Feature/transform headers (#204)

* New feature that lets a user do find and replace on an upstream header

* can transform downstream and upstream headers, not sure if interface is good

* can replace location header with placeholder

* added some syntax

test/Ocelot.UnitTests/Headers/HttpHeadersTransformationMiddlewareTests.cs

@@ -0,0 +1,93 @@
+using Xunit;
+using Shouldly;
+using Ocelot.Logging;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.AspNetCore.Builder;
+using Ocelot.Headers.Middleware;
+using TestStack.BDDfy;
+using System.Linq;
+using System.Threading.Tasks;
+using System;
+using Microsoft.AspNetCore.Http;
+using System.Collections.Generic;
+using Moq;
+using Ocelot.Configuration;
+using Ocelot.DownstreamRouteFinder;
+using Ocelot.Responses;
+using Ocelot.Configuration.Builder;
+using Ocelot.Headers;
+using System.Net.Http;
+
+namespace Ocelot.UnitTests.Headers
+{
+    public class HttpHeadersTransformationMiddlewareTests : ServerHostedMiddlewareTest
+    {
+        private Mock<IHttpContextRequestHeaderReplacer> _preReplacer;
+        private Mock<IHttpResponseHeaderReplacer> _postReplacer;
+        
+        public HttpHeadersTransformationMiddlewareTests()
+        {
+            _preReplacer = new Mock<IHttpContextRequestHeaderReplacer>();
+            _postReplacer = new Mock<IHttpResponseHeaderReplacer>();
+            
+            GivenTheTestServerIsConfigured();
+        }
+
+        [Fact]
+        public void should_call_pre_and_post_header_transforms()
+        {
+            this.Given(x => GivenTheFollowingRequest())
+                .And(x => GivenTheReRouteHasPreFindAndReplaceSetUp())
+                .And(x => GivenTheHttpResponseMessageIs())
+                .When(x => WhenICallTheMiddleware())
+                .Then(x => ThenTheIHttpContextRequestHeaderReplacerIsCalledCorrectly())
+                .And(x => ThenTheIHttpResponseHeaderReplacerIsCalledCorrectly())
+                .BDDfy();
+        }
+
+        private void GivenTheHttpResponseMessageIs()
+        {
+            var httpResponseMessage = new HttpResponseMessage();
+            var response = new OkResponse<HttpResponseMessage>(httpResponseMessage);
+            ScopedRepository.Setup(x => x.Get<HttpResponseMessage>("HttpResponseMessage")).Returns(response);
+        }
+
+        private void GivenTheReRouteHasPreFindAndReplaceSetUp()
+        {
+            var fAndRs = new List<HeaderFindAndReplace>();
+            var reRoute = new ReRouteBuilder().WithUpstreamHeaderFindAndReplace(fAndRs).WithDownstreamHeaderFindAndReplace(fAndRs).Build();
+            var dR = new DownstreamRoute(null, reRoute);
+            var response = new OkResponse<DownstreamRoute>(dR);
+            ScopedRepository.Setup(x => x.Get<DownstreamRoute>("DownstreamRoute")).Returns(response);
+        }
+
+        private void ThenTheIHttpContextRequestHeaderReplacerIsCalledCorrectly()
+        {
+            _preReplacer.Verify(x => x.Replace(It.IsAny<HttpContext>(), It.IsAny<List<HeaderFindAndReplace>>()), Times.Once);
+        }
+
+        private void ThenTheIHttpResponseHeaderReplacerIsCalledCorrectly()
+        {
+            _postReplacer.Verify(x => x.Replace(It.IsAny<HttpResponseMessage>(), It.IsAny<List<HeaderFindAndReplace>>()), Times.Once);
+        }
+
+        private void GivenTheFollowingRequest()
+        {
+            Client.DefaultRequestHeaders.Add("test", "test");
+        }
+
+        protected override void GivenTheTestServerServicesAreConfigured(IServiceCollection services)
+        {
+            services.AddSingleton<IOcelotLoggerFactory, AspDotNetLoggerFactory>();
+            services.AddLogging();
+            services.AddSingleton(ScopedRepository.Object);
+            services.AddSingleton(_preReplacer.Object);
+            services.AddSingleton(_postReplacer.Object);
+        }
+
+        protected override void GivenTheTestServerPipelineIsConfigured(IApplicationBuilder app)
+        {
+            app.UseHttpHeadersTransformationMiddleware();
+        }
+    }
+}