Umbraco-CMS/src/Umbraco.Core/Composing/ContainerExtensions.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using Umbraco.Core.IO;

namespace Umbraco.Core.Composing
{
    /// <summary>
    /// Provides extension methods to the <see cref="IContainer"/> class.
    /// </summary>
    public static class ContainerExtensions
    {
        /// <summary>
        /// Gets an instance of a service.
        /// </summary>
        /// <typeparam name="T">The type of the service.</typeparam>
        /// <param name="container">The container.</param>
        /// <returns>An instance of the specified type.</returns>
        /// <remarks>Throws an exception if the container failed to get an instance of the specified type.</remarks>
        public static T GetInstance<T>(this IContainer container)
            => (T) container.GetInstance(typeof(T));

        /// <summary>
        /// Tries to get an instance of a service.
        /// </summary>
        /// <typeparam name="T">The type of the service.</typeparam>
        /// <returns>An instance of the specified type, or null.</returns>
        /// <remarks>Returns null if the container does not know how to get an instance
        /// of the specified type. Throws an exception if the container does know how
        /// to get an instance of the specified type, but failed to do so.</remarks>
        public static T TryGetInstance<T>(this IContainer container)
            => (T) container.TryGetInstance(typeof(T));

        /// <summary>
        /// Gets registrations for a service.
        /// </summary>
        /// <typeparam name="TService">The type of the service.</typeparam>
        /// <returns>The registrations for the service.</returns>
        public static IEnumerable<Registration> GetRegistered<TService>(this IContainer container)
            => container.GetRegistered(typeof(TService));

        /// <summary>
        /// Creates an instance with arguments.
        /// </summary>
        /// <typeparam name="T">The type of the instance.</typeparam>
        /// <param name="container">The container.</param>
        /// <param name="args">Arguments.</param>
        /// <returns>An instance of the specified type.</returns>
        /// <remarks>
        /// <para>Throws an exception if the container failed to get an instance of the specified type.</para>
        /// <para>The arguments are used as dependencies by the container.</para>
        /// </remarks>
        public static T CreateInstance<T>(this IContainer container, params object[] args)
            => (T) container.CreateInstance(typeof(T), args);

        /// <summary>
        /// Registers a service with an implementation type.
        /// </summary>
        public static void Register<TService, TImplementing>(this IContainer container, Lifetime lifetime = Lifetime.Transient)
            => container.Register(typeof(TService), typeof(TImplementing), lifetime);

        /// <summary>
        /// Registers a service as its own implementation.
        /// </summary>
        public static void Register<TService>(this IContainer container, Lifetime lifetime = Lifetime.Transient)
            => container.Register(typeof(TService), lifetime);

        /// <summary>
        /// Registers a singleton service as its own implementation.
        /// </summary>
        public static void RegisterSingleton<TService>(this IContainer container)
            => container.Register(typeof(TService), Lifetime.Singleton);

        /// <summary>
        /// Registers a singleton service with an implementation type.
        /// </summary>
        public static void RegisterSingleton<TService, TImplementing>(this IContainer container)
            => container.Register(typeof(TService), typeof(TImplementing), Lifetime.Singleton);

        /// <summary>
        /// Registers a singleton service with an implementation factory.
        /// </summary>
        public static void RegisterSingleton<TService>(this IContainer container, Func<IContainer, TService> factory)
            => container.Register(factory, Lifetime.Singleton);

        /// <summary>
        /// Registers a service with an implementing instance.
        /// </summary>
        public static void RegisterInstance<TService>(this IContainer container, TService instance)
            => container.RegisterInstance(typeof(TService), instance);

        /// <summary>
        /// Registers a base type for auto-registration.
        /// </summary>
        public static void RegisterAuto<TServiceBase>(this IContainer container)
            => container.RegisterAuto(typeof(TServiceBase));

        /// <summary>
        /// Creates an instance of a service, with arguments.
        /// </summary>
        /// <param name="container"></param>
        /// <param name="type">The type of the instance.</param>
        /// <param name="args">Named arguments.</param>
        /// <returns>An instance of the specified type.</returns>
        /// <remarks>
        /// <para>The instance type does not need to be registered into the container.</para>
        /// <para>The arguments are used as dependencies by the container. Other dependencies
        /// are retrieved from the container.</para>
        /// </remarks>
        public static object CreateInstance(this IContainer container, Type type, params object[] args)
        {
            // LightInject has this, but then it requires RegisterConstructorDependency etc and has various oddities
            // including the most annoying one, which is that it does not work on singletons (hard to fix)
            //return Container.GetInstance(type, args);

            // this method is essentially used to build singleton instances, so it is assumed that it would be
            // more expensive to build and cache a dynamic method ctor than to simply invoke the ctor, as we do
            // here - this can be discussed

            // TODO: we currently try the ctor with most parameters, but we could want to fall back to others

            var ctor = type.GetConstructors(BindingFlags.Instance | BindingFlags.Public).OrderByDescending(x => x.GetParameters().Length).FirstOrDefault();
            if (ctor == null) throw new InvalidOperationException($"Could not find a public constructor for type {type.FullName}.");

            var ctorParameters = ctor.GetParameters();
            var ctorArgs = new object[ctorParameters.Length];
            var i = 0;
            foreach (var parameter in ctorParameters)
            {
                // no! IsInstanceOfType is not ok here
                // ReSharper disable once UseMethodIsInstanceOfType
                var arg = args?.FirstOrDefault(a => parameter.ParameterType.IsAssignableFrom(a.GetType()));
                ctorArgs[i++] = arg ?? container.GetInstance(parameter.ParameterType);
            }
            return ctor.Invoke(ctorArgs);
        }

        /// <summary>
        /// Registers a filesystem.
        /// </summary>
        /// <typeparam name="TFileSystem">The type of the filesystem.</typeparam>
        /// <typeparam name="TImplementing">The implementing type.</typeparam>
        /// <param name="container">The container.</param>
        /// <param name="supportingFileSystemFactory">A factory method creating the supporting filesystem.</param>
        /// <returns>The container.</returns>
        public static IContainer RegisterFileSystem<TFileSystem, TImplementing>(this IContainer container, Func<IContainer, IFileSystem> supportingFileSystemFactory)
            where TImplementing : FileSystemWrapper, TFileSystem
        {
            container.RegisterSingleton<TFileSystem>(factory =>
            {
                var fileSystems = factory.GetInstance<FileSystems>();
                return fileSystems.GetFileSystem<TImplementing>(supportingFileSystemFactory(factory));
            });

            return container;
        }

        /// <summary>
        /// Registers a filesystem.
        /// </summary>
        /// <typeparam name="TFileSystem">The type of the filesystem.</typeparam>
        /// <param name="container">The container.</param>
        /// <param name="supportingFileSystemFactory">A factory method creating the supporting filesystem.</param>
        /// <returns>The container.</returns>
        public static IContainer RegisterFileSystem<TFileSystem>(this IContainer container, Func<IContainer, IFileSystem> supportingFileSystemFactory)
            where TFileSystem : FileSystemWrapper
        {
            container.RegisterSingleton(factory =>
            {
                var fileSystems = factory.GetInstance<FileSystems>();
                return fileSystems.GetFileSystem<TFileSystem>(supportingFileSystemFactory(factory));
            });

            return container;
        }
    }
}