Add json support to app POST /api/report

This way you can save reports from /app/report, then use curl to post it
to the app later for testing.

app/router.go

@@ -3,6 +3,7 @@ package main
 import (
 	"compress/gzip"
 	"encoding/gob"
+	"encoding/json"
 	"net/http"
 	"net/url"
 	"strings"
@@ -87,7 +88,11 @@ func makeReportPostHandler(a Adder) http.HandlerFunc {
 			}
 		}
 
-		if err := gob.NewDecoder(reader).Decode(&rpt); err != nil {
+		decoder := gob.NewDecoder(reader).Decode
+		if strings.HasPrefix(r.Header.Get("Content-Type"), "application/json") {
+			decoder = json.NewDecoder(reader).Decode
+		}
+		if err := decoder(&rpt); err != nil {
 			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}

app/router_test.go

@@ -1,11 +1,19 @@
 package main
 
 import (
+	"bytes"
+	"encoding/gob"
+	"encoding/json"
 	"net/http"
+	"net/http/httptest"
 	"reflect"
 	"testing"
+	"time"
 
 	"github.com/gorilla/mux"
+
+	"github.com/weaveworks/scope/test"
+	"github.com/weaveworks/scope/test/fixture"
 )
 
 type v map[string]string
@@ -28,3 +36,33 @@ func TestURLMatcher(t *testing.T) {
 	test("/a/b/{c}", "/a/b/b", true, v{"c": "b"})
 	test("/a/b/{c}", "/a/b/b%2Fb", true, v{"c": "b/b"})
 }
+
+func TestReportPostHandler(t *testing.T) {
+	test := func(contentType string, encoder func(interface{}) ([]byte, error)) {
+		b, err := encoder(fixture.Report)
+		if err != nil {
+			t.Fatalf("Content-Type %s: %s", contentType, err)
+		}
+
+		r, _ := http.NewRequest("POST", "/api/report", bytes.NewReader(b))
+		r.Header.Set("Content-Type", contentType)
+		w := httptest.NewRecorder()
+		c := NewCollector(1 * time.Minute)
+		makeReportPostHandler(c).ServeHTTP(w, r)
+		if w.Code != http.StatusOK {
+			t.Fatalf("Content-Type %s: http status: %d\nbody: %s", contentType, w.Code, w.Body.String())
+		}
+		// Just check a few items, to confirm it parsed. Otherwise
+		// reflect.DeepEqual chokes on nil vs empty arrays.
+		if want, have := fixture.Report.Endpoint.Nodes, c.Report().Endpoint.Nodes; len(have) == 0 || len(want) != len(have) {
+			t.Fatalf("Content-Type %s: %v", contentType, test.Diff(have, want))
+		}
+	}
+
+	test("", func(v interface{}) ([]byte, error) {
+		buf := &bytes.Buffer{}
+		err := gob.NewEncoder(buf).Encode(v)
+		return buf.Bytes(), err
+	})
+	test("application/json", json.Marshal)
+}