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Make occurrences in chronological order even if BYMONTHDAY or BYYEARD…
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…AY is not in order (#666)

The recurrence iterator has a problem where it makes occurrences in the same order as given in
BYMONTHDAY or BYYEARDAY, which doesn't make sense - it should always return them in chronological
order.

This patch fixes it by pre-ordering the days that can be used when the month or year changes.
A day that is valid for one month/year may be different or not valid for the next month/year, so
the days need to be recomputed each time.
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@darktrojan
darktrojan authored Apr 18, 2024
1 parent 3724e72 commit ae06bf4
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Showing 2 changed files with 284 additions and 80 deletions.
191 changes: 111 additions & 80 deletions lib/ical/recur_iterator.js
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Original file line number Diff line number Diff line change
Expand Up @@ -233,7 +233,7 @@ class RecurIterator {
this.last.second = this.setup_defaults("BYSECOND", "SECONDLY", this.dtstart.second);
this.last.minute = this.setup_defaults("BYMINUTE", "MINUTELY", this.dtstart.minute);
this.last.hour = this.setup_defaults("BYHOUR", "HOURLY", this.dtstart.hour);
let dayOffset = this.last.day = this.setup_defaults("BYMONTHDAY", "DAILY", this.dtstart.day);
this.last.day = this.setup_defaults("BYMONTHDAY", "DAILY", this.dtstart.day);
this.last.month = this.setup_defaults("BYMONTH", "MONTHLY", this.dtstart.month);

if (this.rule.freq == "WEEKLY") {
Expand Down Expand Up @@ -262,77 +262,79 @@ class RecurIterator {
this._nextByYearDay();
}

if (this.rule.freq == "MONTHLY" && this.has_by_data("BYDAY")) {
let tempLast = null;
let initLast = this.last.clone();
let daysInMonth = Time.daysInMonth(this.last.month, this.last.year);

// Check every weekday in BYDAY with relative dow and pos.
for (let bydow of this.by_data.BYDAY) {
this.last = initLast.clone();
let [pos, dow] = this.ruleDayOfWeek(bydow);
let dayOfMonth = this.last.nthWeekDay(dow, pos);

// If |pos| >= 6, the byday is invalid for a monthly rule.
if (pos >= 6 || pos <= -6) {
throw new Error("Malformed values in BYDAY part");
}
if (this.rule.freq == "MONTHLY") {
if (this.has_by_data("BYDAY")) {
let tempLast = null;
let initLast = this.last.clone();
let daysInMonth = Time.daysInMonth(this.last.month, this.last.year);

// Check every weekday in BYDAY with relative dow and pos.
for (let bydow of this.by_data.BYDAY) {
this.last = initLast.clone();
let [pos, dow] = this.ruleDayOfWeek(bydow);
let dayOfMonth = this.last.nthWeekDay(dow, pos);

// If |pos| >= 6, the byday is invalid for a monthly rule.
if (pos >= 6 || pos <= -6) {
throw new Error("Malformed values in BYDAY part");
}

// If a Byday with pos=+/-5 is not in the current month it
// must be searched in the next months.
if (dayOfMonth > daysInMonth || dayOfMonth <= 0) {
// Skip if we have already found a "last" in this month.
if (tempLast && tempLast.month == initLast.month) {
continue;
// If a Byday with pos=+/-5 is not in the current month it
// must be searched in the next months.
if (dayOfMonth > daysInMonth || dayOfMonth <= 0) {
// Skip if we have already found a "last" in this month.
if (tempLast && tempLast.month == initLast.month) {
continue;
}
while (dayOfMonth > daysInMonth || dayOfMonth <= 0) {
this.increment_month();
daysInMonth = Time.daysInMonth(this.last.month, this.last.year);
dayOfMonth = this.last.nthWeekDay(dow, pos);
}
}
while (dayOfMonth > daysInMonth || dayOfMonth <= 0) {
this.increment_month();
daysInMonth = Time.daysInMonth(this.last.month, this.last.year);
dayOfMonth = this.last.nthWeekDay(dow, pos);

this.last.day = dayOfMonth;
if (!tempLast || this.last.compare(tempLast) < 0) {
tempLast = this.last.clone();
}
}

this.last.day = dayOfMonth;
if (!tempLast || this.last.compare(tempLast) < 0) {
tempLast = this.last.clone();
this.last = tempLast.clone();

//XXX: This feels like a hack, but we need to initialize
// the BYMONTHDAY case correctly and byDayAndMonthDay handles
// this case. It accepts a special flag which will avoid incrementing
// the initial value without the flag days that match the start time
// would be missed.
if (this.has_by_data('BYMONTHDAY')) {
this._byDayAndMonthDay(true);
}
}
this.last = tempLast.clone();

//XXX: This feels like a hack, but we need to initialize
// the BYMONTHDAY case correctly and byDayAndMonthDay handles
// this case. It accepts a special flag which will avoid incrementing
// the initial value without the flag days that match the start time
// would be missed.
if (this.has_by_data('BYMONTHDAY')) {
this._byDayAndMonthDay(true);
}

if (this.last.day > daysInMonth || this.last.day == 0) {
throw new Error("Malformed values in BYDAY part");
}
} else if (this.has_by_data("BYMONTHDAY")) {
// Attempting to access `this.last.day` will cause the date to be normalised.
// So it will never be a negative value or more than the number of days in the month.
// We keep the value in a separate variable instead.

// Change the day value so that normalisation won't change the month.
this.last.day = 1;
let daysInMonth = Time.daysInMonth(this.last.month, this.last.year);
if (this.last.day > daysInMonth || this.last.day == 0) {
throw new Error("Malformed values in BYDAY part");
}
} else if (this.has_by_data("BYMONTHDAY")) {
// Change the day value so that normalisation won't change the month.
this.last.day = 1;

if (dayOffset < 0) {
// A negative value represents days before the end of the month.
this.last.day = daysInMonth + dayOffset + 1;
} else if (this.by_data.BYMONTHDAY[0] > daysInMonth) {
// There's no occurrence in this month, find the next valid month.
// The longest possible sequence of skipped months is February-April-June,
// so we might need to call next_month up to three times.
if (!this.next_month() && !this.next_month() && !this.next_month()) {
throw new Error("No possible occurrences");
// Get a sorted list of days in the starting month that match the rule.
let normalized = this.normalizeByMonthDayRules(
this.last.year,
this.last.month,
this.rule.parts.BYMONTHDAY
).filter(d => d >= this.last.day);

if (normalized.length) {
// There's at least one valid day, use it.
this.last.day = normalized[0];
this.by_data.BYMONTHDAY = normalized;
} else {
// There's no occurrence in this month, find the next valid month.
// The longest possible sequence of skipped months is February-April-June,
// so we might need to call next_month up to three times.
if (!this.next_month() && !this.next_month() && !this.next_month()) {
throw new Error("No possible occurrences");
}
}
} else {
// Otherwise, reset the day.
this.last.day = dayOffset;
}
}
}
Expand Down Expand Up @@ -513,7 +515,10 @@ class RecurIterator {
let rule;

for (; ruleIdx < len; ruleIdx++) {
rule = rules[ruleIdx];
rule = parseInt(rules[ruleIdx], 10);
if (isNaN(rule)) {
throw new Error('Invalid BYMONTHDAY value');
}

// if this rule falls outside of given
// month discard it.
Expand Down Expand Up @@ -747,6 +752,9 @@ class RecurIterator {
if (this.by_indices.BYMONTHDAY >= this.by_data.BYMONTHDAY.length) {
this.by_indices.BYMONTHDAY = 0;
this.increment_month();
if (this.by_indices.BYMONTHDAY >= this.by_data.BYMONTHDAY.length) {
return 0;
}
}

let daysInMonth = Time.daysInMonth(this.last.month, this.last.year);
Expand All @@ -762,7 +770,6 @@ class RecurIterator {
} else {
this.last.day = day;
}

} else {
this.increment_month();
let daysInMonth = Time.daysInMonth(this.last.month, this.last.year);
Expand Down Expand Up @@ -835,7 +842,6 @@ class RecurIterator {
}

next_year() {

if (this.next_hour() == 0) {
return 0;
}
Expand All @@ -844,6 +850,13 @@ class RecurIterator {
this.days_index = 0;
do {
this.increment_year(this.rule.interval);
if (this.has_by_data("BYMONTHDAY")) {
this.by_data.BYMONTHDAY = this.normalizeByMonthDayRules(
this.last.year,
this.last.month,
this.rule.parts.BYMONTHDAY
);
}
this.expand_year_days(this.last.year);
} while (this.days.length == 0);
}
Expand All @@ -854,19 +867,19 @@ class RecurIterator {
}

_nextByYearDay() {
let doy = this.days[this.days_index];
let year = this.last.year;
if (doy < 1) {
// Time.fromDayOfYear(doy, year) indexes relative to the
// start of the given year. That is different from the
// semantics of BYYEARDAY where negative indexes are an
// offset from the end of the given year.
doy += 1;
year += 1;
}
let next = Time.fromDayOfYear(doy, year);
this.last.day = next.day;
this.last.month = next.month;
let doy = this.days[this.days_index];
let year = this.last.year;
if (doy < 1) {
// Time.fromDayOfYear(doy, year) indexes relative to the
// start of the given year. That is different from the
// semantics of BYYEARDAY where negative indexes are an
// offset from the end of the given year.
doy += 1;
year += 1;
}
let next = Time.fromDayOfYear(doy, year);
this.last.day = next.day;
this.last.month = next.month;
}

/**
Expand Down Expand Up @@ -953,9 +966,19 @@ class RecurIterator {
this.increment_year(years);
}
}

if (this.has_by_data("BYMONTHDAY")) {
this.by_data.BYMONTHDAY = this.normalizeByMonthDayRules(
this.last.year,
this.last.month,
this.rule.parts.BYMONTHDAY
);
}
}

increment_year(inc) {
// Don't jump into the next month if this.last is Feb 29.
this.last.day = 1;
this.last.year += inc;
}

Expand Down Expand Up @@ -1177,6 +1200,14 @@ class RecurIterator {
} else {
this.days = [];
}

let daysInYear = Time.isLeapYear(aYear) ? 366 : 365;
this.days.sort((a, b) => {
if (a < 0) a += daysInYear + 1;
if (b < 0) b += daysInYear + 1;
return a - b;
});

return 0;
}

Expand Down
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