"""Support for DSMR Reader through MQTT."""
from __future__ import annotations

from homeassistant.components import mqtt
from homeassistant.components.sensor import SensorEntity
from homeassistant.config_entries import ConfigEntry
from homeassistant.core import HomeAssistant, callback
from homeassistant.helpers.entity_platform import AddEntitiesCallback
from homeassistant.util import slugify

from .definitions import SENSORS, DSMRReaderSensorEntityDescription


async def async_setup_entry(
    _: HomeAssistant,
    config_entry: ConfigEntry,
    async_add_entities: AddEntitiesCallback,
) -> None:
    """Set up DSMR Reader sensors from config entry."""
    async_add_entities(DSMRSensor(description, config_entry) for description in SENSORS)


class DSMRSensor(SensorEntity):
    """Representation of a DSMR sensor that is updated via MQTT."""

    entity_description: DSMRReaderSensorEntityDescription

    def __init__(
        self, description: DSMRReaderSensorEntityDescription, config_entry: ConfigEntry
    ) -> None:
        """Initialize the sensor."""
        self.entity_description = description

        slug = slugify(description.key.replace("/", "_"))
        self.entity_id = f"sensor.{slug}"
        self._attr_unique_id = f"{config_entry.entry_id}-{slug}"

    async def async_added_to_hass(self) -> None:
        """Subscribe to MQTT events."""

        @callback
        def message_received(message):
            """Handle new MQTT messages."""
            if message.payload == "":
                self._attr_native_value = None
            elif self.entity_description.state is not None:
                # Perform optional additional parsing
                self._attr_native_value = self.entity_description.state(message.payload)
            else:
                self._attr_native_value = message.payload

            self.async_write_ha_state()

        await mqtt.async_subscribe(
            self.hass, self.entity_description.key, message_received, 1
        )
