using System;
using System.Collections.Generic;
using System.Linq;

using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;

namespace HeuristicLab.Problems.ProgramSynthesis {
  [StorableClass]
  public abstract class ErcOptionConvertible<TValue, TValueItem> : CheckedItemCollection<WeightedErcItem<TValueItem>>, IErcItem<TValue> {
    [Storable]
    protected bool isEnabled;

    public event EventHandler<bool> EnabledChanged;

    protected ErcOptionConvertible() : this(false, new WeightedErcItem<TValueItem>[0]) { }

    protected ErcOptionConvertible(bool isEnabled, params WeightedErcItem<TValueItem>[] values) : base(values) {
      this.isEnabled = isEnabled;
      SetEnabledChangedHandler(values);

      foreach (var value in values)
        SetItemCheckedState(value, value.IsEnabled);
    }

    [StorableConstructor]
    protected ErcOptionConvertible(bool deserializing)
      : base(deserializing) {
    }

    [StorableHook(HookType.AfterDeserialization)]
    // ReSharper disable once UnusedMember.Local
    private void AfterDeserialization() {
      SetEnabledChangedHandler(list);
    }

    protected ErcOptionConvertible(ErcOptionConvertible<TValue, TValueItem> origin, Cloner cloner)
      : base(origin, cloner) {
      IsEnabled = origin.IsEnabled;
    }

    private void SetEnabledChangedHandler(IEnumerable<WeightedErcItem<TValueItem>> values) {
      foreach (var item in values)
        item.EnabledChanged += ErcValueItemEnabledChanged;
    }

    protected override void OnItemsAdded(IEnumerable<WeightedErcItem<TValueItem>> items) {
      base.OnItemsAdded(items);
      SetEnabledChangedHandler(items);
    }

    protected override void OnItemsRemoved(IEnumerable<WeightedErcItem<TValueItem>> items) {
      base.OnItemsRemoved(items);

      foreach (var item in items)
        item.EnabledChanged -= ErcValueItemEnabledChanged;
    }

    private void ErcValueItemEnabledChanged(object sender, bool state) {
      SetItemCheckedState((WeightedErcItem<TValueItem>)sender, state);
    }

    protected override void OnCheckedItemsChanged(IEnumerable<WeightedErcItem<TValueItem>> items) {
      base.OnCheckedItemsChanged(items);

      foreach (var item in items) {
        item.IsEnabled = ItemChecked(item);
      }
    }

    public bool IsEnabled {
      get { return isEnabled; }
      set {
        if (value == isEnabled)
          return;

        isEnabled = value;

        if (EnabledChanged != null)
          EnabledChanged(this, value);
      }
    }

    public abstract TValue GetErcValue(IRandom random);

    protected TValue GetErcValue(IRandom random, Converter<TValueItem, TValue> converter) {
      if (Count == 0 || !IsEnabled) return default(TValue);

      var ercValueItem = list
        .Where(item => item.IsEnabled)
        .RandomWeightedOrDefault(random, x => x.Weight);

      return ercValueItem == null
        ? default(TValue)
        : converter(ercValueItem.GetErcValue(random));
    }
  }
}