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

namespace Neo.Afx.Collections
{
    /// <summary>
    /// Represents an observable collection of objects.
    /// </summary>
    public class ObservableCollection : ICollection, INotifyCollectionChanged
    {
        readonly List<object> _contents = new List<object>();

        /// <summary>
        /// Occurs when the items list of the collection has changed, or the collection is reset.
        /// </summary>
        public event NotifyCollectionChangedEventHandler CollectionChanged;

        /// <summary>
        /// Initializes a new instance of the <see cref="ObservableCollection"/> class.
        /// </summary>
        public ObservableCollection()
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ObservableCollection"/> class.
        /// </summary>
        /// <param name="collection">The collection to be added.</param>
        public ObservableCollection(IEnumerable collection)
        {
            AddRange(collection);
        }

        #region IEnumerable Members

        #region GetEnumerator

        /// <summary>
        /// Returns an enumerator that iterates through a collection.
        /// </summary>
        /// <returns>
        /// An <see cref="T:System.Collections.IEnumerator"/> object that can be used to iterate through the collection.
        /// </returns>
        public IEnumerator GetEnumerator()
        {
            return _contents.GetEnumerator();
        }

        #endregion

        #endregion

        #region ICollection Members

        #region CopyTo

        /// <summary>
        /// Copies the elements of the <see cref="T:System.Collections.ICollection"/> to an <see cref="T:System.Array"/>, starting at a particular <see cref="T:System.Array"/> index.
        /// </summary>
        /// <param name="array">The one-dimensional <see cref="T:System.Array"/> that is the destination of the elements copied from <see cref="T:System.Collections.ICollection"/>. The <see cref="T:System.Array"/> must have zero-based indexing.</param>
        /// <param name="index">The zero-based index in <paramref name="array"/> at which copying begins.</param>
        /// <exception cref="T:System.ArgumentNullException">
        /// 	<paramref name="array"/> is null. 
        /// </exception>
        /// <exception cref="T:System.ArgumentOutOfRangeException">
        /// 	<paramref name="index"/> is less than zero. 
        /// </exception>
        /// <exception cref="T:System.ArgumentException">
        /// 	<paramref name="array"/> is multidimensional.-or- The number of elements in the source <see cref="T:System.Collections.ICollection"/> is greater than the available space from <paramref name="index"/> to the end of the destination <paramref name="array"/>.-or- The type of the source <see cref="T:System.Collections.ICollection"/> cannot be cast automatically to the type of the destination <paramref name="array"/>
        /// </exception>
        public void CopyTo(Array array, int index)
        {
            var j = index;
            for(var i = 0; i < Count; i++)
            {
                array.SetValue(_contents[i], j);
                j++;
            }

        }

        #endregion

        #region Count

        /// <summary>
        /// Gets the number of elements contained in the <see cref="T:System.Collections.ICollection"/>.
        /// </summary>
        /// <value></value>
        /// <returns>The number of elements contained in the <see cref="T:System.Collections.ICollection"/>.</returns>
        public int Count
        {
            get
            {
                return _contents.Count;
            }
        }

        #endregion

        #region IsSynchronized

        /// <summary>
        /// Gets a value indicating whether access to the <see cref="T:System.Collections.ICollection"/> is synchronized (thread safe).
        /// </summary>
        /// <value>false</value>
        /// <returns>true if access to the <see cref="T:System.Collections.ICollection"/> is synchronized (thread safe); otherwise, false.</returns>
        public bool IsSynchronized
        {
            get
            {
                return false;
            }
        }

        #endregion

        #region SyncRoot

        /// <summary>
        /// Gets an object that can be used to synchronize access to the <see cref="T:System.Collections.ICollection"/>.
        /// <remarks>
        /// Return the current instance since the underlying store is not publicly available
        /// </remarks>
        /// </summary>
        /// <value></value>
        /// <returns>An object that can be used to synchronize access to the <see cref="T:System.Collections.ICollection"/>.</returns>
        public object SyncRoot
        {
            get
            {
                return this;
            }
        }

        #endregion

        #endregion

        #region AddRange

        /// <summary>
        /// Adds the specified collection.
        /// </summary>
        /// <param name="collection">The collection to be added.</param>
        public void AddRange(IEnumerable collection)
        {
            _contents.AddRange(collection.Cast<object>());
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
        }

        #endregion

        #region Clear

        /// <summary>
        /// Clears the collection.
        /// </summary>
        public void Clear()
        {
            _contents.Clear();
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
        }

        #endregion

        /// <summary>
        /// Raises the <see cref="CollectionChanged"/> event.
        /// </summary>
        /// <param name="e">The <see cref="System.Collections.Specialized.NotifyCollectionChangedEventArgs"/> instance containing the event data.</param>
        protected virtual void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            if(CollectionChanged != null)
            {
                CollectionChanged(this, e);
            }
        }
    }
}