dovenest

dovenest/pimdav/src/expand.rs
expand.rs
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1//! Recurrence expansion: DTSTART + RRULE + RDATE - EXRULE - EXDATE, with
2//! RECURRENCE-ID overrides applied.
3
4use std::collections::{BTreeMap, HashMap, HashSet};
5use std::ops::Range;
6
7use calcard::common::{CalendarScale, PartialDateTime};
8use calcard::icalendar::{
9 ICalendar, ICalendarComponent, ICalendarComponentType, ICalendarDuration, ICalendarFrequency,
10 ICalendarParameterName, ICalendarPeriod, ICalendarProperty, ICalendarRecurrenceRule,
11 ICalendarSkip, ICalendarValue,
12};
13use chrono::{DateTime, NaiveDateTime, NaiveTime, TimeDelta, TimeZone, Timelike, Utc, Weekday};
14
15use crate::zone::{Zone, Zones, add, add_local};
16
17/// Occurrences the rules of one series may generate together before
18/// expansion gives up.
19// ponytail: COUNT, MONTHLY and YEARLY rules iterate from DTSTART, so a long
20// running one can hit this. Skip ahead for them if that matters.
21const MAX_OCCURRENCES: usize = 1_000_000;
22
23#[derive(Debug, Clone, PartialEq)]
24pub struct Instance {
25 pub start: DateTime<Utc>,
26 pub end: DateTime<Utc>,
27 /// The original start. `None` if the component does not recur.
28 pub recurrence_id: Option<DateTime<Utc>>,
29 /// Index into `ICalendar::components` of the master or override that
30 /// describes this instance.
31 pub component: usize,
32}
33
34#[derive(Debug, Default)]
35pub struct Expansion {
36 /// Sorted by start.
37 pub instances: Vec<Instance>,
38 /// A series reached `MAX_OCCURRENCES`, so later instances are missing.
39 pub truncated: bool,
40}
41
42/// The instances of all VEVENT, VTODO and VJOURNAL components that overlap
43/// `window`. A zero-length instance overlaps if it starts inside.
44///
45/// Components are grouped by type and UID into one master and its overrides.
46/// Components without DTSTART are skipped. `floating` interprets values
47/// without a zone.
48pub fn expand(cal: &ICalendar, window: Range<DateTime<Utc>>, floating: Zone) -> Expansion {
49 let zones = Zones::new(cal, floating);
50 let mut out = Expansion::default();
51 let mut groups: HashMap<(&ICalendarComponentType, &str), Vec<usize>> = HashMap::new();
52 for (i, c) in cal.components.iter().enumerate() {
53 if !matches!(
54 c.component_type,
55 ICalendarComponentType::VEvent
56 | ICalendarComponentType::VTodo
57 | ICalendarComponentType::VJournal
58 ) {
59 continue;
60 }
61 match c.uid() {
62 Some(uid) => groups.entry((&c.component_type, uid)).or_default().push(i),
63 None => expand_group(cal, &zones, &[i], &window, &mut out),
64 }
65 }
66 for group in groups.values() {
67 expand_group(cal, &zones, group, &window, &mut out);
68 }
69 out.instances.sort_by_key(|i| (i.start, i.component));
70 out
71}
72
73/// A date or date-time value and the zone it is in.
74#[derive(Debug, Clone)]
75pub(crate) struct Stamp {
76 pub(crate) local: NaiveDateTime,
77 zone: Zone,
78 pub(crate) date: bool,
79 /// A date-time without TZID or UTC offset.
80 floating: bool,
81}
82
83impl Stamp {
84 pub(crate) fn utc(&self) -> DateTime<Utc> {
85 self.zone.to_utc(self.local)
86 }
87}
88
89#[derive(Debug, Clone)]
90enum Length {
91 Exact(TimeDelta),
92 /// Whole days count in wall-clock time, so a day can last 23 or 25 hours.
93 Nominal {
94 days: i64,
95 exact: TimeDelta,
96 },
97}
98
99impl Length {
100 fn end(&self, zone: &Zone, local: NaiveDateTime, utc: DateTime<Utc>) -> DateTime<Utc> {
101 match self {
102 Length::Exact(d) => add(utc, *d),
103 Length::Nominal { days, exact } => add(
104 zone.to_utc(add_local(local, TimeDelta::days(*days))),
105 *exact,
106 ),
107 }
108 }
109
110 /// An upper bound, for widening the generation window.
111 fn max(&self) -> TimeDelta {
112 match self {
113 Length::Exact(d) => *d,
114 Length::Nominal { days, exact } => TimeDelta::days(days + 1) + *exact,
115 }
116 }
117}
118
119/// DTSTART and length of one component.
120#[derive(Debug, Clone)]
121struct Timing {
122 start: Stamp,
123 length: Length,
124 component: usize,
125}
126
127impl Timing {
128 fn of(cal: &ICalendar, zones: &Zones, component: usize) -> Option<Self> {
129 let c = &cal.components[component];
130 let start = prop_stamp(zones, c, &ICalendarProperty::Dtstart)?;
131 let end = match c.component_type {
132 ICalendarComponentType::VTodo => ICalendarProperty::Due,
133 _ => ICalendarProperty::Dtend,
134 };
135 let zero = TimeDelta::zero();
136 let length = if let Some(end) = prop_stamp(zones, c, &end) {
137 if start.date && end.date {
138 Length::Nominal {
139 days: (end.local - start.local).num_days().max(0),
140 exact: zero,
141 }
142 } else {
143 Length::Exact((end.utc() - start.utc()).max(zero))
144 }
145 } else if let Some(ICalendarValue::Duration(d)) = c
146 .property(&ICalendarProperty::Duration)
147 .and_then(|e| e.values.first())
148 {
149 nominal(d)
150 } else if start.date {
151 Length::Nominal {
152 days: 1,
153 exact: zero,
154 }
155 } else {
156 Length::Exact(zero)
157 };
158 Some(Timing {
159 start,
160 length,
161 component,
162 })
163 }
164
165 fn end_at(&self, local: NaiveDateTime, utc: DateTime<Utc>) -> DateTime<Utc> {
166 self.length.end(&self.start.zone, local, utc)
167 }
168
169 /// A RECURRENCE-ID, RDATE or EXDATE value. Dates and floating times are
170 /// read in the zone of the series: clients write them that way.
171 fn utc_of(&self, s: &Stamp) -> DateTime<Utc> {
172 if s.date || s.floating {
173 self.start.zone.to_utc(s.local)
174 } else {
175 s.utc()
176 }
177 }
178
179 /// The identity of a recurrence instance. An all-day series matches by
180 /// date alone, whatever zone the other value names.
181 fn key(&self, s: &Stamp) -> i64 {
182 if self.start.date {
183 day_key(s.local)
184 } else {
185 self.utc_of(s).timestamp()
186 }
187 }
188
189 fn member_key(&self, local: NaiveDateTime, utc: DateTime<Utc>) -> i64 {
190 if self.start.date {
191 day_key(local)
192 } else {
193 utc.timestamp()
194 }
195 }
196}
197
198struct Member {
199 local: NaiveDateTime,
200 utc: DateTime<Utc>,
201 /// From an RDATE period.
202 length: Option<Length>,
203}
204
205struct Override {
206 sequence: i64,
207 recurrence_id: DateTime<Utc>,
208 timing: Timing,
209}
210
211fn expand_group(
212 cal: &ICalendar,
213 zones: &Zones,
214 group: &[usize],
215 window: &Range<DateTime<Utc>>,
216 out: &mut Expansion,
217) {
218 let comp = |i: usize| &cal.components[i];
219 let sequence = |i: usize| {
220 comp(i)
221 .property(&ICalendarProperty::Sequence)
222 .and_then(|e| e.values.first()?.as_integer())
223 .unwrap_or(0)
224 };
225 let (overrides, masters): (Vec<usize>, Vec<usize>) = group
226 .iter()
227 .partition(|&&i| comp(i).has_property(&ICalendarProperty::RecurrenceId));
228 // Several masters for one UID are invalid. Take the latest revision,
229 // or the first one on a tie.
230 let master = masters
231 .into_iter()
232 .rev()
233 .max_by_key(|&i| sequence(i))
234 .and_then(|i| Timing::of(cal, zones, i));
235
236 // Matched by RECURRENCE-ID only. SEQUENCE picks between two overrides of
237 // one instance and never decides whether an override applies.
238 let mut exact: HashMap<i64, Override> = HashMap::new();
239 let mut future: Vec<(i64, DateTime<Utc>, Timing)> = Vec::new();
240 for i in overrides {
241 let Some(e) = comp(i).property(&ICalendarProperty::RecurrenceId) else {
242 continue;
243 };
244 let (Some(timing), Some(rid)) = (
245 Timing::of(cal, zones, i),
246 e.values
247 .first()
248 .and_then(|v| stamp(zones, v.as_partial_date_time()?, e.tz_id())),
249 ) else {
250 continue;
251 };
252 let (key, rid_utc) = match &master {
253 Some(m) => (m.key(&rid), m.utc_of(&rid)),
254 None => (rid.utc().timestamp(), rid.utc()),
255 };
256 if e.parameter(&ICalendarParameterName::Range).is_some() {
257 future.push((key, rid_utc, timing.clone()));
258 }
259 if exact.get(&key).is_none_or(|old| sequence(i) > old.sequence) {
260 let sequence = sequence(i);
261 exact.insert(
262 key,
263 Override {
264 sequence,
265 recurrence_id: rid_utc,
266 timing,
267 },
268 );
269 }
270 }
271 future.sort_by_key(|f| f.0);
272
273 let Some(m) = master else {
274 push_overrides(out, window, exact.values());
275 return;
276 };
277 let mc = comp(m.component);
278 let mz = &m.start.zone;
279
280 let rules: Vec<_> = mc
281 .properties(&ICalendarProperty::Rrule)
282 .filter_map(|e| rule(e.values.first()?))
283 .collect();
284 let mut set: BTreeMap<i64, Member> = BTreeMap::new();
285 let mut slack = m.length.max();
286 // DTSTART is an instance even when it does not match the RRULE, unless
287 // the series ended before it.
288 let ended = !rules.is_empty()
289 && rules.iter().all(|r| {
290 r.until
291 .as_ref()
292 .and_then(|u| until_local(u, &m.start))
293 .is_some_and(|u| u < m.start.local)
294 });
295 if !ended {
296 let utc = m.start.utc();
297 set.insert(
298 m.member_key(m.start.local, utc),
299 Member {
300 local: m.start.local,
301 utc,
302 length: None,
303 },
304 );
305 }
306 for e in mc.properties(&ICalendarProperty::Rdate) {
307 for v in &e.values {
308 let (s, length) = match v {
309 ICalendarValue::PartialDateTime(p) => {
310 let Some(s) = stamp(zones, p, e.tz_id()) else {
311 continue;
312 };
313 (s, None)
314 }
315 ICalendarValue::Period(ICalendarPeriod::Range { start, end }) => {
316 let (Some(s), Some(end)) =
317 (stamp(zones, start, e.tz_id()), stamp(zones, end, e.tz_id()))
318 else {
319 continue;
320 };
321 let d = (end.utc() - s.utc()).max(TimeDelta::zero());
322 (s, Some(Length::Exact(d)))
323 }
324 ICalendarValue::Period(ICalendarPeriod::Duration { start, duration }) => {
325 let Some(s) = stamp(zones, start, e.tz_id()) else {
326 continue;
327 };
328 (s, Some(nominal(duration)))
329 }
330 _ => continue,
331 };
332 let utc = m.utc_of(&s);
333 let local = mz.to_local(utc);
334 if let Some(l) = &length {
335 slack = slack.max(l.max());
336 }
337 // A period on DTSTART or a rule instance still sets its length.
338 let member = set.entry(m.key(&s)).or_insert(Member {
339 local,
340 utc,
341 length: None,
342 });
343 member.length = length.or(member.length.take());
344 }
345 }
346 for (_, rid, t) in &future {
347 slack = slack.max((t.start.utc() - *rid).abs() + t.length.max());
348 }
349 let slack = slack + TimeDelta::days(1);
350 let (from, to) = (add(window.start, -slack), add(window.end, slack));
351 let (from_local, to_local) = (mz.to_local(from), mz.to_local(to));
352
353 let mut budget = MAX_OCCURRENCES;
354 let mut excluded = HashSet::new();
355 for e in mc.properties(&ICalendarProperty::Exrule) {
356 let Some(rule) = e.values.first().and_then(rule) else {
357 continue;
358 };
359 for local in occurrences_capped(rule, &m, from_local, to_local, &mut budget, out) {
360 excluded.insert(m.member_key(local, mz.to_utc(local)));
361 }
362 }
363 // ponytail: sub-daily rules iterate in wall time. A DST fall-back skips the
364 // repeated hour, and a spring-forward collapses a shifted instance into the
365 // next (COUNT=5 gives 4). Iterate in elapsed time, BYHOUR in local, to fix.
366 for rule in rules {
367 for local in occurrences_capped(rule, &m, from_local, to_local, &mut budget, out) {
368 let utc = mz.to_utc(local);
369 if utc >= from {
370 set.entry(m.member_key(local, utc)).or_insert(Member {
371 local,
372 utc,
373 length: None,
374 });
375 }
376 }
377 }
378
379 // A DATE EXDATE on a DATE-TIME series removes every instance on that day.
380 let mut excluded_days = HashSet::new();
381 for e in mc.properties(&ICalendarProperty::Exdate) {
382 for s in e
383 .values
384 .iter()
385 .filter_map(|v| stamp(zones, v.as_partial_date_time()?, e.tz_id()))
386 {
387 if s.date && !m.start.date {
388 excluded_days.insert(s.local.date());
389 } else {
390 excluded.insert(m.key(&s));
391 }
392 }
393 }
394
395 // An EXDATE removes an override of that instance too. An override whose
396 // RECURRENCE-ID matches no instance still shows, as in clients.
397 push_overrides(
398 out,
399 window,
400 exact.iter().filter_map(|(key, o)| {
401 let day = mz.to_local(o.recurrence_id).date();
402 (!excluded.contains(key) && !excluded_days.contains(&day)).then_some(o)
403 }),
404 );
405
406 let recurs =
407 mc.has_property(&ICalendarProperty::Rrule) || mc.has_property(&ICalendarProperty::Rdate);
408 for (key, member) in &set {
409 if member.utc < from
410 || excluded.contains(key)
411 || excluded_days.contains(&member.local.date())
412 || exact.contains_key(key)
413 {
414 continue;
415 }
416 let recurrence_id = recurs.then_some(member.utc);
417 // The latest THISANDFUTURE override before this instance moves it by
418 // the same offset and gives it the override's length. The offset is
419 // wall-clock time, so later instances keep their local time across DST.
420 let instance = match future.iter().rev().find(|f| f.0 <= *key) {
421 Some((_, rid, t)) => {
422 let shift = mz.to_local(t.start.utc()) - mz.to_local(*rid);
423 let start = mz.to_utc(add_local(member.local, shift));
424 Instance {
425 start,
426 end: t.end_at(t.start.zone.to_local(start), start),
427 recurrence_id,
428 component: t.component,
429 }
430 }
431 None => Instance {
432 start: member.utc,
433 end: member.length.as_ref().map_or_else(
434 || m.end_at(member.local, member.utc),
435 |l| l.end(mz, member.local, member.utc),
436 ),
437 recurrence_id,
438 component: m.component,
439 },
440 };
441 push(out, window, instance);
442 }
443}
444
445fn push_overrides<'a>(
446 out: &mut Expansion,
447 window: &Range<DateTime<Utc>>,
448 overrides: impl Iterator<Item = &'a Override>,
449) {
450 for o in overrides {
451 let t = &o.timing;
452 let start = t.start.utc();
453 let end = t.end_at(t.start.local, start);
454 push(
455 out,
456 window,
457 Instance {
458 start,
459 end,
460 recurrence_id: Some(o.recurrence_id),
461 component: t.component,
462 },
463 );
464 }
465}
466
467fn occurrences_capped(
468 rule: &ICalendarRecurrenceRule,
469 m: &Timing,
470 from_local: NaiveDateTime,
471 to_local: NaiveDateTime,
472 budget: &mut usize,
473 out: &mut Expansion,
474) -> Vec<NaiveDateTime> {
475 let until = match &rule.until {
476 Some(u) => match until_local(u, &m.start) {
477 Some(u) => Some(u),
478 None => return Vec::new(),
479 },
480 None => None,
481 };
482 // Whole steps keep the period grid, so INTERVAL and BYxxx still line up.
483 let unit = match rule.freq {
484 ICalendarFrequency::Weekly => 7 * 86400,
485 ICalendarFrequency::Daily => 86400,
486 ICalendarFrequency::Hourly => 3600,
487 ICalendarFrequency::Minutely => 60,
488 ICalendarFrequency::Secondly => 1,
489 _ => 0,
490 };
491 let mut first = m.start.local;
492 if unit > 0 && rule.count.is_none() {
493 let step = unit * i64::from(rule.interval.unwrap_or(1).max(1));
494 let behind = (from_local - first).num_seconds();
495 if behind > 0 {
496 first += TimeDelta::seconds(behind / step * step);
497 }
498 }
499 let mut list: Vec<_> = occurrences(rule, first, until, to_local)
500 .take(*budget + 1)
501 .collect();
502 if list.len() > *budget {
503 list.pop();
504 out.truncated = true;
505 }
506 *budget -= list.len();
507 // DTSTART is the first of COUNT (RFC 5545, 3.3.10), also when the rule
508 // skips it.
509 if let Some(n) = rule.count.filter(|_| until.is_none()).map(|n| n as usize)
510 && list.first() != Some(&m.start.local)
511 && list.len() >= n
512 {
513 list.truncate(n.saturating_sub(1));
514 }
515 list
516}
517
518fn push(out: &mut Expansion, window: &Range<DateTime<Utc>>, i: Instance) {
519 let overlaps = if i.start == i.end {
520 window.contains(&i.start)
521 } else {
522 i.start < window.end && i.end > window.start
523 };
524 if overlaps {
525 out.instances.push(i);
526 }
527}
528
529/// UNTIL as wall-clock time in the zone of DTSTART. The rule iterates in wall
530/// time, so a UTC UNTIL compared as-is cuts the last instance east of UTC.
531fn until_local(u: &PartialDateTime, start: &Stamp) -> Option<NaiveDateTime> {
532 let dt = u.to_date_time()?;
533 Some(match dt.offset {
534 Some(o) => {
535 let utc = dt.date_time - TimeDelta::seconds(o.local_minus_utc().into());
536 let local = start.zone.to_local(utc.and_utc());
537 match start.date {
538 // Clients write midnight in UTC or in their own zone. The
539 // later date is the last day either way.
540 true => utc.date().max(local.date()).and_hms_opt(23, 59, 59)?,
541 false => local,
542 }
543 }
544 // A DATE on a DATE-TIME series includes that whole day.
545 None if u.hour.is_none() && !start.date => dt.date_time.date().and_hms_opt(23, 59, 59)?,
546 // Floating, or a DATE on an all-day series: already wall time.
547 None => dt.date_time,
548 })
549}
550
551fn day_key(local: NaiveDateTime) -> i64 {
552 local.date().and_time(NaiveTime::MIN).and_utc().timestamp()
553}
554
555fn nominal(d: &ICalendarDuration) -> Length {
556 if d.neg {
557 return Length::Exact(TimeDelta::zero());
558 }
559 Length::Nominal {
560 days: i64::from(d.weeks) * 7 + i64::from(d.days),
561 exact: TimeDelta::seconds(
562 i64::from(d.hours) * 3600 + i64::from(d.minutes) * 60 + i64::from(d.seconds),
563 ),
564 }
565}
566
567pub(crate) fn stamp(zones: &Zones, v: &PartialDateTime, tzid: Option<&str>) -> Option<Stamp> {
568 let dt = v.to_date_time()?;
569 let date = v.hour.is_none();
570 let zone = match dt.offset {
571 Some(o) if o.local_minus_utc() == 0 => Zone::Utc,
572 Some(o) => Zone::Fixed(o.local_minus_utc()),
573 None if date => zones.floating().clone(),
574 None => zones.get(tzid),
575 };
576 Some(Stamp {
577 local: dt.date_time,
578 zone,
579 date,
580 floating: !date && dt.offset.is_none() && tzid.is_none(),
581 })
582}
583
584fn prop_stamp(zones: &Zones, c: &ICalendarComponent, prop: &ICalendarProperty) -> Option<Stamp> {
585 let e = c.property(prop)?;
586 stamp(zones, e.values.first()?.as_partial_date_time()?, e.tz_id())
587}
588
589pub(crate) fn rule(v: &ICalendarValue) -> Option<&ICalendarRecurrenceRule> {
590 match v {
591 ICalendarValue::RecurrenceRule(r) => Some(r),
592 _ => None,
593 }
594}
595
596/// Wall-clock occurrences of `rule` from `start` up to `end`. An invalid or
597/// unsupported rule yields none.
598pub(crate) fn occurrences(
599 rule: &ICalendarRecurrenceRule,
600 start: NaiveDateTime,
601 until: Option<NaiveDateTime>,
602 end: NaiveDateTime,
603) -> impl Iterator<Item = NaiveDateTime> {
604 let wall = |t: NaiveDateTime| rrule::Tz::UTC.from_utc_datetime(&t);
605 let freq = match rule.freq {
606 ICalendarFrequency::Yearly => rrule::Frequency::Yearly,
607 ICalendarFrequency::Monthly => rrule::Frequency::Monthly,
608 ICalendarFrequency::Weekly => rrule::Frequency::Weekly,
609 ICalendarFrequency::Daily => rrule::Frequency::Daily,
610 ICalendarFrequency::Hourly => rrule::Frequency::Hourly,
611 ICalendarFrequency::Minutely => rrule::Frequency::Minutely,
612 ICalendarFrequency::Secondly => rrule::Frequency::Secondly,
613 };
614 // Other calendar scales and leap months (RFC 7529) are unsupported. RFC
615 // 7529 allows treating such a rule as absent.
616 let months: Option<Vec<chrono::Month>> = rule
617 .bymonth
618 .iter()
619 .map(|m| (!m.is_leap()).then(|| chrono::Month::try_from(m.month()).ok())?)
620 .collect();
621 let valid = months.is_some()
622 && rule
623 .rscale
624 .as_ref()
625 .is_none_or(|s| *s == CalendarScale::Gregorian)
626 && rule.skip.is_none_or(|s| s == ICalendarSkip::Omit);
627 // rrule intersects plain and numbered weekdays, RFC 5545 unites them.
628 // Numbering every occurrence of the plain ones gives the union.
629 let mixed = rule.byday.iter().any(|d| d.ordwk.is_some())
630 && rule.byday.iter().any(|d| d.ordwk.is_none());
631 let max_nth = if rule.freq == ICalendarFrequency::Monthly || !rule.bymonth.is_empty() {
632 5
633 } else {
634 53
635 };
636 let weekdays = rule
637 .byday
638 .iter()
639 .flat_map(|d| {
640 let wd = d.weekday.into();
641 match d.ordwk {
642 Some(n) => vec![rrule::NWeekday::Nth(n, wd)],
643 None if mixed => (1..=max_nth).map(|n| rrule::NWeekday::Nth(n, wd)).collect(),
644 None => vec![rrule::NWeekday::Every(wd)],
645 }
646 })
647 .collect();
648 let interval = rule.interval.unwrap_or(1).max(1);
649 // rrule loses the INTERVAL grid when it jumps to the next allowed hour or
650 // minute and the interval does not divide 60. Filter those limits here.
651 let (hours, minutes) = match rule.freq {
652 ICalendarFrequency::Minutely if 60 % interval != 0 => (rule.byhour.clone(), Vec::new()),
653 ICalendarFrequency::Secondly if 60 % interval != 0 => {
654 (rule.byhour.clone(), rule.byminute.clone())
655 }
656 _ => (Vec::new(), Vec::new()),
657 };
658 let filtered = !(hours.is_empty() && minutes.is_empty());
659 let mut r = rrule::RRule::new(freq)
660 .interval(interval)
661 .week_start(rule.wkst.map_or(Weekday::Mon, Into::into))
662 .by_set_pos(rule.bysetpos.clone())
663 .by_month(&months.unwrap_or_default())
664 .by_month_day(rule.bymonthday.clone())
665 .by_year_day(rule.byyearday.clone())
666 .by_week_no(rule.byweekno.clone())
667 .by_weekday(weekdays)
668 .by_hour(if hours.is_empty() {
669 rule.byhour.clone()
670 } else {
671 Vec::new()
672 })
673 .by_minute(if minutes.is_empty() {
674 rule.byminute.clone()
675 } else {
676 Vec::new()
677 })
678 .by_second(rule.bysecond.clone());
679 // COUNT and UNTIL together are invalid. UNTIL is the safer bound.
680 let count = rule.count.filter(|_| until.is_none());
681 if let Some(n) = count.filter(|_| !filtered) {
682 r = r.count(n);
683 }
684 if let Some(u) = until {
685 r = r.until(wall(u));
686 }
687 r.build(wall(start))
688 .ok()
689 .filter(|_| valid)
690 // Stops a rule that never matches after 100k periods, not at year 9999.
691 .map(|set| (&set.limit()).into_iter())
692 .into_iter()
693 .flatten()
694 .map(|t| t.naive_utc())
695 .filter(move |t| {
696 (hours.is_empty() || hours.contains(&(t.hour() as u8)))
697 && (minutes.is_empty() || minutes.contains(&(t.minute() as u8)))
698 })
699 .take(
700 count
701 .filter(|_| filtered)
702 .map_or(usize::MAX, |n| n as usize),
703 )
704 .take_while(move |t| *t <= end)
705}
706