EmailExclusionValidator

gistfile1.rb

class EmailExclusionValidator < ActiveModel::EachValidator
  
  def validate_each(record, attribute, value)
    unless value =~ email_regex
      record.errors[attribute] << (options[:message] || "is not an email")
    else 
      user_name = value.split('@').first 
      if forbidden_words.include?(user_name) 
        record.errors[attribute] << (options[:message] || "you cannot register with a user name")
      end 
    end
    
  end

  private
  
  def forbidden_words 
    %w(admin)
  end 
  
  def email_name_regex
    '[\w\.%\+\-]+'
  end

  def domain_head_regex
    '(?:[A-Z0-9\-]+\.)+'
  end

  def domain_tld_regex
    '(?:[A-Z]{2}|com|org|net|edu|gov|mil|biz|info|mobi|name|aero|jobs|museum)'
  end

  def email_regex
    /\A#{email_name_regex}@#{domain_head_regex}#{domain_tld_regex}\z/i
  end
end