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

namespace Chernobyl.Collections.Generic.Event
{
    /// <summary>
    /// Decorates a <see cref="IDictionary{TKey, TValue}"/> type to allow client 
    /// code to know when the <see cref="IDictionary{TKey, TValue}" /> has been 
    /// modified. Also designed to make the implementation of new 
    /// <see cref="IEventDictionary{TKey, TValue}"/> easier to create.
    /// </summary>
    /// <typeparam name="TKey">The type of the key.</typeparam>
    /// <typeparam name="TValue">The type of the value.</typeparam>
    public class DecoratingEventDictionary<TKey, TValue> : EventDictionary<TKey, TValue>
    {
        /// <summary>
        /// Initializes a new instance of the 
        /// <see cref="DecoratingEventDictionary{TKey,TValue}"/> class that uses
        /// an instance of <see cref="IDictionary{TKey, TValue}"/> as the
        /// instance it is decorating.
        /// </summary>
        public DecoratingEventDictionary()
            : this(new Dictionary<TKey, TValue>())
        {}

        /// <summary>
        /// Initializes a new instance of the <see cref="DecoratingEventDictionary{TKey,TValue}"/> class.
        /// </summary>
        /// <param name="dictionaryDecorated">The instance that is being decorated with 
        /// event capabilities.</param>
        public DecoratingEventDictionary(IDictionary<TKey, TValue> dictionaryDecorated)
        {
            dictionaryDecorated.ThrowIfNull("dictionaryDecorated");
            _dictionaryDecorated = dictionaryDecorated;
        }

        /// <summary>
        /// The instance that is being decorated with event capabilities.
        /// </summary>
        protected override IDictionary<TKey, TValue> DictionaryDecorated
        {
            get { return _dictionaryDecorated; }
        }

        /// <summary>
        /// The backing field to <see cref="DictionaryDecorated"/>.
        /// </summary>
        readonly IDictionary<TKey, TValue> _dictionaryDecorated;
    }
}