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Don't skip anchors with strict matching in Calendar.RecurrenceRule. Resolve #881 #1000

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merged 1 commit into from
Nov 1, 2024
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Don't skip anchors with strict matching in Calendar.RecurrenceRule. Resolve #881 #1000

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39 changes: 36 additions & 3 deletions Sources/FoundationEssentials/Calendar/Calendar_Recurrence.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -230,12 +230,42 @@ extension Calendar {
case .monthly: [.second, .minute, .hour, .day]
case .yearly: [.second, .minute, .hour, .day, .month]
}
let componentsForEnumerating = recurrence.calendar._dateComponents(components, from: start)
var componentsForEnumerating = recurrence.calendar._dateComponents(components, from: start)

let rangeForBaseRecurrence: Range<Date>? = nil
let expansionChangesDay = dayOfYearAction == .expand || dayOfMonthAction == .expand || weekAction == .expand || weekdayAction == .expand
let expansionChangesMonth = dayOfYearAction == .expand || monthAction == .expand || weekAction == .expand

if expansionChangesDay, componentsForEnumerating.day != nil {
// If we expand either the day of the month or weekday, then
// the day of month is likely to not match that of the start
// date. Reset it to 1 in the base recurrence as to not skip
// "invalid" anchors, such as February 30
componentsForEnumerating.day = 1
}
if expansionChangesMonth, componentsForEnumerating.month != nil {
// Likewise, if we will be changing the month, reset it to 1
// in case the start date falls on a leap month
componentsForEnumerating.month = 1
componentsForEnumerating.isLeapMonth = nil
}
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Would we also need to handle nth-weekday and yearly combination?

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Yes, good catch! Added more exhaustive checks and cleaned up the logic a bit to be easier to read

if expansionChangesDay || expansionChangesMonth, weekAction == .expand, weekdayAction != .expand {
// If we are expanding weeks, all expansions in a given year
// will have the same weekday. Above we have reset the month
// or the day of the month, so we also changed that weekday.

// To specify a yearly recurrence which starts from the same
// weekday, and which doesn't start from a leap day / month,
// simply use `dayOfYear` of the start date
componentsForEnumerating.day = nil
componentsForEnumerating.month = nil
componentsForEnumerating.isLeapMonth = nil
let daysInWeek = recurrence.calendar.maximumRange(of: .weekday)!.count
componentsForEnumerating.dayOfYear = recurrence.calendar.component(.dayOfYear, from: start) % daysInWeek // mod 7 to get the same weekday in the beginning of the year, so it's guaranteed to always exist
}

baseRecurrence = Calendar.DatesByMatching(calendar: recurrence.calendar,
start: start,
range: rangeForBaseRecurrence,
range: nil,
matchingComponents: componentsForEnumerating,
matchingPolicy: recurrence.matchingPolicy,
repeatedTimePolicy: recurrence.repeatedTimePolicy,
Expand Down Expand Up @@ -335,6 +365,9 @@ extension Calendar {
componentCombinations.weekdays = recurrence.weekdays
componentCombinations.daysOfYear = nil
componentCombinations.daysOfMonth = nil
if recurrence.frequency == .yearly, monthAction != .expand {
componentCombinations.months = nil
}
} else if recurrence.frequency == .weekly || weekAction == .expand {
if let weekdayIdx = components.weekday, let weekday = Locale.Weekday(weekdayIdx) {
// In a weekly recurrence (or one that expands weeks of year), we want results to fall on the same weekday as the initial date
Expand Down
63 changes: 63 additions & 0 deletions Tests/FoundationEssentialsTests/GregorianCalendarRecurrenceRuleTests.swift
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Expand Up @@ -676,4 +676,67 @@ final class GregorianCalendarRecurrenceRuleTests: XCTestCase {

XCTAssertEqual(results, [])
}

func testFirstMondaysStrictMatching() {
let startDate = Date(timeIntervalSince1970: 1706659200.0) // 2024-01-31T00:00:00-0000

var rule = Calendar.RecurrenceRule(calendar: gregorian, frequency: .monthly, matchingPolicy: .strict)
rule.weekdays = [.nth(1, .monday)]

var dates = rule.recurrences(of: startDate).makeIterator()
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1707091200.0)) // 2024-02-05T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1709510400.0)) // 2024-03-04T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1711929600.0)) // 2024-04-01T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1714953600.0)) // 2024-05-06T00:00:00-0000
}

func testFifthFridaysStrictMatching() {
let startDate = Date(timeIntervalSince1970: 1706659200.0) // 2024-01-31T00:00:00-0000

var rule = Calendar.RecurrenceRule(calendar: gregorian, frequency: .monthly, matchingPolicy: .strict)
rule.weekdays = [.nth(5, .friday)]

var dates = rule.recurrences(of: startDate).makeIterator()
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1711670400.0)) // 2024-03-29T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1717113600.0)) // 2024-05-31T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1724976000.0)) // 2024-08-30T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1732838400.0)) // 2024-11-29T00:00:00-0000
}

func testYearlyRecurrenceWeekdayExpansionStrictMatching() {
let startDate = Date(timeIntervalSince1970: 1709164800.0) // 2024-02-29T00:00:00-0000

var rule = Calendar.RecurrenceRule(calendar: gregorian, frequency: .yearly, matchingPolicy: .strict)
rule.weekdays = [.nth(5, .friday)]

var dates = rule.recurrences(of: startDate).makeIterator()
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1738281600.0)) // 2025-01-31T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1769731200.0)) // 2026-01-30T00:00:00-0000
}

func testYearlyRecurrenceDayOfYearExpansionStrictMatching() {
let startDate = Date(timeIntervalSince1970: 1709164800.0) // 2024-02-29T00:00:00-0000

var rule = Calendar.RecurrenceRule(calendar: gregorian, frequency: .yearly, matchingPolicy: .strict)
rule.daysOfTheYear = [61]

var dates = rule.recurrences(of: startDate).makeIterator()
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1709251200.0)) // 2024-03-01T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1740873600.0)) // 2025-03-02T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1772409600.0)) // 2026-03-02T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1803945600.0)) // 2027-03-02T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1835481600.0)) // 2028-03-01T00:00:00-0000
}

func testYearlyRecurrenceWeekExpansionStrictMatching() {
let startDate = Date(timeIntervalSince1970: 1709164800.0) // 2024-02-29T00:00:00-0000

var rule = Calendar.RecurrenceRule(calendar: gregorian, frequency: .yearly, matchingPolicy: .strict)
rule.weeks = [2]

var dates = rule.recurrences(of: startDate).makeIterator()
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1736553600.0)) // 2025-01-11T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1767484800.0)) // 2026-01-04T00:00:00-0000
XCTAssertEqual(dates.next(), Date(timeIntervalSince1970: 1799020800.0)) // 2027-01-04T00:00:00-0000
}
}