[QUIZ] Fiddle with regular expressions (#2)

quiz-fiddle-with-regular-expressions.rb

#= part 1

reg =
/^
  [\w!#\$%&'*+\/=?`{|}~^-]+           # 1 or more glyph of: underscore alphabetic letters and symbols choosed from !#\$%&'*+\/=?`{|}~^- 
                                      # followed by
  (?:\.                               # a non-catching block wich has to begin with a dot followed by
    [\w!#\$%&'*+\/=?`{|}~^-]+         #   1 or more gliyp of the same class of line 3.
  )*                                  # this block can apper 0 or more times.
  @                                   # followed by an 'at' sign
  (?:                                 # followed by a non-catching block containing
    [a-zA-Z0-9-]+                     # a sequence of 1 or more lowercase or uppercase alphanumeric chars
  \.)+                                # ending with a dot. The whole block has to be present 1 ore more times in the string
                                      # followed by
  [a-zA-Z]{2,6}                       # 2 to 6 chars of lowercase or uppercase alphabetic chars
  
  $/x

puts 'jd@example.com'[reg] # => jd@example.com
puts 'jd@example.tooolong'[reg] # => nil
puts 'j*d@example.com'[reg] # => j*d@example.com
puts 'john.doe@example.com.INFO'[reg] # => john.doe@example.com.INFO
puts 'jd.@example.com'[reg] # => nil

#= part 2

reg_w_named_refs = /^
  (?<username_token>   [\w!#\$%&'*+\/=?`{|}~^-]+    ){0} 
  (?<domain_token>     [a-zA-Z0-9-]+                ){0} 
  (?<ext_token>        [a-zA-Z]{2,6}                ){0} 

  \g<username_token>(?:\.\g<username_token>)*@(?:\g<domain_token>\.)+\g<ext_token>

$/x

puts 'jd@example.com'[reg_w_named_refs] # => jd@example.com
puts 'jd@example.tooolong'[reg_w_named_refs] # => nil
puts 'j*d@example.com'[reg_w_named_refs] # => j*d@example.com
puts 'john.doe@example.com.INFO'[reg_w_named_refs] # => john.doe@example.com.INFO
puts 'jd.@example.com'[reg_w_named_refs] # => nil

#= part 3

reg_anti_evil_hacker = 
/\A                                  
  [\w!#\$%&'*+\/=?`{|}~^-]+          
                                     
  (?:\.                              
    [\w!#\$%&'*+\/=?`{|}~^-]+        
  )*                                 
  @                                  
  (?:                                
    [a-zA-Z0-9-]+                    
  \.)+                               
                                     
  [a-zA-Z]{2,6}                      
                                     
  \Z/x
  
puts "<script>alert('boo');</script>\nevil@hacker.com"[reg] # =>evil@hacker.com
puts "<script>alert('boo');</script>\nevil@hacker.com"[reg_anti_evil_hacker] # =>nil

#= part 4

def encrypt(string)
  string.gsub(/([[:alnum:]])/){|m|m.next}
end

puts encrypt("this is a test") # => uijt jt b uftu