#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2012 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Linq;

namespace HeuristicLab.Analysis.AlgorithmBehavior.Analyzers {
  /// <summary>
  /// Compares the quality against that of its parents.
  /// This is more or less the same code as in the WeightedParentsQualityComparator operator, but without the operator part
  /// </summary>
  public static class WeightedParentsQualityComparer {
    public static bool Compare(double leftQuality, double rightQuality1, double rightQuality2, double compFact, bool maximization) {
      return Compare(leftQuality, new double[] { rightQuality1, rightQuality2 }, compFact, maximization);
    }

    public static bool Compare(double leftQuality, IList<double> rightQualities, double compFact, bool maximization) {
      if (rightQualities.Count < 1) throw new InvalidOperationException("No rightQualities found. ");

      double threshold = 0;

      if (rightQualities.Count == 2) { // this case will probably be used most often
        double minQuality = Math.Min(rightQualities[0], rightQualities[1]);
        double maxQuality = Math.Max(rightQualities[0], rightQualities[1]);
        if (maximization)
          threshold = minQuality + (maxQuality - minQuality) * compFact;
        else
          threshold = maxQuality - (maxQuality - minQuality) * compFact;
      } else if (rightQualities.Count == 1) { // case for just one parent
        threshold = rightQualities[0];
      } else { // general case extended to 3 or more parents
        List<double> sortedQualities = rightQualities.ToList();
        sortedQualities.Sort();
        double minimumQuality = sortedQualities.First();

        double integral = 0;
        for (int i = 0; i < sortedQualities.Count - 1; i++) {
          integral += (sortedQualities[i] + sortedQualities[i + 1]) / 2.0; // sum of the trapezoid
        }
        integral -= minimumQuality * sortedQualities.Count;
        if (integral == 0) threshold = sortedQualities[0]; // all qualities are equal
        else {
          double selectedArea = integral * (maximization ? compFact : (1 - compFact));
          integral = 0;
          for (int i = 0; i < sortedQualities.Count - 1; i++) {
            double currentSliceArea = (sortedQualities[i] + sortedQualities[i + 1]) / 2.0;
            double windowedSliceArea = currentSliceArea - minimumQuality;
            if (windowedSliceArea == 0) continue;
            integral += windowedSliceArea;
            if (integral >= selectedArea) {
              double factor = 1 - ((integral - selectedArea) / (windowedSliceArea));
              threshold = sortedQualities[i] + (sortedQualities[i + 1] - sortedQualities[i]) * factor;
              break;
            }
          }
        }
      }

      bool result = maximization && leftQuality > threshold || !maximization && leftQuality < threshold;
      return result;
    }
  }
}