Feature/inject error mapper (#562)

* added delegate to select last handler

* #529 implemented a way we can inject the last delegating handler

* wip - moving code

* #529 removed loads of qos code and moved it into Ocelot.Provider.Polly

* #529 can now inject http client expcetions to ocelot errors mappers and updated docs

src/Ocelot/Configuration/QoSOptions.cs

@@ -7,8 +7,6 @@
             int durationofBreak, 
             int timeoutValue, 
             string key,
-            //todo - this is never set in Ocelot so always Pessimistic...I guess it doesn't
-            //matter to much.
             string timeoutStrategy = "Pessimistic")
         {
             ExceptionsAllowedBeforeBreaking = exceptionsAllowedBeforeBreaking;

src/Ocelot/DependencyInjection/OcelotBuilder.cs

@@ -130,6 +130,7 @@ namespace Ocelot.DependencyInjection
             Services.TryAddSingleton<IDownstreamRequestCreator, DownstreamRequestCreator>();
             Services.TryAddSingleton<IFrameworkDescription, FrameworkDescription>();
             Services.TryAddSingleton<IQoSFactory, QoSFactory>();
+            Services.TryAddSingleton<IExceptionToErrorMapper, HttpExeptionToErrorMapper>();
         }
 
         public IOcelotBuilder AddSingletonDefinedAggregator<T>() 

src/Ocelot/Requester/HttpClientHttpRequester.cs

@@ -12,14 +12,17 @@ namespace Ocelot.Requester
         private readonly IHttpClientCache _cacheHandlers;
         private readonly IOcelotLogger _logger;
         private readonly IDelegatingHandlerHandlerFactory _factory;
+        private readonly IExceptionToErrorMapper _mapper;
 
         public HttpClientHttpRequester(IOcelotLoggerFactory loggerFactory,
             IHttpClientCache cacheHandlers,
-            IDelegatingHandlerHandlerFactory house)
+            IDelegatingHandlerHandlerFactory factory, 
+            IExceptionToErrorMapper mapper)
         {
             _logger = loggerFactory.CreateLogger<HttpClientHttpRequester>();
             _cacheHandlers = cacheHandlers;
-            _factory = house;
+            _factory = factory;
+            _mapper = mapper;
         }
 
         public async Task<Response<HttpResponseMessage>> GetResponse(DownstreamContext context)
@@ -35,7 +38,8 @@ namespace Ocelot.Requester
             }
             catch (Exception exception)
             {
-                return new ErrorResponse<HttpResponseMessage>(new UnableToCompleteRequestError(exception));
+                var error = _mapper.Map(exception);
+                return new ErrorResponse<HttpResponseMessage>(error);
             }
             finally
             {

src/Ocelot/Requester/HttpExeptionToErrorMapper.cs

@@ -0,0 +1,29 @@
+namespace Ocelot.Requester
+{
+    using System;
+    using System.Collections.Generic;
+    using Errors;
+    using Microsoft.Extensions.DependencyInjection;
+
+    public class HttpExeptionToErrorMapper : IExceptionToErrorMapper
+    {
+        private readonly Dictionary<Type, Func<Exception, Error>> _mappers;
+
+        public HttpExeptionToErrorMapper(IServiceProvider serviceProvider)
+        {
+            _mappers = serviceProvider.GetService<Dictionary<Type, Func<Exception, Error>>>();
+        }
+
+        public Error Map(Exception exception)
+        {
+            var type = exception.GetType();
+
+            if (_mappers != null && _mappers.ContainsKey(type))
+            {
+                return _mappers[type](exception);
+            }
+
+            return new UnableToCompleteRequestError(exception);
+        }
+    }
+}

src/Ocelot/Requester/IExceptionToErrorMapper.cs

@@ -0,0 +1,10 @@
+using System;
+using Ocelot.Errors;
+
+namespace Ocelot.Requester
+{
+    public interface IExceptionToErrorMapper
+    {
+        Error Map(Exception exception);
+    }
+}

src/Ocelot/Requester/ReRouteDelegatingHandler.cs

@@ -1,10 +0,0 @@
-using System.Net.Http;
-
-namespace Ocelot.Requester
-{
-    public class ReRouteDelegatingHandler<T> 
-        where T : DelegatingHandler
-    {
-        public T DelegatingHandler { get; private set; }
-    }
-}

src/Ocelot/Requester/UnableToFindDelegatingHandlerProviderError.cs

@@ -1,12 +0,0 @@
-using Ocelot.Errors;
-
-namespace Ocelot.Requester
-{
-    public class UnableToFindDelegatingHandlerProviderError : Error
-    {
-        public UnableToFindDelegatingHandlerProviderError(string message)
-            : base(message, OcelotErrorCode.UnableToFindDelegatingHandlerProviderError)
-        {
-        }
-    }
-}