models.rb

class ContactBook < ActiveRecord::Base
  has_many :contacts
  has_many :contacts_with_scope, ->(_contact_book) { desc }, class_name: "Contact", foreign_key: :contact_book_id
  has_many :employees, through: :contacts

  has_many :companies
  has_many :company_employees, through: :companies, source: :employees

  has_many :parents
  has_many :children, through: :parents

  has_many_aggregate :companies, :count, :count, "*"
  has_many_aggregate :companies, :count_with_max_ids_set, :count, "*", max_ids_per_query: 2
  has_many_aggregate :employees, :count, :count, "*"
  has_many_aggregate :company_employees, :count, :count, "*"
  has_many_aggregate :children, :count, :count, "*"

  has_many :companies_with_blank_email_address, -> { joins(:email_address).where(email_addresses: { address: "" }) }, class_name: "Company"
  has_many_aggregate :companies_with_blank_email_address, :count, :count, "*", table_alias_name: "contacts"
end

class Contact < ActiveRecord::Base
  belongs_to :contact_book
  belongs_to :contact_owner, polymorphic: true

  has_many :addresses
  has_many :phone_numbers
  has_one :email_address
  has_many :employees

  has_many_aggregate :addresses, :max_street_length, :maximum, "LENGTH(street)"
  has_many_aggregate :phone_numbers, :count, :count, "id"
  has_many_aggregate :addresses, :count, :count, "*"

  scope :desc, ->{ order(id: :desc) }
end

class Company < Contact
end

class Employee < Contact
  belongs_to :contact
end

class ParentsChild < ActiveRecord::Base
  belongs_to :parent
  belongs_to :child
end

class Parent < Contact
  has_many :parents_child
  has_many :children, through: :parents_child
end

class Child < Contact
  has_many :parents_child
  has_many :parents, through: :parents_child
end

class Address < ActiveRecord::Base
  belongs_to :contact
  belongs_to :country
end

class EmailAddress < ActiveRecord::Base
  belongs_to :contact
end

class PhoneNumber < ActiveRecord::Base
  belongs_to :contact
end

class Country < ActiveRecord::Base
  has_many :addresses
  has_many :contacts, through: :addresses
  has_many :contact_owners, through: :contacts, source_type: 'ContactOwner'
  has_many :states, primary_key: 'name', foreign_key: "region"

  has_many_aggregate :contacts, :count, :count, "*"
  has_many_aggregate :contact_owners, :count, :count, "*"
  has_many_aggregate :states, :count, :count, "*"
end

class State < ActiveRecord::Base
  belongs_to :country, foreign_key: 'region'
end

class ContactOwner < ActiveRecord::Base
  has_many :contacts, as: :contact_owner
  has_many :addresses, through: :contacts

  has_many_aggregate :contacts, :count, :count, "*"
  has_many_aggregate :addresses, :count, :count, "*"
end