// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System.Threading;
using System.Threading.Tasks;

namespace System.Web.Http.ExceptionHandling
{
    /// <summary>
    /// Represents an exception handler that leaves exceptions unhandled (allowing them to propagate).
    /// </summary>
    /// <remarks>
    /// This class represents the behavior of having no IExceptionHandler service, such as when the registered service
    /// is removed (Null Object pattern).
    /// </remarks>
    internal class EmptyExceptionHandler : IExceptionHandler
    {
        public Task HandleAsync(ExceptionHandlerContext context, CancellationToken cancellationToken)
        {
            // For exceptions at the top of the call stack, Result will start out non-null (due to
            // LastChanceExceptionHandler). This class does not force exceptions back to unhandled in such cases, so it
            // will not not trigger the host-level exception processing, such as the ASP.NET yellow screen.
            return TaskHelpers.Completed();
        }
    }
}