using System;
using System.Collections.Generic;
using System.Reflection;
using Chernobyl.Attribution;
using Chernobyl.Reflection;

namespace Chernobyl.Extensions
{
    /// <summary>
    /// Extensions and utility methods for <see cref="Callback{T}"/>.
    /// </summary>
    public static class CallbackExtensions
    {
        /// <summary>
        /// Returns the <see cref="Callback{T}"/> as its <see cref="Action{T1}"/>
        /// equivalent.
        /// </summary>
        /// <typeparam name="T">The type returned to the response channel.</typeparam>
        /// <param name="callback">The method to return as an <see cref="Action{T1}"/>.</param>
        /// <returns><paramref name="callback"/> as <see cref="Action{T1}"/>.</returns>
        public static Action<T> AsAction<T>(this Callback<T> callback)
        {
            return new Action<T>(callback);
        }

        /// <summary>
        /// Returns the <see cref="Action{T1}"/> as its <see cref="Callback{T}"/>
        /// equivalent.
        /// </summary>
        /// <typeparam name="T">The type returned to the response channel.</typeparam>
        /// <param name="action">The method to return as an <see cref="Callback{T1}"/>.</param>
        /// <returns><paramref name="action"/> as <see cref="Callback{T1}"/>.</returns>
        public static Callback<T> AsCallback<T>(this Action<T> action)
        {
            return new Callback<T>(action);
        }

        /// <summary>
        /// Projects each element of a callback into a new form using the 
        /// specified selector.
        /// </summary>
        /// <typeparam name="TSource">The type of the callback origin.</typeparam>
        /// <typeparam name="TResult">The type of the callback destination.</typeparam>
        /// <param name="callback">The method to receive the result.</param>
        /// <param name="selector">The method that will convert the source to 
        /// the result.</param>
        /// <returns>The method to receive the source.</returns>
        public static Callback<TSource> Select<TSource, TResult>(
            this Callback<TResult> callback, Func<TSource, TResult> selector)
        {
            return source =>
            {
                var result = selector(source);
                callback(result);
            };
        }
    }
}