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

using System;
using System.Diagnostics.CodeAnalysis;

namespace Microsoft.Extensions.Options
{
    /// <summary>
    /// Monitors changes on a <typeparamref name="TOptions"/> instance.
    /// </summary>
    /// <typeparam name="TOptions">The options type.</typeparam>
    public interface IOptionsMonitor<[DynamicallyAccessedMembers(Options.DynamicallyAccessedMembers)] out TOptions>
    {
        /// <summary>
        /// Gets the current <typeparamref name="TOptions"/> instance with the <see cref="Options.DefaultName"/>.
        /// </summary>
        TOptions CurrentValue { get; }

        /// <summary>
        /// Returns a configured <typeparamref name="TOptions"/> instance with the given <paramref name="name"/>.
        /// </summary>
        /// <param name="name">The name of the <typeparamref name="TOptions"/> instance. If <see langword="null"/>, <see cref="Options.DefaultName"/>, which is the empty string, is used.</param>
        /// <returns>The <typeparamref name="TOptions"/> instance that matches the given <paramref name="name"/>.</returns>
        TOptions Get(string? name);

        /// <summary>
        /// Registers a listener to be called whenever a named <typeparamref name="TOptions"/> changes.
        /// </summary>
        /// <param name="listener">The action to be invoked when <typeparamref name="TOptions"/> has changed.</param>
        /// <returns>An <see cref="IDisposable"/> that should be disposed to stop listening for changes.</returns>
        IDisposable? OnChange(Action<TOptions, string?> listener);
    }
}