1 files changed, 221 insertions, 0 deletions
diff --git a/intl/components/src/PluralRules.h b/intl/components/src/PluralRules.h
new file mode 100644
index 0000000000..a413d54279
--- /dev/null
+++ b/intl/components/src/PluralRules.h
@@ -0,0 +1,221 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef intl_components_PluralRules_h_
+#define intl_components_PluralRules_h_
+
+#include <string_view>
+#include <type_traits>
+#include <utility>
+
+#include "mozilla/intl/ICUError.h"
+#include "mozilla/intl/NumberFormat.h"
+#include "mozilla/intl/NumberRangeFormat.h"
+#include "mozilla/EnumSet.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "mozilla/Span.h"
+
+#include "unicode/utypes.h"
+
+namespace mozilla::intl {
+
+class PluralRules final {
+ public:
+  /**
+   * The set of keywords that a PluralRules object uses.
+   *
+   * https://tc39.es/ecma402/#sec-intl.pluralrules.prototype.resolvedoptions
+   */
+  enum class Keyword : uint8_t {
+    Few,
+    Many,
+    One,
+    Other,
+    Two,
+    Zero,
+  };
+
+  /**
+   * The two different types of PluralRules objects that can be created.
+   *
+   * https://tc39.es/ecma402/#sec-properties-of-intl-pluralrules-instances
+   */
+  enum class Type : uint8_t {
+    Cardinal,
+    Ordinal,
+  };
+
+  PluralRules(const PluralRules&) = delete;
+  PluralRules& operator=(const PluralRules&) = delete;
+
+  /**
+   * Attempts to construct a PluralRules with the given locale and options.
+   */
+  // TODO(1709880) use mozilla::Span instead of std::string_view.
+  static Result<UniquePtr<PluralRules>, ICUError> TryCreate(
+      std::string_view aLocale, const PluralRulesOptions& aOptions);
+
+  /**
+   * Returns the PluralRules keyword that corresponds to the |aNumber|.
+   *
+   * https://tc39.es/ecma402/#sec-intl.pluralrules.prototype.select
+   */
+  Result<PluralRules::Keyword, ICUError> Select(double aNumber) const;
+
+  /**
+   * Returns the PluralRules keyword that corresponds to the range from |aStart|
+   * to |aEnd|.
+   *
+   * https://tc39.es/ecma402/#sec-intl.pluralrules.prototype.selectrange
+   */
+  Result<PluralRules::Keyword, ICUError> SelectRange(double aStart,
+                                                     double aEnd) const;
+
+  /**
+   * Returns an EnumSet with the plural-rules categories that are supported by
+   * the locale that the PluralRules instance was created with.
+   */
+  Result<EnumSet<PluralRules::Keyword>, ICUError> Categories() const;
+
+  ~PluralRules();
+
+ private:
+  // The longest keyword is "other"
+  static const size_t MAX_KEYWORD_LENGTH = 5;
+
+  UPluralRules* mPluralRules = nullptr;
+  UniquePtr<NumberFormat> mNumberFormat;
+  UniquePtr<NumberRangeFormat> mNumberRangeFormat;
+
+  PluralRules(UPluralRules*&, UniquePtr<NumberFormat>&&,
+              UniquePtr<NumberRangeFormat>&&);
+
+  /**
+   * Returns the PluralRules::Keyword that matches the UTF-16 string.
+   * Strings must be [u"few", u"many", u"one", u"other", u"two", u"zero"]
+   */
+  static PluralRules::Keyword KeywordFromUtf16(Span<const char16_t> aKeyword);
+
+  /**
+   * Returns the PluralRules::Keyword that matches the ASCII string.
+   * Strings must be ["few", "many", "one", "other", "two", "zero"]
+   */
+  static PluralRules::Keyword KeywordFromAscii(Span<const char> aKeyword);
+};
+
+/**
+ * Options required for constructing a PluralRules object.
+ */
+struct MOZ_STACK_CLASS PluralRulesOptions {
+  /**
+   * Creates a NumberFormatOptions from the PluralRulesOptions.
+   */
+  NumberFormatOptions ToNumberFormatOptions() const {
+    NumberFormatOptions options;
+    options.mRoundingMode = NumberFormatOptions::RoundingMode::HalfExpand;
+
+    if (mFractionDigits.isSome()) {
+      options.mFractionDigits.emplace(mFractionDigits.ref());
+    }
+
+    if (mMinIntegerDigits.isSome()) {
+      options.mMinIntegerDigits.emplace(mMinIntegerDigits.ref());
+    }
+
+    if (mSignificantDigits.isSome()) {
+      options.mSignificantDigits.emplace(mSignificantDigits.ref());
+    }
+
+    options.mRoundingPriority =
+        NumberFormatOptions::RoundingPriority(mRoundingPriority);
+
+    return options;
+  }
+  /**
+   * Creates a NumberFormatOptions from the PluralRulesOptions.
+   */
+  NumberRangeFormatOptions ToNumberRangeFormatOptions() const {
+    NumberRangeFormatOptions options;
+    options.mRoundingMode = NumberRangeFormatOptions::RoundingMode::HalfExpand;
+    options.mRangeCollapse = NumberRangeFormatOptions::RangeCollapse::None;
+    options.mRangeIdentityFallback =
+        NumberRangeFormatOptions::RangeIdentityFallback::Range;
+
+    if (mFractionDigits.isSome()) {
+      options.mFractionDigits.emplace(mFractionDigits.ref());
+    }
+
+    if (mMinIntegerDigits.isSome()) {
+      options.mMinIntegerDigits.emplace(mMinIntegerDigits.ref());
+    }
+
+    if (mSignificantDigits.isSome()) {
+      options.mSignificantDigits.emplace(mSignificantDigits.ref());
+    }
+
+    options.mRoundingPriority =
+        NumberFormatOptions::RoundingPriority(mRoundingPriority);
+
+    return options;
+  }
+
+  /**
+   * Set the plural type between cardinal and ordinal.
+   *
+   * https://tc39.es/ecma402/#sec-intl.pluralrules.prototype.resolvedoptions
+   */
+  PluralRules::Type mPluralType = PluralRules::Type::Cardinal;
+
+  /**
+   * Set the minimum number of integer digits. |min| must be a non-zero
+   * number.
+   *
+   * https://tc39.es/ecma402/#sec-intl.pluralrules.prototype.resolvedoptions
+   */
+  Maybe<uint32_t> mMinIntegerDigits;
+
+  /**
+   * Set the fraction digits settings. |min| can be zero, |max| must be
+   * larger-or-equal to |min|.
+   *
+   * https://tc39.es/ecma402/#sec-intl.pluralrules.prototype.resolvedoptions
+   */
+  Maybe<std::pair<uint32_t, uint32_t>> mFractionDigits;
+
+  /**
+   * Set the significant digits settings. |min| must be a non-zero number, |max|
+   * must be larger-or-equal to |min|.
+   *
+   * https://tc39.es/ecma402/#sec-intl.pluralrules.prototype.resolvedoptions
+   */
+  Maybe<std::pair<uint32_t, uint32_t>> mSignificantDigits;
+
+  /**
+   * Set the rounding priority. |mFractionDigits| and |mSignificantDigits| must
+   * both be set if the rounding priority isn't equal to "auto".
+   */
+  enum class RoundingPriority {
+    Auto,
+    MorePrecision,
+    LessPrecision,
+  } mRoundingPriority = RoundingPriority::Auto;
+
+  // Must be compatible with NumberFormatOptions::RoundingPriority.
+  static_assert(std::is_same_v<
+                std::underlying_type_t<RoundingPriority>,
+                std::underlying_type_t<NumberFormatOptions::RoundingPriority>>);
+  static_assert(RoundingPriority::Auto ==
+                RoundingPriority(NumberFormatOptions::RoundingPriority::Auto));
+  static_assert(
+      RoundingPriority::LessPrecision ==
+      RoundingPriority(NumberFormatOptions::RoundingPriority::LessPrecision));
+  static_assert(
+      RoundingPriority::MorePrecision ==
+      RoundingPriority(NumberFormatOptions::RoundingPriority::MorePrecision));
+};
+
+}  // namespace mozilla::intl
+
+#endif