"""
Adds support for generic thermostat units.

For more details about this platform, please refer to the documentation at
https://home-assistant.io/components/climate.generic_thermostat/
"""
import logging
import voluptuous as vol

import homeassistant.helpers.config_validation as cv
from homeassistant.components import switch
from homeassistant.components.climate import (
    STATE_HEAT, STATE_COOL, STATE_IDLE, ClimateDevice)
from homeassistant.const import ATTR_UNIT_OF_MEASUREMENT, STATE_ON, STATE_OFF
from homeassistant.helpers import condition
from homeassistant.helpers.event import track_state_change

DEPENDENCIES = ['switch', 'sensor']

TOL_TEMP = 0.3

CONF_NAME = 'name'
DEFAULT_NAME = 'Generic Thermostat'
CONF_HEATER = 'heater'
CONF_SENSOR = 'target_sensor'
CONF_MIN_TEMP = 'min_temp'
CONF_MAX_TEMP = 'max_temp'
CONF_TARGET_TEMP = 'target_temp'
CONF_AC_MODE = 'ac_mode'
CONF_MIN_DUR = 'min_cycle_duration'

_LOGGER = logging.getLogger(__name__)

PLATFORM_SCHEMA = vol.Schema({
    vol.Required("platform"): "generic_thermostat",
    vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
    vol.Required(CONF_HEATER): cv.entity_id,
    vol.Required(CONF_SENSOR): cv.entity_id,
    vol.Optional(CONF_MIN_TEMP): vol.Coerce(float),
    vol.Optional(CONF_MAX_TEMP): vol.Coerce(float),
    vol.Optional(CONF_TARGET_TEMP): vol.Coerce(float),
    vol.Optional(CONF_AC_MODE): vol.Coerce(bool),
    vol.Optional(CONF_MIN_DUR): vol.All(cv.time_period, cv.positive_timedelta),
})


def setup_platform(hass, config, add_devices, discovery_info=None):
    """Setup the generic thermostat."""
    name = config.get(CONF_NAME)
    heater_entity_id = config.get(CONF_HEATER)
    sensor_entity_id = config.get(CONF_SENSOR)
    min_temp = config.get(CONF_MIN_TEMP)
    max_temp = config.get(CONF_MAX_TEMP)
    target_temp = config.get(CONF_TARGET_TEMP)
    ac_mode = config.get(CONF_AC_MODE)
    min_cycle_duration = config.get(CONF_MIN_DUR)

    add_devices([GenericThermostat(hass, name, heater_entity_id,
                                   sensor_entity_id, min_temp,
                                   max_temp, target_temp, ac_mode,
                                   min_cycle_duration)])


# pylint: disable=too-many-instance-attributes, abstract-method
class GenericThermostat(ClimateDevice):
    """Representation of a GenericThermostat device."""

    # pylint: disable=too-many-arguments
    def __init__(self, hass, name, heater_entity_id, sensor_entity_id,
                 min_temp, max_temp, target_temp, ac_mode, min_cycle_duration):
        """Initialize the thermostat."""
        self.hass = hass
        self._name = name
        self.heater_entity_id = heater_entity_id
        self.ac_mode = ac_mode
        self.min_cycle_duration = min_cycle_duration

        self._active = False
        self._cur_temp = None
        self._min_temp = min_temp
        self._max_temp = max_temp
        self._target_temp = target_temp
        self._unit = hass.config.units.temperature_unit

        track_state_change(hass, sensor_entity_id, self._sensor_changed)

        sensor_state = hass.states.get(sensor_entity_id)
        if sensor_state:
            self._update_temp(sensor_state)

    @property
    def should_poll(self):
        """No polling needed."""
        return False

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

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

    @property
    def current_temperature(self):
        """Return the sensor temperature."""
        return self._cur_temp

    @property
    def operation(self):
        """Return current operation ie. heat, cool, idle."""
        if self.ac_mode:
            cooling = self._active and self._is_device_active
            return STATE_COOL if cooling else STATE_IDLE
        else:
            heating = self._active and self._is_device_active
            return STATE_HEAT if heating else STATE_IDLE

    @property
    def target_temperature(self):
        """Return the temperature we try to reach."""
        return self._target_temp

    def set_temperature(self, temperature):
        """Set new target temperature."""
        self._target_temp = temperature
        self._control_heating()
        self.update_ha_state()

    @property
    def min_temp(self):
        """Return the minimum temperature."""
        # pylint: disable=no-member
        if self._min_temp:
            return self._min_temp
        else:
            # get default temp from super class
            return ClimateDevice.min_temp.fget(self)

    @property
    def max_temp(self):
        """Return the maximum temperature."""
        # pylint: disable=no-member
        if self._min_temp:
            return self._max_temp
        else:
            # Get default temp from super class
            return ClimateDevice.max_temp.fget(self)

    def _sensor_changed(self, entity_id, old_state, new_state):
        """Called when temperature changes."""
        if new_state is None:
            return

        self._update_temp(new_state)
        self._control_heating()
        self.update_ha_state()

    def _update_temp(self, state):
        """Update thermostat with latest state from sensor."""
        unit = state.attributes.get(ATTR_UNIT_OF_MEASUREMENT)

        try:
            self._cur_temp = self.hass.config.units.temperature(
                float(state.state), unit)
        except ValueError as ex:
            _LOGGER.error('Unable to update from sensor: %s', ex)

    def _control_heating(self):
        """Check if we need to turn heating on or off."""
        if not self._active and None not in (self._cur_temp,
                                             self._target_temp):
            self._active = True
            _LOGGER.info('Obtained current and target temperature. '
                         'Generic thermostat active.')

        if not self._active:
            return

        if self.min_cycle_duration:
            if self._is_device_active:
                current_state = STATE_ON
            else:
                current_state = STATE_OFF
            long_enough = condition.state(self.hass, self.heater_entity_id,
                                          current_state,
                                          self.min_cycle_duration)
            if not long_enough:
                return

        if self.ac_mode:
            too_hot = self._cur_temp - self._target_temp > TOL_TEMP
            is_cooling = self._is_device_active
            if too_hot and not is_cooling:
                _LOGGER.info('Turning on AC %s', self.heater_entity_id)
                switch.turn_on(self.hass, self.heater_entity_id)
            elif not too_hot and is_cooling:
                _LOGGER.info('Turning off AC %s', self.heater_entity_id)
                switch.turn_off(self.hass, self.heater_entity_id)
        else:
            too_cold = self._target_temp - self._cur_temp > TOL_TEMP
            is_heating = self._is_device_active

            if too_cold and not is_heating:
                _LOGGER.info('Turning on heater %s', self.heater_entity_id)
                switch.turn_on(self.hass, self.heater_entity_id)
            elif not too_cold and is_heating:
                _LOGGER.info('Turning off heater %s', self.heater_entity_id)
                switch.turn_off(self.hass, self.heater_entity_id)

    @property
    def _is_device_active(self):
        """If the toggleable device is currently active."""
        return switch.is_on(self.hass, self.heater_entity_id)
