Replace SSL certificates in all files and keep indentation

replacer.py

#!/usr/bin/env python3

# vim: fileencoding=utf-8 tw=100 expandtab ts=4 sw=4 :
#
# ssh_replacer
# (c) 2015 ActivKonnect

from sys import argv, exit, stderr
from re import compile
from os import walk, path
import json


WHITESPACE_RE = compile(r'^([ \t]*)([^\r\n]*)([\r\n]*)')


class IndentedString(str):
    def __new__(cls, obj, *args, **kwargs):
        real_str = str(obj)

        m = WHITESPACE_RE.match(real_str)

        clean_str = super(IndentedString, cls).__new__(cls, m.group(2), *args, **kwargs)
        clean_str.real_str = real_str
        clean_str.indent = m.group(1)
        clean_str.eol = m.group(3)

        return clean_str


def read_file(file_name):
    with open(file_name) as f:
        return [IndentedString(x) for x in f.readlines()]


def list_files(dir_name):
    if path.isdir(dir_name):
        for root, dirs, files in walk(dir_name):
            for file_name in sorted(files):
                yield path.join(root, file_name)
    else:
        yield dir_name


def find(haystack, needle):
    progress = 0

    for i, line in enumerate(haystack):
        if line == needle[progress]:
            progress += 1
        else:
            progress = 0

        if progress == len(needle):
            return i - progress + 1


def replace(src, old, new):
    pos = find(src, old)

    if pos is not None:
        indent = src[pos].indent
        eol = src[pos].eol
        last_eol = src[pos + len(old) - 1].eol

        formatted_new = [indent + x + (eol if i != len(new) - 1 else last_eol)
                         for i, x in enumerate(new)]

        return True, src[0:pos] + formatted_new + src[pos + len(old):]
    else:
        return False, src


def get_real_str(string):
    return getattr(string, 'real_str', string)


def main(target_dir, old, new):
    old_f = read_file(old)
    new_f = read_file(new)

    for file_name in list_files(target_dir):
        try:
            file_content = read_file(file_name)
            replaced, new_content = replace(file_content, old_f, new_f)

            if replaced:
                print('### {}'.format(file_name))

                with open(file_name, 'w') as f:
                    f.write(''.join(get_real_str(x) for x in new_content))
        except UnicodeDecodeError:
            pass


if __name__ == '__main__':
    if len(argv) != 4:
        print('Usage: python3 {} <target_dir> <old> <new>'.format(argv[0]), file=stderr)
        exit(1)

    main(*argv[1:])