[IMP] website_event_online: add time-related computation on events

RATIONALE

Events are sometimes held online, gathering a community. In this merge we
improve Event application to better support full-online events with improved
tracks, wishlists, chat rooms, ...

PURPOSE

Reduce complexity of frontend templates and ease time-related display by
adding computed fields on event.

SPECIFICATIONS

Add following information to be used in future templates

  * is_ongoing: between start and end of event;
  * is_done: after end of event;
  * start_today: will start today, for example to display remaining hours
    before start;
  * start_remaining: remaining time before start;

Ensure timezone are correctly taken into account. Base heuristic is

  * datetime are stored in UTC in database;
  * TZ of event is stored on date_tz of event;
  * make most computation based on UTC: compare UTC of current visitor to
    UTC of event datetime;

LINKS

Community PR #53540
Enterprise PR odoo/enterprise#11384

Task ID-2252655 (Main Online Event task)
Task ID-2283796 (Event B2Basics / Registration Flow)

Co-Authored-By: Aurélien Warnon <awa@odoo.com>
Co-Authored-By: David Beguin <dbe@odoo.com>
Co-Authored-By: Thibault Delavallée <tde@odoo.com>

addons/website_event_online/models/event_event.py

@@ -1,8 +1,12 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
+from datetime import datetime
+from pytz import timezone, utc
+
 from odoo import api, fields, models, _
 from odoo.addons.http_routing.models.ir_http import slug
+from odoo.addons.resource.models.resource import float_to_time
 from odoo.osv import expression
 
 
@@ -14,12 +18,42 @@ class Event(models.Model):
     menu_register_cta = fields.Boolean(
         'Add Register Button', compute='_compute_menu_register_cta',
         readonly=False, store=True)
+    # live information
+    is_ongoing = fields.Boolean(
+        'Is Ongoing', compute='_compute_time_data', search='_search_is_ongoing',
+        help="Whether event has begun")
+    is_done = fields.Boolean(
+        'Is Done', compute='_compute_time_data',
+        help="Whether event is finished")
+    start_today = fields.Boolean(
+        'Start Today', compute='_compute_time_data',
+        help="Whether event is going to start today if still not ongoing")
+    start_remaining = fields.Integer(
+        'Remaining before start', compute='_compute_time_data',
+        help="Remaining time before event starts (minutes)")
 
     @api.depends('website_menu')
     def _compute_menu_register_cta(self):
         for event in self:
             event.menu_register_cta = event.website_menu
 
+    @api.depends('date_begin', 'date_end')
+    def _compute_time_data(self):
+        """ Compute start and remaining time. Do everything in UTC as we compute only
+        time deltas here. """
+        now_utc = utc.localize(fields.Datetime.now().replace(microsecond=0))
+        for event in self:
+            date_begin_utc = utc.localize(event.date_begin, is_dst=False)
+            date_end_utc = utc.localize(event.date_end, is_dst=False)
+            event.is_ongoing = date_begin_utc <= now_utc <= date_end_utc
+            event.is_done = now_utc > date_end_utc
+            event.start_today = date_begin_utc.date() == now_utc.date()
+            if date_begin_utc >= now_utc:
+                td = date_begin_utc - now_utc
+                event.start_remaining = int(td.total_seconds() / 60)
+            else:
+                event.start_remaining = 0
+
     def _compute_is_participating(self):
         """ Override is_participating to improve heuristic that is now