Add stale binary sensor to Room State device

Reports on when either slot's last_refresh timestamp exceeds 2x the
configured refresh interval. Unavailable in manual sync mode.

custom_components/room_cal_ha/__init__.py

@@ -10,7 +10,7 @@ from homeassistant.helpers import config_validation as cv
 from .const import DOMAIN, SENSOR_KEYS, STORE_CURRENT, STORE_NEXT
 from .coordinator import RoomCalCoordinator
 
-PLATFORMS = [Platform.SENSOR, Platform.SWITCH, Platform.BUTTON]
+PLATFORMS = [Platform.BINARY_SENSOR, Platform.SENSOR, Platform.SWITCH, Platform.BUTTON]
 
 UPDATE_RESERVATION_SCHEMA = vol.Schema({
   vol.Required("target"): vol.In([STORE_CURRENT, STORE_NEXT]),

custom_components/room_cal_ha/binary_sensor.py

@@ -0,0 +1,68 @@
+from __future__ import annotations
+
+from datetime import timedelta
+
+from homeassistant.components.binary_sensor import BinarySensorEntity
+from homeassistant.config_entries import ConfigEntry
+from homeassistant.core import HomeAssistant
+from homeassistant.helpers.device_registry import DeviceInfo
+from homeassistant.helpers.entity_platform import AddEntitiesCallback
+from homeassistant.helpers.update_coordinator import CoordinatorEntity
+from homeassistant.util import dt as dt_util
+
+from .const import (
+  CONF_REFRESH_INTERVAL,
+  CONF_ROOM_NAME,
+  CONF_SYNC_MODE,
+  DEFAULT_REFRESH_INTERVAL,
+  DOMAIN,
+  SYNC_MODE_MANUAL,
+)
+from .coordinator import CoordinatorData, RoomCalCoordinator
+
+
+async def async_setup_entry(
+  hass: HomeAssistant,
+  entry: ConfigEntry,
+  async_add_entities: AddEntitiesCallback,
+) -> None:
+  coordinator: RoomCalCoordinator = hass.data[DOMAIN][entry.entry_id]["coordinator"]
+  device_name = f"{entry.data.get(CONF_ROOM_NAME, entry.title)} Room State"
+  device_info = DeviceInfo(
+    identifiers={(DOMAIN, f"{entry.entry_id}_room_state")},
+    name=device_name,
+  )
+  async_add_entities([StaleSensor(coordinator, entry, device_info)])
+
+
+class StaleSensor(CoordinatorEntity[RoomCalCoordinator], BinarySensorEntity):
+  _attr_has_entity_name = True
+  _attr_name = "Stale"
+  _attr_icon = "mdi:clock-alert-outline"
+
+  def __init__(
+    self,
+    coordinator: RoomCalCoordinator,
+    entry: ConfigEntry,
+    device_info: DeviceInfo,
+  ) -> None:
+    super().__init__(coordinator)
+    self._entry = entry
+    self._attr_unique_id = f"{entry.entry_id}_stale"
+    self._attr_device_info = device_info
+
+  @property
+  def is_on(self) -> bool | None:
+    if self._entry.options.get(CONF_SYNC_MODE, SYNC_MODE_MANUAL) == SYNC_MODE_MANUAL:
+      return None
+
+    interval = self._entry.options.get(CONF_REFRESH_INTERVAL, DEFAULT_REFRESH_INTERVAL)
+    threshold = timedelta(minutes=interval * 2)
+    now = dt_util.utcnow()
+    data: CoordinatorData = self.coordinator.data
+
+    for ts in (data.current_last_refresh, data.next_last_refresh):
+      if ts is None or (now - ts) > threshold:
+        return True
+
+    return False