LibJS: Implement the Temporal.PlainMonthDay constructor

And the simple Temporal.PlainMonthDay.prototype getters, so that the constructed Temporal.PlainMonthDay may actually be validated.
Author: https://github.com/trflynn89 Commit: 1a386e78c3 Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2471
2025-08-10 01:59:31 +00:00 · 2024-11-20 12:59:15 -05:00 · 2024-11-20 12:59:15 -05:00 · 1a386e78c3 · 2024-11-22 00:25:44 +00:00
commit 1a386e78c3
parent b3b968bed9
31 changed files with 2515 additions and 4 deletions
--- a/Libraries/LibJS/Runtime/Temporal/DateEquations.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/DateEquations.cpp
@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/AbstractOperations.h>
+#include <LibJS/Runtime/Date.h>
+#include <LibJS/Runtime/Temporal/DateEquations.h>
+
+namespace JS::Temporal {
+
+// https://tc39.es/proposal-temporal/#eqn-mathematicaldaysinyear
+u16 mathematical_days_in_year(i32 year)
+{
+    // MathematicalDaysInYear(y)
+    //     = 365 if ((y) modulo 4) ≠ 0
+    //     = 366 if ((y) modulo 4) = 0 and ((y) modulo 100) ≠ 0
+    //     = 365 if ((y) modulo 100) = 0 and ((y) modulo 400) ≠ 0
+    //     = 366 if ((y) modulo 400) = 0
+    if (modulo(year, 4) != 0)
+        return 365;
+    if (modulo(year, 4) == 0 && modulo(year, 100) != 0)
+        return 366;
+    if (modulo(year, 100) == 0 && modulo(year, 400) != 0)
+        return 365;
+    if (modulo(year, 400) == 0)
+        return 366;
+    VERIFY_NOT_REACHED();
+}
+
+// https://tc39.es/proposal-temporal/#eqn-mathematicalinleapyear
+u8 mathematical_in_leap_year(double time)
+{
+    // MathematicalInLeapYear(t)
+    //     = 0 if MathematicalDaysInYear(EpochTimeToEpochYear(t)) = 365
+    //     = 1 if MathematicalDaysInYear(EpochTimeToEpochYear(t)) = 366
+    auto days_in_year = mathematical_days_in_year(epoch_time_to_epoch_year(time));
+
+    if (days_in_year == 365)
+        return 0;
+    if (days_in_year == 366)
+        return 1;
+    VERIFY_NOT_REACHED();
+}
+
+// https://tc39.es/proposal-temporal/#eqn-EpochTimeToDayNumber
+double epoch_time_to_day_number(double time)
+{
+    // EpochTimeToDayNumber(t) = floor(t / ℝ(msPerDay))
+    return floor(time / JS::ms_per_day);
+}
+
+// https://tc39.es/proposal-temporal/#eqn-epochdaynumberforyear
+double epoch_day_number_for_year(double year)
+{
+    // EpochDayNumberForYear(y) = 365 × (y - 1970) + floor((y - 1969) / 4) - floor((y - 1901) / 100) + floor((y - 1601) / 400)
+    return 365.0 * (year - 1970.0) + floor((year - 1969.0) / 4.0) - floor((year - 1901.0) / 100.0) + floor((year - 1601.0) / 400.0);
+}
+
+// https://tc39.es/proposal-temporal/#eqn-epochtimeforyear
+double epoch_time_for_year(double year)
+{
+    // EpochTimeForYear(y) = ℝ(msPerDay) × EpochDayNumberForYear(y)
+    return ms_per_day * epoch_day_number_for_year(year);
+}
+
+// https://tc39.es/proposal-temporal/#eqn-epochtimetoepochyear
+i32 epoch_time_to_epoch_year(double time)
+{
+    // EpochTimeToEpochYear(t) = the largest integral Number y (closest to +∞) such that EpochTimeForYear(y) ≤ t
+    return JS::year_from_time(time);
+}
+
+// https://tc39.es/proposal-temporal/#eqn-epochtimetodayinyear
+u16 epoch_time_to_day_in_year(double time)
+{
+    // EpochTimeToDayInYear(t) = EpochTimeToDayNumber(t) - EpochDayNumberForYear(EpochTimeToEpochYear(t))
+    return static_cast<u16>(epoch_time_to_day_number(time) - epoch_day_number_for_year(epoch_time_to_epoch_year(time)));
+}
+
+// https://tc39.es/proposal-temporal/#eqn-epochtimetoweekday
+u8 epoch_time_to_week_day(double time)
+{
+    // EpochTimeToWeekDay(t) = (EpochTimeToDayNumber(t) + 4) modulo 7
+    return static_cast<u8>(modulo(epoch_time_to_day_number(time) + 4, 7.0));
+}
+
+}