# City:
# Custom Validation on external_id field which should be unique within customer
# name & state should be present for every record of city
class City < ActiveRecord::Base
  include ValidationHelper
  belongs_to :state
  belongs_to :customer
  validates_presence_of :name, :state
  validate -> { unique_prop_in_assoc('external_id', 'customer')  if external_id }
end

# Includes utility methods to apply validations on models
module ValidationHelper
  def unique_prop_in_assoc(prop, assoc)
    assoc_obj_id = method(assoc).call ? method(assoc).call.id : nil
    objects = self.class.where(prop.to_sym => method(prop).call,
              "#{assoc}_id" => assoc_obj_id).where.not(id: self.id)
    if objects.count > 0 && objects[0].has_attribute?(:is_deleted)
      objects = objects.where.not(is_deleted: true)
    end
    if objects.count > 0
      errors.add prop.to_sym, "of #{self.class.name} should be
      unique within #{assoc}"
    end
  end
end