Patch script for resources.pak of Google Chrome

to_patch.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

import os, re
from grit.format import data_pack

def to_patch(patch_rules):
    """ Patch for resources.pak file into part of Chrome browser
        patch_rules - Dictionary with meanings
            input_file - Path to input file (creates a backup)
            output_file - Path to output file (if already exists - auto renames)
            search_string - Search string (allows regex)
            act - One of the options is valid (lower case): append, prepend, replace, remove
            data - Data for change
    """
    # TODO: check exits input and output files
    data = data_pack.ReadDataPack(patch_rules['input_file'])
    # print(data.encoding)

    # PATCH PART
    for (resource_id, text) in data.resources.iteritems():
        # print('%s: %s' % (resource_id, len(text)))
        if re.search(patch_rules['search_string'], text):
            if patch_rules['act'] is 'append':
                data.resources[resource_id] = text + patch_rules['data']
            elif patch_rules['act'] is 'prepend':
                data.resources[resource_id] = patch_rules['data'] + text
            elif patch_rules['act'] is 'replace':
                data.resources[resource_id] = re.sub(patch_rules['search_string'], patch_rules['data'], text)
            elif patch_rules['act'] is 'remove':
                data.resources[resource_id] = re.sub(patch_rules['search_string'], '', text)
            print('In resource ID {} - {} - {} chars'.format(resource_id, patch_rules['act'], len(patch_rules['data'])))
            break

    # SAVE PART
    if not os.path.exists(patch_rules['output_file']):
        os.makedirs(patch_rules['output_file'])
    if patch_rules['input_file'] == patch_rules['output_file']:
        os.rename(patch_rules['input_file'], patch_rules['input_file']+'.bak')
    if os.path.exists(patch_rules['output_file']):
        i = 0
        while os.path.exists(patch_rules['output_file']):
            i += 1
            patch_rules['output_file'] = ''.join(patch_rules['output_file'].split('.')[:-1]) + \
                                         ' ('+i+')' + patch_rules['output_file'].split('.')[-1]

    data_pack.WriteDataPack(data.resources, patch_rules['output_file'], data.encoding)


if __name__ == '__main__':
    # example
    # Hides default icons of frequently visited sites
    # and shows them when you hover the cursor on NewTab (in Google Chrome, Chromium and etc. with original NewTab page)
    PATCH_RULES = {
        'input_file': 'resources.pak',
        'output_file': 'resources.pak',
        'search_string': '#mv-tiles',
        'act': 'append', # append, prepend, replace, remove
        'data': '''
            #mv-tiles {
              opacity: 0;
            }
            #mv-tiles:hover {
              opacity: 1;
            }
            ''',
    }

    to_patch(PATCH_RULES)

    ''' HOW USE IT
        $ git clone https://chromium.googlesource.com/chromium/src/tools/grit
        -> Move this file in grit folder and edit
        -> Move <Chrome-dir>/.../<version>/resources.pak file in grit folder
        $ cd grit
        $ python to_patch.py
        -> file resources.pak is patched! File resources.pak.bak - backup original resources.pak file
        -> Replace got file in dir <Chrome-dir>/.../<version>/
        -> End.

        /*  The MIT License
        Copyright (c) 2017 Vyacheslav Vasiliev (vyach.vasiliev\аt\gmail\dоt\com)
        Permission is hereby granted, free of charge, to any person obtaining a copy
        of this software and associated documentation files (the "Software"), to deal
        in the Software without restriction, including without limitation the rights
        to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
        copies of the Software, and to permit persons to whom the Software is
        furnished to do so, subject to the following conditions:
        The above copyright notice and this permission notice shall be included in
        all copies or substantial portions of the Software.
        THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
        IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
        FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
        AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
        LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
        OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
        THE SOFTWARE. */
    '''