"""
Support for the Awair indoor air quality monitor.

For more details about this platform, please refer to the documentation at
https://home-assistant.io/components/sensor.awair/
"""

from datetime import timedelta
import logging
import math

import voluptuous as vol

from homeassistant.const import (
    CONF_ACCESS_TOKEN, CONF_DEVICES, DEVICE_CLASS_HUMIDITY,
    DEVICE_CLASS_TEMPERATURE, TEMP_CELSIUS)
from homeassistant.exceptions import PlatformNotReady
from homeassistant.helpers.aiohttp_client import async_get_clientsession
import homeassistant.helpers.config_validation as cv
from homeassistant.helpers.entity import Entity
from homeassistant.util import Throttle, dt

REQUIREMENTS = ['python_awair==0.0.3']

_LOGGER = logging.getLogger(__name__)

ATTR_SCORE = 'score'
ATTR_TIMESTAMP = 'timestamp'
ATTR_LAST_API_UPDATE = 'last_api_update'
ATTR_COMPONENT = 'component'
ATTR_VALUE = 'value'
ATTR_SENSORS = 'sensors'

CONF_UUID = 'uuid'

DEVICE_CLASS_PM2_5 = 'PM2.5'
DEVICE_CLASS_PM10 = 'PM10'
DEVICE_CLASS_CARBON_DIOXIDE = 'CO2'
DEVICE_CLASS_VOLATILE_ORGANIC_COMPOUNDS = 'VOC'
DEVICE_CLASS_SCORE = 'score'

SENSOR_TYPES = {
    'TEMP': {'device_class': DEVICE_CLASS_TEMPERATURE,
             'unit_of_measurement': TEMP_CELSIUS,
             'icon': 'mdi:thermometer'},
    'HUMID': {'device_class': DEVICE_CLASS_HUMIDITY,
              'unit_of_measurement': '%',
              'icon': 'mdi:water-percent'},
    'CO2': {'device_class': DEVICE_CLASS_CARBON_DIOXIDE,
            'unit_of_measurement': 'ppm',
            'icon': 'mdi:periodic-table-co2'},
    'VOC': {'device_class': DEVICE_CLASS_VOLATILE_ORGANIC_COMPOUNDS,
            'unit_of_measurement': 'ppb',
            'icon': 'mdi:cloud'},
    # Awair docs don't actually specify the size they measure for 'dust',
    # but 2.5 allows the sensor to show up in HomeKit
    'DUST': {'device_class': DEVICE_CLASS_PM2_5,
             'unit_of_measurement': 'µg/m3',
             'icon': 'mdi:cloud'},
    'PM25': {'device_class': DEVICE_CLASS_PM2_5,
             'unit_of_measurement': 'µg/m3',
             'icon': 'mdi:cloud'},
    'PM10': {'device_class': DEVICE_CLASS_PM10,
             'unit_of_measurement': 'µg/m3',
             'icon': 'mdi:cloud'},
    'score': {'device_class': DEVICE_CLASS_SCORE,
              'unit_of_measurement': '%',
              'icon': 'mdi:percent'},
}

AWAIR_QUOTA = 300

# This is the minimum time between throttled update calls.
# Don't bother asking us for state more often than that.
SCAN_INTERVAL = timedelta(minutes=5)

AWAIR_DEVICE_SCHEMA = vol.Schema({
    vol.Required(CONF_UUID): cv.string,
})

PLATFORM_SCHEMA = cv.PLATFORM_SCHEMA.extend({
    vol.Required(CONF_ACCESS_TOKEN): cv.string,
    vol.Optional(CONF_DEVICES): vol.All(
        cv.ensure_list, [AWAIR_DEVICE_SCHEMA]),
})


# Awair *heavily* throttles calls that get user information,
# and calls that get the list of user-owned devices - they
# allow 30 per DAY. So, we permit a user to provide a static
# list of devices, and they may provide the same set of information
# that the devices() call would return. However, the only thing
# used at this time is the `uuid` value.
async def async_setup_platform(hass, config, async_add_entities,
                               discovery_info=None):
    """Connect to the Awair API and find devices."""
    from python_awair import AwairClient

    token = config[CONF_ACCESS_TOKEN]
    client = AwairClient(token, session=async_get_clientsession(hass))

    try:
        all_devices = []
        devices = config.get(CONF_DEVICES, await client.devices())

        # Try to throttle dynamically based on quota and number of devices.
        throttle_minutes = math.ceil(60 / ((AWAIR_QUOTA / len(devices)) / 24))
        throttle = timedelta(minutes=throttle_minutes)

        for device in devices:
            _LOGGER.debug("Found awair device: %s", device)
            awair_data = AwairData(client, device[CONF_UUID], throttle)
            await awair_data.async_update()
            for sensor in SENSOR_TYPES:
                if sensor in awair_data.data:
                    awair_sensor = AwairSensor(awair_data, device,
                                               sensor, throttle)
                    all_devices.append(awair_sensor)

        async_add_entities(all_devices, True)
        return
    except AwairClient.AuthError:
        _LOGGER.error("Awair API access_token invalid")
    except AwairClient.RatelimitError:
        _LOGGER.error("Awair API ratelimit exceeded.")
    except (AwairClient.QueryError, AwairClient.NotFoundError,
            AwairClient.GenericError) as error:
        _LOGGER.error("Unexpected Awair API error: %s", error)

    raise PlatformNotReady


class AwairSensor(Entity):
    """Implementation of an Awair device."""

    def __init__(self, data, device, sensor_type, throttle):
        """Initialize the sensor."""
        self._uuid = device[CONF_UUID]
        self._device_class = SENSOR_TYPES[sensor_type]['device_class']
        self._name = 'Awair {}'.format(self._device_class)
        unit = SENSOR_TYPES[sensor_type]['unit_of_measurement']
        self._unit_of_measurement = unit
        self._data = data
        self._type = sensor_type
        self._throttle = throttle

    @property
    def name(self):
        """Return the name of the sensor."""
        return self._name

    @property
    def device_class(self):
        """Return the device class."""
        return self._device_class

    @property
    def icon(self):
        """Icon to use in the frontend."""
        return SENSOR_TYPES[self._type]['icon']

    @property
    def state(self):
        """Return the state of the device."""
        return self._data.data[self._type]

    @property
    def device_state_attributes(self):
        """Return additional attributes."""
        return self._data.attrs

    # The Awair device should be reporting metrics in quite regularly.
    # Based on the raw data from the API, it looks like every ~10 seconds
    # is normal. Here we assert that the device is not available if the
    # last known API timestamp is more than (3 * throttle) minutes in the
    # past. It implies that either hass is somehow unable to query the API
    # for new data or that the device is not checking in. Either condition
    # fits the definition for 'not available'. We pick (3 * throttle) minutes
    # to allow for transient errors to correct themselves.
    @property
    def available(self):
        """Device availability based on the last update timestamp."""
        if ATTR_LAST_API_UPDATE not in self.device_state_attributes:
            return False

        last_api_data = self.device_state_attributes[ATTR_LAST_API_UPDATE]
        return (dt.utcnow() - last_api_data) < (3 * self._throttle)

    @property
    def unique_id(self):
        """Return the unique id of this entity."""
        return "{}_{}".format(self._uuid, self._type)

    @property
    def unit_of_measurement(self):
        """Return the unit of measurement of this entity."""
        return self._unit_of_measurement

    async def async_update(self):
        """Get the latest data."""
        await self._data.async_update()


class AwairData:
    """Get data from Awair API."""

    def __init__(self, client, uuid, throttle):
        """Initialize the data object."""
        self._client = client
        self._uuid = uuid
        self.data = {}
        self.attrs = {}
        self.async_update = Throttle(throttle)(self._async_update)

    async def _async_update(self):
        """Get the data from Awair API."""
        resp = await self._client.air_data_latest(self._uuid)

        if not resp:
            return

        timestamp = dt.parse_datetime(resp[0][ATTR_TIMESTAMP])
        self.attrs[ATTR_LAST_API_UPDATE] = timestamp
        self.data[ATTR_SCORE] = resp[0][ATTR_SCORE]

        # The air_data_latest call only returns one item, so this should
        # be safe to only process one entry.
        for sensor in resp[0][ATTR_SENSORS]:
            self.data[sensor[ATTR_COMPONENT]] = sensor[ATTR_VALUE]

        _LOGGER.debug("Got Awair Data for %s: %s", self._uuid, self.data)