"""Support for consuming values for the Volkszaehler API."""
from datetime import timedelta
import logging

import voluptuous as vol

from homeassistant.components.sensor import PLATFORM_SCHEMA
from homeassistant.const import (
    CONF_HOST, CONF_NAME, CONF_PORT, CONF_MONITORED_CONDITIONS, POWER_WATT,
    ENERGY_WATT_HOUR)
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

_LOGGER = logging.getLogger(__name__)

CONF_UUID = 'uuid'

DEFAULT_HOST = 'localhost'
DEFAULT_NAME = 'Volkszaehler'
DEFAULT_PORT = 80

MIN_TIME_BETWEEN_UPDATES = timedelta(minutes=1)

SENSOR_TYPES = {
    'average': ['Average', POWER_WATT, 'mdi:power-off'],
    'consumption': ['Consumption', ENERGY_WATT_HOUR, 'mdi:power-plug'],
    'max': ['Max', POWER_WATT, 'mdi:arrow-up'],
    'min': ['Min', POWER_WATT, 'mdi:arrow-down'],
}

PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
    vol.Required(CONF_UUID): cv.string,
    vol.Optional(CONF_HOST, default=DEFAULT_HOST): cv.string,
    vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
    vol.Optional(CONF_PORT, default=DEFAULT_PORT): cv.port,
    vol.Optional(CONF_MONITORED_CONDITIONS, default=['average']):
        vol.All(cv.ensure_list, [vol.In(SENSOR_TYPES)]),
})


async def async_setup_platform(
        hass, config, async_add_entities, discovery_info=None):
    """Set up the Volkszaehler sensors."""
    from volkszaehler import Volkszaehler

    host = config[CONF_HOST]
    name = config[CONF_NAME]
    port = config[CONF_PORT]
    uuid = config[CONF_UUID]
    conditions = config[CONF_MONITORED_CONDITIONS]

    session = async_get_clientsession(hass)
    vz_api = VolkszaehlerData(
        Volkszaehler(hass.loop, session, uuid, host=host, port=port))

    await vz_api.async_update()

    if vz_api.api.data is None:
        raise PlatformNotReady

    dev = []
    for condition in conditions:
        dev.append(VolkszaehlerSensor(vz_api, name, condition))

    async_add_entities(dev, True)


class VolkszaehlerSensor(Entity):
    """Implementation of a Volkszaehler sensor."""

    def __init__(self, vz_api, name, sensor_type):
        """Initialize the Volkszaehler sensor."""
        self.vz_api = vz_api
        self._name = name
        self.type = sensor_type
        self._state = None

    @property
    def name(self):
        """Return the name of the sensor."""
        return '{} {}'.format(self._name, SENSOR_TYPES[self.type][0])

    @property
    def icon(self):
        """Icon to use in the frontend, if any."""
        return SENSOR_TYPES[self.type][2]

    @property
    def unit_of_measurement(self):
        """Return the unit the value is expressed in."""
        return SENSOR_TYPES[self.type][1]

    @property
    def available(self):
        """Could the device be accessed during the last update call."""
        return self.vz_api.available

    @property
    def state(self):
        """Return the state of the resources."""
        return self._state

    async def async_update(self):
        """Get the latest data from REST API."""
        await self.vz_api.async_update()

        if self.vz_api.api.data is not None:
            self._state = round(getattr(self.vz_api.api, self.type), 2)


class VolkszaehlerData:
    """The class for handling the data retrieval from the Volkszaehler API."""

    def __init__(self, api):
        """Initialize the data object."""
        self.api = api
        self.available = True

    @Throttle(MIN_TIME_BETWEEN_UPDATES)
    async def async_update(self):
        """Get the latest data from the Volkszaehler REST API."""
        from volkszaehler.exceptions import VolkszaehlerApiConnectionError

        try:
            await self.api.get_data()
            self.available = True
        except VolkszaehlerApiConnectionError:
            _LOGGER.error("Unable to fetch data from the Volkszaehler API")
            self.available = False