/*

 * Copyright (c) 2020-2023, Linus Groh <linusg@serenityos.org>

 * Copyright (c) 2022-2023, Tim Flynn <trflynn89@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <AK/NumericLimits.h>

#include <AK/StringBuilder.h>

#include <AK/Time.h>

#include <LibJS/Runtime/AbstractOperations.h>

#include <LibJS/Runtime/Date.h>

#include <LibJS/Runtime/GlobalObject.h>

#include <LibJS/Runtime/Temporal/ISO8601.h>

#include <LibTimeZone/TimeZone.h>

#include <time.h>

namespace JS {

JS_DEFINE_ALLOCATOR(Date);

static Crypto::SignedBigInteger const s_one_billion_bigint { 1'000'000'000 };

static Crypto::SignedBigInteger const s_one_million_bigint { 1'000'000 };

static Crypto::SignedBigInteger const s_one_thousand_bigint { 1'000 };

Crypto::SignedBigInteger const ns_per_day_bigint { static_cast<i64>(ns_per_day) };

NonnullGCPtr<Date> Date::create(Realm& realm, double date_value)

{

    return realm.heap().allocate<Date>(realm, date_value, realm.intrinsics().date_prototype());

}

Date::Date(double date_value, Object& prototype)

    : Object(ConstructWithPrototypeTag::Tag, prototype)

    , m_date_value(date_value)

{

}

Date::~Date() = default;

ErrorOr<String> Date::iso_date_string() const

{

    int year = year_from_time(m_date_value);

    StringBuilder builder;

    if (year < 0)

        builder.appendff("-{:06}", -year);

    else if (year > 9999)

        builder.appendff("+{:06}", year);

    else

        builder.appendff("{:04}", year);

    builder.append('-');

    builder.appendff("{:02}", month_from_time(m_date_value) + 1);

    builder.append('-');

    builder.appendff("{:02}", date_from_time(m_date_value));

    builder.append('T');

    builder.appendff("{:02}", hour_from_time(m_date_value));

    builder.append(':');

    builder.appendff("{:02}", min_from_time(m_date_value));

    builder.append(':');

    builder.appendff("{:02}", sec_from_time(m_date_value));

    builder.append('.');

    builder.appendff("{:03}", ms_from_time(m_date_value));

    builder.append('Z');

    return builder.to_string();

}

// 21.4.1.3 Day ( t ), https://tc39.es/ecma262/#sec-day

double day(double time_value)

{

    // 1. Return 𝔽(floor(ℝ(t / msPerDay))).

    return floor(time_value / ms_per_day);

}

// 21.4.1.4 TimeWithinDay ( t ), https://tc39.es/ecma262/#sec-timewithinday

double time_within_day(double time)

{

    // 1. Return 𝔽(ℝ(t) modulo ℝ(msPerDay)).

    return modulo(time, ms_per_day);

}

// 21.4.1.5 DaysInYear ( y ), https://tc39.es/ecma262/#sec-daysinyear

u16 days_in_year(i32 y)

{

    // 1. Let ry be ℝ(y).

    auto ry = static_cast<double>(y);

    // 2. If (ry modulo 400) = 0, return 366𝔽.

    if (modulo(ry, 400.0) == 0)

        return 366;

    // 3. If (ry modulo 100) = 0, return 365𝔽.

    if (modulo(ry, 100.0) == 0)

        return 365;

    // 4. If (ry modulo 4) = 0, return 366𝔽.

    if (modulo(ry, 4.0) == 0)

        return 366;

    // 5. Return 365𝔽.

    return 365;

}

// 21.4.1.6 DayFromYear ( y ), https://tc39.es/ecma262/#sec-dayfromyear

double day_from_year(i32 y)

{

    // 1. Let ry be ℝ(y).

    auto ry = static_cast<double>(y);

    // 2. NOTE: In the following steps, each _numYearsN_ is the number of years divisible by N that occur between the

    //    epoch and the start of year y. (The number is negative if y is before the epoch.)

    // 3. Let numYears1 be (ry - 1970).

    auto num_years_1 = ry - 1970;

    // 4. Let numYears4 be floor((ry - 1969) / 4).

    auto num_years_4 = floor((ry - 1969) / 4.0);

    // 5. Let numYears100 be floor((ry - 1901) / 100).

    auto num_years_100 = floor((ry - 1901) / 100.0);

    // 6. Let numYears400 be floor((ry - 1601) / 400).

    auto num_years_400 = floor((ry - 1601) / 400.0);

    // 7. Return 𝔽(365 × numYears1 + numYears4 - numYears100 + numYears400).

    return 365.0 * num_years_1 + num_years_4 - num_years_100 + num_years_400;

}

// 21.4.1.7 TimeFromYear ( y ), https://tc39.es/ecma262/#sec-timefromyear

double time_from_year(i32 y)

{

    // 1. Return msPerDay × DayFromYear(y).

    return ms_per_day * day_from_year(y);

}

// 21.4.1.8 YearFromTime ( t ), https://tc39.es/ecma262/#sec-yearfromtime

i32 year_from_time(double t)

{

    // 1. Return the largest integral Number y (closest to +∞) such that TimeFromYear(y) ≤ t.

    if (!Value(t).is_finite_number())

        return NumericLimits<i32>::max();

    // Approximation using average number of milliseconds per year. We might have to adjust this guess afterwards.

    auto year = static_cast<i32>(floor(t / (365.2425 * ms_per_day) + 1970));

    auto year_t = time_from_year(year);

    if (year_t > t)

        year--;

    else if (year_t + days_in_year(year) * ms_per_day <= t)

        year++;

    return year;

}

// 21.4.1.9 DayWithinYear ( t ), https://tc39.es/ecma262/#sec-daywithinyear

u16 day_within_year(double t)

{

    if (!Value(t).is_finite_number())

        return 0;

    // 1. Return Day(t) - DayFromYear(YearFromTime(t)).

    return static_cast<u16>(day(t) - day_from_year(year_from_time(t)));

}

// 21.4.1.10 InLeapYear ( t ), https://tc39.es/ecma262/#sec-inleapyear

bool in_leap_year(double t)

{

    // 1. If DaysInYear(YearFromTime(t)) is 366𝔽, return 1𝔽; else return +0𝔽.

    return days_in_year(year_from_time(t)) == 366;

}

// 21.4.1.11 MonthFromTime ( t ), https://tc39.es/ecma262/#sec-monthfromtime

u8 month_from_time(double t)

{

    // 1. Let inLeapYear be InLeapYear(t).

    auto in_leap_year = static_cast<unsigned>(JS::in_leap_year(t));

    // 2. Let dayWithinYear be DayWithinYear(t).

    auto day_within_year = JS::day_within_year(t);

    // 3. If dayWithinYear < 31𝔽, return +0𝔽.

    if (day_within_year < 31)

        return 0;

    // 4. If dayWithinYear < 59𝔽 + inLeapYear, return 1𝔽.

    if (day_within_year < (59 + in_leap_year))

        return 1;

    // 5. If dayWithinYear < 90𝔽 + inLeapYear, return 2𝔽.

    if (day_within_year < (90 + in_leap_year))

        return 2;

    // 6. If dayWithinYear < 120𝔽 + inLeapYear, return 3𝔽.

    if (day_within_year < (120 + in_leap_year))

        return 3;

    // 7. If dayWithinYear < 151𝔽 + inLeapYear, return 4𝔽.

    if (day_within_year < (151 + in_leap_year))

        return 4;

    // 8. If dayWithinYear < 181𝔽 + inLeapYear, return 5𝔽.

    if (day_within_year < (181 + in_leap_year))

        return 5;

    // 9. If dayWithinYear < 212𝔽 + inLeapYear, return 6𝔽.

    if (day_within_year < (212 + in_leap_year))

        return 6;

    // 10. If dayWithinYear < 243𝔽 + inLeapYear, return 7𝔽.

    if (day_within_year < (243 + in_leap_year))

        return 7;

    // 11. If dayWithinYear < 273𝔽 + inLeapYear, return 8𝔽.

    if (day_within_year < (273 + in_leap_year))

        return 8;

    // 12. If dayWithinYear < 304𝔽 + inLeapYear, return 9𝔽.

    if (day_within_year < (304 + in_leap_year))

        return 9;

    // 13. If dayWithinYear < 334𝔽 + inLeapYear, return 10𝔽.

    if (day_within_year < (334 + in_leap_year))

        return 10;

    // 14. Assert: dayWithinYear < 365𝔽 + inLeapYear.

    VERIFY(day_within_year < (365 + in_leap_year));

    // 15. Return 11𝔽.

    return 11;

}

// 21.4.1.12 DateFromTime ( t ), https://tc39.es/ecma262/#sec-datefromtime

u8 date_from_time(double t)

{

    // 1. Let inLeapYear be InLeapYear(t).

    auto in_leap_year = static_cast<unsigned>(JS::in_leap_year(t));

    // 2. Let dayWithinYear be DayWithinYear(t).

    auto day_within_year = JS::day_within_year(t);

    // 3. Let month be MonthFromTime(t).

    auto month = month_from_time(t);

    // 4. If month is +0𝔽, return dayWithinYear + 1𝔽.

    if (month == 0)

        return day_within_year + 1;

    // 5. If month is 1𝔽, return dayWithinYear - 30𝔽.

    if (month == 1)

        return day_within_year - 30;

    // 6. If month is 2𝔽, return dayWithinYear - 58𝔽 - inLeapYear.

    if (month == 2)

        return day_within_year - 58 - in_leap_year;

    // 7. If month is 3𝔽, return dayWithinYear - 89𝔽 - inLeapYear.

    if (month == 3)

        return day_within_year - 89 - in_leap_year;

    // 8. If month is 4𝔽, return dayWithinYear - 119𝔽 - inLeapYear.

    if (month == 4)

        return day_within_year - 119 - in_leap_year;

    // 9. If month is 5𝔽, return dayWithinYear - 150𝔽 - inLeapYear.

    if (month == 5)

        return day_within_year - 150 - in_leap_year;

    // 10. If month is 6𝔽, return dayWithinYear - 180𝔽 - inLeapYear.

    if (month == 6)

        return day_within_year - 180 - in_leap_year;

    // 11. If month is 7𝔽, return dayWithinYear - 211𝔽 - inLeapYear.

    if (month == 7)

        return day_within_year - 211 - in_leap_year;

    // 12. If month is 8𝔽, return dayWithinYear - 242𝔽 - inLeapYear.

    if (month == 8)

        return day_within_year - 242 - in_leap_year;

    // 13. If month is 9𝔽, return dayWithinYear - 272𝔽 - inLeapYear.

    if (month == 9)

        return day_within_year - 272 - in_leap_year;

    // 14. If month is 10𝔽, return dayWithinYear - 303𝔽 - inLeapYear.

    if (month == 10)

        return day_within_year - 303 - in_leap_year;

    // 15. Assert: month is 11𝔽.

    VERIFY(month == 11);

    // 16. Return dayWithinYear - 333𝔽 - inLeapYear.

    return day_within_year - 333 - in_leap_year;

}

// 21.4.1.13 WeekDay ( t ), https://tc39.es/ecma262/#sec-weekday

u8 week_day(double t)

{

    if (!Value(t).is_finite_number())

        return 0;

    // 1. Return 𝔽(ℝ(Day(t) + 4𝔽) modulo 7).

    return static_cast<u8>(modulo(day(t) + 4, 7));

}

// 21.4.1.14 HourFromTime ( t ), https://tc39.es/ecma262/#sec-hourfromtime

u8 hour_from_time(double t)

{

    if (!Value(t).is_finite_number())

        return 0;

    // 1. Return 𝔽(floor(ℝ(t / msPerHour)) modulo HoursPerDay).

    return static_cast<u8>(modulo(floor(t / ms_per_hour), hours_per_day));

}

// 21.4.1.15 MinFromTime ( t ), https://tc39.es/ecma262/#sec-minfromtime

u8 min_from_time(double t)

{

    if (!Value(t).is_finite_number())

        return 0;

    // 1. Return 𝔽(floor(ℝ(t / msPerMinute)) modulo MinutesPerHour).

    return static_cast<u8>(modulo(floor(t / ms_per_minute), minutes_per_hour));

}

// 21.4.1.16 SecFromTime ( t ), https://tc39.es/ecma262/#sec-secfromtime

u8 sec_from_time(double t)

{

    if (!Value(t).is_finite_number())

        return 0;

    // 1. Return 𝔽(floor(ℝ(t / msPerSecond)) modulo SecondsPerMinute).

    return static_cast<u8>(modulo(floor(t / ms_per_second), seconds_per_minute));

}

// 21.4.1.17 msFromTime ( t ), https://tc39.es/ecma262/#sec-msfromtime

u16 ms_from_time(double t)

{

    if (!Value(t).is_finite_number())

        return 0;

    // 1. Return 𝔽(ℝ(t) modulo ℝ(msPerSecond)).

    return static_cast<u16>(modulo(t, ms_per_second));

}

// 21.4.1.18 GetUTCEpochNanoseconds ( year, month, day, hour, minute, second, millisecond, microsecond, nanosecond ), https://tc39.es/ecma262/#sec-getutcepochnanoseconds

Crypto::SignedBigInteger get_utc_epoch_nanoseconds(i32 year, u8 month, u8 day, u8 hour, u8 minute, u8 second, u16 millisecond, u16 microsecond, u16 nanosecond)

{

    // 1. Let date be MakeDay(𝔽(year), 𝔽(month - 1), 𝔽(day)).

    auto date = make_day(year, month - 1, day);

    // 2. Let time be MakeTime(𝔽(hour), 𝔽(minute), 𝔽(second), 𝔽(millisecond)).

    auto time = make_time(hour, minute, second, millisecond);

    // 3. Let ms be MakeDate(date, time).

    auto ms = make_date(date, time);

    // 4. Assert: ms is an integral Number.

    VERIFY(ms == trunc(ms));

    // 5. Return ℤ(ℝ(ms) × 10^6 + microsecond × 10^3 + nanosecond).

    auto result = Crypto::SignedBigInteger { ms }.multiplied_by(s_one_million_bigint);

    result = result.plus(Crypto::SignedBigInteger { static_cast<i32>(microsecond) }.multiplied_by(s_one_thousand_bigint));

    result = result.plus(Crypto::SignedBigInteger { static_cast<i32>(nanosecond) });

    return result;

}

static i64 clip_bigint_to_sane_time(Crypto::SignedBigInteger const& value)

{

    static Crypto::SignedBigInteger const min_bigint { NumericLimits<i64>::min() };

    static Crypto::SignedBigInteger const max_bigint { NumericLimits<i64>::max() };

    // The provided epoch (nano)seconds value is potentially out of range for AK::Duration and subsequently

    // get_time_zone_offset(). We can safely assume that the TZDB has no useful information that far

    // into the past and future anyway, so clamp it to the i64 range.

    if (value < min_bigint)

        return NumericLimits<i64>::min();

    if (value > max_bigint)

        return NumericLimits<i64>::max();

    // FIXME: Can we do this without string conversion?

    return value.to_base_deprecated(10).to_number<i64>().value();

}

// 21.4.1.20 GetNamedTimeZoneEpochNanoseconds ( timeZoneIdentifier, year, month, day, hour, minute, second, millisecond, microsecond, nanosecond ), https://tc39.es/ecma262/#sec-getnamedtimezoneepochnanoseconds

Vector<Crypto::SignedBigInteger> get_named_time_zone_epoch_nanoseconds(StringView time_zone_identifier, i32 year, u8 month, u8 day, u8 hour, u8 minute, u8 second, u16 millisecond, u16 microsecond, u16 nanosecond)

{

    auto local_nanoseconds = get_utc_epoch_nanoseconds(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond);

    auto local_time = UnixDateTime::from_nanoseconds_since_epoch(clip_bigint_to_sane_time(local_nanoseconds));

    // FIXME: LibTimeZone does not behave exactly as the spec expects. It does not consider repeated or skipped time points.

    auto offset = TimeZone::get_time_zone_offset(time_zone_identifier, local_time);

    // Can only fail if the time zone identifier is invalid, which cannot be the case here.

    VERIFY(offset.has_value());

    return { local_nanoseconds.minus(Crypto::SignedBigInteger { offset->seconds }.multiplied_by(s_one_billion_bigint)) };

}

// 21.4.1.21 GetNamedTimeZoneOffsetNanoseconds ( timeZoneIdentifier, epochNanoseconds ), https://tc39.es/ecma262/#sec-getnamedtimezoneoffsetnanoseconds

i64 get_named_time_zone_offset_nanoseconds(StringView time_zone_identifier, Crypto::SignedBigInteger const& epoch_nanoseconds)

{

    // Only called with validated time zone identifier as argument.

    auto time_zone = TimeZone::time_zone_from_string(time_zone_identifier);

    VERIFY(time_zone.has_value());

    // Since UnixDateTime::from_seconds_since_epoch() and UnixDateTime::from_nanoseconds_since_epoch() both take an i64, converting to

    // seconds first gives us a greater range. The TZDB doesn't have sub-second offsets.

    auto seconds = epoch_nanoseconds.divided_by(s_one_billion_bigint).quotient;

    auto time = UnixDateTime::from_seconds_since_epoch(clip_bigint_to_sane_time(seconds));

    auto offset = TimeZone::get_time_zone_offset(*time_zone, time);

    VERIFY(offset.has_value());

    return offset->seconds * 1'000'000'000;

}

// 21.4.1.23 AvailableNamedTimeZoneIdentifiers ( ), https://tc39.es/ecma262/#sec-time-zone-identifier-record

Vector<TimeZoneIdentifier> available_named_time_zone_identifiers()

{

    // 1. If the implementation does not include local political rules for any time zones, then

    //     a. Return « the Time Zone Identifier Record { [[Identifier]]: "UTC", [[PrimaryIdentifier]]: "UTC" } ».

    // NOTE: This step is not applicable as LibTimeZone will always return at least UTC, even if the TZDB is disabled.

    // 2. Let identifiers be the List of unique available named time zone identifiers.

    auto identifiers = TimeZone::all_time_zones();

    // 3. Sort identifiers into the same order as if an Array of the same values had been sorted using %Array.prototype.sort% with undefined as comparefn.

    // NOTE: LibTimeZone provides the identifiers already sorted.

    // 4. Let result be a new empty List.

    Vector<TimeZoneIdentifier> result;

    result.ensure_capacity(identifiers.size());

    bool found_utc = false;

    // 5. For each element identifier of identifiers, do

    for (auto identifier : identifiers) {

        // a. Let primary be identifier.

        auto primary = identifier.name;

        // b. If identifier is a non-primary time zone identifier in this implementation and identifier is not "UTC", then

        if (identifier.is_link == TimeZone::IsLink::Yes && identifier.name != "UTC"sv) {

            // i. Set primary to the primary time zone identifier associated with identifier.

            // ii. NOTE: An implementation may need to resolve identifier iteratively to obtain the primary time zone identifier.

            primary = TimeZone::canonicalize_time_zone(identifier.name).value();

        }

        // c. Let record be the Time Zone Identifier Record { [[Identifier]]: identifier, [[PrimaryIdentifier]]: primary }.

        TimeZoneIdentifier record { .identifier = identifier.name, .primary_identifier = primary };

        // d. Append record to result.

        result.unchecked_append(record);

        if (!found_utc && identifier.name == "UTC"sv && primary == "UTC"sv)

            found_utc = true;

    }

    // 6. Assert: result contains a Time Zone Identifier Record r such that r.[[Identifier]] is "UTC" and r.[[PrimaryIdentifier]] is "UTC".

    VERIFY(found_utc);

    // 7. Return result.

    return result;

}

// 21.4.1.24 SystemTimeZoneIdentifier ( ), https://tc39.es/ecma262/#sec-systemtimezoneidentifier

StringView system_time_zone_identifier()

{

    return TimeZone::current_time_zone();

}

// 21.4.1.25 LocalTime ( t ), https://tc39.es/ecma262/#sec-localtime

double local_time(double time)

{

    // 1. Let systemTimeZoneIdentifier be SystemTimeZoneIdentifier().

    auto system_time_zone_identifier = JS::system_time_zone_identifier();

    double offset_nanoseconds { 0 };

    // 2. If IsTimeZoneOffsetString(systemTimeZoneIdentifier) is true, then

    if (is_time_zone_offset_string(system_time_zone_identifier)) {

        // a. Let offsetNs be ParseTimeZoneOffsetString(systemTimeZoneIdentifier).

        offset_nanoseconds = parse_time_zone_offset_string(system_time_zone_identifier);

    }

    // 3. Else,

    else {

        // a. Let offsetNs be GetNamedTimeZoneOffsetNanoseconds(systemTimeZoneIdentifier, ℤ(ℝ(t) × 10^6)).

        auto time_bigint = Crypto::SignedBigInteger { time }.multiplied_by(s_one_million_bigint);

        offset_nanoseconds = get_named_time_zone_offset_nanoseconds(system_time_zone_identifier, time_bigint);

    }

    // 4. Let offsetMs be truncate(offsetNs / 10^6).

    auto offset_milliseconds = trunc(offset_nanoseconds / 1e6);

    // 5. Return t + 𝔽(offsetMs).

    return time + offset_milliseconds;

}

// 21.4.1.26 UTC ( t ), https://tc39.es/ecma262/#sec-utc-t

double utc_time(double time)

{

    // 1. Let systemTimeZoneIdentifier be SystemTimeZoneIdentifier().

    auto system_time_zone_identifier = JS::system_time_zone_identifier();

    double offset_nanoseconds { 0 };

    // 2. If IsTimeZoneOffsetString(systemTimeZoneIdentifier) is true, then

    if (is_time_zone_offset_string(system_time_zone_identifier)) {

        // a. Let offsetNs be ParseTimeZoneOffsetString(systemTimeZoneIdentifier).

        offset_nanoseconds = parse_time_zone_offset_string(system_time_zone_identifier);

    }

    // 3. Else,

    else {

        // a. Let possibleInstants be GetNamedTimeZoneEpochNanoseconds(systemTimeZoneIdentifier, ℝ(YearFromTime(t)), ℝ(MonthFromTime(t)) + 1, ℝ(DateFromTime(t)), ℝ(HourFromTime(t)), ℝ(MinFromTime(t)), ℝ(SecFromTime(t)), ℝ(msFromTime(t)), 0, 0).

        auto possible_instants = get_named_time_zone_epoch_nanoseconds(system_time_zone_identifier, year_from_time(time), month_from_time(time) + 1, date_from_time(time), hour_from_time(time), min_from_time(time), sec_from_time(time), ms_from_time(time), 0, 0);

        // b. NOTE: The following steps ensure that when t represents local time repeating multiple times at a negative time zone transition (e.g. when the daylight saving time ends or the time zone offset is decreased due to a time zone rule change) or skipped local time at a positive time zone transition (e.g. when the daylight saving time starts or the time zone offset is increased due to a time zone rule change), t is interpreted using the time zone offset before the transition.

        Crypto::SignedBigInteger disambiguated_instant;

        // c. If possibleInstants is not empty, then

        if (!possible_instants.is_empty()) {

            // i. Let disambiguatedInstant be possibleInstants[0].

            disambiguated_instant = move(possible_instants.first());

        }

        // d. Else,

        else {

            // i. NOTE: t represents a local time skipped at a positive time zone transition (e.g. due to daylight saving time starting or a time zone rule change increasing the UTC offset).

            // ii. Let possibleInstantsBefore be GetNamedTimeZoneEpochNanoseconds(systemTimeZoneIdentifier, ℝ(YearFromTime(tBefore)), ℝ(MonthFromTime(tBefore)) + 1, ℝ(DateFromTime(tBefore)), ℝ(HourFromTime(tBefore)), ℝ(MinFromTime(tBefore)), ℝ(SecFromTime(tBefore)), ℝ(msFromTime(tBefore)), 0, 0), where tBefore is the largest integral Number < t for which possibleInstantsBefore is not empty (i.e., tBefore represents the last local time before the transition).

            // iii. Let disambiguatedInstant be the last element of possibleInstantsBefore.

            // FIXME: This branch currently cannot be reached with our implementation, because LibTimeZone does not handle skipped time points.

            //        When GetNamedTimeZoneEpochNanoseconds is updated to use a LibTimeZone API which does handle them, implement these steps.

            VERIFY_NOT_REACHED();

        }

        // e. Let offsetNs be GetNamedTimeZoneOffsetNanoseconds(systemTimeZoneIdentifier, disambiguatedInstant).

        offset_nanoseconds = get_named_time_zone_offset_nanoseconds(system_time_zone_identifier, disambiguated_instant);

    }

    // 4. Let offsetMs be truncate(offsetNs / 10^6).

    auto offset_milliseconds = trunc(offset_nanoseconds / 1e6);

    // 5. Return t - 𝔽(offsetMs).

    return time - offset_milliseconds;

}

// 21.4.1.27 MakeTime ( hour, min, sec, ms ), https://tc39.es/ecma262/#sec-maketime

double make_time(double hour, double min, double sec, double ms)

{

    // 1. If hour is not finite or min is not finite or sec is not finite or ms is not finite, return NaN.

    if (!isfinite(hour) || !isfinite(min) || !isfinite(sec) || !isfinite(ms))

        return NAN;

    // 2. Let h be 𝔽(! ToIntegerOrInfinity(hour)).

    auto h = to_integer_or_infinity(hour);

    // 3. Let m be 𝔽(! ToIntegerOrInfinity(min)).

    auto m = to_integer_or_infinity(min);

    // 4. Let s be 𝔽(! ToIntegerOrInfinity(sec)).

    auto s = to_integer_or_infinity(sec);

    // 5. Let milli be 𝔽(! ToIntegerOrInfinity(ms)).

    auto milli = to_integer_or_infinity(ms);

    // 6. Let t be ((h * msPerHour + m * msPerMinute) + s * msPerSecond) + milli, performing the arithmetic according to IEEE 754-2019 rules (that is, as if using the ECMAScript operators * and +).

    // NOTE: C++ arithmetic abides by IEEE 754 rules

    auto t = ((h * ms_per_hour + m * ms_per_minute) + s * ms_per_second) + milli;

    // 7. Return t.

    return t;

}

// 21.4.1.28 MakeDay ( year, month, date ), https://tc39.es/ecma262/#sec-makeday

double make_day(double year, double month, double date)

{

    // 1. If year is not finite or month is not finite or date is not finite, return NaN.

    if (!isfinite(year) || !isfinite(month) || !isfinite(date))

        return NAN;

    // 2. Let y be 𝔽(! ToIntegerOrInfinity(year)).

    auto y = to_integer_or_infinity(year);

    // 3. Let m be 𝔽(! ToIntegerOrInfinity(month)).

    auto m = to_integer_or_infinity(month);

    // 4. Let dt be 𝔽(! ToIntegerOrInfinity(date)).

    auto dt = to_integer_or_infinity(date);

    // 5. Let ym be y + 𝔽(floor(ℝ(m) / 12)).

    auto ym = y + floor(m / 12);

    // 6. If ym is not finite, return NaN.

    if (!isfinite(ym))

        return NAN;

    // 7. Let mn be 𝔽(ℝ(m) modulo 12).

    auto mn = modulo(m, 12);

    // 8. Find a finite time value t such that YearFromTime(t) is ym and MonthFromTime(t) is mn and DateFromTime(t) is 1𝔽; but if this is not possible (because some argument is out of range), return NaN.

    if (!AK::is_within_range<int>(ym) || !AK::is_within_range<int>(mn + 1))

        return NAN;

    auto t = days_since_epoch(static_cast<int>(ym), static_cast<int>(mn) + 1, 1) * ms_per_day;

    // 9. Return Day(t) + dt - 1𝔽.

    return day(static_cast<double>(t)) + dt - 1;

}

// 21.4.1.29 MakeDate ( day, time ), https://tc39.es/ecma262/#sec-makedate

double make_date(double day, double time)

{

    // 1. If day is not finite or time is not finite, return NaN.

    if (!isfinite(day) || !isfinite(time))

        return NAN;

    // 2. Let tv be day × msPerDay + time.

    auto tv = day * ms_per_day + time;

    // 3. If tv is not finite, return NaN.

    if (!isfinite(tv))

        return NAN;

    // 4. Return tv.

    return tv;

}

// 21.4.1.31 TimeClip ( time ), https://tc39.es/ecma262/#sec-timeclip

double time_clip(double time)

{

    // 1. If time is not finite, return NaN.

    if (!isfinite(time))

        return NAN;

    // 2. If abs(ℝ(time)) > 8.64 × 10^15, return NaN.

    if (fabs(time) > 8.64E15)

        return NAN;

    // 3. Return 𝔽(! ToIntegerOrInfinity(time)).

    return to_integer_or_infinity(time);

}

// 21.4.1.33.1 IsTimeZoneOffsetString ( offsetString ), https://tc39.es/ecma262/#sec-istimezoneoffsetstring

bool is_time_zone_offset_string(StringView offset_string)

{

    // 1. Let parseResult be ParseText(StringToCodePoints(offsetString), UTCOffset).

    auto parse_result = Temporal::parse_iso8601(Temporal::Production::TimeZoneNumericUTCOffset, offset_string);

    // 2. If parseResult is a List of errors, return false.

    // 3. Return true.

    return parse_result.has_value();

}

// 21.4.1.33.2 ParseTimeZoneOffsetString ( offsetString ), https://tc39.es/ecma262/#sec-parsetimezoneoffsetstring

double parse_time_zone_offset_string(StringView offset_string)

{

    // 1. Let parseResult be ParseText(StringToCodePoints(offsetString), UTCOffset).

    auto parse_result = Temporal::parse_iso8601(Temporal::Production::TimeZoneNumericUTCOffset, offset_string);

    // 2. Assert: parseResult is not a List of errors.

    VERIFY(parse_result.has_value());

    // 3. Assert: parseResult contains a TemporalSign Parse Node.

    VERIFY(parse_result->time_zone_utc_offset_sign.has_value());

    // 4. Let parsedSign be the source text matched by the TemporalSign Parse Node contained within parseResult.

    auto parsed_sign = *parse_result->time_zone_utc_offset_sign;

    i8 sign { 0 };

    // 5. If parsedSign is the single code point U+002D (HYPHEN-MINUS) or U+2212 (MINUS SIGN), then

    if (parsed_sign.is_one_of("-"sv, "\xE2\x88\x92"sv)) {

        // a. Let sign be -1.

        sign = -1;

    }

    // 6. Else,

    else {

        // a. Let sign be 1.

        sign = 1;

    }

    // 7. NOTE: Applications of StringToNumber below do not lose precision, since each of the parsed values is guaranteed to be a sufficiently short string of decimal digits.

    // 8. Assert: parseResult contains an Hour Parse Node.

    VERIFY(parse_result->time_zone_utc_offset_hour.has_value());

    // 9. Let parsedHours be the source text matched by the Hour Parse Node contained within parseResult.

    auto parsed_hours = *parse_result->time_zone_utc_offset_hour;

    // 10. Let hours be ℝ(StringToNumber(CodePointsToString(parsedHours))).

    auto hours = string_to_number(parsed_hours);

    double minutes { 0 };

    double seconds { 0 };

    double nanoseconds { 0 };

    // 11. If parseResult does not contain a MinuteSecond Parse Node, then

    if (!parse_result->time_zone_utc_offset_minute.has_value()) {

        // a. Let minutes be 0.

        minutes = 0;

    }

    // 12. Else,

    else {

        // a. Let parsedMinutes be the source text matched by the first MinuteSecond Parse Node contained within parseResult.

        auto parsed_minutes = *parse_result->time_zone_utc_offset_minute;

        // b. Let minutes be ℝ(StringToNumber(CodePointsToString(parsedMinutes))).

        minutes = string_to_number(parsed_minutes);

    }

    // 13. If parseResult does not contain two MinuteSecond Parse Nodes, then

    if (!parse_result->time_zone_utc_offset_second.has_value()) {

        // a. Let seconds be 0.

        seconds = 0;

    }

    // 14. Else,

    else {

        // a. Let parsedSeconds be the source text matched by the second secondSecond Parse Node contained within parseResult.

        auto parsed_seconds = *parse_result->time_zone_utc_offset_second;

        // b. Let seconds be ℝ(StringToNumber(CodePointsToString(parsedSeconds))).

        seconds = string_to_number(parsed_seconds);

    }

    // 15. If parseResult does not contain a TemporalDecimalFraction Parse Node, then

    if (!parse_result->time_zone_utc_offset_fraction.has_value()) {

        // a. Let nanoseconds be 0.

        nanoseconds = 0;

    }

    // 16. Else,

    else {

        // a. Let parsedFraction be the source text matched by the TemporalDecimalFraction Parse Node contained within parseResult.

        auto parsed_fraction = *parse_result->time_zone_utc_offset_fraction;

        // b. Let fraction be the string-concatenation of CodePointsToString(parsedFraction) and "000000000".

        auto fraction = ByteString::formatted("{}000000000", parsed_fraction);

        // c. Let nanosecondsString be the substring of fraction from 1 to 10.

        auto nanoseconds_string = fraction.substring_view(1, 9);

        // d. Let nanoseconds be ℝ(StringToNumber(nanosecondsString)).

        nanoseconds = string_to_number(nanoseconds_string);

    }

    // 17. Return sign × (((hours × 60 + minutes) × 60 + seconds) × 10^9 + nanoseconds).

    // NOTE: Using scientific notation (1e9) ensures the result of this expression is a double,

    //       which is important - otherwise it's all integers and the result overflows!

    return sign * (((hours * 60 + minutes) * 60 + seconds) * 1e9 + nanoseconds);

}

}