feat: bootstrap NAS music deduper

am_deduper/watcher.py

@@ -0,0 +1,57 @@
+from __future__ import annotations
+
+import time
+from pathlib import Path
+
+from watchdog.events import FileSystemEventHandler
+from watchdog.observers import Observer
+
+from .constants import MUSIC_EXTENSIONS, STABILITY_CHECKS, STABILITY_INTERVAL_SECONDS
+from .db import connect
+from .scanner import index_file
+
+
+class Handler(FileSystemEventHandler):
+    def __init__(self, root: Path, db_path: Path):
+        self.root = root
+        self.db_path = db_path
+
+    def _process(self, filename: str) -> None:
+        path = Path(filename)
+        if path.is_symlink() or path.suffix.lower() not in MUSIC_EXTENSIONS:
+            return
+        try:
+            previous = path.stat().st_size
+            stable = 0
+            while stable < STABILITY_CHECKS - 1:
+                time.sleep(STABILITY_INTERVAL_SECONDS)
+                size = path.stat().st_size
+                if size == previous:
+                    stable += 1
+                else:
+                    previous = size
+                    stable = 0
+            with connect(self.db_path) as conn:
+                index_file(conn, path)
+        except (FileNotFoundError, PermissionError):
+            return
+
+    def on_created(self, event):
+        if not event.is_directory:
+            self._process(event.src_path)
+
+    def on_moved(self, event):
+        if not event.is_directory:
+            self._process(event.dest_path)
+
+
+def watch(root: Path, db_path: Path) -> None:
+    observer = Observer()
+    observer.schedule(Handler(root, db_path), str(root), recursive=True)
+    observer.start()
+    try:
+        while True:
+            time.sleep(1)
+    finally:
+        observer.stop()
+        observer.join()