otp.rb

module Otp
  def send_otp
    result = sms_client.sms.send(
      from: 'Us',
      to: "+65#{mobile_number}",
      text: "Your one time password is #{otp}"
    )

    raise SomeError unless result.messages[0].status == '0'
  end

  def verify_otp(otp_to_verify)
    otp == otp_to_verify
  end

  private

  def otp
    Rails.cache.fetch("otp/#{cache_key}", expires_in: 3.minutes) do
      Array.new(6) { rand(10) }.join
    end
  end

  def sms_client
    @sms_client ||= Nexmo::Client.new(api_key: Rails.application.secrets.nexmo_api_key,
                                      api_secret: Rails.application.secrets.nexmo_secret)
  end
end