#!/usr/bin/env python3
import os
import sys
from pathlib import Path


def stat_follow(p: Path):
    try:
        return p.stat()  # follows symlinks
    except FileNotFoundError:
        return None


def lstat_nofollow(p: Path):
    try:
        return p.lstat()  # does not follow symlinks
    except FileNotFoundError:
        return None


def utime_nofollow(p: Path, t: float):
    try:
        os.utime(p, (t, t), follow_symlinks=False)
    except (NotImplementedError, PermissionError, FileNotFoundError):
        pass


def update_dir_mtime(path: Path, visited: set[tuple[int, int]]) -> float:
    st = stat_follow(path)
    if st is None:
        return 0.0

    key = (st.st_dev, st.st_ino)
    if key in visited:
        return st.st_mtime
    visited.add(key)

    if not path.is_dir():
        return st.st_mtime

    newest = 0.0

    for child in path.iterdir():
        child_st = stat_follow(child)
        if child_st is None:
            continue  # broken symlink or vanished entry -> ignore

        if child.is_dir():  # true also for symlink->dir when target exists
            child_mtime = update_dir_mtime(child, visited)
        else:
            child_mtime = child_st.st_mtime

        # NEW: if child is a symlink and target exists, update the symlink entry too
        if child.is_symlink():
            link_st = lstat_nofollow(child)
            if link_st is not None and child_mtime > link_st.st_mtime:
                utime_nofollow(child, child_mtime)

        if child_mtime > newest:
            newest = child_mtime

    # Update this directory to reflect newest reachable content
    if newest > 0.0 and newest > st.st_mtime:
        os.utime(path, (newest, newest))
        st = stat_follow(path) or st

    return max(newest, st.st_mtime)


if __name__ == "__main__":
    if len(sys.argv) != 2:
        print("Usage: fix_dir_mtime.py <directory>")
        raise SystemExit(1)

    root = Path(sys.argv[1]).resolve()
    update_dir_mtime(root, visited=set())