1package mux 2 3import ( 4 "net/http" 5 "strings" 6) 7 8// MiddlewareFunc is a function which receives an http.Handler and returns another http.Handler. 9// Typically, the returned handler is a closure which does something with the http.ResponseWriter and http.Request passed 10// to it, and then calls the handler passed as parameter to the MiddlewareFunc. 11type MiddlewareFunc func(http.Handler) http.Handler 12 13// middleware interface is anything which implements a MiddlewareFunc named Middleware. 14type middleware interface { 15 Middleware(handler http.Handler) http.Handler 16} 17 18// Middleware allows MiddlewareFunc to implement the middleware interface. 19func (mw MiddlewareFunc) Middleware(handler http.Handler) http.Handler { 20 return mw(handler) 21} 22 23// Use appends a MiddlewareFunc to the chain. Middleware can be used to intercept or otherwise modify requests and/or responses, and are executed in the order that they are applied to the Router. 24func (r *Router) Use(mwf ...MiddlewareFunc) { 25 for _, fn := range mwf { 26 r.middlewares = append(r.middlewares, fn) 27 } 28} 29 30// useInterface appends a middleware to the chain. Middleware can be used to intercept or otherwise modify requests and/or responses, and are executed in the order that they are applied to the Router. 31func (r *Router) useInterface(mw middleware) { 32 r.middlewares = append(r.middlewares, mw) 33} 34 35// CORSMethodMiddleware automatically sets the Access-Control-Allow-Methods response header 36// on requests for routes that have an OPTIONS method matcher to all the method matchers on 37// the route. Routes that do not explicitly handle OPTIONS requests will not be processed 38// by the middleware. See examples for usage. 39func CORSMethodMiddleware(r *Router) MiddlewareFunc { 40 return func(next http.Handler) http.Handler { 41 return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) { 42 allMethods, err := getAllMethodsForRoute(r, req) 43 if err == nil { 44 for _, v := range allMethods { 45 if v == http.MethodOptions { 46 w.Header().Set("Access-Control-Allow-Methods", strings.Join(allMethods, ",")) 47 } 48 } 49 } 50 51 next.ServeHTTP(w, req) 52 }) 53 } 54} 55 56// getAllMethodsForRoute returns all the methods from method matchers matching a given 57// request. 58func getAllMethodsForRoute(r *Router, req *http.Request) ([]string, error) { 59 var allMethods []string 60 61 for _, route := range r.routes { 62 var match RouteMatch 63 if route.Match(req, &match) || match.MatchErr == ErrMethodMismatch { 64 methods, err := route.GetMethods() 65 if err != nil { 66 return nil, err 67 } 68 69 allMethods = append(allMethods, methods...) 70 } 71 } 72 73 return allMethods, nil 74} 75