proxy: add skip invoice creation param

Author: sputn1ck

proxy/service.go

@@ -103,6 +103,13 @@ type Service struct {
 	// /package_name.ServiceName/MethodName
 	AuthWhitelistPaths []string `long:"authwhitelistpaths" description:"List of regular expressions for paths that don't require authentication'"`
 
+	// AuthSkipInvoiceCreationPaths is an optional list of regular expressions
+	// that are matched against the path of the URL of a request. If the request
+	// URL matches any of those regular expressions, the call will not try to
+	// create an invoice for the request, but still try to do the l402
+	// authentication.
+	AuthSkipInvoiceCreationPaths []string `long:"authskipinvoicecreationpaths" description:"List of regular expressions for paths that will skip invoice creation'"`
+
 	freebieDB freebie.DB
 	pricer    pricer.Pricer
 }
@@ -136,6 +143,21 @@ func (s *Service) AuthRequired(r *http.Request) auth.Level {
 	return s.Auth
 }
 
+// SkipInvoiceCreation determines if an invoice should be created for a
+// given request.
+func (s *Service) SkipInvoiceCreation(r *http.Request) bool {
+	for _, pathRegexp := range s.AuthSkipInvoiceCreationPaths {
+		pathRegexp := regexp.MustCompile(pathRegexp)
+		if pathRegexp.MatchString(r.URL.Path) {
+			log.Tracef("Req path [%s] matches skip  entry "+
+				"[%s].", r.URL.Path, pathRegexp)
+			return true
+		}
+	}
+
+	return false
+}
+
 // prepareServices prepares the backend service configurations to be used by the
 // proxy.
 func prepareServices(services []*Service) error {
@@ -195,6 +217,17 @@ func prepareServices(services []*Service) error {
 			}
 		}
 
+		// Make sure all skip invoice creation regular expression entries
+		// actually compile so we run into an eventual panic during startup
+		// and not only when the request happens.
+		for _, entry := range service.AuthSkipInvoiceCreationPaths {
+			_, err := regexp.Compile(entry)
+			if err != nil {
+				return fmt.Errorf("error validating auth "+
+					"whitelist: %v", err)
+			}
+		}
+
 		// If dynamic prices are enabled then use the provided
 		// DynamicPrice options to initialise a gRPC backed
 		// pricer client.