"""
homeassistant.components.alarm_control_panel.mqtt

This platform enables the possibility to control a MQTT alarm.
In this platform, 'state_topic' and 'command_topic' are required.
The alarm will only change state after receiving the a new state
from 'state_topic'. If these messages are published with RETAIN flag,
the MQTT alarm will receive an instant state update after subscription
and will start with correct state. Otherwise, the initial state will
be 'unknown'.

Configuration:

alarm_control_panel:
  platform: mqtt
  name: "MQTT Alarm"
  state_topic: "home/alarm"
  command_topic: "home/alarm/set"
  qos: 0
  payload_disarm: "DISARM"
  payload_arm_home: "ARM_HOME"
  payload_arm_away: "ARM_AWAY"

Variables:

name
*Optional
The name of the alarm. Default is 'MQTT Alarm'.

state_topic
*Required
The MQTT topic subscribed to receive state updates.

command_topic
*Required
The MQTT topic to publish commands to change the alarm state.

qos
*Optional
The maximum QoS level of the state topic. Default is 0.
This QoS will also be used to publishing messages.

payload_disarm
*Optional
The payload do disarm alarm. Default is "DISARM".

payload_arm_home
*Optional
The payload to set armed-home mode. Default is "ARM_HOME".

payload_arm_away
*Optional
The payload to set armed-away mode. Default is "ARM_AWAY".

"""

import logging
import homeassistant.components.mqtt as mqtt
import homeassistant.components.alarm_control_panel as alarm

from homeassistant.const import (STATE_UNKNOWN)

_LOGGER = logging.getLogger(__name__)

DEFAULT_NAME = "MQTT Alarm"
DEFAULT_QOS = 0
DEFAULT_PAYLOAD_DISARM = "DISARM"
DEFAULT_PAYLOAD_ARM_HOME = "ARM_HOME"
DEFAULT_PAYLOAD_ARM_AWAY = "ARM_AWAY"

DEPENDENCIES = ['mqtt']


def setup_platform(hass, config, add_devices, discovery_info=None):
    """ Sets up the MQTT platform. """

    if config.get('state_topic') is None:
        _LOGGER.error("Missing required variable: state_topic")
        return False

    if config.get('command_topic') is None:
        _LOGGER.error("Missing required variable: command_topic")
        return False

    add_devices([MqttAlarm(
        hass,
        config.get('name', DEFAULT_NAME),
        config.get('state_topic'),
        config.get('command_topic'),
        config.get('qos', DEFAULT_QOS),
        config.get('payload_disarm', DEFAULT_PAYLOAD_DISARM),
        config.get('payload_arm_home', DEFAULT_PAYLOAD_ARM_HOME),
        config.get('payload_arm_away', DEFAULT_PAYLOAD_ARM_AWAY))])


# pylint: disable=too-many-arguments, too-many-instance-attributes
class MqttAlarm(alarm.AlarmControlPanel):
    """ represents a MQTT alarm status within home assistant. """

    def __init__(self, hass, name, state_topic, command_topic, qos,
                 payload_disarm, payload_arm_home, payload_arm_away):
        self._state = STATE_UNKNOWN
        self._hass = hass
        self._name = name
        self._state_topic = state_topic
        self._command_topic = command_topic
        self._qos = qos
        self._payload_disarm = payload_disarm
        self._payload_arm_home = payload_arm_home
        self._payload_arm_away = payload_arm_away

        def message_received(topic, payload, qos):
            """ A new MQTT message has been received. """
            self._state = payload
            self.update_ha_state()

        mqtt.subscribe(hass, self._state_topic, message_received, self._qos)

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

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

    @property
    def state(self):
        """ Returns the state of the device. """
        return self._state

    def alarm_disarm(self, code):
        """ Send disarm command. """
        mqtt.publish(self.hass, self._command_topic, self._payload_disarm,
                     self._qos)

    def alarm_arm_home(self, code):
        """ Send arm home command. """
        mqtt.publish(self.hass, self._command_topic, self._payload_arm_home,
                     self._qos)

    def alarm_arm_away(self, code):
        """ Send arm away command. """
        mqtt.publish(self.hass, self._command_topic, self._payload_arm_away,
                     self._qos)