Add counters sensors for Velbus (#31165)

* Add counter sensor

* Apply black formatting

* Move all counter logic to sensor.py

* Code cleanup

homeassistant/components/velbus/sensor.py

@@ -1,6 +1,8 @@
 """Support for Velbus sensors."""
 import logging
 
+from homeassistant.const import DEVICE_CLASS_POWER, ENERGY_KILO_WATT_HOUR
+
 from . import VelbusEntity
 from .const import DOMAIN
 
@@ -15,23 +17,53 @@ async def async_setup_entry(hass, entry, async_add_entities):
     for address, channel in modules_data:
         module = cntrl.get_module(address)
         entities.append(VelbusSensor(module, channel))
+        if module.get_class(channel) == "counter":
+            entities.append(VelbusSensor(module, channel, True))
     async_add_entities(entities)
 
 
 class VelbusSensor(VelbusEntity):
     """Representation of a sensor."""
 
+    def __init__(self, module, channel, counter=False):
+        """Initialize a sensor Velbus entity."""
+        super().__init__(module, channel)
+        self._is_counter = counter
+
+    @property
+    def unique_id(self):
+        """Return unique ID for counter sensors."""
+        unique_id = super().unique_id
+        if self._is_counter:
+            unique_id = f"{unique_id}-counter"
+        return unique_id
+
     @property
     def device_class(self):
         """Return the device class of the sensor."""
+        if self._module.get_class(self._channel) == "counter" and not self._is_counter:
+            if self._module.get_counter_unit(self._channel) == ENERGY_KILO_WATT_HOUR:
+                return DEVICE_CLASS_POWER
+            return None
         return self._module.get_class(self._channel)
 
     @property
     def state(self):
         """Return the state of the sensor."""
+        if self._is_counter:
+            return self._module.get_counter_state(self._channel)
         return self._module.get_state(self._channel)
 
     @property
     def unit_of_measurement(self):
         """Return the unit this state is expressed in."""
+        if self._is_counter:
+            return self._module.get_counter_unit(self._channel)
         return self._module.get_unit(self._channel)
+
+    @property
+    def icon(self):
+        """Icon to use in the frontend."""
+        if self._is_counter:
+            return "mdi:counter"
+        return None