpressionEvaluator;
  private readonly WildCardValueMatcher _wildCardValueMatcher;

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

  public AverageIf(
      NumericExpressionEvaluator evaluator,
      WildCardValueMatcher wildCardValueMatcher) {
    Require.That(evaluator).Named("evaluator").IsNotNull();
    Require.That(evaluator).Named("wildCardValueMatcher").IsNotNull();
    _numericExpressionEvaluator = evaluator;
    _wildCardValueMatcher = wildCardValueMatcher;
  }

  private bool Evaluate(object obj, string expression) {
    double? candidate = default(double?);
    if (IsNumeric(obj)) {
      candidate = ConvertUtil.GetValueDouble(obj);
    }
    if (candidate.HasValue) {
      return _numericExpressionEvaluator.Evaluate(candidate.Value, expression);
    }
    if (obj == null) {
      return false;
    }
    return _wildCardValueMatcher.IsMatch(expression, obj.ToString()) == 0;
  }

  public override CompileResult Execute(
      IEnumerable<FunctionArgument> arguments,
      ParsingContext context) {
    ValidateArguments(arguments, 2);
    var firstArg = arguments.ElementAt(0);
    var args = firstArg.Value as IEnumerable<FunctionArgument>;
    if (args == null && firstArg.IsExcelRange) {
      args = new List<FunctionArgument> { firstArg };
    }
    var criteria = arguments.ElementAt(1).Value;
    ThrowExcelErrorValueExceptionIf(
        () => criteria == null || criteria.ToString().Length > 255,
        eErrorType.Value);
    double retVal;
    if (arguments.Count() > 2) {
      var secondArg = arguments.ElementAt(2);
      var lookupRange = secondArg.Value as IEnumerable<FunctionArgument>;
      if (lookupRange == null && secondArg.IsExcelRange) {
        lookupRange = new List<FunctionArgument> { secondArg };
      }
      retVal = CalculateWithLookupRange(args, criteria.ToString(), lookupRange, context);
    } else {
      retVal = CalculateSingleRange(args, criteria.ToString(), context);
    }
    return CreateResult(retVal, DataType.Decimal);
  }

  private double CalculateWithLookupRange(
      IEnumerable<FunctionArgument> range,
      string criteria,
      IEnumerable<FunctionArgument> sumRange,
      ParsingContext context) {
    var retVal = 0d;
    var nMatches = 0;
    var flattenedRange = ArgsToObjectEnumerable(false, range, context);
    var flattenedSumRange = ArgsToDoubleEnumerable(sumRange, context);
    for (var x = 0; x < flattenedRange.Count(); x++) {
      var candidate = flattenedSumRange.ElementAt(x);
      if (Evaluate(flattenedRange.ElementAt(x), criteria)) {
        nMatches++;
        retVal += candidate;
      }
    }
    return Divide(retVal, nMatches);
  }

  private double CalculateSingleRange(
      IEnumerable<FunctionArgument> args,
      string expression,
      ParsingContext context) {
    var retVal = 0d;
    var nMatches = 0;
    var flattendedRange = ArgsToDoubleEnumerable(args, context);
    var candidates = flattendedRange as double[] ?? flattendedRange.ToArray();
    foreach (var candidate in candidates) {
      if (Evaluate(candidate, expression)) {
        retVal += candidate;
        nMatches++;
      }
    }
    return Divide(retVal, nMatches);
  }
}