module DaVinciPASTestKit::PASSubscriptionVerification

def verify_pas_subscription(subscription_json_str)
  assert_valid_json(subscription_json_str)
  subscription = JSON.parse(subscription_json_str)
  unless subscription['criteria'] == 'http://hl7.org/fhir/us/davinci-pas/SubscriptionTopic/PASSubscriptionTopic'
    add_message('error', %(
      The Subscription must use the PAS-defined Subscription topic
      `http://hl7.org/fhir/us/davinci-pas/SubscriptionTopic/PASSubscriptionTopic`
      in the `Subscription.criteria` element.
    ))
  end
  filter_criteria = subscription.dig('_criteria', 'extension')
    &.select do |ext|
      ext['url'] == 'http://hl7.org/fhir/uv/subscriptions-backport/StructureDefinition/backport-filter-criteria'
    end
  unless filter_criteria&.length == 1
    add_message('error', %(
        The Subscription must include a single filter on the submitting organization
        in the `Subscription.criteria.extension` element.
      ))
  end
  assert messages.none? { |msg| msg[:type] == 'error' },
         'The Subscription does not conform to PAS requirements - see messages for details.'
end