LibJS: Implement a bunch of time value related Date AOs

We don't have these yet as our Date implementation doesn't use the time
value algorithms and AOs from the spec, but Temporal will need these in
various contexts.

Userland/Libraries/LibJS/Runtime/Date.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Linus Groh <linusg@serenityos.org>
+ * Copyright (c) 2020-2021, Linus Groh <linusg@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -9,7 +9,6 @@
 #include <LibJS/Heap/Heap.h>
 #include <LibJS/Runtime/Date.h>
 #include <LibJS/Runtime/GlobalObject.h>
-#include <sys/time.h>
 #include <time.h>
 
 namespace JS {
@@ -111,6 +110,12 @@ String Date::iso_date_string() const
     return builder.build();
 }
 
+// https://tc39.es/ecma262/#eqn-HoursPerDay
+static constexpr double HOURS_PER_DAY = 24;
+// https://tc39.es/ecma262/#eqn-MinutesPerHour
+static constexpr double MINUTES_PER_HOUR = 60;
+// https://tc39.es/ecma262/#eqn-SecondsPerMinute
+static constexpr double SECONDS_PER_MINUTE = 60;
 // https://tc39.es/ecma262/#eqn-msPerSecond
 static constexpr double MS_PER_SECOND = 1000;
 // https://tc39.es/ecma262/#eqn-msPerMinute
@@ -120,6 +125,171 @@ static constexpr double MS_PER_HOUR = 3600000;
 // https://tc39.es/ecma262/#eqn-msPerDay
 static constexpr double MS_PER_DAY = 86400000;
 
+// DayWithinYear(t), https://tc39.es/ecma262/#eqn-DayWithinYear
+u16 day_within_year(double t)
+{
+    // Day(t) - DayFromYear(YearFromTime(t))
+    return static_cast<u16>(day(t) - day_from_year(year_from_time(t)));
+}
+
+// DateFromTime(t), https://tc39.es/ecma262/#sec-date-number
+u8 date_from_time(double t)
+{
+    switch (month_from_time(t)) {
+    // DayWithinYear(t) + 1𝔽 if MonthFromTime(t) = +0𝔽
+    case 0:
+        return day_within_year(t) + 1;
+    // DayWithinYear(t) - 30𝔽 if MonthFromTime(t) = 1𝔽
+    case 1:
+        return day_within_year(t) - 30;
+    // DayWithinYear(t) - 58𝔽 - InLeapYear(t) if MonthFromTime(t) = 2𝔽
+    case 2:
+        return day_within_year(t) - 58 - in_leap_year(t);
+    // DayWithinYear(t) - 89𝔽 - InLeapYear(t) if MonthFromTime(t) = 3𝔽
+    case 3:
+        return day_within_year(t) - 89 - in_leap_year(t);
+    // DayWithinYear(t) - 119𝔽 - InLeapYear(t) if MonthFromTime(t) = 4𝔽
+    case 4:
+        return day_within_year(t) - 119 - in_leap_year(t);
+    // DayWithinYear(t) - 150𝔽 - InLeapYear(t) if MonthFromTime(t) = 5𝔽
+    case 5:
+        return day_within_year(t) - 150 - in_leap_year(t);
+    // DayWithinYear(t) - 180𝔽 - InLeapYear(t) if MonthFromTime(t) = 6𝔽
+    case 6:
+        return day_within_year(t) - 180 - in_leap_year(t);
+    // DayWithinYear(t) - 211𝔽 - InLeapYear(t) if MonthFromTime(t) = 7𝔽
+    case 7:
+        return day_within_year(t) - 211 - in_leap_year(t);
+    // DayWithinYear(t) - 242𝔽 - InLeapYear(t) if MonthFromTime(t) = 8𝔽
+    case 8:
+        return day_within_year(t) - 242 - in_leap_year(t);
+    // DayWithinYear(t) - 272𝔽 - InLeapYear(t) if MonthFromTime(t) = 9𝔽
+    case 9:
+        return day_within_year(t) - 272 - in_leap_year(t);
+    // DayWithinYear(t) - 303𝔽 - InLeapYear(t) if MonthFromTime(t) = 10𝔽
+    case 10:
+        return day_within_year(t) - 303 - in_leap_year(t);
+    // DayWithinYear(t) - 333𝔽 - InLeapYear(t) if MonthFromTime(t) = 11𝔽
+    case 11:
+        return day_within_year(t) - 333 - in_leap_year(t);
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+// DaysInYear(y), https://tc39.es/ecma262/#eqn-DaysInYear
+u16 days_in_year(i32 y)
+{
+    // 365𝔽 if (ℝ(y) modulo 4) ≠ 0
+    if (y % 4 != 0)
+        return 365;
+    // 366𝔽 if (ℝ(y) modulo 4) = 0 and (ℝ(y) modulo 100) ≠ 0
+    if (y % 4 == 0 && y % 100 != 0)
+        return 366;
+    // 365𝔽 if (ℝ(y) modulo 100) = 0 and (ℝ(y) modulo 400) ≠ 0
+    if (y % 100 == 0 && y % 400 != 0)
+        return 365;
+    // 366𝔽 if (ℝ(y) modulo 400) = 0
+    if (y % 400 == 0)
+        return 366;
+    VERIFY_NOT_REACHED();
+}
+
+// DayFromYear(y), https://tc39.es/ecma262/#eqn-DaysFromYear
+double day_from_year(i32 y)
+{
+    // 𝔽(365 × (ℝ(y) - 1970) + floor((ℝ(y) - 1969) / 4) - floor((ℝ(y) - 1901) / 100) + floor((ℝ(y) - 1601) / 400))
+    return 365 * (y - 1970) + floor((y - 1969) / 4.0) - floor((y - 1901) / 100.0) + floor((y - 1601) / 400.0);
+}
+
+// YearFromTime(t), https://tc39.es/ecma262/#eqn-YearFromTime
+i32 year_from_time(double t)
+{
+    // the largest integral Number y (closest to +∞) such that TimeFromYear(y) ≤ t
+    return static_cast<i32>(t / (365.0 * MS_PER_DAY) + 1970);
+}
+
+// InLeapYear(t), https://tc39.es/ecma262/#eqn-InLeapYear
+bool in_leap_year(double t)
+{
+    // +0𝔽 if DaysInYear(YearFromTime(t)) = 365𝔽
+    // 1𝔽 if DaysInYear(YearFromTime(t)) = 366𝔽
+    return days_in_year(year_from_time(t)) == 366;
+}
+
+// MonthFromTime(t), https://tc39.es/ecma262/#eqn-MonthFromTime
+u8 month_from_time(double t)
+{
+    auto in_leap_year = JS::in_leap_year(t);
+    auto day_within_year = JS::day_within_year(t);
+
+    // +0𝔽 if +0𝔽 ≤ DayWithinYear(t) < 31𝔽
+    if (day_within_year < 31)
+        return 0;
+    // 1𝔽 if 31𝔽 ≤ DayWithinYear(t) < 59𝔽 + InLeapYear(t)
+    if (31 <= day_within_year && day_within_year < 59 + in_leap_year)
+        return 1;
+    // 2𝔽 if 59𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 90𝔽 + InLeapYear(t)
+    if (59 + in_leap_year <= day_within_year && day_within_year < 90 + in_leap_year)
+        return 2;
+    // 3𝔽 if 90𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 120𝔽 + InLeapYear(t)
+    if (90 + in_leap_year <= day_within_year && day_within_year < 120 + in_leap_year)
+        return 3;
+    // 4𝔽 if 120𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 151𝔽 + InLeapYear(t)
+    if (120 + in_leap_year <= day_within_year && day_within_year < 151 + in_leap_year)
+        return 4;
+    // 5𝔽 if 151𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 181𝔽 + InLeapYear(t)
+    if (151 + in_leap_year <= day_within_year && day_within_year < 181 + in_leap_year)
+        return 5;
+    // 6𝔽 if 181𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 212𝔽 + InLeapYear(t)
+    if (181 + in_leap_year <= day_within_year && day_within_year < 212 + in_leap_year)
+        return 6;
+    // 7𝔽 if 212𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 243𝔽 + InLeapYear(t)
+    if (212 + in_leap_year <= day_within_year && day_within_year < 243 + in_leap_year)
+        return 7;
+    // 8𝔽 if 243𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 273𝔽 + InLeapYear(t)
+    if (243 + in_leap_year <= day_within_year && day_within_year < 273 + in_leap_year)
+        return 8;
+    // 9𝔽 if 273𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 304𝔽 + InLeapYear(t)
+    if (273 + in_leap_year <= day_within_year && day_within_year < 304 + in_leap_year)
+        return 9;
+    // 10𝔽 if 304𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 334𝔽 + InLeapYear(t)
+    if (304 + in_leap_year <= day_within_year && day_within_year < 334 + in_leap_year)
+        return 10;
+    // 11𝔽 if 334𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 365𝔽 + InLeapYear(t)
+    if (334 + in_leap_year <= day_within_year && day_within_year < 365 + in_leap_year)
+        return 11;
+    VERIFY_NOT_REACHED();
+}
+
+// HourFromTime(t), https://tc39.es/ecma262/#eqn-HourFromTime
+u8 hour_from_time(double t)
+{
+    // 𝔽(floor(ℝ(t / msPerHour)) modulo HoursPerDay)
+    return static_cast<u8>(fmod(floor(t / MS_PER_HOUR), HOURS_PER_DAY));
+}
+
+// MinFromTime(t), https://tc39.es/ecma262/#eqn-MinFromTime
+u8 min_from_time(double t)
+{
+    // 𝔽(floor(ℝ(t / msPerMinute)) modulo MinutesPerHour)
+    return static_cast<u8>(fmod(floor(t / MS_PER_MINUTE), MINUTES_PER_HOUR));
+}
+
+// SecFromTime(t), https://tc39.es/ecma262/#eqn-SecFromTime
+u8 sec_from_time(double t)
+{
+    // 𝔽(floor(ℝ(t / msPerSecond)) modulo SecondsPerMinute)
+    return static_cast<u8>(fmod(t / MS_PER_SECOND, SECONDS_PER_MINUTE));
+}
+
+// msFromTime(t), https://tc39.es/ecma262/#eqn-msFromTime
+u16 ms_from_time(double t)
+{
+    // 𝔽(ℝ(t) modulo msPerSecond)
+    return static_cast<u16>(fmod(t, MS_PER_SECOND));
+}
+
 // 21.4.1.11 MakeTime ( hour, min, sec, ms ), https://tc39.es/ecma262/#sec-maketime
 Value make_time(GlobalObject& global_object, Value hour, Value min, Value sec, Value ms)
 {
@@ -142,8 +312,8 @@ Value make_time(GlobalObject& global_object, Value hour, Value min, Value sec, V
     return Value(t);
 }
 
-// https://tc39.es/ecma262/#eqn-Day
-static inline double day(double time_value)
+// Day(t), https://tc39.es/ecma262/#eqn-Day
+double day(double time_value)
 {
     return floor(time_value / MS_PER_DAY);
 }

Userland/Libraries/LibJS/Runtime/Date.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Linus Groh <linusg@serenityos.org>
+ * Copyright (c) 2020-2021, Linus Groh <linusg@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -86,6 +86,18 @@ private:
     bool m_is_invalid { false };
 };
 
+u16 day_within_year(double);
+u8 date_from_time(double);
+u16 days_in_year(i32);
+double day_from_year(i32);
+i32 year_from_time(double);
+bool in_leap_year(double);
+u8 month_from_time(double);
+u8 hour_from_time(double);
+u8 min_from_time(double);
+u8 sec_from_time(double);
+u16 ms_from_time(double);
+double day(double);
 Value make_time(GlobalObject& global_object, Value hour, Value min, Value sec, Value ms);
 Value make_day(GlobalObject& global_object, Value year, Value month, Value date);
 Value make_date(Value day, Value time);