"""
Event parser and human readable log generator.

For more details about this component, please refer to the documentation at
https://home-assistant.io/components/logbook/
"""
import logging
import re
from datetime import timedelta
from itertools import groupby

import voluptuous as vol

import homeassistant.helpers.config_validation as cv
import homeassistant.util.dt as dt_util
from homeassistant.components import recorder, sun
from homeassistant.components.http import HomeAssistantView
from homeassistant.const import (EVENT_HOMEASSISTANT_START,
                                 EVENT_HOMEASSISTANT_STOP, EVENT_STATE_CHANGED,
                                 STATE_NOT_HOME, STATE_OFF, STATE_ON)
from homeassistant.core import DOMAIN as HA_DOMAIN
from homeassistant.core import State
from homeassistant.helpers import template
from homeassistant.helpers.entity import split_entity_id

DOMAIN = "logbook"
DEPENDENCIES = ['recorder', 'http']

URL_LOGBOOK = re.compile(r'/api/logbook(?:/(?P<date>\d{4}-\d{1,2}-\d{1,2})|)')

_LOGGER = logging.getLogger(__name__)

EVENT_LOGBOOK_ENTRY = 'logbook_entry'

GROUP_BY_MINUTES = 15

ATTR_NAME = 'name'
ATTR_MESSAGE = 'message'
ATTR_DOMAIN = 'domain'
ATTR_ENTITY_ID = 'entity_id'

LOG_MESSAGE_SCHEMA = vol.Schema({
    vol.Required(ATTR_NAME): cv.string,
    vol.Required(ATTR_MESSAGE): cv.string,
    vol.Optional(ATTR_DOMAIN): cv.slug,
    vol.Optional(ATTR_ENTITY_ID): cv.entity_id,
})


def log_entry(hass, name, message, domain=None, entity_id=None):
    """Add an entry to the logbook."""
    data = {
        ATTR_NAME: name,
        ATTR_MESSAGE: message
    }

    if domain is not None:
        data[ATTR_DOMAIN] = domain
    if entity_id is not None:
        data[ATTR_ENTITY_ID] = entity_id
    hass.bus.fire(EVENT_LOGBOOK_ENTRY, data)


def setup(hass, config):
    """Listen for download events to download files."""
    def log_message(service):
        """Handle sending notification message service calls."""
        message = service.data[ATTR_MESSAGE]
        name = service.data[ATTR_NAME]
        domain = service.data.get(ATTR_DOMAIN)
        entity_id = service.data.get(ATTR_ENTITY_ID)

        message = template.render(hass, message)
        log_entry(hass, name, message, domain, entity_id)

    hass.wsgi.register_view(LogbookView)

    hass.services.register(DOMAIN, 'log', log_message,
                           schema=LOG_MESSAGE_SCHEMA)
    return True


class LogbookView(HomeAssistantView):
    """Handle logbook view requests."""

    url = '/api/logbook'
    name = 'api:logbook'
    extra_urls = ['/api/logbook/<date:date>']

    def get(self, request, date=None):
        """Retrieve logbook entries."""
        if date:
            start_day = dt_util.start_of_local_day(date)
        else:
            start_day = dt_util.start_of_local_day()

        start_day = dt_util.as_utc(start_day)
        end_day = start_day + timedelta(days=1)

        events = recorder.get_model('Events')
        query = recorder.query('Events').filter(
            (events.time_fired > start_day) &
            (events.time_fired < end_day))
        events = recorder.execute(query)

        return self.json(humanify(events))


class Entry(object):
    """A human readable version of the log."""

    # pylint: disable=too-many-arguments, too-few-public-methods
    def __init__(self, when=None, name=None, message=None, domain=None,
                 entity_id=None):
        """Initialize the entry."""
        self.when = when
        self.name = name
        self.message = message
        self.domain = domain
        self.entity_id = entity_id

    def as_dict(self):
        """Convert entry to a dict to be used within JSON."""
        return {
            'when': self.when,
            'name': self.name,
            'message': self.message,
            'domain': self.domain,
            'entity_id': self.entity_id,
        }


def humanify(events):
    """Generator that converts a list of events into Entry objects.

    Will try to group events if possible:
     - if 2+ sensor updates in GROUP_BY_MINUTES, show last
     - if home assistant stop and start happen in same minute call it restarted
    """
    # pylint: disable=too-many-branches
    # Group events in batches of GROUP_BY_MINUTES
    for _, g_events in groupby(
            events,
            lambda event: event.time_fired.minute // GROUP_BY_MINUTES):

        events_batch = list(g_events)

        # Keep track of last sensor states
        last_sensor_event = {}

        # Group HA start/stop events
        # Maps minute of event to 1: stop, 2: stop + start
        start_stop_events = {}

        # Process events
        for event in events_batch:
            if event.event_type == EVENT_STATE_CHANGED:
                entity_id = event.data.get('entity_id')

                if entity_id is None:
                    continue

                if entity_id.startswith('sensor.'):
                    last_sensor_event[entity_id] = event

            elif event.event_type == EVENT_HOMEASSISTANT_STOP:
                if event.time_fired.minute in start_stop_events:
                    continue

                start_stop_events[event.time_fired.minute] = 1

            elif event.event_type == EVENT_HOMEASSISTANT_START:
                if event.time_fired.minute not in start_stop_events:
                    continue

                start_stop_events[event.time_fired.minute] = 2

        # Yield entries
        for event in events_batch:
            if event.event_type == EVENT_STATE_CHANGED:

                # Do not report on new entities
                if 'old_state' not in event.data:
                    continue

                to_state = State.from_dict(event.data.get('new_state'))

                # If last_changed != last_updated only attributes have changed
                # we do not report on that yet. Also filter auto groups.
                if not to_state or \
                   to_state.last_changed != to_state.last_updated or \
                   to_state.domain == 'group' and \
                   to_state.attributes.get('auto', False):
                    continue

                domain = to_state.domain

                # Skip all but the last sensor state
                if domain == 'sensor' and \
                   event != last_sensor_event[to_state.entity_id]:
                    continue

                yield Entry(
                    event.time_fired,
                    name=to_state.name,
                    message=_entry_message_from_state(domain, to_state),
                    domain=domain,
                    entity_id=to_state.entity_id)

            elif event.event_type == EVENT_HOMEASSISTANT_START:
                if start_stop_events.get(event.time_fired.minute) == 2:
                    continue

                yield Entry(
                    event.time_fired, "Home Assistant", "started",
                    domain=HA_DOMAIN)

            elif event.event_type == EVENT_HOMEASSISTANT_STOP:
                if start_stop_events.get(event.time_fired.minute) == 2:
                    action = "restarted"
                else:
                    action = "stopped"

                yield Entry(
                    event.time_fired, "Home Assistant", action,
                    domain=HA_DOMAIN)

            elif event.event_type.lower() == EVENT_LOGBOOK_ENTRY:
                domain = event.data.get(ATTR_DOMAIN)
                entity_id = event.data.get(ATTR_ENTITY_ID)
                if domain is None and entity_id is not None:
                    try:
                        domain = split_entity_id(str(entity_id))[0]
                    except IndexError:
                        pass

                yield Entry(
                    event.time_fired, event.data.get(ATTR_NAME),
                    event.data.get(ATTR_MESSAGE), domain,
                    entity_id)


def _entry_message_from_state(domain, state):
    """Convert a state to a message for the logbook."""
    # We pass domain in so we don't have to split entity_id again
    # pylint: disable=too-many-return-statements
    if domain == 'device_tracker':
        if state.state == STATE_NOT_HOME:
            return 'is away'
        else:
            return 'is at {}'.format(state.state)

    elif domain == 'sun':
        if state.state == sun.STATE_ABOVE_HORIZON:
            return 'has risen'
        else:
            return 'has set'

    elif state.state == STATE_ON:
        # Future: combine groups and its entity entries ?
        return "turned on"

    elif state.state == STATE_OFF:
        return "turned off"

    return "changed to {}".format(state.state)
