#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2017 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;
using System.Runtime.Remoting.Contexts;
using System.Threading;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Data;
using HeuristicLab.Encodings.PermutationEncoding;
using HeuristicLab.Optimization;
using HeuristicLab.Optimization.Operators;
using HeuristicLab.Parameters;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;

namespace HeuristicLab.Problems.TravelingSalesman {
  [Item("InversionPathRelinker", "An operator that relinks solutions.")]
  [StorableClass]
  public sealed class InversionPathRelinker : SingleObjectivePathRelinker, IStochasticOperator {
    public IValueLookupParameter<DoubleMatrix> DistanceMatrixParameter {
      get { return (IValueLookupParameter<DoubleMatrix>)Parameters["DistanceMatrix"]; }
    }

    public ILookupParameter<IRandom> RandomParameter {
      get { return (ILookupParameter<IRandom>) Parameters["Random"]; }
    }
    [StorableConstructor]
    private InversionPathRelinker(bool deserializing) : base(deserializing) { }
    private InversionPathRelinker(InversionPathRelinker original, Cloner cloner) : base(original, cloner) { }

    public InversionPathRelinker() : base() {
      Parameters.Add(new ValueLookupParameter<DoubleMatrix>("DistanceMatrix"));
      Parameters.Add(new LookupParameter<IRandom>("Random"));
    }

    public override IDeepCloneable Clone(Cloner cloner) {
      return new InversionPathRelinker(this, cloner);
    }

    protected override ItemArray<IItem> Relink(ItemArray<IItem> parents, PercentValue n) {
      if (parents.Length != 2)
        throw new ArgumentException("The number of parents is not equal to 2.");
      var random = RandomParameter.ActualValue;
      var distances = DistanceMatrixParameter.ActualValue;
      Func<Permutation, double> eval = (p) => {
        double length = 0;
        for (int i = 0; i < p.Length - 1; i++)
          length += distances[p[i], p[i + 1]];
        length += distances[p[p.Length - 1], p[0]];
        return length;
      };
      return new ItemArray<IItem>(RelinkOpt(random, (Permutation)parents[0],
        (Permutation)parents[1], eval));
    }

    public IEnumerable<Permutation> RelinkOpt(IRandom random, Permutation p1, Permutation p2,
                               Func<Permutation, double> eval) {

      var evaluations = 0;
      var child = (Permutation)p1.Clone();
      
      Permutation bestChild = null;

      var invChild = new int[child.Length];
      var invP2 = new int[child.Length];
      for (var i = 0; i < child.Length; i++) {
        invChild[child[i]] = i;
        invP2[p2[i]] = i;
      }

      var bestChange = double.NaN;
      var moveQueue = new Queue<Tuple<int, int>>();
      var undoStack = new Stack<Tuple<int, int>>();
      do {
        Queue<Tuple<int, int>> bestQueue = null;
        bestChange = double.NaN;
        for (var j = 0; j < p2.Length; j++) {
          if (IsUndirectedEdge(invChild, p2[j], p2.GetCircular(j + 1))) continue;

          var a = invChild[p2[j]];
          var b = invChild[p2.GetCircular(j + 1)];
          if (a > b) { var h = a; a = b; b = h; }
          var aprev = a - 1;
          var bprev = b - 1;
          while (IsUndirectedEdge(invP2, child.GetCircular(aprev), child.GetCircular(aprev + 1))) {
            aprev--;
          }
          while (IsUndirectedEdge(invP2, child.GetCircular(bprev), child.GetCircular(bprev + 1))) {
            bprev--;
          }
          var bnext = b + 1;
          var anext = a + 1;
          while (IsUndirectedEdge(invP2, child.GetCircular(bnext - 1), child.GetCircular(bnext))) {
            bnext++;
          }
          while (IsUndirectedEdge(invP2, child.GetCircular(anext - 1), child.GetCircular(anext))) {
            anext++;
          }
          aprev++; bprev++; anext--; bnext--;

          if (aprev < a && bnext > b) {
            if (aprev < 0) {
              moveQueue.Enqueue(Tuple.Create(a + 1, bnext));
              moveQueue.Enqueue(Tuple.Create(a + 1, a + 1 + (bnext - b)));
            } else {
              moveQueue.Enqueue(Tuple.Create(aprev, b - 1));
              moveQueue.Enqueue(Tuple.Create(b - 1 - (a - aprev), b - 1));
            }
          } else if (aprev < a && bnext == b && bprev == b) {
            moveQueue.Enqueue(Tuple.Create(a + 1, b));
          } else if (aprev < a && bprev < b) {
            moveQueue.Enqueue(Tuple.Create(a + 1, b));
          } else if (aprev == a && anext == a && bnext > b) {
            moveQueue.Enqueue(Tuple.Create(a, b - 1));
          } else if (aprev == a && anext == a && bnext == b && bprev == b) {
            moveQueue.Enqueue(Tuple.Create(a, b - 1));
          } else if (aprev == a && anext == a && bprev < b) {
            moveQueue.Enqueue(Tuple.Create(a + 1, b));
          } else if (anext > a && bnext > b) {
            moveQueue.Enqueue(Tuple.Create(a, b - 1));
          } else if (anext > a && bnext == b && bprev == b) {
            moveQueue.Enqueue(Tuple.Create(a, b - 1));
          } else /*if (anext > a && bprev < b)*/ {
            moveQueue.Enqueue(Tuple.Create(a, bprev - 1));
            moveQueue.Enqueue(Tuple.Create(bprev, b));
          }

          while (moveQueue.Count > 0) {
            var m = moveQueue.Dequeue();
            Opt(child, m.Item1, m.Item2);
            undoStack.Push(m);
          }
          var moveF = eval(child);

          evaluations++;
          if (double.IsNaN(bestChange) || moveF < bestChange) {
            bestChange = moveF;
            bestQueue = new Queue<Tuple<int, int>>(undoStack.Reverse());
          }
          // undo
          while (undoStack.Count > 0) {
            var m = undoStack.Pop();
            Opt(child, m.Item1, m.Item2);
          }
        }
        if (!double.IsNaN(bestChange)) {
          while (bestQueue.Count > 0) {
            var m = bestQueue.Dequeue();
            Opt(child, m.Item1, m.Item2);
            for (var i = m.Item1; i <= m.Item2; i++) invChild[child[i]] = i;
          }
          yield return (Permutation) child.Clone();
        }
      } while (!double.IsNaN(bestChange));
    }

    private static bool IsUndirectedEdge(int[] invP, int a, int b) {
      var d = Math.Abs(invP[a] - invP[b]);
      return d == 1 || d == invP.Length - 1;
    }

    private static void Opt(Permutation child, int from, int to) {
      if (from > to) child.Reverse(to, from - to + 1);
      else child.Reverse(from, to - from + 1);
    }
  }
}