ANSI Escape Sequences

ansi_seq.rb

class String
   def seq
      gsub(%r{
         %% |
         % (?<bg> B )? (?<sgr> black|red|green|yellow|blue|magenta|cyan|white|[0bu!_]|clr ) |
         % (?<n1> \d+ )? (?<c> [\^v><\|\-!fb]<? ) (?<n2> \d+ )?
      }x) {
         match, bg, sgr, n1, c, n2 = *$~
         
         if sgr   #Select Graphic Rendition (reset, bold, underline, negative, colors) TODO: xterm colors
            next "\e[2J" if sgr == 'clr'
            
            n = {
               ?0 => 0,
               ?b => 1, ?u => 4, ?_ => 4, ?! => 7,
               'black' => 30, 'red' => 31, 'green' => 32, 'yellow' => 33, 'blue' => 34, 'magenta' => 35, 'cyan' => 36, 'white' => 37
            }[sgr]
            
            n += 10 if bg and n >= 30
            
            "\e[#{n}m"
         elsif c   #Other codes (cursor movement) and colors
            codes = {
               ?^ => ?A, ?v => ?B, ?> => ?C, ?< => ?D,
               'v<' => ?E, '^<' => ?F,
               ?| => ?G
            }
            
            if c == ?f   #Foreground
               "\e[#{30 + n1.to_i}m"
            elsif c == ?b   #Background
               "\e[#{40 + n1.to_i}m"
            elsif n2   #Set cursor position
               "\e[#{n1 || 1};#{n2}H"
            else   #Other codes
               "\e[#{n1 || 0}#{codes[c]}"
            end
         else
            ?%
         end
      }
   end	
end