// 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;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Hosting;
 
namespace Microsoft.Extensions.DependencyInjection
{
    /// <summary>
    /// Extension methods for adding hosted services to an <see cref="IServiceCollection" />.
    /// </summary>
    public static class ServiceCollectionHostedServiceExtensions
    {
        /// <summary>
        /// Add an <see cref="IHostedService"/> registration for the given type.
        /// </summary>
        /// <typeparam name="THostedService">An <see cref="IHostedService"/> to register.</typeparam>
        /// <param name="services">The <see cref="IServiceCollection"/> to register with.</param>
        /// <returns>The original <see cref="IServiceCollection"/>.</returns>
        public static IServiceCollection AddHostedService<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] THostedService>(this IServiceCollection services)
            where THostedService : class, IHostedService
        {
            services.TryAddEnumerable(ServiceDescriptor.Singleton<IHostedService, THostedService>());
 
            return services;
        }
 
        /// <summary>
        /// Add an <see cref="IHostedService"/> registration for the given type.
        /// </summary>
        /// <typeparam name="THostedService">An <see cref="IHostedService"/> to register.</typeparam>
        /// <param name="services">The <see cref="IServiceCollection"/> to register with.</param>
        /// <param name="implementationFactory">A factory to create new instances of the service implementation.</param>
        /// <returns>The original <see cref="IServiceCollection"/>.</returns>
        public static IServiceCollection AddHostedService<THostedService>(this IServiceCollection services, Func<IServiceProvider, THostedService> implementationFactory)
            where THostedService : class, IHostedService
        {
            services.TryAddEnumerable(ServiceDescriptor.Singleton<IHostedService>(implementationFactory));
 
            return services;
        }
    }
}