using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Linq;

namespace Neo.Afx.Collections
{
    /// <summary>
    /// Represents a dynamic data collection that provides notifications when items get added, removed, or when the entire list is refreshed.
    /// </summary>
    /// <typeparam name="T">The type of elements in the collection.</typeparam>
    public class TrulyObservableCollection<T> : ObservableCollection<T>
    {
        bool _suppressOnCollectionChanged;

        #region Initialization

        /// <summary>
        /// Initializes a new instance of the <see cref="TrulyObservableCollection&lt;T&gt;"/> class.
        /// </summary>
        public TrulyObservableCollection()
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="TrulyObservableCollection&lt;T&gt;"/> class.
        /// </summary>
        /// <param name="items">The items to be added.</param>
        public TrulyObservableCollection(IEnumerable<T> items)
        {
            AddRange(items);
        }

        #endregion

        #region AddRange

        /// <summary>
        /// Adds the given list of items.
        /// </summary>
        /// <param name="items">The items to be added.</param>
        public void AddRange(IEnumerable<T> items)
        {
            if(items == null)
            {
                throw new ArgumentNullException("items");
            }

            if(!items.Any())
            {
                return;
            }

            try
            {
                _suppressOnCollectionChanged = true;
                foreach(var item in items)
                {
                    var localItem = item; // neccessary to avoid "access to modified closure" error
                    Add(localItem);
                }
            }
            finally
            {
                _suppressOnCollectionChanged = false;
                OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
            }
        }
        #endregion

        /// <summary>
        /// Raises the <see cref="ObservableCollection{T}.CollectionChanged"/> event.
        /// </summary>
        /// <param name="e">The <see cref="System.Collections.Specialized.NotifyCollectionChangedEventArgs"/> instance containing the event data.</param>
        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            if(!_suppressOnCollectionChanged)
            {
                base.OnCollectionChanged(e);
            }
        }

    }

}