using System;
using System.Linq;
using HEAL.Attic;
using HeuristicLab.Collections;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Optimization;
using HeuristicLab.Parameters;

namespace HeuristicLab.Problems.Modifiers {
  [StorableType("4C46E221-E7E6-41B4-8CFB-35920CDCE6E8")]
  [Creatable(CreatableAttribute.Categories.Problems, Priority = 90)]
  [Item("SingleObjectiveModifiedProblem", "A wrapper problem for single-objective problems that should be evaluated using Hive.")]
  public class SingleObjectiveModifiedProblem : SingleObjectiveBasicProblem<IEncoding>, IStatefulItem {

    private readonly SingleObjectiveEndPointProblemModifier<IEncoding> endPoint = new SingleObjectiveEndPointProblemModifier<IEncoding>();
    private ProblemModifier activeStart; //this is to avoid attaching to multiple modifiers
    public override bool Maximization => false; // this is a fixed and readonly parameter in BasicProblem, we cannot change it dynamically (after the constructor).

    #region Parameter Names
    private const string ProblemParameterName = "Problem";
    private const string ModifierParameterName = "Modifiers";
    #endregion

    #region Parameters
    public IValueParameter<SingleObjectiveBasicProblem<IEncoding>> ProblemParameter => (IValueParameter<SingleObjectiveBasicProblem<IEncoding>>)Parameters[ProblemParameterName];

    public IFixedValueParameter<CheckedItemList<ProblemModifier>> ModifierParameter => (IFixedValueParameter<CheckedItemList<ProblemModifier>>)Parameters[ModifierParameterName];
    #endregion

    #region Parameter Properties
    public SingleObjectiveBasicProblem<IEncoding> Problem {
      get => ProblemParameter.Value;
      set => ProblemParameter.Value = value;
    }

    public CheckedItemList<ProblemModifier> Modifiers => ModifierParameter.Value;

    #endregion

    #region Constructors & Cloning
    [StorableConstructor]
    protected SingleObjectiveModifiedProblem(StorableConstructorFlag _) : base(_) { }
    protected SingleObjectiveModifiedProblem(SingleObjectiveModifiedProblem original, Cloner cloner) : base(original, cloner) {
      Initialize();
    }
    public SingleObjectiveModifiedProblem() {
      var defaultModifiers = new CheckedItemList<ProblemModifier> {
        {new EvaluationCacheProblemModifier(), false},
        {new EvaluationRepetitionProblemModifier(), false},
        {new EvaluationLoggingProblemModifier(), false}
      };
      Parameters.Add(new ValueParameter<SingleObjectiveBasicProblem<IEncoding>>(ProblemParameterName, "The actual problem that should used to evaluate individuals."));
      Parameters.Add(new FixedValueParameter<CheckedItemList<ProblemModifier>>(ModifierParameterName, "The modifiers applied to the problem (order can be important)", defaultModifiers));
      Initialize();
    }

    public override IDeepCloneable Clone(Cloner cloner) {
      return new SingleObjectiveModifiedProblem(this, cloner);
    }
    #endregion

    [StorableHook(HookType.AfterDeserialization)]
    private void AfterDeserialization() {
      Initialize();
    }

    private void Initialize() {
      if (Problem != null) {
        Problem.OperatorsChanged -= Problem_OperatorsChanged;
        Problem.OperatorsChanged += Problem_OperatorsChanged;
      }
      ProblemParameter.ValueChanged -= ProblemParameter_ValueChanged;
      ProblemParameter.ValueChanged += ProblemParameter_ValueChanged;
      Modifiers.CheckedItemsChanged -= ActiveModifiersChanged;
      Modifiers.CheckedItemsChanged += ActiveModifiersChanged;
      Modifiers.ItemsMoved -= ActiveModifiersChanged; //This my fire unnecessarily but CheckedItemsChanged does not account for order ...
      Modifiers.ItemsMoved += ActiveModifiersChanged;
      UpdateModifiers();
    }

    public override double Evaluate(Individual individual, IRandom random) {
      // this must be a minimization problem. If the wrapped problem is a maximization problem then just return the negative quality.
      var wrappedQuality = activeStart.ModifiedEvaluate(individual, random)[0];
      return Problem.Maximization ? -wrappedQuality : wrappedQuality;
    }

    public override void Analyze(Individual[] individuals, double[] qualities, ResultCollection results, IRandom random) {
      activeStart.ModifiedAnalyze(individuals, qualities.Select(x => new[] { x }).ToArray(), results, random);
    }

    private bool updating;
    private void UpdateModifiers() {
      if (Problem == null || updating) return;
      updating = true;
      var am = Modifiers.CheckedItems.Select(x => x.Value).ToArray();

      //unwire modifiers to prevent cycles while setting and superfluous listeners
      foreach (var problemModifier in Modifiers) problemModifier.NextModifier = null;
      //wire modifiers
      for (var i = 0; i < am.Length - 1; i++) am[i].NextModifier = am[i + 1];
      if (am.Length != 0) am[am.Length - 1].NextModifier = endPoint;
      endPoint.Problem = Problem;

      //listen to activeStart changes
      if (activeStart != null) {
        activeStart.EncodingChanged -= StartEncodingChanged;
      }
      activeStart = am.Length == 0 ? endPoint : am[0];
      activeStart.EncodingChanged += StartEncodingChanged;

      foreach (var m in Modifiers) m.Initialize();

      updating = false;
      if (Encoding == activeStart.Encoding || activeStart.Encoding == null) return;
      Encoding = activeStart.Encoding;
    }


    private void StartEncodingChanged(object sender, EventArgs e) {
      if (Encoding == activeStart.Encoding || activeStart.Encoding == null) return;
      Encoding = activeStart.Encoding;
    }
    private void ActiveModifiersChanged(object sender, CollectionItemsChangedEventArgs<IndexedItem<ProblemModifier>> e) {
      UpdateModifiers();
    }

    private void ProblemParameter_ValueChanged(object sender, EventArgs e) {
      if (Problem != null) {
        Problem.OperatorsChanged -= Problem_OperatorsChanged;
        Problem.OperatorsChanged += Problem_OperatorsChanged;
      }
      endPoint.Problem = Problem;
      UpdateModifiers();
    }

    private void Problem_OperatorsChanged(object sender, EventArgs e) {
      UpdateModifiers();
    }


    void IStatefulItem.InitializeState() {
      UpdateModifiers();
    }

    void IStatefulItem.ClearState() {
      UpdateModifiers();
    }
  }
}