text: """Support for MQTT sensors."""
  from datetime import timedelta
  import json
  import logging
  from typing import Optional
  
  import voluptuous as vol
  
  from openpeerpower.components import mqtt, sensor
  from openpeerpower.components.sensor import DEVICE_CLASSES_SCHEMA
  from openpeerpower.const import (
      CONF_DEVICE,
      CONF_DEVICE_CLASS,
      CONF_FORCE_UPDATE,
      CONF_ICON,
      CONF_NAME,
      CONF_UNIT_OF_MEASUREMENT,
      CONF_VALUE_TEMPLATE,
  )
  from openpeerpower.core import callback
  import openpeerpower.helpers.config_validation as cv
  from openpeerpower.helpers.dispatcher import async_dispatcher_connect
  from openpeerpower.helpers.entity import Entity
  from openpeerpower.helpers.event import async_track_point_in_utc_time
  from openpeerpower.helpers.typing import ConfigType, OpenPeerPowerType
  from openpeerpower.util import dt as dt_util
  
  from . import (
      ATTR_DISCOVERY_HASH,
      CONF_QOS,
      CONF_STATE_TOPIC,
      CONF_UNIQUE_ID,
      MqttAttributes,
      MqttAvailability,
      MqttDiscoveryUpdate,
      MqttEntityDeviceInfo,
      subscription,
  )
  from .discovery import MQTT_DISCOVERY_NEW, clear_discovery_hash
  
  _LOGGER = logging.getLogger(__name__)
  
  CONF_EXPIRE_AFTER = "expire_after"
  CONF_JSON_ATTRS = "json_attributes"
  
  DEFAULT_NAME = "MQTT Sensor"
  DEFAULT_FORCE_UPDATE = False
  PLATFORM_SCHEMA = (
      mqtt.MQTT_RO_PLATFORM_SCHEMA.extend(
          {
              vol.Optional(CONF_DEVICE): mqtt.MQTT_ENTITY_DEVICE_INFO_SCHEMA,
              vol.Optional(CONF_DEVICE_CLASS): DEVICE_CLASSES_SCHEMA,
              vol.Optional(CONF_EXPIRE_AFTER): cv.positive_int,
              vol.Optional(CONF_FORCE_UPDATE, default=DEFAULT_FORCE_UPDATE): cv.boolean,
              vol.Optional(CONF_ICON): cv.icon,
              vol.Optional(CONF_JSON_ATTRS, default=[]): cv.ensure_list_csv,
              vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
              vol.Optional(CONF_UNIQUE_ID): cv.string,
              vol.Optional(CONF_UNIT_OF_MEASUREMENT): cv.string,
          }
      )
      .extend(mqtt.MQTT_AVAILABILITY_SCHEMA.schema)
      .extend(mqtt.MQTT_JSON_ATTRS_SCHEMA.schema)
  )
  
  
  async def async_setup_platform(
      opp: OpenPeerPowerType, config: ConfigType, async_add_entities, discovery_info=None
  ):
      """Set up MQTT sensors through configuration.yaml."""
      await _async_setup_entity(config, async_add_entities)
  
  
  async def async_setup_entry(opp, config_entry, async_add_entities):
      """Set up MQTT sensors dynamically through MQTT discovery."""
  
      async def async_discover_sensor(discovery_payload):
          """Discover and add a discovered MQTT sensor."""
          try:
              discovery_hash = discovery_payload.pop(ATTR_DISCOVERY_HASH)
              config = PLATFORM_SCHEMA(discovery_payload)
              await _async_setup_entity(
                  config, async_add_entities, config_entry, discovery_hash
              )
          except Exception:
              if discovery_hash:
                  clear_discovery_hash(opp, discovery_hash)
              raise
  
      async_dispatcher_connect(
          opp, MQTT_DISCOVERY_NEW.format(sensor.DOMAIN, "mqtt"), async_discover_sensor
      )
  
  
  async def _async_setup_entity(
      config: ConfigType, async_add_entities, config_entry=None, discovery_hash=None
  ):
      """Set up MQTT sensor."""
      async_add_entities([MqttSensor(config, config_entry, discovery_hash)])
  
  
  class MqttSensor(
      MqttAttributes, MqttAvailability, MqttDiscoveryUpdate, MqttEntityDeviceInfo, Entity
  ):
      """Representation of a sensor that can be updated using MQTT."""
  
      def __init__(self, config, config_entry, discovery_hash):
          """Initialize the sensor."""
          self._config = config
          self._unique_id = config.get(CONF_UNIQUE_ID)
          self._state = None
          self._sub_state = None
          self._expiration_trigger = None
          self._attributes = None
  
          device_config = config.get(CONF_DEVICE)
  
          if config.get(CONF_JSON_ATTRS):
              _LOGGER.warning(
                  'configuration variable "json_attributes" is '
                  'deprecated, replace with "json_attributes_topic"'
              )
  
          MqttAttributes.__init__(self, config)
          MqttAvailability.__init__(self, config)
          MqttDiscoveryUpdate.__init__(self, discovery_hash, self.discovery_update)
          MqttEntityDeviceInfo.__init__(self, device_config, config_entry)
  
      async def async_added_to_opp(self):
          """Subscribe to MQTT events."""
          await super().async_added_to_opp()
          await self._subscribe_topics()
  
      async def discovery_update(self, discovery_payload):
          """Handle updated discovery message."""
          config = PLATFORM_SCHEMA(discovery_payload)
          self._config = config
          await self.attributes_discovery_update(config)
          await self.availability_discovery_update(config)
          await self.device_info_discovery_update(config)
          await self._subscribe_topics()
          self.async_write_op_state()
  
      async def _subscribe_topics(self):
          """(Re)Subscribe to topics."""
          template = self._config.get(CONF_VALUE_TEMPLATE)
          if template is not None:
              template.opp = self.opp
  
          @callback
          def message_received(msg):
              """Handle new MQTT messages."""
              payload = msg.payload
              # auto-expire enabled?
              expire_after = self._config.get(CONF_EXPIRE_AFTER)
              if expire_after is not None and expire_after > 0:
                  # Reset old trigger
                  if self._expiration_trigger:
                      self._expiration_trigger()
                      self._expiration_trigger = None
  
                  # Set new trigger
                  expiration_at = dt_util.utcnow() + timedelta(seconds=expire_after)
  
                  self._expiration_trigger = async_track_point_in_utc_time(
                      self.opp, self.value_is_expired, expiration_at
                  )
  
              json_attributes = set(self._config[CONF_JSON_ATTRS])
              if json_attributes:
                  self._attributes = {}
                  try:
                      json_dict = json.loads(payload)
                      if isinstance(json_dict, dict):
                          attrs = {
                              k: json_dict[k] for k in json_attributes & json_dict.keys()
                          }
                          self._attributes = attrs
                      else:
                          _LOGGER.warning("JSON result was not a dictionary")
                  except ValueError:
                      _LOGGER.warning("MQTT payload could not be parsed as JSON")
                      _LOGGER.debug("Erroneous JSON: %s", payload)
  
              if template is not None:
                  payload = template.async_render_with_possible_json_value(
                      payload, self._state
                  )
              self._state = payload
              self.async_write_op_state()
  
          self._sub_state = await subscription.async_subscribe_topics(
              self.opp,
              self._sub_state,
              {
                  "state_topic": {
                      "topic": self._config[CONF_STATE_TOPIC],
                      "msg_callback": message_received,
                      "qos": self._config[CONF_QOS],
                  }
              },
          )
  
      async def async_will_remove_from_opp(self):
          """Unsubscribe when removed."""
          self._sub_state = await subscription.async_unsubscribe_topics(
              self.opp, self._sub_state
          )
          await MqttAttributes.async_will_remove_from_opp(self)
          await MqttAvailability.async_will_remove_from_opp(self)
  
      @callback
      def value_is_expired(self, *_):
          """Triggered when value is expired."""
          self._expiration_trigger = None
          self._state = None
          self.async_write_op_state()
  
      @property
      def should_poll(self):
          """No polling needed."""
          return False
  
      @property
      def name(self):
          """Return the name of the sensor."""
          return self._config[CONF_NAME]
  
      @property
      def unit_of_measurement(self):
          """Return the unit this state is expressed in."""
          return self._config.get(CONF_UNIT_OF_MEASUREMENT)
  
      @property
      def force_update(self):
          """Force update."""
          return self._config[CONF_FORCE_UPDATE]
  
      @property
      def state(self):
          """Return the state of the entity."""
          return self._state
  
      @property
      def device_state_attributes(self):
          """Return the state attributes."""
          return self._attributes
  
      @property
      def unique_id(self):
          """Return a unique ID."""
          return self._unique_id
  
      @property
      def icon(self):
          """Return the icon."""
          return self._config.get(CONF_ICON)
  
      @property
      def device_class(self) -> Optional[str]:
          """Return the device class of the sensor."""
          return self._config.get(CONF_DEVICE_CLASS)
  