baclight/app/models/id_card/exception_item.rb

class IdCard::ExceptionItem < ApplicationRecord
    belongs_to :id_card_exception
    belongs_to :id_card_network_logo, optional: true
    belongs_to :id_card_provider_section, optional: true

    validate :only_one_exception_field_present

    FIELDS_TO_VALIDATE = [:field_value, :card_logo_file_id, :card_provider_id].freeze

    VALID_FIELD_NAMES = ['network_logo', 'provider_section', 'effective_date']

    validates :field_name, inclusion: { in: VALID_FIELD_NAMES,
                                    message: "%{value} is not a valid Id Card Field Name" }


    private

    def only_one_exception_field_present
        present_fields = FIELDS_TO_VALIDATE.count { |field| self[field].present? }

        if present_fields != 1
            errors.add(:base, "Only one exception field can be present at a time")
        end
    end
end