Active Model North American Telephone Number validator

nanp_validator.rb

# == Active Model North American Telephone Number Validator
# http://en.wikipedia.org/wiki/North_American_Numbering_Plan#Current_system
# [Author] Roger Rohrbach (roger@ecstatic.com)
class NanpValidator < ActiveModel::EachValidator  

  def self.matcher(require_area_code) # :nodoc:
    %r{
      (?<country_code>  \+1                         ){0}
      (?<trunk_prefix>  1                           ){0}
      (?<delimiter>     ([-\.]|\ +)                 ){0}
      (?<area_code>     [2-9]\d{2}                  ){0}
      (?<exchange>      [2-9]([02-9][0-9]|1[02-9])  ){0}
      (?<station>       \d{4}                       ){0}

      ^
      \ *
      ((\g<country_code>|\g<trunk_prefix>)\g<delimiter>{0,1})*
      (\(*\g<area_code>\)*){#{require_area_code ? '1' : '0,1'}}
      \g<delimiter>{0,1}
      \g<exchange>
      \g<delimiter>{0,1}
      \g<station>
      \ *
      $
    }x
  end

  private_class_method :matcher

  # <p><p>
  # Validates a telephone number in the North American Numbering Plan.
  # <p>
  # Example:
  # <p>
  #   class Person < ActiveRecord::Base
  #     validates :phone, :nanp => true
  #   end
  # <p><p>
  # Options:
  # <p>
  # * +require_area_code+ -
  #   consider number valid only if area code is present
  #   (default: +true+)
  #
  # * +allow_fictitious_numbers+ -
  #   allow numbers of the form 555-01<i>xx</i> or
  #   those with area code "958" (default: +false+)
  # <p><p>
  # e.g.:
  # <p>
  #   class Person < ActiveRecord::Base
  #     validates :phone, :nanp => {require_area_code: false}
  #   end
  def validate_each(record, attribute, value)
    match = self.class.send(
      :matcher,
      ({:require_area_code => true}.merge(options))[:require_area_code]
    ).match(value)

    if match
      if ["950", "958", "959", "976"].include?(match[:exchange])
        record.errors[attribute] << "is not a subscriber number"
      end

      # http://en.wikipedia.org/wiki/Fictitious_telephone_number
      unless options[:allow_fictitious_numbers]
        if match[:area_code] == "958" ||
          (match[:exchange] == "555" && match[:station] =~ /^01\d{2}$/)

            record.errors[attribute] << "is fictitious"
        end
      end
    else
      record.errors[attribute] << "is not valid"
    end
  end
end