using System;

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

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