From 8a46f3c66a21467151d998d3ec8398946859e6e6 Mon Sep 17 00:00:00 2001
From: Gergely Polonkai <gergely@polonkai.eu>
Date: Mon, 2 Jul 2018 15:07:53 +0200
Subject: [PATCH] Add proper time zone support
MIME-Version: 1.0
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Until now event timestamps were saved in the server’s time zone.  Now they are saved in UTC,
considering the time zone set by the creator of the event.
---
 calsocial/forms.py                  | 63 ++++++++++++++++++++++++++++-
 calsocial/models.py                 | 13 ++++++
 calsocial/templates/month-view.html | 22 +++++++++-
 3 files changed, 95 insertions(+), 3 deletions(-)

diff --git a/calsocial/forms.py b/calsocial/forms.py
index 1274948..91e10fa 100644
--- a/calsocial/forms.py
+++ b/calsocial/forms.py
@@ -1,6 +1,7 @@
 from flask_babelex import lazy_gettext as _
 from flask_wtf import FlaskForm
-from wtforms import PasswordField, StringField, BooleanField
+import pytz
+from wtforms import BooleanField, PasswordField, SelectField, StringField
 from wtforms.ext.dateutil.fields import DateTimeField
 from wtforms.validators import DataRequired, Email, ValidationError
 from wtforms.widgets import TextArea
@@ -17,14 +18,72 @@ class RegistrationForm(FlaskForm):
             raise ValidationError(_('The two passwords must match!'))
 
 
+class TimezoneField(SelectField):
+    def __init__(self, *args, **kwargs):
+        kwargs.update({
+            'choices': [
+                (pytz.timezone(tz), tz.replace('_', ' '))
+                for tz in pytz.common_timezones
+            ],
+        })
+
+        SelectField.__init__(self, *args, **kwargs)
+
+    def process_formdata(self, valuelist):
+        if not valuelist:
+            self.data = None
+
+            return
+
+        try:
+            self.data = pytz.timezone(valuelist[0])
+        except pytz.exceptions.UnknownTimeZoneError:
+            self.data = None
+
+            raise ValueError('Unknown time zone')
+
+    @staticmethod
+    def is_pytz_instance(value):
+        return value is pytz.UTC or isinstance(value, pytz.tzinfo.BaseTzInfo)
+
+    def process_data(self, value):
+        if value is None:
+            self.data = None
+
+            return
+
+        if is_pytz_instance(value):
+            self.data = value
+
+            return
+
+        try:
+            self.data = pytz.timezone(value)
+        except Exception as exc:
+            raise ValueError(f'Unknown time zone {value}')
+
+    def iter_choices(self):
+        for value, label in self.choices:
+            yield (value, label, value == self.data)
+
+
 class EventForm(FlaskForm):
     title = StringField(_('Title'), validators=[DataRequired()])
-    time_zone = StringField(_('Time zone'), validators=[DataRequired()])
+    time_zone = TimezoneField(_('Time zone'), validators=[DataRequired()])
     start_time = DateTimeField(_('Start time'), validators=[DataRequired()])
     end_time = DateTimeField(_('End time'), validators=[DataRequired()])
     all_day = BooleanField(_('All day'))
     description = StringField(_('Description'), widget=TextArea())
 
+    def populate_obj(self, obj):
+        FlaskForm.populate_obj(self, obj)
+
+        tz = self.time_zone.data
+
+        obj.time_zone = str(tz)
+        obj.start_time = tz.localize(self.start_time.data).astimezone(pytz.utc)
+        obj.end_time = tz.localize(self.end_time.data).astimezone(pytz.utc)
+
     def validate_end_time(self, field):
         if field.data < self.start_time.data:
             raise ValidationError(_('End time must be later than start time!'))
diff --git a/calsocial/models.py b/calsocial/models.py
index c3fb466..e18d628 100644
--- a/calsocial/models.py
+++ b/calsocial/models.py
@@ -83,5 +83,18 @@ class Event(db.Model):
     #: The description of the event
     description = db.Column(db.UnicodeText())
 
+    def __as_tz(self, timestamp):
+        from pytz import timezone, utc
+
+        return utc.localize(timestamp).astimezone(timezone(self.time_zone))
+
+    @property
+    def start_time_tz(self):
+        return self.__as_tz(self.start_time)
+
+    @property
+    def end_time_tz(self):
+        return self.__as_tz(self.end_time)
+
     def __repr__(self):
         return f'<Event {self.id} ({self.title}) of {self.user}>'
diff --git a/calsocial/templates/month-view.html b/calsocial/templates/month-view.html
index 8400c67..1294b77 100644
--- a/calsocial/templates/month-view.html
+++ b/calsocial/templates/month-view.html
@@ -6,6 +6,7 @@
  table.calendar {
      width: 100%;
      border-collapse: collapse;
+     table-layout: fixed;
  }
 
  tr.month > td {
@@ -46,14 +47,31 @@
      background-color: #d8d8d8;
  }
 
- td > div.event {
+ tr.week > td > div.event {
      border: 1px solid green;
      background-color: white;
      border-radius: 2px;
+     text-overflow: ellipsis;
+     white-space: nowrap;
+     overflow: hidden;
+ }
+
+ tr.sizer > td {
+     width: 14.2857%;
+     height: 0;
  }
 </style>
 <table class="calendar">
     <thead>
+        <tr class="sizer">
+            <td></td>
+            <td></td>
+            <td></td>
+            <td></td>
+            <td></td>
+            <td></td>
+            <td></td>
+        </tr>
         <tr class="month">
             <td>
                 <a href="{{ url_for('hello', date=calendar.prev_year) }}">« {{ calendar.prev_year_year }}</a>
@@ -101,6 +119,8 @@
                 <span class="day-num">{{ day.day }}</span>
     {% for event in calendar.day_events(day, user=current_user) %}
                 <div class="event">
+                    {{ event.start_time_tz.strftime('%H:%M') }}–{{ event.end_time_tz.strftime('%H:%M') }}
+                    ({{ event.time_zone }})
                     {{ event.title }}
                 </div>
     {% endfor %}