Add Sync Source sensor to Room State device

Exposes the configured sync mode (manual/caldav/api) as a sensor value,
with server_url as an attribute populated from caldav_url or api_base_url.

custom_components/room_cal_ha/sensor.py

@@ -11,10 +11,14 @@ from homeassistant.helpers.entity_platform import AddEntitiesCallback
 from homeassistant.helpers.update_coordinator import CoordinatorEntity
 
 from .const import (
+  CONF_API_BASE_URL,
+  CONF_CALDAV_URL,
   CONF_ROOM_NAME,
+  CONF_SYNC_MODE,
   DOMAIN,
   STORE_CURRENT,
   STORE_NEXT,
+  SYNC_MODE_MANUAL,
 )
 from .coordinator import CoordinatorData, RoomCalCoordinator
 from .models import ReservationData
@@ -29,7 +33,9 @@ async def async_setup_entry(
 
   room_name = entry.data.get(CONF_ROOM_NAME, entry.title)
 
-  entities: list[SensorEntity] = []
+  entities: list[SensorEntity] = [
+    SyncSourceSensor(entry, room_name),
+  ]
 
   for slot, device_name in (
     (STORE_CURRENT, f"{room_name} Current"),
@@ -55,6 +61,35 @@ async def async_setup_entry(
   async_add_entities(entities)
 
 
+class SyncSourceSensor(SensorEntity):
+  _attr_has_entity_name = True
+  _attr_name = "Sync Source"
+  _attr_icon = "mdi:sync"
+
+  def __init__(self, entry: ConfigEntry, room_name: str) -> None:
+    self._entry = entry
+    self._attr_unique_id = f"{entry.entry_id}_sync_source"
+    self._attr_device_info = DeviceInfo(
+      identifiers={(DOMAIN, f"{entry.entry_id}_room_state")},
+      name=f"{room_name} Room State",
+    )
+
+  @property
+  def native_value(self) -> str:
+    return self._entry.options.get(CONF_SYNC_MODE, SYNC_MODE_MANUAL)
+
+  @property
+  def extra_state_attributes(self) -> dict[str, str | None]:
+    mode = self._entry.options.get(CONF_SYNC_MODE, SYNC_MODE_MANUAL)
+    if mode == "caldav":
+      url = self._entry.options.get(CONF_CALDAV_URL)
+    elif mode == "api":
+      url = self._entry.options.get(CONF_API_BASE_URL)
+    else:
+      url = None
+    return {"server_url": url}
+
+
 class _ReservationSensor(CoordinatorEntity[RoomCalCoordinator], SensorEntity):
   _attr_has_entity_name = True