feat: add support for validator resolution from dependency injection

src/request.validation/DispatchingValidator.cs

@@ -0,0 +1,69 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Collections.Concurrent;
+using System.Reflection.Metadata;
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+
+[assembly: MetadataUpdateHandler(typeof(Geekeey.Request.Validation.DispatchingValidator))]
+
+namespace Geekeey.Request.Validation;
+
+internal sealed class DispatchingValidator : IValidator
+{
+	private static readonly ConcurrentDictionary<Type, ValidatorInvoker> ValidatorsHandlers = new();
+
+	private readonly IServiceProvider _serviceProvider;
+
+	public DispatchingValidator(IServiceProvider serviceProvider)
+	{
+		_serviceProvider = serviceProvider;
+	}
+
+	public Validation Validate(ValidationContext context)
+	{
+		ArgumentNullException.ThrowIfNull(context);
+
+		if (context.Instance is null)
+		{
+			return new Validation([]);
+		}
+
+		var handler = ValidatorsHandlers.GetOrAdd(context.Instance.GetType(), static key =>
+		{
+			var type = typeof(ValidatorInvoker<>).MakeGenericType(key);
+			return (ValidatorInvoker)Activator.CreateInstance(type)!;
+		});
+
+		return handler.Validate(context, _serviceProvider);
+	}
+
+	private abstract class ValidatorInvoker
+	{
+		public abstract Validation Validate(ValidationContext context, IServiceProvider serviceProvider);
+	}
+
+	private sealed class ValidatorInvoker<T> : ValidatorInvoker
+	{
+		public override Validation Validate(ValidationContext context, IServiceProvider serviceProvider)
+		{
+			var options = serviceProvider.GetRequiredService<IOptions<ValidationOptions>>().Value;
+
+			var validators = options.GetValidators<T>(serviceProvider);
+
+			var problems = new List<Problem>();
+
+			foreach (var validator in validators)
+			{
+				if (validator.Validate(context) is { IsValid: false, Problems: { } result })
+				{
+					problems.AddRange(result);
+				}
+			}
+
+			return new Validation(problems);
+		}
+	}
+}

src/request.validation/Geekeey.Request.Validation.csproj

@@ -28,4 +28,9 @@
     <None Include="..\..\LICENSE.md" Pack="true" PackagePath="\" Visible="false" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
+    <PackageReference Include="Microsoft.Extensions.Options" />
+  </ItemGroup>
+
 </Project>

src/request.validation/IValidatorBuilder.cs

@@ -0,0 +1,17 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Geekeey.Request.Validation;
+
+/// <summary>
+/// Defines a builder for configuring validator registrations.
+/// </summary>
+public interface IValidatorBuilder
+{
+	/// <summary>
+	/// Gets the service collection where the validators are registered.
+	/// </summary>
+	IServiceCollection Services { get; }
+}

src/request.validation/ServiceCollectionExtensions.cs

@@ -0,0 +1,49 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Geekeey.Request.Validation;
+
+/// <summary>
+/// Provides extension methods for configuring and registering validator services in the <see cref="IServiceCollection"/>.
+/// </summary>
+public static class ServiceCollectionExtensions
+{
+	/// <summary>
+	/// Adds validator services to the specified <see cref="IServiceCollection"/>.
+	/// </summary>
+	/// <param name="services">The service collection to which the validator services will be added.</param>
+	/// <returns>An instance of <see cref="IValidatorBuilder"/> to configure the validator registrations.</returns>
+	public static IValidatorBuilder AddValidation(this IServiceCollection services)
+	{
+		ArgumentNullException.ThrowIfNull(services);
+
+		services.AddOptions<ValidationOptions>();
+		services.AddTransient<IValidator, DispatchingValidator>();
+
+		return new ValidatorBuilder(services);
+	}
+
+	/// <summary>
+	/// Adds validator services to the specified <see cref="IServiceCollection"/>
+	/// and configures them using the provided <see cref="Action{T}"/>.
+	/// </summary>
+	/// <param name="services">The service collection to which the validator services will be added.</param>
+	/// <param name="configure">A delegate to configure the validator builder.</param>
+	/// <returns>The service collection with the validator services added.</returns>
+	public static IServiceCollection AddValidation(this IServiceCollection services, Action<IValidatorBuilder> configure)
+	{
+		ArgumentNullException.ThrowIfNull(services);
+		ArgumentNullException.ThrowIfNull(configure);
+
+		configure(services.AddValidation());
+
+		return services;
+	}
+
+	private sealed class ValidatorBuilder(IServiceCollection services) : IValidatorBuilder
+	{
+		public IServiceCollection Services { get; } = services;
+	}
+}

src/request.validation/ValidationOptions.cs

@@ -0,0 +1,145 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Collections;
+using System.Collections.Concurrent;
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Geekeey.Request.Validation;
+
+internal sealed class ValidationOptions
+{
+	private readonly List<Type> _search = [];
+	private readonly Lazy<TypeIndex> _validatorsTypeIndex;
+
+	public ValidationOptions()
+	{
+		_validatorsTypeIndex = new Lazy<TypeIndex>(() => new ValidatorTypeIndex(_search.Distinct()));
+	}
+
+	public void Inspect(IEnumerable<Type> assembly)
+	{
+		if (_validatorsTypeIndex.IsValueCreated)
+		{
+			throw new InvalidOperationException("The type index has already been created. Cannot inspect new assemblies.");
+		}
+
+		_search.AddRange(assembly);
+	}
+
+	public IEnumerable<IValidator<T>> GetValidators<T>(IServiceProvider services)
+	{
+		return _validatorsTypeIndex.Value.Resolve<IValidator<T>>(services);
+	}
+
+	private abstract class TypeIndex
+	{
+		private readonly ConcurrentDictionary<Type, Func<IServiceProvider, IEnumerable>> _cache = new();
+
+		protected readonly Dictionary<Type, List<Type>> _closedTypeInfo = [];
+		protected readonly List<Type> _openTypeInfo = [];
+
+		protected TypeIndex(IEnumerable<Type> collection, Func<Type, bool> predicate)
+		{
+			foreach (var type in collection)
+			{
+				if (type.IsGenericTypeDefinition)
+				{
+					if (type.GetInterfaces().Any(predicate))
+					{
+						_openTypeInfo.Add(type);
+					}
+				}
+				else
+				{
+					foreach (var @interface in type.GetInterfaces().Where(predicate))
+					{
+						(_closedTypeInfo.TryGetValue(@interface, out var list) ? list : _closedTypeInfo[@interface] = []).Add(type);
+					}
+				}
+			}
+		}
+
+		public IEnumerable<T> Resolve<T>(IServiceProvider services)
+		{
+			return (IEnumerable<T>)_cache.GetOrAdd(typeof(T), CreateResolverFactory<T>)(services);
+		}
+
+		protected abstract IReadOnlyList<Type> IsAssignableTo(Type type);
+
+		private Func<IServiceProvider, IEnumerable<T>> CreateResolverFactory<T>(Type @interface)
+		{
+			var list = IsAssignableTo(@interface);
+			return ResolverFactory;
+
+			IEnumerable<T> ResolverFactory(IServiceProvider services)
+			{
+				foreach (var type in list)
+				{
+					yield return (T)ActivatorUtilities.GetServiceOrCreateInstance(services, type);
+				}
+			}
+		}
+	}
+
+	internal static bool IsValidatorType(Type type)
+	{
+		return type.IsGenericType && type.GetGenericTypeDefinition() == typeof(IValidator<>);
+	}
+
+	private sealed class ValidatorTypeIndex(IEnumerable<Type> collection)
+		: TypeIndex(collection, IsValidatorType)
+	{
+		protected override IReadOnlyList<Type> IsAssignableTo(Type @interface)
+		{
+			var result = new List<Type>();
+
+			foreach (var kvp in _closedTypeInfo)
+			{
+				if (@interface.IsAssignableFrom(kvp.Key))
+				{
+					result.AddRange(kvp.Value);
+				}
+			}
+
+			var validatedType = @interface.GetGenericArguments()[0];
+
+			foreach (var type in _openTypeInfo)
+			{
+				try
+				{
+					// open type case one: Validator<T> : IValidator<T>
+					// We try to close it with the validated type.
+					var impl = type.MakeGenericType(validatedType);
+					if (impl.IsAssignableTo(@interface))
+					{
+						result.Add(impl);
+					}
+				}
+				catch (ArgumentException)
+				{
+				}
+
+				try
+				{
+					// open type case two: Validator<T> : IValidator<Wrapper<T>>
+					// If the validated type is generic, we try to close the validator with the validated type's generic arguments.
+					if (validatedType.IsGenericType)
+					{
+						var impl = type.MakeGenericType(validatedType.GetGenericArguments());
+						if (impl.IsAssignableTo(@interface))
+						{
+							result.Add(impl);
+						}
+					}
+				}
+				catch (ArgumentException)
+				{
+				}
+			}
+
+			return result;
+		}
+	}
+}

src/request.validation/ValidatorBuilderExtensions.cs

@@ -0,0 +1,167 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Reflection;
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+
+using static Geekeey.Request.Validation.ValidationOptions;
+
+namespace Geekeey.Request.Validation;
+
+/// <summary>
+/// Provides extension methods for configuring <see cref="IValidatorBuilder"/>
+/// with additional capabilities such as searching and registering validators in assemblies or adding types directly.
+/// </summary>
+public static class ValidatorBuilderExtensions
+{
+	/// <summary>
+	/// Searches for validator types within the specified assembly and adds them to the validator
+	/// configuration.
+	/// </summary>
+	/// <param name="builder">The <see cref="IValidatorBuilder"/> to configure.</param>
+	/// <param name="assembly">The assembly to search for validator types.</param>
+	/// <returns>The <see cref="IValidatorBuilder"/> instance for further configuration.</returns>
+	public static IValidatorBuilder SearchInAssembly(this IValidatorBuilder builder, Assembly assembly)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		var exports = assembly.GetTypes()
+			.Where(type => type is { IsClass: true, IsAbstract: false })
+			.Where(IsValidatorImplementationType);
+
+		builder.Add(exports);
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Searches for validator types within the specified assembly and adds them to the validator
+	/// configuration with the given service lifetime.
+	/// </summary>
+	/// <param name="builder">The <see cref="IValidatorBuilder"/> to configure.</param>
+	/// <param name="assembly">The assembly to search for validator types.</param>
+	/// <param name="lifetime">The lifetime with which the validators are registered in the dependency injection container.</param>
+	/// <returns>The <see cref="IValidatorBuilder"/> instance for further configuration.</returns>
+	public static IValidatorBuilder SearchInAssembly(this IValidatorBuilder builder, Assembly assembly, ServiceLifetime lifetime)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		var exports = assembly.GetTypes()
+			.Where(type => type is { IsClass: true, IsAbstract: false })
+			.Where(IsValidatorImplementationType);
+
+		builder.Add(exports, lifetime);
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Adds the specified type to the validator configuration for inspection.
+	/// </summary>
+	/// <param name="builder">The <see cref="IValidatorBuilder"/> to configure.</param>
+	/// <param name="type">The type to be added to the validator configuration.</param>
+	/// <returns>The <see cref="IValidatorBuilder"/> instance for further configuration.</returns>
+	public static IValidatorBuilder Add(this IValidatorBuilder builder, Type type)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		builder.Services.AddOptions<ValidationOptions>()
+			.Configure(options => options.Inspect([type]));
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Adds the specified type to the validator configuration.
+	/// This also adds the type to the service collection with the specified lifetime,
+	/// allowing it to be resolved as a dependency.
+	/// </summary>
+	/// <param name="builder">The <see cref="IValidatorBuilder"/> used to configure the validators.</param>
+	/// <param name="type">The type to be added to the validator configuration.</param>
+	/// <param name="lifetime">The lifetime scope of the type in the service container.</param>
+	/// <returns>The <see cref="IValidatorBuilder"/> instance for further configuration.</returns>
+	public static IValidatorBuilder Add(this IValidatorBuilder builder, Type type, ServiceLifetime lifetime)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		builder.Services.AddOptions<ValidationOptions>()
+			.Configure(options => options.Inspect([type]));
+
+		builder.Services.Add(new ServiceDescriptor(type, type, lifetime));
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Adds the specified collection of types to the validator configuration for inspection.
+	/// </summary>
+	/// <param name="builder">The <see cref="IValidatorBuilder"/> to configure.</param>
+	/// <param name="types">The collection of types to be added to the validator configuration.</param>
+	/// <returns>The <see cref="IValidatorBuilder"/> instance for further configuration.</returns>
+	public static IValidatorBuilder Add(this IValidatorBuilder builder, IEnumerable<Type> types)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		var typeList = types.ToList();
+
+		builder.Services.AddOptions<ValidationOptions>()
+			.Configure(options => options.Inspect(typeList));
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Adds the specified collection of types to the validator configuration for inspection.
+	/// This also adds the specified collection of types to the service collection with the specified lifetime,
+	/// allowing it to be resolved as a dependency.
+	/// </summary>
+	/// <param name="builder">The <see cref="IValidatorBuilder"/> to configure.</param>
+	/// <param name="types">The collection of types to be added to the validator configuration.</param>
+	/// <param name="lifetime">The lifetime scope of the types in the service container.</param>
+	/// <returns>The <see cref="IValidatorBuilder"/> instance for further configuration.</returns>
+	public static IValidatorBuilder Add(this IValidatorBuilder builder, IEnumerable<Type> types, ServiceLifetime lifetime)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		var typeList = types.ToList();
+
+		builder.Services.AddOptions<ValidationOptions>()
+			.Configure(options => options.Inspect(typeList));
+
+		builder.Services.Add(typeList.Select(export => new ServiceDescriptor(export, export, lifetime)));
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Adds the specified validator type to the validator configuration.
+	/// </summary>
+	/// <typeparam name="TValidator">The type of the validator to add.</typeparam>
+	/// <param name="builder">The <see cref="IValidatorBuilder"/> to configure.</param>
+	/// <returns>The <see cref="IValidatorBuilder"/> instance for further configuration.</returns>
+	public static IValidatorBuilder Add<TValidator>(this IValidatorBuilder builder)
+		where TValidator : class, IValidator
+	{
+		return builder.Add(typeof(TValidator));
+	}
+
+	/// <summary>
+	/// Adds the specified validator type to the validator configuration with the specified lifetime.
+	/// </summary>
+	/// <typeparam name="TValidator">The type of the validator to add.</typeparam>
+	/// <param name="builder">The <see cref="IValidatorBuilder"/> to configure.</param>
+	/// <param name="lifetime">The lifetime scope of the validator in the service container.</param>
+	/// <returns>The <see cref="IValidatorBuilder"/> instance for further configuration.</returns>
+	public static IValidatorBuilder Add<TValidator>(this IValidatorBuilder builder, ServiceLifetime lifetime)
+		where TValidator : class, IValidator
+	{
+		return builder.Add(typeof(TValidator), lifetime);
+	}
+
+	private static bool IsValidatorImplementationType(Type type)
+	{
+		return type.GetInterfaces().Any(IsValidatorType);
+	}
+}

src/request.validation/ValidatorExtensions.cs

@@ -0,0 +1,23 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Request.Validation;
+
+/// <summary>
+/// Extension methods for <see cref="IValidator"/>.
+/// </summary>
+public static class ValidatorExtensions
+{
+	/// <summary>
+	/// Executes the validation logic for a specified instance of type <typeparamref name="T"/> and returns the validation result.
+	/// </summary>
+	/// <param name="validator">The <see cref="IValidator"/> instance used to perform the validation.</param>
+	/// <param name="instance">The instance of type <typeparamref name="T"/> to validate.</param>
+	/// <param name="serviceProvider">The service provider available for nested validator resolution.</param>
+	/// <param name="items">Per-call state shared across nested validation operations.</param>
+	/// <returns>A <see cref="Validation"/> object containing the results of the validation, including any problems encountered.</returns>
+	public static Validation Validate<T>(this IValidator validator, T instance, IServiceProvider? serviceProvider = null, IReadOnlyDictionary<object, object?>? items = null)
+	{
+		return validator.Validate(new ValidationContext<T>(instance, serviceProvider, items));
+	}
+}