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