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SubscriptionBuilder.cs
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SubscriptionBuilder.cs
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// Copyright (C) Ubiquitous AS. All rights reserved
// Licensed under the Apache License, Version 2.0.
using System.Reflection;
using Eventuous.Diagnostics;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Options;
namespace Eventuous.Subscriptions.Registrations;
using Consumers;
using Context;
using Filters;
public abstract class SubscriptionBuilder(IServiceCollection services, string subscriptionId) {
public string SubscriptionId { get; } = subscriptionId;
public IServiceCollection Services { get; } = services;
readonly List<ResolveHandler> _handlers = new();
protected ConsumePipe Pipe { get; } = new();
protected ResolveConsumer ResolveConsumer { get; set; } = null!;
protected IEventHandler[] ResolveHandlers(IServiceProvider sp)
=> _handlers.Select(x => x(sp)).ToArray();
/// <summary>
/// Adds an event handler to the subscription
/// </summary>
/// <typeparam name="THandler">Event handler type</typeparam>
/// <returns></returns>
public SubscriptionBuilder AddEventHandler<THandler>()
where THandler : class, IEventHandler {
Services.TryAddSingleton<THandler>();
AddHandlerResolve(sp => sp.GetRequiredService<THandler>());
return this;
}
/// <summary>
/// Adds an event handler to the subscription
/// </summary>
/// <param name="getHandler">A function to resolve event handler using the service provider</param>
/// <typeparam name="THandler"></typeparam>
/// <returns></returns>
public SubscriptionBuilder AddEventHandler<THandler>(Func<IServiceProvider, THandler> getHandler)
where THandler : class, IEventHandler {
Services.TryAddSingleton(getHandler);
AddHandlerResolve(sp => sp.GetRequiredService<THandler>());
return this;
}
public SubscriptionBuilder AddCompositionEventHandler<THandler, TWrappingHandler>(Func<THandler, TWrappingHandler> getWrappingHandler)
where THandler : class, IEventHandler where TWrappingHandler : class, IEventHandler {
Services.TryAddSingleton<THandler>();
AddHandlerResolve(sp => getWrappingHandler(sp.GetRequiredService<THandler>()));
return this;
}
public SubscriptionBuilder AddCompositionEventHandler<THandler, TWrappingHandler>(
Func<IServiceProvider, THandler> getInnerHandler,
Func<THandler, TWrappingHandler> getWrappingHandler
) where THandler : class, IEventHandler where TWrappingHandler : class, IEventHandler {
Services.TryAddSingleton(getInnerHandler);
AddHandlerResolve(sp => getWrappingHandler(sp.GetRequiredService<THandler>()));
return this;
}
/// <summary>
/// Allows using a custom consumer instead of the <see cref="DefaultConsumer"/> one.
/// Can also be used to change the default consumer instantiation.
/// </summary>
/// <param name="getConsumer">A function to resolve the consumer using the service provider</param>
/// <returns></returns>
[PublicAPI]
public SubscriptionBuilder UseConsumer(Func<IServiceProvider, IEventHandler[], IMessageConsumer> getConsumer) {
Ensure.NotNull(getConsumer);
ResolveConsumer = sp => getConsumer(sp, ResolveHandlers(sp));
return this;
}
/// <summary>
/// Add a custom filter to the consume pipe, at the end of the pipe
/// </summary>
/// <param name="filter">The filter instance</param>
/// <typeparam name="TIn">Inbound consume context type</typeparam>
/// <typeparam name="TOut">Outbound consume context type</typeparam>
/// <returns></returns>
[PublicAPI]
public SubscriptionBuilder AddConsumeFilterLast<TIn, TOut>(IConsumeFilter<TIn, TOut> filter)
where TIn : class, IBaseConsumeContext where TOut : class, IBaseConsumeContext {
Pipe.AddFilterLast(filter);
return this;
}
/// <summary>
/// Add a custom filter to the consume pipe, at the beginning of the pipe
/// </summary>
/// <param name="filter">The filter instance</param>
/// <typeparam name="TIn">Inbound consume context type</typeparam>
/// <typeparam name="TOut">Outbound consume context type</typeparam>
/// <returns></returns>
[PublicAPI]
public SubscriptionBuilder AddConsumeFilterFirst<TIn, TOut>(IConsumeFilter<TIn, TOut> filter)
where TIn : class, IBaseConsumeContext where TOut : class, IBaseConsumeContext {
Pipe.AddFilterFirst(filter);
return this;
}
void AddHandlerResolve(ResolveHandler resolveHandler)
=> _handlers.Add(
sp => {
var handler = resolveHandler(sp);
return EventuousDiagnostics.Enabled ? new TracedEventHandler(handler) : handler;
}
);
}
public class SubscriptionBuilder<T, TOptions> : SubscriptionBuilder
where T : EventSubscription<TOptions>
where TOptions : SubscriptionOptions {
public SubscriptionBuilder(IServiceCollection services, string subscriptionId)
: base(services, subscriptionId) {
ResolveConsumer = ResolveDefaultConsumer;
ConfigureOptions = options => options.SubscriptionId = subscriptionId;
}
T? _resolvedSubscription;
IMessageConsumer? _resolvedConsumer;
public Action<TOptions> ConfigureOptions { get; private set; }
ParameterMap ParametersMap { get; } = new();
/// <summary>
/// Configure subscription options
/// </summary>
/// <param name="configureOptions">Subscription options configuration function</param>
/// <returns></returns>
[PublicAPI]
public SubscriptionBuilder<T, TOptions> Configure(Action<TOptions>? configureOptions) {
ConfigureOptions = Cfg;
return this;
void Cfg(TOptions options) {
options.SubscriptionId = SubscriptionId;
configureOptions?.Invoke(options);
}
}
/// <summary>
/// Add custom dependency resolver for the subscription. The service be resolved from the service provider.
/// </summary>
/// <typeparam name="TService">Dependency type</typeparam>
/// <returns></returns>
public SubscriptionBuilder<T, TOptions> AddParameterMap<TService>() where TService : class {
ParametersMap.Add<TService, TService>();
return this;
}
/// <summary>
/// Add custom dependency resolver for the subscription. The service be resolved from the service provider.
/// </summary>
/// <typeparam name="TService">Dependency type</typeparam>
/// <typeparam name="TImplementation">Service type that implements <code>TService</code></typeparam>
/// <returns></returns>
public SubscriptionBuilder<T, TOptions> AddParameterMap<TService, TImplementation>()
where TImplementation : class, TService {
ParametersMap.Add<TService, TImplementation>();
return this;
}
/// <summary>
/// Add custom dependency resolver for the subscription.
/// The service be resolved from the service provider by using the factory function..
/// </summary>
/// <param name="resolver">Function to resolve the service from the service provider</param>
/// <typeparam name="TService">Dependency type</typeparam>
/// <returns></returns>
public SubscriptionBuilder<T, TOptions> AddParameterMap<TService>(Func<IServiceProvider, TService> resolver)
where TService : class {
ParametersMap.Add<TService, TService>(resolver);
return this;
}
/// <summary>
/// Add custom dependency resolver for the subscription.
/// The service be resolved from the service provider by using the factory function..
/// </summary>
/// <param name="resolver">Function to resolve the service from the service provider</param>
/// <typeparam name="TService">Dependency type</typeparam>
/// <typeparam name="TImplementation">Service type that implements <code>TService</code></typeparam>
/// <returns></returns>
public SubscriptionBuilder<T, TOptions> AddParameterMap<TService, TImplementation>(Func<IServiceProvider, TImplementation> resolver)
where TImplementation : class, TService {
ParametersMap.Add<TService, TImplementation>(resolver);
return this;
}
IMessageConsumer GetConsumer(IServiceProvider sp) {
if (_resolvedConsumer != null) return _resolvedConsumer;
_resolvedConsumer = ResolveConsumer(sp);
return _resolvedConsumer;
}
IMessageConsumer ResolveDefaultConsumer(IServiceProvider sp) {
_resolvedConsumer = new DefaultConsumer(ResolveHandlers(sp));
return _resolvedConsumer;
}
// ReSharper disable once CognitiveComplexity
public T ResolveSubscription(IServiceProvider sp) {
const string subscriptionIdParameterName = "subscriptionId";
if (_resolvedSubscription != null) {
return _resolvedSubscription;
}
var consumer = GetConsumer(sp);
if (EventuousDiagnostics.Enabled) {
Pipe.AddFilterLast(new TracingFilter(consumer.GetType().Name));
}
Pipe.AddFilterLast(new ConsumerFilter(consumer));
var constructors = typeof(T).GetConstructors<TOptions>();
switch (constructors.Length) {
case > 1: throw new ArgumentOutOfRangeException(typeof(T).Name, "Subscription type must have only one constructor with options argument");
case 0:
constructors = typeof(T).GetConstructors<string>(subscriptionIdParameterName);
break;
}
if (constructors.Length == 0) {
throw new ArgumentOutOfRangeException(
typeof(T).Name,
"Subscription type must have at least one constructor with options or subscription id argument"
);
}
var (ctor, parameters, parameter) = constructors[0];
var args = parameters.Select(CreateArg).ToArray();
if (ctor.Invoke(args) is not T instance) {
throw new InvalidOperationException($"Unable to instantiate {typeof(T)}");
}
_resolvedSubscription = instance;
return instance;
object? CreateArg(ParameterInfo parameterInfo) {
if (parameterInfo == parameter) {
if (parameter.Name == subscriptionIdParameterName) {
return SubscriptionId;
}
var options = Ensure.NotNull(sp.GetService<IOptionsMonitor<TOptions>>(), typeof(TOptions).Name);
return options.Get(SubscriptionId);
}
// ReSharper disable once ConvertIfStatementToReturnStatement
// ReSharper disable once InvertIf
if (parameterInfo.ParameterType == typeof(ConsumePipe)) {
return Pipe;
}
// ReSharper disable once ConvertIfStatementToReturnStatement
if (ParametersMap.TryGetResolver(parameterInfo.ParameterType, out var resolver)) {
return resolver!(sp);
}
return sp.GetService(parameterInfo.ParameterType);
}
}
}
static class TypeExtensionsForRegistrations {
public static (ConstructorInfo Ctor, ParameterInfo[] parameters, ParameterInfo? Options)[] GetConstructors<T>(this Type type, string? name = null)
=> type
.GetConstructors()
.Select(x => (Ctor: x, Parameters: x.GetParameters()))
.Select(
x => (
x.Ctor,
x.Parameters,
Options: x.Parameters.SingleOrDefault(y => y.ParameterType == typeof(T) && (name == null || y.Name == name))
)
)
.Where(x => x.Options != null)
.ToArray();
}
public delegate IEventHandler ResolveHandler(IServiceProvider sp);
public delegate IMessageConsumer ResolveConsumer(IServiceProvider sp);