#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;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Data;
using HeuristicLab.Operators;
using HeuristicLab.Parameters;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;

namespace HeuristicLab.Algorithms.ScatterSearch {
  /// <summary>
  /// An operator that updates the solution pool.
  /// </summary>
  [Item("SolutionPoolUpdateMethod", "An operator that updates the solution pool.")]
  [StorableClass]
  public sealed class SolutionPoolUpdateMethod : SingleSuccessorOperator, IScatterSearchTargetProcessor {
    #region Parameter properties
    public ScopeParameter CurrentScopeParameter {
      get { return (ScopeParameter)Parameters["CurrentScope"]; }
    }
    public IValueLookupParameter<BoolValue> MaximizationParameter {
      get { return (IValueLookupParameter<BoolValue>)Parameters["Maximization"]; }
    }
    public IValueLookupParameter<BoolValue> NewSolutionsParameter {
      get { return (IValueLookupParameter<BoolValue>)Parameters["NewSolutions"]; }
    }
    public IValueLookupParameter<IntValue> ReferenceSetSizeParameter {
      get { return (IValueLookupParameter<IntValue>)Parameters["ReferenceSetSize"]; }
    }
    public IValueLookupParameter<IItem> QualityParameter {
      get { return (IValueLookupParameter<IItem>)Parameters["Quality"]; }
    }
    public IValueLookupParameter<IItem> TargetParameter {
      get { return (IValueLookupParameter<IItem>)Parameters["Target"]; }
    }
    #endregion

    #region Properties
    private IScope CurrentScope {
      get { return CurrentScopeParameter.ActualValue; }
    }
    private BoolValue Maximization {
      get { return MaximizationParameter.ActualValue; }
      set { MaximizationParameter.ActualValue = value; }
    }
    private BoolValue NewSolutions {
      get { return NewSolutionsParameter.ActualValue; }
    }
    private IntValue ReferenceSetSize {
      get { return ReferenceSetSizeParameter.ActualValue; }
      set { ReferenceSetSizeParameter.ActualValue = value; }
    }
    private IItem Quality {
      get { return QualityParameter.ActualValue; }
    }
    private IItem Target {
      get { return TargetParameter.ActualValue; }
    }
    #endregion

    [StorableConstructor]
    private SolutionPoolUpdateMethod(bool deserializing) : base(deserializing) { }
    private SolutionPoolUpdateMethod(SolutionPoolUpdateMethod original, Cloner cloner) : base(original, cloner) { }
    public SolutionPoolUpdateMethod() : base() { Initialize(); }

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

    private void Initialize() {
      #region Create parameters
      Parameters.Add(new ScopeParameter("CurrentScope"));
      Parameters.Add(new ValueLookupParameter<BoolValue>("Maximization"));
      Parameters.Add(new ValueLookupParameter<BoolValue>("NewSolutions"));
      Parameters.Add(new ValueLookupParameter<IntValue>("ReferenceSetSize"));
      Parameters.Add(new ValueLookupParameter<IItem>("Quality"));
      Parameters.Add(new ValueLookupParameter<IItem>("Target"));
      #endregion
      TargetParameter.ActualName = "KnapsackSolution"; // temporary solution for the knapsack problem
    }

    public override IOperation Apply() {
      var parentsScope = new Scope("Parents");
      var offspringScope = new Scope("Offspring");

      // split parents and offspring
      foreach (var scope in CurrentScope.SubScopes) {
        parentsScope.SubScopes.AddRange(scope.SubScopes.Take(scope.SubScopes.Count - 1));
        offspringScope.SubScopes.AddRange(scope.SubScopes.Last().SubScopes);
      }

      CurrentScope.SubScopes.Clear();

      var orderedParents = Maximization.Value ? parentsScope.SubScopes.OrderByDescending(x => x.Variables[QualityParameter.ActualName].Value) :
                                                parentsScope.SubScopes.OrderBy(x => x.Variables[QualityParameter.ActualName].Value);
      var orderedOffspring = Maximization.Value ? offspringScope.SubScopes.OrderByDescending(x => x.Variables[QualityParameter.ActualName].Value) :
                                                  offspringScope.SubScopes.OrderBy(x => x.Variables[QualityParameter.ActualName].Value);

      CurrentScope.SubScopes.AddRange(orderedParents);

      var worstParentQuality = (orderedParents.Last().Variables[QualityParameter.ActualName].Value as DoubleValue).Value;

      var Constraint = Maximization.Value ? (Func<IScope, bool>)(x => { return (x.Variables[QualityParameter.ActualName].Value as DoubleValue).Value > worstParentQuality; }) :
                                            (Func<IScope, bool>)(x => { return (x.Variables[QualityParameter.ActualName].Value as DoubleValue).Value < worstParentQuality; });

      // is there any offspring better than the worst parent?
      if (orderedOffspring.Any(Constraint)) {
        // produce the set union
        // attention: distinction might cause a too small reference set! (e.g. reference set = {1, 2, 2, 2, ..., 2} -> union = {1, 2}
        var union = orderedParents.Union(orderedOffspring.Where(Constraint), new KeyEqualityComparer<IScope>(x => x.Variables[TargetParameter.ActualName].Value.ToString()));
        if (union.Count() > orderedParents./*Distinct(new KeyEqualityComparer<IScope>(x => x.Variables[TargetParameter.ActualName].Value.ToString())).*/Count()) {
          var orderedUnion = Maximization.Value ? union.OrderByDescending(x => x.Variables[QualityParameter.ActualName].Value) :
                                                  union.OrderBy(x => x.Variables[QualityParameter.ActualName].Value);
          CurrentScope.SubScopes.Replace(orderedUnion.Take(ReferenceSetSize.Value).ToList());
          NewSolutions.Value = true;
        }
      }

      return base.Apply();
    }

    private class KeyEqualityComparer<T> : IEqualityComparer<T> {
      private readonly Func<T, object> keyExtractor;

      public KeyEqualityComparer(Func<T, object> keyExtractor) {
        this.keyExtractor = keyExtractor;
      }

      public bool Equals(T x, T y) {
        return keyExtractor(x).Equals(keyExtractor(y));
      }

      public int GetHashCode(T obj) {
        return keyExtractor(obj).GetHashCode();
      }
    }
  }
}