// 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 Microsoft.AspNetCore.Mvc.ApiExplorer;
using Microsoft.Extensions.DependencyInjection.Extensions;

namespace Microsoft.Extensions.DependencyInjection
{
    /// <summary>
    /// Extensions for configuring ApiExplorer using an <see cref="IMvcCoreBuilder"/>.
    /// </summary>
    public static class MvcApiExplorerMvcCoreBuilderExtensions
    {
        /// <summary>
        /// Configures <see cref="IMvcCoreBuilder"/> to use ApiExplorer.
        /// </summary>
        /// <param name="builder">The <see cref="IMvcCoreBuilder"/>.</param>
        /// <returns>The <see cref="IMvcCoreBuilder"/>.</returns>
        public static IMvcCoreBuilder AddApiExplorer(this IMvcCoreBuilder builder)
        {
            if (builder == null)
            {
                throw new ArgumentNullException(nameof(builder));
            }

            AddApiExplorerServices(builder.Services);
            return builder;
        }

        // Internal for testing.
        internal static void AddApiExplorerServices(IServiceCollection services)
        {
            services.TryAddSingleton<IApiDescriptionGroupCollectionProvider, ApiDescriptionGroupCollectionProvider>();
            services.TryAddEnumerable(
                ServiceDescriptor.Transient<IApiDescriptionProvider, DefaultApiDescriptionProvider>());
        }
    }
}
