using System;
using System.Collections;
using System.Collections.Generic;
using HeuristicLab.Core;

namespace HeuristicLab.Problems.MetaOptimization {
  public class ParameterCombinationsEnumerator : IEnumerator<IOptimizable> {
    private IOptimizable node;
    private List<IEnumerator> enumerators;
    private EnumeratorCollectionEnumerator<IItem> valueEnumerator;
    private bool initialized = false;

    public ParameterCombinationsEnumerator(IOptimizable node) {
      this.node = node;
      this.enumerators = new List<IEnumerator>();
    }

    public IOptimizable Current {
      get { return node; }
    }
    object IEnumerator.Current {
      get {
        if (!initialized)
          throw new InvalidOperationException("Enumeration not started. Call MoveNext!");
        return Current;
      }
    }

    public void Dispose() { }

    public bool MoveNext() {
      if (!initialized) {
        foreach (var enu in enumerators) {
          enu.Reset();
          if (!enu.MoveNext())
            return false;
        }
        initialized = true;
      } else {
        int i = 0;
        bool ok = false;
        while (!ok && i < enumerators.Count) {
          if (enumerators[i].MoveNext()) {
            ok = true;
          } else {
            i++;
          }
        }

        if (ok) {
          for (int k = i - 1; k >= 0; k--) {
            enumerators[k].Reset();
            enumerators[k].MoveNext();
          }
        } else {
          return false;
        }
      }

      var pc = node as IParameterConfiguration;
      if (pc != null && valueEnumerator != null) {
        pc.ActualValue = ((IValueConfiguration)valueEnumerator.Current).ActualValue;
        pc.UpdateActualValueIndexToItem((IValueConfiguration)valueEnumerator.Current);
      }
      var vc = node as IValueConfiguration;
      if (vc != null && valueEnumerator != null) {
        vc.ActualValue.Value = (IItem)valueEnumerator.Current;
      }
      return true;
    }

    public void Reset() {
      enumerators.Clear();
      valueEnumerator = null;
      initialized = false;

      var pc = node as IParameterConfiguration;
      if (pc != null) {
        valueEnumerator = new EnumeratorCollectionEnumerator<IItem>();

        foreach (var valueConfiguration in pc.ValueConfigurations.CheckedItems) {
          if (valueConfiguration.Value.Optimize) {
            var enumerator = new ParameterCombinationsEnumerator(valueConfiguration.Value);
            enumerator.Reset();
            valueEnumerator.AddEnumerator(enumerator);
          } else {
            valueEnumerator.AddEnumerator(new List<IItem> { valueConfiguration.Value }.GetEnumerator());
          }
        }
        valueEnumerator.Reset();
        enumerators.Add(valueEnumerator);
      }

      var rangeVc = node as RangeValueConfiguration;
      if (rangeVc != null) {
        valueEnumerator = new EnumeratorCollectionEnumerator<IItem>();
        valueEnumerator.AddEnumerator(rangeVc.RangeConstraint.GetCombinations().GetEnumerator());
        valueEnumerator.Reset();
        enumerators.Add(valueEnumerator);
      }

      var parameterizedVc = node as ParameterizedValueConfiguration;
      if (parameterizedVc != null) {
        foreach (var parameterConfiguration in parameterizedVc.ParameterConfigurations) {
          if (parameterConfiguration.Optimize) {
            var enumerator = new ParameterCombinationsEnumerator(parameterConfiguration);
            enumerator.Reset();
            enumerators.Add(enumerator);
          }
        }
        enumerators.Reverse(); // this makes the list of combinations better readable
      }
    }
  }

  /// <summary>
  /// Enumerator which can enumerate all elements of a list of enumerators
  /// </summary>
  /// <typeparam name="T"></typeparam>
  public class EnumeratorCollectionEnumerator<T> : IEnumerator<T> {
    private List<IEnumerator<T>> enumerators = new List<IEnumerator<T>>();
    private IEnumerator<IEnumerator<T>> currentEnumerator;

    public EnumeratorCollectionEnumerator() { }

    public void AddEnumerator(IEnumerator<T> enumerator) {
      enumerators.Add(enumerator);
    }

    public void Dispose() { }

    public T Current {
      get { return currentEnumerator.Current.Current; }
    }

    object IEnumerator.Current {
      get { return this.Current; }
    }

    public bool MoveNext() {
      bool ok = currentEnumerator.Current.MoveNext();
      if (!ok) {
        ok = currentEnumerator.MoveNext();
        if (!ok)
          return false;
        else
          return this.MoveNext();
      }
      return true;
    }

    public void Reset() {
      foreach (var enu in enumerators) {
        enu.Reset();
      }
      currentEnumerator = enumerators.GetEnumerator();
      currentEnumerator.Reset();
      currentEnumerator.MoveNext();
    }
  }
}