Update import of basic recurrence rules

Conversion of COUNT to UNTIL was a simple calculation which assumed one
repetiton per period (day, week, month or year); it does not take exception
days and invalid dates into account. Solved by a new function which returns the
n'th occurrence of a recurrence rule.

In calcurse UNTIL is interpreted as a day (DATE), in RFC 5545 as a time of day
(DATE-TIME). This has implications when a recurrence rule has an occurrence on
the UNTIL day, see comment in ical.c

An "Import:" note is added when a multi-day event is imported and turned into a
calcurse all-day event.

Icalendar quotes in comments have been updated to RFC 5545.

Signed-off-by: Lars Henriksen <LarsHenriksen@get2net.dk>
Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/recur.c b/src/recur.c
index d028d09..29e3dd8 100644
--- a/src/recur.c
+++ b/src/recur.c
@@ -1826,3 +1826,23 @@ int recur_next_occurrence(time_t s, long d, struct rpt *r, llist_t *e,
 	}
 	return ret;
 }
+
+/*
+ * Finds the nth occurrence of a recurrence rule (s, d, r, e) (incl. the start)
+ * and returns it in the provided buffer.
+ */
+int recur_nth_occurrence(time_t s, long d, struct rpt *r, llist_t *e, int n,
+			 time_t *nth)
+{
+	time_t day;
+
+	if (n <= 0)
+		return 0;
+
+	for (n--, *nth = s; n > 0; n--) {
+		day = update_time_in_date(*nth, 0, 0);
+		if (!recur_next_occurrence(s, d, r, e, day, nth))
+			break;
+	}
+	return !n;
+}