func main()

in images/coturn-web/main.go [46:117]
57 lines of code
8 McCabe index (conditional complexity)

func main() {
	externalIP := popVarFromEnv("EXTERNAL_IP", true, "")
	turnPort := popVarFromEnv("TURN_PORT", false, "3478")
	sharedSecret := popVarFromEnv("TURN_SHARED_SECRET", true, "")
	listenPort := popVarFromEnv("PORT", false, "8080")
	authHeaderName := popVarFromEnv("AUTH_HEADER_NAME", false, "x-auth-user")

	// Env vars for running in aggregator mode.
	discoveryDNSName := popVarFromEnv("DISCOVERY_DNS_NAME", false, "")
	discoveryPortName := popVarFromEnv("DISCOVERY_PORT_NAME", false, "turn")

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {

		// Get user from auth header.
		user := r.Header.Get(authHeaderName)
		if len(user) == 0 {
			writeStatusResponse(w, http.StatusUnauthorized, fmt.Sprintf("Missing or invalid %s header", authHeaderName))
			return
		}
		// IAP uses a prefix of accounts.google.com:email, remove this to just get the email
		userToks := strings.Split(user, ":")
		user = userToks[len(userToks)-1]
		ips := make([]string, 0)

		if len(discoveryDNSName) == 0 {
			// Standard mode, use external IP to return single server.
			ips = []string{externalIP}
			resp, err := makeRTCConfig(ips, turnPort, user, sharedSecret)
			if err != nil {
				writeStatusResponse(w, http.StatusInternalServerError, "Internal server error")
				return
			}

			w.Header().Set("Content-Type", "application/json")
			w.WriteHeader(http.StatusOK)
			json.NewEncoder(w).Encode(resp)
		} else {
			// Aggregator mode, use DNS SRV records to build RTC config.
			// Fetch all service host and ports using SRV record of headless discovery service.
			// NOTE: The SRV record returns resolvable aliases to the endpoints, so do another lookup should return the IP.
			_, srvs, err := net.LookupSRV(discoveryPortName, "tcp", discoveryDNSName)
			if err != nil {
				log.Printf("ERROR: failed to query SRV record from %v %v: %v", discoveryDNSName, discoveryPortName, err)
				writeStatusResponse(w, http.StatusInternalServerError, "Internal server error")
				return
			}
			for _, srv := range srvs {
				addrs, err := net.LookupHost(srv.Target)
				if err != nil {
					log.Printf("ERROR: failed to query A record from %v: %v", srv.Target, err)
					writeStatusResponse(w, http.StatusInternalServerError, "Internal server error")
					return
				}
				ips = append(ips, addrs[0])
			}
		}

		resp, err := makeRTCConfig(ips, turnPort, user, sharedSecret)
		if err != nil {
			log.Printf("ERROR: failed to make RTC config: %v", err)
			writeStatusResponse(w, http.StatusInternalServerError, "Internal server error")
			return
		}

		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(resp)
	})

	log.Println(fmt.Sprintf("Listening on port %s", listenPort))
	http.ListenAndServe(fmt.Sprintf("0.0.0.0:%s", listenPort), nil)
}