// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

#nullable enable

using System.Diagnostics.CodeAnalysis;
using System.Threading;

namespace Microsoft.AspNetCore.Mvc.Infrastructure
{
    /// <summary>
    /// Type that provides access to an <see cref="ActionContext"/>.
    /// </summary>
    public class ActionContextAccessor : IActionContextAccessor
    {
        internal static readonly IActionContextAccessor Null = new NullActionContextAccessor();

        private static readonly AsyncLocal<ActionContext> _storage = new AsyncLocal<ActionContext>();

        /// <inheritdoc/>
        [DisallowNull]
        public ActionContext? ActionContext
        {
            get { return _storage.Value; }
            set { _storage.Value = value; }
        }

        private class NullActionContextAccessor : IActionContextAccessor
        {
            public ActionContext? ActionContext
            {
                get => null;
                set { }
            }
        }
    }
}
