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package mux
import (
"net/http"
"strings"
)
// MiddlewareFunc is a function which receives an http.Handler and returns another http.Handler.
// Typically, the returned handler is a closure which does something with the http.ResponseWriter and http.Request passed
// to it, and then calls the handler passed as parameter to the MiddlewareFunc.
type MiddlewareFunc func(http.Handler) http.Handler
// middleware interface is anything which implements a MiddlewareFunc named Middleware.
type middleware interface {
Middleware(handler http.Handler) http.Handler
}
// Middleware allows MiddlewareFunc to implement the middleware interface.
func (mw MiddlewareFunc) Middleware(handler http.Handler) http.Handler {
return mw(handler)
}
// 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.
func (r *Router) Use(mwf ...MiddlewareFunc) {
for _, fn := range mwf {
r.middlewares = append(r.middlewares, fn)
}
}
// 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.
func (r *Router) useInterface(mw middleware) {
r.middlewares = append(r.middlewares, mw)
}
// CORSMethodMiddleware automatically sets the Access-Control-Allow-Methods response header
// on requests for routes that have an OPTIONS method matcher to all the method matchers on
// the route. Routes that do not explicitly handle OPTIONS requests will not be processed
// by the middleware. See examples for usage.
func CORSMethodMiddleware(r *Router) MiddlewareFunc {
return func(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
allMethods, err := getAllMethodsForRoute(r, req)
if err == nil {
for _, v := range allMethods {
if v == http.MethodOptions {
w.Header().Set("Access-Control-Allow-Methods", strings.Join(allMethods, ","))
}
}
}
next.ServeHTTP(w, req)
})
}
}
// getAllMethodsForRoute returns all the methods from method matchers matching a given
// request.
func getAllMethodsForRoute(r *Router, req *http.Request) ([]string, error) {
var allMethods []string
err := r.Walk(func(route *Route, _ *Router, _ []*Route) error {
for _, m := range route.matchers {
if _, ok := m.(*routeRegexp); ok {
if m.Match(req, &RouteMatch{}) {
methods, err := route.GetMethods()
if err != nil {
return err
}
allMethods = append(allMethods, methods...)
}
break
}
}
return nil
})
return allMethods, err
}
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