"""Helpers for components that manage entities."""
from threading import Lock

from homeassistant.bootstrap import prepare_setup_platform
from homeassistant.components import discovery, group
from homeassistant.const import ATTR_ENTITY_ID, CONF_SCAN_INTERVAL
from homeassistant.helpers import config_per_platform
from homeassistant.helpers.entity import generate_entity_id
from homeassistant.helpers.event import track_utc_time_change
from homeassistant.helpers.service import extract_entity_ids

DEFAULT_SCAN_INTERVAL = 15


class EntityComponent(object):
    """Helper class that will help a component manage its entities."""

    # pylint: disable=too-many-instance-attributes
    # pylint: disable=too-many-arguments
    def __init__(self, logger, domain, hass,
                 scan_interval=DEFAULT_SCAN_INTERVAL,
                 discovery_platforms=None, group_name=None):
        """Initialize an entity component."""
        self.logger = logger
        self.hass = hass

        self.domain = domain
        self.entity_id_format = domain + '.{}'
        self.scan_interval = scan_interval
        self.discovery_platforms = discovery_platforms
        self.group_name = group_name

        self.entities = {}
        self.group = None
        self.is_polling = False

        self.config = None
        self.lock = Lock()

        self.add_entities = EntityPlatform(self,
                                           self.scan_interval).add_entities

    def setup(self, config):
        """Set up a full entity component.

        Loads the platforms from the config and will listen for supported
        discovered platforms.
        """
        self.config = config

        # Look in config for Domain, Domain 2, Domain 3 etc and load them
        for p_type, p_config in \
                config_per_platform(config, self.domain, self.logger):

            self._setup_platform(p_type, p_config)

        if self.discovery_platforms:
            discovery.listen(
                self.hass, self.discovery_platforms.keys(),
                lambda service, info:
                self._setup_platform(self.discovery_platforms[service], {},
                                     info))

    def extract_from_service(self, service):
        """Extract all known entities from a service call.

        Will return all entities if no entities specified in call.
        Will return an empty list if entities specified but unknown.
        """
        with self.lock:
            if ATTR_ENTITY_ID not in service.data:
                return list(self.entities.values())

            return [self.entities[entity_id] for entity_id
                    in extract_entity_ids(self.hass, service)
                    if entity_id in self.entities]

    def _setup_platform(self, platform_type, platform_config,
                        discovery_info=None):
        """Setup a platform for this component."""
        platform = prepare_setup_platform(
            self.hass, self.config, self.domain, platform_type)

        if platform is None:
            return

        try:
            # Config > Platform > Component
            scan_interval = platform_config.get(
                CONF_SCAN_INTERVAL,
                getattr(platform, 'SCAN_INTERVAL', self.scan_interval))
            platform.setup_platform(
                self.hass, platform_config,
                EntityPlatform(self, scan_interval).add_entities,
                discovery_info)
            platform_name = '{}.{}'.format(self.domain, platform_type)
            self.hass.config.components.append(platform_name)
        except Exception:  # pylint: disable=broad-except
            self.logger.exception(
                'Error while setting up platform %s', platform_type)
            return

    def add_entity(self, entity):
        """Add entity to component."""
        if entity is None or entity in self.entities.values():
            return False

        entity.hass = self.hass

        if getattr(entity, 'entity_id', None) is None:
            entity.entity_id = generate_entity_id(
                self.entity_id_format, entity.name,
                self.entities.keys())

        self.entities[entity.entity_id] = entity
        entity.update_ha_state()

        return True

    def update_group(self):
        """Set up and/or update component group."""
        if self.group is None and self.group_name is not None:
            self.group = group.Group(self.hass, self.group_name,
                                     user_defined=False)

        if self.group is not None:
            self.group.update_tracked_entity_ids(self.entities.keys())


class EntityPlatform(object):
    """Keep track of entities for a single platform."""

    # pylint: disable=too-few-public-methods
    def __init__(self, component, scan_interval):
        """Initalize the entity platform."""
        self.component = component
        self.scan_interval = scan_interval
        self.platform_entities = []
        self.is_polling = False

    def add_entities(self, new_entities):
        """Add entities for a single platform."""
        with self.component.lock:
            for entity in new_entities:
                if self.component.add_entity(entity):
                    self.platform_entities.append(entity)

            self.component.update_group()

            if self.is_polling or \
               not any(entity.should_poll for entity
                       in self.platform_entities):
                return

            self.is_polling = True

            track_utc_time_change(
                self.component.hass, self._update_entity_states,
                second=range(0, 60, self.scan_interval))

    def _update_entity_states(self, now):
        """Update the states of all the polling entities."""
        with self.component.lock:
            # We copy the entities because new entities might be detected
            # during state update causing deadlocks.
            entities = list(entity for entity in self.platform_entities
                            if entity.should_poll)

        for entity in entities:
            entity.update_ha_state(True)