sequential.rb

module Sequential
  extend ActiveSupport::Concern

  module ClassMethods

    def next_custom_id_for_tenant(tenant_id)
      raise "Tenant is required" unless tenant_id.present?

      # FIXME: Should probably store this value in some external resource, as this could cause race conditions and/or performance issues due to transaction locking.
      # Possibly use PG Triggers?
      max_id = max_custom_id_for_tenant(tenant_id)
      return max_id.to_i + 1
    end

    def max_custom_id_for_tenant(tenant_id)
      unscoped.where(tenant_id: tenant_id).maximum('custom_id')
    end
  end

  included do
    validates :tenant, presence: true
    before_validation :set_tenant_id, on: :create
    before_validation :set_custom_id, on: :create
    validates_uniqueness_of :custom_id, scope: :tenant
    scope :by_custom_id, -> { order(:custom_id) }

  end

  def to_param
    custom_id.to_s
  end

  private

  def set_custom_id
    self.custom_id = self.class.next_custom_id_for_tenant(tenant_id)
  end

  def set_tenant_id
    self.tenant_id ||= Tenant.current_id
  end

end