io-watch-directory-recursive

Answer

The implementation uses raw Linux inotify via ctypes (zero external dependencies). Key design:

Recursive watching – on start(), os.walk() scans the root tree and adds an inotify watch for every directory. When IN_CREATE | IN_ISDIR fires, a watch is added for the new directory and any already-populated subdirectories (handles os.makedirs race).

Event detection – the event loop reads raw struct inotify_event records from the inotify fd and maps them to four user-facing types: created, modified, deleted, moved. MOVED_FROM/MOVED_TO pairs are matched by cookie to produce a single moved event.

Debouncing – a _Debouncer class collects events per-path. On each new event it resets a timer; when the timer fires (default 300ms quiet), the final event type is emitted. Merge rules: deleted always wins; created takes precedence over modified.

Thread safety – all debouncer state is protected by a lock. The inotify event loop runs in a daemon thread. stop() signals the loop, drains remaining events, and closes the fd.

import os, time, ctypes, threading, struct, errno

# ctypes bindings for inotify_init, inotify_add_watch, inotify_rm_watch, close
libc = ctypes.CDLL(ctypes.util.find_library("c"), use_errno=True)
_clib.inotify_init.restype = ctypes.c_int
# ... (see solution.py for full source)

class RecursiveDirWatcher:
    def __init__(self, root_dir, callback, debounce_interval=0.3): ...
    def start(self): ...
    def stop(self): ...