new files to implement iCalendar recurrence rules. These are only part

2000-05-20  Damon Chaplin  <damon@helixcode.com>

        * cal-util/cal-recur.[hc]: new files to implement iCalendar recurrence
        rules. These are only part finished, but people may like to check that
        the architecture seems OK.

2000-05-17  Damon Chaplin  <damon@helixcode.com>

        * gui/e-day-view.c (e_day_view_on_delete_occurrence):
        * gui/e-week-view.c (e_week_view_on_delete_occurrence): use a copy of
        the iCalObject so we detect the change in the "update_event" callback.
        Maybe we should just update the view ourselves and then we wouldn't
        need to detect any change in the callback.

        * cal-util/calobj.c (ical_object_reset_recurrence): new function to
        get rid of any recurrence rules. Used when we 'unrecur' an event.

        * gui/e-day-view.c (e_day_view_key_press): don't add a new event if it
        won't fit, or we end up adding a new event for each key press.
        (e_day_view_update_event_label): don't update it if it doesn't have
        an EText item (i.e. it isn't visible).

        * gui/e-day-view-time-item.c: allow selection of times using this
        column.

svn path=/trunk/; revision=3144

5 files changed, 1247 insertions, 0 deletions

diff --git a/calendar/cal-util/Makefile.am b/calendar/cal-util/Makefile.am
index 250cbf95c9..f110e96394 100644
--- a/calendar/cal-util/Makefile.am
+++ b/calendar/cal-util/Makefile.am
@@ -11,6 +11,7 @@ INCLUDES =						\
 lib_LTLIBRARIES = libcal-util.la
 
 libcal_util_la_SOURCES = \
+	cal-recur.c	\
 	cal-util.c	\
 	calobj.c	\
 	timeutil.c
@@ -18,6 +19,7 @@ libcal_util_la_SOURCES = \
 libcal_utilincludedir = $(includedir)/evolution/cal-util
 
 libcal_utilinclude_HEADERS =	\
+	cal-recur.h		\
 	cal-util.h		\
 	calobj.h		\
 	timeutil.h
diff --git a/calendar/cal-util/cal-recur.c b/calendar/cal-util/cal-recur.c
new file mode 100644
index 0000000000..711ef5e64d
--- /dev/null
+++ b/calendar/cal-util/cal-recur.c
@@ -0,0 +1,1131 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
+/*
+ * Evolution calendar recurrence rule functions
+ *
+ * Copyright (C) 2000 Helix Code, Inc.
+ *
+ * Author: Damon Chaplin <damon@helixcode.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <cal-util/cal-recur.h>
+#include <cal-util/timeutil.h>
+
+
+/*
+ * Introduction to The Recurrence Generation Functions:
+ *
+ * Note: This is pretty complicated. See the iCalendar spec (RFC 2445) for
+ *       the specification of the recurrence rules and lots of examples
+ *	 (sections 4.3.10 & 4.8.5). We also want to support the older
+ *	 vCalendar spec, though this should be easy since it is basically a
+ *	 subset of iCalendar.
+ *
+ * o An iCalendar event can have any number of recurrence rules specifying
+ *   occurrences of the event, as well as dates & times of specific
+ *   occurrences. It can also have any number of recurrence rules and
+ *   specific dates & times specifying exceptions to the occurrences.
+ *   So we first merge all the occurrences generated, eliminating any
+ *   duplicates, then we generate all the exceptions and remove these to
+ *   form the final set of occurrences.
+ *
+ * o There are 7 frequencies of occurrences: YEARLY, MONTHLY, WEEKLY, DAILY,
+ *   HOURLY, MINUTELY & SECONDLY. The 'interval' property specifies the
+ *   multiples of the frequency between each 'set' of occurrences. So for
+ *   a YEARLY frequency with an interval of 3, we generate a set of occurrences
+ *   for every 3rd year. We use complete years here -  any generated
+ *   occurrences that occur before the event's start (or after its end)
+ *   are just discarded.
+ *
+ * o There are 8 frequency modifiers: BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY,
+ *   BYDAY, BYHOUR & BYSECOND. These can either add extra occurrences or
+ *   filter out occurrences. For example 'FREQ=YEARLY;BYMONTH=1,2' produces
+ *   2 occurrences for each year rather than the default 1. And
+ *   'FREQ=DAILY; BYMONTH=1' filters out all occurrences except those in Jan.
+ *   If the modifier works on periods which are less than the recurrence
+ *   frequency, then extra occurrences are added, else occurrences are
+ *   filtered. So we have 2 functions for each modifier - one to expand events
+ *   and the other to filter. We use a table of functions for each frequency
+ *   which points to the appropriate function to use for each modifier.
+ *
+ * o Any number of frequency modifiers can be used in a recurrence rule
+ *   (though BYWEEKNO can only be used in a YEARLY rule). They are applied in
+ *   the order given above.
+ *
+ * o After the set of occurrences for the frequency interval are generated,
+ *   the BYSETPOS property is used to select which of the occurrences are
+ *   finally output. If BYSETPOS is not specified then all the occurrences are
+ *   output.
+ */
+
+
+#define CAL_OBJ_NUM_FILTERS	8
+
+typedef gboolean (*CalObjFindStartFn) (CalObjTime *event_start,
+				       CalObjTime *event_end,
+				       Recurrence *recur,
+				       CalObjTime *interval_start,
+				       CalObjTime *interval_end,
+				       CalObjTime *cotime);
+typedef gboolean (*CalObjFindNextFn)  (CalObjTime *cotime,
+				       CalObjTime *event_end,
+				       Recurrence *recur,
+				       CalObjTime *interval_end);
+typedef GArray* (*CalObjFilterFn)    (Recurrence *recur,
+				      GArray     *occs);
+
+typedef struct _CalObjRecurVTable CalObjRecurVTable;
+struct _CalObjRecurVTable {
+	CalObjFindStartFn find_start_position;
+	CalObjFindNextFn find_next_position;
+	CalObjFilterFn filters[CAL_OBJ_NUM_FILTERS];
+};
+
+
+static CalObjRecurVTable* cal_obj_get_vtable (Recurrence *recur);
+static void cal_obj_sort_occurrences (GArray *occs);
+static gint cal_obj_time_compare_func (const void *arg1,
+				       const void *arg2);
+static void cal_obj_remove_duplicates (GArray *occs);
+static GArray* cal_obj_bysetpos_filter (GArray *occs);
+
+
+static gboolean cal_obj_yearly_find_start_position (CalObjTime *event_start,
+						    CalObjTime *event_end,
+						    Recurrence *recur,
+						    CalObjTime *interval_start,
+						    CalObjTime *interval_end,
+						    CalObjTime *cotime);
+static gboolean cal_obj_yearly_find_next_position  (CalObjTime *cotime,
+						    CalObjTime *event_end,
+						    Recurrence *recur,
+						    CalObjTime *interval_end);
+
+static gboolean cal_obj_monthly_find_start_position (CalObjTime *event_start,
+						     CalObjTime *event_end,
+						     Recurrence *recur,
+						     CalObjTime *interval_start,
+						     CalObjTime *interval_end,
+						     CalObjTime *cotime);
+static gboolean cal_obj_monthly_find_next_position  (CalObjTime *cotime,
+						     CalObjTime *event_end,
+						     Recurrence *recur,
+						     CalObjTime *interval_end);
+
+static gboolean cal_obj_weekly_find_start_position (CalObjTime *event_start,
+						    CalObjTime *event_end,
+						    Recurrence *recur,
+						    CalObjTime *interval_start,
+						    CalObjTime *interval_end,
+						    CalObjTime *cotime);
+static gboolean cal_obj_weekly_find_next_position  (CalObjTime *cotime,
+						    CalObjTime *event_end,
+						    Recurrence *recur,
+						    CalObjTime *interval_end);
+
+static gboolean cal_obj_daily_find_start_position  (CalObjTime *event_start,
+						    CalObjTime *event_end,
+						    Recurrence *recur,
+						    CalObjTime *interval_start,
+						    CalObjTime *interval_end,
+						    CalObjTime *cotime);
+static gboolean cal_obj_daily_find_next_position   (CalObjTime *cotime,
+						    CalObjTime *event_end,
+						    Recurrence *recur,
+						    CalObjTime *interval_end);
+
+static gboolean cal_obj_hourly_find_start_position (CalObjTime *event_start,
+						    CalObjTime *event_end,
+						    Recurrence *recur,
+						    CalObjTime *interval_start,
+						    CalObjTime *interval_end,
+						    CalObjTime *cotime);
+static gboolean cal_obj_hourly_find_next_position  (CalObjTime *cotime,
+						    CalObjTime *event_end,
+						    Recurrence *recur,
+						    CalObjTime *interval_end);
+
+static gboolean cal_obj_minutely_find_start_position (CalObjTime *event_start,
+						      CalObjTime *event_end,
+						      Recurrence *recur,
+						      CalObjTime *interval_start,
+						      CalObjTime *interval_end,
+						      CalObjTime *cotime);
+static gboolean cal_obj_minutely_find_next_position  (CalObjTime *cotime,
+						      CalObjTime *event_end,
+						      Recurrence *recur,
+						      CalObjTime *interval_end);
+
+static gboolean cal_obj_secondly_find_start_position (CalObjTime *event_start,
+						      CalObjTime *event_end,
+						      Recurrence *recur,
+						      CalObjTime *interval_start,
+						      CalObjTime *interval_end,
+						      CalObjTime *cotime);
+static gboolean cal_obj_secondly_find_next_position  (CalObjTime *cotime,
+						      CalObjTime *event_end,
+						      Recurrence *recur,
+						      CalObjTime *interval_end);
+
+static GArray* cal_obj_bymonth_expand		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_bymonth_filter		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_byweekno_expand		(Recurrence *recur,
+						 GArray     *occs);
+#if 0
+/* This isn't used at present. */
+static GArray* cal_obj_byweekno_filter		(Recurrence *recur,
+						 GArray     *occs);
+#endif
+static GArray* cal_obj_byyearday_expand		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_byyearday_filter		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_bymonthday_expand	(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_bymonthday_filter	(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_byday_expand		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_byday_filter		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_byhour_expand		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_byhour_filter		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_byminute_expand		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_byminute_filter		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_bysecond_expand		(Recurrence *recur,
+						 GArray     *occs);
+static GArray* cal_obj_bysecond_filter		(Recurrence *recur,
+						 GArray     *occs);
+
+static void cal_obj_time_add_days (CalObjTime *cotime,
+				   gint	       days);
+
+
+CalObjRecurVTable cal_obj_yearly_vtable = {
+	cal_obj_yearly_find_start_position,
+	cal_obj_yearly_find_next_position,
+	{
+		cal_obj_bymonth_expand,
+		cal_obj_byweekno_expand,
+		cal_obj_byyearday_expand,
+		cal_obj_bymonthday_expand,
+		cal_obj_byday_expand,
+		cal_obj_byhour_expand,
+		cal_obj_byminute_expand,
+		cal_obj_bysecond_expand
+	},
+};
+
+CalObjRecurVTable cal_obj_monthly_vtable = {
+	cal_obj_monthly_find_start_position,
+	cal_obj_monthly_find_next_position,
+	{
+		cal_obj_bymonth_filter,
+		NULL,
+		cal_obj_byyearday_filter,
+		cal_obj_bymonthday_expand,
+		cal_obj_byday_expand,
+		cal_obj_byhour_expand,
+		cal_obj_byminute_expand,
+		cal_obj_bysecond_expand
+	},
+};
+
+CalObjRecurVTable cal_obj_weekly_vtable = {
+	cal_obj_weekly_find_start_position,
+	cal_obj_weekly_find_next_position,
+	{
+		cal_obj_bymonth_filter,
+		NULL,
+		cal_obj_byyearday_filter,
+		cal_obj_bymonthday_filter,
+		cal_obj_byday_expand,
+		cal_obj_byhour_expand,
+		cal_obj_byminute_expand,
+		cal_obj_bysecond_expand
+	},
+};
+
+CalObjRecurVTable cal_obj_daily_vtable = {
+	cal_obj_daily_find_start_position,
+	cal_obj_daily_find_next_position,
+	{
+		cal_obj_bymonth_filter,
+		NULL,
+		cal_obj_byyearday_filter,
+		cal_obj_bymonthday_filter,
+		cal_obj_byday_filter,
+		cal_obj_byhour_expand,
+		cal_obj_byminute_expand,
+		cal_obj_bysecond_expand
+	},
+};
+
+CalObjRecurVTable cal_obj_hourly_vtable = {
+	cal_obj_hourly_find_start_position,
+	cal_obj_hourly_find_next_position,
+	{
+		cal_obj_bymonth_filter,
+		NULL,
+		cal_obj_byyearday_filter,
+		cal_obj_bymonthday_filter,
+		cal_obj_byday_filter,
+		cal_obj_byhour_filter,
+		cal_obj_byminute_expand,
+		cal_obj_bysecond_expand
+	},
+};
+
+CalObjRecurVTable cal_obj_minutely_vtable = {
+	cal_obj_minutely_find_start_position,
+	cal_obj_minutely_find_next_position,
+	{
+		cal_obj_bymonth_filter,
+		NULL,
+		cal_obj_byyearday_filter,
+		cal_obj_bymonthday_filter,
+		cal_obj_byday_filter,
+		cal_obj_byhour_filter,
+		cal_obj_byminute_filter,
+		cal_obj_bysecond_expand
+	},
+};
+
+CalObjRecurVTable cal_obj_secondly_vtable = {
+	cal_obj_secondly_find_start_position,
+	cal_obj_secondly_find_next_position,
+	{
+		cal_obj_bymonth_filter,
+		NULL,
+		cal_obj_byyearday_filter,
+		cal_obj_bymonthday_filter,
+		cal_obj_byday_filter,
+		cal_obj_byhour_filter,
+		cal_obj_byminute_filter,
+		cal_obj_bysecond_filter
+	},
+};
+
+
+
+
+/* Returns an unsorted array of time_t's resulting from expanding the
+   recurrence within the given interval. Each iCalendar event can have any
+   number of recurrence rules specifying occurrences of the event, as well as
+   any number of recurrence rules specifying exceptions. */
+GArray*
+cal_obj_expand_recurrence		(CalObjTime	*event_start,
+					 CalObjTime	*event_end,
+					 Recurrence	*recur,
+					 CalObjTime	*interval_start,
+					 CalObjTime	*interval_end)
+{
+	CalObjRecurVTable *vtable;
+	CalObjTime occ;
+	GArray *all_occs, *occs;
+	gint filter;
+
+	vtable = cal_obj_get_vtable (recur);
+
+	/* This is the resulting array of CalObjTime elements. */
+	all_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+
+	/* Get the first period based on the frequency and the interval that
+	   intersects the interval between start and end. */
+	if ((*vtable->find_start_position) (event_start, event_end, recur,
+					    interval_start, interval_end,
+					    &occ))
+		return all_occs;
+
+	/* Loop until the event ends or we go past the end of the required
+	   interval. */
+	for (;;) {
+
+		/* We start with just the one time in the set. */
+		occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+		g_array_append_val (occs, occ);
+
+		/* Generate the set of occurrences for this period. */
+		for (filter = 0; filter < CAL_OBJ_NUM_FILTERS; filter++) {
+			if (vtable->filters[filter])
+				occs = (*vtable->filters[filter]) (recur,
+								   occs);
+		}
+
+		/* Sort the occurrences and remove duplicates. */
+		cal_obj_sort_occurrences (occs);
+		cal_obj_remove_duplicates (occs);
+
+		/* Apply the BYSETPOS property. */
+		occs = cal_obj_bysetpos_filter (occs);
+
+		/* Add the occurrences onto the main array. */
+		g_array_append_vals (all_occs, occs->data, occs->len);
+
+		/* Skip to the next period, or exit the loop if finished. */
+		if ((*vtable->find_next_position) (&occ, event_end, recur,
+						   interval_end))
+			break;
+	}
+
+	return all_occs;
+}
+
+
+/* Returns the function table corresponding to the recurrence frequency. */
+static CalObjRecurVTable*
+cal_obj_get_vtable (Recurrence *recur)
+{
+	switch (recur->type) {
+	case RECUR_YEARLY:
+		return &cal_obj_yearly_vtable;
+	case RECUR_MONTHLY:
+		return &cal_obj_monthly_vtable;
+	case RECUR_WEEKLY:
+		return &cal_obj_weekly_vtable;
+	case RECUR_DAILY:
+		return &cal_obj_daily_vtable;
+	case RECUR_HOURLY:
+		return &cal_obj_hourly_vtable;
+	case RECUR_MINUTELY:
+		return &cal_obj_minutely_vtable;
+	case RECUR_SECONDLY:
+		return &cal_obj_secondly_vtable;
+	}
+	return NULL;
+}
+
+
+static void
+cal_obj_sort_occurrences (GArray *occs)
+{
+	qsort (occs->data, occs->len, sizeof (CalObjTime),
+	       cal_obj_time_compare_func);
+}
+
+
+static gint
+cal_obj_time_compare_func (const void *arg1,
+			   const void *arg2)
+{
+	CalObjTime *cotime1, *cotime2;
+
+	cotime1 = (CalObjTime*) arg1;
+	cotime2 = (CalObjTime*) arg2;
+
+	if (cotime1->year < cotime2->year)
+		return -1;
+	if (cotime1->year > cotime2->year)
+		return 1;
+
+	if (cotime1->month < cotime2->month)
+		return -1;
+	if (cotime1->month > cotime2->month)
+		return 1;
+
+	if (cotime1->day < cotime2->day)
+		return -1;
+	if (cotime1->day > cotime2->day)
+		return 1;
+
+	if (cotime1->hour < cotime2->hour)
+		return -1;
+	if (cotime1->hour > cotime2->hour)
+		return 1;
+
+	if (cotime1->minute < cotime2->minute)
+		return -1;
+	if (cotime1->minute > cotime2->minute)
+		return 1;
+
+	if (cotime1->second < cotime2->second)
+		return -1;
+	if (cotime1->second > cotime2->second)
+		return 1;
+
+	return 0;
+}
+
+
+static void
+cal_obj_remove_duplicates (GArray *occs)
+{
+	CalObjTime *occ, *prev_occ = NULL;
+	gint len, i, j = 0;
+
+	len = occs->len;
+	for (i = 0; i < len; i++) {
+		occ = &g_array_index (occs, CalObjTime, i);
+
+		if (!prev_occ
+		    || cal_obj_time_compare_func (occ, prev_occ) != 0) {
+			if (i != j)
+				g_array_index (occs, CalObjTime, j)
+					= g_array_index (occs, CalObjTime, i);
+			j++;
+		}
+
+		prev_occ = occ;
+	}
+
+	g_array_set_size (occs, j);
+}
+
+
+static GArray*
+cal_obj_bysetpos_filter (GArray *occs)
+{
+
+	return occs;
+}
+
+
+
+
+static gboolean
+cal_obj_yearly_find_start_position (CalObjTime *event_start,
+				    CalObjTime *event_end,
+				    Recurrence *recur,
+				    CalObjTime *interval_start,
+				    CalObjTime *interval_end,
+				    CalObjTime *cotime)
+{
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_yearly_find_next_position (CalObjTime *cotime,
+				   CalObjTime *event_end,
+				   Recurrence *recur,
+				   CalObjTime *interval_end)
+{
+	/* NOTE: The day may now be invalid, e.g. 29th Feb.
+	   Make sure we remove these eventually. */
+	cotime->year += recur->interval;
+
+	if (cotime->year > event_end->year
+	    || cotime->year > interval_end->year)
+		return TRUE;
+
+	return FALSE;
+}
+
+
+
+static gboolean
+cal_obj_monthly_find_start_position (CalObjTime *event_start,
+				     CalObjTime *event_end,
+				     Recurrence *recur,
+				     CalObjTime *interval_start,
+				     CalObjTime *interval_end,
+				     CalObjTime *cotime)
+{
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_monthly_find_next_position (CalObjTime *cotime,
+				    CalObjTime *event_end,
+				    Recurrence *recur,
+				    CalObjTime *interval_end)
+{
+	cotime->month += recur->interval;
+	cotime->year += cotime->month / 12;
+	cotime->month %= 12;
+
+	if (cotime->year > event_end->year
+	    || cotime->year > interval_end->year
+	    || (cotime->year == event_end->year
+		&& cotime->month > event_end->month)
+	    || (cotime->year == interval_end->year
+		&& cotime->month > interval_end->month))
+		return TRUE;
+
+	return FALSE;
+}
+
+
+
+static gboolean
+cal_obj_weekly_find_start_position (CalObjTime *event_start,
+				    CalObjTime *event_end,
+				    Recurrence *recur,
+				    CalObjTime *interval_start,
+				    CalObjTime *interval_end,
+				    CalObjTime *cotime)
+{
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_weekly_find_next_position (CalObjTime *cotime,
+				   CalObjTime *event_end,
+				   Recurrence *recur,
+				   CalObjTime *interval_end)
+{
+	cal_obj_time_add_days (cotime, recur->interval);
+
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_daily_find_start_position  (CalObjTime *event_start,
+				    CalObjTime *event_end,
+				    Recurrence *recur,
+				    CalObjTime *interval_start,
+				    CalObjTime *interval_end,
+				    CalObjTime *cotime)
+{
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_daily_find_next_position  (CalObjTime *cotime,
+				   CalObjTime *event_end,
+				   Recurrence *recur,
+				   CalObjTime *interval_end)
+{
+
+	cal_obj_time_add_days (cotime, recur->interval);
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_hourly_find_start_position (CalObjTime *event_start,
+				    CalObjTime *event_end,
+				    Recurrence *recur,
+				    CalObjTime *interval_start,
+				    CalObjTime *interval_end,
+				    CalObjTime *cotime)
+{
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_hourly_find_next_position (CalObjTime *cotime,
+				   CalObjTime *event_end,
+				   Recurrence *recur,
+				   CalObjTime *interval_end)
+{
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_minutely_find_start_position (CalObjTime *event_start,
+				      CalObjTime *event_end,
+				      Recurrence *recur,
+				      CalObjTime *interval_start,
+				      CalObjTime *interval_end,
+				      CalObjTime *cotime)
+{
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_minutely_find_next_position (CalObjTime *cotime,
+				     CalObjTime *event_end,
+				     Recurrence *recur,
+				     CalObjTime *interval_end)
+{
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_secondly_find_start_position (CalObjTime *event_start,
+				      CalObjTime *event_end,
+				      Recurrence *recur,
+				      CalObjTime *interval_start,
+				      CalObjTime *interval_end,
+				      CalObjTime *cotime)
+{
+
+
+	return FALSE;
+}
+
+
+static gboolean
+cal_obj_secondly_find_next_position (CalObjTime *cotime,
+				     CalObjTime *event_end,
+				     Recurrence *recur,
+				     CalObjTime *interval_end)
+{
+
+
+	return FALSE;
+}
+
+
+
+
+
+/* If the BYMONTH rule is specified it expands each occurrence in occs, by
+   using each of the months in the bymonth list. */
+static GArray*
+cal_obj_bymonth_expand		(Recurrence *recur,
+				 GArray     *occs)
+{
+	GArray *new_occs;
+	CalObjTime *occ;
+	GList *elem;
+	gint len, i;
+
+	/* If BYMONTH has not been specified, or the array is empty, just
+	   return the array. */
+	if (!recur->bymonth || occs->len == 0)
+		return occs;
+
+	new_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+
+	len = occs->len;
+	for (i = 0; i < len; i++) {
+		occ = &g_array_index (occs, CalObjTime, i);
+
+		elem = recur->bymonth;
+		while (elem) {
+			/* NOTE: The day may now be invalid, e.g. 31st Feb.
+			   Make sure we remove these eventually. */
+			occ->month = GPOINTER_TO_INT (elem->data);
+			g_array_append_vals (new_occs, occ, 1);
+			elem = elem->next;
+		}
+	}
+
+	g_array_free (occs, TRUE);
+
+	return new_occs;
+}
+
+
+/* If the BYMONTH rule is specified it filters out all occurrences in occs
+   which do not match one of the months in the bymonth list. */
+static GArray*
+cal_obj_bymonth_filter		(Recurrence *recur,
+				 GArray     *occs)
+{
+	GArray *new_occs;
+	CalObjTime *occ;
+	guint8 months[12];
+	gint mon, len, i;
+	GList *elem;
+
+	/* If BYMONTH has not been specified, or the array is empty, just
+	   return the array. */
+	elem = recur->bymonth;
+	if (!elem || occs->len == 0)
+		return occs;
+
+	/* Create an array of months from bymonths for fast lookup. */
+	memset (&months, 0, sizeof (months));
+	while (elem) {
+		mon = GPOINTER_TO_INT (elem->data);
+		months[mon] = 1;
+		elem = elem->next;
+	}
+
+	new_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+
+	len = occs->len;
+	for (i = 0; i < len; i++) {
+		occ = &g_array_index (occs, CalObjTime, i);
+		if (months[occ->month])
+			g_array_append_vals (new_occs, occ, 1);
+	}
+
+	g_array_free (occs, TRUE);
+
+	return new_occs;
+}
+
+
+
+static GArray*
+cal_obj_byweekno_expand		(Recurrence *recur,
+				 GArray     *occs)
+{
+
+	return occs;
+}
+
+
+#if 0
+/* This isn't used at present. */
+static GArray*
+cal_obj_byweekno_filter		(Recurrence *recur,
+				 GArray     *occs)
+{
+
+	return occs;
+}
+#endif
+
+
+static GArray*
+cal_obj_byyearday_expand	(Recurrence *recur,
+				 GArray     *occs)
+{
+
+	return occs;
+}
+
+
+static GArray*
+cal_obj_byyearday_filter	(Recurrence *recur,
+				 GArray     *occs)
+{
+
+	return occs;
+}
+
+
+
+static GArray*
+cal_obj_bymonthday_expand	(Recurrence *recur,
+				 GArray     *occs)
+{
+
+	return occs;
+}
+
+
+static GArray*
+cal_obj_bymonthday_filter	(Recurrence *recur,
+				 GArray     *occs)
+{
+
+	return occs;
+}
+
+
+
+static GArray*
+cal_obj_byday_expand		(Recurrence *recur,
+				 GArray     *occs)
+{
+
+	return occs;
+}
+
+
+static GArray*
+cal_obj_byday_filter		(Recurrence *recur,
+				 GArray     *occs)
+{
+
+	return occs;
+}
+
+
+
+/* If the BYHOUR rule is specified it expands each occurrence in occs, by
+   using each of the hours in the byhour list. */
+static GArray*
+cal_obj_byhour_expand		(Recurrence *recur,
+				 GArray     *occs)
+{
+	GArray *new_occs;
+	CalObjTime *occ;
+	GList *elem;
+	gint len, i;
+
+	/* If BYHOUR has not been specified, or the array is empty, just
+	   return the array. */
+	if (!recur->byhour || occs->len == 0)
+		return occs;
+
+	new_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+
+	len = occs->len;
+	for (i = 0; i < len; i++) {
+		occ = &g_array_index (occs, CalObjTime, i);
+
+		elem = recur->byhour;
+		while (elem) {
+			occ->hour = GPOINTER_TO_INT (elem->data);
+			g_array_append_vals (new_occs, occ, 1);
+			elem = elem->next;
+		}
+	}
+
+	g_array_free (occs, TRUE);
+
+	return new_occs;
+}
+
+
+/* If the BYHOUR rule is specified it filters out all occurrences in occs
+   which do not match one of the hours in the byhour list. */
+static GArray*
+cal_obj_byhour_filter		(Recurrence *recur,
+				 GArray     *occs)
+{
+	GArray *new_occs;
+	CalObjTime *occ;
+	guint8 hours[24];
+	gint hour, len, i;
+	GList *elem;
+
+	/* If BYHOURUTE has not been specified, or the array is empty, just
+	   return the array. */
+	elem = recur->byhour;
+	if (!elem || occs->len == 0)
+		return occs;
+
+	/* Create an array of hours from byhour for fast lookup. */
+	memset (&hours, 0, sizeof (hours));
+	while (elem) {
+		hour = GPOINTER_TO_INT (elem->data);
+		hours[hour] = 1;
+		elem = elem->next;
+	}
+
+	new_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+
+	len = occs->len;
+	for (i = 0; i < len; i++) {
+		occ = &g_array_index (occs, CalObjTime, i);
+		if (hours[occ->hour])
+			g_array_append_vals (new_occs, occ, 1);
+	}
+
+	g_array_free (occs, TRUE);
+
+	return new_occs;
+}
+
+
+
+/* If the BYMINUTE rule is specified it expands each occurrence in occs, by
+   using each of the minutes in the byminute list. */
+static GArray*
+cal_obj_byminute_expand		(Recurrence *recur,
+				 GArray     *occs)
+{
+	GArray *new_occs;
+	CalObjTime *occ;
+	GList *elem;
+	gint len, i;
+
+	/* If BYMINUTE has not been specified, or the array is empty, just
+	   return the array. */
+	if (!recur->byminute || occs->len == 0)
+		return occs;
+
+	new_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+
+	len = occs->len;
+	for (i = 0; i < len; i++) {
+		occ = &g_array_index (occs, CalObjTime, i);
+
+		elem = recur->byminute;
+		while (elem) {
+			occ->minute = GPOINTER_TO_INT (elem->data);
+			g_array_append_vals (new_occs, occ, 1);
+			elem = elem->next;
+		}
+	}
+
+	g_array_free (occs, TRUE);
+
+	return new_occs;
+}
+
+
+/* If the BYMINUTE rule is specified it filters out all occurrences in occs
+   which do not match one of the minutes in the byminute list. */
+static GArray*
+cal_obj_byminute_filter		(Recurrence *recur,
+				 GArray     *occs)
+{
+	GArray *new_occs;
+	CalObjTime *occ;
+	guint8 minutes[60];
+	gint min, len, i;
+	GList *elem;
+
+	/* If BYMINUTE has not been specified, or the array is empty, just
+	   return the array. */
+	elem = recur->byminute;
+	if (!elem || occs->len == 0)
+		return occs;
+
+	/* Create an array of minutes from byminutes for fast lookup. */
+	memset (&minutes, 0, sizeof (minutes));
+	while (elem) {
+		min = GPOINTER_TO_INT (elem->data);
+		minutes[min] = 1;
+		elem = elem->next;
+	}
+
+	new_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+
+	len = occs->len;
+	for (i = 0; i < len; i++) {
+		occ = &g_array_index (occs, CalObjTime, i);
+		if (minutes[occ->minute])
+			g_array_append_vals (new_occs, occ, 1);
+	}
+
+	g_array_free (occs, TRUE);
+
+	return new_occs;
+}
+
+
+
+/* If the BYSECOND rule is specified it expands each occurrence in occs, by
+   using each of the seconds in the bysecond list. */
+static GArray*
+cal_obj_bysecond_expand		(Recurrence *recur,
+				 GArray     *occs)
+{
+	GArray *new_occs;
+	CalObjTime *occ;
+	GList *elem;
+	gint len, i;
+
+	/* If BYSECOND has not been specified, or the array is empty, just
+	   return the array. */
+	if (!recur->bysecond || occs->len == 0)
+		return occs;
+
+	new_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+
+	len = occs->len;
+	for (i = 0; i < len; i++) {
+		occ = &g_array_index (occs, CalObjTime, i);
+
+		elem = recur->bysecond;
+		while (elem) {
+			occ->second = GPOINTER_TO_INT (elem->data);
+			g_array_append_vals (new_occs, occ, 1);
+			elem = elem->next;
+		}
+	}
+
+	g_array_free (occs, TRUE);
+
+	return new_occs;
+}
+
+
+/* If the BYSECOND rule is specified it filters out all occurrences in occs
+   which do not match one of the seconds in the bysecond list. */
+static GArray*
+cal_obj_bysecond_filter		(Recurrence *recur,
+				 GArray     *occs)
+{
+	GArray *new_occs;
+	CalObjTime *occ;
+	guint8 seconds[61];
+	gint sec, len, i;
+	GList *elem;
+
+	/* If BYSECOND has not been specified, or the array is empty, just
+	   return the array. */
+	elem = recur->bysecond;
+	if (!elem || occs->len == 0)
+		return occs;
+
+	/* Create an array of seconds from byseconds for fast lookup. */
+	memset (&seconds, 0, sizeof (seconds));
+	while (elem) {
+		sec = GPOINTER_TO_INT (elem->data);
+		seconds[sec] = 1;
+		elem = elem->next;
+	}
+
+	new_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
+
+	len = occs->len;
+	for (i = 0; i < len; i++) {
+		occ = &g_array_index (occs, CalObjTime, i);
+		if (seconds[occ->second])
+			g_array_append_vals (new_occs, occ, 1);
+	}
+
+	g_array_free (occs, TRUE);
+
+	return new_occs;
+}
+
+
+
+static void
+cal_obj_time_add_days (CalObjTime *cotime,
+		       gint	   days)
+{
+	guint day, days_in_month;
+
+	/* We use a guint to avoid overflow on the guint8. */
+	day = (guint) cotime->day;
+	day += days;
+
+	for (;;) {
+		days_in_month = time_days_in_month (cotime->year,
+						    cotime->month);
+		if (day <= days_in_month)
+			break;
+
+		cotime->month++;
+		if (cotime->month >= 12) {
+			cotime->year++;
+			cotime->month = 0;
+		}
+
+		day -= days_in_month;
+	}
+
+	cotime->day = (guint8) day;
+}
diff --git a/calendar/cal-util/cal-recur.h b/calendar/cal-util/cal-recur.h
new file mode 100644
index 0000000000..340b897417
--- /dev/null
+++ b/calendar/cal-util/cal-recur.h
@@ -0,0 +1,102 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
+/*
+ * Evolution calendar recurrence rule functions
+ *
+ * Copyright (C) 2000 Helix Code, Inc.
+ *
+ * Author: Damon Chaplin <damon@helixcode.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#ifndef CAL_RECURL_H
+#define CAL_RECUR_H
+
+#include <libgnome/gnome-defs.h>
+#include <glib.h>
+
+BEGIN_GNOME_DECLS
+
+
+/* FIXME: I've put modified versions of RecurType and Recurrence here, since
+   the ones in calobj.h don't support all of iCalendar. Hopefully Seth will
+   update those soon and these can be removed. */
+
+enum RecurType {
+	RECUR_YEARLY,
+	RECUR_MONTHLY,
+	RECUR_WEEKLY,
+	RECUR_DAILY,
+	RECUR_HOURLY,
+	RECUR_MINUTELY,
+	RECUR_SECONDLY,
+};
+
+typedef struct {
+	enum RecurType type;
+
+	int            interval;
+
+	int            weekday;
+
+	int	       month_pos;
+
+	int	       month_day;
+
+
+	/* For BYMONTH modifier. A list of GINT_TO_POINTERs, 0-11. */
+	GList	      *bymonth;
+
+
+	/* For BYHOUR modifier. A list of GINT_TO_POINTERs, 0-23. */
+	GList	      *byhour;
+
+	/* For BYMINUTE modifier. A list of GINT_TO_POINTERs, 0-59. */
+	GList	      *byminute;
+
+	/* For BYSECOND modifier. A list of GINT_TO_POINTERs, 0-60. */
+	GList	      *bysecond;
+
+} Recurrence;
+
+
+
+/* This is what we use to represent a date & time. */
+typedef struct _CalObjTime CalObjTime;
+struct _CalObjTime {
+	guint16 year;
+	guint8 month;		/* 0 - 11 */
+	guint8 day;		/* 1 - 31 */
+	guint8 hour;		/* 0 - 23 */
+	guint8 minute;		/* 0 - 59 */
+	guint8 second;		/* 0 - 59 (maybe 60 for leap second) */
+};
+
+
+
+/* Returns an unsorted array of time_t's resulting from expanding the
+   recurrence within the given interval. Each iCalendar event can have any
+   number of recurrence rules specifying occurrences of the event, as well as
+   any number of recurrence rules specifying exceptions. */
+GArray*
+cal_obj_expand_recurrence		(CalObjTime	*event_start,
+					 CalObjTime	*event_end,
+					 Recurrence	*recur,
+					 CalObjTime	*interval_start,
+					 CalObjTime	*interval_end);
+
+END_GNOME_DECLS
+
+#endif
diff --git a/calendar/cal-util/calobj.c b/calendar/cal-util/calobj.c
index 4a3afd81ec..d2c47fbc65 100644
--- a/calendar/cal-util/calobj.c
+++ b/calendar/cal-util/calobj.c
@@ -157,6 +157,14 @@ ical_object_destroy (iCalObject *ico)
 	g_free (ico);
 }
 
+/* This resets any recurrence rules of the iCalObject. */
+void
+ical_object_reset_recurrence (iCalObject *ico)
+{
+	free_if_defined  (ico->recur);
+	lfree_if_defined (ico->exdate);
+}
+
 static GList *
 set_list (char *str)
 {
diff --git a/calendar/cal-util/calobj.h b/calendar/cal-util/calobj.h
index e44b2ad7b1..cf5483a228 100644
--- a/calendar/cal-util/calobj.h
+++ b/calendar/cal-util/calobj.h
@@ -277,6 +277,10 @@ gboolean    ical_object_compare_dates (iCalObject *ico1, iCalObject *ico2);
 /* Generates a new uid for a calendar object. Should be g_free'd eventually. */
 char	   *ical_gen_uid (void);
 
+/* This resets any recurrence rules of the iCalObject. */
+void	    ical_object_reset_recurrence (iCalObject *ico);
+
+
 END_GNOME_DECLS
 
 #endif