fix(calendar-sync): honor BYDAY rules and drop cancelled events

The expander ignored BYDAY on monthly and yearly rules and stepped DTSTART's day-of-month instead, so a "2nd Wednesday" series rendered on the 12th of every month, the wrong weekday most months. It now resolves nth-weekday entries (2WE, -1TU), bare weekdays with BYSETPOS, and yearly BYMONTH+BYDAY, so each occurrence lands on the day the rule names.

Nothing read the VEVENT STATUS property, so cancelled events rendered as normal meetings: a cancelled instance of a series reappeared at its original time, and standalone cancelled events stayed on the agenda. parse-event now drops STATUS:CANCELLED events, which also kills cancelled series masters. A cancelled RECURRENCE-ID override removes its occurrence instead of overriding it.

The fixes are coupled: until BYDAY generates the right dates, a cancelled override can't match the occurrence it removes.

1 files changed, 21 insertions, 0 deletions

diff --git a/tests/test-calendar-sync--parse-rrule.el b/tests/test-calendar-sync--parse-rrule.el
index 099e4e44..2668c1ac 100644
--- a/tests/test-calendar-sync--parse-rrule.el
+++ b/tests/test-calendar-sync--parse-rrule.el
@@ -206,5 +206,26 @@
         (should (= (plist-get result :count) 10)))
     (test-calendar-sync--parse-rrule-teardown)))
 
+;;; BYSETPOS / BYMONTH Cases
+
+(ert-deftest test-calendar-sync--parse-rrule-normal-bysetpos-returns-number ()
+  "Normal: BYSETPOS parses to a number (Proton emits BYDAY=SU;BYSETPOS=2)."
+  (let ((result (calendar-sync--parse-rrule "FREQ=MONTHLY;BYDAY=SU;BYSETPOS=2")))
+    (should (eq (plist-get result :freq) 'monthly))
+    (should (equal (plist-get result :byday) '("SU")))
+    (should (= (plist-get result :bysetpos) 2))))
+
+(ert-deftest test-calendar-sync--parse-rrule-normal-bymonth-returns-number ()
+  "Normal: BYMONTH parses to a number (yearly nth-weekday rules carry it)."
+  (let ((result (calendar-sync--parse-rrule "FREQ=YEARLY;BYMONTH=3;BYDAY=2SU")))
+    (should (eq (plist-get result :freq) 'yearly))
+    (should (= (plist-get result :bymonth) 3))
+    (should (equal (plist-get result :byday) '("2SU")))))
+
+(ert-deftest test-calendar-sync--parse-rrule-boundary-negative-bysetpos ()
+  "Boundary: negative BYSETPOS (last matching day) parses."
+  (let ((result (calendar-sync--parse-rrule "FREQ=MONTHLY;BYDAY=FR;BYSETPOS=-1")))
+    (should (= (plist-get result :bysetpos) -1))))
+
 (provide 'test-calendar-sync--parse-rrule)
 ;;; test-calendar-sync--parse-rrule.el ends here