AppMessagingService.kt

class AppMessagingService : FirebaseMessagingService() {

    override fun onNewToken(token: String?) {
        val registrationId = token ?: return
        val userId = UUIDProvider.provide(this) // described later

        // request push registration
    }

    override fun onMessageReceived(remoteMessage: RemoteMessage) {
        super.onMessageReceived(remoteMessage)
        Log.i(TAG, "Message received.")

        AppCache.lockState = remoteMessage.getLockState()
        LockWidgetProvider.showLockState(this)
    }

    private fun RemoteMessage.getLockState(): LockState? {
        val json = data.get("state") ?: return null

        return LockState.fromJson(json)
    }

}