Added logic and unit tests for a simple version of Header forwarding …

…(from responses from api.xmidt to some TR1D1UM caller)

src/tr1d1um/http.go

@@ -7,6 +7,7 @@ import (
 	"github.com/Comcast/webpa-common/logging"
 	"github.com/go-kit/kit/log"
 	"github.com/gorilla/mux"
+	"strings"
 )
 
 //ConversionHandler wraps the main WDMP -> WRP conversion method
@@ -67,5 +68,22 @@ func (ch *ConversionHandler) ServeHTTP(origin http.ResponseWriter, req *http.Req
 	ctx, cancel := context.WithTimeout(req.Context(), ch.sender.GetRespTimeout())
 	response, err := ch.sender.Send(ch, origin, wdmpPayload, req.WithContext(ctx))
 	cancel()
+
+	ForwardHeadersByPrefix("X", origin, response)
+
 	ch.sender.HandleResponse(ch, err, response, origin)
 }
+
+// Helper functions
+
+//ForwardHeadersByPrefix forwards header values whose keys start with the given prefix from some response
+//into an responseWriter
+func ForwardHeadersByPrefix(prefix string, origin http.ResponseWriter, resp *http.Response){
+	for headerKey, headerValues := range resp.Header {
+		if strings.HasPrefix(headerKey, prefix) {
+			for _, headerValue := range headerValues {
+				origin.Header().Add(headerKey, headerValue)
+			}
+		}
+	}
+}

src/tr1d1um/http_test.go

@@ -107,6 +107,46 @@ func TestConversionHandler(t *testing.T) {
 	})
 }
 
+func TestForwardHeadersByPrefix(t *testing.T) {
+	t.Run("NoHeaders", func(t *testing.T) {
+		assert := assert.New(t)
+		origin := httptest.NewRecorder()
+
+		ForwardHeadersByPrefix("H", origin, resp)
+		assert.Empty(origin.Header())
+	})
+
+	t.Run("MultipleHeadersFiltered", func(t *testing.T) {
+		assert := assert.New(t)
+		origin := httptest.NewRecorder()
+		resp := &http.Response{Header:http.Header{}}
+
+		resp.Header.Add("Helium", "3")
+		resp.Header.Add("Hydrogen", "5")
+		resp.Header.Add("Hydrogen", "6")
+
+		ForwardHeadersByPrefix("He", origin, resp)
+		assert.NotEmpty(origin.Header())
+		assert.EqualValues(1, len(origin.Header()))
+		assert.EqualValues("3", origin.Header().Get("Helium"))
+	})
+
+	t.Run("MultipleHeadersFilteredFullArray", func(t *testing.T) {
+		assert := assert.New(t)
+		origin := httptest.NewRecorder()
+		resp := &http.Response{Header:http.Header{}}
+
+		resp.Header.Add("Helium", "3")
+		resp.Header.Add("Hydrogen", "5")
+		resp.Header.Add("Hydrogen", "6")
+
+		ForwardHeadersByPrefix("H", origin, resp)
+		assert.NotEmpty(origin.Header())
+		assert.EqualValues(2, len(origin.Header()))
+		assert.EqualValues([]string{"5","6"}, origin.Header()["Hydrogen"])
+	})
+}
+
 func SetUpTest(encodeArg interface{}, req *http.Request) {
 	recorder := httptest.NewRecorder()
 	timeout := time.Nanosecond