allow_cors.go

package utils

import (
	"net/http"
	"strings"

	"github.com/golang/glog"
)

func AllowCORS(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		origin := r.Header.Get("Origin")
		if origin == "" {
			return
		}
		w.Header().Set("Access-Control-Allow-Origin", origin)
		if r.Method == "OPTIONS" && r.Header.Get("Access-Control-Request-Method") != "" {
			preflightHandler(w, r)
			return
		}
		h.ServeHTTP(w, r)
	})
}

func preflightHandler(w http.ResponseWriter, r *http.Request) {
	headers := []string{"Content-Type", "Accept"}
	w.Header().Set("Access-Control-Allow-Headers", strings.Join(headers, ","))
	methods := []string{"GET", "HEAD", "POST", "PUT", "DELETE"}
	w.Header().Set("Access-Control-Allow-Methods", strings.Join(methods, ","))
	glog.Infof("preflight request for %s", r.URL.Path)
	return
}