# encoding: utf-8

module Okei

  # Stores and validates units of measure.
  #
  # Attributes:
  # +uuids+:: list of Units::Uuid objects assigned (referred to) the unit.
  # +code+::  literal cyrillic code ("КМ/Ч").
  # +name+::  name of the unit ("Километры в час").
  # +num+::   numeric code of the unit following the OKEI ("007").
  # +int_code+:: a literal international code of the unit ("KMH").
  # +base+:: literal cyrillic code of the basic unit of measure ("М/С").
  # +factor+:: float number of basic units in a current unit (0.28).
  # +measure+:: the name of measurement ("СКОРОСТЬ") used for filtering units.
  #
  # Methods:
  # <tt>#uuid</tt>:: returns value of the first +uuids+ assigned to the unit.
  # <tt>.by_uuid(value)</tt>:: selects units by a given UUID.
  #
  # The first UUID can be set manually if necessary (when db populated from the
  # outer list). Otherwise it will be assigned by default on the unit creation.
  #
  # @example
  #     unit = Unit.new(
  #       name: "Километры в час", code: "КМ/Ч", num: "007", int_code: "KMH",
  #       base: "М/С", factor: 0.28, measure: "СКОРОСТЬ"
  #     )
  #     # this can be skipped:
  #     unit.uuids.new value: "9ac7e74a-d51a-424c-8fcd-71b0b55f6658"
  #
  class Unit < ActiveRecord::Base
    include Uuids::Base

    # Format of OKEI numeric codes (three digits).
    NUM_FORMAT  = /\A\d{3}\z/

    has_uuids
    validates :code, :name, :base, :factor, :measure, presence: true
    validates :code, :name, uniqueness: true, allow_nil: true
    validates :factor, allow_nil: true, numericality: { greater_than: 0.0 }
    validates :num,    allow_nil: true, format: { with: NUM_FORMAT }
  end
end