validates_email_format_of.rb

require "active_model"

# = EmailValidator
#
# Validates whether the value of the specified attribute is a valid email address.
# Borrowed from http://github.com/dancroak/validates_email_format_of and ported to Rails 3.
#
# ==== Example
#
#   class User
#     include ActiveModel::Validations
#     
#     attr_accessor :email
#     validate :email, :email => true
#   end
#
# ==== Options
#
#   [allow_nil]    Allow nil values (default is false)
#   [allow_blank]  Allow blank values (default is false)
#   [with]         Custom email format (you should stick to the default)
class EmailValidator < ActiveModel::EachValidator

  LocalPartSpecialChars = Regexp.escape('!#$%&\'*-/=?+-^_`{|}~')
  LocalPartUnquoted = '(([[:alnum:]' + LocalPartSpecialChars + ']+[\.\+]+))*[[:alnum:]' + LocalPartSpecialChars + '+]+'
  LocalPartQuoted = '\"(([[:alnum:]' + LocalPartSpecialChars + '\.\+]*|(\\\\[\u0001-\uFFFF]))*)\"'
  EmailFormat = Regexp.new('^((' + LocalPartUnquoted + ')|(' + LocalPartQuoted + ')+)@(((\w+\-+)|(\w+\.))*\w{1,63}\.[a-z]{2,6}$)', Regexp::EXTENDED | Regexp::IGNORECASE)

  def initialize(options)
    super
    
    defaults = { :allow_nil => false, :allow_blank => false, :with => EmailFormat }
    @options = defaults.merge options
  end

  def validate_each(record, attribute, value)
    value = value.to_s
    
    # local part max is 64 chars, domain part max is 255 chars
    # TODO: should this decode escaped entities before counting?
    begin
      domain, local = value.reverse.split("@", 2)
    rescue
      record.errors.add attribute, :invalid_email, :value => value
      next
    end
    
    unless value =~ options[:with] and not value =~ /\.\./ and domain.length <= 255 and local.length <= 64
      record.errors.add attribute, :invalid_email, :value => value
    end
  end

end