using System;
using System.Collections.ObjectModel;

namespace Framework.Support {

  /// <summary>Collection that sends notifications when its contents change</summary>
  /// <typeparam name="TItem">Type of items that will be managed in the collection</typeparam>
  public class ObservableCollection<TItem> : Collection<TItem>, IObservableCollection<TItem> {

    /// <summary>Called before the collection is cleared</summary>
    public event Action Clearing;
    /// <summary>Called after the collection has been cleared</summary>
    public event Action Cleared;
    /// <summary>Called when an item has been added into the collection</summary>
    public event Action<TItem> ItemAdded;
    /// <summary>Called before an item gets removed from the collection</summary>
    public event Action<TItem> ItemRemoved;

    /// <summary>Called when the collection is cleared of all its items</summary>
    protected override void ClearItems() {
      if(Clearing != null) {
        Clearing();
      }
      base.ClearItems();
      if(Cleared != null) {
        Cleared();
      }
    }

    /// <summary>Called when an item gets inserted into the collection</summary>
    /// <param name="index">Index at which the item is inserted</param>
    /// <param name="item">Item that is being inserted</param>
    protected override void InsertItem(int index, TItem item) {
      base.InsertItem(index, item);
      if(ItemAdded != null) {
        ItemAdded(item);
      }
    }

    /// <summary>Called when an item is removed from the collection</summary>
    /// <param name="index">Index at which the item is being removed</param>
    protected override void RemoveItem(int index) {
      if(ItemRemoved != null) {
        ItemRemoved(Items[index]);
      }
      base.RemoveItem(index);
    }

    /// <summary>Called when an item gets overwritten in the collection</summary>
    /// <param name="index">Index at which an item is being overwritten</param>
    /// <param name="item">
    ///   Item with which the item at the specified index is being overwritten
    /// </param>
    protected override void SetItem(int index, TItem item) {
      if(ItemRemoved != null) {
        ItemRemoved(Items[index]);
      }
      base.SetItem(index, item);
      if(ItemAdded != null) {
        ItemAdded(item);
      }
    }

  }

} // namespace Framework.Support