#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2011 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 HeuristicLab.PluginInfrastructure;

namespace HeuristicLab.Encodings.PermutationEncoding {
  [NonDiscoverableType]
  public class PermutationEqualityComparer : IEqualityComparer<Permutation> {
    public bool Equals(Permutation x, Permutation y) {
      if (x.PermutationType != y.PermutationType) return false;
      if (x.Length != y.Length) return false;
      switch (x.PermutationType) {
        case PermutationTypes.Absolute:
          return EqualsAbsolute(x, y);
        case PermutationTypes.RelativeDirected:
          return EqualsRelative(x, y, true);
        case PermutationTypes.RelativeUndirected:
          return EqualsRelative(x, y, false);
        default:
          throw new InvalidOperationException("unknown permutation type");
      }
    }

    private bool EqualsAbsolute(Permutation x, Permutation y) {
      for (int i = 0; i < x.Length; i++)
        if (x[i] != y[i]) return false;
      return true;
    }

    private bool EqualsRelative(Permutation x, Permutation y, bool directed) {
      int[] edgesX = CalculateEdgesVector(x);
      int[] edgesY = CalculateEdgesVector(y);
      for (int i = 0; i < x.Length; i++)
        if ((edgesX[i] != edgesY[i]) && (directed || edgesX[edgesY[i]] != i))
          return false;
      return true;
    }

    private int[] CalculateEdgesVector(Permutation permutation) {
      // transform path representation into adjacency representation
      int[] edgesVector = new int[permutation.Length];
      for (int i = 0; i < permutation.Length - 1; i++)
        edgesVector[permutation[i]] = permutation[i + 1];
      edgesVector[permutation[permutation.Length - 1]] = permutation[0];
      return edgesVector;
    }

    public int GetHashCode(Permutation obj) {
      if (obj == null) return 0;
      return obj.GetHashCode();
    }
  }
}