validate us canada phone number

string_extension.rb

class String

  def is_us_phone?
    !!(self.gsub(/\D/,'') =~/\A1?\d{10}\z/)
  end
  
  def to_us_phone
    return nil unless is_us_phone?
    s = self.gsub /\D/,''
    s[0,1]=='1' ? s[0,11] : '1'+s[0,10]
  end

  @@bad_phones = 0.upto(9).collect{|t| '1'+t.to_s*10} + ['11231231234', '1231231234']
  def is_bad_us_phone?
    return true unless is_us_phone?
    tmp_str = self.to_us_phone
    
    # This is according to http://en.wikipedia.org/wiki/North_American_Numbering_Plan
    return true unless tmp_str =~ /\A1[2-9][0-8]\d[2-9]\d{6}\z/ 
    
    # These are some numbers that are common fakes, although some are valid, e.g. 333-333-3333
    return true if @@bad_phones.include?(tmp_str)
    
    # Ficticious numbers and directory assistance
    return true if tmp_str =~ /55501\d{2}\z/ or tmp_str =~ /5551212\z/ or tmp_str =~/\A1555/
    
    false
  end
end