text: /*
   * Copyright (c) 2021, Tim Flynn <trflynn89@pm.me>
   *
   * SPDX-License-Identifier: BSD-2-Clause
   */
  
  #include <AK/Utf8View.h>
  #include <LibJS/Runtime/Array.h>
  #include <LibJS/Runtime/GlobalObject.h>
  #include <LibJS/Runtime/Intl/NumberFormat.h>
  #include <LibJS/Runtime/Intl/NumberFormatFunction.h>
  #include <LibUnicode/CurrencyCode.h>
  #include <LibUnicode/Locale.h>
  #include <math.h>
  #include <stdlib.h>
  
  namespace JS::Intl {
  
  // 15 NumberFormat Objects, https://tc39.es/ecma402/#numberformat-objects
  NumberFormat::NumberFormat(Object& prototype)
      : Object(prototype)
  {
  }
  
  void NumberFormat::visit_edges(Cell::Visitor& visitor)
  {
      Base::visit_edges(visitor);
      if (m_bound_format)
          visitor.visit(m_bound_format);
  }
  
  void NumberFormat::set_style(StringView style)
  {
      if (style == "decimal"sv)
          m_style = Style::Decimal;
      else if (style == "percent"sv)
          m_style = Style::Percent;
      else if (style == "currency"sv)
          m_style = Style::Currency;
      else if (style == "unit"sv)
          m_style = Style::Unit;
      else
          VERIFY_NOT_REACHED();
  }
  
  StringView NumberFormat::style_string() const
  {
      switch (m_style) {
      case Style::Decimal:
          return "decimal"sv;
      case Style::Percent:
          return "percent"sv;
      case Style::Currency:
          return "currency"sv;
      case Style::Unit:
          return "unit"sv;
      default:
          VERIFY_NOT_REACHED();
      }
  }
  
  void NumberFormat::set_currency_display(StringView currency_display)
  {
      m_resolved_currency_display.clear();
  
      if (currency_display == "code"sv)
          m_currency_display = CurrencyDisplay::Code;
      else if (currency_display == "symbol"sv)
          m_currency_display = CurrencyDisplay::Symbol;
      else if (currency_display == "narrowSymbol"sv)
          m_currency_display = CurrencyDisplay::NarrowSymbol;
      else if (currency_display == "name"sv)
          m_currency_display = CurrencyDisplay::Name;
      else
          VERIFY_NOT_REACHED();
  }
  
  StringView NumberFormat::resolve_currency_display()
  {
      if (m_resolved_currency_display.has_value())
          return *m_resolved_currency_display;
  
      switch (currency_display()) {
      case NumberFormat::CurrencyDisplay::Code:
          m_resolved_currency_display = currency();
          break;
      case NumberFormat::CurrencyDisplay::Symbol:
          m_resolved_currency_display = Unicode::get_locale_currency_mapping(data_locale(), currency(), Unicode::Style::Short);
          break;
      case NumberFormat::CurrencyDisplay::NarrowSymbol:
          m_resolved_currency_display = Unicode::get_locale_currency_mapping(data_locale(), currency(), Unicode::Style::Narrow);
          break;
      case NumberFormat::CurrencyDisplay::Name:
          m_resolved_currency_display = Unicode::get_locale_currency_mapping(data_locale(), currency(), Unicode::Style::Numeric);
          break;
      default:
          VERIFY_NOT_REACHED();
      }
  
      if (!m_resolved_currency_display.has_value())
          m_resolved_currency_display = currency();
  
      return *m_resolved_currency_display;
  }
  
  StringView NumberFormat::currency_display_string() const
  {
      VERIFY(m_currency_display.has_value());
  
      switch (*m_currency_display) {
      case CurrencyDisplay::Code:
          return "code"sv;
      case CurrencyDisplay::Symbol:
          return "symbol"sv;
      case CurrencyDisplay::NarrowSymbol:
          return "narrowSymbol"sv;
      case CurrencyDisplay::Name:
          return "name"sv;
      default:
          VERIFY_NOT_REACHED();
      }
  }
  
  void NumberFormat::set_currency_sign(StringView currency_sign)
  {
      if (currency_sign == "standard"sv)
          m_currency_sign = CurrencySign::Standard;
      else if (currency_sign == "accounting"sv)
          m_currency_sign = CurrencySign::Accounting;
      else
          VERIFY_NOT_REACHED();
  }
  
  StringView NumberFormat::currency_sign_string() const
  {
      VERIFY(m_currency_sign.has_value());
  
      switch (*m_currency_sign) {
      case CurrencySign::Standard:
          return "standard"sv;
      case CurrencySign::Accounting:
          return "accounting"sv;
      default:
          VERIFY_NOT_REACHED();
      }
  }
  
  void NumberFormat::set_unit_display(StringView unit_display)
  {
      if (unit_display == "short"sv)
          m_unit_display = UnitDisplay::Short;
      else if (unit_display == "narrow"sv)
          m_unit_display = UnitDisplay::Narrow;
      else if (unit_display == "long"sv)
          m_unit_display = UnitDisplay::Long;
      else
          VERIFY_NOT_REACHED();
  }
  
  StringView NumberFormat::unit_display_string() const
  {
      VERIFY(m_unit_display.has_value());
  
      switch (*m_unit_display) {
      case UnitDisplay::Short:
          return "short"sv;
      case UnitDisplay::Narrow:
          return "narrow"sv;
      case UnitDisplay::Long:
          return "long"sv;
      default:
          VERIFY_NOT_REACHED();
      }
  }
  
  StringView NumberFormat::rounding_type_string() const
  {
      switch (m_rounding_type) {
      case RoundingType::SignificantDigits:
          return "significantDigits"sv;
      case RoundingType::FractionDigits:
          return "fractionDigits"sv;
      case RoundingType::CompactRounding:
          return "compactRounding"sv;
      default:
          VERIFY_NOT_REACHED();
      }
  }
  
  void NumberFormat::set_notation(StringView notation)
  {
      if (notation == "standard"sv)
          m_notation = Notation::Standard;
      else if (notation == "scientific"sv)
          m_notation = Notation::Scientific;
      else if (notation == "engineering"sv)
          m_notation = Notation::Engineering;
      else if (notation == "compact"sv)
          m_notation = Notation::Compact;
      else
          VERIFY_NOT_REACHED();
  }
  
  StringView NumberFormat::notation_string() const
  {
      switch (m_notation) {
      case Notation::Standard:
          return "standard"sv;
      case Notation::Scientific:
          return "scientific"sv;
      case Notation::Engineering:
          return "engineering"sv;
      case Notation::Compact:
          return "compact"sv;
      default:
          VERIFY_NOT_REACHED();
      }
  }
  
  void NumberFormat::set_compact_display(StringView compact_display)
  {
      if (compact_display == "short"sv)
          m_compact_display = CompactDisplay::Short;
      else if (compact_display == "long"sv)
          m_compact_display = CompactDisplay::Long;
      else
          VERIFY_NOT_REACHED();
  }
  
  StringView NumberFormat::compact_display_string() const
  {
      VERIFY(m_compact_display.has_value());
  
      switch (*m_compact_display) {
      case CompactDisplay::Short:
          return "short"sv;
      case CompactDisplay::Long:
          return "long"sv;
      default:
          VERIFY_NOT_REACHED();
      }
  }
  
  void NumberFormat::set_sign_display(StringView sign_display)
  {
      if (sign_display == "auto"sv)
          m_sign_display = SignDisplay::Auto;
      else if (sign_display == "never"sv)
          m_sign_display = SignDisplay::Never;
      else if (sign_display == "always"sv)
          m_sign_display = SignDisplay::Always;
      else if (sign_display == "exceptZero"sv)
          m_sign_display = SignDisplay::ExceptZero;
      else
          VERIFY_NOT_REACHED();
  }
  
  StringView NumberFormat::sign_display_string() const
  {
      switch (m_sign_display) {
      case SignDisplay::Auto:
          return "auto"sv;
      case SignDisplay::Never:
          return "never"sv;
      case SignDisplay::Always:
          return "always"sv;
      case SignDisplay::ExceptZero:
          return "exceptZero"sv;
      default:
          VERIFY_NOT_REACHED();
      }
  }
  
  static ALWAYS_INLINE int log10floor(double value)
  {
      return static_cast<int>(floor(log10(value)));
  }
  
  // 15.1.1 SetNumberFormatDigitOptions ( intlObj, options, mnfdDefault, mxfdDefault, notation ), https://tc39.es/ecma402/#sec-setnfdigitoptions
  ThrowCompletionOr<void> set_number_format_digit_options(GlobalObject& global_object, NumberFormat& intl_object, Object const& options, int default_min_fraction_digits, int default_max_fraction_digits, NumberFormat::Notation notation)
  {
      auto& vm = global_object.vm();
  
      // 1. Let mnid be ? GetNumberOption(options, "minimumIntegerDigits,", 1, 21, 1).
      auto min_integer_digits = TRY(get_number_option(global_object, options, vm.names.minimumIntegerDigits, 1, 21, 1));
  
      // 2. Let mnfd be ? Get(options, "minimumFractionDigits").
      auto min_fraction_digits = TRY(options.get(vm.names.minimumFractionDigits));
  
      // 3. Let mxfd be ? Get(options, "maximumFractionDigits").
      auto max_fraction_digits = TRY(options.get(vm.names.maximumFractionDigits));
  
      // 4. Let mnsd be ? Get(options, "minimumSignificantDigits").
      auto min_significant_digits = TRY(options.get(vm.names.minimumSignificantDigits));
  
      // 5. Let mxsd be ? Get(options, "maximumSignificantDigits").
      auto max_significant_digits = TRY(options.get(vm.names.maximumSignificantDigits));
  
      // 6. Set intlObj.[[MinimumIntegerDigits]] to mnid.
      intl_object.set_min_integer_digits(*min_integer_digits);
  
      // 7. If mnsd is not undefined or mxsd is not undefined, then
      //     a. Let hasSd be true.
      // 8. Else,
      //     a. Let hasSd be false.
      bool has_significant_digits = !min_significant_digits.is_undefined() || !max_significant_digits.is_undefined();
  
      // 9. If mnfd is not undefined or mxfd is not undefined, then
      //     a. Let hasFd be true.
      // 10. Else,
      //     a. Let hasFd be false.
      bool has_fraction_digits = !min_fraction_digits.is_undefined() || !max_fraction_digits.is_undefined();
  
      // 11. Let needSd be hasSd.
      bool need_significant_digits = has_significant_digits;
  
      // 12. If hasSd is true, or hasFd is false and notation is "compact", then
      //     a. Let needFd be false.
      // 13. Else,
      //     a. Let needFd be true.
      bool need_fraction_digits = !has_significant_digits && (has_fraction_digits || (notation != NumberFormat::Notation::Compact));
  
      // 14. If needSd is true, then
      if (need_significant_digits) {
          // a. Assert: hasSd is true.
          VERIFY(has_significant_digits);
  
          // b. Set mnsd to ? DefaultNumberOption(mnsd, 1, 21, 1).
          auto min_digits = TRY(default_number_option(global_object, min_significant_digits, 1, 21, 1));
  
          // c. Set mxsd to ? DefaultNumberOption(mxsd, mnsd, 21, 21).
          auto max_digits = TRY(default_number_option(global_object, max_significant_digits, *min_digits, 21, 21));
  
          // d. Set intlObj.[[MinimumSignificantDigits]] to mnsd.
          intl_object.set_min_significant_digits(*min_digits);
  
          // e. Set intlObj.[[MaximumSignificantDigits]] to mxsd.
          intl_object.set_max_significant_digits(*max_digits);
      }
  
      // 15. If needFd is true, then
      if (need_fraction_digits) {
          // a. If hasFd is true, then
          if (has_fraction_digits) {
              // i. Set mnfd to ? DefaultNumberOption(mnfd, 0, 20, undefined).
              auto min_digits = TRY(default_number_option(global_object, min_fraction_digits, 0, 20, {}));
  
              // ii. Set mxfd to ? DefaultNumberOption(mxfd, 0, 20, undefined).
              auto max_digits = TRY(default_number_option(global_object, max_fraction_digits, 0, 20, {}));
  
              // iii. If mnfd is undefined, set mnfd to min(mnfdDefault, mxfd).
              if (!min_digits.has_value())
                  min_digits = min(default_min_fraction_digits, *max_digits);
              // iv. Else if mxfd is undefined, set mxfd to max(mxfdDefault, mnfd).
              else if (!max_digits.has_value())
                  max_digits = max(default_max_fraction_digits, *min_digits);
              // v. Else if mnfd is greater than mxfd, throw a RangeError exception.
              else if (*min_digits > *max_digits)
                  return vm.throw_completion<RangeError>(global_object, ErrorType::IntlMinimumExceedsMaximum, *min_digits, *max_digits);
  
              // vi. Set intlObj.[[MinimumFractionDigits]] to mnfd.
              intl_object.set_min_fraction_digits(*min_digits);
  
              // vii. Set intlObj.[[MaximumFractionDigits]] to mxfd.
              intl_object.set_max_fraction_digits(*max_digits);
          }
          // b. Else,
          else {
              // i. Set intlObj.[[MinimumFractionDigits]] to mnfdDefault.
              intl_object.set_min_fraction_digits(default_min_fraction_digits);
  
              // ii. Set intlObj.[[MaximumFractionDigits]] to mxfdDefault.
              intl_object.set_max_fraction_digits(default_max_fraction_digits);
          }
      }
  
      // 16. If needSd is false and needFd is false, then
      if (!need_significant_digits && !need_fraction_digits) {
          // a. Set intlObj.[[RoundingType]] to compactRounding.
          intl_object.set_rounding_type(NumberFormat::RoundingType::CompactRounding);
      }
      // 17. Else if hasSd is true, then
      else if (has_significant_digits) {
          // a. Set intlObj.[[RoundingType]] to significantDigits.
          intl_object.set_rounding_type(NumberFormat::RoundingType::SignificantDigits);
      }
      // 18. Else,
      else {
          // a. Set intlObj.[[RoundingType]] to fractionDigits.
          intl_object.set_rounding_type(NumberFormat::RoundingType::FractionDigits);
      }
  
      return {};
  }
  
  // 15.1.2 InitializeNumberFormat ( numberFormat, locales, options ), https://tc39.es/ecma402/#sec-initializenumberformat
  ThrowCompletionOr<NumberFormat*> initialize_number_format(GlobalObject& global_object, NumberFormat& number_format, Value locales_value, Value options_value)
  {
      auto& vm = global_object.vm();
  
      // 1. Let requestedLocales be ? CanonicalizeLocaleList(locales).
      auto requested_locales = TRY(canonicalize_locale_list(global_object, locales_value));
  
      // 2. Set options to ? CoerceOptionsToObject(options).
      auto* options = TRY(coerce_options_to_object(global_object, options_value));
  
      // 3. Let opt be a new Record.
      LocaleOptions opt {};
  
      // 4. Let matcher be ? GetOption(options, "localeMatcher", "string", « "lookup", "best fit" », "best fit").
      auto matcher = TRY(get_option(global_object, *options, vm.names.localeMatcher, Value::Type::String, { "lookup"sv, "best fit"sv }, "best fit"sv));
  
      // 5. Set opt.[[localeMatcher]] to matcher.
      opt.locale_matcher = matcher;
  
      // 6. Let numberingSystem be ? GetOption(options, "numberingSystem", "string", undefined, undefined).
      auto numbering_system = TRY(get_option(global_object, *options, vm.names.numberingSystem, Value::Type::String, {}, Empty {}));
  
      // 7. If numberingSystem is not undefined, then
      if (!numbering_system.is_undefined()) {
          // a. If numberingSystem does not match the Unicode Locale Identifier type nonterminal, throw a RangeError exception.
          if (!Unicode::is_type_identifier(numbering_system.as_string().string()))
              return vm.throw_completion<RangeError>(global_object, ErrorType::OptionIsNotValidValue, numbering_system, "numberingSystem"sv);
  
          // 8. Set opt.[[nu]] to numberingSystem.
          opt.nu = numbering_system.as_string().string();
      }
  
      // 9. Let localeData be %NumberFormat%.[[LocaleData]].
      // 10. Let r be ResolveLocale(%NumberFormat%.[[AvailableLocales]], requestedLocales, opt, %NumberFormat%.[[RelevantExtensionKeys]], localeData).
      auto result = resolve_locale(requested_locales, opt, NumberFormat::relevant_extension_keys());
  
      // 11. Set numberFormat.[[Locale]] to r.[[locale]].
      number_format.set_locale(move(result.locale));
  
      // 12. Set numberFormat.[[DataLocale]] to r.[[dataLocale]].
      number_format.set_data_locale(move(result.data_locale));
  
      // 13. Set numberFormat.[[NumberingSystem]] to r.[[nu]].
      number_format.set_numbering_system(result.nu.release_value());
  
      // 14. Perform ? SetNumberFormatUnitOptions(numberFormat, options).
      TRY(set_number_format_unit_options(global_object, number_format, *options));
  
      // 15. Let style be numberFormat.[[Style]].
      auto style = number_format.style();
  
      int default_min_fraction_digits = 0;
      int default_max_fraction_digits = 0;
  
      // 16. If style is "currency", then
      if (style == NumberFormat::Style::Currency) {
          // a. Let currency be numberFormat.[[Currency]].
          auto const& currency = number_format.currency();
  
          // b. Let cDigits be CurrencyDigits(currency).
          int digits = currency_digits(currency);
  
          // c. Let mnfdDefault be cDigits.
          default_min_fraction_digits = digits;
  
          // d. Let mxfdDefault be cDigits.
          default_max_fraction_digits = digits;
      }
      // 17. Else,
      else {
          // a. Let mnfdDefault be 0.
          default_min_fraction_digits = 0;
  
          // b. If style is "percent", then
          //     i. Let mxfdDefault be 0.
          // c. Else,
          //     i. Let mxfdDefault be 3.
          default_max_fraction_digits = style == NumberFormat::Style::Percent ? 0 : 3;
      }
  
      // 18. Let notation be ? GetOption(options, "notation", "string", « "standard", "scientific", "engineering", "compact" », "standard").
      auto notation = TRY(get_option(global_object, *options, vm.names.notation, Value::Type::String, { "standard"sv, "scientific"sv, "engineering"sv, "compact"sv }, "standard"sv));
  
      // 19. Set numberFormat.[[Notation]] to notation.
      number_format.set_notation(notation.as_string().string());
  
      // 20. Perform ? SetNumberFormatDigitOptions(numberFormat, options, mnfdDefault, mxfdDefault, notation).
      TRY(set_number_format_digit_options(global_object, number_format, *options, default_min_fraction_digits, default_max_fraction_digits, number_format.notation()));
  
      // 21. Let compactDisplay be ? GetOption(options, "compactDisplay", "string", « "short", "long" », "short").
      auto compact_display = TRY(get_option(global_object, *options, vm.names.compactDisplay, Value::Type::String, { "short"sv, "long"sv }, "short"sv));
  
      // 22. If notation is "compact", then
      if (number_format.notation() == NumberFormat::Notation::Compact) {
          // a. Set numberFormat.[[CompactDisplay]] to compactDisplay.
          number_format.set_compact_display(compact_display.as_string().string());
      }
  
      // 23. Let useGrouping be ? GetOption(options, "useGrouping", "boolean", undefined, true).
      auto use_grouping = TRY(get_option(global_object, *options, vm.names.useGrouping, Value::Type::Boolean, {}, true));
  
      // 24. Set numberFormat.[[UseGrouping]] to useGrouping.
      number_format.set_use_grouping(use_grouping.as_bool());
  
      // 25. Let signDisplay be ? GetOption(options, "signDisplay", "string", « "auto", "never", "always", "exceptZero" », "auto").
      auto sign_display = TRY(get_option(global_object, *options, vm.names.signDisplay, Value::Type::String, { "auto"sv, "never"sv, "always"sv, "exceptZero"sv }, "auto"sv));
  
      // 26. Set numberFormat.[[SignDisplay]] to signDisplay.
      number_format.set_sign_display(sign_display.as_string().string());
  
      // 27. Return numberFormat.
      return &number_format;
  }
  
  // 15.1.3 CurrencyDigits ( currency ), https://tc39.es/ecma402/#sec-currencydigits
  int currency_digits(StringView currency)
  {
      // 1. If the ISO 4217 currency and funds code list contains currency as an alphabetic code, return the minor
      //    unit value corresponding to the currency from the list; otherwise, return 2.
      if (auto currency_code = Unicode::get_currency_code(currency); currency_code.has_value())
          return currency_code->minor_unit.value_or(2);
      return 2;
  }
  
  // 15.1.5 FormatNumericToString ( intlObject, x ), https://tc39.es/ecma402/#sec-formatnumberstring
  FormatResult format_numeric_to_string(NumberFormat& number_format, double number)
  {
      // 1. If x < 0 or x is -0𝔽, let isNegative be true; else let isNegative be false.
      bool is_negative = (number < 0.0) || Value(number).is_negative_zero();
  
      // 2. If isNegative, then
      if (is_negative) {
          // a. Let x be -x.
          number *= -1;
      }
  
      RawFormatResult result {};
  
      switch (number_format.rounding_type()) {
      // 3. If intlObject.[[RoundingType]] is significantDigits, then
      case NumberFormat::RoundingType::SignificantDigits:
          // a. Let result be ToRawPrecision(x, intlObject.[[MinimumSignificantDigits]], intlObject.[[MaximumSignificantDigits]]).
          result = to_raw_precision(number, number_format.min_significant_digits(), number_format.max_significant_digits());
          break;
  
      // 4. Else if intlObject.[[RoundingType]] is fractionDigits, then
      case NumberFormat::RoundingType::FractionDigits:
          // a. Let result be ToRawFixed(x, intlObject.[[MinimumFractionDigits]], intlObject.[[MaximumFractionDigits]]).
          result = to_raw_fixed(number, number_format.min_fraction_digits(), number_format.max_fraction_digits());
          break;
  
      // 5. Else,
      case NumberFormat::RoundingType::CompactRounding:
          // a. Assert: intlObject.[[RoundingType]] is compactRounding.
          // b. Let result be ToRawPrecision(x, 1, 2).
          result = to_raw_precision(number, 1, 2);
  
          // c. If result.[[IntegerDigitsCount]] > 1, then
          if (result.digits > 1) {
              // i. Let result be ToRawFixed(x, 0, 0).
              result = to_raw_fixed(number, 0, 0);
          }
  
          break;
  
      default:
          VERIFY_NOT_REACHED();
      }
  
      // 6. Let x be result.[[RoundedNumber]].
      number = result.rounded_number;
  
      // 7. Let string be result.[[FormattedString]].
      auto string = move(result.formatted_string);
  
      // 8. Let int be result.[[IntegerDigitsCount]].
      int digits = result.digits;
  
      // 9. Let minInteger be intlObject.[[MinimumIntegerDigits]].
      int min_integer = number_format.min_integer_digits();
  
      // 10. If int < minInteger, then
      if (digits < min_integer) {
          // a. Let forwardZeros be the String consisting of minInteger–int occurrences of the character "0".
          auto forward_zeros = String::repeated('0', min_integer - digits);
  
          // b. Set string to the string-concatenation of forwardZeros and string.
          string = String::formatted("{}{}", forward_zeros, string);
      }
  
      // 11. If isNegative, then
      if (is_negative) {
          // a. Let x be -x.
          number *= -1;
      }
  
      // 12. Return the Record { [[RoundedNumber]]: x, [[FormattedString]]: string }.
      return { move(string), number };
  }
  
  // 15.1.6 PartitionNumberPattern ( numberFormat, x ), https://tc39.es/ecma402/#sec-partitionnumberpattern
  Vector<PatternPartition> partition_number_pattern(NumberFormat& number_format, double number)
  {
      // 1. Let exponent be 0.
      int exponent = 0;
  
      String formatted_string;
  
      // 2. If x is NaN, then
      if (Value(number).is_nan()) {
          // a. Let n be an implementation- and locale-dependent (ILD) String value indicating the NaN value.
          formatted_string = Unicode::get_number_system_symbol(number_format.data_locale(), number_format.numbering_system(), "nan"sv).value_or("NaN"sv);
      }
      // 3. Else if x is a non-finite Number, then
      else if (!Value(number).is_finite_number()) {
          // a. Let n be an ILD String value indicating infinity.
          formatted_string = Unicode::get_number_system_symbol(number_format.data_locale(), number_format.numbering_system(), "infinity"sv).value_or("infinity"sv);
      }
      // 4. Else,
      else {
          // a. If numberFormat.[[Style]] is "percent", let x be 100 × x.
          if (number_format.style() == NumberFormat::Style::Percent)
              number = number * 100;
  
          // b. Let exponent be ComputeExponent(numberFormat, x).
          exponent = compute_exponent(number_format, number);
  
          // c. Let x be x × 10^(-exponent).
          number *= pow(10, -exponent);
  
          // d. Let formatNumberResult be FormatNumericToString(numberFormat, x).
          auto format_number_result = format_numeric_to_string(number_format, number);
  
          // e. Let n be formatNumberResult.[[FormattedString]].
          formatted_string = move(format_number_result.formatted_string);
  
          // f. Let x be formatNumberResult.[[RoundedNumber]].
          number = format_number_result.rounded_number;
      }
  
      Unicode::NumberFormat found_pattern {};
  
      // 5. Let pattern be GetNumberFormatPattern(numberFormat, x).
      auto pattern = get_number_format_pattern(number_format, number, found_pattern);
      if (!pattern.has_value())
          return {};
  
      // 6. Let result be a new empty List.
      Vector<PatternPartition> result;
  
      // 7. Let patternParts be PartitionPattern(pattern).
      auto pattern_parts = pattern->visit([](auto const& p) { return partition_pattern(p); });
  
      // 8. For each Record { [[Type]], [[Value]] } patternPart of patternParts, do
      for (auto& pattern_part : pattern_parts) {
          // a. Let p be patternPart.[[Type]].
          auto part = pattern_part.type;
  
          // b. If p is "literal", then
          if (part == "literal"sv) {
              // i. Append a new Record { [[Type]]: "literal", [[Value]]: patternPart.[[Value]] } as the last element of result.
              result.append({ "literal"sv, move(pattern_part.value) });
          }
  
          // c. Else if p is equal to "number", then
          else if (part == "number"sv) {
              // i. Let notationSubParts be PartitionNotationSubPattern(numberFormat, x, n, exponent).
              auto notation_sub_parts = partition_notation_sub_pattern(number_format, number, formatted_string, exponent);
              // ii. Append all elements of notationSubParts to result.
              result.extend(move(notation_sub_parts));
          }
  
          // d. Else if p is equal to "plusSign", then
          else if (part == "plusSign"sv) {
              // i. Let plusSignSymbol be the ILND String representing the plus sign.
              auto plus_sign_symbol = Unicode::get_number_system_symbol(number_format.data_locale(), number_format.numbering_system(), "plusSign"sv).value_or("+"sv);
              // ii. Append a new Record { [[Type]]: "plusSign", [[Value]]: plusSignSymbol } as the last element of result.
              result.append({ "plusSign"sv, plus_sign_symbol });
          }
  
          // e. Else if p is equal to "minusSign", then
          else if (part == "minusSign"sv) {
              // i. Let minusSignSymbol be the ILND String representing the minus sign.
              auto minus_sign_symbol = Unicode::get_number_system_symbol(number_format.data_locale(), number_format.numbering_system(), "minusSign"sv).value_or("-"sv);
              // ii. Append a new Record { [[Type]]: "minusSign", [[Value]]: minusSignSymbol } as the last element of result.
              result.append({ "minusSign"sv, minus_sign_symbol });
          }
  
          // f. Else if p is equal to "percentSign" and numberFormat.[[Style]] is "percent", then
          else if ((part == "percentSign"sv) && (number_format.style() == NumberFormat::Style::Percent)) {
              // i. Let percentSignSymbol be the ILND String representing the percent sign.
              auto percent_sign_symbol = Unicode::get_number_system_symbol(number_format.data_locale(), number_format.numbering_system(), "percentSign"sv).value_or("%"sv);
              // ii. Append a new Record { [[Type]]: "percentSign", [[Value]]: percentSignSymbol } as the last element of result.
              result.append({ "percentSign"sv, percent_sign_symbol });
          }
  
          // g. Else if p is equal to "unitPrefix" and numberFormat.[[Style]] is "unit", then
          // h. Else if p is equal to "unitSuffix" and numberFormat.[[Style]] is "unit", then
          else if ((part.starts_with("unitIdentifier:"sv)) && (number_format.style() == NumberFormat::Style::Unit)) {
              // Note: Our implementation combines "unitPrefix" and "unitSuffix" into one field, "unitIdentifier".
  
              auto identifier_index = part.substring_view("unitIdentifier:"sv.length()).to_uint();
              VERIFY(identifier_index.has_value());
  
              // i. Let unit be numberFormat.[[Unit]].
              // ii. Let unitDisplay be numberFormat.[[UnitDisplay]].
              // iii. Let mu be an ILD String value representing unit before x in unitDisplay form, which may depend on x in languages having different plural forms.
              auto unit_identifier = found_pattern.identifiers[*identifier_index];
  
              // iv. Append a new Record { [[Type]]: "unit", [[Value]]: mu } as the last element of result.
              result.append({ "unit"sv, unit_identifier });
          }
  
          // i. Else if p is equal to "currencyCode" and numberFormat.[[Style]] is "currency", then
          // j. Else if p is equal to "currencyPrefix" and numberFormat.[[Style]] is "currency", then
          // k. Else if p is equal to "currencySuffix" and numberFormat.[[Style]] is "currency", then
          //
          // Note: Our implementation manipulates the format string to inject/remove spacing around the
          //       currency code during GetNumberFormatPattern so that we do not have to do currency
          //       display / plurality lookups more than once.
          else if ((part == "currency"sv) && (number_format.style() == NumberFormat::Style::Currency)) {
              result.append({ "currency"sv, number_format.resolve_currency_display() });
          }
  
          // l. Else,
          else {
              // i. Let unknown be an ILND String based on x and p.
              // ii. Append a new Record { [[Type]]: "unknown", [[Value]]: unknown } as the last element of result.
  
              // LibUnicode doesn't generate any "unknown" patterns.
              VERIFY_NOT_REACHED();
          }
      }
  
      // 9. Return result.
      return result;
  }
  
  static String replace_digits_for_number_format(NumberFormat& number_format, String formatted_string)
  {
      // https://tc39.es/ecma402/#table-numbering-system-digits
      static HashMap<StringView, AK::Array<u32, 10>> s_numbering_system_digits = {
          { "adlm"sv, { 0x1e950, 0x1e951, 0x1e952, 0x1e953, 0x1e954, 0x1e955, 0x1e956, 0x1e957, 0x1e958, 0x1e959 } },
          { "ahom"sv, { 0x11730, 0x11731, 0x11732, 0x11733, 0x11734, 0x11735, 0x11736, 0x11737, 0x11738, 0x11739 } },
          { "arab"sv, { 0x660, 0x661, 0x662, 0x663, 0x664, 0x665, 0x666, 0x667, 0x668, 0x669 } },
          { "arabext"sv, { 0x6f0, 0x6f1, 0x6f2, 0x6f3, 0x6f4, 0x6f5, 0x6f6, 0x6f7, 0x6f8, 0x6f9 } },
          { "bali"sv, { 0x1b50, 0x1b51, 0x1b52, 0x1b53, 0x1b54, 0x1b55, 0x1b56, 0x1b57, 0x1b58, 0x1b59 } },
          { "beng"sv, { 0x9e6, 0x9e7, 0x9e8, 0x9e9, 0x9ea, 0x9eb, 0x9ec, 0x9ed, 0x9ee, 0x9ef } },
          { "bhks"sv, { 0x11c50, 0x11c51, 0x11c52, 0x11c53, 0x11c54, 0x11c55, 0x11c56, 0x11c57, 0x11c58, 0x11c59 } },
          { "brah"sv, { 0x11066, 0x11067, 0x11068, 0x11069, 0x1106a, 0x1106b, 0x1106c, 0x1106d, 0x1106e, 0x1106f } },
          { "cakm"sv, { 0x11136, 0x11137, 0x11138, 0x11139, 0x1113a, 0x1113b, 0x1113c, 0x1113d, 0x1113e, 0x1113f } },
          { "cham"sv, { 0xaa50, 0xaa51, 0xaa52, 0xaa53, 0xaa54, 0xaa55, 0xaa56, 0xaa57, 0xaa58, 0xaa59 } },
          { "deva"sv, { 0x966, 0x967, 0x968, 0x969, 0x96a, 0x96b, 0x96c, 0x96d, 0x96e, 0x96f } },
          { "diak"sv, { 0x11950, 0x11951, 0x11952, 0x11953, 0x11954, 0x11955, 0x11956, 0x11957, 0x11958, 0x11959 } },
          { "fullwide"sv, { 0xff10, 0xff11, 0xff12, 0xff13, 0xff14, 0xff15, 0xff16, 0xff17, 0xff18, 0xff19 } },
          { "gong"sv, { 0x11da0, 0x11da1, 0x11da2, 0x11da3, 0x11da4, 0x11da5, 0x11da6, 0x11da7, 0x11da8, 0x11da9 } },
          { "gonm"sv, { 0x11d50, 0x11d51, 0x11d52, 0x11d53, 0x11d54, 0x11d55, 0x11d56, 0x11d57, 0x11d58, 0x11d59 } },
          { "gujr"sv, { 0xae6, 0xae7, 0xae8, 0xae9, 0xaea, 0xaeb, 0xaec, 0xaed, 0xaee, 0xaef } },
          { "guru"sv, { 0xa66, 0xa67, 0xa68, 0xa69, 0xa6a, 0xa6b, 0xa6c, 0xa6d, 0xa6e, 0xa6f } },
          { "hanidec"sv, { 0x3007, 0x4e00, 0x4e8c, 0x4e09, 0x56db, 0x4e94, 0x516d, 0x4e03, 0x516b, 0x4e5d } },
          { "hmng"sv, { 0x16b50, 0x16b51, 0x16b52, 0x16b53, 0x16b54, 0x16b55, 0x16b56, 0x16b57, 0x16b58, 0x16b59 } },
          { "hmnp"sv, { 0x1e140, 0x1e141, 0x1e142, 0x1e143, 0x1e144, 0x1e145, 0x1e146, 0x1e147, 0x1e148, 0x1e149 } },
          { "java"sv, { 0xa9d0, 0xa9d1, 0xa9d2, 0xa9d3, 0xa9d4, 0xa9d5, 0xa9d6, 0xa9d7, 0xa9d8, 0xa9d9 } },
          { "kali"sv, { 0xa900, 0xa901, 0xa902, 0xa903, 0xa904, 0xa905, 0xa906, 0xa907, 0xa908, 0xa909 } },
          { "khmr"sv, { 0x17e0, 0x17e1, 0x17e2, 0x17e3, 0x17e4, 0x17e5, 0x17e6, 0x17e7, 0x17e8, 0x17e9 } },
          { "knda"sv, { 0xce6, 0xce7, 0xce8, 0xce9, 0xcea, 0xceb, 0xcec, 0xced, 0xcee, 0xcef } },
          { "lana"sv, { 0x1a80, 0x1a81, 0x1a82, 0x1a83, 0x1a84, 0x1a85, 0x1a86, 0x1a87, 0x1a88, 0x1a89 } },
          { "lanatham"sv, { 0x1a90, 0x1a91, 0x1a92, 0x1a93, 0x1a94, 0x1a95, 0x1a96, 0x1a97, 0x1a98, 0x1a99 } },
          { "laoo"sv, { 0xed0, 0xed1, 0xed2, 0xed3, 0xed4, 0xed5, 0xed6, 0xed7, 0xed8, 0xed9 } },
          { "latn"sv, { 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39 } },
          { "lepc"sv, { 0x1c40, 0x1c41, 0x1c42, 0x1c43, 0x1c44, 0x1c45, 0x1c46, 0x1c47, 0x1c48, 0x1c49 } },
          { "limb"sv, { 0x1946, 0x1947, 0x1948, 0x1949, 0x194a, 0x194b, 0x194c, 0x194d, 0x194e, 0x194f } },
          { "mathbold"sv, { 0x1d7ce, 0x1d7cf, 0x1d7d0, 0x1d7d1, 0x1d7d2, 0x1d7d3, 0x1d7d4, 0x1d7d5, 0x1d7d6, 0x1d7d7 } },
          { "mathdbl"sv, { 0x1d7d8, 0x1d7d9, 0x1d7da, 0x1d7db, 0x1d7dc, 0x1d7dd, 0x1d7de, 0x1d7df, 0x1d7e0, 0x1d7e1 } },
          { "mathmono"sv, { 0x1d7f6, 0x1d7f7, 0x1d7f8, 0x1d7f9, 0x1d7fa, 0x1d7fb, 0x1d7fc, 0x1d7fd, 0x1d7fe, 0x1d7ff } },
          { "mathsanb"sv, { 0x1d7ec, 0x1d7ed, 0x1d7ee, 0x1d7ef, 0x1d7f0, 0x1d7f1, 0x1d7f2, 0x1d7f3, 0x1d7f4, 0x1d7f5 } },
          { "mathsans"sv, { 0x1d7e2, 0x1d7e3, 0x1d7e4, 0x1d7e5, 0x1d7e6, 0x1d7e7, 0x1d7e8, 0x1d7e9, 0x1d7ea, 0x1d7eb } },
          { "mlym"sv, { 0xd66, 0xd67, 0xd68, 0xd69, 0xd6a, 0xd6b, 0xd6c, 0xd6d, 0xd6e, 0xd6f } },
          { "modi"sv, { 0x11650, 0x11651, 0x11652, 0x11653, 0x11654, 0x11655, 0x11656, 0x11657, 0x11658, 0x11659 } },
          { "mong"sv, { 0x1810, 0x1811, 0x1812, 0x1813, 0x1814, 0x1815, 0x1816, 0x1817, 0x1818, 0x1819 } },
          { "mroo"sv, { 0x16a60, 0x16a61, 0x16a62, 0x16a63, 0x16a64, 0x16a65, 0x16a66, 0x16a67, 0x16a68, 0x16a69 } },
          { "mtei"sv, { 0xabf0, 0xabf1, 0xabf2, 0xabf3, 0xabf4, 0xabf5, 0xabf6, 0xabf7, 0xabf8, 0xabf9 } },
          { "mymr"sv, { 0x1040, 0x1041, 0x1042, 0x1043, 0x1044, 0x1045, 0x1046, 0x1047, 0x1048, 0x1049 } },
          { "mymrshan"sv, { 0x1090, 0x1091, 0x1092, 0x1093, 0x1094, 0x1095, 0x1096, 0x1097, 0x1098, 0x1099 } },
          { "mymrtlng"sv, { 0xa9f0, 0xa9f1, 0xa9f2, 0xa9f3, 0xa9f4, 0xa9f5, 0xa9f6, 0xa9f7, 0xa9f8, 0xa9f9 } },
          { "newa"sv, { 0x11450, 0x11451, 0x11452, 0x11453, 0x11454, 0x11455, 0x11456, 0x11457, 0x11458, 0x11459 } },
          { "nkoo"sv, { 0x7c0, 0x7c1, 0x7c2, 0x7c3, 0x7c4, 0x7c5, 0x7c6, 0x7c7, 0x7c8, 0x7c9 } },
          { "olck"sv, { 0x1c50, 0x1c51, 0x1c52, 0x1c53, 0x1c54, 0x1c55, 0x1c56, 0x1c57, 0x1c58, 0x1c59 } },
          { "orya"sv, { 0xb66, 0xb67, 0xb68, 0xb69, 0xb6a, 0xb6b, 0xb6c, 0xb6d, 0xb6e, 0xb6f } },
          { "osma"sv, { 0x104a0, 0x104a1, 0x104a2, 0x104a3, 0x104a4, 0x104a5, 0x104a6, 0x104a7, 0x104a8, 0x104a9 } },
          { "rohg"sv, { 0x10d30, 0x10d31, 0x10d32, 0x10d33, 0x10d34, 0x10d35, 0x10d36, 0x10d37, 0x10d38, 0x10d39 } },
          { "saur"sv, { 0xa8d0, 0xa8d1, 0xa8d2, 0xa8d3, 0xa8d4, 0xa8d5, 0xa8d6, 0xa8d7, 0xa8d8, 0xa8d9 } },
          { "segment"sv, { 0x1fbf0, 0x1fbf1, 0x1fbf2, 0x1fbf3, 0x1fbf4, 0x1fbf5, 0x1fbf6, 0x1fbf7, 0x1fbf8, 0x1fbf9 } },
          { "shrd"sv, { 0x111d0, 0x111d1, 0x111d2, 0x111d3, 0x111d4, 0x111d5, 0x111d6, 0x111d7, 0x111d8, 0x111d9 } },
          { "sind"sv, { 0x112f0, 0x112f1, 0x112f2, 0x112f3, 0x112f4, 0x112f5, 0x112f6, 0x112f7, 0x112f8, 0x112f9 } },
          { "sinh"sv, { 0xde6, 0xde7, 0xde8, 0xde9, 0xdea, 0xdeb, 0xdec, 0xded, 0xdee, 0xdef } },
          { "sora"sv, { 0x110f0, 0x110f1, 0x110f2, 0x110f3, 0x110f4, 0x110f5, 0x110f6, 0x110f7, 0x110f8, 0x110f9 } },
          { "sund"sv, { 0x1bb0, 0x1bb1, 0x1bb2, 0x1bb3, 0x1bb4, 0x1bb5, 0x1bb6, 0x1bb7, 0x1bb8, 0x1bb9 } },
          { "takr"sv, { 0x116c0, 0x116c1, 0x116c2, 0x116c3, 0x116c4, 0x116c5, 0x116c6, 0x116c7, 0x116c8, 0x116c9 } },
          { "talu"sv, { 0x19d0, 0x19d1, 0x19d2, 0x19d3, 0x19d4, 0x19d5, 0x19d6, 0x19d7, 0x19d8, 0x19d9 } },
          { "tamldec"sv, { 0xbe6, 0xbe7, 0xbe8, 0xbe9, 0xbea, 0xbeb, 0xbec, 0xbed, 0xbee, 0xbef } },
          { "telu"sv, { 0xc66, 0xc67, 0xc68, 0xc69, 0xc6a, 0xc6b, 0xc6c, 0xc6d, 0xc6e, 0xc6f } },
          { "thai"sv, { 0xe50, 0xe51, 0xe52, 0xe53, 0xe54, 0xe55, 0xe56, 0xe57, 0xe58, 0xe59 } },
          { "tibt"sv, { 0xf20, 0xf21, 0xf22, 0xf23, 0xf24, 0xf25, 0xf26, 0xf27, 0xf28, 0xf29 } },
          { "tirh"sv, { 0x114d0, 0x114d1, 0x114d2, 0x114d3, 0x114d4, 0x114d5, 0x114d6, 0x114d7, 0x114d8, 0x114d9 } },
          { "vaii"sv, { 0xa620, 0xa621, 0xa622, 0xa623, 0xa624, 0xa625, 0xa626, 0xa627, 0xa628, 0xa629 } },
          { "wara"sv, { 0x118e0, 0x118e1, 0x118e2, 0x118e3, 0x118e4, 0x118e5, 0x118e6, 0x118e7, 0x118e8, 0x118e9 } },
          { "wcho"sv, { 0x1e2f0, 0x1e2f1, 0x1e2f2, 0x1e2f3, 0x1e2f4, 0x1e2f5, 0x1e2f6, 0x1e2f7, 0x1e2f8, 0x1e2f9 } },
      };
  
      auto digits = s_numbering_system_digits.get(number_format.numbering_system());
      if (!digits.has_value())
          digits = s_numbering_system_digits.get("latn"sv);
      VERIFY(digits.has_value());
  
      StringBuilder builder;
  
      for (auto& ch : formatted_string) {
          if (is_ascii_digit(ch)) {
              u32 digit = digits->at(parse_ascii_digit(ch));
              builder.append_code_point(digit);
          } else {
              builder.append(ch);
          }
      }
  
      return builder.build();
  }
  
  static Vector<StringView> separate_integer_into_groups(Unicode::NumberGroupings const& grouping_sizes, StringView integer)
  {
      Utf8View utf8_integer { integer };
      Vector<StringView> groups;
  
      auto add_group = [&](size_t index, size_t length) {
          groups.prepend(utf8_integer.unicode_substring_view(index, length).as_string());
      };
  
      if (utf8_integer.length() > grouping_sizes.primary_grouping_size) {
          size_t index = utf8_integer.length() - grouping_sizes.primary_grouping_size;
          add_group(index, grouping_sizes.primary_grouping_size);
  
          while (index > grouping_sizes.secondary_grouping_size) {
              index -= grouping_sizes.secondary_grouping_size;
              add_group(index, grouping_sizes.secondary_grouping_size);
          }
  
          if (index > 0)
              add_group(0, index);
      } else {
          groups.append(integer);
      }
  
      return groups;
  }
  
  // 15.1.7 PartitionNotationSubPattern ( numberFormat, x, n, exponent ), https://tc39.es/ecma402/#sec-partitionnotationsubpattern
  Vector<PatternPartition> partition_notation_sub_pattern(NumberFormat& number_format, double number, String formatted_string, int exponent)
  {
      // 1. Let result be a new empty List.
      Vector<PatternPartition> result;
  
      auto grouping_sizes = Unicode::get_number_system_groupings(number_format.data_locale(), number_format.numbering_system());
      if (!grouping_sizes.has_value())
          return {};
  
      // 2. If x is NaN, then
      if (Value(number).is_nan()) {
          // a. Append a new Record { [[Type]]: "nan", [[Value]]: n } as the last element of result.
          result.append({ "nan"sv, move(formatted_string) });
      }
      // 3. Else if x is a non-finite Number, then
      else if (!Value(number).is_finite_number()) {
          // a. Append a new Record { [[Type]]: "infinity", [[Value]]: n } as the last element of result.
          result.append({ "infinity"sv, move(formatted_string) });
      }
      // 4. Else,
      else {
          // a. Let notationSubPattern be GetNotationSubPattern(numberFormat, exponent).
          auto notation_sub_pattern = get_notation_sub_pattern(number_format, exponent);
          if (!notation_sub_pattern.has_value())
              return {};
  
          // b. Let patternParts be PartitionPattern(notationSubPattern).
          auto pattern_parts = partition_pattern(*notation_sub_pattern);
  
          // c. For each Record { [[Type]], [[Value]] } patternPart of patternParts, do
          for (auto& pattern_part : pattern_parts) {
              // i. Let p be patternPart.[[Type]].
              auto part = pattern_part.type;
  
              // ii. If p is "literal", then
              if (part == "literal"sv) {
                  // 1. Append a new Record { [[Type]]: "literal", [[Value]]: patternPart.[[Value]] } as the last element of result.
                  result.append({ "literal"sv, move(pattern_part.value) });
              }
              // iii. Else if p is equal to "number", then
              else if (part == "number"sv) {
                  // 1. If the numberFormat.[[NumberingSystem]] matches one of the values in the "Numbering System" column of Table 10 below, then
                  //     a. Let digits be a List whose 10 String valued elements are the UTF-16 string representations of the 10 digits specified in the "Digits" column of the matching row in Table 10.
                  //     b. Replace each digit in n with the value of digits[digit].
                  // 2. Else use an implementation dependent algorithm to map n to the appropriate representation of n in the given numbering system.
                  formatted_string = replace_digits_for_number_format(number_format, move(formatted_string));
  
                  // 3. Let decimalSepIndex be ! StringIndexOf(n, ".", 0).
                  auto decimal_sep_index = formatted_string.find('.');
  
                  StringView integer;
                  Optional<StringView> fraction;
  
                  // 4. If decimalSepIndex > 0, then
                  if (decimal_sep_index.has_value() && (*decimal_sep_index > 0)) {
                      // a. Let integer be the substring of n from position 0, inclusive, to position decimalSepIndex, exclusive.
                      integer = formatted_string.substring_view(0, *decimal_sep_index);
                      // b. Let fraction be the substring of n from position decimalSepIndex, exclusive, to the end of n.
                      fraction = formatted_string.substring_view(*decimal_sep_index + 1);
                  }
                  // 5. Else,
                  else {
                      // a. Let integer be n.
                      integer = formatted_string;
                      // b. Let fraction be undefined.
                  }
  
                  bool use_grouping = number_format.use_grouping();
  
                  // FIXME: The spec doesn't indicate this, but grouping should be disabled for numbers less than 10,000 when the notation is compact.
                  //        This is addressed in Intl.NumberFormat V3 with the "min2" [[UseGrouping]] option. However, test262 explicitly expects this
                  //        behavior in the "de-DE" locale tests, because this is how ICU (and therefore V8, SpiderMoney, etc.) has always behaved.
                  //
                  //        So, in locales "de-*", we must have:
                  //            Intl.NumberFormat("de", {notation: "compact"}).format(1234) === "1234"
                  //            Intl.NumberFormat("de", {notation: "compact"}).format(12345) === "12.345"
                  //            Intl.NumberFormat("de").format(1234) === "1.234"
                  //            Intl.NumberFormat("de").format(12345) === "12.345"
                  //
                  //        See: https://github.com/tc39/proposal-intl-numberformat-v3/issues/3
                  if (number_format.has_compact_format())
                      use_grouping = number >= 10'000;
  
                  // 6. If the numberFormat.[[UseGrouping]] is true, then
                  if (use_grouping) {
                      // a. Let groupSepSymbol be the implementation-, locale-, and numbering system-dependent (ILND) String representing the grouping separator.
                      auto group_sep_symbol = Unicode::get_number_system_symbol(number_format.data_locale(), number_format.numbering_system(), "group"sv).value_or(","sv);
  
                      // b. Let groups be a List whose elements are, in left to right order, the substrings defined by ILND set of locations within the integer.
                      auto groups = separate_integer_into_groups(*grouping_sizes, integer);
  
                      // c. Assert: The number of elements in groups List is greater than 0.
                      VERIFY(!groups.is_empty());
  
                      // d. Repeat, while groups List is not empty,
                      while (!groups.is_empty()) {
                          // i. Remove the first element from groups and let integerGroup be the value of that element.
                          auto integer_group = groups.take_first();
  
                          // ii. Append a new Record { [[Type]]: "integer", [[Value]]: integerGroup } as the last element of result.
                          result.append({ "integer"sv, integer_group });
  
                          // iii. If groups List is not empty, then
                          if (!groups.is_empty()) {
                              // i. Append a new Record { [[Type]]: "group", [[Value]]: groupSepSymbol } as the last element of result.
                              result.append({ "group"sv, group_sep_symbol });
                          }
                      }
                  }
                  // 7. Else,
                  else {
                      // a. Append a new Record { [[Type]]: "integer", [[Value]]: integer } as the last element of result.
                      result.append({ "integer"sv, integer });
                  }
  
                  // 8. If fraction is not undefined, then
                  if (fraction.has_value()) {
                      // a. Let decimalSepSymbol be the ILND String representing the decimal separator.
                      auto decimal_sep_symbol = Unicode::get_number_system_symbol(number_format.data_locale(), number_format.numbering_system(), "decimal"sv).value_or("."sv);
                      // b. Append a new Record { [[Type]]: "decimal", [[Value]]: decimalSepSymbol } as the last element of result.
                      result.append({ "decimal"sv, decimal_sep_symbol });
                      // c. Append a new Record { [[Type]]: "fraction", [[Value]]: fraction } as the last element of result.
                      result.append({ "fraction"sv, fraction.release_value() });
                  }
              }
              // iv. Else if p is equal to "compactSymbol", then
              // v. Else if p is equal to "compactName", then
              else if (part.starts_with("compactIdentifier:"sv)) {
                  // Note: Our implementation combines "compactSymbol" and "compactName" into one field, "compactIdentifier".
  
                  auto identifier_index = part.substring_view("compactIdentifier:"sv.length()).to_uint();
                  VERIFY(identifier_index.has_value());
  
                  // 1. Let compactSymbol be an ILD string representing exponent in short form, which may depend on x in languages having different plural forms. The implementation must be able to provide this string, or else the pattern would not have a "{compactSymbol}" placeholder.
                  auto compact_identifier = number_format.compact_format().identifiers[*identifier_index];
  
                  // 2. Append a new Record { [[Type]]: "compact", [[Value]]: compactSymbol } as the last element of result.
                  result.append({ "compact"sv, compact_identifier });
              }
              // vi. Else if p is equal to "scientificSeparator", then
              else if (part == "scientificSeparator"sv) {
                  // 1. Let scientificSeparator be the ILND String representing the exponent separator.
                  auto scientific_separator = Unicode::get_number_system_symbol(number_format.data_locale(), number_format.numbering_system(), "exponential"sv).value_or("E"sv);
                  // 2. Append a new Record { [[Type]]: "exponentSeparator", [[Value]]: scientificSeparator } as the last element of result.
                  result.append({ "exponentSeparator"sv, scientific_separator });
              }
              // vii. Else if p is equal to "scientificExponent", then
              else if (part == "scientificExponent"sv) {
                  // 1. If exponent < 0, then
                  if (exponent < 0) {
                      // a. Let minusSignSymbol be the ILND String representing the minus sign.
                      auto minus_sign_symbol = Unicode::get_number_system_symbol(number_format.data_locale(), number_format.numbering_system(), "minusSign"sv).value_or("-"sv);
  
                      // b. Append a new Record { [[Type]]: "exponentMinusSign", [[Value]]: minusSignSymbol } as the last element of result.
                      result.append({ "exponentMinusSign"sv, minus_sign_symbol });
  
                      // c. Let exponent be -exponent.
                      exponent *= -1;
                  }
  
                  // 2. Let exponentResult be ToRawFixed(exponent, 1, 0, 0).
                  // Note: See the implementation of ToRawFixed for why we do not pass the 1.
                  auto exponent_result = to_raw_fixed(exponent, 0, 0);
  
                  // FIXME: The spec does not say to do this, but all of major engines perform this replacement.
                  //        Without this, formatting with non-Latin numbering systems will produce non-localized results.
                  exponent_result.formatted_string = replace_digits_for_number_format(number_format, move(exponent_result.formatted_string));
  
                  // 3. Append a new Record { [[Type]]: "exponentInteger", [[Value]]: exponentResult.[[FormattedString]] } as the last element of result.
                  result.append({ "exponentInteger"sv, move(exponent_result.formatted_string) });
              }
              // viii. Else,
              else {
                  // 1. Let unknown be an ILND String based on x and p.
                  // 2. Append a new Record { [[Type]]: "unknown", [[Value]]: unknown } as the last element of result.
  
                  // LibUnicode doesn't generate any "unknown" patterns.
                  VERIFY_NOT_REACHED();
              }
          }
      }
  
      // 5. Return result.
      return result;
  }
  
  // 15.1.8 FormatNumeric ( numberFormat, x ), https://tc39.es/ecma402/#sec-formatnumber
  String format_numeric(NumberFormat& number_format, double number)
  {
      // 1. Let parts be ? PartitionNumberPattern(numberFormat, x).
      // Note: Our implementation of PartitionNumberPattern does not throw.
      auto parts = partition_number_pattern(number_format, number);
  
      // 2. Let result be the empty String.
      StringBuilder result;
  
      // 3. For each Record { [[Type]], [[Value]] } part in parts, do
      for (auto& part : parts) {
          // a. Set result to the string-concatenation of result and part.[[Value]].
          result.append(move(part.value));
      }
  
      // 4. Return result.
      return result.build();
  }
  
  // 15.1.9 FormatNumericToParts ( numberFormat, x ), https://tc39.es/ecma402/#sec-formatnumbertoparts
  Array* format_numeric_to_parts(GlobalObject& global_object, NumberFormat& number_format, double number)
  {
      auto& vm = global_object.vm();
  
      // 1. Let parts be ? PartitionNumberPattern(numberFormat, x).
      // Note: Our implementation of PartitionNumberPattern does not throw.
      auto parts = partition_number_pattern(number_format, number);
  
      // 2. Let result be ArrayCreate(0).
      auto* result = MUST(Array::create(global_object, 0));
  
      // 3. Let n be 0.
      size_t n = 0;
  
      // 4. For each Record { [[Type]], [[Value]] } part in parts, do
      for (auto& part : parts) {
          // a. Let O be OrdinaryObjectCreate(%Object.prototype%).
          auto* object = Object::create(global_object, global_object.object_prototype());
  
          // b. Perform ! CreateDataPropertyOrThrow(O, "type", part.[[Type]]).
          MUST(object->create_data_property_or_throw(vm.names.type, js_string(vm, part.type)));
  
          // c. Perform ! CreateDataPropertyOrThrow(O, "value", part.[[Value]]).
          MUST(object->create_data_property_or_throw(vm.names.value, js_string(vm, move(part.value))));
  
          // d. Perform ! CreateDataPropertyOrThrow(result, ! ToString(n), O).
          MUST(result->create_data_property_or_throw(n, object));
  
          // e. Increment n by 1.
          ++n;
      }
  
      // 5. Return result.
      return result;
  }
  
  static String cut_trailing_zeroes(StringView string, int cut)
  {
      // These steps are exactly the same between ToRawPrecision and ToRawFixed.
  
      // Repeat, while cut > 0 and the last character of m is "0",
      while ((cut > 0) && string.ends_with('0')) {
          // Remove the last character from m.
          string = string.substring_view(0, string.length() - 1);
  
          // Decrease cut by 1.
          --cut;
      }
  
      // If the last character of m is ".", then
      if (string.ends_with('.')) {
          // Remove the last character from m.
          string = string.substring_view(0, string.length() - 1);
      }
  
      return string.to_string();
  }
  
  // 15.1.10 ToRawPrecision ( x, minPrecision, maxPrecision ), https://tc39.es/ecma402/#sec-torawprecision
  RawFormatResult to_raw_precision(double number, int min_precision, int max_precision)
  {
      RawFormatResult result {};
  
      // 1. Let p be maxPrecision.
      int precision = max_precision;
      int exponent = 0;
  
      // 2. If x = 0, then
      if (number == 0.0) {
          // a. Let m be the String consisting of p occurrences of the character "0".
          result.formatted_string = String::repeated('0', precision);
  
          // b. Let e be 0.
          exponent = 0;
  
          // c. Let xFinal be 0.
          result.rounded_number = 0;
      }
  
      // 3. Else,
      else {
          // FIXME: The result of these steps isn't entirely accurate for large values of 'p' (which
          //        defaults to 21, resulting in numbers on the order of 10^21). Either AK::format or
          //        our Number::toString AO (double_to_string in Value.cpp) will need to be improved
          //        to produce more accurate results.
  
          // a. Let e be the base 10 logarithm of x rounded down to the nearest integer.
          exponent = log10floor(number);
  
          double power = pow(10, exponent - precision + 1);
  
          // b. Let n be an integer such that 10^(p–1) ≤ n < 10^p and for which the exact mathematical value of n × 10^(e–p+1) – x
          //    is as close to zero as possible. If there is more than one such n, pick the one for which n × 10^(e–p+1) is larger.
          double n = round(number / power);
  
          // c. Let m be the String consisting of the digits of the decimal representation of n (in order, with no leading zeroes).
          result.formatted_string = Value(n).to_string_without_side_effects();
  
          // d. Let xFinal be n × 10^(e–p+1).
          result.rounded_number = n * power;
      }
  
      // 4. If e ≥ p–1, then
      if (exponent >= (precision - 1)) {
          // a. Let m be the string-concatenation of m and e–p+1 occurrences of the character "0".
          result.formatted_string = String::formatted(
              "{}{}",
              result.formatted_string,
              String::repeated('0', exponent - precision + 1));
  
          // b. Let int be e+1.
          result.digits = exponent + 1;
      }
      // 5. Else if e ≥ 0, then
      else if (exponent >= 0) {
          // a. Let m be the string-concatenation of the first e+1 characters of m, the character ".", and the remaining p–(e+1) characters of m.
          result.formatted_string = String::formatted(
              "{}.{}",
              result.formatted_string.substring_view(0, exponent + 1),
              result.formatted_string.substring_view(exponent + 1));
  
          // b. Let int be e+1.
          result.digits = exponent + 1;
      }
      // 6. Else,
      else {
          // a. Assert: e < 0.
          // b. Let m be the string-concatenation of the String value "0.", –(e+1) occurrences of the character "0", and m.
          result.formatted_string = String::formatted(
              "0.{}{}",
              String::repeated('0', -1 * (exponent + 1)),
              result.formatted_string);
  
          // c. Let int be 1.
          result.digits = 1;
      }
  
      // 7. If m contains the character ".", and maxPrecision > minPrecision, then
      if (result.formatted_string.contains('.') && (max_precision > min_precision)) {
          // a. Let cut be maxPrecision – minPrecision.
          int cut = max_precision - min_precision;
  
          result.formatted_string = cut_trailing_zeroes(result.formatted_string, cut);
      }
  
      // 8. Return the Record { [[FormattedString]]: m, [[RoundedNumber]]: xFinal, [[IntegerDigitsCount]]: int }.
      return result;
  }
  
  // 15.1.11 ToRawFixed ( x, minInteger, minFraction, maxFraction ), https://tc39.es/ecma402/#sec-torawfixed
  // NOTE: The spec has a mistake here. The minInteger parameter is unused and is not provided by FormatNumericToString.
  RawFormatResult to_raw_fixed(double number, int min_fraction, int max_fraction)
  {
      RawFormatResult result {};
  
      // 1. Let f be maxFraction.
      int fraction = max_fraction;
  
      double power = pow(10, fraction);
  
      // 2. Let n be an integer for which the exact mathematical value of n / 10^f – x is as close to zero as possible. If there are two such n, pick the larger n.
      double n = round(number * power);
  
      // 3. Let xFinal be n / 10^f.
      result.rounded_number = n / power;
  
      // 4. If n = 0, let m be the String "0". Otherwise, let m be the String consisting of the digits of the decimal representation of n (in order, with no leading zeroes).
      result.formatted_string = n == 0.0 ? String("0"sv) : Value(n).to_string_without_side_effects();
  
      // 5. If f ≠ 0, then
      if (fraction != 0) {
          // a. Let k be the number of characters in m.
          auto decimals = result.formatted_string.length();
  
          // b. If k ≤ f, then
          if (decimals <= static_cast<size_t>(fraction)) {
              // i. Let z be the String value consisting of f+1–k occurrences of the character "0".
              auto zeroes = String::repeated('0', fraction + 1 - decimals);
  
              // ii. Let m be the string-concatenation of z and m.
              result.formatted_string = String::formatted("{}{}", zeroes, result.formatted_string);
  
              // iii. Let k be f+1.
              decimals = fraction + 1;
          }
  
          // c. Let a be the first k–f characters of m, and let b be the remaining f characters of m.
          auto a = result.formatted_string.substring_view(0, decimals - fraction);
          auto b = result.formatted_string.substring_view(decimals - fraction, fraction);
  
          // d. Let m be the string-concatenation of a, ".", and b.
          result.formatted_string = String::formatted("{}.{}", a, b);
  
          // e. Let int be the number of characters in a.
          result.digits = a.length();
      }
      // 6. Else, let int be the number of characters in m.
      else {
          result.digits = result.formatted_string.length();
      }
  
      // 7. Let cut be maxFraction – minFraction.
      int cut = max_fraction - min_fraction;
  
      result.formatted_string = cut_trailing_zeroes(result.formatted_string, cut);
  
      // 10. Return the Record { [[FormattedString]]: m, [[RoundedNumber]]: xFinal, [[IntegerDigitsCount]]: int }.
      return result;
  }
  
  // 15.1.13 SetNumberFormatUnitOptions ( intlObj, options ), https://tc39.es/ecma402/#sec-setnumberformatunitoptions
  ThrowCompletionOr<void> set_number_format_unit_options(GlobalObject& global_object, NumberFormat& intl_object, Object const& options)
  {
      auto& vm = global_object.vm();
  
      // 1. Assert: Type(intlObj) is Object.
      // 2. Assert: Type(options) is Object.
  
      // 3. Let style be ? GetOption(options, "style", "string", « "decimal", "percent", "currency", "unit" », "decimal").
      auto style = TRY(get_option(global_object, options, vm.names.style, Value::Type::String, { "decimal"sv, "percent"sv, "currency"sv, "unit"sv }, "decimal"sv));
  
      // 4. Set intlObj.[[Style]] to style.
      intl_object.set_style(style.as_string().string());
  
      // 5. Let currency be ? GetOption(options, "currency", "string", undefined, undefined).
      auto currency = TRY(get_option(global_object, options, vm.names.currency, Value::Type::String, {}, Empty {}));
  
      // 6. If currency is undefined, then
      if (currency.is_undefined()) {
          // a. If style is "currency", throw a TypeError exception.
          if (intl_object.style() == NumberFormat::Style::Currency)
              return vm.throw_completion<TypeError>(global_object, ErrorType::IntlOptionUndefined, "currency"sv, "style"sv, style);
      }
      // 7. Else,
      //     a. If the result of IsWellFormedCurrencyCode(currency) is false, throw a RangeError exception.
      else if (!is_well_formed_currency_code(currency.as_string().string()))
          return vm.throw_completion<RangeError>(global_object, ErrorType::OptionIsNotValidValue, currency, "currency"sv);
  
      // 8. Let currencyDisplay be ? GetOption(options, "currencyDisplay", "string", « "code", "symbol", "narrowSymbol", "name" », "symbol").
      auto currency_display = TRY(get_option(global_object, options, vm.names.currencyDisplay, Value::Type::String, { "code"sv, "symbol"sv, "narrowSymbol"sv, "name"sv }, "symbol"sv));
  
      // 9. Let currencySign be ? GetOption(options, "currencySign", "string", « "standard", "accounting" », "standard").
      auto currency_sign = TRY(get_option(global_object, options, vm.names.currencySign, Value::Type::String, { "standard"sv, "accounting"sv }, "standard"sv));
  
      // 10. Let unit be ? GetOption(options, "unit", "string", undefined, undefined).
      auto unit = TRY(get_option(global_object, options, vm.names.unit, Value::Type::String, {}, Empty {}));
  
      // 11. If unit is undefined, then
      if (unit.is_undefined()) {
          // a. If style is "unit", throw a TypeError exception.
          if (intl_object.style() == NumberFormat::Style::Unit)
              return vm.throw_completion<TypeError>(global_object, ErrorType::IntlOptionUndefined, "unit"sv, "style"sv, style);
      }
      // 12. Else,
      //     a. If the result of IsWellFormedUnitIdentifier(unit) is false, throw a RangeError exception.
      else if (!is_well_formed_unit_identifier(unit.as_string().string()))
          return vm.throw_completion<RangeError>(global_object, ErrorType::OptionIsNotValidValue, unit, "unit"sv);
  
      // 13. Let unitDisplay be ? GetOption(options, "unitDisplay", "string", « "short", "narrow", "long" », "short").
      auto unit_display = TRY(get_option(global_object, options, vm.names.unitDisplay, Value::Type::String, { "short"sv, "narrow"sv, "long"sv }, "short"sv));
  
      // 14. If style is "currency", then
      if (intl_object.style() == NumberFormat::Style::Currency) {
          // a. Let currency be the result of converting currency to upper case as specified in 6.1.
          // b. Set intlObj.[[Currency]] to currency.
          intl_object.set_currency(currency.as_string().string().to_uppercase());
  
          // c. Set intlObj.[[CurrencyDisplay]] to currencyDisplay.
          intl_object.set_currency_display(currency_display.as_string().string());
  
          // d. Set intlObj.[[CurrencySign]] to currencySign.
          intl_object.set_currency_sign(currency_sign.as_string().string());
      }
  
      // 15. If style is "unit", then
      if (intl_object.style() == NumberFormat::Style::Unit) {
          // a. Set intlObj.[[Unit]] to unit.
          intl_object.set_unit(unit.as_string().string());
  
          // b. Set intlObj.[[UnitDisplay]] to unitDisplay.
          intl_object.set_unit_display(unit_display.as_string().string());
      }
  
      return {};
  }
  
  // 15.1.14 GetNumberFormatPattern ( numberFormat, x ), https://tc39.es/ecma402/#sec-getnumberformatpattern
  Optional<Variant<StringView, String>> get_number_format_pattern(NumberFormat& number_format, double number, Unicode::NumberFormat& found_pattern)
  {
      // 1. Let localeData be %NumberFormat%.[[LocaleData]].
      // 2. Let dataLocale be numberFormat.[[DataLocale]].
      // 3. Let dataLocaleData be localeData.[[<dataLocale>]].
      // 4. Let patterns be dataLocaleData.[[patterns]].
      // 5. Assert: patterns is a Record (see 15.3.3).
      Optional<Unicode::NumberFormat> patterns;
  
      // 6. Let style be numberFormat.[[Style]].
      switch (number_format.style()) {
      // 7. If style is "percent", then
      case NumberFormat::Style::Percent:
          // a. Let patterns be patterns.[[percent]].
          patterns = Unicode::get_standard_number_system_format(number_format.data_locale(), number_format.numbering_system(), Unicode::StandardNumberFormatType::Percent);
          break;
  
      // 8. Else if style is "unit", then
      case NumberFormat::Style::Unit: {
          // a. Let unit be numberFormat.[[Unit]].
          // b. Let unitDisplay be numberFormat.[[UnitDisplay]].
          // c. Let patterns be patterns.[[unit]].
          // d. If patterns doesn't have a field [[<unit>]], then
          //     i. Let unit be "fallback".
          // e. Let patterns be patterns.[[<unit>]].
          // f. Let patterns be patterns.[[<unitDisplay>]].
          Vector<Unicode::NumberFormat> formats;
  
          switch (number_format.unit_display()) {
          case NumberFormat::UnitDisplay::Long:
              formats = Unicode::get_unit_formats(number_format.data_locale(), number_format.unit(), Unicode::Style::Long);
              break;
          case NumberFormat::UnitDisplay::Short:
              formats = Unicode::get_unit_formats(number_format.data_locale(), number_format.unit(), Unicode::Style::Short);
              break;
          case NumberFormat::UnitDisplay::Narrow:
              formats = Unicode::get_unit_formats(number_format.data_locale(), number_format.unit(), Unicode::Style::Narrow);
              break;
          }
  
          patterns = Unicode::select_pattern_with_plurality(formats, number);
          break;
      }
  
      // 9. Else if style is "currency", then
      case NumberFormat::Style::Currency:
          // a. Let currency be numberFormat.[[Currency]].
          // b. Let currencyDisplay be numberFormat.[[CurrencyDisplay]].
          // c. Let currencySign be numberFormat.[[CurrencySign]].
          // d. Let patterns be patterns.[[currency]].
          // e. If patterns doesn't have a field [[<currency>]], then
          //     i. Let currency be "fallback".
          // f. Let patterns be patterns.[[<currency>]].
          // g. Let patterns be patterns.[[<currencyDisplay>]].
          // h. Let patterns be patterns.[[<currencySign>]].
  
          // Handling of other [[CurrencyDisplay]] options will occur after [[SignDisplay]].
          if (number_format.currency_display() == NumberFormat::CurrencyDisplay::Name) {
              auto formats = Unicode::get_compact_number_system_formats(number_format.data_locale(), number_format.numbering_system(), Unicode::CompactNumberFormatType::CurrencyUnit);
  
              auto maybe_patterns = Unicode::select_pattern_with_plurality(formats, number);
              if (maybe_patterns.has_value()) {
                  patterns = maybe_patterns.release_value();
                  break;
              }
          }
  
          switch (number_format.currency_sign()) {
          case NumberFormat::CurrencySign::Standard:
              patterns = Unicode::get_standard_number_system_format(number_format.data_locale(), number_format.numbering_system(), Unicode::StandardNumberFormatType::Currency);
              break;
          case NumberFormat::CurrencySign::Accounting:
              patterns = Unicode::get_standard_number_system_format(number_format.data_locale(), number_format.numbering_system(), Unicode::StandardNumberFormatType::Accounting);
              break;
          }
  
          break;
  
      // 10. Else,
      case NumberFormat::Style::Decimal:
          // a. Assert: style is "decimal".
          // b. Let patterns be patterns.[[decimal]].
          patterns = Unicode::get_standard_number_system_format(number_format.data_locale(), number_format.numbering_system(), Unicode::StandardNumberFormatType::Decimal);
          break;
  
      default:
          VERIFY_NOT_REACHED();
      }
  
      if (!patterns.has_value())
          return {};
  
      StringView pattern;
  
      Value number_value(number);
      bool is_positive_zero = number_value.is_positive_zero();
      bool is_negative_zero = number_value.is_negative_zero();
      bool is_nan = number_value.is_nan();
  
      // 11. Let signDisplay be numberFormat.[[SignDisplay]].
      switch (number_format.sign_display()) {
      // 12. If signDisplay is "never", then
      case NumberFormat::SignDisplay::Never:
          // a. Let pattern be patterns.[[zeroPattern]].
          pattern = patterns->zero_format;
          break;
  
      // 13. Else if signDisplay is "auto", then
      case NumberFormat::SignDisplay::Auto:
          // a. If x is 0 or x > 0 or x is NaN, then
          if (is_positive_zero || (number > 0) || is_nan) {
              // i. Let pattern be patterns.[[zeroPattern]].
              pattern = patterns->zero_format;
          }
          // b. Else,
          else {
              // i. Let pattern be patterns.[[negativePattern]].
              pattern = patterns->negative_format;
          }
          break;
  
      // 14. Else if signDisplay is "always", then
      case NumberFormat::SignDisplay::Always:
          // a. If x is 0 or x > 0 or x is NaN, then
          if (is_positive_zero || (number > 0) || is_nan) {
              // i. Let pattern be patterns.[[positivePattern]].
              pattern = patterns->positive_format;
          }
          // b. Else,
          else {
              // i. Let pattern be patterns.[[negativePattern]].
              pattern = patterns->negative_format;
          }
          break;
  
      // 15. Else,
      case NumberFormat::SignDisplay::ExceptZero:
          // a. Assert: signDisplay is "exceptZero".
          // b. If x is 0 or x is -0 or x is NaN, then
          if (is_positive_zero || is_negative_zero || is_nan) {
              // i. Let pattern be patterns.[[zeroPattern]].
              pattern = patterns->zero_format;
          }
          // c. Else if x > 0, then
          else if (number > 0) {
              // i. Let pattern be patterns.[[positivePattern]].
              pattern = patterns->positive_format;
          }
          // d. Else,
          else {
              // i. Let pattern be patterns.[[negativePattern]].
              pattern = patterns->negative_format;
          }
          break;
  
      default:
          VERIFY_NOT_REACHED();
      }
  
      found_pattern = patterns.release_value();
  
      // Handling of steps 9b/9g: Depending on the currency display and the format pattern found above,
      // we might need to mutate the format pattern to inject a space between the currency display and
      // the currency number.
      if (number_format.style() == NumberFormat::Style::Currency) {
          auto modified_pattern = Unicode::augment_currency_format_pattern(number_format.resolve_currency_display(), pattern);
          if (modified_pattern.has_value())
              return modified_pattern.release_value();
      }
  
      // 16. Return pattern.
      return pattern;
  }
  
  // 15.1.15 GetNotationSubPattern ( numberFormat, exponent ), https://tc39.es/ecma402/#sec-getnotationsubpattern
  Optional<StringView> get_notation_sub_pattern(NumberFormat& number_format, int exponent)
  {
      // 1. Let localeData be %NumberFormat%.[[LocaleData]].
      // 2. Let dataLocale be numberFormat.[[DataLocale]].
      // 3. Let dataLocaleData be localeData.[[<dataLocale>]].
      // 4. Let notationSubPatterns be dataLocaleData.[[notationSubPatterns]].
      // 5. Assert: notationSubPatterns is a Record (see 15.3.3).
  
      // 6. Let notation be numberFormat.[[Notation]].
      auto notation = number_format.notation();
  
      // 7. If notation is "scientific" or notation is "engineering", then
      if ((notation == NumberFormat::Notation::Scientific) || (notation == NumberFormat::Notation::Engineering)) {
          // a. Return notationSubPatterns.[[scientific]].
          auto notation_sub_patterns = Unicode::get_standard_number_system_format(number_format.data_locale(), number_format.numbering_system(), Unicode::StandardNumberFormatType::Scientific);
          if (!notation_sub_patterns.has_value())
              return {};
  
          return notation_sub_patterns->zero_format;
      }
      // 8. Else if exponent is not 0, then
      else if (exponent != 0) {
          // a. Assert: notation is "compact".
          VERIFY(notation == NumberFormat::Notation::Compact);
  
          // b. Let compactDisplay be numberFormat.[[CompactDisplay]].
          // c. Let compactPatterns be notationSubPatterns.[[compact]].[[<compactDisplay>]].
          // d. Return compactPatterns.[[<exponent>]].
          if (number_format.has_compact_format())
              return number_format.compact_format().zero_format;
      }
  
      // 9. Else,
      //     a. Return "{number}".
      return "{number}"sv;
  }
  
  // 15.1.16 ComputeExponent ( numberFormat, x ), https://tc39.es/ecma402/#sec-computeexponent
  int compute_exponent(NumberFormat& number_format, double number)
  {
      // 1. If x = 0, then
      if (number == 0.0) {
          // a. Return 0.
          return 0;
      }
  
      // 2. If x < 0, then
      if (number < 0) {
          // a. Let x = -x.
          number *= -1;
      }
  
      // 3. Let magnitude be the base 10 logarithm of x rounded down to the nearest integer.
      int magnitude = log10floor(number);
  
      // 4. Let exponent be ComputeExponentForMagnitude(numberFormat, magnitude).
      int exponent = compute_exponent_for_magniude(number_format, magnitude);
  
      // 5. Let x be x × 10^(-exponent).
      number *= pow(10, -exponent);
  
      // 6. Let formatNumberResult be FormatNumericToString(numberFormat, x).
      auto format_number_result = format_numeric_to_string(number_format, number);
  
      // 7. If formatNumberResult.[[RoundedNumber]] = 0, then
      if (format_number_result.rounded_number == 0) {
          // a. Return exponent.
          return exponent;
      }
  
      // 8. Let newMagnitude be the base 10 logarithm of formatNumberResult.[[RoundedNumber]] rounded down to the nearest integer.
      int new_magnitude = log10floor(format_number_result.rounded_number);
  
      // 9. If newMagnitude is magnitude – exponent, then
      if (new_magnitude == magnitude - exponent) {
          // a. Return exponent.
          return exponent;
      }
  
      // 10. Return ComputeExponentForMagnitude(numberFormat, magnitude + 1).
      return compute_exponent_for_magniude(number_format, magnitude + 1);
  }
  
  // 15.1.17 ComputeExponentForMagnitude ( numberFormat, magnitude ), https://tc39.es/ecma402/#sec-computeexponentformagnitude
  int compute_exponent_for_magniude(NumberFormat& number_format, int magnitude)
  {
      // 1. Let notation be numberFormat.[[Notation]].
      switch (number_format.notation()) {
      // 2. If notation is "standard", then
      case NumberFormat::Notation::Standard:
          // a. Return 0.
          return 0;
  
      // 3. Else if notation is "scientific", then
      case NumberFormat::Notation::Scientific:
          // a. Return magnitude.
          return magnitude;
  
      // 4. Else if notation is "engineering", then
      case NumberFormat::Notation::Engineering: {
          // a. Let thousands be the greatest integer that is not greater than magnitude / 3.
          double thousands = floor(static_cast<double>(magnitude) / 3.0);
  
          // b. Return thousands × 3.
          return static_cast<int>(thousands) * 3;
      }
  
      // 5. Else,
      case NumberFormat::Notation::Compact: {
          // a. Assert: notation is "compact".
          VERIFY(number_format.has_compact_display());
  
          // b. Let exponent be an implementation- and locale-dependent (ILD) integer by which to scale a number of the given magnitude in compact notation for the current locale.
          // c. Return exponent.
          Vector<Unicode::NumberFormat> format_rules;
  
          if (number_format.style() == NumberFormat::Style::Currency)
              format_rules = Unicode::get_compact_number_system_formats(number_format.data_locale(), number_format.numbering_system(), Unicode::CompactNumberFormatType::CurrencyShort);
          else if (number_format.compact_display() == NumberFormat::CompactDisplay::Long)
              format_rules = Unicode::get_compact_number_system_formats(number_format.data_locale(), number_format.numbering_system(), Unicode::CompactNumberFormatType::DecimalLong);
          else
              format_rules = Unicode::get_compact_number_system_formats(number_format.data_locale(), number_format.numbering_system(), Unicode::CompactNumberFormatType::DecimalShort);
  
          Unicode::NumberFormat const* best_number_format = nullptr;
  
          for (auto const& format_rule : format_rules) {
              if (format_rule.magnitude > magnitude)
                  break;
              best_number_format = &format_rule;
          }
  
          if (best_number_format == nullptr)
              return 0;
  
          number_format.set_compact_format(*best_number_format);
          return best_number_format->exponent;
      }
  
      default:
          VERIFY_NOT_REACHED();
      }
  }
  
  }
  