Add sensor when meter last sent its data to Discovergy (#97223)

* Add sensor for last reading by Discovergy

* Rename sensor to make it clear what it actually is

* Revert back to single sensor classe and extend entity_description with a value function

homeassistant/components/discovergy/sensor.py

@@ -1,7 +1,9 @@
 """Discovergy sensor entity."""
+from collections.abc import Callable
 from dataclasses import dataclass, field
+from datetime import datetime
 
-from pydiscovergy.models import Meter
+from pydiscovergy.models import Meter, Reading
 
 from homeassistant.components.sensor import (
     SensorDeviceClass,
@@ -11,6 +13,7 @@ from homeassistant.components.sensor import (
 )
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.const import (
+    EntityCategory,
     UnitOfElectricPotential,
     UnitOfEnergy,
     UnitOfPower,
@@ -19,7 +22,6 @@ from homeassistant.const import (
 from homeassistant.core import HomeAssistant
 from homeassistant.helpers.device_registry import DeviceInfo
 from homeassistant.helpers.entity_platform import AddEntitiesCallback
-from homeassistant.helpers.typing import StateType
 from homeassistant.helpers.update_coordinator import CoordinatorEntity
 
 from . import DiscovergyData, DiscovergyUpdateCoordinator
@@ -32,6 +34,9 @@ PARALLEL_UPDATES = 1
 class DiscovergyMixin:
     """Mixin for alternative keys."""
 
+    value_fn: Callable[[Reading, str, int], datetime | float | None] = field(
+        default=lambda reading, key, scale: float(reading.values[key] / scale)
+    )
     alternative_keys: list[str] = field(default_factory=lambda: [])
     scale: int = field(default_factory=lambda: 1000)
 
@@ -144,6 +149,17 @@ ELECTRICITY_SENSORS: tuple[DiscovergySensorEntityDescription, ...] = (
     ),
 )
 
+ADDITIONAL_SENSORS: tuple[DiscovergySensorEntityDescription, ...] = (
+    DiscovergySensorEntityDescription(
+        key="last_transmitted",
+        translation_key="last_transmitted",
+        device_class=SensorDeviceClass.TIMESTAMP,
+        entity_category=EntityCategory.DIAGNOSTIC,
+        entity_registry_enabled_default=False,
+        value_fn=lambda reading, key, scale: reading.time_with_timezone,
+    ),
+)
+
 
 async def async_setup_entry(
     hass: HomeAssistant, entry: ConfigEntry, async_add_entities: AddEntitiesCallback
@@ -160,18 +176,22 @@ async def async_setup_entry(
         elif meter.measurement_type == "GAS":
             sensors = GAS_SENSORS
 
+        coordinator: DiscovergyUpdateCoordinator = data.coordinators[meter.meter_id]
+
         if sensors is not None:
             for description in sensors:
                 # check if this meter has this data, then add this sensor
                 for key in {description.key, *description.alternative_keys}:
-                    coordinator: DiscovergyUpdateCoordinator = data.coordinators[
-                        meter.meter_id
-                    ]
                     if key in coordinator.data.values:
                         entities.append(
                             DiscovergySensor(key, description, meter, coordinator)
                         )
 
+        for description in ADDITIONAL_SENSORS:
+            entities.append(
+                DiscovergySensor(description.key, description, meter, coordinator)
+            )
+
     async_add_entities(entities, False)
 
 
@@ -204,8 +224,8 @@ class DiscovergySensor(CoordinatorEntity[DiscovergyUpdateCoordinator], SensorEnt
         )
 
     @property
-    def native_value(self) -> StateType:
+    def native_value(self) -> datetime | float | None:
         """Return the sensor state."""
-        return float(
+        return self.entity_description.value_fn(
-            self.coordinator.data.values[self.data_key] / self.entity_description.scale
+            self.coordinator.data, self.data_key, self.entity_description.scale
         )

homeassistant/components/discovergy/strings.json

@@ -60,6 +60,9 @@
       },
       "phase_3_power": {
         "name": "Phase 3 power"
+      },
+      "last_transmitted": {
+        "name": "Last transmitted"
       }
     }
   }