Toolkit2/Framework/Foundation/Extensions/IServiceCollectionExtensions.cs

using Mediator;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;

namespace Toolkit.Framework.Foundation;

public static class IServiceCollectionExtensions
{
    public static IServiceCollection AddHandler<TRequestHandler>(this IServiceCollection services) where TRequestHandler : notnull
    {
        if (typeof(TRequestHandler).GetInterface(typeof(IRequestHandler<,>).Name) is { } contract)
        {
            if (contract.GetGenericArguments() is { Length: 2 } arguments)
            {
                Type requestType = arguments[0];
                Type responseType = arguments[1];
                Type wrapperType = typeof(RequestClassHandlerWrapper<,>).MakeGenericType(requestType, responseType);

                services.TryAdd(new ServiceDescriptor(typeof(TRequestHandler), typeof(TRequestHandler), ServiceLifetime.Transient));
                services.Add(new ServiceDescriptor(wrapperType,
                    sp =>
                    {
                        return sp.GetService<IServiceFactory>()?.Create(wrapperType, sp.GetRequiredService<TRequestHandler>(), sp.GetServices(typeof(IPipelineBehavior<,>).MakeGenericType(requestType, responseType)))!;
                    },
                    ServiceLifetime.Transient
                ));

            }
        }

        return services;
    }

    public static IServiceCollection AddFoundation(this IServiceCollection serviceCollection)
    {
        serviceCollection
            .AddSingleton<IMediator, Mediator>()
            .AddHandler<InitializeHandler>()
            .AddSingleton<IServiceFactory>(provider => new ServiceFactory(provider.GetService, (instanceType, parameters) => ActivatorUtilities.CreateInstance(provider, instanceType, parameters!)))
            .AddHandler<ServiceFactoryHandler>()
            .AddSingleton<IInitialization, Initialization>(provider => new Initialization(() =>
            {
                return serviceCollection.Where(x => x.ServiceType.GetInterfaces()
                    .Contains(typeof(IInitializable)) || x.ServiceType == typeof(IInitializable))
                    .GroupBy(x => x.ServiceType)
                    .Select(x => x.First())
                    .SelectMany(x => provider.GetServices(x.ServiceType)
                    .Select(x => (IInitializable?)x)).ToList();
            }));

        return serviceCollection;
    }
}