auth.go

package main

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

	"github.com/stretchr/objx"

	"github.com/stretchr/gomniauth"
)

type authHandler struct {
	next http.Handler
}

func (h *authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	cookie, err := r.Cookie("nexus-auth")
	if err == http.ErrNoCookie || cookie.Value == "" {
		w.Header().Set("Location", "/login")
		w.WriteHeader(http.StatusTemporaryRedirect)
		return
	}

	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	h.next.ServeHTTP(w, r)
}

func MustAuth(handler http.Handler) http.Handler {
	return &authHandler{next: handler}
}

// loginHandler handles 3P logins
// format: /auth/action/provider
func loginHandler(w http.ResponseWriter, r *http.Request) {
	segments := strings.Split(r.URL.Path, "/")
	action := segments[2]
	provider := segments[3]
	switch action {
	case "login":
		provider, err := gomniauth.Provider(provider)
		if err != nil {
			http.Error(w, fmt.Sprintf("Error when trying to get provider %s: %s", provider, err),
				http.StatusBadRequest)
			return
		}
		loginUrl, err := provider.GetBeginAuthURL(nil, nil)
		if err != nil {
			http.Error(w, fmt.Sprintf("Error when trying to GetBeginAuthURL for %s: %s", provider, err),
				http.StatusInternalServerError)
			return
		}
		w.Header().Set("Location", loginUrl)
		w.WriteHeader(http.StatusTemporaryRedirect)
	case "callback":
		provider, err := gomniauth.Provider(provider)
		if err != nil {
			http.Error(w, fmt.Sprintf("Error when trying to get provider %s: %s", provider, err),
				http.StatusBadRequest)
			return
		}
		creds, err := provider.CompleteAuth(objx.MustFromURLQuery(r.URL.RawQuery))
		if err != nil {
			http.Error(w, fmt.Sprintf("Error when trying to finish auth for %s: %s", provider, err),
				http.StatusInternalServerError)
			return
		}
		user, err := provider.GetUser(creds)
		if err != nil {
			http.Error(w, fmt.Sprintf("Error when trying to get user from %s: %s", provider, err),
				http.StatusInternalServerError)
			return
		}
		authCookieValue := objx.New(map[string]interface{}{
			"name":       user.Name(),
			"avatar_url": user.AvatarURL(),
		}).MustBase64()
		http.SetCookie(w, &http.Cookie{
			Name:  "nexus-auth",
			Value: authCookieValue,
			Path:  "/",
		})
		w.Header().Set("Location", "/chat")
		w.WriteHeader(http.StatusTemporaryRedirect)
	default:
		w.WriteHeader(http.StatusNotFound)
		fmt.Fprintf(w, "auth action %s not supported", action)
	}
}