/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 * Evolution calendar recurrence rule functions
 *
 * Copyright (C) 2000 Ximian, Inc.
 *
 * Author: Damon Chaplin <damon@ximian.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU Lesser General Public
 * License as published by the Free Software Foundation.
 *
 * 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser 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.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#include <string.h>
#include <glib.h>
#include <glib/gi18n-lib.h>
#include "e-cal-recur.h"
#include "e-cal-time-util.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 which we step by. We generate a 'set' of
 *   occurrences for each period defined by the frequency & interval.
 *   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, BYMINUTE & 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, otherwise 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 the iCalendar spec says that BYWEEKNO can only be used in a YEARLY
 *   rule, and some modifiers aren't appropriate for some frequencies - e.g.
 *   BYMONTHDAY is not really useful in a WEEKLY frequency, and BYYEARDAY is
 *   not useful in a MONTHLY or WEEKLY frequency).
 *   The frequency modifiers are applied in the order given above. The first 5
 *   modifier rules (BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY & BYDAY) all
 *   produce the days on which the occurrences take place, and so we have to
 *   compute some of these in parallel rather than sequentially, or we may end
 *   up with too many days.
 *
 * o Note that some expansion functions may produce days which are invalid,
 *   e.g. 31st September, 30th Feb. These invalid days are removed before the
 *   BYHOUR, BYMINUTE & BYSECOND modifier functions are applied.
 *
 * 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.
 *
 *
 * FIXME: I think there are a few errors in this code:
 *
 *  1) I'm not sure it should be generating events in parallel like it says
 *     above. That needs to be checked.
 *
 *  2) I didn't think about timezone changes when implementing this. I just
 *     assumed all the occurrences of the event would be in local time.
 *     But when clocks go back or forwards due to daylight-saving time, some
 *     special handling may be needed, especially for the shorter frequencies.
 *     e.g. for a MINUTELY frequency it should probably iterate over all the
 *     minutes before and after clocks go back (i.e. some may be the same local
 *     time but have different UTC offsets). For longer frequencies, if an
 *     occurrence lands on the overlapping or non-existant time when clocks
 *     go back/forward, then it may need to choose which of the times to use
 *     or move the time forward or something. I'm not sure this is clear in the
 *     spec.
 */

/* This is the maximum year we will go up to (inclusive). Since we use time_t
   values we can't go past 2037 anyway, and some of our VTIMEZONEs may stop
   at 2037 as well. */
#define MAX_YEAR	2037

/* Define this for some debugging output. */
#if 0
#define CAL_OBJ_DEBUG	1
#endif

/* We will use icalrecurrencetype instead of this eventually. */
typedef struct {
	icalrecurrencetype_frequency freq;

	int            interval;

	/* Specifies the end of the recurrence, inclusive. No occurrences are
	   generated after this date. If it is 0, the event recurs forever. */
	time_t         enddate;

	/* WKST property - the week start day: 0 = Monday to 6 = Sunday. */
	gint	       week_start_day;


	/* NOTE: I've used GList's here, but it doesn't matter if we use
	   other data structures like arrays. The code should be easy to
	   change. So long as it is easy to see if the modifier is set. */

	/* For BYMONTH modifier. A list of GINT_TO_POINTERs, 0-11. */
	GList	      *bymonth;

	/* For BYWEEKNO modifier. A list of GINT_TO_POINTERs, [+-]1-53. */
	GList	      *byweekno;

	/* For BYYEARDAY modifier. A list of GINT_TO_POINTERs, [+-]1-366. */
	GList	      *byyearday;

	/* For BYMONTHDAY modifier. A list of GINT_TO_POINTERs, [+-]1-31. */
	GList	      *bymonthday;

	/* For BYDAY modifier. A list of GINT_TO_POINTERs, in pairs.
	   The first of each pair is the weekday, 0 = Monday to 6 = Sunday.
	   The second of each pair is the week number [+-]0-53. */
	GList	      *byday;

	/* 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;

	/* For BYSETPOS modifier. A list of GINT_TO_POINTERs, +ve or -ve. */
	GList	      *bysetpos;
} ECalRecurrence;

/* This is what we use to pass to all the filter functions. */
typedef struct _RecurData RecurData;
struct _RecurData {
	ECalRecurrence *recur;

	/* This is used for the WEEKLY frequency. It is the offset from the
	   week_start_day. */
	gint weekday_offset;

	/* This is used for fast lookup in BYMONTH filtering. */
	guint8 months[12];

	/* This is used for fast lookup in BYYEARDAY filtering. */
	guint8 yeardays[367], neg_yeardays[367]; /* Days are 1 - 366. */

	/* This is used for fast lookup in BYMONTHDAY filtering. */
	guint8 monthdays[32], neg_monthdays[32]; /* Days are 1 to 31. */

	/* This is used for fast lookup in BYDAY filtering. */
	guint8 weekdays[7];

	/* This is used for fast lookup in BYHOUR filtering. */
	guint8 hours[24];

	/* This is used for fast lookup in BYMINUTE filtering. */
	guint8 minutes[60];

	/* This is used for fast lookup in BYSECOND filtering. */
	guint8 seconds[62];
};

/* 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 up to 61 for leap seconds) */
	guint8 flags;		/* The meaning of this depends on where the
				   CalObjTime is used. In most cases this is
				   set to TRUE to indicate that this is an
				   RDATE with an end or a duration set.
				   In the exceptions code, this is set to TRUE
				   to indicate that this is an EXDATE with a
				   DATE value. */
};

/* This is what we use to represent specific recurrence dates.
   Note that we assume it starts with a CalObjTime when sorting. */
typedef struct _CalObjRecurrenceDate CalObjRecurrenceDate;
struct _CalObjRecurrenceDate {
	CalObjTime start;
	ECalComponentPeriod *period;
};

/* The paramter we use to store the enddate in RRULE and EXRULE properties. */
#define EVOLUTION_END_DATE_PARAMETER	"X-EVOLUTION-ENDDATE"

typedef gboolean (*CalObjFindStartFn) (CalObjTime *event_start,
				       CalObjTime *event_end,
				       RecurData  *recur_data,
				       CalObjTime *interval_start,
				       CalObjTime *interval_end,
				       CalObjTime *cotime);
typedef gboolean (*CalObjFindNextFn)  (CalObjTime *cotime,
				       CalObjTime *event_end,
				       RecurData  *recur_data,
				       CalObjTime *interval_end);
typedef GArray*	 (*CalObjFilterFn)    (RecurData  *recur_data,
				       GArray     *occs);

typedef struct _ECalRecurVTable ECalRecurVTable;
struct _ECalRecurVTable {
	CalObjFindStartFn find_start_position;
	CalObjFindNextFn find_next_position;

	CalObjFilterFn bymonth_filter;
	CalObjFilterFn byweekno_filter;
	CalObjFilterFn byyearday_filter;
	CalObjFilterFn bymonthday_filter;
	CalObjFilterFn byday_filter;
	CalObjFilterFn byhour_filter;
	CalObjFilterFn byminute_filter;
	CalObjFilterFn bysecond_filter;
};


/* This is used to specify which parts of the CalObjTime to compare in
   cal_obj_time_compare(). */
typedef enum {
	CALOBJ_YEAR,
	CALOBJ_MONTH,
	CALOBJ_DAY,
	CALOBJ_HOUR,
	CALOBJ_MINUTE,
	CALOBJ_SECOND
} CalObjTimeComparison;

static void e_cal_recur_generate_instances_of_rule (ECalComponent	*comp,
						  icalproperty	*prop,
						  time_t	 start,
						  time_t	 end,
						  ECalRecurInstanceFn cb,
						  gpointer       cb_data,
						  ECalRecurResolveTimezoneFn  tz_cb,
						  gpointer	 tz_cb_data,
						  icaltimezone	*default_timezone);

static ECalRecurrence * e_cal_recur_from_icalproperty (icalproperty *prop,
						    gboolean exception,
						    icaltimezone *zone,
						    gboolean convert_end_date);
static gint e_cal_recur_ical_weekday_to_weekday	(enum icalrecurrencetype_weekday day);
static void	e_cal_recur_free			(ECalRecurrence	*r);


static gboolean cal_object_get_rdate_end	(CalObjTime	*occ,
						 GArray		*rdate_periods);
static void	cal_object_compute_duration	(CalObjTime	*start,
						 CalObjTime	*end,
						 gint		*days,
						 gint		*seconds);

static gboolean generate_instances_for_chunk	(ECalComponent		*comp,
						 time_t			 comp_dtstart,
						 icaltimezone		*zone,
						 GSList			*rrules,
						 GSList			*rdates,
						 GSList			*exrules,
						 GSList			*exdates,
						 gboolean		 single_rule,
						 CalObjTime		*event_start,
						 time_t			 interval_start,
						 CalObjTime		*chunk_start,
						 CalObjTime		*chunk_end,
						 gint			 duration_days,
						 gint			 duration_seconds,
						 gboolean		 convert_end_date,
						 ECalRecurInstanceFn	 cb,
						 gpointer		 cb_data);

static GArray* cal_obj_expand_recurrence	(CalObjTime	  *event_start,
						 icaltimezone	  *zone,
						 ECalRecurrence	  *recur,
						 CalObjTime	  *interval_start,
						 CalObjTime	  *interval_end,
						 gboolean	  *finished);

static GArray*	cal_obj_generate_set_yearly	(RecurData	*recur_data,
						 ECalRecurVTable *vtable,
						 CalObjTime	*occ);
static GArray*	cal_obj_generate_set_monthly	(RecurData	*recur_data,
						 ECalRecurVTable *vtable,
						 CalObjTime	*occ);
static GArray*	cal_obj_generate_set_default	(RecurData	*recur_data,
						 ECalRecurVTable *vtable,
						 CalObjTime	*occ);


static ECalRecurVTable* cal_obj_get_vtable	(icalrecurrencetype_frequency recur_type);
static void	cal_obj_initialize_recur_data	(RecurData	*recur_data,
						 ECalRecurrence	*recur,
						 CalObjTime	*event_start);
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_and_invalid_dates (GArray	*occs);
static void	cal_obj_remove_exceptions	(GArray		*occs,
						 GArray		*ex_occs);
static GArray*	cal_obj_bysetpos_filter		(ECalRecurrence	*recur,
						 GArray		*occs);


static gboolean cal_obj_yearly_find_start_position (CalObjTime *event_start,
						    CalObjTime *event_end,
						    RecurData  *recur_data,
						    CalObjTime *interval_start,
						    CalObjTime *interval_end,
						    CalObjTime *cotime);
static gboolean cal_obj_yearly_find_next_position  (CalObjTime *cotime,
						    CalObjTime *event_end,
						    RecurData  *recur_data,
						    CalObjTime *interval_end);

static gboolean cal_obj_monthly_find_start_position (CalObjTime *event_start,
						     CalObjTime *event_end,
						     RecurData  *recur_data,
						     CalObjTime *interval_start,
						     CalObjTime *interval_end,
						     CalObjTime *cotime);
static gboolean cal_obj_monthly_find_next_position  (CalObjTime *cotime,
						     CalObjTime *event_end,
						     RecurData  *recur_data,
						     CalObjTime *interval_end);

static gboolean cal_obj_weekly_find_start_position (CalObjTime *event_start,
						    CalObjTime *event_end,
						    RecurData  *recur_data,
						    CalObjTime *interval_start,
						    CalObjTime *interval_end,
						    CalObjTime *cotime);
static gboolean cal_obj_weekly_find_next_position  (CalObjTime *cotime,
						    CalObjTime *event_end,
						    RecurData  *recur_data,
						    CalObjTime *interval_end);

static gboolean cal_obj_daily_find_start_position  (CalObjTime *event_start,
						    CalObjTime *event_end,
						    RecurData  *recur_data,
						    CalObjTime *interval_start,
						    CalObjTime *interval_end,
						    CalObjTime *cotime);
static gboolean cal_obj_daily_find_next_position   (CalObjTime *cotime,
						    CalObjTime *event_end,
						    RecurData  *recur_data,
						    CalObjTime *interval_end);

static gboolean cal_obj_hourly_find_start_position (CalObjTime *event_start,
						    CalObjTime *event_end,
						    RecurData  *recur_data,
						    CalObjTime *interval_start,
						    CalObjTime *interval_end,
						    CalObjTime *cotime);
static gboolean cal_obj_hourly_find_next_position  (CalObjTime *cotime,
						    CalObjTime *event_end,
						    RecurData  *recur_data,
						    CalObjTime *interval_end);

static gboolean cal_obj_minutely_find_start_position (CalObjTime *event_start,
						      CalObjTime *event_end,
						      RecurData  *recur_data,
						      CalObjTime *interval_start,
						      CalObjTime *interval_end,
						      CalObjTime *cotime);
static gboolean cal_obj_minutely_find_next_position  (CalObjTime *cotime,
						      CalObjTime *event_end,
						      RecurData  *recur_data,
						      CalObjTime *interval_end);

static gboolean cal_obj_secondly_find_start_position (CalObjTime *event_start,
						      CalObjTime *event_end,
						      RecurData  *recur_data,
						      CalObjTime *interval_start,
						      CalObjTime *interval_end,
						      CalObjTime *cotime);
static gboolean cal_obj_secondly_find_next_position  (CalObjTime *cotime,
						      CalObjTime *event_end,
						      RecurData  *recur_data,
						      CalObjTime *interval_end);

static GArray* cal_obj_bymonth_expand		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_bymonth_filter		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byweekno_expand		(RecurData  *recur_data,
						 GArray     *occs);
#if 0
/* This isn't used at present. */
static GArray* cal_obj_byweekno_filter		(RecurData  *recur_data,
						 GArray     *occs);
#endif
static GArray* cal_obj_byyearday_expand		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byyearday_filter		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_bymonthday_expand	(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_bymonthday_filter	(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byday_expand_yearly	(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byday_expand_monthly	(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byday_expand_weekly	(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byday_filter		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byhour_expand		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byhour_filter		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byminute_expand		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_byminute_filter		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_bysecond_expand		(RecurData  *recur_data,
						 GArray     *occs);
static GArray* cal_obj_bysecond_filter		(RecurData  *recur_data,
						 GArray     *occs);

static void cal_obj_time_add_months		(CalObjTime *cotime,
						 gint	     months);
static void cal_obj_time_add_days		(CalObjTime *cotime,
						 gint	     days);
static void cal_obj_time_add_hours		(CalObjTime *cotime,
						 gint	     hours);
static void cal_obj_time_add_minutes		(CalObjTime *cotime,
						 gint	     minutes);
static void cal_obj_time_add_seconds		(CalObjTime *cotime,
						 gint	     seconds);
static gint cal_obj_time_compare		(CalObjTime *cotime1,
						 CalObjTime *cotime2,
						 CalObjTimeComparison type);
static gint cal_obj_time_weekday		(CalObjTime *cotime);
static gint cal_obj_time_weekday_offset		(CalObjTime *cotime,
						 ECalRecurrence *recur);
static gint cal_obj_time_day_of_year		(CalObjTime *cotime);
static void cal_obj_time_find_first_week	(CalObjTime *cotime,
						 RecurData  *recur_data);
static void cal_object_time_from_time		(CalObjTime *cotime,
						 time_t      t,
						 icaltimezone *zone);
static gint cal_obj_date_only_compare_func	(const void *arg1,
						 const void *arg2);



static gboolean e_cal_recur_ensure_end_dates	(ECalComponent	*comp,
						 gboolean	 refresh,
						 ECalRecurResolveTimezoneFn tz_cb,
						 gpointer	 tz_cb_data);
static gboolean e_cal_recur_ensure_rule_end_date	(ECalComponent	*comp,
						 icalproperty	*prop,
						 gboolean	 exception,
						 gboolean	 refresh,
						 ECalRecurResolveTimezoneFn tz_cb,
						 gpointer	 tz_cb_data);
static gboolean e_cal_recur_ensure_rule_end_date_cb	(ECalComponent	*comp,
							 time_t		 instance_start,
							 time_t		 instance_end,
							 gpointer	 data);
static time_t e_cal_recur_get_rule_end_date	(icalproperty	*prop,
						 icaltimezone	*default_timezone);
static void e_cal_recur_set_rule_end_date		(icalproperty	*prop,
						 time_t		 end_date);


#ifdef CAL_OBJ_DEBUG
static char* cal_obj_time_to_string		(CalObjTime	*cotime);
#endif


ECalRecurVTable 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_yearly,
	cal_obj_byhour_expand,
	cal_obj_byminute_expand,
	cal_obj_bysecond_expand
};

ECalRecurVTable cal_obj_monthly_vtable = {
	cal_obj_monthly_find_start_position,
	cal_obj_monthly_find_next_position,

	cal_obj_bymonth_filter,
	NULL, /* BYWEEKNO is only applicable to YEARLY frequency. */
	NULL, /* BYYEARDAY is not useful in a MONTHLY frequency. */
	cal_obj_bymonthday_expand,
	cal_obj_byday_expand_monthly,
	cal_obj_byhour_expand,
	cal_obj_byminute_expand,
	cal_obj_bysecond_expand
};

ECalRecurVTable cal_obj_weekly_vtable = {
	cal_obj_weekly_find_start_position,
	cal_obj_weekly_find_next_position,

	cal_obj_bymonth_filter,
	NULL, /* BYWEEKNO is only applicable to YEARLY frequency. */
	NULL, /* BYYEARDAY is not useful in a WEEKLY frequency. */
	NULL, /* BYMONTHDAY is not useful in a WEEKLY frequency. */
	cal_obj_byday_expand_weekly,
	cal_obj_byhour_expand,
	cal_obj_byminute_expand,
	cal_obj_bysecond_expand
};

ECalRecurVTable cal_obj_daily_vtable = {
	cal_obj_daily_find_start_position,
	cal_obj_daily_find_next_position,

	cal_obj_bymonth_filter,
	NULL, /* BYWEEKNO is only applicable to YEARLY frequency. */
	cal_obj_byyearday_filter,
	cal_obj_bymonthday_filter,
	cal_obj_byday_filter,
	cal_obj_byhour_expand,
	cal_obj_byminute_expand,
	cal_obj_bysecond_expand
};

ECalRecurVTable cal_obj_hourly_vtable = {
	cal_obj_hourly_find_start_position,
	cal_obj_hourly_find_next_position,

	cal_obj_bymonth_filter,
	NULL, /* BYWEEKNO is only applicable to YEARLY frequency. */
	cal_obj_byyearday_filter,
	cal_obj_bymonthday_filter,
	cal_obj_byday_filter,
	cal_obj_byhour_filter,
	cal_obj_byminute_expand,
	cal_obj_bysecond_expand
};

ECalRecurVTable cal_obj_minutely_vtable = {
	cal_obj_minutely_find_start_position,
	cal_obj_minutely_find_next_position,

	cal_obj_bymonth_filter,
	NULL, /* BYWEEKNO is only applicable to YEARLY frequency. */
	cal_obj_byyearday_filter,
	cal_obj_bymonthday_filter,
	cal_obj_byday_filter,
	cal_obj_byhour_filter,
	cal_obj_byminute_filter,
	cal_obj_bysecond_expand
};

ECalRecurVTable cal_obj_secondly_vtable = {
	cal_obj_secondly_find_start_position,
	cal_obj_secondly_find_next_position,

	cal_obj_bymonth_filter,
	NULL, /* BYWEEKNO is only applicable to YEARLY frequency. */
	cal_obj_byyearday_filter,
	cal_obj_bymonthday_filter,
	cal_obj_byday_filter,
	cal_obj_byhour_filter,
	cal_obj_byminute_filter,
	cal_obj_bysecond_filter
};

/**
 * e_cal_recur_generate_instances:
 * @comp: A calendar component object.
 * @start: Range start time.
 * @end: Range end time.
 * @cb: Callback function.
 * @cb_data: Closure data for the callback function.
 * @tz_cb: Callback for retrieving timezones.
 * @tz_cb_data: Closure data for the timezone callback.
 * @default_timezone: Default timezone to use when a timezone cannot be
 * found.
 *
 * Calls the given callback function for each occurrence of the event that
 * intersects the range between the given @start and @end times (the end time is
 * not included). Note that the occurrences may start before the given start
 * time.
 *
 * If the callback routine returns FALSE the occurrence generation stops.
 *
 * Both start and end can be -1, in which case we start at the events first
 * instance and continue until it ends, or forever if it has no enddate.
 *
 * The tz_cb is used to resolve references to timezones. It is passed a TZID
 * and should return the icaltimezone* corresponding to that TZID. We need to
 * do this as we access timezones in different ways on the client & server.
 *
 * The default_timezone argument is used for DTSTART or DTEND properties that
 * are DATE values or do not have a TZID (i.e. floating times).
 */
void
e_cal_recur_generate_instances (ECalComponent		*comp,
			      time_t			 start,
			      time_t			 end,
			      ECalRecurInstanceFn	 cb,
			      gpointer                   cb_data,
			      ECalRecurResolveTimezoneFn  tz_cb,
			      gpointer			 tz_cb_data,
			      icaltimezone		*default_timezone)
{
#if 0
	g_print ("In e_cal_recur_generate_instances comp: %p\n", comp);
	g_print ("  start: %li - %s", start, ctime (&start));
	g_print ("  end  : %li - %s", end, ctime (&end));
#endif
	e_cal_recur_generate_instances_of_rule (comp, NULL, start, end,
						cb, cb_data, tz_cb, tz_cb_data,
						default_timezone);
}


/*
 * Calls the given callback function for each occurrence of the given
 * recurrence rule between the given start and end times. If the rule is NULL
 * it uses all the rules from the component.
 *
 * If the callback routine returns FALSE the occurrence generation stops.
 *
 * The use of the specific rule is for determining the end of a rule when
 * COUNT is set. The callback will count instances and store the enddate
 * when COUNT is reached.
 *
 * Both start and end can be -1, in which case we start at the events first
 * instance and continue until it ends, or forever if it has no enddate.
 */
static void
e_cal_recur_generate_instances_of_rule (ECalComponent	 *comp,
					icalproperty	 *prop,
					time_t		  start,
					time_t		  end,
					ECalRecurInstanceFn  cb,
					gpointer            cb_data,
					ECalRecurResolveTimezoneFn  tz_cb,
					gpointer	            tz_cb_data,
					icaltimezone	 *default_timezone)
{
	ECalComponentDateTime dtstart, dtend;
	time_t dtstart_time, dtend_time;
	GSList *rrules = NULL, *rdates = NULL, elem;
	GSList *exrules = NULL, *exdates = NULL;
	CalObjTime interval_start, interval_end, event_start, event_end;
	CalObjTime chunk_start, chunk_end;
	gint days, seconds, year;
	gboolean single_rule, convert_end_date = FALSE;
	icaltimezone *start_zone = NULL, *end_zone = NULL;

	g_return_if_fail (comp != NULL);
	g_return_if_fail (cb != NULL);
	g_return_if_fail (tz_cb != NULL);
	g_return_if_fail (start >= -1);
	g_return_if_fail (end >= -1);

	/* Get dtstart, dtend, recurrences, and exceptions. Note that
	   cal_component_get_dtend() will convert a DURATION property to a
	   DTEND so we don't need to worry about that. */

	e_cal_component_get_dtstart (comp, &dtstart);
	e_cal_component_get_dtend (comp, &dtend);

	if (!dtstart.value) {
		g_message ("e_cal_recur_generate_instances_of_rule(): bogus "
			   "component, does not have DTSTART.  Skipping...");
		goto out;
	}

	/* For DATE-TIME values with a TZID, we use the supplied callback to
	   resolve the TZID. For DATE values and DATE-TIME values without a
	   TZID (i.e. floating times) we use the default timezone. */
	if (dtstart.tzid && !dtstart.value->is_date) {
		start_zone = (*tz_cb) (dtstart.tzid, tz_cb_data);
		if (!start_zone)
			start_zone = default_timezone;
	} else {
		start_zone = default_timezone;

		/* Flag that we need to convert the saved ENDDATE property
		   to the default timezone. */
		convert_end_date = TRUE;
	}

	dtstart_time = icaltime_as_timet_with_zone (*dtstart.value,
						    start_zone);
	if (start == -1)
		start = dtstart_time;

	if (dtend.value) {
		/* If both DTSTART and DTEND are DATE values, and they are the
		   same day, we add 1 day to DTEND. This means that most
		   events created with the old Evolution behavior will still
		   work OK. I'm not sure what Outlook does in this case. */
		if (dtstart.value->is_date && dtend.value->is_date) {
			if (icaltime_compare_date_only (*dtstart.value,
							*dtend.value) == 0) {
				icaltime_adjust (dtend.value, 1, 0, 0, 0);
			}
		}
	} else {
		/* If there is no DTEND, then if DTSTART is a DATE-TIME value
		   we use the same time (so we have a single point in time).
		   If DTSTART is a DATE value we add 1 day. */
		dtend.value = g_new (struct icaltimetype, 1);
		*dtend.value = *dtstart.value;

		if (dtstart.value->is_date) {
			icaltime_adjust (dtend.value, 1, 0, 0, 0);
		}
	}

	if (dtend.tzid && !dtend.value->is_date) {
		end_zone = (*tz_cb) (dtend.tzid, tz_cb_data);
		if (!end_zone)
			end_zone = default_timezone;
	} else {
		end_zone = default_timezone;
	}

	/* We don't do this any more, since Outlook assumes that the DTEND
	   date is not included. */
#if 0
	/* If DTEND is a DATE value, we add 1 day to it so that it includes
	   the entire day. */
	if (dtend.value->is_date) {
		dtend.value->hour = 0;
		dtend.value->minute = 0;
		dtend.value->second = 0;
		icaltime_adjust (dtend.value, 1, 0, 0, 0);
	}
#endif
	dtend_time = icaltime_as_timet_with_zone (*dtend.value, end_zone);

	/* If there is no recurrence, just call the callback if the event
	   intersects the given interval. */
	if (!(e_cal_component_has_recurrences (comp)
	      || e_cal_component_has_exceptions (comp))) {
		if (e_cal_component_get_vtype (comp) == E_CAL_COMPONENT_JOURNAL) {
			icaltimetype start_t = icaltime_from_timet_with_zone (start, FALSE, default_timezone);
			icaltimetype end_t = icaltime_from_timet_with_zone (end, FALSE, default_timezone);
		
			if ((icaltime_compare_date_only (*dtstart.value, start_t) >= 0) && ((icaltime_compare_date_only (*dtstart.value, end_t) < 0)))
				(* cb) (comp, dtstart_time, dtend_time, cb_data);
		} else if  ((end == -1 || dtstart_time < end) && dtend_time > start) {
			(* cb) (comp, dtstart_time, dtend_time, cb_data);
		}

		goto out;
	}

	/* If a specific recurrence rule is being used, set up a simple list,
	   else get the recurrence rules from the component. */
	if (prop) {
		single_rule = TRUE;

		elem.data = prop;
		elem.next = NULL;
		rrules = &elem;
	} else if (e_cal_component_is_instance (comp)) {
		single_rule = FALSE;
	} else {
		single_rule = FALSE;

		/* Make sure all the enddates for the rules are set. */
		e_cal_recur_ensure_end_dates (comp, FALSE, tz_cb, tz_cb_data);

		e_cal_component_get_rrule_property_list (comp, &rrules);
		e_cal_component_get_rdate_list (comp, &rdates);
		e_cal_component_get_exrule_property_list (comp, &exrules);
		e_cal_component_get_exdate_list (comp, &exdates);
	}

	/* Convert the interval start & end to CalObjTime. Note that if end
	   is -1 interval_end won't be set, so don't use it!
	   Also note that we use end - 1 since we want the interval to be
	   inclusive as it makes the code simpler. We do all calculation
	   in the timezone of the DTSTART. */
	cal_object_time_from_time (&interval_start, start, start_zone);
	if (end != -1)
		cal_object_time_from_time (&interval_end, end - 1, start_zone);

	cal_object_time_from_time (&event_start, dtstart_time, start_zone);
	cal_object_time_from_time (&event_end, dtend_time, start_zone);
	
	/* Calculate the duration of the event, which we use for all
	   occurrences. We can't just subtract start from end since that may
	   be affected by daylight-saving time. So we want a value of days
	   + seconds. */
	cal_object_compute_duration (&event_start, &event_end,
				     &days, &seconds);

	/* Take off the duration from interval_start, so we get occurrences
	   that start just before the start time but overlap it. But only do
	   that if the interval is after the event's start time. */
	if (start > dtstart_time) {
		cal_obj_time_add_days (&interval_start, -days);
		cal_obj_time_add_seconds (&interval_start, -seconds);
	}

	/* Expand the recurrence for each year between start & end, or until
	   the callback returns 0 if end is 0. We do a year at a time to
	   give the callback function a chance to break out of the loop, and
	   so we don't get into problems with infinite recurrences. Since we
	   have to work on complete sets of occurrences, if there is a yearly
	   frequency it wouldn't make sense to break it into smaller chunks,
	   since we would then be calculating the same sets several times.
	   Though this does mean that we sometimes do a lot more work than
	   is necessary, e.g. if COUNT is set to something quite low. */
	for (year = interval_start.year;
	     (end == -1 || year <= interval_end.year) && year <= MAX_YEAR;
	     year++) {
		chunk_start = interval_start;
		chunk_start.year = year;
		if (end != -1)
			chunk_end = interval_end;
		chunk_end.year = year;

		if (year != interval_start.year) {
			chunk_start.month  = 0;
			chunk_start.day    = 1;
			chunk_start.hour   = 0;
			chunk_start.minute = 0;
			chunk_start.second = 0;
		}
		if (end == -1 || year != interval_end.year) {
			chunk_end.month  = 11;
			chunk_end.day    = 31;
			chunk_end.hour   = 23;
			chunk_end.minute = 59;
			chunk_end.second = 61;
			chunk_end.flags  = FALSE;
		}

		if (!generate_instances_for_chunk (comp, dtstart_time,
						   start_zone,
						   rrules, rdates,
						   exrules, exdates,
						   single_rule,
						   &event_start,
						   start,
						   &chunk_start, &chunk_end,
						   days, seconds,
						   convert_end_date,
						   cb, cb_data))
			break;
	}

	if (!prop) {
		e_cal_component_free_period_list (rdates);
		e_cal_component_free_exdate_list (exdates);
	}

 out:
	e_cal_component_free_datetime (&dtstart);
	e_cal_component_free_datetime (&dtend);
}

/* Builds a list of GINT_TO_POINTER() elements out of a short array from a
 * struct icalrecurrencetype.
 */
static GList *
array_to_list (short *array, int max_elements)
{
	GList *l;
	int i;

	l = NULL;

	for (i = 0; i < max_elements && array[i] != ICAL_RECURRENCE_ARRAY_MAX; i++)
		l = g_list_prepend (l, GINT_TO_POINTER ((int) (array[i])));
	return g_list_reverse (l);
}

/**
 * e_cal_recur_from_icalproperty:
 * @prop: An RRULE or EXRULE #icalproperty.
 * @exception: TRUE if this is an EXRULE rather than an RRULE.
 * @zone: The DTSTART timezone, used for converting the UNTIL property if it
 * is given as a DATE value.
 * @convert_end_date: TRUE if the saved end date needs to be converted to the
 * given @zone timezone. This is needed if the DTSTART is a DATE or floating
 * time.
 * 
 * Converts an #icalproperty to a #ECalRecurrence.  This should be
 * freed using the e_cal_recur_free() function.
 * 
 * Return value: #ECalRecurrence structure.
 **/
static ECalRecurrence *
e_cal_recur_from_icalproperty (icalproperty *prop, gboolean exception,
			     icaltimezone *zone, gboolean convert_end_date)
{
	struct icalrecurrencetype ir;
	ECalRecurrence *r;
	gint max_elements, i;
	GList *elem;

	g_return_val_if_fail (prop != NULL, NULL);

	r = g_new (ECalRecurrence, 1);

	if (exception)
		ir = icalproperty_get_exrule (prop);
	else
		ir = icalproperty_get_rrule (prop);

	r->freq = ir.freq;
	r->interval = ir.interval;

	if (ir.count != 0) {
		/* If COUNT is set, we use the pre-calculated enddate.
		   Note that this can be 0 if the RULE doesn't actually
		   generate COUNT instances. */
		r->enddate = e_cal_recur_get_rule_end_date (prop, convert_end_date ? zone : NULL);
	} else {
		if (icaltime_is_null_time (ir.until)) {
			/* If neither COUNT or UNTIL is set, the event
			   recurs forever. */
			r->enddate = 0;
		} else if (ir.until.is_date) {
			/* If UNTIL is a DATE, we stop at the end of
			   the day, in local time (with the DTSTART timezone).
			   Note that UNTIL is inclusive so we stop before
			   midnight. */
			ir.until.hour = 23;
			ir.until.minute = 59;
			ir.until.second = 59;
			ir.until.is_date = FALSE;

			r->enddate = icaltime_as_timet_with_zone (ir.until,
								  zone);
#if 0
			g_print ("  until: %li - %s", r->enddate, ctime (&r->enddate));
#endif

		} else {
			/* If UNTIL is a DATE-TIME, it must be in UTC. */
			icaltimezone *utc_zone;
			utc_zone = icaltimezone_get_utc_timezone ();
			r->enddate = icaltime_as_timet_with_zone (ir.until,
								  utc_zone);
		}
	}

	r->week_start_day = e_cal_recur_ical_weekday_to_weekday (ir.week_start);

	r->bymonth = array_to_list (ir.by_month,
				    sizeof (ir.by_month) / sizeof (ir.by_month[0]));
	for (elem = r->bymonth; elem; elem = elem->next) {
		/* We need to convert from 1-12 to 0-11, i.e. subtract 1. */
		int month = GPOINTER_TO_INT (elem->data) - 1;
		elem->data = GINT_TO_POINTER (month);
	}

	r->byweekno = array_to_list (ir.by_week_no,
				     sizeof (ir.by_week_no) / sizeof (ir.by_week_no[0]));

	r->byyearday = array_to_list (ir.by_year_day,
				      sizeof (ir.by_year_day) / sizeof (ir.by_year_day[0]));

	r->bymonthday = array_to_list (ir.by_month_day,
				       sizeof (ir.by_month_day) / sizeof (ir.by_month_day[0]));

	/* FIXME: libical only supports 8 values, out of possible 107 * 7. */
	r->byday = NULL;
	max_elements = sizeof (ir.by_day) / sizeof (ir.by_day[0]);
	for (i = 0; i < max_elements && ir.by_day[i] != ICAL_RECURRENCE_ARRAY_MAX; i++) {
		enum icalrecurrencetype_weekday day;
		gint weeknum, weekday;

		day = icalrecurrencetype_day_day_of_week (ir.by_day[i]);
		weeknum = icalrecurrencetype_day_position (ir.by_day[i]);

		weekday = e_cal_recur_ical_weekday_to_weekday (day);

		r->byday = g_list_prepend (r->byday,
					   GINT_TO_POINTER (weeknum));
		r->byday = g_list_prepend (r->byday,
					   GINT_TO_POINTER (weekday));
	}

	r->byhour = array_to_list (ir.by_hour,
				   sizeof (ir.by_hour) / sizeof (ir.by_hour[0]));

	r->byminute = array_to_list (ir.by_minute,
				     sizeof (ir.by_minute) / sizeof (ir.by_minute[0]));

	r->bysecond = array_to_list (ir.by_second,
				     sizeof (ir.by_second) / sizeof (ir.by_second[0]));

	r->bysetpos = array_to_list (ir.by_set_pos,
				     sizeof (ir.by_set_pos) / sizeof (ir.by_set_pos[0]));

	return r;
}


static gint
e_cal_recur_ical_weekday_to_weekday	(enum icalrecurrencetype_weekday day)
{
	gint weekday;

	switch (day) {
	case ICAL_NO_WEEKDAY:		/* Monday is the default in RFC2445. */
	case ICAL_MONDAY_WEEKDAY:
		weekday = 0;
		break;
	case ICAL_TUESDAY_WEEKDAY:
		weekday = 1;
		break;
	case ICAL_WEDNESDAY_WEEKDAY:
		weekday = 2;
		break;
	case ICAL_THURSDAY_WEEKDAY:
		weekday = 3;
		break;
	case ICAL_FRIDAY_WEEKDAY:
		weekday = 4;
		break;
	case ICAL_SATURDAY_WEEKDAY:
		weekday = 5;
		break;
	case ICAL_SUNDAY_WEEKDAY:
		weekday = 6;
		break;
	default:
		g_warning ("e_cal_recur_ical_weekday_to_weekday(): Unknown week day %d",
			   day);
		weekday = 0;
	}

	return weekday;
}


/**
 * e_cal_recur_free:
 * @r: A #ECalRecurrence structure.
 * 
 * Frees a #ECalRecurrence structure.
 **/
static void
e_cal_recur_free (ECalRecurrence *r)
{
	g_return_if_fail (r != NULL);

	g_list_free (r->bymonth);
	g_list_free (r->byweekno);
	g_list_free (r->byyearday);
	g_list_free (r->bymonthday);
	g_list_free (r->byday);
	g_list_free (r->byhour);
	g_list_free (r->byminute);
	g_list_free (r->bysecond);
	g_list_free (r->bysetpos);

	g_free (r);
}

/* Generates one year's worth of recurrence instances.  Returns TRUE if all the
 * callback invocations returned TRUE, or FALSE when any one of them returns
 * FALSE, i.e. meaning that the instance generation should be stopped.
 *
 * This should only output instances whose start time is between chunk_start
 * and chunk_end (inclusive), or we may generate duplicates when we do the next
 * chunk. (This applies mainly to weekly recurrences, since weeks can span 2
 * years.)
 *
 * It should also only output instances that are on or after the event's
 * DTSTART property and that intersect the required interval, between
 * interval_start and interval_end.
 */
static gboolean
generate_instances_for_chunk (ECalComponent	*comp,
			      time_t             comp_dtstart,
			      icaltimezone	*zone,
			      GSList		*rrules,
			      GSList		*rdates,
			      GSList		*exrules,
			      GSList		*exdates,
			      gboolean		 single_rule,
			      CalObjTime	*event_start,
			      time_t		 interval_start,
			      CalObjTime	*chunk_start,
			      CalObjTime	*chunk_end,
			      gint		 duration_days,
			      gint		 duration_seconds,
			      gboolean		 convert_end_date,
			      ECalRecurInstanceFn cb,
			      gpointer           cb_data)
{
	GArray *occs, *ex_occs, *tmp_occs, *rdate_periods;
	CalObjTime cotime, *occ;
	GSList *elem;
	gint i;
	time_t start_time, end_time;
	struct icaltimetype start_tt, end_tt;
	gboolean cb_status = TRUE, rule_finished, finished = TRUE;

#if 0
	g_print ("In generate_instances_for_chunk rrules: %p\n"
		 "  %i/%i/%i %02i:%02i:%02i - %i/%i/%i %02i:%02i:%02i\n",
		 rrules,
		 chunk_start->day, chunk_start->month + 1,
		 chunk_start->year, chunk_start->hour,
		 chunk_start->minute, chunk_start->second,
		 chunk_end->day, chunk_end->month + 1,
		 chunk_end->year, chunk_end->hour,
		 chunk_end->minute, chunk_end->second);
#endif

	occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
	ex_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
	rdate_periods = g_array_new (FALSE, FALSE,
				     sizeof (CalObjRecurrenceDate));

	/* The original DTSTART property is included in the occurrence set,
	   but not if we are just generating occurrences for a single rule. */
	if (!single_rule) {
		/* We add it if it is in this chunk. If it is after this chunk
		   we set finished to FALSE, since we know we aren't finished
		   yet. */
		if (cal_obj_time_compare_func (event_start, chunk_end) >= 0)
			finished = FALSE;
		else if (cal_obj_time_compare_func (event_start, chunk_start) >= 0)
			g_array_append_vals (occs, event_start, 1);
	}
	
	/* Expand each of the recurrence rules. */
	for (elem = rrules; elem; elem = elem->next) {
		icalproperty *prop;
		ECalRecurrence *r;

		prop = elem->data;
		r = e_cal_recur_from_icalproperty (prop, FALSE, zone,
						 convert_end_date);

		tmp_occs = cal_obj_expand_recurrence (event_start, zone, r,
						      chunk_start,
						      chunk_end,
						      &rule_finished);
		e_cal_recur_free (r);

		/* If any of the rules return FALSE for finished, we know we
		   have to carry on so we set finished to FALSE. */
		if (!rule_finished)
			finished = FALSE;

		g_array_append_vals (occs, tmp_occs->data, tmp_occs->len);
		g_array_free (tmp_occs, TRUE);
	}

	/* Add on specific RDATE occurrence dates. If they have an end time
	   or duration set, flag them as RDATEs, and store a pointer to the
	   period in the rdate_periods array. Otherwise we can just treat them
	   as normal occurrences. */
	for (elem = rdates; elem; elem = elem->next) {
		ECalComponentPeriod *p;
		CalObjRecurrenceDate rdate;

		p = elem->data;

		/* FIXME: We currently assume RDATEs are in the same timezone
		   as DTSTART. We should get the RDATE timezone and convert
		   to the DTSTART timezone first. */
		cotime.year     = p->start.year;
		cotime.month    = p->start.month - 1;
		cotime.day      = p->start.day;
		cotime.hour     = p->start.hour;
		cotime.minute   = p->start.minute;
		cotime.second   = p->start.second;
		cotime.flags    = FALSE;

		/* If the rdate is after the current chunk we set finished
		   to FALSE, and we skip it. */
		if (cal_obj_time_compare_func (&cotime, chunk_end) >= 0) {
			finished = FALSE;
			continue;
		}

		/* Check if the end date or duration is set. If it is we need
		   to store it so we can get it later. (libical seems to set
		   second to -1 to denote an unset time. See icalvalue.c)
		   FIXME. */
		if (p->type != E_CAL_COMPONENT_PERIOD_DATETIME
		    || p->u.end.second != -1) {
			cotime.flags = TRUE;

			rdate.start = cotime;
			rdate.period = p;
			g_array_append_val (rdate_periods, rdate);
		}

		g_array_append_val (occs, cotime);
	}

	/* Expand each of the exception rules. */
	for (elem = exrules; elem; elem = elem->next) {
		icalproperty *prop;
		ECalRecurrence *r;

		prop = elem->data;
		r = e_cal_recur_from_icalproperty (prop, FALSE, zone,
						 convert_end_date);

		tmp_occs = cal_obj_expand_recurrence (event_start, zone, r,
						      chunk_start,
						      chunk_end,
						      &rule_finished);
		e_cal_recur_free (r);

		g_array_append_vals (ex_occs, tmp_occs->data, tmp_occs->len);
		g_array_free (tmp_occs, TRUE);
	}

	/* Add on specific exception dates. */
	for (elem = exdates; elem; elem = elem->next) {
		ECalComponentDateTime *cdt;

		cdt = elem->data;

		/* FIXME: We currently assume EXDATEs are in the same timezone
		   as DTSTART. We should get the EXDATE timezone and convert
		   to the DTSTART timezone first. */
		cotime.year     = cdt->value->year;
		cotime.month    = cdt->value->month - 1;
		cotime.day      = cdt->value->day;

		/* If the EXDATE has a DATE value, set the time to the start
		   of the day and set flags to TRUE so we know to skip all
		   occurrences on that date. */
		if (cdt->value->is_date) {
			cotime.hour     = 0;
			cotime.minute   = 0;
			cotime.second   = 0;
			cotime.flags    = TRUE;
		} else {
			cotime.hour     = cdt->value->hour;
			cotime.minute   = cdt->value->minute;
			cotime.second   = cdt->value->second;
			cotime.flags    = FALSE;
		}

		g_array_append_val (ex_occs, cotime);
	}


	/* Sort all the arrays. */
	cal_obj_sort_occurrences (occs);
	cal_obj_sort_occurrences (ex_occs);

	qsort (rdate_periods->data, rdate_periods->len,
	       sizeof (CalObjRecurrenceDate), cal_obj_time_compare_func);

	/* Create the final array, by removing the exceptions from the
	   occurrences, and removing any duplicates. */
	cal_obj_remove_exceptions (occs, ex_occs);

	/* Call the callback for each occurrence. If it returns 0 we break
	   out of the loop. */
	for (i = 0; i < occs->len; i++) {
		/* Convert each CalObjTime into a start & end time_t, and
		   check it is within the bounds of the event & interval. */
		occ = &g_array_index (occs, CalObjTime, i);
#if 0
		g_print ("Checking occurrence: %s\n",
			 cal_obj_time_to_string (occ));
#endif
		start_tt = icaltime_null_time ();
		start_tt.year   = occ->year;
		start_tt.month  = occ->month + 1;
		start_tt.day    = occ->day;
		start_tt.hour   = occ->hour;
		start_tt.minute = occ->minute;
		start_tt.second = occ->second;
		start_time = icaltime_as_timet_with_zone (start_tt, zone);

		if (start_time == -1) {
			g_warning ("time_t out of range");
			finished = TRUE;
			break;
		}

		/* Check to ensure that the start time is at or after the
		   event's DTSTART time, and that it is inside the chunk that
		   we are currently working on. (Note that the chunk_end time
		   is never after the interval end time, so this also tests
		   that we don't go past the end of the required interval). */
		if (start_time < comp_dtstart
		    || cal_obj_time_compare_func (occ, chunk_start) < 0
		    || cal_obj_time_compare_func (occ, chunk_end) > 0) {
#if 0
			g_print ("  start time invalid\n");
#endif
			continue;
		}

		if (occ->flags) {
			/* If it is an RDATE, we see if the end date or
			   duration was set. If not, we use the same duration
			   as the original occurrence. */
			if (!cal_object_get_rdate_end (occ, rdate_periods)) {
				cal_obj_time_add_days (occ, duration_days);
				cal_obj_time_add_seconds (occ,
							  duration_seconds);
			}
		} else {
			cal_obj_time_add_days (occ, duration_days);
			cal_obj_time_add_seconds (occ, duration_seconds);
		}

		end_tt = icaltime_null_time ();
		end_tt.year   = occ->year;
		end_tt.month  = occ->month + 1;
		end_tt.day    = occ->day;
		end_tt.hour   = occ->hour;
		end_tt.minute = occ->minute;
		end_tt.second = occ->second;
		end_time = icaltime_as_timet_with_zone (end_tt, zone);

		if (end_time == -1) {
			g_warning ("time_t out of range");
			finished = TRUE;
			break;
		}

		/* Check that the end time is after the interval start, so we
		   know that it intersects the required interval. */
		if (end_time <= interval_start) {
#if 0
			g_print ("  end time invalid\n");
#endif
			continue;
		}

		cb_status = (*cb) (comp, start_time, end_time, cb_data);
		if (!cb_status)
			break;
	}

	g_array_free (occs, TRUE);
	g_array_free (ex_occs, TRUE);
	g_array_free (rdate_periods, TRUE);

	/* We return TRUE (i.e. carry on) only if the callback has always
	   returned TRUE and we know that we have more occurrences to generate
	   (i.e. finished is FALSE). */
	return cb_status && !finished;
}


/* This looks up the occurrence time in the sorted rdate_periods array, and
   tries to compute the end time of the occurrence. If no end time or duration
   is set it returns FALSE and the default duration will be used. */
static gboolean
cal_object_get_rdate_end	(CalObjTime	*occ,
				 GArray		*rdate_periods)
{
	CalObjRecurrenceDate *rdate = NULL;
	ECalComponentPeriod *p;
	gint lower, upper, middle, cmp = 0;

	lower = 0;
	upper = rdate_periods->len;

	while (lower < upper) {
		middle = (lower + upper) >> 1;
	  
		rdate = &g_array_index (rdate_periods, CalObjRecurrenceDate,
					middle);

		cmp = cal_obj_time_compare_func (occ, &rdate->start);
	  
		if (cmp == 0)
			break;
		else if (cmp < 0)
			upper = middle;
		else
			lower = middle + 1;
	}

	/* This should never happen. */
	if (cmp == 0) {
		g_warning ("Recurrence date not found");
		return FALSE;
	}

	p = rdate->period;
	if (p->type == E_CAL_COMPONENT_PERIOD_DATETIME) {
		/* FIXME: We currently assume RDATEs are in the same timezone
		   as DTSTART. We should get the RDATE timezone and convert
		   to the DTSTART timezone first. */
		occ->year     = p->u.end.year;
		occ->month    = p->u.end.month - 1;
		occ->day      = p->u.end.day;
		occ->hour     = p->u.end.hour;
		occ->minute   = p->u.end.minute;
		occ->second   = p->u.end.second;
		occ->flags    = FALSE;
	} else {
		cal_obj_time_add_days (occ, p->u.duration.weeks * 7
				       + p->u.duration.days);
		cal_obj_time_add_hours (occ, p->u.duration.hours);
		cal_obj_time_add_minutes (occ, p->u.duration.minutes);
		cal_obj_time_add_seconds (occ, p->u.duration.seconds);
	}

	return TRUE;
}


static void
cal_object_compute_duration (CalObjTime *start,
			     CalObjTime *end,
			     gint	*days,
			     gint	*seconds)
{
	GDate start_date, end_date;
	gint start_seconds, end_seconds;

	g_date_clear (&start_date, 1);
	g_date_clear (&end_date, 1);
	g_date_set_dmy (&start_date, start->day, start->month + 1,
			start->year);
	g_date_set_dmy (&end_date, end->day, end->month + 1,
			end->year);

	*days = g_date_get_julian (&end_date) - g_date_get_julian (&start_date);
	start_seconds = start->hour * 3600 + start->minute * 60
		+ start->second;
	end_seconds = end->hour * 3600 + end->minute * 60 + end->second;

	*seconds = end_seconds - start_seconds;
	if (*seconds < 0) {
		*days = *days - 1;
		*seconds += 24 * 60 * 60;
	}
}


/* Returns an unsorted GArray of CalObjTime's resulting from expanding the
   given recurrence rule within the given interval. Note that it doesn't
   clip the generated occurrences to the interval, i.e. if the interval
   starts part way through the year this function still returns all the
   occurrences for the year. Clipping is done later.
   The finished flag is set to FALSE if there are more occurrences to generate
   after the given interval.*/
static GArray*
cal_obj_expand_recurrence		(CalObjTime	  *event_start,
					 icaltimezone	  *zone,
					 ECalRecurrence	  *recur,
					 CalObjTime	  *interval_start,
					 CalObjTime	  *interval_end,
					 gboolean	  *finished)
{
	ECalRecurVTable *vtable;
	CalObjTime *event_end = NULL, event_end_cotime;
	RecurData recur_data;
	CalObjTime occ, *cotime;
	GArray *all_occs, *occs;
	gint len;

	/* This is the resulting array of CalObjTime elements. */
	all_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));

	*finished = TRUE;

	vtable = cal_obj_get_vtable (recur->freq);
	if (!vtable)
		return all_occs;

	/* Calculate some useful data such as some fast lookup tables. */
	cal_obj_initialize_recur_data (&recur_data, recur, event_start);

	/* Compute the event_end, if the recur's enddate is set. */
	if (recur->enddate > 0) {
		cal_object_time_from_time (&event_end_cotime,
					   recur->enddate, zone);
		event_end = &event_end_cotime;

		/* If the enddate is before the requested interval return. */
		if (cal_obj_time_compare_func (event_end, interval_start) < 0)
			return all_occs;
	}

	/* Set finished to FALSE if we know there will be more occurrences to
	   do after this interval. */
	if (!interval_end || !event_end
	    || cal_obj_time_compare_func (event_end, interval_end) > 0)
		*finished = FALSE;

	/* 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_data,
					    interval_start, interval_end,
					    &occ))
		return all_occs;

	/* Loop until the event ends or we go past the end of the required
	   interval. */
	for (;;) {
		/* Generate the set of occurrences for this period. */
		switch (recur->freq) {
		case ICAL_YEARLY_RECURRENCE:
			occs = cal_obj_generate_set_yearly (&recur_data,
							    vtable, &occ);
			break;
		case ICAL_MONTHLY_RECURRENCE:
			occs = cal_obj_generate_set_monthly (&recur_data,
							     vtable, &occ);
			break;
		default:
			occs = cal_obj_generate_set_default (&recur_data,
							     vtable, &occ);
			break;
		}

		/* Sort the occurrences and remove duplicates. */
		cal_obj_sort_occurrences (occs);
		cal_obj_remove_duplicates_and_invalid_dates (occs);

		/* Apply the BYSETPOS property. */
		occs = cal_obj_bysetpos_filter (recur, occs);

		/* Remove any occs after event_end. */
		len = occs->len - 1;
		if (event_end) {
			while (len >= 0) {
				cotime = &g_array_index (occs, CalObjTime,
							 len);
				if (cal_obj_time_compare_func (cotime,
							       event_end) <= 0)
					break;
				len--;
			}
		}

		/* Add the occurrences onto the main array. */
		if (len >= 0)
			g_array_append_vals (all_occs, occs->data, len + 1);

 		g_array_free (occs, TRUE);

		/* Skip to the next period, or exit the loop if finished. */
		if ((*vtable->find_next_position) (&occ, event_end,
						   &recur_data, interval_end))
			break;
	}

	return all_occs;
}


static GArray*
cal_obj_generate_set_yearly	(RecurData *recur_data,
				 ECalRecurVTable *vtable,
				 CalObjTime *occ)
{
	ECalRecurrence *recur = recur_data->recur;
	GArray *occs_arrays[4], *occs, *occs2;
	gint num_occs_arrays = 0, i;

	/* This is a bit complicated, since the iCalendar spec says that
	   several BYxxx modifiers can be used simultaneously. So we have to
	   be quite careful when determining the days of the occurrences.
	   The BYHOUR, BYMINUTE & BYSECOND modifiers are no problem at all.

	   The modifiers we have to worry about are: BYMONTH, BYWEEKNO,
	   BYYEARDAY, BYMONTHDAY & BYDAY. We can't do these sequentially
	   since each filter will mess up the results of the previous one.
	   But they aren't all completely independant, e.g. BYMONTHDAY and
	   BYDAY are related to BYMONTH, and BYDAY is related to BYWEEKNO.

	   BYDAY & BYMONTHDAY can also be applied independently, which makes
	   it worse. So we assume that if BYMONTH or BYWEEKNO is used, then
	   the BYDAY modifier applies to those, else it is applied
	   independantly.

	   We expand the occurrences in parallel into the occs_arrays[] array,
	   and then merge them all into one GArray before expanding BYHOUR,
	   BYMINUTE & BYSECOND. */

	if (recur->bymonth) {
		occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
		g_array_append_vals (occs, occ, 1);

		occs = (*vtable->bymonth_filter) (recur_data, occs);

		/* If BYMONTHDAY & BYDAY are both set we need to expand them
		   in parallel and add the results. */
		if (recur->bymonthday && recur->byday) {
			/* Copy the occs array. */
			occs2 = g_array_new (FALSE, FALSE,
					     sizeof (CalObjTime));
			g_array_append_vals (occs2, occs->data, occs->len);

			occs = (*vtable->bymonthday_filter) (recur_data, occs);
			/* Note that we explicitly call the monthly version
			   of the BYDAY expansion filter. */
			occs2 = cal_obj_byday_expand_monthly (recur_data,
							      occs2);

			/* Add the 2 resulting arrays together. */
			g_array_append_vals (occs, occs2->data, occs2->len);
			g_array_free (occs2, TRUE);
		} else {
			occs = (*vtable->bymonthday_filter) (recur_data, occs);
			/* Note that we explicitly call the monthly version
			   of the BYDAY expansion filter. */
			occs = cal_obj_byday_expand_monthly (recur_data, occs);
		}

		occs_arrays[num_occs_arrays++] = occs;
	}

	if (recur->byweekno) {
		occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
		g_array_append_vals (occs, occ, 1);

		occs = (*vtable->byweekno_filter) (recur_data, occs);
		/* Note that we explicitly call the weekly version of the
		   BYDAY expansion filter. */
		occs = cal_obj_byday_expand_weekly (recur_data, occs);

		occs_arrays[num_occs_arrays++] = occs;
	}

	if (recur->byyearday) {
		occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
		g_array_append_vals (occs, occ, 1);

		occs = (*vtable->byyearday_filter) (recur_data, occs);

		occs_arrays[num_occs_arrays++] = occs;
	}

	/* If BYMONTHDAY is set, and BYMONTH is not set, we need to
	   expand BYMONTHDAY independantly. */
	if (recur->bymonthday && !recur->bymonth) {
		occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
		g_array_append_vals (occs, occ, 1);

		occs = (*vtable->bymonthday_filter) (recur_data, occs);

		occs_arrays[num_occs_arrays++] = occs;
	}

	/* If BYDAY is set, and BYMONTH and BYWEEKNO are not set, we need to
	   expand BYDAY independantly. */
	if (recur->byday && !recur->bymonth && !recur->byweekno) {
		occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
		g_array_append_vals (occs, occ, 1);

		occs = (*vtable->byday_filter) (recur_data, occs);

		occs_arrays[num_occs_arrays++] = occs;
	}

	/* Add all the arrays together. If no filters were used we just
	   create an array with one element. */
	if (num_occs_arrays > 0) {
		occs = occs_arrays[0];
		for (i = 1; i < num_occs_arrays; i++) {
			occs2 = occs_arrays[i];
			g_array_append_vals (occs, occs2->data, occs2->len);
			g_array_free (occs2, TRUE);
		}
	} else {
		occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
		g_array_append_vals (occs, occ, 1);
	}

	/* Now expand BYHOUR, BYMINUTE & BYSECOND. */
	occs = (*vtable->byhour_filter) (recur_data, occs);
	occs = (*vtable->byminute_filter) (recur_data, occs);
	occs = (*vtable->bysecond_filter) (recur_data, occs);

	return occs;
}


static GArray*
cal_obj_generate_set_monthly	(RecurData *recur_data,
				 ECalRecurVTable *vtable,
				 CalObjTime *occ)
{
	GArray *occs, *occs2;

	/* We start with just the one time in each set. */
	occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
	g_array_append_vals (occs, occ, 1);

	occs = (*vtable->bymonth_filter) (recur_data, occs);

	/* We need to combine the output of BYMONTHDAY & BYDAY, by doing them
	   in parallel rather than sequentially. If we did them sequentially
	   then we would lose the occurrences generated by BYMONTHDAY, and
	   instead have repetitions of the occurrences from BYDAY. */
	if (recur_data->recur->bymonthday && recur_data->recur->byday) {
		occs2 = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
		g_array_append_vals (occs2, occs->data, occs->len);

		occs = (*vtable->bymonthday_filter) (recur_data, occs);
		occs2 = (*vtable->byday_filter) (recur_data, occs2);

		g_array_append_vals (occs, occs2->data, occs2->len);
		g_array_free (occs2, TRUE);
	} else {
		occs = (*vtable->bymonthday_filter) (recur_data, occs);
		occs = (*vtable->byday_filter) (recur_data, occs);
	}

	occs = (*vtable->byhour_filter) (recur_data, occs);
	occs = (*vtable->byminute_filter) (recur_data, occs);
	occs = (*vtable->bysecond_filter) (recur_data, occs);

	return occs;
}


static GArray*
cal_obj_generate_set_default	(RecurData *recur_data,
				 ECalRecurVTable *vtable,
				 CalObjTime *occ)
{
	GArray *occs;

#if 0
	g_print ("Generating set for %i/%i/%i %02i:%02i:%02i\n",
		 occ->day, occ->month + 1, occ->year, occ->hour, occ->minute,
		 occ->second);
#endif

	/* We start with just the one time in the set. */
	occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));
	g_array_append_vals (occs, occ, 1);

	occs = (*vtable->bymonth_filter) (recur_data, occs);
	if (vtable->byweekno_filter)
		occs = (*vtable->byweekno_filter) (recur_data, occs);
	if (vtable->byyearday_filter)
		occs = (*vtable->byyearday_filter) (recur_data, occs);
	if (vtable->bymonthday_filter)
		occs = (*vtable->bymonthday_filter) (recur_data, occs);
	occs = (*vtable->byday_filter) (recur_data, occs);

	occs = (*vtable->byhour_filter) (recur_data, occs);
	occs = (*vtable->byminute_filter) (recur_data, occs);
	occs = (*vtable->bysecond_filter) (recur_data, occs);

	return occs;
}



/* Returns the function table corresponding to the recurrence frequency. */
static ECalRecurVTable* cal_obj_get_vtable (icalrecurrencetype_frequency recur_type)
{
	ECalRecurVTable* vtable;

	switch (recur_type) {
	case ICAL_YEARLY_RECURRENCE:
		vtable = &cal_obj_yearly_vtable;
		break;
	case ICAL_MONTHLY_RECURRENCE:
		vtable = &cal_obj_monthly_vtable;
		break;
	case ICAL_WEEKLY_RECURRENCE:
		vtable = &cal_obj_weekly_vtable;
		break;
	case ICAL_DAILY_RECURRENCE:
		vtable = &cal_obj_daily_vtable;
		break;
	case ICAL_HOURLY_RECURRENCE:
		vtable = &cal_obj_hourly_vtable;
		break;
	case ICAL_MINUTELY_RECURRENCE:
		vtable = &cal_obj_minutely_vtable;
		break;
	case ICAL_SECONDLY_RECURRENCE:
		vtable = &cal_obj_secondly_vtable;
		break;
	default:
		g_warning ("Unknown recurrence frequency");
		vtable = NULL;
	}

	return vtable;
}


/* This creates a number of fast lookup tables used when filtering with the
   modifier properties BYMONTH, BYYEARDAY etc. */
static void
cal_obj_initialize_recur_data (RecurData  *recur_data,
			       ECalRecurrence *recur,
			       CalObjTime *event_start)
{
	GList *elem;
	gint month, yearday, monthday, weekday, week_num, hour, minute, second;

	/* Clear the entire RecurData. */
	memset (recur_data, 0, sizeof (RecurData));

	recur_data->recur = recur;

	/* Set the weekday, used for the WEEKLY frequency and the BYWEEKNO
	   modifier. */
	recur_data->weekday_offset = cal_obj_time_weekday_offset (event_start,
								  recur);

	/* Create an array of months from bymonths for fast lookup. */
	elem = recur->bymonth;
	while (elem) {
		month = GPOINTER_TO_INT (elem->data);
		recur_data->months[month] = 1;
		elem = elem->next;
	}

	/* Create an array of yeardays from byyearday for fast lookup.
	   We create a second array to handle the negative values. The first
	   element there corresponds to the last day of the year. */
	elem = recur->byyearday;
	while (elem) {
		yearday = GPOINTER_TO_INT (elem->data);
		if (yearday >= 0)
			recur_data->yeardays[yearday] = 1;
		else
			recur_data->neg_yeardays[-yearday] = 1;
		elem = elem->next;
	}

	/* Create an array of monthdays from bymonthday for fast lookup.
	   We create a second array to handle the negative values. The first
	   element there corresponds to the last day of the month. */
	elem = recur->bymonthday;
	while (elem) {
		monthday = GPOINTER_TO_INT (elem->data);
		if (monthday >= 0)
			recur_data->monthdays[monthday] = 1;
		else
			recur_data->neg_monthdays[-monthday] = 1;
		elem = elem->next;
	}

	/* Create an array of weekdays from byday for fast lookup. */
	elem = recur->byday;
	while (elem) {
		weekday = GPOINTER_TO_INT (elem->data);
		elem = elem->next;
		/* The week number is not used when filtering. */
		week_num = GPOINTER_TO_INT (elem->data);
		elem = elem->next;

		recur_data->weekdays[weekday] = 1;
	}

	/* Create an array of hours from byhour for fast lookup. */
	elem = recur->byhour;
	while (elem) {
		hour = GPOINTER_TO_INT (elem->data);
		recur_data->hours[hour] = 1;
		elem = elem->next;
	}

	/* Create an array of minutes from byminutes for fast lookup. */
	elem = recur->byminute;
	while (elem) {
		minute = GPOINTER_TO_INT (elem->data);
		recur_data->minutes[minute] = 1;
		elem = elem->next;
	}

	/* Create an array of seconds from byseconds for fast lookup. */
	elem = recur->bysecond;
	while (elem) {
		second = GPOINTER_TO_INT (elem->data);
		recur_data->seconds[second] = 1;
		elem = elem->next;
	}
}


static void
cal_obj_sort_occurrences (GArray *occs)
{
	qsort (occs->data, occs->len, sizeof (CalObjTime),
	       cal_obj_time_compare_func);
}


static void
cal_obj_remove_duplicates_and_invalid_dates (GArray *occs)
{
	static const int days_in_month[12] = {
		31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
	};

	CalObjTime *occ, *prev_occ = NULL;
	gint len, i, j = 0, year, month, days;
	gboolean keep_occ;

	len = occs->len;
	for (i = 0; i < len; i++) {
		occ = &g_array_index (occs, CalObjTime, i);
		keep_occ = TRUE;

		if (prev_occ && cal_obj_time_compare_func (occ,
							   prev_occ) == 0)
			keep_occ = FALSE;

		year = occ->year;
		month = occ->month;
		days = days_in_month[occ->month];
		/* If it is february and a leap year, add a day. */
		if (month == 1 && (year % 4 == 0
				   && (year % 100 != 0
				       || year % 400 == 0)))
			days++;

		if (occ->day > days) {
			/* move occurrence to the last day of the month */
			occ->day = days;
		}

		if (keep_occ) {
			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);
}


/* Removes the exceptions from the ex_occs array from the occurrences in the
   occs array, and removes any duplicates. Both arrays are sorted. */
static void
cal_obj_remove_exceptions (GArray *occs,
			   GArray *ex_occs)
{
	CalObjTime *occ, *prev_occ = NULL, *ex_occ = NULL, *last_occ_kept;
	gint i, j = 0, cmp, ex_index, occs_len, ex_occs_len;
	gboolean keep_occ, current_time_is_exception = FALSE;

	if (occs->len == 0)
		return;

	ex_index = 0;
	occs_len = occs->len;
	ex_occs_len = ex_occs->len;

	if (ex_occs_len > 0)
		ex_occ = &g_array_index (ex_occs, CalObjTime, ex_index);

	for (i = 0; i < occs_len; i++) {
		occ = &g_array_index (occs, CalObjTime, i);
		keep_occ = TRUE;

		/* If the occurrence is a duplicate of the previous one, skip
		   it. */
		if (prev_occ
		    && cal_obj_time_compare_func (occ, prev_occ) == 0) {
			keep_occ = FALSE;

			/* If this occurrence is an RDATE with an end or
			   duration set, and the previous occurrence in the
			   array was kept, set the RDATE flag of the last one,
			   so we still use the end date or duration. */
			if (occ->flags && !current_time_is_exception) {
				last_occ_kept = &g_array_index (occs,
								CalObjTime,
								j - 1);
				last_occ_kept->flags = TRUE;
			}
		} else {
			/* We've found a new occurrence time. Reset the flag
			   to indicate that it hasn't been found in the
			   exceptions array (yet). */
			current_time_is_exception = FALSE;

			if (ex_occ) {
				/* Step through the exceptions until we come
				   to one that matches or follows this
				   occurrence. */
				while (ex_occ) {
					/* If the exception is an EXDATE with
					   a DATE value, we only have to
					   compare the date. */
					if (ex_occ->flags)
						cmp = cal_obj_date_only_compare_func (ex_occ, occ);
					else
						cmp = cal_obj_time_compare_func (ex_occ, occ);

					if (cmp > 0)
						break;

					/* Move to the next exception, or set
					   ex_occ to NULL when we reach the
					   end of array. */
					ex_index++;
					if (ex_index < ex_occs_len)
						ex_occ = &g_array_index (ex_occs, CalObjTime, ex_index);
					else
						ex_occ = NULL;

					/* If the exception did match this
					   occurrence we remove it, and set the
					   flag to indicate that the current
					   time is an exception. */
					if (cmp == 0) {
						current_time_is_exception = TRUE;
						keep_occ = FALSE;
						break;
					}
				}
			}
		}

		if (keep_occ) {
			/* We are keeping this occurrence, so we move it to
			   the next free space, unless its position hasn't
			   changed (i.e. all previous occurrences were also
			   kept). */
			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 (ECalRecurrence *recur,
			 GArray	    *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	GList *elem;
	gint len, pos;

	/* If BYSETPOS has not been specified, or the array is empty, just
	   return the array. */
	elem = recur->bysetpos;
	if (!elem || occs->len == 0)
		return occs;

	new_occs = g_array_new (FALSE, FALSE, sizeof (CalObjTime));

	/* Iterate over the indices given in bysetpos, adding the corresponding
	   element from occs to new_occs. */
	len = occs->len;
	while (elem) {
		pos = GPOINTER_TO_INT (elem->data);

		/* Negative values count back from the end of the array. */
		if (pos < 0)
			pos += len;
		/* Positive values need to be decremented since the array is
		   0-based. */
		else
			pos--;

		if (pos >= 0 && pos < len) {
			occ = &g_array_index (occs, CalObjTime, pos);
			g_array_append_vals (new_occs, occ, 1);
		}
		elem = elem->next;
	}

	g_array_free (occs, TRUE);

	return new_occs;
}




/* Finds the first year from the event_start, counting in multiples of the
   recurrence interval, that intersects the given interval. It returns TRUE
   if there is no intersection. */
static gboolean
cal_obj_yearly_find_start_position (CalObjTime *event_start,
				    CalObjTime *event_end,
				    RecurData  *recur_data,
				    CalObjTime *interval_start,
				    CalObjTime *interval_end,
				    CalObjTime *cotime)
{
	*cotime = *event_start;

	/* Move on to the next interval, if the event starts before the
	   given interval. */
	if (cotime->year < interval_start->year) {
		gint years = interval_start->year - cotime->year
			+ recur_data->recur->interval - 1;
		years -= years % recur_data->recur->interval;
		/* NOTE: The day may now be invalid, e.g. 29th Feb. */
		cotime->year += years;
	}

	if ((event_end && cotime->year > event_end->year)
	    || (interval_end && cotime->year > interval_end->year))
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_yearly_find_next_position (CalObjTime *cotime,
				   CalObjTime *event_end,
				   RecurData  *recur_data,
				   CalObjTime *interval_end)
{
	/* NOTE: The day may now be invalid, e.g. 29th Feb. */
	cotime->year += recur_data->recur->interval;

	if ((event_end && cotime->year > event_end->year)
	    || (interval_end && cotime->year > interval_end->year))
		return TRUE;

	return FALSE;
}



static gboolean
cal_obj_monthly_find_start_position (CalObjTime *event_start,
				     CalObjTime *event_end,
				     RecurData  *recur_data,
				     CalObjTime *interval_start,
				     CalObjTime *interval_end,
				     CalObjTime *cotime)
{
	*cotime = *event_start;

	/* Move on to the next interval, if the event starts before the
	   given interval. */
	if (cal_obj_time_compare (cotime, interval_start, CALOBJ_MONTH) < 0) {
		gint months = (interval_start->year - cotime->year) * 12
			+ interval_start->month - cotime->month
			+ recur_data->recur->interval - 1;
		months -= months % recur_data->recur->interval;
		/* NOTE: The day may now be invalid, e.g. 31st Sep. */
		cal_obj_time_add_months (cotime, months);
	}

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_MONTH) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_MONTH) > 0)
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_monthly_find_next_position (CalObjTime *cotime,
				    CalObjTime *event_end,
				    RecurData  *recur_data,
				    CalObjTime *interval_end)
{
	/* NOTE: The day may now be invalid, e.g. 31st Sep. */
	cal_obj_time_add_months (cotime, recur_data->recur->interval);

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_MONTH) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_MONTH) > 0)
		return TRUE;

	return FALSE;
}



static gboolean
cal_obj_weekly_find_start_position (CalObjTime *event_start,
				    CalObjTime *event_end,
				    RecurData  *recur_data,
				    CalObjTime *interval_start,
				    CalObjTime *interval_end,
				    CalObjTime *cotime)
{
	GDate event_start_date, interval_start_date;
	guint32 event_start_julian, interval_start_julian;
	gint interval_start_weekday_offset;
	CalObjTime week_start;

	if (event_end && cal_obj_time_compare (event_end, interval_start,
					       CALOBJ_DAY) < 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (event_start, interval_end,
						  CALOBJ_DAY) > 0)
		return TRUE;

	*cotime = *event_start;

	/* Convert the event start and interval start to GDates, so we can
	   easily find the number of days between them. */
	g_date_clear (&event_start_date, 1);
	g_date_set_dmy (&event_start_date, event_start->day,
			event_start->month + 1, event_start->year);
	g_date_clear (&interval_start_date, 1);
	g_date_set_dmy (&interval_start_date, interval_start->day,
			interval_start->month + 1, interval_start->year);

	/* Calculate the start of the weeks corresponding to the event start
	   and interval start. */
	event_start_julian = g_date_get_julian (&event_start_date);
	event_start_julian -= recur_data->weekday_offset;

	interval_start_julian = g_date_get_julian (&interval_start_date);
	interval_start_weekday_offset = cal_obj_time_weekday_offset (interval_start, recur_data->recur);
	interval_start_julian -= interval_start_weekday_offset;

	/* We want to find the first full week using the recurrence interval
	   that intersects the given interval dates. */
	if (event_start_julian < interval_start_julian) {
		gint weeks = (interval_start_julian - event_start_julian) / 7;
		weeks += recur_data->recur->interval - 1;
		weeks -= weeks % recur_data->recur->interval;
		cal_obj_time_add_days (cotime, weeks * 7);
	}

	week_start = *cotime;
	cal_obj_time_add_days (&week_start, -recur_data->weekday_offset);

	if (event_end && cal_obj_time_compare (&week_start, event_end,
					       CALOBJ_DAY) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (&week_start, interval_end,
						  CALOBJ_DAY) > 0)
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_weekly_find_next_position (CalObjTime *cotime,
				   CalObjTime *event_end,
				   RecurData  *recur_data,
				   CalObjTime *interval_end)
{
	CalObjTime week_start;

	cal_obj_time_add_days (cotime, recur_data->recur->interval * 7);

	/* Return TRUE if the start of this week is after the event finishes
	   or is after the end of the required interval. */
	week_start = *cotime;
	cal_obj_time_add_days (&week_start, -recur_data->weekday_offset);

#ifdef CAL_OBJ_DEBUG
	g_print ("Next  day: %s\n", cal_obj_time_to_string (cotime));
	g_print ("Week Start: %s\n", cal_obj_time_to_string (&week_start));
#endif

	if (event_end && cal_obj_time_compare (&week_start, event_end,
					       CALOBJ_DAY) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (&week_start, interval_end,
						  CALOBJ_DAY) > 0) {
#ifdef CAL_OBJ_DEBUG
		g_print ("Interval end reached: %s\n",
			 cal_obj_time_to_string (interval_end));
#endif
		return TRUE;
	}

	return FALSE;
}


static gboolean
cal_obj_daily_find_start_position  (CalObjTime *event_start,
				    CalObjTime *event_end,
				    RecurData  *recur_data,
				    CalObjTime *interval_start,
				    CalObjTime *interval_end,
				    CalObjTime *cotime)
{
	GDate event_start_date, interval_start_date;
	guint32 event_start_julian, interval_start_julian, days;

	if (interval_end && cal_obj_time_compare (event_start, interval_end,
						  CALOBJ_DAY) > 0)
		return TRUE;
	if (event_end && cal_obj_time_compare (event_end, interval_start,
					       CALOBJ_DAY) < 0)
		return TRUE;

	*cotime = *event_start;

	/* Convert the event start and interval start to GDates, so we can
	   easily find the number of days between them. */
	g_date_clear (&event_start_date, 1);
	g_date_set_dmy (&event_start_date, event_start->day,
			event_start->month + 1, event_start->year);
	g_date_clear (&interval_start_date, 1);
	g_date_set_dmy (&interval_start_date, interval_start->day,
			interval_start->month + 1, interval_start->year);

	event_start_julian = g_date_get_julian (&event_start_date);
	interval_start_julian = g_date_get_julian (&interval_start_date);

	if (event_start_julian < interval_start_julian) {
		days = interval_start_julian - event_start_julian
			+ recur_data->recur->interval - 1;
		days -= days % recur_data->recur->interval;
		cal_obj_time_add_days (cotime, days);
	}

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_DAY) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_DAY) > 0)
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_daily_find_next_position  (CalObjTime *cotime,
				   CalObjTime *event_end,
				   RecurData  *recur_data,
				   CalObjTime *interval_end)
{
	cal_obj_time_add_days (cotime, recur_data->recur->interval);

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_DAY) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_DAY) > 0)
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_hourly_find_start_position (CalObjTime *event_start,
				    CalObjTime *event_end,
				    RecurData  *recur_data,
				    CalObjTime *interval_start,
				    CalObjTime *interval_end,
				    CalObjTime *cotime)
{
	GDate event_start_date, interval_start_date;
	guint32 event_start_julian, interval_start_julian, hours;

	if (interval_end && cal_obj_time_compare (event_start, interval_end,
						  CALOBJ_HOUR) > 0)
		return TRUE;
	if (event_end && cal_obj_time_compare (event_end, interval_start,
					       CALOBJ_HOUR) < 0)
		return TRUE;

	*cotime = *event_start;

	if (cal_obj_time_compare (event_start, interval_start,
				  CALOBJ_HOUR) < 0) {
		/* Convert the event start and interval start to GDates, so we
		   can easily find the number of days between them. */
		g_date_clear (&event_start_date, 1);
		g_date_set_dmy (&event_start_date, event_start->day,
				event_start->month + 1, event_start->year);
		g_date_clear (&interval_start_date, 1);
		g_date_set_dmy (&interval_start_date, interval_start->day,
				interval_start->month + 1,
				interval_start->year);

		event_start_julian = g_date_get_julian (&event_start_date);
		interval_start_julian = g_date_get_julian (&interval_start_date);

		hours = (interval_start_julian - event_start_julian) * 24;
		hours += interval_start->hour - event_start->hour;
		hours += recur_data->recur->interval - 1;
		hours -= hours % recur_data->recur->interval;
		cal_obj_time_add_hours (cotime, hours);
	}

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_HOUR) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_HOUR) > 0)
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_hourly_find_next_position (CalObjTime *cotime,
				   CalObjTime *event_end,
				   RecurData  *recur_data,
				   CalObjTime *interval_end)
{
	cal_obj_time_add_hours (cotime, recur_data->recur->interval);

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_HOUR) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_HOUR) > 0)
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_minutely_find_start_position (CalObjTime *event_start,
				      CalObjTime *event_end,
				      RecurData  *recur_data,
				      CalObjTime *interval_start,
				      CalObjTime *interval_end,
				      CalObjTime *cotime)
{
	GDate event_start_date, interval_start_date;
	guint32 event_start_julian, interval_start_julian, minutes;

	if (interval_end && cal_obj_time_compare (event_start, interval_end,
						  CALOBJ_MINUTE) > 0)
		return TRUE;
	if (event_end && cal_obj_time_compare (event_end, interval_start,
					       CALOBJ_MINUTE) < 0)
		return TRUE;

	*cotime = *event_start;

	if (cal_obj_time_compare (event_start, interval_start,
				  CALOBJ_MINUTE) < 0) {
		/* Convert the event start and interval start to GDates, so we
		   can easily find the number of days between them. */
		g_date_clear (&event_start_date, 1);
		g_date_set_dmy (&event_start_date, event_start->day,
				event_start->month + 1, event_start->year);
		g_date_clear (&interval_start_date, 1);
		g_date_set_dmy (&interval_start_date, interval_start->day,
				interval_start->month + 1,
				interval_start->year);

		event_start_julian = g_date_get_julian (&event_start_date);
		interval_start_julian = g_date_get_julian (&interval_start_date);

		minutes = (interval_start_julian - event_start_julian)
			* 24 * 60;
		minutes += (interval_start->hour - event_start->hour) * 24;
		minutes += interval_start->minute - event_start->minute;
		minutes += recur_data->recur->interval - 1;
		minutes -= minutes % recur_data->recur->interval;
		cal_obj_time_add_minutes (cotime, minutes);
	}

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_MINUTE) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_MINUTE) > 0)
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_minutely_find_next_position (CalObjTime *cotime,
				     CalObjTime *event_end,
				     RecurData  *recur_data,
				     CalObjTime *interval_end)
{
	cal_obj_time_add_minutes (cotime, recur_data->recur->interval);

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_MINUTE) > 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_MINUTE) > 0)
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_secondly_find_start_position (CalObjTime *event_start,
				      CalObjTime *event_end,
				      RecurData  *recur_data,
				      CalObjTime *interval_start,
				      CalObjTime *interval_end,
				      CalObjTime *cotime)
{
	GDate event_start_date, interval_start_date;
	guint32 event_start_julian, interval_start_julian, seconds;

	if (interval_end && cal_obj_time_compare (event_start, interval_end,
						  CALOBJ_SECOND) > 0)
		return TRUE;
	if (event_end && cal_obj_time_compare (event_end, interval_start,
					       CALOBJ_SECOND) < 0)
		return TRUE;

	*cotime = *event_start;

	if (cal_obj_time_compare (event_start, interval_start,
				  CALOBJ_SECOND) < 0) {
		/* Convert the event start and interval start to GDates, so we
		   can easily find the number of days between them. */
		g_date_clear (&event_start_date, 1);
		g_date_set_dmy (&event_start_date, event_start->day,
				event_start->month + 1, event_start->year);
		g_date_clear (&interval_start_date, 1);
		g_date_set_dmy (&interval_start_date, interval_start->day,
				interval_start->month + 1,
				interval_start->year);

		event_start_julian = g_date_get_julian (&event_start_date);
		interval_start_julian = g_date_get_julian (&interval_start_date);

		seconds = (interval_start_julian - event_start_julian)
			* 24 * 60 * 60;
		seconds += (interval_start->hour - event_start->hour)
			* 24 * 60;
		seconds += (interval_start->minute - event_start->minute) * 60;
		seconds += interval_start->second - event_start->second;
		seconds += recur_data->recur->interval - 1;
		seconds -= seconds % recur_data->recur->interval;
		cal_obj_time_add_seconds (cotime, seconds);
	}

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_SECOND) >= 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_SECOND) >= 0)
		return TRUE;

	return FALSE;
}


static gboolean
cal_obj_secondly_find_next_position (CalObjTime *cotime,
				     CalObjTime *event_end,
				     RecurData  *recur_data,
				     CalObjTime *interval_end)
{
	cal_obj_time_add_seconds (cotime, recur_data->recur->interval);

	if (event_end && cal_obj_time_compare (cotime, event_end,
					       CALOBJ_SECOND) >= 0)
		return TRUE;
	if (interval_end && cal_obj_time_compare (cotime, interval_end,
						  CALOBJ_SECOND) >= 0)
		return TRUE;

	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		(RecurData  *recur_data,
				 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_data->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_data->recur->bymonth;
		while (elem) {
			/* NOTE: The day may now be invalid, e.g. 31st Feb. */
			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		(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	gint len, i;

	/* If BYMONTH has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->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);
		if (recur_data->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		(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ, year_start_cotime, year_end_cotime, cotime;
	GList *elem;
	gint len, i, weekno;

	/* If BYWEEKNO has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->recur->byweekno || 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);

		/* Find the day that would correspond to week 1 (note that
		   week 1 is the first week starting from the specified week
		   start day that has 4 days in the new year). */
		year_start_cotime = *occ;
		cal_obj_time_find_first_week (&year_start_cotime,
					      recur_data);

		/* Find the day that would correspond to week 1 of the next
		   year, which we use for -ve week numbers. */
		year_end_cotime = *occ;
		year_end_cotime.year++;
		cal_obj_time_find_first_week (&year_end_cotime,
					      recur_data);

		/* Now iterate over the week numbers in byweekno, generating a
		   new occurrence for each one. */
		elem = recur_data->recur->byweekno;
		while (elem) {
			weekno = GPOINTER_TO_INT (elem->data);
			if (weekno > 0) {
				cotime = year_start_cotime;
				cal_obj_time_add_days (&cotime,
						       (weekno - 1) * 7);
			} else {
				cotime = year_end_cotime;
				cal_obj_time_add_days (&cotime, weekno * 7);
			}

			/* Skip occurrences if they fall outside the year. */
			if (cotime.year == occ->year)
				g_array_append_val (new_occs, cotime);
			elem = elem->next;
		}
	}

	g_array_free (occs, TRUE);

	return new_occs;
}


#if 0
/* This isn't used at present. */
static GArray*
cal_obj_byweekno_filter		(RecurData  *recur_data,
				 GArray     *occs)
{

	return occs;
}
#endif


static GArray*
cal_obj_byyearday_expand	(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ, year_start_cotime, year_end_cotime, cotime;
	GList *elem;
	gint len, i, dayno;

	/* If BYYEARDAY has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->recur->byyearday || 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);

		/* Find the day that would correspond to day 1. */
		year_start_cotime = *occ;
		year_start_cotime.month = 0;
		year_start_cotime.day = 1;

		/* Find the day that would correspond to day 1 of the next
		   year, which we use for -ve day numbers. */
		year_end_cotime = *occ;
		year_end_cotime.year++;
		year_end_cotime.month = 0;
		year_end_cotime.day = 1;

		/* Now iterate over the day numbers in byyearday, generating a
		   new occurrence for each one. */
		elem = recur_data->recur->byyearday;
		while (elem) {
			dayno = GPOINTER_TO_INT (elem->data);
			if (dayno > 0) {
				cotime = year_start_cotime;
				cal_obj_time_add_days (&cotime, dayno - 1);
			} else {
				cotime = year_end_cotime;
				cal_obj_time_add_days (&cotime, dayno);
			}

			/* Skip occurrences if they fall outside the year. */
			if (cotime.year == occ->year)
				g_array_append_val (new_occs, cotime);
			elem = elem->next;
		}
	}

	g_array_free (occs, TRUE);

	return new_occs;
}


/* Note: occs must not contain invalid dates, e.g. 31st September. */
static GArray*
cal_obj_byyearday_filter	(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	gint yearday, len, i, days_in_year;

	/* If BYYEARDAY has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->recur->byyearday || 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);
		yearday = cal_obj_time_day_of_year (occ);
		if (recur_data->yeardays[yearday]) {
			g_array_append_vals (new_occs, occ, 1);
		} else {
			days_in_year = g_date_is_leap_year (occ->year)
				? 366 : 365;
			if (recur_data->neg_yeardays[days_in_year + 1
						    - yearday])
				g_array_append_vals (new_occs, occ, 1);
		}
	}

	g_array_free (occs, TRUE);

	return new_occs;
}



static GArray*
cal_obj_bymonthday_expand	(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ, month_start_cotime, month_end_cotime, cotime;
	GList *elem;
	gint len, i, dayno;

	/* If BYMONTHDAY has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->recur->bymonthday || 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);

		/* Find the day that would correspond to day 1. */
		month_start_cotime = *occ;
		month_start_cotime.day = 1;

		/* Find the day that would correspond to day 1 of the next
		   month, which we use for -ve day numbers. */
		month_end_cotime = *occ;
		month_end_cotime.month++;
		month_end_cotime.day = 1;

		/* Now iterate over the day numbers in bymonthday, generating a
		   new occurrence for each one. */
		elem = recur_data->recur->bymonthday;
		while (elem) {
			dayno = GPOINTER_TO_INT (elem->data);
			if (dayno > 0) {
				cotime = month_start_cotime;
				cal_obj_time_add_days (&cotime, dayno - 1);
			} else {
				cotime = month_end_cotime;
				cal_obj_time_add_days (&cotime, dayno);
			}
			if (cotime.month == occ->month) {
				g_array_append_val (new_occs, cotime);
			} else {
				/* set to last day in month */
				cotime.month = occ->month;
				cotime.day = time_days_in_month (occ->year, occ->month);
				g_array_append_val (new_occs, cotime);
			}
				
			elem = elem->next;
		}
	}

	g_array_free (occs, TRUE);

	return new_occs;
}


static GArray*
cal_obj_bymonthday_filter	(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	gint len, i, days_in_month;

	/* If BYMONTHDAY has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->recur->bymonthday || 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);
		if (recur_data->monthdays[occ->day]) {
			g_array_append_vals (new_occs, occ, 1);
		} else {
			days_in_month = time_days_in_month (occ->year,
							    occ->month);
			if (recur_data->neg_monthdays[days_in_month + 1
						     - occ->day])
				g_array_append_vals (new_occs, occ, 1);
		}
	}

	g_array_free (occs, TRUE);

	return new_occs;
}



static GArray*
cal_obj_byday_expand_yearly	(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	GList *elem;
	gint len, i, weekday, week_num;
	gint first_weekday, last_weekday, offset;
	guint16 year;

	/* If BYDAY has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->recur->byday || 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_data->recur->byday;
		while (elem) {
			weekday = GPOINTER_TO_INT (elem->data);
			elem = elem->next;
			week_num = GPOINTER_TO_INT (elem->data);
			elem = elem->next;

			year = occ->year;
			if (week_num == 0) {
				/* Expand to every Mon/Tue/etc. in the year. */
				occ->month = 0;
				occ->day = 1;
				first_weekday = cal_obj_time_weekday (occ);
				offset = (weekday + 7 - first_weekday) % 7;
				cal_obj_time_add_days (occ, offset);

				while (occ->year == year) {
					g_array_append_vals (new_occs, occ, 1);
					cal_obj_time_add_days (occ, 7);
				}

			} else if (week_num > 0) {
				/* Add the nth Mon/Tue/etc. in the year. */
				occ->month = 0;
				occ->day = 1;
				first_weekday = cal_obj_time_weekday (occ);
				offset = (weekday + 7 - first_weekday) % 7;
				offset += (week_num - 1) * 7;
				cal_obj_time_add_days (occ, offset);
				if (occ->year == year)
					g_array_append_vals (new_occs, occ, 1);

			} else {
				/* Add the -nth Mon/Tue/etc. in the year. */
				occ->month = 11;
				occ->day = 31;
				last_weekday = cal_obj_time_weekday (occ);
				offset = (last_weekday + 7 - weekday) % 7;
				offset += (week_num - 1) * 7;
				cal_obj_time_add_days (occ, -offset);
				if (occ->year == year)
					g_array_append_vals (new_occs, occ, 1);
			}

			/* Reset the year, as we may have gone past the end. */
			occ->year = year;
		}
	}

	g_array_free (occs, TRUE);

	return new_occs;
}


static GArray*
cal_obj_byday_expand_monthly	(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	GList *elem;
	gint len, i, weekday, week_num;
	gint first_weekday, last_weekday, offset;
	guint16 year;
	guint8 month;

	/* If BYDAY has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->recur->byday || 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_data->recur->byday;
		while (elem) {
			weekday = GPOINTER_TO_INT (elem->data);
			elem = elem->next;
			week_num = GPOINTER_TO_INT (elem->data);
			elem = elem->next;

			year = occ->year;
			month = occ->month;
			if (week_num == 0) {
				/* Expand to every Mon/Tue/etc. in the month.*/
				occ->day = 1;
				first_weekday = cal_obj_time_weekday (occ);
				offset = (weekday + 7 - first_weekday) % 7;
				cal_obj_time_add_days (occ, offset);

				while (occ->year == year
				       && occ->month == month) {
					g_array_append_vals (new_occs, occ, 1);
					cal_obj_time_add_days (occ, 7);
				}

			} else if (week_num > 0) {
				/* Add the nth Mon/Tue/etc. in the month. */
				occ->day = 1;
				first_weekday = cal_obj_time_weekday (occ);
				offset = (weekday + 7 - first_weekday) % 7;
				offset += (week_num - 1) * 7;
				cal_obj_time_add_days (occ, offset);
				if (occ->year == year && occ->month == month)
					g_array_append_vals (new_occs, occ, 1);

			} else {
				/* Add the -nth Mon/Tue/etc. in the month. */
				occ->day = time_days_in_month (occ->year,
							       occ->month);
				last_weekday = cal_obj_time_weekday (occ);

				/* This calculates the number of days to step
				   backwards from the last day of the month
				   to the weekday we want. */
				offset = (last_weekday + 7 - weekday) % 7;

				/* This adds on the weeks. */
				offset += (-week_num - 1) * 7;

				cal_obj_time_add_days (occ, -offset);
				if (occ->year == year && occ->month == month)
					g_array_append_vals (new_occs, occ, 1);
			}

			/* Reset the year & month, as we may have gone past
			   the end. */
			occ->year = year;
			occ->month = month;
		}
	}

	g_array_free (occs, TRUE);

	return new_occs;
}


/* Note: occs must not contain invalid dates, e.g. 31st September. */
static GArray*
cal_obj_byday_expand_weekly	(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	GList *elem;
	gint len, i, weekday, week_num;
	gint weekday_offset, new_weekday_offset;

	/* If BYDAY has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->recur->byday || 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_data->recur->byday;
		while (elem) {
			weekday = GPOINTER_TO_INT (elem->data);
			elem = elem->next;

			/* FIXME: Currently we just ignore this, but maybe we
			   should skip all elements where week_num != 0.
			   The spec isn't clear about this. */
			week_num = GPOINTER_TO_INT (elem->data);
			elem = elem->next;

			weekday_offset = cal_obj_time_weekday_offset (occ, recur_data->recur);
			new_weekday_offset = (weekday + 7 - recur_data->recur->week_start_day) % 7;
			cal_obj_time_add_days (occ, new_weekday_offset - weekday_offset);
			g_array_append_vals (new_occs, occ, 1);
		}
	}

	g_array_free (occs, TRUE);

	return new_occs;
}


/* Note: occs must not contain invalid dates, e.g. 31st September. */
static GArray*
cal_obj_byday_filter		(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	gint len, i, weekday;

	/* If BYDAY has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->recur->byday || 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);
		weekday = cal_obj_time_weekday (occ);

		/* See if the weekday on its own is set. */
		if (recur_data->weekdays[weekday])
			g_array_append_vals (new_occs, occ, 1);
	}

	g_array_free (occs, TRUE);

	return new_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		(RecurData  *recur_data,
				 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_data->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_data->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		(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	gint len, i;

	/* If BYHOUR has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->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);
		if (recur_data->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		(RecurData  *recur_data,
				 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_data->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_data->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		(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	gint len, i;

	/* If BYMINUTE has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->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);
		if (recur_data->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		(RecurData  *recur_data,
				 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_data->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_data->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		(RecurData  *recur_data,
				 GArray     *occs)
{
	GArray *new_occs;
	CalObjTime *occ;
	gint len, i;

	/* If BYSECOND has not been specified, or the array is empty, just
	   return the array. */
	if (!recur_data->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);
		if (recur_data->seconds[occ->second])
			g_array_append_vals (new_occs, occ, 1);
	}

	g_array_free (occs, TRUE);

	return new_occs;
}





/* Adds a positive or negative number of months to the given CalObjTime,
   updating the year appropriately so we end up with a valid month.
   Note that the day may be invalid, e.g. 30th Feb. */
static void
cal_obj_time_add_months		(CalObjTime *cotime,
				 gint	     months)
{
	guint month, years;

	/* We use a guint to avoid overflow on the guint8. */
	month = cotime->month + months;
	cotime->month = month % 12;
	if (month > 0) {
		cotime->year += month / 12;
	} else {
		years = month / 12;
		if (cotime->month != 0) {
			cotime->month += 12;
			years -= 1;
		}
		cotime->year += years;
	}
}


/* Adds a positive or negative number of days to the given CalObjTime,
   updating the month and year appropriately so we end up with a valid day. */
static void
cal_obj_time_add_days		(CalObjTime *cotime,
				 gint	     days)
{
	gint day, days_in_month;

	/* We use a guint to avoid overflow on the guint8. */
	day = cotime->day;
	day += days;

	if (days >= 0) {
		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;
	} else {
		while (day <= 0) {
			if (cotime->month == 0) {
				cotime->year--;
				cotime->month = 11;
			} else {
				cotime->month--;
			}

			days_in_month = time_days_in_month (cotime->year,
							    cotime->month);
			day += days_in_month;
		}

		cotime->day = (guint8) day;
	}
}


/* Adds a positive or negative number of hours to the given CalObjTime,
   updating the day, month & year appropriately so we end up with a valid
   time. */
static void
cal_obj_time_add_hours		(CalObjTime *cotime,
				 gint	     hours)
{
	gint hour, days;

	/* We use a gint to avoid overflow on the guint8. */
	hour = cotime->hour + hours;
	cotime->hour = hour % 24;
	if (hour >= 0) {
		if (hour >= 24)
			cal_obj_time_add_days (cotime, hour / 24);
	} else {
		days = hour / 24;
		if (cotime->hour != 0) {
			cotime->hour += 24;
			days -= 1;
		}
		cal_obj_time_add_days (cotime, days);
	}
}


/* Adds a positive or negative number of minutes to the given CalObjTime,
   updating the rest of the CalObjTime appropriately. */
static void
cal_obj_time_add_minutes	(CalObjTime *cotime,
				 gint	     minutes)
{
	gint minute, hours;

	/* We use a gint to avoid overflow on the guint8. */
	minute = cotime->minute + minutes;
	cotime->minute = minute % 60;
	if (minute >= 0) {
		if (minute >= 60)
			cal_obj_time_add_hours (cotime, minute / 60);
	} else {
		hours = minute / 60;
		if (cotime->minute != 0) {
			cotime->minute += 60;
			hours -= 1;
		}
		cal_obj_time_add_hours (cotime, hours);
	}
}


/* Adds a positive or negative number of seconds to the given CalObjTime,
   updating the rest of the CalObjTime appropriately. */
static void
cal_obj_time_add_seconds	(CalObjTime *cotime,
				 gint	     seconds)
{
	gint second, minutes;

	/* We use a gint to avoid overflow on the guint8. */
	second = cotime->second + seconds;
	cotime->second = second % 60;
	if (second >= 0) {
		if (second >= 60)
			cal_obj_time_add_minutes (cotime, second / 60);
	} else {
		minutes = second / 60;
		if (cotime->second != 0) {
			cotime->second += 60;
			minutes -= 1;
		}
		cal_obj_time_add_minutes (cotime, minutes);
	}
}


/* Compares 2 CalObjTimes. Returns -1 if the cotime1 is before cotime2, 0 if
   they are the same, or 1 if cotime1 is after cotime2. The comparison type
   specifies which parts of the times we are interested in, e.g. if CALOBJ_DAY
   is used we only want to know if the days are different. */
static gint
cal_obj_time_compare		(CalObjTime *cotime1,
				 CalObjTime *cotime2,
				 CalObjTimeComparison type)
{
	if (cotime1->year < cotime2->year)
		return -1;
	if (cotime1->year > cotime2->year)
		return 1;

	if (type == CALOBJ_YEAR)
		return 0;

	if (cotime1->month < cotime2->month)
		return -1;
	if (cotime1->month > cotime2->month)
		return 1;

	if (type == CALOBJ_MONTH)
		return 0;

	if (cotime1->day < cotime2->day)
		return -1;
	if (cotime1->day > cotime2->day)
		return 1;

	if (type == CALOBJ_DAY)
		return 0;

	if (cotime1->hour < cotime2->hour)
		return -1;
	if (cotime1->hour > cotime2->hour)
		return 1;

	if (type == CALOBJ_HOUR)
		return 0;

	if (cotime1->minute < cotime2->minute)
		return -1;
	if (cotime1->minute > cotime2->minute)
		return 1;

	if (type == CALOBJ_MINUTE)
		return 0;

	if (cotime1->second < cotime2->second)
		return -1;
	if (cotime1->second > cotime2->second)
		return 1;

	return 0;
}


/* This is the same as the above function, but without the comparison type.
   It is used for qsort(). */
static gint
cal_obj_time_compare_func (const void *arg1,
			   const void *arg2)
{
	CalObjTime *cotime1, *cotime2;
	gint retval;

	cotime1 = (CalObjTime*) arg1;
	cotime2 = (CalObjTime*) arg2;

	if (cotime1->year < cotime2->year)
		retval = -1;
	else if (cotime1->year > cotime2->year)
		retval = 1;

	else if (cotime1->month < cotime2->month)
		retval = -1;
	else if (cotime1->month > cotime2->month)
		retval = 1;

	else if (cotime1->day < cotime2->day)
		retval = -1;
	else if (cotime1->day > cotime2->day)
		retval = 1;

	else if (cotime1->hour < cotime2->hour)
		retval = -1;
	else if (cotime1->hour > cotime2->hour)
		retval = 1;

	else if (cotime1->minute < cotime2->minute)
		retval = -1;
	else if (cotime1->minute > cotime2->minute)
		retval = 1;

	else if (cotime1->second < cotime2->second)
		retval = -1;
	else if (cotime1->second > cotime2->second)
		retval = 1;

	else
		retval = 0;

#if 0
	g_print ("%s - ", cal_obj_time_to_string (cotime1));
	g_print ("%s : %i\n", cal_obj_time_to_string (cotime2), retval);
#endif

	return retval;
}


static gint
cal_obj_date_only_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;

	return 0;
}


/* Returns the weekday of the given CalObjTime, from 0 (Mon) - 6 (Sun). */
static gint
cal_obj_time_weekday		(CalObjTime *cotime)
{
	GDate date;
	gint weekday;

	g_date_clear (&date, 1);
	g_date_set_dmy (&date, cotime->day, cotime->month + 1, cotime->year);

	/* This results in a value of 0 (Monday) - 6 (Sunday). */
	weekday = g_date_get_weekday (&date) - 1;

	return weekday;
}


/* Returns the weekday of the given CalObjTime, from 0 - 6. The week start
   day is Monday by default, but can be set in the recurrence rule. */
static gint
cal_obj_time_weekday_offset	(CalObjTime *cotime,
				 ECalRecurrence *recur)
{
	GDate date;
	gint weekday, offset;

	g_date_clear (&date, 1);
	g_date_set_dmy (&date, cotime->day, cotime->month + 1, cotime->year);

	/* This results in a value of 0 (Monday) - 6 (Sunday). */
	weekday = g_date_get_weekday (&date) - 1;

	/* This calculates the offset of our day from the start of the week.
	   We just add on a week (to avoid any possible negative values) and
	   then subtract the specified week start day, then convert it into a
	   value from 0-6. */
	offset = (weekday + 7 - recur->week_start_day) % 7;

	return offset;
}


/* Returns the day of the year of the given CalObjTime, from 1 - 366. */
static gint
cal_obj_time_day_of_year		(CalObjTime *cotime)
{
	GDate date;

	g_date_clear (&date, 1);
	g_date_set_dmy (&date, cotime->day, cotime->month + 1, cotime->year);

	return g_date_get_day_of_year (&date);
}


/* Finds the first week in the given CalObjTime's year, using the same weekday
   as the event start day (i.e. from the RecurData).
   The first week of the year is the first week starting from the specified
   week start day that has 4 days in the new year. It may be in the previous
   year. */
static void
cal_obj_time_find_first_week	(CalObjTime *cotime,
				 RecurData  *recur_data)
{
	GDate date;
	gint weekday, week_start_day, first_full_week_start_offset, offset;

	/* Find out the weekday of the 1st of the year, 0 (Mon) - 6 (Sun). */
	g_date_clear (&date, 1);
	g_date_set_dmy (&date, 1, 1, cotime->year);
	weekday = g_date_get_weekday (&date) - 1;

	/* Calculate the first day of the year that starts a new week, i.e. the
	   first week_start_day after weekday, using 0 = 1st Jan.
	   e.g. if the 1st Jan is a Tuesday (1) and week_start_day is a
	   Monday (0), the result will be (0 + 7 - 1) % 7 = 6 (7th Jan). */
	week_start_day = recur_data->recur->week_start_day;
	first_full_week_start_offset = (week_start_day + 7 - weekday) % 7;

	/* Now see if we have to move backwards 1 week, i.e. if the week
	   starts on or after Jan 5th (since the previous week has 4 days in
	   this year and so will be the first week of the year). */
	if (first_full_week_start_offset >= 4)
		first_full_week_start_offset -= 7;

	/* Now add the days to get to the event's weekday. */
	offset = first_full_week_start_offset + recur_data->weekday_offset;

	/* Now move the cotime to the appropriate day. */
	cotime->month = 0;
	cotime->day = 1;
	cal_obj_time_add_days (cotime, offset);
}


static void
cal_object_time_from_time	(CalObjTime	*cotime,
				 time_t		 t,
				 icaltimezone	*zone)
{
	struct icaltimetype tt;

	if (zone)
		tt = icaltime_from_timet_with_zone (t, FALSE, zone);
	else
		tt = icaltime_from_timet (t, FALSE);

	cotime->year     = tt.year;
	cotime->month    = tt.month - 1;
	cotime->day      = tt.day;
	cotime->hour     = tt.hour;
	cotime->minute   = tt.minute;
	cotime->second   = tt.second;
	cotime->flags    = FALSE;
}


/* Debugging function to convert a CalObjTime to a string. It uses a static
   buffer so beware. */
#ifdef CAL_OBJ_DEBUG
static char*
cal_obj_time_to_string		(CalObjTime	*cotime)
{
	static char buffer[20];
	char *weekdays[] = { "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun",
			     "   " };
	gint weekday;

	weekday = cal_obj_time_weekday (cotime);

	sprintf (buffer, "%s %02i/%02i/%04i %02i:%02i:%02i",
		 weekdays[weekday],
		 cotime->day, cotime->month + 1, cotime->year,
		 cotime->hour, cotime->minute, cotime->second);
	return buffer;
}
#endif


/* This recalculates the end dates for recurrence & exception rules which use
   the COUNT property. If refresh is TRUE it will recalculate all enddates
   for rules which use COUNT. If refresh is FALSE, it will only calculate
   the enddate if it hasn't already been set. It returns TRUE if the component
   was changed, i.e. if the component should be saved at some point.
   We store the enddate in the "X-EVOLUTION-ENDDATE" parameter of the RRULE
   or EXRULE. */
static gboolean
e_cal_recur_ensure_end_dates (ECalComponent	*comp,
			    gboolean		 refresh,
			    ECalRecurResolveTimezoneFn  tz_cb,
			    gpointer		 tz_cb_data)
{
	GSList *rrules, *exrules, *elem;
	gboolean changed = FALSE;

	/* Do the RRULEs. */
	e_cal_component_get_rrule_property_list (comp, &rrules);
	for (elem = rrules; elem; elem = elem->next) {
		changed |= e_cal_recur_ensure_rule_end_date (comp, elem->data,
							   FALSE, refresh,
							   tz_cb, tz_cb_data);
	}

	/* Do the EXRULEs. */
	e_cal_component_get_exrule_property_list (comp, &exrules);
	for (elem = exrules; elem; elem = elem->next) {
		changed |= e_cal_recur_ensure_rule_end_date (comp, elem->data,
							   TRUE, refresh,
							   tz_cb, tz_cb_data);
	}

	return changed;
}


typedef struct _ECalRecurEnsureEndDateData ECalRecurEnsureEndDateData;
struct _ECalRecurEnsureEndDateData {
	gint count;
	gint instances;
	time_t end_date;
};


static gboolean
e_cal_recur_ensure_rule_end_date (ECalComponent			*comp,
				icalproperty			*prop,
				gboolean			 exception,
				gboolean			 refresh,
				ECalRecurResolveTimezoneFn	 tz_cb,
				gpointer			 tz_cb_data)
{
	struct icalrecurrencetype rule;
	ECalRecurEnsureEndDateData cb_data;

	if (exception)
		rule = icalproperty_get_exrule (prop);
	else
		rule = icalproperty_get_rrule (prop);

	/* If the rule doesn't use COUNT just return. */
	if (rule.count == 0)
		return FALSE;

	/* If refresh is FALSE, we check if the enddate is already set, and
	   if it is we just return. */
	if (!refresh) {
		if (e_cal_recur_get_rule_end_date (prop, NULL) != -1)
			return FALSE;
	}

	/* Calculate the end date. Note that we initialize end_date to 0, so
	   if the RULE doesn't generate COUNT instances we save a time_t of 0.
	   Also note that we use the UTC timezone as the default timezone.
	   In get_end_date() if the DTSTART is a DATE or floating time, we will
	   convert the ENDDATE to the current timezone. */
	cb_data.count = rule.count;
	cb_data.instances = 0;
	cb_data.end_date = 0;
	e_cal_recur_generate_instances_of_rule (comp, prop, -1, -1,
					      e_cal_recur_ensure_rule_end_date_cb,
					      &cb_data, tz_cb, tz_cb_data,
					      icaltimezone_get_utc_timezone ());

	/* Store the end date in the "X-EVOLUTION-ENDDATE" parameter of the
	   rule. */
	e_cal_recur_set_rule_end_date (prop, cb_data.end_date);
		
	return TRUE;
}


static gboolean
e_cal_recur_ensure_rule_end_date_cb	(ECalComponent	*comp,
					 time_t		 instance_start,
					 time_t		 instance_end,
					 gpointer	 data)
{
	ECalRecurEnsureEndDateData *cb_data;

	cb_data = (ECalRecurEnsureEndDateData*) data;

	cb_data->instances++;

	if (cb_data->instances == cb_data->count) {
		cb_data->end_date = instance_start;
		return FALSE;
	}

	return TRUE;
}


/* If default_timezone is set, the saved ENDDATE parameter is assumed to be
   in that timezone. This is used when the DTSTART is a DATE or floating
   value, since the RRULE end date will change depending on the timezone that
   it is evaluated in. */
static time_t
e_cal_recur_get_rule_end_date	(icalproperty	*prop,
				 icaltimezone	*default_timezone)
{
	icalparameter *param;
	const char *xname, *xvalue;
	icalvalue *value;
	struct icaltimetype icaltime;
	icaltimezone *zone;

	param = icalproperty_get_first_parameter (prop, ICAL_X_PARAMETER);
	while (param) {
		xname = icalparameter_get_xname (param);
		if (xname && !strcmp (xname, EVOLUTION_END_DATE_PARAMETER)) {
			xvalue = icalparameter_get_x (param);
			value = icalvalue_new_from_string (ICAL_DATETIME_VALUE,
							   xvalue);
			if (value) {
				icaltime = icalvalue_get_datetime (value);
				icalvalue_free (value);

				zone = default_timezone ? default_timezone : 
					icaltimezone_get_utc_timezone ();
				return icaltime_as_timet_with_zone (icaltime,
								    zone);
			}
		}

		param = icalproperty_get_next_parameter (prop,
							 ICAL_X_PARAMETER);
	}

	return -1;
}


static void
e_cal_recur_set_rule_end_date	(icalproperty	*prop,
				 time_t		 end_date)
{
	icalparameter *param;
	icalvalue *value;
	icaltimezone *utc_zone;
	struct icaltimetype icaltime;
	const char *end_date_string, *xname;

	/* We save the value as a UTC DATE-TIME. */
	utc_zone = icaltimezone_get_utc_timezone ();
	icaltime = icaltime_from_timet_with_zone (end_date, FALSE, utc_zone);
	value = icalvalue_new_datetime (icaltime);
	end_date_string = icalvalue_as_ical_string (value);
	icalvalue_free (value);

	/* If we already have an X-EVOLUTION-ENDDATE parameter, set the value
	   to the new date-time. */
	param = icalproperty_get_first_parameter (prop, ICAL_X_PARAMETER);
	while (param) {
		xname = icalparameter_get_xname (param);
		if (xname && !strcmp (xname, EVOLUTION_END_DATE_PARAMETER)) {
			icalparameter_set_x (param, end_date_string);
			return;
		}
		param = icalproperty_get_next_parameter (prop, ICAL_X_PARAMETER);
	}

	/* Create a new X-EVOLUTION-ENDDATE and add it to the property. */
	param = icalparameter_new_x (end_date_string);
	icalparameter_set_xname (param, EVOLUTION_END_DATE_PARAMETER);
	icalproperty_add_parameter (prop, param);
}

#ifdef G_OS_WIN32
#undef e_cal_recur_nth
static
#endif
const char *e_cal_recur_nth[31] = {
	N_("1st"),
	N_("2nd"),
	N_("3rd"),
	N_("4th"),
	N_("5th"),
	N_("6th"),
	N_("7th"),
	N_("8th"),
	N_("9th"),
	N_("10th"),
	N_("11th"),
	N_("12th"),
	N_("13th"),
	N_("14th"),
	N_("15th"),
	N_("16th"),
	N_("17th"),
	N_("18th"),
	N_("19th"),
	N_("20th"),
	N_("21st"),
	N_("22nd"),
	N_("23rd"),
	N_("24th"),
	N_("25th"),
	N_("26th"),
	N_("27th"),
	N_("28th"),
	N_("29th"),
	N_("30th"),
	N_("31st")
};

#ifdef G_OS_WIN32

const char **
e_cal_get_recur_nth (void)
{
	return e_cal_recur_nth;
}

#endif
