"""Support for Generic Modbus Thermostats."""
import logging
import struct

import voluptuous as vol

from homeassistant.components.climate import PLATFORM_SCHEMA, ClimateDevice
from homeassistant.components.climate.const import (
    SUPPORT_TARGET_TEMPERATURE, HVAC_MODE_HEAT)
from homeassistant.const import ATTR_TEMPERATURE, CONF_NAME, CONF_SLAVE
import homeassistant.helpers.config_validation as cv

from . import CONF_HUB, DEFAULT_HUB, DOMAIN as MODBUS_DOMAIN

_LOGGER = logging.getLogger(__name__)

CONF_TARGET_TEMP = 'target_temp_register'
CONF_CURRENT_TEMP = 'current_temp_register'
CONF_DATA_TYPE = 'data_type'
CONF_COUNT = 'data_count'
CONF_PRECISION = 'precision'

DATA_TYPE_INT = 'int'
DATA_TYPE_UINT = 'uint'
DATA_TYPE_FLOAT = 'float'
SUPPORT_FLAGS = SUPPORT_TARGET_TEMPERATURE
HVAC_MODES = [HVAC_MODE_HEAT]

PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
    vol.Required(CONF_CURRENT_TEMP): cv.positive_int,
    vol.Required(CONF_NAME): cv.string,
    vol.Required(CONF_SLAVE): cv.positive_int,
    vol.Required(CONF_TARGET_TEMP): cv.positive_int,
    vol.Optional(CONF_COUNT, default=2): cv.positive_int,
    vol.Optional(CONF_DATA_TYPE, default=DATA_TYPE_FLOAT):
        vol.In([DATA_TYPE_INT, DATA_TYPE_UINT, DATA_TYPE_FLOAT]),
    vol.Optional(CONF_HUB, default=DEFAULT_HUB): cv.string,
    vol.Optional(CONF_PRECISION, default=1): cv.positive_int,
})


def setup_platform(hass, config, add_entities, discovery_info=None):
    """Set up the Modbus Thermostat Platform."""
    name = config.get(CONF_NAME)
    modbus_slave = config.get(CONF_SLAVE)
    target_temp_register = config.get(CONF_TARGET_TEMP)
    current_temp_register = config.get(CONF_CURRENT_TEMP)
    data_type = config.get(CONF_DATA_TYPE)
    count = config.get(CONF_COUNT)
    precision = config.get(CONF_PRECISION)
    hub_name = config.get(CONF_HUB)
    hub = hass.data[MODBUS_DOMAIN][hub_name]

    add_entities([ModbusThermostat(
        hub, name, modbus_slave, target_temp_register, current_temp_register,
        data_type, count, precision)], True)


class ModbusThermostat(ClimateDevice):
    """Representation of a Modbus Thermostat."""

    def __init__(self, hub, name, modbus_slave, target_temp_register,
                 current_temp_register, data_type, count, precision):
        """Initialize the unit."""
        self._hub = hub
        self._name = name
        self._slave = modbus_slave
        self._target_temperature_register = target_temp_register
        self._current_temperature_register = current_temp_register
        self._target_temperature = None
        self._current_temperature = None
        self._data_type = data_type
        self._count = int(count)
        self._precision = precision
        self._structure = '>f'

        data_types = {
            DATA_TYPE_INT: {1: 'h', 2: 'i', 4: 'q'},
            DATA_TYPE_UINT: {1: 'H', 2: 'I', 4: 'Q'},
            DATA_TYPE_FLOAT: {1: 'e', 2: 'f', 4: 'd'},
        }

        self._structure = '>{}'.format(
            data_types[self._data_type][self._count])

    @property
    def supported_features(self):
        """Return the list of supported features."""
        return SUPPORT_FLAGS

    def update(self):
        """Update Target & Current Temperature."""
        self._target_temperature = self.read_register(
            self._target_temperature_register)
        self._current_temperature = self.read_register(
            self._current_temperature_register)

    @property
    def hvac_mode(self):
        """Return the current HVAC mode."""
        return HVAC_MODE_HEAT

    @property
    def hvac_modes(self):
        """Return the possible HVAC modes."""
        return HVAC_MODES

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

    @property
    def current_temperature(self):
        """Return the current temperature."""
        return self._current_temperature

    @property
    def target_temperature(self):
        """Return the target temperature."""
        return self._target_temperature

    def set_temperature(self, **kwargs):
        """Set new target temperature."""
        target_temperature = kwargs.get(ATTR_TEMPERATURE)
        if target_temperature is None:
            return
        byte_string = struct.pack(self._structure, target_temperature)
        register_value = struct.unpack('>h', byte_string[0:2])[0]

        try:
            self.write_register(
                self._target_temperature_register, register_value)
        except AttributeError as ex:
            _LOGGER.error(ex)

    def read_register(self, register):
        """Read holding register using the Modbus hub slave."""
        try:
            result = self._hub.read_holding_registers(
                self._slave, register, self._count)
        except AttributeError as ex:
            _LOGGER.error(ex)
        byte_string = b''.join(
            [x.to_bytes(2, byteorder='big') for x in result.registers])
        val = struct.unpack(self._structure, byte_string)[0]
        register_value = format(val, '.{}f'.format(self._precision))
        return register_value

    def write_register(self, register, value):
        """Write register using the Modbus hub slave."""
        self._hub.write_registers(self._slave, register, [value, 0])
