more work on rewrites

lib/httplib/httplib.go

@@ -23,6 +23,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"regexp"
 	"strconv"
 
 	"github.com/gravitational/roundtrip"
@@ -113,3 +114,30 @@ func ParseBool(q url.Values, name string) (bool, bool, error) {
 	}
 	return val, true, nil
 }
+
+// RewritePair is a rewrite expression
+type RewritePair struct {
+	// Expr is matching expression
+	Expr *regexp.Regexp
+	// Replacement is replacement
+	Replacement string
+}
+
+// Rewrite creates a rewrite pair, panics if in epxression
+// is not a valid regular expressoin
+func Rewrite(in, out string) *RewritePair {
+	return &RewritePair{
+		Expr:        regexp.MustCompile(in),
+		Replacement: out,
+	}
+}
+
+// RewritePaths creates a middleware that rewrites paths in incoming request
+func RewritePaths(next http.Handler, rewrites ...RewritePair) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		for _, rewrite := range rewrites {
+			req.URL.Path = rewrite.Expr.ReplaceAllString(req.URL.Path, rewrite.Replacement)
+		}
+		next.ServeHTTP(w, req)
+	})
+}

lib/httplib/httplib_test.go

@@ -0,0 +1,60 @@
+/*
+Copyright 2016 Gravitational, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package httplib
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/julienschmidt/httprouter"
+	. "gopkg.in/check.v1"
+)
+
+func TestHTTP(t *testing.T) { TestingT(t) }
+
+type HTTPSuite struct {
+}
+
+var _ = Suite(&HTTPSuite{})
+
+func (s *HTTPSuite) TestRewritePaths(c *C) {
+	RewritePaths(newTestHandler(), Rewrite("/v1/sessions/([^/]+)/stream", "/v1/namespaces/default/sessions/1/stream"))
+}
+
+type testHandler struct {
+	httprouter.Router
+	capturedNamespace string
+	capturedID        string
+}
+
+func newTestHandler() http.Handler {
+	h := &testHandler{}
+	h.Router = *httprouter.New()
+	h.POST("/v1/sessions/:id/stream", MakeHandler(h.postSessionChunkOriginal))
+	h.POST("/v1/namespaces/:namespace/sessions/:id/stream", MakeHandler(h.postSessionChunkNamespace))
+	return h
+}
+
+func (h *testHandler) postSessionChunkOriginal(w http.ResponseWriter, r *http.Request, p httprouter.Params) (interface{}, error) {
+	return "ok", nil
+}
+
+func (h *testHandler) postSessionChunkNamespace(w http.ResponseWriter, r *http.Request, p httprouter.Params) (interface{}, error) {
+	h.capturedNamespace = p.ByName("namespace")
+	h.capturedID = p.ByName("id")
+	return "ok", nil
+}