audio: add DeviceMonitor for device list polling

src/tuimble/audio.py

@@ -10,6 +10,8 @@ from __future__ import annotations
 import array
 import logging
 import queue
+import threading
+from typing import Callable
 
 log = logging.getLogger(__name__)
 
@@ -30,6 +32,60 @@ def _apply_gain(pcm: bytes, gain: float) -> bytes:
     return samples.tobytes()
 
 
+class DeviceMonitor:
+    """Poll sounddevice for device list changes.
+
+    Runs a daemon thread that compares a string fingerprint of
+    ``sounddevice.query_devices()`` against a cached snapshot every
+    *interval* seconds.  Fires *callback* when the list changes.
+
+    Uses ``threading.Event`` for cancellation (same pattern as
+    ``ReconnectManager``).
+    """
+
+    def __init__(self, callback: Callable[[], None], interval: float = 2.0):
+        self._callback = callback
+        self._interval = interval
+        self._cancel = threading.Event()
+        self._snapshot = self._device_fingerprint()
+        self._thread: threading.Thread | None = None
+
+    @staticmethod
+    def _device_fingerprint() -> str:
+        """Return a string snapshot of the current device list."""
+        try:
+            import sounddevice as sd
+
+            return str(sd.query_devices())
+        except Exception:
+            return ""
+
+    def start(self) -> None:
+        """Start polling in a daemon thread."""
+        if self._thread is not None and self._thread.is_alive():
+            return
+        self._cancel.clear()
+        self._snapshot = self._device_fingerprint()
+        self._thread = threading.Thread(target=self._poll, daemon=True)
+        self._thread.start()
+
+    def stop(self) -> None:
+        """Signal the poll loop to exit."""
+        self._cancel.set()
+        self._thread = None
+
+    def _poll(self) -> None:
+        while not self._cancel.wait(timeout=self._interval):
+            current = self._device_fingerprint()
+            if current != self._snapshot:
+                self._snapshot = current
+                log.info("audio device list changed")
+                try:
+                    self._callback()
+                except Exception:
+                    log.exception("device change callback failed")
+
+
 class AudioPipeline:
     """Manages audio input/output streams and Opus codec."""