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 sets the Access-Control-Allow-Methods response header 36// on a request, by matching routes based only on paths. It also handles 37// OPTIONS requests, by settings Access-Control-Allow-Methods, and then 38// returning without calling the next http handler. 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 var allMethods []string 43 44 err := r.Walk(func(route *Route, _ *Router, _ []*Route) error { 45 for _, m := range route.matchers { 46 if _, ok := m.(*routeRegexp); ok { 47 if m.Match(req, &RouteMatch{}) { 48 methods, err := route.GetMethods() 49 if err != nil { 50 return err 51 } 52 53 allMethods = append(allMethods, methods...) 54 } 55 break 56 } 57 } 58 return nil 59 }) 60 61 if err == nil { 62 w.Header().Set("Access-Control-Allow-Methods", strings.Join(append(allMethods, "OPTIONS"), ",")) 63 64 if req.Method == "OPTIONS" { 65 return 66 } 67 } 68 69 next.ServeHTTP(w, req) 70 }) 71 } 72} 73