auth.go

package main

import (
	"fmt"
	"log"
	"net/http"
	"strings"

	"github.com/stretchr/gomniauth"
	"github.com/stretchr/objx"
)

type authHandler struct {
	next http.Handler
}

func (h *authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if _, err := r.Cookie("auth"); err == http.ErrNoCookie {
		// not authenticated
		w.Header().Set("Location", "/login")
		w.WriteHeader(http.StatusTemporaryRedirect)
	} else if err != nil {
		// some other error
		panic(err.Error())
	} else {
		// success - call the next handler
		h.next.ServeHTTP(w, r)
	}
}

// MustAuth ensures that only authenticated user may have access to the chat
// uses decorator pattern
func MustAuth(handler http.Handler) http.Handler {
	return &authHandler{next: handler}
}

// loginHandler handles the third-party login process.
// format: /auth/{action}/{provider}
func loginHandler(w http.ResponseWriter, r *http.Request) {
	segs := strings.Split(r.URL.Path, "/")
	var action string
	var provider string
	if len(segs) > 2 {
		action = segs[2]
		provider = segs[3]
	}

	switch action {
	case "login":
		provider, err := gomniauth.Provider(provider)
		if err != nil {
			log.Fatalln("Error when trying to get provider", provider, "-", err)
		}
		loginURL, err := provider.GetBeginAuthURL(nil, nil)
		if err != nil {
			log.Fatalln("Error when trying to GetBeginAuthURL for", provider, "-", err)
		}
		w.Header().Set("Location", loginURL)
		w.WriteHeader(http.StatusTemporaryRedirect)
	case "callback":
		provider, err := gomniauth.Provider(provider)
		if err != nil {
			log.Fatalln("Error when trying to get provider", provider, "-", err)
		}
		creds, err := provider.CompleteAuth(objx.MustFromURLQuery(r.URL.RawQuery))
		if err != nil {
			log.Fatalln("Error when trying to complete auth for", provider, "-", err)
		}
		user, err := provider.GetUser(creds)
		if err != nil {
			log.Fatalln("Error when trying to get user from", provider, "-", err)
		}
		authCookieValue := objx.New(map[string]interface{}{
			"name": user.Name(),
		}).MustBase64()
		http.SetCookie(w, &http.Cookie{
			Name:  "auth",
			Value: authCookieValue,
			Path:  "/"})
		w.Header()["Location"] = []string{"/chat"}
		w.WriteHeader(http.StatusTemporaryRedirect)
	default:
		w.WriteHeader(http.StatusNotFound)
		fmt.Fprintf(w, "Auth action %s not supported", action)
	}
}