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| 1 | +using Microsoft.Extensions.DependencyInjection; |
| 2 | +using System; |
| 3 | +using System.Collections.Generic; |
| 4 | +using System.Linq; |
| 5 | +using System.Reflection; |
| 6 | +using System.Text; |
| 7 | + |
| 8 | +namespace MediatR.Registration |
| 9 | +{ |
| 10 | + public class DynamicServiceProvider : IServiceProvider, IDisposable |
| 11 | + { |
| 12 | + private readonly IServiceProvider _rootProvider; |
| 13 | + private ServiceProvider _currentProvider; |
| 14 | + private readonly IServiceCollection _services; |
| 15 | + private readonly Type[] RequestHandlerTypes = new Type[] { typeof(IRequestHandler<>), typeof(IRequestHandler<,>) }; |
| 16 | + |
| 17 | + public DynamicServiceProvider(IServiceProvider rootProvider) |
| 18 | + { |
| 19 | + _rootProvider = rootProvider; |
| 20 | + _services = new ServiceCollection(); |
| 21 | + _currentProvider = _services.BuildServiceProvider(); |
| 22 | + } |
| 23 | + |
| 24 | + public IEnumerable<ServiceDescriptor> GetAllServiceDescriptors() |
| 25 | + { |
| 26 | + return _services; |
| 27 | + } |
| 28 | + |
| 29 | + public void AddService(Type serviceType, Type implementationType, ServiceLifetime lifetime = ServiceLifetime.Transient) |
| 30 | + { |
| 31 | + var constructor = implementationType.GetConstructors().OrderByDescending(c => c.GetParameters().Length).FirstOrDefault(); |
| 32 | + if (constructor != null) |
| 33 | + { |
| 34 | + var parameters = constructor.GetParameters(); |
| 35 | + |
| 36 | + foreach (var parameter in parameters) |
| 37 | + { |
| 38 | + // Check if the dependency is already registered |
| 39 | + if (_currentProvider.GetService(parameter.ParameterType) != null) |
| 40 | + continue; |
| 41 | + |
| 42 | + // Attempt to resolve from the root provider |
| 43 | + var dependency = _rootProvider.GetService(parameter.ParameterType); |
| 44 | + if (dependency != null) |
| 45 | + { |
| 46 | + // Dynamically register the dependency in the dynamic registry |
| 47 | + _services.Add(new ServiceDescriptor(parameter.ParameterType, _ => dependency, lifetime)); |
| 48 | + RebuildProvider(); // Rebuild the internal provider to include the new service |
| 49 | + } |
| 50 | + else |
| 51 | + { |
| 52 | + throw new InvalidOperationException( |
| 53 | + $"Unable to resolve dependency {parameter.ParameterType.FullName} for {serviceType.FullName}"); |
| 54 | + } |
| 55 | + } |
| 56 | + } |
| 57 | + _services.Add(new ServiceDescriptor(serviceType, implementationType, lifetime)); |
| 58 | + RebuildProvider(); |
| 59 | + } |
| 60 | + |
| 61 | + public void AddService(Type serviceType, Func<IServiceProvider, object> implementationFactory, ServiceLifetime lifetime = ServiceLifetime.Transient) |
| 62 | + { |
| 63 | + if (serviceType == null) throw new ArgumentNullException(nameof(serviceType)); |
| 64 | + if (implementationFactory == null) throw new ArgumentNullException(nameof(implementationFactory)); |
| 65 | + |
| 66 | + // Add the service descriptor with the factory |
| 67 | + _services.Add(new ServiceDescriptor(serviceType, implementationFactory, lifetime)); |
| 68 | + RebuildProvider(); |
| 69 | + } |
| 70 | + |
| 71 | + //public IServiceProvider RootProvider { get { return _rootProvider; } } |
| 72 | + public object? GetService(Type serviceType) |
| 73 | + { |
| 74 | + // Handle requests for IEnumerable<T> |
| 75 | + if (serviceType.IsGenericType && serviceType.GetGenericTypeDefinition() == typeof(IEnumerable<>)) |
| 76 | + { |
| 77 | + // typeof(T) for IEnumerable<T> |
| 78 | + var elementType = serviceType.GenericTypeArguments[0]; |
| 79 | + return CastToEnumerableOfType(GetServices(elementType), elementType); |
| 80 | + } |
| 81 | + |
| 82 | + // Try resolving from the current provider |
| 83 | + var service = _currentProvider.GetService(serviceType); |
| 84 | + if (service != null) return service; |
| 85 | + |
| 86 | + //fall back to root provider |
| 87 | + service = _rootProvider.GetService(serviceType); |
| 88 | + if(service != null) return service; |
| 89 | + |
| 90 | + //if not found in current or root then try to find the implementation and register it. |
| 91 | + if (serviceType.IsGenericType) |
| 92 | + { |
| 93 | + var genericArguments = serviceType.GetGenericArguments(); |
| 94 | + var hasResponseType = genericArguments.Length > 1; |
| 95 | + var openInterface = hasResponseType ? typeof(IRequestHandler<,>) : typeof(IRequestHandler<>); |
| 96 | + |
| 97 | + if(openInterface != null) |
| 98 | + { |
| 99 | + var requestType = genericArguments[0]; |
| 100 | + Type? responseType = hasResponseType ? genericArguments[1] : null; |
| 101 | + |
| 102 | + var implementationType = FindOpenGenericHandlerType(requestType, responseType); |
| 103 | + if(implementationType == null) |
| 104 | + throw new InvalidOperationException($"No implementation found for {openInterface.FullName}"); |
| 105 | + |
| 106 | + AddService(serviceType, implementationType); |
| 107 | + } |
| 108 | + } |
| 109 | + |
| 110 | + //find the newly registered service |
| 111 | + service = _currentProvider.GetService(serviceType); |
| 112 | + if (service != null) return service; |
| 113 | + |
| 114 | + // Fallback to the root provider as a last resort |
| 115 | + return _rootProvider.GetService(serviceType); |
| 116 | + } |
| 117 | + |
| 118 | + public IEnumerable<object> GetServices(Type serviceType) |
| 119 | + { |
| 120 | + // Collect services from the dynamic provider |
| 121 | + var dynamicServices = _services |
| 122 | + .Where(d => d.ServiceType == serviceType) |
| 123 | + .Select(d => _currentProvider.GetService(d.ServiceType)) |
| 124 | + .Where(s => s != null); |
| 125 | + |
| 126 | + // Collect services from the root provider |
| 127 | + var rootServices = _rootProvider |
| 128 | + .GetServices(serviceType) |
| 129 | + .Cast<object>(); |
| 130 | + |
| 131 | + // Combine results and remove duplicates |
| 132 | + return dynamicServices.Concat(rootServices).Distinct()!; |
| 133 | + } |
| 134 | + |
| 135 | + private object CastToEnumerableOfType(IEnumerable<object> services, Type elementType) |
| 136 | + { |
| 137 | + var castMethod = typeof(Enumerable) |
| 138 | + .GetMethod(nameof(Enumerable.Cast)) |
| 139 | + ?.MakeGenericMethod(elementType); |
| 140 | + |
| 141 | + var toListMethod = typeof(Enumerable) |
| 142 | + .GetMethod(nameof(Enumerable.ToList)) |
| 143 | + ?.MakeGenericMethod(elementType); |
| 144 | + |
| 145 | + if (castMethod == null || toListMethod == null) |
| 146 | + throw new InvalidOperationException("Unable to cast services to the specified enumerable type."); |
| 147 | + |
| 148 | + var castedServices = castMethod.Invoke(null, new object[] { services }); |
| 149 | + return toListMethod.Invoke(null, new[] { castedServices })!; |
| 150 | + } |
| 151 | + |
| 152 | + public Type? FindOpenGenericHandlerType(Type requestType, Type? responseType = null) |
| 153 | + { |
| 154 | + if (!requestType.IsGenericType) |
| 155 | + return null; |
| 156 | + |
| 157 | + // Define the target generic handler type |
| 158 | + var openHandlerType = responseType == null ? typeof(IRequestHandler<>) : typeof(IRequestHandler<,>); |
| 159 | + var genericArguments = responseType == null ? new Type[] { requestType } : new Type[] { requestType, responseType }; |
| 160 | + var closedHandlerType = openHandlerType.MakeGenericType(genericArguments); |
| 161 | + |
| 162 | + // Get the current assembly |
| 163 | + var currentAssembly = Assembly.GetExecutingAssembly(); |
| 164 | + |
| 165 | + // Get assemblies that reference the current assembly |
| 166 | + var consumingAssemblies = AppDomain.CurrentDomain.GetAssemblies() |
| 167 | + .Where(assembly => assembly.GetReferencedAssemblies() |
| 168 | + .Any(reference => reference.FullName == currentAssembly.FullName)); |
| 169 | + |
| 170 | + // Search for matching types |
| 171 | + var types = consumingAssemblies.SelectMany(x => x.GetTypes()) |
| 172 | + .Where(t => t.IsClass && !t.IsAbstract && t.IsGenericTypeDefinition) |
| 173 | + .ToList(); |
| 174 | + |
| 175 | + foreach (var type in types) |
| 176 | + { |
| 177 | + var interfaces = type.GetInterfaces(); |
| 178 | + if (interfaces.Any(i => i.IsGenericType && i.GetGenericTypeDefinition() == openHandlerType)) |
| 179 | + { |
| 180 | + // Check generic constraints |
| 181 | + var concreteHandlerGenericArgs = type.GetGenericArguments(); |
| 182 | + var concreteHandlerConstraints = concreteHandlerGenericArgs.Select(x => x.GetGenericParameterConstraints()); |
| 183 | + var concreteRequestTypeGenericArgs = requestType.GetGenericArguments(); |
| 184 | + //var secondArgConstrants = genericArguments[1]; |
| 185 | + |
| 186 | + // Ensure the constraints are compatible |
| 187 | + if (concreteHandlerConstraints |
| 188 | + .Select((list, i) => new { List = list, Index = i }) |
| 189 | + .All(x => x.List.All(c => c.IsAssignableFrom(concreteRequestTypeGenericArgs[x.Index])))) |
| 190 | + { |
| 191 | + return type.MakeGenericType(concreteRequestTypeGenericArgs); |
| 192 | + } |
| 193 | + } |
| 194 | + } |
| 195 | + |
| 196 | + return null; // No matching type found |
| 197 | + } |
| 198 | + |
| 199 | + private void RebuildProvider() |
| 200 | + { |
| 201 | + _currentProvider.Dispose(); |
| 202 | + _currentProvider = _services.BuildServiceProvider(); |
| 203 | + } |
| 204 | + |
| 205 | + public void Dispose() |
| 206 | + { |
| 207 | + _currentProvider.Dispose(); |
| 208 | + } |
| 209 | + } |
| 210 | +} |
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