namespace Caliburn.Micro.Core {
    using System;

    /// <summary>
    /// Extension methods for <see cref="IResult"/> instances.
    /// </summary>
    public static class ResultExtensions {
        /// <summary>
        /// Adds behavior to the result which is executed when the <paramref name ="result"/> was cancelled.
        /// </summary>
        /// <param name="result">The result to decorate.</param>
        /// <param name="coroutine">The coroutine to execute when <paramref name="result"/> was canceled.</param>
        /// <returns></returns>
        public static IResult WhenCancelled(this IResult result, Func<IResult> coroutine) {
            return new ContinueResultDecorator(result, coroutine);
        }

        /// <summary>
        /// Overrides <see cref="ResultCompletionEventArgs.WasCancelled"/> of the decorated <paramref name="result"/> instance.
        /// </summary>
        /// <param name="result">The result to decorate.</param>
        /// <returns></returns>
        public static IResult OverrideCancel(this IResult result) {
            return new OverrideCancelResultDecorator(result);
        }

        /// <summary>
        /// Rescues <typeparamref name="TException"/> from the decorated <paramref name="result"/> by executing a <paramref name="rescue"/> coroutine.
        /// </summary>
        /// <typeparam name = "TException">The type of the exception we want to perform the rescue on.</typeparam>
        /// <param name="result">The result to decorate.</param>
        /// <param name="rescue">The rescue coroutine.</param>
        /// <param name="cancelResult">Set to true to cancel the result after executing rescue.</param>
        /// <returns></returns>
        public static IResult Rescue<TException>(this IResult result, Func<TException, IResult> rescue,
            bool cancelResult = true)
            where TException : Exception {
            return new RescueResultDecorator<TException>(result, rescue, cancelResult);
        }

        /// <summary>
        /// Rescues any exception from the decorated <paramref name="result"/> by executing a <paramref name="rescue"/> coroutine.
        /// </summary>
        /// <param name="result">The result to decorate.</param>
        /// <param name="rescue">The rescue coroutine.</param>
        /// <param name="cancelResult">Set to true to cancel the result after executing rescue.</param>
        /// <returns></returns>
        public static IResult Rescue(this IResult result, Func<Exception, IResult> rescue,
            bool cancelResult = true) {
            return Rescue<Exception>(result, rescue, cancelResult);
        }
    }
}