// 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.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
 
namespace Microsoft.Extensions.DependencyInjection
{
    /// <summary>
    /// Extension methods for getting services from an <see cref="IServiceProvider" />.
    /// </summary>
    public static class ServiceProviderServiceExtensions
    {
        /// <summary>
        /// Get service of type <typeparamref name="T"/> from the <see cref="IServiceProvider"/>.
        /// </summary>
        /// <typeparam name="T">The type of service object to get.</typeparam>
        /// <param name="provider">The <see cref="IServiceProvider"/> to retrieve the service object from.</param>
        /// <returns>A service object of type <typeparamref name="T"/> or null if there is no such service.</returns>
        public static T? GetService<T>(this IServiceProvider provider)
        {
            ThrowHelper.ThrowIfNull(provider);
 
            return (T?)provider.GetService(typeof(T));
        }
 
        /// <summary>
        /// Get service of type <paramref name="serviceType"/> from the <see cref="IServiceProvider"/>.
        /// </summary>
        /// <param name="provider">The <see cref="IServiceProvider"/> to retrieve the service object from.</param>
        /// <param name="serviceType">An object that specifies the type of service object to get.</param>
        /// <returns>A service object of type <paramref name="serviceType"/>.</returns>
        /// <exception cref="System.InvalidOperationException">There is no service of type <paramref name="serviceType"/>.</exception>
        public static object GetRequiredService(this IServiceProvider provider, Type serviceType)
        {
            ThrowHelper.ThrowIfNull(provider);
            ThrowHelper.ThrowIfNull(serviceType);
 
            if (provider is ISupportRequiredService requiredServiceSupportingProvider)
            {
                return requiredServiceSupportingProvider.GetRequiredService(serviceType);
            }
 
            object? service = provider.GetService(serviceType);
            if (service == null)
            {
                throw new InvalidOperationException(SR.Format(SR.NoServiceRegistered, serviceType));
            }
 
            return service;
        }
 
        /// <summary>
        /// Get service of type <typeparamref name="T"/> from the <see cref="IServiceProvider"/>.
        /// </summary>
        /// <typeparam name="T">The type of service object to get.</typeparam>
        /// <param name="provider">The <see cref="IServiceProvider"/> to retrieve the service object from.</param>
        /// <returns>A service object of type <typeparamref name="T"/>.</returns>
        /// <exception cref="System.InvalidOperationException">There is no service of type <typeparamref name="T"/>.</exception>
        public static T GetRequiredService<T>(this IServiceProvider provider) where T : notnull
        {
            ThrowHelper.ThrowIfNull(provider);
 
            return (T)provider.GetRequiredService(typeof(T));
        }
 
        /// <summary>
        /// Get an enumeration of services of type <typeparamref name="T"/> from the <see cref="IServiceProvider"/>.
        /// </summary>
        /// <typeparam name="T">The type of service object to get.</typeparam>
        /// <param name="provider">The <see cref="IServiceProvider"/> to retrieve the services from.</param>
        /// <returns>An enumeration of services of type <typeparamref name="T"/>.</returns>
        public static IEnumerable<T> GetServices<T>(this IServiceProvider provider)
        {
            ThrowHelper.ThrowIfNull(provider);
 
            return provider.GetRequiredService<IEnumerable<T>>();
        }
 
        /// <summary>
        /// Get an enumeration of services of type <paramref name="serviceType"/> from the <see cref="IServiceProvider"/>.
        /// </summary>
        /// <param name="provider">The <see cref="IServiceProvider"/> to retrieve the services from.</param>
        /// <param name="serviceType">An object that specifies the type of service object to get.</param>
        /// <returns>An enumeration of services of type <paramref name="serviceType"/>.</returns>
        [RequiresDynamicCode("The native code for an IEnumerable<serviceType> might not be available at runtime.")]
        public static IEnumerable<object?> GetServices(this IServiceProvider provider, Type serviceType)
        {
            ThrowHelper.ThrowIfNull(provider);
            ThrowHelper.ThrowIfNull(serviceType);
 
            Type? genericEnumerable = typeof(IEnumerable<>).MakeGenericType(serviceType);
            return (IEnumerable<object>)provider.GetRequiredService(genericEnumerable);
        }
 
        /// <summary>
        /// Creates a new <see cref="IServiceScope"/> that can be used to resolve scoped services.
        /// </summary>
        /// <param name="provider">The <see cref="IServiceProvider"/> to create the scope from.</param>
        /// <returns>A <see cref="IServiceScope"/> that can be used to resolve scoped services.</returns>
        public static IServiceScope CreateScope(this IServiceProvider provider)
        {
            return provider.GetRequiredService<IServiceScopeFactory>().CreateScope();
        }
 
        /// <summary>
        /// Creates a new <see cref="AsyncServiceScope"/> that can be used to resolve scoped services.
        /// </summary>
        /// <param name="provider">The <see cref="IServiceProvider"/> to create the scope from.</param>
        /// <returns>An <see cref="AsyncServiceScope"/> that can be used to resolve scoped services.</returns>
        public static AsyncServiceScope CreateAsyncScope(this IServiceProvider provider)
        {
            return new AsyncServiceScope(provider.CreateScope());
        }
 
        /// <summary>
        /// Creates a new <see cref="AsyncServiceScope"/> that can be used to resolve scoped services.
        /// </summary>
        /// <param name="serviceScopeFactory">The <see cref="IServiceScopeFactory"/> to create the scope from.</param>
        /// <returns>An <see cref="AsyncServiceScope"/> that can be used to resolve scoped services.</returns>
        public static AsyncServiceScope CreateAsyncScope(this IServiceScopeFactory serviceScopeFactory)
        {
            return new AsyncServiceScope(serviceScopeFactory.CreateScope());
        }
    }
}