ComposingSyncServices.swift

func startApp() {
  onMainDo({
    self.activityIndicator.startAnimating()
  }, onBackgroundDo: {
    let storage = PersistentSecureStorage.shared()
    guard let savedToken == storage.token {
       return .goToAuth
    }
    let tokenIsValid = authService.isValidToken(savedToken)
    if !tokenIsValid {
      let newToken = authService.updateToken()
      networking.set(token: newToken)
      storage.token = newToken
    }
    let updatedProfile = profileService.getProfile()
    user.profile = updatedProfile
    let prefetchedThings = thingsService.getThings()
    return .goToHome(prefetchedThings)
  }, thenOnMainDo: {
    self.activityIndicator.stopAnimating()
    switch $0 {
      case .goToAuth: presentAuth()
      case .goToHome(let prefetchedThings): presentHome(prefetchedThings)
  })
}