created mapping router

mapping_router.go

@@ -0,0 +1,28 @@
+package flog
+
+
+// NewMappingRouter returns an initialized MappingRouter.
+func NewMappingRouter(subrouter Router, fn func(string, map[string]interface{})(string, map[string]interface{})) *MappingRouter {
+	router := MappingRouter{
+		subrouter:subrouter,
+		fn:fn,
+	}
+
+	return &router
+}
+
+
+// MappingRouter is a Router that can modify the message and context before
+// re-routing it to its sub-router.
+//
+// Conceptually this is somewhat similar to "map" functions in functional
+// programming.
+type MappingRouter struct {
+	subrouter Router
+	fn func(string, map[string]interface{})(string, map[string]interface{})
+}
+
+
+func (router *MappingRouter) Route(message string, context map[string]interface{}) error {
+	return router.subrouter.Route(router.fn(message, context))
+}