add monthly recurrence options

Add a recurrence option for meetings that repeat monthly. Instantiate
the ones for the first weekdays of the month for now.

Change-Id: I0fa95653594dc5a28008630f57bee67b92537d29
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

README.rst

@@ -163,6 +163,14 @@ yaml2ical supports a number of possible frequency options:
   * ``quadweekly-week-2``, ``quadweekly-alternate``: Occurs when ``ISOweek % 4 == 2``
   * ``quadweekly-week-3``: Occurs when ``ISOweek % 4 == 3``
 
+* Event occurs in the first week of a month:
+
+  * ``first-monday``: On the first Monday of the month.
+  * ``first-tuesday``: On the first Tuesday of the month.
+  * ``first-wednesday``: On the first Wednesday of the month.
+  * ``first-thursday``: On the first Thursday of the month.
+  * ``first-friday``: On the first Friday of the month.
+
 * Event doesn't happen on a defined schedule but is used as a placeholder for
   html generation:
 

yaml2ical/meeting.py

@@ -147,6 +147,11 @@ class Schedule(object):
                 'quadweekly-week-2': set([2]),
                 'quadweekly-week-3': set([3]),
                 'quadweekly-alternate': set([2]),
+                'first-monday': set([0, 1, 2, 3]),
+                'first-tuesday': set([0, 1, 2, 3]),
+                'first-wednesday': set([0, 1, 2, 3]),
+                'first-thursday': set([0, 1, 2, 3]),
+                'first-friday': set([0, 1, 2, 3]),
             }
 
             return len(week[self.freq].intersection(week[other.freq])) > 0

yaml2ical/recurrence.py

@@ -10,6 +10,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import calendar
 import datetime
 
 
@@ -131,6 +132,66 @@ class AdhocRecurrence(object):
     def __str__(self):
         return "Occurs as needed, no fixed schedule."
 
+
+class MonthlyRecurrence(object):
+    """Meetings occuring every month."""
+    def __init__(self, week, day):
+        self._week = week
+        self._day = day
+
+    def next_occurence(self, current_date_time, day):
+        """Return the date of the next meeting.
+
+        :param current_date_time: datetime object of meeting
+        :param day: weekday the meeting is held on
+
+        :returns: datetime object of the next meeting time
+        """
+        weekday = WEEKDAYS[day]
+
+        month = current_date_time.month + 1
+        year = current_date_time.year
+        if current_date_time.month == 12:
+            month = 1
+            year = year + 1
+        next_month_dates = calendar.monthcalendar(year, month)
+
+        # We can't simply index into the dates for the next month
+        # because we don't know that the first week is full of days
+        # that actually appear in that month. Therefore we loop
+        # through them counting down until we've skipped enough weeks.
+        skip_weeks = self._week - 1
+        for week in next_month_dates:
+            day = week[weekday]
+            # Dates in the week that fall in other months
+            # are 0 so we want to skip counting those weeks.
+            if not day:
+                continue
+            # If we have skipped all of the weeks we need to,
+            # we have the day.
+            if not skip_weeks:
+                return datetime.datetime(
+                    year, month, day,
+                    current_date_time.hour, current_date_time.minute,
+                    current_date_time.second, current_date_time.microsecond,
+                )
+            skip_weeks -= 1
+
+        raise ValueError(
+            'Could not compute week {} of next month for {}'.format(
+                self._week, current_date_time)
+        )
+
+    def rrule(self):
+        return {
+            'freq': 'monthly',
+            'byday': '{}{}'.format(self._week, self._day[:2].upper()),
+        }
+
+    def __str__(self):
+        return "Monthly"
+
+
 supported_recurrences = {
     'weekly': WeeklyRecurrence(),
     'biweekly-odd': BiWeeklyRecurrence(style='odd'),
@@ -141,4 +202,9 @@ supported_recurrences = {
     'quadweekly-week-3': QuadWeeklyRecurrence(week=3),
     'quadweekly-alternate': QuadWeeklyRecurrence(week=2),
     'adhoc': AdhocRecurrence(),
+    'first-monday': MonthlyRecurrence(week=1, day='Monday'),
+    'first-tuesday': MonthlyRecurrence(week=1, day='Tuesday'),
+    'first-wednesday': MonthlyRecurrence(week=1, day='Wednesday'),
+    'first-thursday': MonthlyRecurrence(week=1, day='Thursday'),
+    'first-friday': MonthlyRecurrence(week=1, day='Friday'),
 }

yaml2ical/tests/sample_data.py

@@ -362,3 +362,87 @@ chair: John Doe
 description:  >
   Example Quadweekly Alternate meeting
 """
+
+FIRST_MONDAY_MEETING = """
+project: OpenStack Random Meeting
+agenda_url: http://agenda.com/
+project_url: http://project.com
+schedule:
+  - time: '2200'
+    day: Monday
+    irc: openstack-meeting
+    frequency: first-monday
+chair: John Doe
+description:  >
+  Example Monthly meeting
+"""
+
+FIRST_TUESDAY_MEETING = """
+project: OpenStack Random Meeting
+agenda_url: http://agenda.com/
+project_url: http://project.com
+schedule:
+  - time: '2200'
+    day: Tuesday
+    irc: openstack-meeting
+    frequency: first-tuesday
+chair: John Doe
+description:  >
+  Example Monthly meeting
+"""
+
+WEEKLY_MEETING_2200 = """
+project: OpenStack Subteam Meeting
+schedule:
+  - time: '2200'
+    day: Wednesday
+    irc: openstack-meeting
+    frequency: weekly
+chair: Joe Developer
+description: >
+    Weekly meeting for Subteam project.
+agenda: |
+  * Top bugs this week
+"""
+
+FIRST_WEDNESDAY_MEETING = """
+project: OpenStack Random Meeting
+agenda_url: http://agenda.com/
+project_url: http://project.com
+schedule:
+  - time: '2200'
+    day: Wednesday
+    irc: openstack-meeting
+    frequency: first-wednesday
+chair: John Doe
+description:  >
+  Example Monthly meeting
+"""
+
+FIRST_THURSDAY_MEETING = """
+project: OpenStack Random Meeting
+agenda_url: http://agenda.com/
+project_url: http://project.com
+schedule:
+  - time: '2200'
+    day: Thursday
+    irc: openstack-meeting
+    frequency: first-thursday
+chair: John Doe
+description:  >
+  Example Monthly meeting
+"""
+
+FIRST_FRIDAY_MEETING = """
+project: OpenStack Random Meeting
+agenda_url: http://agenda.com/
+project_url: http://project.com
+schedule:
+  - time: '2200'
+    day: Friday
+    irc: openstack-meeting
+    frequency: first-friday
+chair: John Doe
+description:  >
+  Example Monthly meeting
+"""

yaml2ical/tests/test_meeting.py

@@ -163,6 +163,20 @@ class MeetingTestCase(unittest.TestCase):
             sample_data.CONFLICTING_WEEKLY_MEETING,
             sample_data.MEETING_WITH_DURATION)
 
+    def test_monthly_conflicts(self):
+        self.should_be_conflicting(
+            sample_data.WEEKLY_MEETING_2200,
+            sample_data.FIRST_WEDNESDAY_MEETING)
+        self.should_be_conflicting(
+            sample_data.BIWEEKLY_EVEN_MEETING,
+            sample_data.FIRST_WEDNESDAY_MEETING)
+        self.should_be_conflicting(
+            sample_data.QUADWEEKLY_MEETING,
+            sample_data.FIRST_WEDNESDAY_MEETING)
+        self.should_be_conflicting(
+            sample_data.ALTERNATING_MEETING,
+            sample_data.FIRST_WEDNESDAY_MEETING)
+
     def test_skip_meeting(self):
         meeting_yaml = sample_data.MEETING_WITH_SKIP_DATES
         # Copied from sample_data.MEETING_WITH_SKIP_DATES

yaml2ical/tests/test_recurrence.py

@@ -83,3 +83,25 @@ class RecurrenceTestCase(unittest.TestCase):
             self.assertEqual(
                 'Every four weeks on week %d of the four week rotation' % i,
                 str(recurrence.QuadWeeklyRecurrence(week=i)))
+
+    def test_monthly_first_week(self):
+        rec = recurrence.MonthlyRecurrence(week=1, day='Wednesday')
+        self.assertEqual(
+            datetime.datetime(2014, 11, 5, 2, 47, 28, 832666),
+            self.next_meeting(rec),
+        )
+
+    def test_monthly_second_week(self):
+        rec = recurrence.MonthlyRecurrence(week=2, day='Wednesday')
+        self.assertEqual(
+            datetime.datetime(2014, 11, 12, 2, 47, 28, 832666),
+            self.next_meeting(rec),
+        )
+
+    def test_monthly_invalid_week(self):
+        rec = recurrence.MonthlyRecurrence(week=6, day='Wednesday')
+        self.assertRaises(
+            ValueError,
+            self.next_meeting,
+            rec,
+        )