tools/grit/minimize_css.py

#!/usr/bin/env python
# Copyright 2016 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import re
import sys

class CSSMinimizer(object):

  INITIAL = 0
  MAYBE_COMMENT_START = 1
  INSIDE_COMMENT = 2
  MAYBE_COMMENT_END = 3
  INSIDE_SINGLE_QUOTE = 4
  INSIDE_SINGLE_QUOTE_ESCAPE = 5
  INSIDE_DOUBLE_QUOTE = 6
  INSIDE_DOUBLE_QUOTE_ESCAPE = 7

  def __init__(self):
    self._output = ''
    self._codeblock = ''

  def flush_codeblock(self):
    stripped = re.sub(r"\s+", ' ', self._codeblock)
    stripped = re.sub(r";?\s*(?P<op>[{};])\s*", r'\g<op>', stripped)
    self._output += stripped
    self._codeblock = ''

  def parse(self, content):
    state = self.INITIAL
    for char in content:
      if state == self.INITIAL:
        if char == '/':
          state = self.MAYBE_COMMENT_START
        elif char == "'":
          self.flush_codeblock()
          self._output += char
          state = self.INSIDE_SINGLE_QUOTE
        elif char == '"':
          self.flush_codeblock()
          self._output += char
          state = self.INSIDE_DOUBLE_QUOTE
        else:
          self._codeblock += char
      elif state == self.MAYBE_COMMENT_START:
        if char == '*':
          self.flush_codeblock()
          state = self.INSIDE_COMMENT
        else:
          self._codeblock += '/' + char
          state = self.INITIAL
      elif state == self.INSIDE_COMMENT:
        if char == '*':
          state = self.MAYBE_COMMENT_END
        else:
          pass
      elif state == self.MAYBE_COMMENT_END:
        if char == '/':
          state = self.INITIAL
        else:
          state = self.INSIDE_COMMENT
      elif state == self.INSIDE_SINGLE_QUOTE:
        if char == '\\':
          self._output += char
          state = self.INSIDE_SINGLE_QUOTE_ESCAPE
        elif char == "'":
          self._output += char
          state = self.INITIAL
        else:
          self._output += char
      elif state == self.INSIDE_SINGLE_QUOTE_ESCAPE:
        self._output += char
        state = self.INSIDE_SINGLE_QUOTE
      elif state == self.INSIDE_DOUBLE_QUOTE:
        if char == '\\':
          self._output += char
          state = self.INSIDE_DOUBLE_QUOTE_ESCAPE
        elif char == '"':
          self._output += char
          state = self.INITIAL
        else:
          self._output += char
      elif state == self.INSIDE_DOUBLE_QUOTE_ESCAPE:
        self._output += char
        state = self.INSIDE_DOUBLE_QUOTE

    self.flush_codeblock()
    self._output = self._output.strip()
    return self._output

  @classmethod
  def minimize_css(cls, content):
    minimizer = CSSMinimizer()
    return minimizer.parse(content)

def main():
  result = ''
  try:
    result = CSSMinimizer.minimize_css(sys.stdin.read())
  finally:
    print(result)

if __name__ == '__main__':
  main()