LibJS: Implement stringification Temporal.Duration prototypes

Author: https://github.com/trflynn89
Commit: 4742775262
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2431
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/shannonbooth ✅

Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp

@@ -8,10 +8,12 @@
  */
 
 #include <LibCrypto/BigFraction/BigFraction.h>
+#include <LibJS/Runtime/AbstractOperations.h>
 #include <LibJS/Runtime/PropertyKey.h>
 #include <LibJS/Runtime/Temporal/AbstractOperations.h>
 #include <LibJS/Runtime/Temporal/Duration.h>
 #include <LibJS/Runtime/Temporal/ISO8601.h>
+#include <LibJS/Runtime/Temporal/Instant.h>
 
 namespace JS::Temporal {
 
@@ -41,6 +43,227 @@ StringView temporal_unit_to_string(Unit unit)
     return temporal_units[to_underlying(unit)].singular_property_name;
 }
 
+// 13.15 GetTemporalFractionalSecondDigitsOption ( options ), https://tc39.es/proposal-temporal/#sec-temporal-gettemporalfractionalseconddigitsoption
+ThrowCompletionOr<Precision> get_temporal_fractional_second_digits_option(VM& vm, Object const& options)
+{
+    // 1. Let digitsValue be ? Get(options, "fractionalSecondDigits").
+    auto digits_value = TRY(options.get(vm.names.fractionalSecondDigits));
+
+    // 2. If digitsValue is undefined, return AUTO.
+    if (digits_value.is_undefined())
+        return Precision { Auto {} };
+
+    // 3. If digitsValue is not a Number, then
+    if (!digits_value.is_number()) {
+        // a. If ? ToString(digitsValue) is not "auto", throw a RangeError exception.
+        auto digits_value_string = TRY(digits_value.to_string(vm));
+
+        if (digits_value_string != "auto"sv)
+            return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, digits_value, vm.names.fractionalSecondDigits);
+
+        // b. Return AUTO.
+        return Precision { Auto {} };
+    }
+
+    // 4. If digitsValue is NaN, +∞𝔽, or -∞𝔽, throw a RangeError exception.
+    if (digits_value.is_nan() || digits_value.is_infinity())
+        return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, digits_value, vm.names.fractionalSecondDigits);
+
+    // 5. Let digitCount be floor(ℝ(digitsValue)).
+    auto digit_count = floor(digits_value.as_double());
+
+    // 6. If digitCount < 0 or digitCount > 9, throw a RangeError exception.
+    if (digit_count < 0 || digit_count > 9)
+        return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, digits_value, vm.names.fractionalSecondDigits);
+
+    // 7. Return digitCount.
+    return Precision { static_cast<u8>(digit_count) };
+}
+
+// 13.16 ToSecondsStringPrecisionRecord ( smallestUnit, fractionalDigitCount ), https://tc39.es/proposal-temporal/#sec-temporal-tosecondsstringprecisionrecord
+SecondsStringPrecision to_seconds_string_precision_record(UnitValue smallest_unit, Precision fractional_digit_count)
+{
+    if (auto const* unit = smallest_unit.get_pointer<Unit>()) {
+        // 1. If smallestUnit is MINUTE, then
+        if (*unit == Unit::Minute) {
+            // a. Return the Record { [[Precision]]: MINUTE, [[Unit]]: MINUTE, [[Increment]]: 1  }.
+            return { .precision = SecondsStringPrecision::Minute {}, .unit = Unit::Minute, .increment = 1 };
+        }
+
+        // 2. If smallestUnit is SECOND, then
+        if (*unit == Unit::Second) {
+            // a. Return the Record { [[Precision]]: 0, [[Unit]]: SECOND, [[Increment]]: 1  }.
+            return { .precision = 0, .unit = Unit::Second, .increment = 1 };
+        }
+
+        // 3. If smallestUnit is MILLISECOND, then
+        if (*unit == Unit::Millisecond) {
+            // a. Return the Record { [[Precision]]: 3, [[Unit]]: MILLISECOND, [[Increment]]: 1  }.
+            return { .precision = 3, .unit = Unit::Millisecond, .increment = 1 };
+        }
+
+        // 4. If smallestUnit is MICROSECOND, then
+        if (*unit == Unit::Microsecond) {
+            // a. Return the Record { [[Precision]]: 6, [[Unit]]: MICROSECOND, [[Increment]]: 1  }.
+            return { .precision = 6, .unit = Unit::Microsecond, .increment = 1 };
+        }
+
+        // 5. If smallestUnit is NANOSECOND, then
+        if (*unit == Unit::Nanosecond) {
+            // a. Return the Record { [[Precision]]: 9, [[Unit]]: NANOSECOND, [[Increment]]: 1  }.
+            return { .precision = 9, .unit = Unit::Nanosecond, .increment = 1 };
+        }
+    }
+
+    // 6. Assert: smallestUnit is UNSET.
+    VERIFY(smallest_unit.has<Unset>());
+
+    // 7. If fractionalDigitCount is auto, then
+    if (fractional_digit_count.has<Auto>()) {
+        // a. Return the Record { [[Precision]]: AUTO, [[Unit]]: NANOSECOND, [[Increment]]: 1  }.
+        return { .precision = Auto {}, .unit = Unit::Nanosecond, .increment = 1 };
+    }
+
+    auto fractional_digits = fractional_digit_count.get<u8>();
+
+    // 8. If fractionalDigitCount = 0, then
+    if (fractional_digits == 0) {
+        // a. Return the Record { [[Precision]]: 0, [[Unit]]: SECOND, [[Increment]]: 1  }.
+        return { .precision = 0, .unit = Unit::Second, .increment = 1 };
+    }
+
+    // 9. If fractionalDigitCount is in the inclusive interval from 1 to 3, then
+    if (fractional_digits >= 1 && fractional_digits <= 3) {
+        // a. Return the Record { [[Precision]]: fractionalDigitCount, [[Unit]]: MILLISECOND, [[Increment]]: 10**(3 - fractionalDigitCount)  }.
+        return { .precision = fractional_digits, .unit = Unit::Millisecond, .increment = static_cast<u8>(pow(10, 3 - fractional_digits)) };
+    }
+
+    // 10. If fractionalDigitCount is in the inclusive interval from 4 to 6, then
+    if (fractional_digits >= 4 && fractional_digits <= 6) {
+        // a. Return the Record { [[Precision]]: fractionalDigitCount, [[Unit]]: MICROSECOND, [[Increment]]: 10**(6 - fractionalDigitCount)  }.
+        return { .precision = fractional_digits, .unit = Unit::Microsecond, .increment = static_cast<u8>(pow(10, 6 - fractional_digits)) };
+    }
+
+    // 11. Assert: fractionalDigitCount is in the inclusive interval from 7 to 9.
+    VERIFY(fractional_digits >= 7 && fractional_digits <= 9);
+
+    // 12. Return the Record { [[Precision]]: fractionalDigitCount, [[Unit]]: NANOSECOND, [[Increment]]: 10**(9 - fractionalDigitCount)  }.
+    return { .precision = fractional_digits, .unit = Unit::Nanosecond, .increment = static_cast<u8>(pow(10, 9 - fractional_digits)) };
+}
+
+// 13.17 GetTemporalUnitValuedOption ( options, key, unitGroup, default [ , extraValues ] ), https://tc39.es/proposal-temporal/#sec-temporal-gettemporalunitvaluedoption
+ThrowCompletionOr<UnitValue> get_temporal_unit_valued_option(VM& vm, Object const& options, PropertyKey const& key, UnitGroup unit_group, UnitDefault const& default_, ReadonlySpan<UnitValue> extra_values)
+{
+    // 1. Let allowedValues be a new empty List.
+    Vector<UnitValue> allowed_values;
+
+    // 2. For each row of Table 21, except the header row, in table order, do
+    for (auto const& row : temporal_units) {
+        // a. Let unit be the value in the "Value" column of the row.
+        auto unit = row.value;
+
+        // b. If the "Category" column of the row is DATE and unitGroup is DATE or DATETIME, append unit to allowedValues.
+        if (row.category == UnitCategory::Date && (unit_group == UnitGroup::Date || unit_group == UnitGroup::DateTime))
+            allowed_values.append(unit);
+
+        // c. Else if the "Category" column of the row is TIME and unitGroup is TIME or DATETIME, append unit to allowedValues.
+        if (row.category == UnitCategory::Time && (unit_group == UnitGroup::Time || unit_group == UnitGroup::DateTime))
+            allowed_values.append(unit);
+    }
+
+    // 3. If extraValues is present, then
+    if (!extra_values.is_empty()) {
+        // a. Set allowedValues to the list-concatenation of allowedValues and extraValues.
+        for (auto value : extra_values)
+            allowed_values.append(value);
+    }
+
+    OptionDefault default_value;
+
+    // 4. If default is UNSET, then
+    if (default_.has<Unset>()) {
+        // a. Let defaultValue be undefined.
+        default_value = {};
+    }
+    // 5. Else if default is REQUIRED, then
+    else if (default_.has<Required>()) {
+        // a. Let defaultValue be REQUIRED.
+        default_value = Required {};
+    }
+    // 6. Else if default is AUTO, then
+    else if (default_.has<Auto>()) {
+        // a. Append default to allowedValues.
+        allowed_values.append(Auto {});
+
+        // b. Let defaultValue be "auto".
+        default_value = "auto"sv;
+    }
+    // 7. Else,
+    else {
+        auto unit = default_.get<Unit>();
+
+        // a. Assert: allowedValues contains default.
+
+        // b. Let defaultValue be the value in the "Singular property name" column of Table 21 corresponding to the row
+        //    with default in the "Value" column.
+        default_value = temporal_units[to_underlying(unit)].singular_property_name;
+    }
+
+    // 8. Let allowedStrings be a new empty List.
+    Vector<StringView> allowed_strings;
+
+    // 9. For each element value of allowedValues, do
+    for (auto value : allowed_values) {
+        // a. If value is auto, then
+        if (value.has<Auto>()) {
+            // i. Append "auto" to allowedStrings.
+            allowed_strings.append("auto"sv);
+        }
+        // b. Else,
+        else {
+            auto unit = value.get<Unit>();
+
+            // i. Let singularName be the value in the "Singular property name" column of Table 21 corresponding to the
+            //    row with value in the "Value" column.
+            auto singular_name = temporal_units[to_underlying(unit)].singular_property_name;
+
+            // ii. Append singularName to allowedStrings.
+            allowed_strings.append(singular_name);
+
+            // iii. Let pluralName be the value in the "Plural property name" column of the corresponding row.
+            auto plural_name = temporal_units[to_underlying(unit)].plural_property_name;
+
+            // iv. Append pluralName to allowedStrings.
+            allowed_strings.append(plural_name);
+        }
+    }
+
+    // 10. NOTE: For each singular Temporal unit name that is contained within allowedStrings, the corresponding plural
+    //     name is also contained within it.
+
+    // 11. Let value be ? GetOption(options, key, STRING, allowedStrings, defaultValue).
+    auto value = TRY(get_option(vm, options, key, OptionType::String, allowed_strings, default_value));
+
+    // 12. If value is undefined, return UNSET.
+    if (value.is_undefined())
+        return UnitValue { Unset {} };
+
+    auto value_string = value.as_string().utf8_string_view();
+
+    // 13. If value is "auto", return AUTO.
+    if (value_string == "auto"sv)
+        return UnitValue { Auto {} };
+
+    // 14. Return the value in the "Value" column of Table 21 corresponding to the row with value in its "Singular
+    //     property name" or "Plural property name" column.
+    for (auto const& row : temporal_units) {
+        if (value_string.is_one_of(row.singular_property_name, row.plural_property_name))
+            return UnitValue { row.value };
+    }
+
+    VERIFY_NOT_REACHED();
+}
+
 // 13.18 GetTemporalRelativeToOption ( options ), https://tc39.es/proposal-temporal/#sec-temporal-gettemporalrelativetooption
 ThrowCompletionOr<RelativeTo> get_temporal_relative_to_option(VM& vm, Object const& options)
 {
@@ -101,6 +324,305 @@ UnitCategory temporal_unit_category(Unit unit)
     return temporal_units[to_underlying(unit)].category;
 }
 
+// AD-HOC
+Crypto::UnsignedBigInteger const& temporal_unit_length_in_nanoseconds(Unit unit)
+{
+    switch (unit) {
+    case Unit::Day:
+        return NANOSECONDS_PER_DAY;
+    case Unit::Hour:
+        return NANOSECONDS_PER_HOUR;
+    case Unit::Minute:
+        return NANOSECONDS_PER_MINUTE;
+    case Unit::Second:
+        return NANOSECONDS_PER_SECOND;
+    case Unit::Millisecond:
+        return NANOSECONDS_PER_MILLISECOND;
+    case Unit::Microsecond:
+        return NANOSECONDS_PER_MICROSECOND;
+    case Unit::Nanosecond:
+        return NANOSECONDS_PER_NANOSECOND;
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+// 13.24 FormatFractionalSeconds ( subSecondNanoseconds, precision ), https://tc39.es/proposal-temporal/#sec-temporal-formatfractionalseconds
+String format_fractional_seconds(u64 sub_second_nanoseconds, Precision precision)
+{
+    String fraction_string;
+
+    // 1. If precision is auto, then
+    if (precision.has<Auto>()) {
+        // a. If subSecondNanoseconds = 0, return the empty String.
+        if (sub_second_nanoseconds == 0)
+            return String {};
+
+        // b. Let fractionString be ToZeroPaddedDecimalString(subSecondNanoseconds, 9).
+        fraction_string = MUST(String::formatted("{:09}", sub_second_nanoseconds));
+
+        // c. Set fractionString to the longest prefix of fractionString ending with a code unit other than 0x0030 (DIGIT ZERO).
+        fraction_string = MUST(fraction_string.trim("0"sv, TrimMode::Right));
+    }
+    // 2. Else,
+    else {
+        // a. If precision = 0, return the empty String.
+        if (precision.get<u8>() == 0)
+            return String {};
+
+        // b. Let fractionString be ToZeroPaddedDecimalString(subSecondNanoseconds, 9).
+        fraction_string = MUST(String::formatted("{:09}", sub_second_nanoseconds));
+
+        // c. Set fractionString to the substring of fractionString from 0 to precision.
+        fraction_string = MUST(fraction_string.substring_from_byte_offset(0, precision.get<u8>()));
+    }
+
+    // 3. Return the string-concatenation of the code unit 0x002E (FULL STOP) and fractionString.
+    return MUST(String::formatted(".{}", fraction_string));
+}
+
+// 13.26 GetUnsignedRoundingMode ( roundingMode, sign ), https://tc39.es/proposal-temporal/#sec-getunsignedroundingmode
+UnsignedRoundingMode get_unsigned_rounding_mode(RoundingMode rounding_mode, Sign sign)
+{
+    // 1. Return the specification type in the "Unsigned Rounding Mode" column of Table 22 for the row where the value
+    //    in the "Rounding Mode" column is roundingMode and the value in the "Sign" column is sign.
+    switch (rounding_mode) {
+    case RoundingMode::Ceil:
+        return sign == Sign::Positive ? UnsignedRoundingMode::Infinity : UnsignedRoundingMode::Zero;
+    case RoundingMode::Floor:
+        return sign == Sign::Positive ? UnsignedRoundingMode::Zero : UnsignedRoundingMode::Infinity;
+    case RoundingMode::Expand:
+        return UnsignedRoundingMode::Infinity;
+    case RoundingMode::Trunc:
+        return UnsignedRoundingMode::Zero;
+    case RoundingMode::HalfCeil:
+        return sign == Sign::Positive ? UnsignedRoundingMode::HalfInfinity : UnsignedRoundingMode::HalfZero;
+    case RoundingMode::HalfFloor:
+        return sign == Sign::Positive ? UnsignedRoundingMode::HalfZero : UnsignedRoundingMode::HalfInfinity;
+    case RoundingMode::HalfExpand:
+        return UnsignedRoundingMode::HalfInfinity;
+    case RoundingMode::HalfTrunc:
+        return UnsignedRoundingMode::HalfZero;
+    case RoundingMode::HalfEven:
+        return UnsignedRoundingMode::HalfEven;
+    }
+
+    VERIFY_NOT_REACHED();
+}
+
+// 13.27 ApplyUnsignedRoundingMode ( x, r1, r2, unsignedRoundingMode ), https://tc39.es/proposal-temporal/#sec-applyunsignedroundingmode
+double apply_unsigned_rounding_mode(double x, double r1, double r2, UnsignedRoundingMode unsigned_rounding_mode)
+{
+    // 1. If x = r1, return r1.
+    if (x == r1)
+        return r1;
+
+    // 2. Assert: r1 < x < r2.
+    VERIFY(r1 < x && x < r2);
+
+    // 3. Assert: unsignedRoundingMode is not undefined.
+
+    // 4. If unsignedRoundingMode is ZERO, return r1.
+    if (unsigned_rounding_mode == UnsignedRoundingMode::Zero)
+        return r1;
+
+    // 5. If unsignedRoundingMode is INFINITY, return r2.
+    if (unsigned_rounding_mode == UnsignedRoundingMode::Infinity)
+        return r2;
+
+    // 6. Let d1 be x – r1.
+    auto d1 = x - r1;
+
+    // 7. Let d2 be r2 – x.
+    auto d2 = r2 - x;
+
+    // 8. If d1 < d2, return r1.
+    if (d1 < d2)
+        return r1;
+
+    // 9. If d2 < d1, return r2.
+    if (d2 < d1)
+        return r2;
+
+    // 10. Assert: d1 is equal to d2.
+    VERIFY(d1 == d2);
+
+    // 11. If unsignedRoundingMode is HALF-ZERO, return r1.
+    if (unsigned_rounding_mode == UnsignedRoundingMode::HalfZero)
+        return r1;
+
+    // 12. If unsignedRoundingMode is HALF-INFINITY, return r2.
+    if (unsigned_rounding_mode == UnsignedRoundingMode::HalfInfinity)
+        return r2;
+
+    // 13. Assert: unsignedRoundingMode is HALF-EVEN.
+    VERIFY(unsigned_rounding_mode == UnsignedRoundingMode::HalfEven);
+
+    // 14. Let cardinality be (r1 / (r2 – r1)) modulo 2.
+    auto cardinality = modulo((r1 / (r2 - r1)), 2);
+
+    // 15. If cardinality = 0, return r1.
+    if (cardinality == 0)
+        return r1;
+
+    // 16. Return r2.
+    return r2;
+}
+
+// 13.27 ApplyUnsignedRoundingMode ( x, r1, r2, unsignedRoundingMode ), https://tc39.es/proposal-temporal/#sec-applyunsignedroundingmode
+Crypto::SignedBigInteger apply_unsigned_rounding_mode(Crypto::SignedDivisionResult const& x, Crypto::SignedBigInteger const& r1, Crypto::SignedBigInteger const& r2, UnsignedRoundingMode unsigned_rounding_mode, Crypto::UnsignedBigInteger const& increment)
+{
+    // 1. If x = r1, return r1.
+    if (x.quotient == r1 && x.remainder.unsigned_value().is_zero())
+        return r1;
+
+    // 2. Assert: r1 < x < r2.
+    // NOTE: Skipped for the sake of performance.
+
+    // 3. Assert: unsignedRoundingMode is not undefined.
+
+    // 4. If unsignedRoundingMode is ZERO, return r1.
+    if (unsigned_rounding_mode == UnsignedRoundingMode::Zero)
+        return r1;
+
+    // 5. If unsignedRoundingMode is INFINITY, return r2.
+    if (unsigned_rounding_mode == UnsignedRoundingMode::Infinity)
+        return r2;
+
+    // 6. Let d1 be x – r1.
+    auto d1 = x.remainder.unsigned_value();
+
+    // 7. Let d2 be r2 – x.
+    auto d2 = increment.minus(x.remainder.unsigned_value());
+
+    // 8. If d1 < d2, return r1.
+    if (d1 < d2)
+        return r1;
+
+    // 9. If d2 < d1, return r2.
+    if (d2 < d1)
+        return r2;
+
+    // 10. Assert: d1 is equal to d2.
+    // NOTE: Skipped for the sake of performance.
+
+    // 11. If unsignedRoundingMode is HALF-ZERO, return r1.
+    if (unsigned_rounding_mode == UnsignedRoundingMode::HalfZero)
+        return r1;
+
+    // 12. If unsignedRoundingMode is HALF-INFINITY, return r2.
+    if (unsigned_rounding_mode == UnsignedRoundingMode::HalfInfinity)
+        return r2;
+
+    // 13. Assert: unsignedRoundingMode is HALF-EVEN.
+    VERIFY(unsigned_rounding_mode == UnsignedRoundingMode::HalfEven);
+
+    // 14. Let cardinality be (r1 / (r2 – r1)) modulo 2.
+    auto cardinality = modulo(r1.divided_by(r2.minus(r1)).quotient, "2"_bigint);
+
+    // 15. If cardinality = 0, return r1.
+    if (cardinality.unsigned_value().is_zero())
+        return r1;
+
+    // 16. Return r2.
+    return r2;
+}
+
+// 13.28 RoundNumberToIncrement ( x, increment, roundingMode ), https://tc39.es/proposal-temporal/#sec-temporal-roundnumbertoincrement
+double round_number_to_increment(double x, u64 increment, RoundingMode rounding_mode)
+{
+    // 1. Let quotient be x / increment.
+    auto quotient = x / static_cast<double>(increment);
+
+    Sign is_negative;
+
+    // 2. If quotient < 0, then
+    if (quotient < 0) {
+        // a. Let isNegative be NEGATIVE.
+        is_negative = Sign::Negative;
+
+        // b. Set quotient to -quotient.
+        quotient = -quotient;
+    }
+    // 3. Else,
+    else {
+        // a. Let isNegative be POSITIVE.
+        is_negative = Sign::Positive;
+    }
+
+    // 4. Let unsignedRoundingMode be GetUnsignedRoundingMode(roundingMode, isNegative).
+    auto unsigned_rounding_mode = get_unsigned_rounding_mode(rounding_mode, is_negative);
+
+    // 5. Let r1 be the largest integer such that r1 ≤ quotient.
+    auto r1 = floor(quotient);
+
+    // 6. Let r2 be the smallest integer such that r2 > quotient.
+    auto r2 = ceil(quotient);
+    if (quotient == r2)
+        r2++;
+
+    // 7. Let rounded be ApplyUnsignedRoundingMode(quotient, r1, r2, unsignedRoundingMode).
+    auto rounded = apply_unsigned_rounding_mode(quotient, r1, r2, unsigned_rounding_mode);
+
+    // 8. If isNegative is NEGATIVE, set rounded to -rounded.
+    if (is_negative == Sign::Negative)
+        rounded = -rounded;
+
+    // 9. Return rounded × increment.
+    return rounded * static_cast<double>(increment);
+}
+
+// 13.28 RoundNumberToIncrement ( x, increment, roundingMode ), https://tc39.es/proposal-temporal/#sec-temporal-roundnumbertoincrement
+Crypto::SignedBigInteger round_number_to_increment(Crypto::SignedBigInteger const& x, Crypto::UnsignedBigInteger const& increment, RoundingMode rounding_mode)
+{
+    // OPTIMIZATION: If the increment is 1 the number is always rounded.
+    if (increment == 1)
+        return x;
+
+    // 1. Let quotient be x / increment.
+    auto division_result = x.divided_by(increment);
+
+    // OPTIMIZATION: If there's no remainder the number is already rounded.
+    if (division_result.remainder.unsigned_value().is_zero())
+        return x;
+
+    Sign is_negative;
+
+    // 2. If quotient < 0, then
+    if (division_result.quotient.is_negative()) {
+        // a. Let isNegative be NEGATIVE.
+        is_negative = Sign::Negative;
+
+        // b. Set quotient to -quotient.
+        division_result.quotient.negate();
+        division_result.remainder.negate();
+    }
+    // 3. Else,
+    else {
+        // a. Let isNegative be POSITIVE.
+        is_negative = Sign::Positive;
+    }
+
+    // 4. Let unsignedRoundingMode be GetUnsignedRoundingMode(roundingMode, isNegative).
+    auto unsigned_rounding_mode = get_unsigned_rounding_mode(rounding_mode, is_negative);
+
+    // 5. Let r1 be the largest integer such that r1 ≤ quotient.
+    auto r1 = division_result.quotient;
+
+    // 6. Let r2 be the smallest integer such that r2 > quotient.
+    auto r2 = division_result.quotient.plus(1_bigint);
+
+    // 7. Let rounded be ApplyUnsignedRoundingMode(quotient, r1, r2, unsignedRoundingMode).
+    auto rounded = apply_unsigned_rounding_mode(division_result, r1, r2, unsigned_rounding_mode, increment);
+
+    // 8. If isNegative is NEGATIVE, set rounded to -rounded.
+    if (is_negative == Sign::Negative)
+        rounded.negate();
+
+    // 9. Return rounded × increment.
+    return rounded.multiplied_by(increment);
+}
+
 // 13.35 ParseTemporalDurationString ( isoString ), https://tc39.es/proposal-temporal/#sec-temporal-parsetemporaldurationstring
 ThrowCompletionOr<GC::Ref<Duration>> parse_temporal_duration_string(VM& vm, StringView iso_string)
 {
@@ -353,12 +875,12 @@ ThrowCompletionOr<Value> get_option(VM& vm, Object const& options, PropertyKey c
     // 2. If value is undefined, then
     if (value.is_undefined()) {
         // a. If default is REQUIRED, throw a RangeError exception.
-        if (default_.has<DefaultRequired>())
+        if (default_.has<Required>())
             return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, "undefined"sv, property.as_string());
 
         // b. Return default.
         return default_.visit(
-            [](DefaultRequired) -> Value { VERIFY_NOT_REACHED(); },
+            [](Required) -> Value { VERIFY_NOT_REACHED(); },
             [](Empty) -> Value { return js_undefined(); },
             [](bool default_) -> Value { return Value { default_ }; },
             [](double default_) -> Value { return Value { default_ }; },
@@ -392,4 +914,20 @@ ThrowCompletionOr<Value> get_option(VM& vm, Object const& options, PropertyKey c
     return value;
 }
 
+// 14.4.1.3 GetRoundingModeOption ( options, fallback ), https://tc39.es/proposal-temporal/#sec-temporal-getroundingmodeoption
+ThrowCompletionOr<RoundingMode> get_rounding_mode_option(VM& vm, Object const& options, RoundingMode fallback)
+{
+    // 1. Let allowedStrings be the List of Strings from the "String Identifier" column of Table 26.
+    static constexpr auto allowed_strings = to_array({ "ceil"sv, "floor"sv, "expand"sv, "trunc"sv, "halfCeil"sv, "halfFloor"sv, "halfExpand"sv, "halfTrunc"sv, "halfEven"sv });
+
+    // 2. Let stringFallback be the value from the "String Identifier" column of the row with fallback in its "Rounding Mode" column.
+    auto string_fallback = allowed_strings[to_underlying(fallback)];
+
+    // 3. Let stringValue be ? GetOption(options, "roundingMode", STRING, allowedStrings, stringFallback).
+    auto string_value = TRY(get_option(vm, options, vm.names.roundingMode, OptionType::String, allowed_strings, string_fallback));
+
+    // 4. Return the value from the "Rounding Mode" column of the row with stringValue in its "String Identifier" column.
+    return static_cast<RoundingMode>(allowed_strings.first_index_of(string_value.as_string().utf8_string_view()).value());
+}
+
 }