"""Support for MQTT sensors."""
from datetime import timedelta
import logging
from typing import Optional

import voluptuous as vol

from homeassistant.components import mqtt, sensor
from homeassistant.components.sensor import DEVICE_CLASSES_SCHEMA
from homeassistant.const import (
    CONF_DEVICE,
    CONF_DEVICE_CLASS,
    CONF_FORCE_UPDATE,
    CONF_ICON,
    CONF_NAME,
    CONF_UNIT_OF_MEASUREMENT,
    CONF_VALUE_TEMPLATE,
)
from homeassistant.core import callback
import homeassistant.helpers.config_validation as cv
from homeassistant.helpers.dispatcher import async_dispatcher_connect
from homeassistant.helpers.entity import Entity
from homeassistant.helpers.event import async_track_point_in_utc_time
from homeassistant.helpers.typing import ConfigType, HomeAssistantType
from homeassistant.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 .debug_info import log_messages
from .discovery import MQTT_DISCOVERY_NEW, clear_discovery_hash

_LOGGER = logging.getLogger(__name__)

CONF_EXPIRE_AFTER = "expire_after"

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_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(
    hass: HomeAssistantType, 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(hass, 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."""
        discovery_data = discovery_payload.discovery_data
        try:
            config = PLATFORM_SCHEMA(discovery_payload)
            await _async_setup_entity(
                config, async_add_entities, config_entry, discovery_data
            )
        except Exception:
            clear_discovery_hash(hass, discovery_data[ATTR_DISCOVERY_HASH])
            raise

    async_dispatcher_connect(
        hass, MQTT_DISCOVERY_NEW.format(sensor.DOMAIN, "mqtt"), async_discover_sensor
    )


async def _async_setup_entity(
    config: ConfigType, async_add_entities, config_entry=None, discovery_data=None
):
    """Set up MQTT sensor."""
    async_add_entities([MqttSensor(config, config_entry, discovery_data)])


class MqttSensor(
    MqttAttributes, MqttAvailability, MqttDiscoveryUpdate, MqttEntityDeviceInfo, Entity
):
    """Representation of a sensor that can be updated using MQTT."""

    def __init__(self, config, config_entry, discovery_data):
        """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

        device_config = config.get(CONF_DEVICE)

        MqttAttributes.__init__(self, config)
        MqttAvailability.__init__(self, config)
        MqttDiscoveryUpdate.__init__(self, discovery_data, self.discovery_update)
        MqttEntityDeviceInfo.__init__(self, device_config, config_entry)

    async def async_added_to_hass(self):
        """Subscribe to MQTT events."""
        await super().async_added_to_hass()
        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_ha_state()

    async def _subscribe_topics(self):
        """(Re)Subscribe to topics."""
        template = self._config.get(CONF_VALUE_TEMPLATE)
        if template is not None:
            template.hass = self.hass

        @callback
        @log_messages(self.hass, self.entity_id)
        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.hass, self.value_is_expired, expiration_at
                )

            if template is not None:
                payload = template.async_render_with_possible_json_value(
                    payload, self._state
                )
            self._state = payload
            self.async_write_ha_state()

        self._sub_state = await subscription.async_subscribe_topics(
            self.hass,
            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_hass(self):
        """Unsubscribe when removed."""
        self._sub_state = await subscription.async_unsubscribe_topics(
            self.hass, self._sub_state
        )
        await MqttAttributes.async_will_remove_from_hass(self)
        await MqttAvailability.async_will_remove_from_hass(self)
        await MqttDiscoveryUpdate.async_will_remove_from_hass(self)

    @callback
    def value_is_expired(self, *_):
        """Triggered when value is expired."""
        self._expiration_trigger = None
        self._state = None
        self.async_write_ha_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 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)