FairCG JS character classification helper

js_parser_generator.rb

class CharClassData
  def initialize(char_classes)
    @switch_points = []
    @result_ccs = []
    
    prev_cc = nil
    max_ch = char_classes.flatten.max + 1
    (0..max_ch).each do |ch|
      next if prev_cc && char_classes[prev_cc].include?(ch)
      
      cc = char_classes.find_index {|g| g.include?(ch)}
      if prev_cc != cc
        @switch_points << ch
        @result_ccs << (cc || char_classes.length)
      end
      prev_cc = cc
    end
  end
  
  attr_reader :switch_points, :result_ccs
  
  def to_a
    other_cc = self.result_ccs.max
    [].tap do |result|
      cur_cc = other_cc
      cur_ch = 0
      self.result_ccs.zip(self.switch_points).each do |cc, ch_start|
        result.concat([cur_cc] * (ch_start - cur_ch))
        cur_cc = cc
        cur_ch = ch_start
      end
    end
  end
end