"""
homeassistant.components.script
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
entity_id
Scripts are a sequence of actions that can be triggered manually
by the user or automatically based upon automation events, etc.
"""
import logging
from datetime import timedelta
import homeassistant.util.dt as date_util
from itertools import islice
import threading

from homeassistant.helpers.entity_component import EntityComponent
from homeassistant.helpers.entity import ToggleEntity
from homeassistant.helpers.event import track_point_in_utc_time
from homeassistant.util import split_entity_id
from homeassistant.const import (
    ATTR_ENTITY_ID, EVENT_TIME_CHANGED, STATE_ON, SERVICE_TURN_ON,
    SERVICE_TURN_OFF)

DOMAIN = "script"
ENTITY_ID_FORMAT = DOMAIN + '.{}'
DEPENDENCIES = ["group"]

STATE_NOT_RUNNING = 'Not Running'

CONF_ALIAS = "alias"
CONF_SERVICE = "service"
CONF_SERVICE_OLD = "execute_service"
CONF_SERVICE_DATA = "service_data"
CONF_SEQUENCE = "sequence"
CONF_EVENT = "event"
CONF_EVENT_DATA = "event_data"
CONF_DELAY = "delay"

ATTR_LAST_ACTION = 'last_action'

_LOGGER = logging.getLogger(__name__)


def is_on(hass, entity_id):
    """ Returns if the switch is on based on the statemachine. """
    return hass.states.is_state(entity_id, STATE_ON)


def turn_on(hass, entity_id):
    """ Turn script on. """
    _, object_id = split_entity_id(entity_id)

    hass.services.call(DOMAIN, object_id)


def turn_off(hass, entity_id):
    """ Turn script on. """
    hass.services.call(DOMAIN, SERVICE_TURN_OFF, {ATTR_ENTITY_ID: entity_id})


def setup(hass, config):
    """ Load the scripts from the configuration. """

    component = EntityComponent(_LOGGER, DOMAIN, hass)

    def service_handler(service):
        """ Execute a service call to script.<script name>. """
        entity_id = ENTITY_ID_FORMAT.format(service.service)
        script = component.entities.get(entity_id)
        if script:
            script.turn_on()

    for name, cfg in config[DOMAIN].items():
        if not cfg.get(CONF_SEQUENCE):
            _LOGGER.warn("Missing key 'sequence' for script %s", name)
            continue
        alias = cfg.get(CONF_ALIAS, name)
        script = Script(hass, alias, cfg[CONF_SEQUENCE])
        component.add_entities((script,))
        _, object_id = split_entity_id(script.entity_id)
        hass.services.register(DOMAIN, object_id, service_handler)

    def turn_on_service(service):
        """ Calls a service to turn script on. """
        # We could turn on script directly here, but we only want to offer
        # one way to do it. Otherwise no easy way to call invocations.
        for script in component.extract_from_service(service):
            turn_on(hass, script.entity_id)

    def turn_off_service(service):
        """ Cancels a script. """
        for script in component.extract_from_service(service):
            script.turn_off()

    hass.services.register(DOMAIN, SERVICE_TURN_ON, turn_on_service)
    hass.services.register(DOMAIN, SERVICE_TURN_OFF, turn_off_service)

    return True


class Script(ToggleEntity):
    """ Represents a script. """
    def __init__(self, hass, name, sequence):
        self.hass = hass
        self._name = name
        self.sequence = sequence
        self._lock = threading.Lock()
        self._cur = -1
        self._last_action = None
        self._listener = None

    @property
    def should_poll(self):
        return False

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

    @property
    def state_attributes(self):
        """ Returns the state attributes. """
        attrs = {}

        if self._last_action:
            attrs[ATTR_LAST_ACTION] = self._last_action

        return attrs

    @property
    def is_on(self):
        """ True if entity is on. """
        return self._cur != -1

    def turn_on(self, **kwargs):
        """ Turn the entity on. """
        _LOGGER.info("Executing script %s", self._name)
        with self._lock:
            if self._cur == -1:
                self._cur = 0

            # Unregister callback if we were in a delay but turn on is called
            # again. In that case we just continue execution.
            self._remove_listener()

            for cur, action in islice(enumerate(self.sequence), self._cur,
                                      None):

                if CONF_SERVICE in action or CONF_SERVICE_OLD in action:
                    self._call_service(action)

                elif CONF_EVENT in action:
                    self._fire_event(action)

                elif CONF_DELAY in action:
                    # Call ourselves in the future to continue work
                    def script_delay(now):
                        """ Called after delay is done. """
                        self._listener = None
                        self.turn_on()

                    delay = timedelta(**action[CONF_DELAY])
                    self._listener = track_point_in_utc_time(
                        self.hass, script_delay, date_util.utcnow() + delay)
                    self._cur = cur + 1
                    self.update_ha_state()
                    return

            self._cur = -1
            self._last_action = None
            self.update_ha_state()

    def turn_off(self, **kwargs):
        """ Turn script off. """
        _LOGGER.info("Cancelled script %s", self._name)
        with self._lock:
            if self._cur == -1:
                return

            self._cur = -1
            self.update_ha_state()
            self._remove_listener()

    def _call_service(self, action):
        """ Calls the service specified in the action. """
        conf_service = action.get(CONF_SERVICE, action.get(CONF_SERVICE_OLD))
        self._last_action = action.get(CONF_ALIAS, conf_service)
        _LOGGER.info("Executing script %s step %s", self._name,
                     self._last_action)
        domain, service = split_entity_id(conf_service)
        data = action.get(CONF_SERVICE_DATA, {})
        self.hass.services.call(domain, service, data)

    def _fire_event(self, action):
        """ Fires an event. """
        self._last_action = action.get(CONF_ALIAS, action[CONF_EVENT])
        _LOGGER.info("Executing script %s step %s", self._name,
                     self._last_action)
        self.hass.bus.fire(action[CONF_EVENT], action.get(CONF_EVENT_DATA))

    def _remove_listener(self):
        """ Remove point in time listener, if any. """
        if self._listener:
            self.hass.bus.remove_listener(EVENT_TIME_CHANGED,
                                          self._listener)
            self._listener = None