Fixup JSON dates exported by .NET JavaScriptSerializer

fix_json_dates.py

#!/usr/bin/env python3
# Updated 2025-06-02 by AfroThundr

'''
Fixup JSON dates exported by .NET JavaScriptSerializer

Example input file:

> $FormatEnumerationLimit = -1
> Get-ADUser -Filter * -Properties * |
>     ConvertTo-Json -Compress | Out-File AD_User.json
'''

from datetime import datetime as dt
from json import load, dump
from pathlib import Path
from re import search
from sys import argv, maxsize

from chardet import detect


def parse_netdate(obj: object, _: str = None, regex: str = None) -> object:
    '''Reads .NET JSON timestamps and returns ISO-8601 timestamps'''
    regex = regex or r'\/Date\((-?\d+)\)\/'
    if isinstance(obj, str) and (match := search(regex, obj)):
        return dt.fromtimestamp(
            int(match.groups()[0]) / 1000).strftime('%FT%TZ')
    if isinstance(obj, int) and 18 <= len(str(obj)) <= 19:
        if obj == maxsize:
            return 'Never'
        epoch1 = -int(dt.strptime('0001', "%Y").strftime('%s'))
        epoch2 = -int(dt.strptime('1601', "%Y").strftime('%s'))
        obj /= 10_000_000
        obj = obj - epoch1 if obj > epoch1 else obj - epoch2
        return dt.fromtimestamp(obj).strftime("%FT%TZ")
    return obj


def make_walker(func: callable) -> callable:
    '''Create a function that walks an object and calls a method on members'''
    def _walk(node: object, key: str = None) -> object:
        '''Walks an object and calls a method on members'''
        if isinstance(node, dict):
            return {k: _walk(v, k) for k, v in node.items()}
        if isinstance(node, list):
            return [_walk(v, key) for v in node]
        return func(node, key)
    return _walk


def fix_encoding(file: str, encoding: str = 'utf-8') -> None:
    '''Autodetect file encoding and convert to UTF-8'''
    with Path(file).open('rb') as f:
        detected=detect(f.read(20))['encoding']
    Path(file).write_text(
        Path(file).read_text(encoding=detected), encoding=encoding)


if __name__ == '__main__':
    for entry in argv[1:]:
        print('Processing:', entry)
        fix_encoding(entry)
        with open(entry, 'r+', encoding='utf-8') as f1, \
            open(entry, 'r', encoding='utf-8') as f2:
            dump(load(f2, object_hook=make_walker(parse_netdate)), f1, indent=2)