import datetime
import os
import os.path
import time

# os.scandir() Windows bug dir_entry.stat() not works on file during writing.
# Such files is for example application log.
# No problem with os.stat()

# Call of os.stat() before os.scandir() -> dir_entry.stat() is workaround.
# Open file during writing other program "fixes" dir_entry.stat().
# Get properties on open file during writing "fixes" dir_entry.stat().

# Notice that I run os.scandir() separately so dir_entry.stat() is not cached.

# Steps to reproduce lack of modification update:
# 1. Close all explorers or other application using PATH (it has impact).
# 2. Set PATH to test folder can be directory or windows share.
# 3. Run program without DO_STAT (False).
#
# Alternative steps (external app force valid modification date):
# 4. run 'touch' or 'echo' on file should "fix" problem. 'echo' will throw error not matter.
#
# Alternative scenario (os.stat() force valid modification date - very slow):
# 3. Run program without DO_STAT (True). No problems.
#
# Error result:
# Modification date from dir_entry.stat() is stalled (not changing after modification)
# if os.stat() or other Windows application not read file.
#
# Excepted result:
# Modification date from dir_entry.stat() is update from separate calls os.scandir()
# or cached if it is same os.scandir() call.
#
# Notice that os.scandir() must be call before dir_entry.stat() to avoid caching as described in documentation.
# And this is done but not work on files during writing..
#
# Ask question if you have since is very hard to find bug.

PATH = r'T:\\'
FILE_NAME = r'test.txt'

# PATH = r'\\nsdptrm01\d$\tmp'
# FILE_NAME = r'test.txt'

DO_STAT = True

def scan():
    with os.scandir(PATH) as dir_entries_iter:
        for dir_entry in dir_entries_iter:
            if dir_entry.path.endswith(FILE_NAME):
                stat_result = dir_entry.stat()
                print('dir_entry.stat()', dir_entry.path, stat_result.st_mtime,
                      'since last change', datetime.datetime.now().timestamp() - stat_result.st_mtime)
                if DO_STAT:
                    stat_result = os.stat(dir_entry.path)
                    print('os.stat()', dir_entry.path, stat_result.st_mtime)
                # mtime = os.path.getmtime(dir_entry.path)
                # size = os.path.getsize(dir_entry.path)
                # print('os.path', dir_entry.path, mtime, size)


with open(f'{PATH}\\{FILE_NAME}', 'w') as f:
    while True:
        scan()

        now = datetime.datetime.now()
        print(now, now.timestamp())
        f.write(str(now) + '\n')
        f.flush()
        time.sleep(1.0)