feat: add miband bot application

miband_tracker/lock.py

@@ -0,0 +1,31 @@
+from __future__ import annotations
+
+import fcntl
+import os
+import time
+from collections.abc import Iterator
+from contextlib import contextmanager
+from pathlib import Path
+
+
+class LockUnavailable(RuntimeError):
+    """Raised when another process already owns the sync lock."""
+
+
+@contextmanager
+def exclusive_file_lock(path: Path) -> Iterator[None]:
+    path.parent.mkdir(parents=True, exist_ok=True)
+    with path.open("a+", encoding="utf-8") as lock_file:
+        try:
+            fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
+        except BlockingIOError as exc:
+            raise LockUnavailable(f"Lock is already held: {path}") from exc
+
+        try:
+            lock_file.seek(0)
+            lock_file.truncate()
+            lock_file.write(f"pid={os.getpid()} time={int(time.time())}\n")
+            lock_file.flush()
+            yield
+        finally:
+            fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)