proxy: add readonly handler

proxy/proxy.go

@@ -31,3 +31,19 @@ func NewHandler(endpoints []string) (http.Handler, error) {
 
 	return &rp, nil
 }
+
+func readonlyHandlerFunc(next http.Handler) func(http.ResponseWriter, *http.Request) {
+	return func(w http.ResponseWriter, req *http.Request) {
+		if req.Method != "GET" {
+			w.WriteHeader(http.StatusNotImplemented)
+			return
+		}
+
+		next.ServeHTTP(w, req)
+	}
+}
+
+func NewReadonlyHandler(hdlr http.Handler) http.Handler {
+	readonly := readonlyHandlerFunc(hdlr)
+	return http.HandlerFunc(readonly)
+}

proxy/proxy_test.go

@@ -0,0 +1,39 @@
+package proxy
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestReadonlyHandler(t *testing.T) {
+	fixture := func(w http.ResponseWriter, req *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}
+	hdlrFunc := readonlyHandlerFunc(http.HandlerFunc(fixture))
+
+	tests := []struct {
+		method string
+		want   int
+	}{
+		// GET is only passing method
+		{"GET", http.StatusOK},
+
+		// everything but GET is StatusNotImplemented
+		{"POST", http.StatusNotImplemented},
+		{"PUT", http.StatusNotImplemented},
+		{"PATCH", http.StatusNotImplemented},
+		{"DELETE", http.StatusNotImplemented},
+		{"FOO", http.StatusNotImplemented},
+	}
+
+	for i, tt := range tests {
+		req, _ := http.NewRequest(tt.method, "http://example.com", nil)
+		rr := httptest.NewRecorder()
+		hdlrFunc(rr, req)
+
+		if tt.want != rr.Code {
+			t.Errorf("#%d: incorrect HTTP status code: method=%s want=%d got=%d", i, tt.method, tt.want, rr.Code)
+		}
+	}
+}