using System;
using System.Collections.Generic;
using System.Linq;
using Chernobyl.Utility;

namespace Chernobyl.Collections.Generic.Event
{
    /// <summary>
    /// A list type that extends an IList using the decorator pattern 
    /// (http://en.wikipedia.org/wiki/Decorator_pattern) by giving it add and
    /// removal events.
    /// </summary>
    /// <typeparam name="T">The type that is to be held within the list.</typeparam>
    public class DecoratingEventList<T> : EventList<T>
    {
        /// <summary>
        /// Constructor that creates an event list that uses a <see cref="List{T}"/> 
        /// as it's internal list implementation.
        /// </summary>
        public DecoratingEventList() : this(new List<T>())
        {}

        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="listDecorated">The <see cref="IList{T}" /> being 
        /// decorated or extended with event capabilities.</param>
        public DecoratingEventList(IList<T> listDecorated)
        {
            listDecorated.ThrowIfNull("list");
            _listDecorated = listDecorated;
        }

        /// <summary>
        /// The <see cref="IList{T}" /> being decorated or extended with event
        /// capabilities.
        /// </summary>
        protected override IList<T> ListDecorated
        {
            get { return _listDecorated; }
        }

        /// <summary>
        /// The backing field to <see cref="ListDecorated"/>.
        /// </summary>
        readonly IList<T> _listDecorated;
    }

    /// <summary>
    /// Extensions and utilities for <see cref="DecoratingEventList{T}"/> and 
    /// related types.
    /// </summary>
    public static class DecoratingEventListExtensions
    {
        /// <summary>
        /// Creates an <see cref="EventList{T}"/> from an 
        /// <see cref="IEnumerable{T}"/>.
        /// </summary>
        /// <typeparam name="T">The type of the elements of source.</typeparam>
        /// <param name="source">The <see cref="IEnumerable{T}"/> to create a 
        /// <see cref="EventList{T}"/> from.</param>
        /// <returns>A <see cref="EventList{T}"/> that contains elements from the 
        /// input sequence.</returns>
        /// <exception cref="ArgumentNullException">Thrown if 
        /// <paramref name="source"/> is null.</exception>
        public static EventList<T> ToEventList<T>(this IEnumerable<T> source)
        {
            source.ThrowIfNull("source");
            return source.ToList().ToEventList();
        }

        /// <summary>
        /// Creates an <see cref="EventList{T}"/> from an 
        /// <see cref="IList{T}"/>.
        /// </summary>
        /// <typeparam name="T">The type of the elements of source.</typeparam>
        /// <param name="source">The <see cref="IList{T}"/> to create a 
        /// <see cref="EventList{T}"/> from.</param>
        /// <returns>A <see cref="EventList{T}"/> that contains elements from the 
        /// input sequence.</returns>
        /// <exception cref="ArgumentNullException">Thrown if 
        /// <paramref name="source"/> is null.</exception>
        public static EventList<T> ToEventList<T>(this IList<T> source)
        {
            return new DecoratingEventList<T>(source);
        }
    }
}