/// <summary>
/// Registers a subclass of <see cref="RabbitMqService{T}"/> to be used with dependency injection.
///
/// If it is a consumer with type <c>TConsumer</c>, it is registered both as
/// <see cref="RabbitMqConsumer{TConsumer}"/> and <c>TConsumer</c>.
///
/// If it is a producer with type <c>TProducer</c>, it is registered both as
/// <see cref="RabbitMqProducer{TProducer}"/> and <c>TProducer</c>.
/// </summary>
/// <remarks>
/// It reuses an existing <see cref="IBusProxy"/> singleton, if one is found using the provided
/// <see cref="IRabbitMqConfig.Id"/>.
///
/// If not, a new <see cref="IBusProxy"/> singleton is registered.
/// </remarks>
public void Add(IServiceCollection serviceCollection)
{
var isConsumer = typeof(T).IsSubclassOf(typeof(RabbitMqConsumer <T>));
if (!isConsumer && !typeof(T).IsSubclassOf(typeof(RabbitMqProducer <T>)))
{
throw new Exception(
$"{nameof(T)}, of type {typeof(T).FullName}, must be a subclass of " +
$"{nameof(RabbitMqConsumer<T>)} or {nameof(RabbitMqProducer<T>)}.");
}
_configRabbitMqConfig ??= new RabbitMqConfig();
var busProxy = serviceCollection
.Where(serviceDescriptor =>
serviceDescriptor.Lifetime == ServiceLifetime.Singleton &&
serviceDescriptor.ServiceType == typeof(IBusProxy))
.Select(serviceDescriptor => (IBusProxy)serviceDescriptor.ImplementationInstance)
.FirstOrDefault(registeredBusProxy => registeredBusProxy.Id == _configRabbitMqConfig.Id);
// ReSharper disable once ConditionIsAlwaysTrueOrFalse
// ReSharper disable HeuristicUnreachableCode
if (busProxy == null)
{
// build an IServiceProvider early so as to ensure that an ILogger<T> can be passed to
// ConsumerErrorStrategy
var serviceProvider =
new DefaultServiceProviderFactory(new ServiceProviderOptions
{
ValidateScopes = false,
ValidateOnBuild = false
})
.CreateBuilder(serviceCollection)
.BuildServiceProvider();
var bus = RabbitMqService <T> .CreateLazyBus(
_configRabbitMqConfig, _configUseStronglyTypedMessages, _configUseCorrelationIds, serviceProvider);
busProxy = new BusProxy(_configRabbitMqConfig.Id, bus);
serviceCollection.AddSingleton(busProxy);
}
// ReSharper restore HeuristicUnreachableCode
Func <IServiceProvider, T> ServiceFactoryFactory()
{
T service = null !;
var @lock = new object();
return(serviceProvider =>
{
// ReSharper disable once ConditionIsAlwaysTrueOrFalse
if (service != null)
{
return service;
}
lock (@lock)
{
if (service != null)
{
return service;
}
// _configRabbitMqConfig must not be null here
service = RabbitMqService <T> .Create <T>(
isConsumer, busProxy, _configRabbitMqConfig !, _configOnConnected, serviceProvider);
return service;
}
});
}
var serviceFactory = ServiceFactoryFactory();
serviceCollection.AddHostedService(serviceFactory);
var serviceType = isConsumer ? typeof(RabbitMqConsumer <T>) : typeof(RabbitMqProducer <T>);
// enable injection as RabbitMqConsumer<MyConsumerType> or RabbitMqProducer<MyProducerType>
serviceCollection.AddSingleton(serviceType, serviceFactory);
// enable injection as MyConsumerType or MyProducerType
serviceCollection.AddSingleton(serviceFactory);
}