# -*- coding: utf-8 -*-
# Part of Odoo. See LICENSE file for full copyright and licensing details.

import logging
import math
from datetime import datetime, timedelta
from itertools import repeat
from werkzeug.urls import url_parse

import pytz
import uuid

from odoo import api, fields, models, Command
from odoo.osv.expression import AND
from odoo.addons.base.models.res_partner import _tz_get
from odoo.addons.calendar.models.calendar_attendee import Attendee
from odoo.addons.calendar.models.calendar_recurrence import (
    weekday_to_field,
    RRULE_TYPE_SELECTION,
    END_TYPE_SELECTION,
    MONTH_BY_SELECTION,
    WEEKDAY_SELECTION,
    BYDAY_SELECTION
)
from odoo.tools.translate import _
from odoo.tools.misc import get_lang
from odoo.tools import pycompat, html2plaintext, is_html_empty, single_email_re
from odoo.exceptions import UserError, ValidationError

_logger = logging.getLogger(__name__)

try:
    import vobject
except ImportError:
    _logger.warning("`vobject` Python module not found, iCal file generation disabled. Consider installing this module if you want to generate iCal files")
    vobject = None

SORT_ALIASES = {
    'start': 'sort_start',
    'start_date': 'sort_start',
}

RRULE_TYPE_SELECTION_UI = [
    ('daily', 'Daily'),
    ('weekly', 'Weekly'),
    ('monthly', 'Monthly'),
    ('yearly', 'Yearly'),
    ('custom', 'Custom')
]

def get_weekday_occurence(date):
    """
    :returns: ocurrence

    >>> get_weekday_occurence(date(2019, 12, 17))
    3  # third Tuesday of the month

    >>> get_weekday_occurence(date(2019, 12, 25))
    -1  # last Friday of the month
    """
    occurence_in_month = math.ceil(date.day/7)
    if occurence_in_month in {4, 5}:  # fourth or fifth week on the month -> last
        return -1
    return occurence_in_month


class Meeting(models.Model):
    _name = 'calendar.event'
    _description = "Calendar Event"
    _order = "start desc"
    _inherit = ["mail.thread"]
    _systray_view = 'calendar'

    DISCUSS_ROUTE = 'calendar/join_videocall'

    @api.model
    def get_state_selections(self):
        return Attendee.STATE_SELECTION

    @api.model
    def default_get(self, fields):
        # super default_model='crm.lead' for easier use in addons
        if self.env.context.get('default_res_model') and not self.env.context.get('default_res_model_id'):
            self = self.with_context(
                default_res_model_id=self.env['ir.model']._get_id(self.env.context['default_res_model'])
            )

        defaults = super(Meeting, self).default_get(fields)

        # support active_model / active_id as replacement of default_* if not already given
        if 'res_model_id' not in defaults and 'res_model_id' in fields and \
                self.env.context.get('active_model') and self.env.context['active_model'] != 'calendar.event':
            defaults['res_model_id'] = self.env['ir.model']._get_id(self.env.context['active_model'])
            defaults['res_model'] = self.env.context.get('active_model')
        if 'res_id' not in defaults and 'res_id' in fields and \
                defaults.get('res_model_id') and self.env.context.get('active_id'):
            defaults['res_id'] = self.env.context['active_id']

        return defaults

    @api.model
    def _default_partners(self):
        """ When active_model is res.partner, the current partners should be attendees """
        partners = self.env.user.partner_id
        active_id = self._context.get('active_id')
        if self._context.get('active_model') == 'res.partner' and active_id and active_id not in partners.ids:
                partners |= self.env['res.partner'].browse(active_id)
        return partners

    @api.model
    def _default_start(self):
        now = fields.Datetime.now()
        return now + (datetime.min - now) % timedelta(minutes=30)

    @api.model
    def _default_stop(self):
        now = fields.Datetime.now()
        start = now + (datetime.min - now) % timedelta(minutes=30)
        return start + timedelta(hours=1)

    # description
    name = fields.Char('Meeting Subject', required=True)
    description = fields.Html('Description')
    user_id = fields.Many2one('res.users', 'Organizer', default=lambda self: self.env.user)
    partner_id = fields.Many2one(
        'res.partner', string='Scheduled by', related='user_id.partner_id', readonly=True)
    location = fields.Char('Location', tracking=True)
    videocall_location = fields.Char('Meeting URL', compute='_compute_videocall_location', store=True, copy=True)
    access_token = fields.Char('Invitation Token', store=True, copy=False, index=True)
    videocall_source = fields.Selection([('discuss', 'Discuss'), ('custom', 'Custom')], compute='_compute_videocall_source')
    videocall_channel_id = fields.Many2one('discuss.channel', 'Discuss Channel')
    # visibility
    privacy = fields.Selection(
        [('public', 'Public'),
         ('private', 'Private'),
         ('confidential', 'Only internal users')],
        'Privacy', default='public', required=True,
        help="People to whom this event will be visible.")
    show_as = fields.Selection(
        [('free', 'Available'),
         ('busy', 'Busy')], 'Show as', default='busy', required=True,
        help="If the time is shown as 'busy', this event will be visible to other people with either the full \
        information or simply 'busy' written depending on its privacy. Use this option to let other people know \
        that you are unavailable during that period of time. \n If the event is shown as 'free', other users know \
        that you are available during that period of time.")
    is_highlighted = fields.Boolean(
        compute='_compute_is_highlighted', string='Is the Event Highlighted')
    is_organizer_alone = fields.Boolean(compute='_compute_is_organizer_alone', string="Is the Organizer Alone",
        help="""Check if the organizer is alone in the event, i.e. if the organizer is the only one that hasn't declined
        the event (only if the organizer is not the only attendee)""")
    # filtering
    active = fields.Boolean(
        'Active', default=True,
        tracking=True,
        help="If the active field is set to false, it will allow you to hide the event alarm information without removing it.")
    categ_ids = fields.Many2many(
        'calendar.event.type', 'meeting_category_rel', 'event_id', 'type_id', 'Tags')
    # timing
    start = fields.Datetime(
        'Start', required=True, tracking=True, default=_default_start,
        help="Start date of an event, without time for full days events")
    stop = fields.Datetime(
        'Stop', required=True, tracking=True, default=_default_stop,
        compute='_compute_stop', readonly=False, store=True,
        help="Stop date of an event, without time for full days events")
    display_time = fields.Char('Event Time', compute='_compute_display_time')
    allday = fields.Boolean('All Day', default=False)
    start_date = fields.Date(
        'Start Date', store=True, tracking=True,
        compute='_compute_dates', inverse='_inverse_dates')
    stop_date = fields.Date(
        'End Date', store=True, tracking=True,
        compute='_compute_dates', inverse='_inverse_dates')
    duration = fields.Float('Duration', compute='_compute_duration', store=True, readonly=False)
    # linked document
    res_id = fields.Many2oneReference('Document ID', model_field='res_model')
    res_model_id = fields.Many2one('ir.model', 'Document Model', ondelete='cascade')
    res_model = fields.Char(
        'Document Model Name', related='res_model_id.model', readonly=True, store=True)
    res_model_name = fields.Char(related='res_model_id.name')
    # messaging
    activity_ids = fields.One2many('mail.activity', 'calendar_event_id', string='Activities')
    # attendees
    attendee_ids = fields.One2many(
        'calendar.attendee', 'event_id', 'Participant')
    current_attendee = fields.Many2one("calendar.attendee", compute="_compute_current_attendee", search="_search_current_attendee")
    current_status = fields.Selection(string="Attending?", related="current_attendee.state", readonly=False)
    should_show_status = fields.Boolean(compute="_compute_should_show_status")
    partner_ids = fields.Many2many(
        'res.partner', 'calendar_event_res_partner_rel',
        string='Attendees', default=_default_partners)
    invalid_email_partner_ids = fields.Many2many('res.partner', compute='_compute_invalid_email_partner_ids')
    # alarms
    alarm_ids = fields.Many2many(
        'calendar.alarm', 'calendar_alarm_calendar_event_rel',
        string='Reminders', ondelete="restrict",
        help="Notifications sent to all attendees to remind of the meeting.")
    # RECURRENCE FIELD
    recurrency = fields.Boolean('Recurrent')
    recurrence_id = fields.Many2one(
        'calendar.recurrence', string="Recurrence Rule")
    follow_recurrence = fields.Boolean(default=False) # Indicates if an event follows the recurrence, i.e. is not an exception
    recurrence_update = fields.Selection([
        ('self_only', "This event"),
        ('future_events', "This and following events"),
        ('all_events', "All events"),
    ], store=False, copy=False, default='self_only',
       help="Choose what to do with other events in the recurrence. Updating All Events is not allowed when dates or time is modified")
    # Those field are pseudo-related fields of recurrence_id.
    # They can't be "real" related fields because it should work at record creation
    # when recurrence_id is not created yet.
    # If some of these fields are set and recurrence_id does not exists,
    # a `calendar.recurrence.rule` will be dynamically created.
    rrule = fields.Char('Recurrent Rule', compute='_compute_recurrence', readonly=False)
    rrule_type_ui = fields.Selection(RRULE_TYPE_SELECTION_UI, string='Repeat',
                                     compute="_compute_rrule_type_ui",
                                     readonly=False,
                                     help="Let the event automatically repeat at that interval")
    rrule_type = fields.Selection(RRULE_TYPE_SELECTION, string='Recurrence',
                                  help="Let the event automatically repeat at that interval",
                                  compute='_compute_recurrence', readonly=False)
    event_tz = fields.Selection(
        _tz_get, string='Timezone', compute='_compute_recurrence', readonly=False)
    end_type = fields.Selection(
        END_TYPE_SELECTION, string='Recurrence Termination',
        compute='_compute_recurrence', readonly=False)
    interval = fields.Integer(
        string='Repeat On', compute='_compute_recurrence', readonly=False,
        help="Repeat every (Days/Week/Month/Year)")
    count = fields.Integer(
        string='Number of Repetitions', help="Repeat x times", compute='_compute_recurrence', readonly=False)
    mon = fields.Boolean(compute='_compute_recurrence', readonly=False)
    tue = fields.Boolean(compute='_compute_recurrence', readonly=False)
    wed = fields.Boolean(compute='_compute_recurrence', readonly=False)
    thu = fields.Boolean(compute='_compute_recurrence', readonly=False)
    fri = fields.Boolean(compute='_compute_recurrence', readonly=False)
    sat = fields.Boolean(compute='_compute_recurrence', readonly=False)
    sun = fields.Boolean(compute='_compute_recurrence', readonly=False)
    month_by = fields.Selection(
        MONTH_BY_SELECTION, string='Option', compute='_compute_recurrence', readonly=False)
    day = fields.Integer('Date of month', compute='_compute_recurrence', readonly=False)
    weekday = fields.Selection(WEEKDAY_SELECTION, compute='_compute_recurrence', readonly=False)
    byday = fields.Selection(BYDAY_SELECTION, string="By day", compute='_compute_recurrence', readonly=False)
    until = fields.Date(compute='_compute_recurrence', readonly=False)
    # UI Fields.
    display_description = fields.Boolean(compute='_compute_display_description')
    attendees_count = fields.Integer(compute='_compute_attendees_count')
    accepted_count = fields.Integer(compute='_compute_attendees_count')
    declined_count = fields.Integer(compute='_compute_attendees_count')
    tentative_count = fields.Integer(compute='_compute_attendees_count')
    awaiting_count = fields.Integer(compute="_compute_attendees_count")
    user_can_edit = fields.Boolean(compute='_compute_user_can_edit')

    @api.depends("attendee_ids")
    def _compute_should_show_status(self):
        for event in self:
            event.should_show_status = event.current_attendee and any(attendee.partner_id != self.env.user.partner_id for attendee in event.attendee_ids)

    @api.depends('attendee_ids', 'attendee_ids.state')
    def _compute_current_attendee(self):
        for event in self:
            current_attendee = event.attendee_ids.filtered(lambda attendee: attendee.partner_id == self.env.user.partner_id)
            event.current_attendee = current_attendee and current_attendee[0]

    def _search_current_attendee(self, operator, value):
        return [("id", operator, value)]

    @api.depends('attendee_ids', 'attendee_ids.state', 'partner_ids')
    def _compute_attendees_count(self):
        for event in self:
            count_event = {}
            for attendee in event.attendee_ids:
                count_event[attendee.state] = count_event.get(attendee.state, 0) + 1

            accepted_count = count_event.get('accepted', 0)
            declined_count = count_event.get('declined', 0)
            tentative_count = count_event.get('tentative', 0)
            attendees_count = len(event.partner_ids)
            event.update({
                'accepted_count': accepted_count,
                'declined_count': declined_count,
                'tentative_count': tentative_count,
                'attendees_count': attendees_count,
                'awaiting_count': attendees_count - accepted_count - declined_count - tentative_count
            })

    @api.depends('partner_ids')
    @api.depends_context('uid')
    def _compute_user_can_edit(self):
        for event in self:
            event.user_can_edit = self.env.user in event.partner_ids.user_ids + event.user_id

    @api.depends('attendee_ids')
    def _compute_invalid_email_partner_ids(self):
        for event in self:
            event.invalid_email_partner_ids = event.partner_ids.filtered(
                lambda a: not (a.email and single_email_re.match(a.email))
            )

    def _compute_is_highlighted(self):
        if self.env.context.get('active_model') == 'res.partner':
            partner_id = self.env.context.get('active_id')
            for event in self:
                if event.partner_ids.filtered(lambda s: s.id == partner_id):
                    event.is_highlighted = True
                else:
                    event.is_highlighted = False
        else:
            for event in self:
                event.is_highlighted = False

    @api.depends('partner_id', 'attendee_ids')
    def _compute_is_organizer_alone(self):
        """
            Check if the organizer of the event is the only one who has accepted the event.
            It does not apply if the organizer is the only attendee of the event because it
            would represent a personnal event.
            The goal of this field is to highlight to the user that the others attendees are
            not available for this event.
        """
        for event in self:
            organizer = event.attendee_ids.filtered(lambda a: a.partner_id == event.partner_id)
            all_declined = not any((event.attendee_ids - organizer).filtered(lambda a: a.state != 'declined'))
            event.is_organizer_alone = len(event.attendee_ids) > 1 and all_declined

    def _compute_display_time(self):
        for meeting in self:
            meeting.display_time = self._get_display_time(meeting.start, meeting.stop, meeting.duration, meeting.allday)

    @api.depends('allday', 'start', 'stop')
    def _compute_dates(self):
        """ Adapt the value of start_date(time)/stop_date(time)
            according to start/stop fields and allday. Also, compute
            the duration for not allday meeting ; otherwise the
            duration is set to zero, since the meeting last all the day.
        """
        for meeting in self:
            if meeting.allday and meeting.start and meeting.stop:
                meeting.start_date = meeting.start.date()
                meeting.stop_date = meeting.stop.date()
            else:
                meeting.start_date = False
                meeting.stop_date = False

    @api.depends('stop', 'start')
    def _compute_duration(self):
        for event in self:
            event.duration = self._get_duration(event.start, event.stop)

    @api.depends('start', 'duration')
    def _compute_stop(self):
        # stop and duration fields both depends on the start field.
        # But they also depends on each other.
        # When start is updated, we want to update the stop datetime based on
        # the *current* duration. In other words, we want: change start => keep the duration fixed and
        # recompute stop accordingly.
        # However, while computing stop, duration is marked to be recomputed. Calling `event.duration` would trigger
        # its recomputation. To avoid this we manually mark the field as computed.
        duration_field = self._fields['duration']
        self.env.remove_to_compute(duration_field, self)
        for event in self:
            # Round the duration (in hours) to the minute to avoid weird situations where the event
            # stops at 4:19:59, later displayed as 4:19.
            event.stop = event.start and event.start + timedelta(minutes=round((event.duration or 1.0) * 60))
            if event.allday:
                event.stop -= timedelta(seconds=1)

    @api.onchange('start_date', 'stop_date')
    def _onchange_date(self):
        """ This onchange is required for cases where the stop/start is False and we set an allday event.
            The inverse method is not called in this case because start_date/stop_date are not used in any
            compute/related, so we need an onchange to set the start/stop values in the form view
        """
        for event in self:
            if event.stop_date and event.start_date:
                event.with_context(is_calendar_event_new=True).write({
                    'start': fields.Datetime.from_string(event.start_date).replace(hour=8),
                    'stop': fields.Datetime.from_string(event.stop_date).replace(hour=18),
                })

    def _inverse_dates(self):
        """ This method is used to set the start and stop values of all day events.
            The calendar view needs date_start and date_stop values to display correctly the allday events across
            several days. As the user edit the {start,stop}_date fields when allday is true,
            this inverse method is needed to update the  start/stop value and have a relevant calendar view.
        """
        for meeting in self:
            if meeting.allday:

                # Convention break:
                # stop and start are NOT in UTC in allday event
                # in this case, they actually represent a date
                # because fullcalendar just drops times for full day events.
                # i.e. Christmas is on 25/12 for everyone
                # even if people don't celebrate it simultaneously
                enddate = fields.Datetime.from_string(meeting.stop_date)
                enddate = enddate.replace(hour=18)

                startdate = fields.Datetime.from_string(meeting.start_date)
                startdate = startdate.replace(hour=8)  # Set 8 AM

                meeting.write({
                    'start': startdate.replace(tzinfo=None),
                    'stop': enddate.replace(tzinfo=None)
                })

    @api.constrains('start', 'stop', 'start_date', 'stop_date')
    def _check_closing_date(self):
        for meeting in self:
            if not meeting.allday and meeting.start and meeting.stop and meeting.stop < meeting.start:
                raise ValidationError(
                    _('The ending date and time cannot be earlier than the starting date and time.') + '\n' +
                    _("Meeting '%(name)s' starts '%(start_datetime)s' and ends '%(end_datetime)s'",
                      name=meeting.name,
                      start_datetime=meeting.start,
                      end_datetime=meeting.stop
                    )
                )
            if meeting.allday and meeting.start_date and meeting.stop_date and meeting.stop_date < meeting.start_date:
                raise ValidationError(
                    _('The ending date cannot be earlier than the starting date.') + '\n' +
                    _("Meeting '%(name)s' starts '%(start_datetime)s' and ends '%(end_datetime)s'",
                      name=meeting.name,
                      start_datetime=meeting.start,
                      end_datetime=meeting.stop
                    )
                )

    @api.depends('recurrence_id', 'recurrency')
    def _compute_rrule_type_ui(self):
        defaults = self.env["calendar.recurrence"].default_get(["interval", "rrule_type"])
        for event in self:
            if event.recurrency:
                if event.recurrence_id:
                    event.rrule_type_ui = 'custom' if event.recurrence_id.interval != 1 else (event.recurrence_id.rrule_type)
                else:
                    event.rrule_type_ui = defaults["rrule_type"]

    @api.depends('recurrence_id', 'recurrency', 'rrule_type_ui')
    def _compute_recurrence(self):
        recurrence_fields = self._get_recurrent_fields()
        false_values = {field: False for field in recurrence_fields}  # computes need to set a value
        defaults = self.env['calendar.recurrence'].default_get(recurrence_fields)
        default_rrule_values = self.recurrence_id.default_get(recurrence_fields)
        for event in self:
            if event.recurrency:
                current_rrule = (event.rrule_type if event.rrule_type_ui == "custom" else event.rrule_type_ui)
                event.update(defaults)  # default recurrence values are needed to correctly compute the recurrence params
                event_values = event._get_recurrence_params()
                rrule_values = {
                    field: event.recurrence_id[field]
                    for field in recurrence_fields
                    if event.recurrence_id[field]
                }
                rrule_values = rrule_values or default_rrule_values
                rrule_values['rrule_type'] = current_rrule or rrule_values.get('rrule_type') or defaults['rrule_type']
                event.update({**false_values, **defaults, **event_values, **rrule_values})
            else:
                event.update(false_values)

    @api.depends('description')
    def _compute_display_description(self):
        for event in self:
            event.display_description = not is_html_empty(event.description)

    @api.depends('videocall_source', 'access_token')
    def _compute_videocall_location(self):
        for event in self:
            if event.videocall_source == 'discuss':
                event._set_discuss_videocall_location()

    @api.model
    def _set_videocall_location(self, vals_list):
        for vals in vals_list:
            if not vals.get('videocall_location'):
                continue
            url = url_parse(vals['videocall_location'])
            if url.scheme in ('http', 'https'):
                continue
            # relative url to convert to absolute
            base = url_parse(self.get_base_url())
            vals['videocall_location'] = url.replace(scheme=base.scheme, netloc=base.netloc).to_url()

    @api.depends('videocall_location')
    def _compute_videocall_source(self):
        for event in self:
            if event.videocall_location and self.DISCUSS_ROUTE in event.videocall_location:
                event.videocall_source = 'discuss'
            else:
                event.videocall_source = 'custom'

    def _set_discuss_videocall_location(self):
        """
        This method sets the videocall_location to a discuss route.
        If no access_token exists for this event, we create one.
        Note that recurring events will have different access_tokens.
        This is done by design to prevent users not being able to join a discuss meeting because the base event of the recurrency was deleted.
        """
        if not self.access_token:
            self.access_token = uuid.uuid4().hex
        self.videocall_location = f"{self.get_base_url()}/{self.DISCUSS_ROUTE}/{self.access_token}"

    @api.model
    def get_discuss_videocall_location(self):
        access_token = uuid.uuid4().hex
        return f"{self.get_base_url()}/{self.DISCUSS_ROUTE}/{access_token}"

    # ------------------------------------------------------------
    # CRUD
    # ------------------------------------------------------------

    @api.model_create_multi
    def create(self, vals_list):
        # Prevent sending update notification when _inverse_dates is called
        self = self.with_context(is_calendar_event_new=True)
        defaults = self.default_get(['activity_ids', 'res_model_id', 'res_id', 'user_id', 'res_model', 'partner_ids'])

        vals_list = [  # Else bug with quick_create when we are filter on an other user
            dict(vals, user_id=defaults.get('user_id', self.env.user.id)) if not 'user_id' in vals else vals
            for vals in vals_list
        ]
        meeting_activity_type = self.env['mail.activity.type'].search([('category', '=', 'meeting')], limit=1)
        # get list of models ids and filter out None values directly
        model_ids = list(filter(None, {values.get('res_model_id', defaults.get('res_model_id')) for values in vals_list}))
        model_name = defaults.get('res_model')
        valid_activity_model_ids = model_name and self.env[model_name].sudo().browse(model_ids).filtered(lambda m: 'activity_ids' in m).ids or []
        if meeting_activity_type and not defaults.get('activity_ids'):
            for values in vals_list:
                # created from calendar: try to create an activity on the related record
                if values.get('activity_ids'):
                    continue
                res_model_id = values.get('res_model_id', defaults.get('res_model_id'))
                res_id = values.get('res_id', defaults.get('res_id'))
                user_id = values.get('user_id', defaults.get('user_id'))
                if not res_model_id or not res_id:
                    continue
                if res_model_id not in valid_activity_model_ids:
                    continue
                activity_vals = {
                    'res_model_id': res_model_id,
                    'res_id': res_id,
                    'activity_type_id': meeting_activity_type.id,
                }
                if user_id:
                    activity_vals['user_id'] = user_id
                values['activity_ids'] = [(0, 0, activity_vals)]
        self._set_videocall_location(vals_list)

        # Add commands to create attendees from partners (if present) if no attendee command
        # is already given (coming from Google event for example).
        # Automatically add the current partner when creating an event if there is none (happens when we quickcreate an event)
        default_partners_ids = defaults.get('partner_ids') or ([(4, self.env.user.partner_id.id)])
        vals_list = [
            dict(vals, attendee_ids=self._attendees_values(vals.get('partner_ids', default_partners_ids)))
            if not vals.get('attendee_ids')
            else vals
            for vals in vals_list
        ]
        recurrence_fields = self._get_recurrent_fields()
        recurring_vals = [vals for vals in vals_list if vals.get('recurrency')]
        other_vals = [vals for vals in vals_list if not vals.get('recurrency')]
        events = super().create(other_vals)

        for vals in recurring_vals:
            vals['follow_recurrence'] = True
        recurring_events = super().create(recurring_vals)
        events += recurring_events

        for event, vals in zip(recurring_events, recurring_vals):
            recurrence_values = {field: vals.pop(field) for field in recurrence_fields if field in vals}
            if vals.get('recurrency'):
                detached_events = event._apply_recurrence_values(recurrence_values)
                detached_events.active = False

        events.filtered(lambda event: event.start > fields.Datetime.now()).attendee_ids._send_invitation_emails()

        events._sync_activities(fields={f for vals in vals_list for f in vals.keys()})
        if not self.env.context.get('dont_notify'):
            alarm_events = self.env['calendar.event']
            for event, values in zip(events, vals_list):
                if values.get('allday'):
                    # All day events will trigger the _inverse_date method which will create the trigger.
                    continue
                alarm_events |= event
            recurring_events = alarm_events.filtered('recurrence_id')
            recurring_events.recurrence_id._setup_alarms()
            (alarm_events - recurring_events)._setup_alarms()
        return events.with_context(is_calendar_event_new=False)

    def _compute_field_value(self, field):
        if field.compute_sudo:
            return super(Meeting, self.with_context(prefetch_fields=False))._compute_field_value(field)
        return super()._compute_field_value(field)

    def _fetch_query(self, query, fields):
        if self.env.is_system():
            return super()._fetch_query(query, fields)

        public_fnames = self._get_public_fields()
        private_fields = [field for field in fields if field.name not in public_fnames]
        if not private_fields:
            return super()._fetch_query(query, fields)

        fields_to_fetch = list(fields) + [self._fields[name] for name in ('privacy', 'user_id', 'partner_ids')]
        events = super()._fetch_query(query, fields_to_fetch)

        # determine private events to which the user does not participate
        current_partner_id = self.env.user.partner_id
        others_private_events = events.filtered(
            lambda e: e.privacy == 'private' \
                  and e.user_id != self.env.user \
                  and current_partner_id not in e.partner_ids
        )
        if not others_private_events:
            return events

        private_fields.append(self._fields['partner_ids'])
        for field in private_fields:
            replacement = field.convert_to_cache(
                _('Busy') if field.name == 'name' else False,
                others_private_events)
            self.env.cache.update(others_private_events, field, repeat(replacement))

        return events

    def write(self, values):
        detached_events = self.env['calendar.event']
        recurrence_update_setting = values.pop('recurrence_update', None)
        update_recurrence = recurrence_update_setting in ('all_events', 'future_events') and len(self) == 1
        break_recurrence = values.get('recurrency') is False

        if any(vals in self._get_recurrent_fields() for vals in values) and not (update_recurrence or values.get('recurrency')):
            raise UserError(_('Unable to save the recurrence with "This Event"'))

        update_alarms = False
        update_time = False
        self._set_videocall_location([values])
        if 'partner_ids' in values:
            values['attendee_ids'] = self._attendees_values(values['partner_ids'])
            update_alarms = True
            if self.videocall_channel_id:
                new_partner_ids = []
                for command in values['partner_ids']:
                    if command[0] == Command.LINK:
                        new_partner_ids.append(command[1])
                    elif command[0] == Command.SET:
                        new_partner_ids.extend(command[2])
                self.videocall_channel_id.add_members(new_partner_ids)

        time_fields = self.env['calendar.event']._get_time_fields()
        if any([values.get(key) for key in time_fields]):
            update_alarms = True
            update_time = True
        if 'alarm_ids' in values:
            update_alarms = True

        if (not recurrence_update_setting or recurrence_update_setting == 'self_only' and len(self) == 1) and 'follow_recurrence' not in values:
            if any({field: values.get(field) for field in time_fields if field in values}):
                values['follow_recurrence'] = False

        previous_attendees = self.attendee_ids

        recurrence_values = {field: values.pop(field) for field in self._get_recurrent_fields() if field in values}
        if update_recurrence:
            if break_recurrence:
                # Update this event
                detached_events |= self._break_recurrence(future=recurrence_update_setting == 'future_events')
            else:
                future_edge_case = recurrence_update_setting == 'future_events' and self == self.recurrence_id.base_event_id
                time_values = {field: values.pop(field) for field in time_fields if field in values}
                if 'access_token' in values:
                    values.pop('access_token')  # prevents copying access_token to other events in recurrency
                if recurrence_update_setting == 'all_events' or future_edge_case:
                    # Update all events: we create a new reccurrence and dismiss the existing events
                    self._rewrite_recurrence(values, time_values, recurrence_values)
                else:
                    # Update future events: trim recurrence, delete remaining events except base event and recreate it
                    # All the recurrent events processing is done within the following method
                    self._update_future_events(values, time_values, recurrence_values)
        else:
            super().write(values)
            self._sync_activities(fields=values.keys())

        # We reapply recurrence for future events and when we add a rrule and 'recurrency' == True on the event
        if recurrence_update_setting not in ['self_only', 'all_events'] and not break_recurrence:
            detached_events |= self._apply_recurrence_values(recurrence_values, future=recurrence_update_setting == 'future_events')

        (detached_events & self).active = False
        (detached_events - self).with_context(archive_on_error=True).unlink()

        # Notify attendees if there is an alarm on the modified event, or if there was an alarm
        # that has just been removed, as it might have changed their next event notification
        if not self.env.context.get('dont_notify') and update_alarms:
            self.recurrence_id._setup_alarms(recurrence_update=True)
            if not self.recurrence_id:
                self._setup_alarms()
        attendee_update_events = self.filtered(lambda ev: ev.user_id and ev.user_id != self.env.user)
        if update_time and attendee_update_events:
            # Another user update the event time fields. It should not be auto accepted for the organizer.
            # This prevent weird behavior when a user modified future events time fields and
            # the base event of a recurrence is accepted by the organizer but not the following events
            attendee_update_events.attendee_ids.filtered(lambda att: self.user_id.partner_id == att.partner_id).write({'state': 'needsAction'})

        current_attendees = self.filtered('active').attendee_ids
        if 'partner_ids' in values:
            # we send to all partners and not only the new ones
            (current_attendees - previous_attendees)._send_mail_to_attendees(
                self.env.ref('calendar.calendar_template_meeting_invitation', raise_if_not_found=False)
            )
        if not self.env.context.get('is_calendar_event_new') and 'start' in values:
            start_date = fields.Datetime.to_datetime(values.get('start'))
            # Only notify on future events
            if start_date and start_date >= fields.Datetime.now():
                (current_attendees & previous_attendees).with_context(
                    calendar_template_ignore_recurrence=not update_recurrence
                )._send_mail_to_attendees(
                    self.env.ref('calendar.calendar_template_meeting_changedate', raise_if_not_found=False)
                )

        return True

    @api.depends('privacy', 'user_id')
    def _compute_display_name(self):
        """ Hide private events' name for events which don't belong to the current user
        """
        hidden = self.filtered(
            lambda evt:
                evt.privacy == 'private' and
                evt.user_id.id != self.env.uid and
                self.env.user.partner_id not in evt.partner_ids
        )
        hidden.display_name = _('Busy')
        super(Meeting, self - hidden)._compute_display_name()

    @api.model
    def read_group(self, domain, fields, groupby, offset=0, limit=None, orderby=False, lazy=True):
        groupby = [groupby] if isinstance(groupby, str) else groupby
        fields_aggregates = [
            field_name for field_name in (fields or list(self._fields))
            if ':' in field_name or (field_name in self and self._fields[field_name].group_operator)
        ]
        grouped_fields = {group_field.split(':')[0] for group_field in groupby + fields_aggregates}
        private_fields = grouped_fields - self._get_public_fields()
        if not self.env.su and private_fields:
            # display public and confidential events
            domain = AND([domain, ['|', ('privacy', '!=', 'private'), ('user_id', '=', self.env.user.id)]])
            return super(Meeting, self).read_group(domain, fields, groupby, offset=offset, limit=limit, orderby=orderby, lazy=lazy)
        return super(Meeting, self).read_group(domain, fields, groupby, offset=offset, limit=limit, orderby=orderby, lazy=lazy)

    def unlink(self):
        if not self:
            return super().unlink()

        # Get concerned attendees to notify them if there is an alarm on the unlinked events,
        # as it might have changed their next event notification
        events = self.filtered_domain([('alarm_ids', '!=', False)])
        partner_ids = events.mapped('partner_ids').ids

        # don't forget to update recurrences if there are some base events in the set to unlink,
        # but after having removed the events ;-)
        recurrences = self.env["calendar.recurrence"].search([
            ('base_event_id', 'in', [e.id for e in self])
        ])

        result = super().unlink()

        if recurrences:
            recurrences._select_new_base_event()

        # Notify the concerned attendees (must be done after removing the events)
        self.env['calendar.alarm_manager']._notify_next_alarm(partner_ids)
        return result

    def copy(self, default=None):
        """When an event is copied, the attendees should be recreated to avoid sharing the same attendee records
         between copies
         """
        self.ensure_one()
        if not default:
            default = {}
        # We need to make sure that the attendee_ids are recreated with new ids to avoid sharing attendees between events
        # The copy should not have the same attendee status than the original event
        default.update(partner_ids=[Command.set([])], attendee_ids=[Command.set([])])
        copied_event = super().copy(default)
        copied_event.write({'partner_ids': [(Command.set(self.partner_ids.ids))]})
        return copied_event

    @api.model
    def _get_mail_message_access(self, res_ids, operation, model_name=None):
        if operation == 'read' and (not model_name or model_name == 'event.event'):
            for event in self.browse(res_ids):
                if event.privacy == "private" and self.env.user.partner_id not in event.attendee_ids.partner_id:
                    return 'write'
        return super()._get_mail_message_access(res_ids, operation, model_name=model_name)

    def _attendees_values(self, partner_commands):
        """
        :param partner_commands: ORM commands for partner_id field (0 and 1 commands not supported)
        :return: associated attendee_ids ORM commands
        """
        attendee_commands = []

        removed_partner_ids = []
        added_partner_ids = []

        # if commands are just integers, assume they are ids with the intent to `Command.set`
        if partner_commands and isinstance(partner_commands[0], int):
            partner_commands = [Command.set(partner_commands)]

        for command in partner_commands:
            op = command[0]
            if op in (2, 3, Command.delete, Command.unlink):  # Remove partner
                removed_partner_ids += [command[1]]
            elif op in (6, Command.set):  # Replace all
                removed_partner_ids += set(self.partner_ids.ids) - set(command[2])  # Don't recreate attendee if partner already attend the event
                added_partner_ids += set(command[2]) - set(self.partner_ids.ids)
            elif op in (4, Command.link):
                added_partner_ids += [command[1]] if command[1] not in self.partner_ids.ids else []
            # commands 0 and 1 not supported

        if not self:
            attendees_to_unlink = self.env['calendar.attendee']
        else:
            attendees_to_unlink = self.env['calendar.attendee'].search([
                ('event_id', 'in', self.ids),
                ('partner_id', 'in', removed_partner_ids),
            ])
        attendee_commands += [[2, attendee.id] for attendee in attendees_to_unlink]  # Removes and delete

        attendee_commands += [
            [0, 0, dict(partner_id=partner_id)]
            for partner_id in added_partner_ids
        ]
        return attendee_commands

    def _create_videocall_channel(self):
        if self.recurrency:
            # check if any of the events have videocall_channel_id, if not create one
            event_with_channel = self.env['calendar.event'].search([
                ('recurrence_id', '=', self.recurrence_id.id),
                ('videocall_channel_id', '!=', False)
            ], limit=1)
            if event_with_channel:
                self.videocall_channel_id = event_with_channel.videocall_channel_id
                return
        self.videocall_channel_id = self._create_videocall_channel_id(self.name, self.partner_ids.ids)
        self.videocall_channel_id.channel_change_description(self.recurrence_id.name if self.recurrency else self.display_time)

    def _create_videocall_channel_id(self, name, partner_ids):
        videocall_channel = self.env['discuss.channel'].create_group(partner_ids, default_display_mode='video_full_screen', name=name)
        # if recurrent event, set channel to all other records of the same recurrency
        if self.recurrency:
            recurrent_events_without_channel = self.env['calendar.event'].search([
                ('recurrence_id', '=', self.recurrence_id.id), ('videocall_channel_id', '=', False)
            ])
            recurrent_events_without_channel.videocall_channel_id = videocall_channel
        return videocall_channel

    # ------------------------------------------------------------
    # ACTIONS
    # ------------------------------------------------------------

    # dummy method. this method is intercepted in the frontend and the value is set locally
    def set_discuss_videocall_location(self):
        return True

    # dummy method. this method is intercepted in the frontend and the value is set locally
    def clear_videocall_location(self):
        return True

    def action_open_calendar_event(self):
        if self.res_model and self.res_id:
            return self.env[self.res_model].browse(self.res_id).get_formview_action()
        return False

    def action_sendmail(self):
        email = self.env.user.email
        if email:
            for meeting in self:
                meeting.attendee_ids._send_mail_to_attendees(
                    self.env.ref('calendar.calendar_template_meeting_invitation', raise_if_not_found=False)
                )
        return True

    def action_open_composer(self):
        if not self.partner_ids:
            raise UserError(_("There are no attendees on these events"))
        template_id = self.env['ir.model.data']._xmlid_to_res_id('calendar.calendar_template_meeting_update', raise_if_not_found=False)
        # The mail is sent with datetime corresponding to the sending user TZ
        default_composition_mode = self.env.context.get('default_composition_mode', self.env.context.get('composition_mode', 'comment'))
        compose_ctx = dict(
            default_composition_mode=default_composition_mode,
            default_model='calendar.event',
            default_res_ids=self.ids,
            default_template_id=template_id,
            default_partner_ids=self.partner_ids.ids,
            mail_tz=self.env.user.tz,
        )
        return {
            'type': 'ir.actions.act_window',
            'name': _('Contact Attendees'),
            'view_mode': 'form',
            'res_model': 'mail.compose.message',
            'views': [(False, 'form')],
            'view_id': False,
            'target': 'new',
            'context': compose_ctx,
        }

    def action_join_video_call(self):
        return {
            'type': 'ir.actions.act_url',
            'url': self.videocall_location,
            'target': 'new'
        }

    def action_join_meeting(self, partner_id):
        """ Method used when an existing user wants to join
        """
        self.ensure_one()
        partner = self.env['res.partner'].browse(partner_id)
        if partner not in self.partner_ids:
            self.write({'partner_ids': [(4, partner.id)]})

    def action_mass_deletion(self, recurrence_update_setting):
        self.ensure_one()
        if recurrence_update_setting == 'all_events':
            events = self.recurrence_id.calendar_event_ids
            self.recurrence_id.unlink()
            events.unlink()
        elif recurrence_update_setting == 'future_events':
            future_events = self.recurrence_id.calendar_event_ids.filtered(lambda ev: ev.start >= self.start)
            future_events.unlink()

    def action_mass_archive(self, recurrence_update_setting):
        """
        The aim of this action purpose is to be called from sync calendar module when mass deletion is not possible.
        """
        self.ensure_one()
        if recurrence_update_setting == 'all_events':
            self.recurrence_id.calendar_event_ids.write(self._get_archive_values())
        elif recurrence_update_setting == 'future_events':
            detached_events = self.recurrence_id._stop_at(self)
            detached_events.write(self._get_archive_values())
        elif recurrence_update_setting == 'self_only':
            self.write({
                'active': False,
                'recurrence_update': 'self_only'
            })
            if len(self.recurrence_id.calendar_event_ids) == 0:
                self.recurrence_id.unlink()
            elif self == self.recurrence_id.base_event_id:
                self.recurrence_id._select_new_base_event()

    # ------------------------------------------------------------
    # MAILING
    # ------------------------------------------------------------

    def _get_attendee_emails(self):
        """ Get comma-separated attendee email addresses. """
        self.ensure_one()
        return ",".join([e for e in self.attendee_ids.mapped("email") if e])

    def _get_mail_tz(self):
        self.ensure_one()
        return self.event_tz or self.env.user.tz

    def _sync_activities(self, fields):
        # update activities
        for event in self:
            if event.activity_ids:
                activity_values = {}
                if 'name' in fields:
                    activity_values['summary'] = event.name
                if 'description' in fields:
                    activity_values['note'] = event.description
                if 'start' in fields:
                    # self.start is a datetime UTC *only when the event is not allday*
                    # activty.date_deadline is a date (No TZ, but should represent the day in which the user's TZ is)
                    # See 72254129dbaeae58d0a2055cba4e4a82cde495b7 for the same issue, but elsewhere
                    deadline = event.start
                    user_tz = self.env.context.get('tz')
                    if user_tz and not event.allday:
                        deadline = pytz.utc.localize(deadline)
                        deadline = deadline.astimezone(pytz.timezone(user_tz))
                    activity_values['date_deadline'] = deadline.date()
                if 'user_id' in fields:
                    activity_values['user_id'] = event.user_id.id
                if activity_values.keys():
                    event.activity_ids.write(activity_values)

    # ------------------------------------------------------------
    # ALARMS
    # ------------------------------------------------------------

    def _get_trigger_alarm_types(self):
        return ['email']

    def _setup_alarms(self):
        """ Schedule cron triggers for future events """
        cron = self.env.ref('calendar.ir_cron_scheduler_alarm').sudo()
        alarm_types = self._get_trigger_alarm_types()
        events_to_notify = self.env['calendar.event']
        triggers_by_events = {}
        for event in self:
            existing_trigger = event.recurrence_id.trigger_id
            for alarm in (alarm for alarm in event.alarm_ids if alarm.alarm_type in alarm_types):
                at = event.start - timedelta(minutes=alarm.duration_minutes)
                create_trigger = not existing_trigger or existing_trigger and existing_trigger.call_at != at
                if create_trigger and (not cron.lastcall or at > cron.lastcall):
                    # Don't trigger for past alarms, they would be skipped by design
                    trigger = cron._trigger(at=at)
                    triggers_by_events[event.id] = trigger.id
            if any(alarm.alarm_type == 'notification' for alarm in event.alarm_ids):
                # filter events before notifying attendees through calendar_alarm_manager
                events_to_notify |= event.filtered(lambda ev: ev.alarm_ids and ev.stop >= fields.Datetime.now())
        if events_to_notify:
            self.env['calendar.alarm_manager']._notify_next_alarm(events_to_notify.partner_ids.ids)
        return triggers_by_events

    def get_next_alarm_date(self, events_by_alarm):
        self.ensure_one()
        now = fields.datetime.now()
        sorted_alarms = self.alarm_ids.sorted("duration_minutes")
        triggered_alarms = sorted_alarms.filtered(lambda alarm: alarm.id in events_by_alarm)[0]
        event_has_future_alarms = sorted_alarms[0] != triggered_alarms
        next_date = None
        if self.recurrence_id.trigger_id and self.recurrence_id.trigger_id.call_at <= now:
            next_date = self.start - timedelta(minutes=sorted_alarms[0].duration_minutes) \
                if event_has_future_alarms \
                else self.start
        return next_date

    # ------------------------------------------------------------
    # RECURRENCY
    # ------------------------------------------------------------

    def _apply_recurrence_values(self, values, future=True):
        """Apply the new recurrence rules in `values`. Create a recurrence if it does not exist
        and create all missing events according to the rrule.
        If the changes are applied to future
        events only, a new recurrence is created with the updated rrule.

        :param values: new recurrence values to apply
        :param future: rrule values are applied to future events only if True.
                       Rrule changes are applied to all events in the recurrence otherwise.
                       (ignored if no recurrence exists yet).
        :return: events detached from the recurrence
        """
        if not values:
            return self.browse()
        recurrence_vals = []
        to_update = self.env['calendar.recurrence']
        for event in self:
            if not event.recurrence_id:
                recurrence_vals += [dict(values, base_event_id=event.id, calendar_event_ids=[(4, event.id)])]
            elif future:
                to_update |= event.recurrence_id._split_from(event, values)
        self.write({'recurrency': True, 'follow_recurrence': True})
        to_update |= self.env['calendar.recurrence'].create(recurrence_vals)
        return to_update._apply_recurrence()

    def _get_recurrence_params(self):
        if not self:
            return {}
        event_date = self._get_start_date()
        weekday_field_name = weekday_to_field(event_date.weekday())
        return {
            weekday_field_name: True,
            'weekday': weekday_field_name.upper(),
            'byday': str(get_weekday_occurence(event_date)),
            'day': event_date.day,
        }

    @api.model
    def _get_recurrence_params_by_date(self, event_date):
        """ Return the recurrence parameters from a date object. """
        weekday_field_name = weekday_to_field(event_date.weekday())
        return {
            weekday_field_name: True,
            'weekday': weekday_field_name.upper(),
            'byday': str(get_weekday_occurence(event_date)),
            'day': event_date.day,
        }

    def _split_recurrence(self, time_values):
        """Apply time changes to events and update the recurrence accordingly.

        :return: detached events
        """
        self.ensure_one()
        if not time_values:
            return self.browse()
        if self.follow_recurrence and self.recurrency:
            previous_week_day_field = weekday_to_field(self._get_start_date().weekday())
        else:
            # When we try to change recurrence values of an event not following the recurrence, we get the parameters from
            # the base_event
            previous_week_day_field = weekday_to_field(self.recurrence_id.base_event_id._get_start_date().weekday())
        self.write(time_values)
        return self._apply_recurrence_values({
            previous_week_day_field: False,
            **self._get_recurrence_params(),
        }, future=True)

    def _break_recurrence(self, future=True):
        """Breaks the event's recurrence.
        Stop the recurrence at the current event if `future` is True, leaving past events in the recurrence.
        If `future` is False, all events in the recurrence are detached and the recurrence itself is unlinked.
        :return: detached events excluding the current events
        """
        recurrences_to_unlink = self.env['calendar.recurrence']
        detached_events = self.env['calendar.event']
        for event in self:
            recurrence = event.recurrence_id
            if future:
                detached_events |= recurrence._stop_at(event)
            else:
                detached_events |= recurrence.calendar_event_ids
                recurrence.calendar_event_ids.recurrence_id = False
                recurrences_to_unlink |= recurrence
        recurrences_to_unlink.with_context(archive_on_error=True).unlink()
        return detached_events - self

    def _get_time_update_dict(self, base_event, time_values):
        """ Return the update dictionary for shifting the base_event's time to the new date. """
        if not base_event:
            raise UserError(_("You can't update a recurrence without base event."))
        [base_time_values] = base_event.read(['start', 'stop', 'allday'])
        update_dict = {}
        start_update = fields.Datetime.to_datetime(time_values.get('start'))
        stop_update = fields.Datetime.to_datetime(time_values.get('stop'))
        # Convert the base_event_id hours according to new values: time shift
        if start_update or stop_update:
            if start_update:
                start = base_time_values['start'] + (start_update - self.start)
                stop = base_time_values['stop'] + (start_update - self.start)
                start_date = base_time_values['start'].date() + (start_update.date() - self.start.date())
                stop_date = base_time_values['stop'].date() + (start_update.date() - self.start.date())
                update_dict.update({'start': start, 'start_date': start_date, 'stop': stop, 'stop_date': stop_date})
            if stop_update:
                if not start_update:
                    # Apply the same shift for start
                    start = base_time_values['start'] + (stop_update - self.stop)
                    start_date = base_time_values['start'].date() + (stop_update.date() - self.stop.date())
                    update_dict.update({'start': start, 'start_date': start_date})
                stop = base_time_values['stop'] + (stop_update - self.stop)
                stop_date = base_time_values['stop'].date() + (stop_update.date() - self.stop.date())
                update_dict.update({'stop': stop, 'stop_date': stop_date})
        return update_dict

    @api.model
    def _get_archive_values(self):
        """ Return parameters for archiving events in calendar module. """
        return {'active': False}

    @api.model
    def _check_values_to_sync(self, values):
        """ Method to be overriden: return candidate values to be synced within rewrite_recurrence function scope. """
        return False

    @api.model
    def _get_update_future_events_values(self):
        """ Return parameters for updating future events within _update_future_events function scope. """
        return {}

    @api.model
    def _get_remove_sync_id_values(self):
        """ Return parameters for removing event synchronization id within _update_future_events function scope. """
        return {}

    def _get_updated_recurrence_values(self, new_start_date):
        """ Copy values from current recurrence and update the start date weekday. """
        [previous_recurrence_values] = self.recurrence_id.copy_data()
        if self.start.weekday() != new_start_date.weekday():
            previous_recurrence_values.pop(weekday_to_field(self.start.weekday()), None)
        return previous_recurrence_values

    def _update_future_events(self, values, time_values, recurrence_values):
        """
            Trim the current recurrence detaching the occurrences after current event,
            deactivate the detached events except for the updated event and apply recurrence values.
        """
        self.ensure_one()
        base_event = self
        update_dict = self._get_time_update_dict(base_event, time_values)
        time_values.update(update_dict)
        # Get base values from the previous recurrence and update the start date weekday field.
        start_date = time_values['start'].date() if 'start' in time_values else self.start.date()
        previous_recurrence_values = self._get_updated_recurrence_values(start_date)

        # Trim previous recurrence at current event, deleting following events except for the updated event.
        detached_events_split = self.recurrence_id._stop_at(self)
        (detached_events_split - self).write({'active': False, **self._get_remove_sync_id_values()})

        # Update the current event with the new recurrence information.
        if values or time_values:
            self.write({
                **time_values, **values,
                **self._get_remove_sync_id_values(),
                **self._get_update_future_events_values()
            })

        # Combine parameters from previous recurrence with the new recurrence parameters.
        new_values = {
            **previous_recurrence_values,
            **self._get_recurrence_params_by_date(start_date),
            **recurrence_values,
            'count': recurrence_values.get('count', 0) or len(detached_events_split)
        }
        new_values.pop('rrule', None)

        # Generate the new recurrence by patching the updated event and return an empty list.
        self._apply_recurrence_values(new_values)

    def _rewrite_recurrence(self, values, time_values, recurrence_values):
        """ Delete the current recurrence, reactivate base event and apply updated recurrence values. """
        self.ensure_one()
        base_event = self.recurrence_id.base_event_id or self.recurrence_id._get_first_event(include_outliers=False)
        update_dict = self._get_time_update_dict(base_event, time_values)
        time_values.update(update_dict)

        if self._check_values_to_sync(values) or time_values or recurrence_values:
            # Get base values from the previous recurrence and update the start date weekday field.
            start_date = time_values['start'].date() if 'start' in time_values else self.start.date()
            old_recurrence_values = self._get_updated_recurrence_values(start_date)

            # Archive all events and delete recurrence, reactivate base event and apply updated values.
            base_event.action_mass_archive("all_events")
            base_event.recurrence_id.unlink()
            base_event.write({
                'active': True,
                'recurrence_id': False,
                **values, **time_values
            })

            # Combine parameters from previous recurrence with the new recurrence parameters.
            new_values = {
                **old_recurrence_values,
                **base_event._get_recurrence_params(),
                **recurrence_values,
            }
            new_values.pop('rrule', None)

            # Patch base event with updated recurrence parameters: this will recreate the recurrence.
            detached_events = base_event._apply_recurrence_values(new_values)
            detached_events.write({'active': False})
        else:
            # Write on all events. Carefull, it could trigger a lot of noise to Google/Microsoft...
            self.recurrence_id._write_events(values)

    # ------------------------------------------------------------
    # MANAGEMENT
    # ------------------------------------------------------------

    def change_attendee_status(self, status, recurrence_update_setting):
        self.ensure_one()
        if recurrence_update_setting == 'all_events':
            events = self.recurrence_id.calendar_event_ids
        elif recurrence_update_setting == 'future_events':
            events = self.recurrence_id.calendar_event_ids.filtered(lambda ev: ev.start >= self.start)
        else:
            events = self
        attendee = events.attendee_ids.filtered(lambda x: x.partner_id == self.env.user.partner_id)
        if status == 'accepted':
            return attendee.do_accept()
        if status == 'declined':
            return attendee.do_decline()
        return attendee.do_tentative()

    def find_partner_customer(self):
        self.ensure_one()
        return next(
            (attendee.partner_id for attendee in self.attendee_ids.sorted('create_date')
             if attendee.partner_id != self.user_id.partner_id),
            self.env['calendar.attendee']
        )

    # ------------------------------------------------------------
    # TOOLS
    # ------------------------------------------------------------

    def _get_start_date(self):
        """Return the event starting date in the event's timezone.
        If no starting time is assigned (yet), return today as default
        :return: date
        """
        if not self.start:
            return fields.Date.today()
        if self.recurrency and self.event_tz:
            tz = pytz.timezone(self.event_tz)
            # Ensure that all day events date are not calculated around midnight. TZ shift would potentially return bad date
            start = self.start if not self.allday else self.start.replace(hour=12)
            return pytz.utc.localize(start).astimezone(tz).date()
        return self.start.date()

    def _range(self):
        self.ensure_one()
        return (self.start, self.stop)

    def get_display_time_tz(self, tz=False):
        """ get the display_time of the meeting, forcing the timezone. This method is called from email template, to not use sudo(). """
        self.ensure_one()
        if tz:
            self = self.with_context(tz=tz)
        return self._get_display_time(self.start, self.stop, self.duration, self.allday)

    def _get_ics_file(self):
        """ Returns iCalendar file for the event invitation.
            :returns a dict of .ics file content for each meeting
        """
        result = {}

        def ics_datetime(idate, allday=False):
            if idate:
                if allday:
                    return idate
                return idate.replace(tzinfo=pytz.timezone('UTC'))
            return False

        if not vobject:
            return result

        for meeting in self:
            cal = vobject.iCalendar()
            event = cal.add('vevent')

            if not meeting.start or not meeting.stop:
                raise UserError(_("First you have to specify the date of the invitation."))
            event.add('created').value = ics_datetime(fields.Datetime.now())
            event.add('dtstart').value = ics_datetime(meeting.start, meeting.allday)
            event.add('dtend').value = ics_datetime(meeting.stop, meeting.allday)
            event.add('summary').value = meeting._get_customer_summary()
            description = meeting._get_customer_description()
            if description:
                event.add('description').value = description
            if meeting.location:
                event.add('location').value = meeting.location
            if meeting.rrule:
                event.add('rrule').value = meeting.rrule

            if meeting.alarm_ids:
                for alarm in meeting.alarm_ids:
                    valarm = event.add('valarm')
                    interval = alarm.interval
                    duration = alarm.duration
                    trigger = valarm.add('TRIGGER')
                    trigger.params['related'] = ["START"]
                    if interval == 'days':
                        delta = timedelta(days=duration)
                    elif interval == 'hours':
                        delta = timedelta(hours=duration)
                    elif interval == 'minutes':
                        delta = timedelta(minutes=duration)
                    trigger.value = delta
                    valarm.add('DESCRIPTION').value = alarm.name or u'Odoo'
            for attendee in meeting.attendee_ids:
                attendee_add = event.add('attendee')
                attendee_add.value = u'MAILTO:' + (attendee.email or u'')

            # Add "organizer" field if email available
            if meeting.partner_id.email:
                organizer = event.add('organizer')
                organizer.value = u'MAILTO:' + meeting.partner_id.email
                if meeting.partner_id.name:
                    organizer.params['CN'] = [meeting.partner_id.display_name.replace('\"', '\'')]

            result[meeting.id] = cal.serialize().encode('utf-8')

        return result

    def _get_customer_description(self):
        """:return (str): The description to include in calendar exports"""
        return html2plaintext(self.description) if self.description else ''

    def _get_customer_summary(self):
        """:return (str): The summary to include in calendar exports"""
        return self.name or ''

    @api.model
    def _get_display_time(self, start, stop, zduration, zallday):
        """ Return date and time (from to from) based on duration with timezone in string. Eg :
                1) if user add duration for 2 hours, return : August-23-2013 at (04-30 To 06-30) (Europe/Brussels)
                2) if event all day ,return : AllDay, July-31-2013
        """
        timezone = self._context.get('tz') or self.env.user.partner_id.tz or 'UTC'

        # get date/time format according to context
        format_date, format_time = self._get_date_formats()

        # convert date and time into user timezone
        self_tz = self.with_context(tz=timezone)
        date = fields.Datetime.context_timestamp(self_tz, fields.Datetime.from_string(start))
        date_deadline = fields.Datetime.context_timestamp(self_tz, fields.Datetime.from_string(stop))

        # convert into string the date and time, using user formats
        to_text = pycompat.to_text
        date_str = to_text(date.strftime(format_date))
        time_str = to_text(date.strftime(format_time))

        if zallday:
            display_time = _("All Day, %(day)s", day=date_str)
        elif zduration < 24:
            duration = date + timedelta(minutes=round(zduration*60))
            duration_time = to_text(duration.strftime(format_time))
            display_time = _(
                u"%(day)s at (%(start)s To %(end)s) (%(timezone)s)",
                day=date_str,
                start=time_str,
                end=duration_time,
                timezone=timezone,
            )
        else:
            dd_date = to_text(date_deadline.strftime(format_date))
            dd_time = to_text(date_deadline.strftime(format_time))
            display_time = _(
                u"%(date_start)s at %(time_start)s To\n %(date_end)s at %(time_end)s (%(timezone)s)",
                date_start=date_str,
                time_start=time_str,
                date_end=dd_date,
                time_end=dd_time,
                timezone=timezone,
            )
        return display_time

    def _get_duration(self, start, stop):
        """ Get the duration value between the 2 given dates. """
        if not start or not stop:
            return 0
        duration = (stop - start).total_seconds() / 3600
        return round(duration, 2)

    @api.model
    def _get_date_formats(self):
        """ get current date and time format, according to the context lang
            :return: a tuple with (format date, format time)
        """
        lang = get_lang(self.env)
        return (lang.date_format, lang.time_format)

    @api.model
    def _get_recurrent_fields(self):
        return {'byday', 'until', 'rrule_type', 'month_by', 'event_tz', 'rrule',
                'interval', 'count', 'end_type', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat',
                'sun', 'day', 'weekday'}

    @api.model
    def _get_time_fields(self):
        return {'start', 'stop', 'start_date', 'stop_date'}

    @api.model
    def _get_custom_fields(self):
        all_fields = self.fields_get(attributes=['manual'])
        return {fname for fname in all_fields if all_fields[fname]['manual']}

    @api.model
    def _get_public_fields(self):
        return self._get_recurrent_fields() | self._get_time_fields() | self._get_custom_fields() | {
            'id', 'active', 'allday',
            'duration', 'user_id', 'interval', 'partner_id',
            'count', 'rrule', 'recurrence_id', 'show_as', 'privacy'}
