"""
Support for Google - Calendar Event Devices.

For more details about this platform, please refer to the documentation at
https://home-assistant.io/components/google/

NOTE TO OTHER DEVELOPERS: IF YOU ADD MORE SCOPES TO THE OAUTH THAN JUST
CALENDAR THEN USERS WILL NEED TO DELETE THEIR TOKEN_FILE. THEY WILL LOSE THEIR
REFRESH_TOKEN PIECE WHEN RE-AUTHENTICATING TO ADD MORE API ACCESS
IT'S BEST TO JUST HAVE SEPARATE OAUTH FOR DIFFERENT PIECES OF GOOGLE
"""
import logging
import os
import yaml

import voluptuous as vol
from voluptuous.error import Error as VoluptuousError

import homeassistant.helpers.config_validation as cv
from homeassistant.setup import setup_component
from homeassistant.helpers import discovery
from homeassistant.helpers.entity import generate_entity_id
from homeassistant.helpers.event import track_time_change
from homeassistant.util import convert, dt

REQUIREMENTS = [
    'google-api-python-client==1.6.4',
    'oauth2client==4.0.0',
]

_LOGGER = logging.getLogger(__name__)

DOMAIN = 'google'
ENTITY_ID_FORMAT = DOMAIN + '.{}'

CONF_CLIENT_ID = 'client_id'
CONF_CLIENT_SECRET = 'client_secret'
CONF_TRACK_NEW = 'track_new_calendar'

CONF_CAL_ID = 'cal_id'
CONF_DEVICE_ID = 'device_id'
CONF_NAME = 'name'
CONF_ENTITIES = 'entities'
CONF_TRACK = 'track'
CONF_SEARCH = 'search'
CONF_OFFSET = 'offset'

DEFAULT_CONF_TRACK_NEW = True
DEFAULT_CONF_OFFSET = '!!'

NOTIFICATION_ID = 'google_calendar_notification'
NOTIFICATION_TITLE = 'Google Calendar Setup'
GROUP_NAME_ALL_CALENDARS = "Google Calendar Sensors"

SERVICE_SCAN_CALENDARS = 'scan_for_calendars'
SERVICE_FOUND_CALENDARS = 'found_calendar'

DATA_INDEX = 'google_calendars'

YAML_DEVICES = '{}_calendars.yaml'.format(DOMAIN)
SCOPES = 'https://www.googleapis.com/auth/calendar.readonly'

TOKEN_FILE = '.{}.token'.format(DOMAIN)

CONFIG_SCHEMA = vol.Schema({
    DOMAIN: vol.Schema({
        vol.Required(CONF_CLIENT_ID): cv.string,
        vol.Required(CONF_CLIENT_SECRET): cv.string,
        vol.Optional(CONF_TRACK_NEW): cv.boolean,
    })
}, extra=vol.ALLOW_EXTRA)

_SINGLE_CALSEARCH_CONFIG = vol.Schema({
    vol.Required(CONF_NAME): cv.string,
    vol.Required(CONF_DEVICE_ID): cv.string,
    vol.Optional(CONF_TRACK): cv.boolean,
    vol.Optional(CONF_SEARCH): vol.Any(cv.string, None),
    vol.Optional(CONF_OFFSET): cv.string,
})

DEVICE_SCHEMA = vol.Schema({
    vol.Required(CONF_CAL_ID): cv.string,
    vol.Required(CONF_ENTITIES, None):
        vol.All(cv.ensure_list, [_SINGLE_CALSEARCH_CONFIG]),
}, extra=vol.ALLOW_EXTRA)


def do_authentication(hass, config):
    """Notify user of actions and authenticate.

    Notify user of user_code and verification_url then poll
    until we have an access token.
    """
    from oauth2client.client import (
        OAuth2WebServerFlow,
        OAuth2DeviceCodeError,
        FlowExchangeError
    )
    from oauth2client.file import Storage

    oauth = OAuth2WebServerFlow(
        client_id=config[CONF_CLIENT_ID],
        client_secret=config[CONF_CLIENT_SECRET],
        scope='https://www.googleapis.com/auth/calendar.readonly',
        redirect_uri='Home-Assistant.io',
    )

    try:
        dev_flow = oauth.step1_get_device_and_user_codes()
    except OAuth2DeviceCodeError as err:
        hass.components.persistent_notification.create(
            'Error: {}<br />You will need to restart hass after fixing.'
            ''.format(err),
            title=NOTIFICATION_TITLE,
            notification_id=NOTIFICATION_ID)
        return False

    hass.components.persistent_notification.create(
        'In order to authorize Home-Assistant to view your calendars '
        'you must visit: <a href="{}" target="_blank">{}</a> and enter '
        'code: {}'.format(dev_flow.verification_url,
                          dev_flow.verification_url,
                          dev_flow.user_code),
        title=NOTIFICATION_TITLE, notification_id=NOTIFICATION_ID
    )

    def step2_exchange(now):
        """Keep trying to validate the user_code until it expires."""
        if now >= dt.as_local(dev_flow.user_code_expiry):
            hass.components.persistent_notification.create(
                'Authenication code expired, please restart '
                'Home-Assistant and try again',
                title=NOTIFICATION_TITLE,
                notification_id=NOTIFICATION_ID)
            listener()

        try:
            credentials = oauth.step2_exchange(device_flow_info=dev_flow)
        except FlowExchangeError:
            # not ready yet, call again
            return

        storage = Storage(hass.config.path(TOKEN_FILE))
        storage.put(credentials)
        do_setup(hass, config)
        listener()
        hass.components.persistent_notification.create(
            'We are all setup now. Check {} for calendars that have '
            'been found'.format(YAML_DEVICES),
            title=NOTIFICATION_TITLE, notification_id=NOTIFICATION_ID)

    listener = track_time_change(hass, step2_exchange,
                                 second=range(0, 60, dev_flow.interval))

    return True


def setup(hass, config):
    """Set up the Google platform."""
    if DATA_INDEX not in hass.data:
        hass.data[DATA_INDEX] = {}

    conf = config.get(DOMAIN, {})

    token_file = hass.config.path(TOKEN_FILE)
    if not os.path.isfile(token_file):
        do_authentication(hass, conf)
    else:
        do_setup(hass, conf)

    return True


def setup_services(hass, track_new_found_calendars, calendar_service):
    """Set up the service listeners."""
    def _found_calendar(call):
        """Check if we know about a calendar and generate PLATFORM_DISCOVER."""
        calendar = get_calendar_info(hass, call.data)
        if hass.data[DATA_INDEX].get(calendar[CONF_CAL_ID], None) is not None:
            return

        hass.data[DATA_INDEX].update({calendar[CONF_CAL_ID]: calendar})

        update_config(
            hass.config.path(YAML_DEVICES),
            hass.data[DATA_INDEX][calendar[CONF_CAL_ID]]
        )

        discovery.load_platform(hass, 'calendar', DOMAIN,
                                hass.data[DATA_INDEX][calendar[CONF_CAL_ID]])

    hass.services.register(
        DOMAIN, SERVICE_FOUND_CALENDARS, _found_calendar,
        None, schema=None)

    def _scan_for_calendars(service):
        """Scan for new calendars."""
        service = calendar_service.get()
        cal_list = service.calendarList()  # pylint: disable=no-member
        calendars = cal_list.list().execute()['items']
        for calendar in calendars:
            calendar['track'] = track_new_found_calendars
            hass.services.call(DOMAIN, SERVICE_FOUND_CALENDARS,
                               calendar)

    hass.services.register(
        DOMAIN, SERVICE_SCAN_CALENDARS,
        _scan_for_calendars,
        None, schema=None)
    return True


def do_setup(hass, config):
    """Run the setup after we have everything configured."""
    # Load calendars the user has configured
    hass.data[DATA_INDEX] = load_config(hass.config.path(YAML_DEVICES))

    calendar_service = GoogleCalendarService(hass.config.path(TOKEN_FILE))
    track_new_found_calendars = convert(config.get(CONF_TRACK_NEW),
                                        bool, DEFAULT_CONF_TRACK_NEW)
    setup_services(hass, track_new_found_calendars, calendar_service)

    # Ensure component is loaded
    setup_component(hass, 'calendar', config)

    for calendar in hass.data[DATA_INDEX].values():
        discovery.load_platform(hass, 'calendar', DOMAIN, calendar)

    # Look for any new calendars
    hass.services.call(DOMAIN, SERVICE_SCAN_CALENDARS, None)
    return True


class GoogleCalendarService(object):
    """Calendar service interface to Google."""

    def __init__(self, token_file):
        """Init the Google Calendar service."""
        self.token_file = token_file

    def get(self):
        """Get the calendar service from the storage file token."""
        import httplib2
        from oauth2client.file import Storage
        from googleapiclient import discovery as google_discovery
        credentials = Storage(self.token_file).get()
        http = credentials.authorize(httplib2.Http())
        service = google_discovery.build(
            'calendar', 'v3', http=http, cache_discovery=False)
        return service


def get_calendar_info(hass, calendar):
    """Convert data from Google into DEVICE_SCHEMA."""
    calendar_info = DEVICE_SCHEMA({
        CONF_CAL_ID: calendar['id'],
        CONF_ENTITIES: [{
            CONF_TRACK: calendar['track'],
            CONF_NAME: calendar['summary'],
            CONF_DEVICE_ID: generate_entity_id(
                '{}', calendar['summary'], hass=hass),
        }]
    })
    return calendar_info


def load_config(path):
    """Load the google_calendar_devices.yaml."""
    calendars = {}
    try:
        with open(path) as file:
            data = yaml.safe_load(file)
            for calendar in data:
                try:
                    calendars.update({calendar[CONF_CAL_ID]:
                                      DEVICE_SCHEMA(calendar)})
                except VoluptuousError as exception:
                    # keep going
                    _LOGGER.warning("Calendar Invalid Data: %s", exception)
    except FileNotFoundError:
        # When YAML file could not be loaded/did not contain a dict
        return {}

    return calendars


def update_config(path, calendar):
    """Write the google_calendar_devices.yaml."""
    with open(path, 'a') as out:
        out.write('\n')
        yaml.dump([calendar], out, default_flow_style=False)
