Simple CSS Selector Minifier

css-selector-minifier.rb

CHARS = [*'A'..'Z', *'a'..'z']

def index_to_shortcut(number, base = 52)
  quotient, remainder = number.divmod(base)

  if quotient.zero?
    CHARS[remainder]
  else
    index_to_shortcut(quotient - 1, base) + CHARS[remainder]
  end
end

def log_size(original, minified)
  original_size = File.size(original)
  minified_size = File.size(minified)
  ratio = (100.0 * (original_size - minified_size) / original_size).round(2)

  puts "#{original}"
  puts "\t#{(original_size / 1024.0).round(2)}KB ➔ #{(minified_size / 1024.0).round(2)}KB"
  puts "\t#{ratio}% compressed.\n\n"
end

def make_map(selectors, shortcuts)
  contents = ''

  selectors.each_with_index do |value, index|
    contents << "#{index + 1}\t#{shortcuts[index]}\t#{value}\n"
  end

  File.write('map.txt', contents)
end

selectors = []
shortcuts = []

html_files = ['lezhin.html']
css_path = File.join('./lezhin_files', '*.css')
css_files = Dir.glob(css_path)

css_files.each do |filename|
  simple_css= File.read(filename).gsub(/{[^}]+}/, '{}')
  candidates = simple_css.scan(/(?<=[#.])[a-z]{1}[a-z0-9\-_]*/i).reject{|selector| selector.size < 3}
  selectors.concat(candidates)
end

selectors.uniq!.sort_by!{|x| [-x.length, x]}

puts "#{selectors.size} selectors found.\n\n"

selectors.each_with_index do |value, index|
  shortcuts << index_to_shortcut(index)
end

html_files.each do |filename|
  contents = File.read(filename)
  contents.gsub!(/^\s+/, '').gsub!(/\r?\n/, '')

  selectors.each_with_index do |value, index|
    contents.gsub!(/(?<!<)#{value}/, shortcuts[index])
  end

  new_filename = filename.gsub(/\.html$/, '.min.html')
  File.write(new_filename, contents)

  log_size(filename, new_filename)
end

css_files.each do |filename|
  contents = File.read(filename)
  selectors.each_with_index do |value, index|
    contents.gsub!(/([#.]{1})#{value}/, '\1' + shortcuts[index])
  end

  new_filename = filename.gsub(/\.css$/, '.min.css')
  File.write(new_filename, contents)

  log_size(filename, new_filename)
end

make_map(selectors, shortcuts)