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

using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Diagnostics.HealthChecks;
using Microsoft.Extensions.Hosting;

namespace Microsoft.Extensions.DependencyInjection
{
    /// <summary>
    /// Provides extension methods for registering <see cref="HealthCheckService"/> in an <see cref="IServiceCollection"/>.
    /// </summary>
    public static class HealthCheckServiceCollectionExtensions
    {
        /// <summary>
        /// Adds the <see cref="HealthCheckService"/> to the container, using the provided delegate to register
        /// health checks.
        /// </summary>
        /// <remarks>
        /// This operation is idempotent - multiple invocations will still only result in a single
        /// <see cref="HealthCheckService"/> instance in the <see cref="IServiceCollection"/>. It can be invoked
        /// multiple times in order to get access to the <see cref="IHealthChecksBuilder"/> in multiple places.
        /// </remarks>
        /// <param name="services">The <see cref="IServiceCollection"/> to add the <see cref="HealthCheckService"/> to.</param>
        /// <returns>An instance of <see cref="IHealthChecksBuilder"/> from which health checks can be registered.</returns>
        public static IHealthChecksBuilder AddHealthChecks(this IServiceCollection services)
        {
            services.TryAddSingleton<HealthCheckService, DefaultHealthCheckService>();
            services.TryAddEnumerable(ServiceDescriptor.Singleton<IHostedService, HealthCheckPublisherHostedService>());
            return new HealthChecksBuilder(services);
        }
    }
}
