invert_policy_provders.rb

require 'active_support/all'

module UnderwritingService
  extend self
  PolicyMeta = Struct.new(:product_type, :public_id, :status)

  def policies_metas(user_id:)
    UserPoliciesRegistry.all.flat_map do |provider|
      provider.of_user(user_id:user_id).map { |policy|
        PolicyMeta.new(provider.product_type, provider.public_id(policy), provider.status(policy))
      }
    end
  end

  def fetch_policies(product:, public_ids:)
    UserPoliciesRegistry.for_product(product).fetch(public_ids)
  end
  
end

module UserPoliciesRegistry
  extend self

  def register(provider)
    @providers ||= {}
    @providers[provider.product_type] = provider
  end

  def all
    @providers.values
  end

  def for_product(product_type)
    @providers[product_type]
  end
end

module UserPoliciesProvider
  extend ::ActiveSupport::Concern

  included do
    UserPoliciesRegistry.register(self)
  end
end

module PetUserPolicies
  extend self
  
  def product_type
    :pet
  end
  
  include UserPoliciesProvider
  
  def of_user(user_id:)
    [{id:2}]
  end

  def fetch(ids:)
    []
  end

  def public_id(policy)
    '1'
  end

  def status(policy)
    true
  end
end

metas = UnderwritingService.policies_metas(user_id: 2)
p metas