tubestation/intl/components/src/DateTimePatternGenerator.h

/* 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_DateTimePatternGenerator_h_
#define intl_components_DateTimePatternGenerator_h_

#include "unicode/udatpg.h"
#include "mozilla/EnumSet.h"
#include "mozilla/Result.h"
#include "mozilla/Span.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/intl/ICU4CGlue.h"
#include "mozilla/intl/ICUError.h"

namespace mozilla::intl {

class DisplayNames;

/**
 * The DateTimePatternGenerator is the machinery used to work with DateTime
 * pattern manipulation. It is expensive to create one, and so generally it is
 * created once and then cached. It may be needed to be passed in as an argument
 * for different mozilla::intl APIs.
 */
class DateTimePatternGenerator final {
 public:
  explicit DateTimePatternGenerator(UDateTimePatternGenerator* aGenerator)
      : mGenerator(aGenerator) {
    MOZ_ASSERT(aGenerator);
  };

  // Transfer ownership of the UDateTimePatternGenerator in the move
  // constructor.
  DateTimePatternGenerator(DateTimePatternGenerator&& other) noexcept;

  // Transfer ownership of the UEnumeration in the move assignment operator.
  DateTimePatternGenerator& operator=(
      DateTimePatternGenerator&& other) noexcept;

  // Disallow copy.
  DateTimePatternGenerator(const DateTimePatternGenerator&) = delete;
  DateTimePatternGenerator& operator=(const DateTimePatternGenerator&) = delete;

  ~DateTimePatternGenerator();

  static Result<UniquePtr<DateTimePatternGenerator>, ICUError> TryCreate(
      const char* aLocale);

  enum class PatternMatchOption {
    /**
     * Adjust the 'hour' field in the resolved pattern to match the input
     * skeleton width.
     */
    HourField,

    /**
     * Adjust the 'minute' field in the resolved pattern to match the input
     * skeleton width.
     */
    MinuteField,

    /**
     * Adjust the 'second' field in the resolved pattern to match the input
     * skeleton width.
     */
    SecondField,
  };

  /**
   * Given a skeleton (a string with unordered datetime fields), get a best
   * pattern that will fit for that locale. This pattern will be filled into the
   * buffer. e.g. The skeleton "yMd" would return the pattern "M/d/y" for en-US,
   * or "dd/MM/y" for en-GB.
   */
  template <typename B>
  ICUResult GetBestPattern(Span<const char16_t> aSkeleton, B& aBuffer,
                           EnumSet<PatternMatchOption> options = {}) {
    return FillBufferWithICUCall(
        aBuffer, [&](UChar* target, int32_t length, UErrorCode* status) {
          return udatpg_getBestPatternWithOptions(
              mGenerator.GetMut(), aSkeleton.data(),
              static_cast<int32_t>(aSkeleton.Length()),
              toUDateTimePatternMatchOptions(options), target, length, status);
        });
  }

  /**
   * Get a skeleton (a string with unordered datetime fields) from a pattern.
   * For example, both "MMM-dd" and "dd/MMM" produce the skeleton "MMMdd".
   */
  template <typename B>
  static ICUResult GetSkeleton(Span<const char16_t> aPattern, B& aBuffer) {
    // At one time udatpg_getSkeleton required a UDateTimePatternGenerator*, but
    // now it is valid to pass in a nullptr.
    return FillBufferWithICUCall(
        aBuffer, [&](UChar* target, int32_t length, UErrorCode* status) {
          return udatpg_getSkeleton(nullptr, aPattern.data(),
                                    static_cast<int32_t>(aPattern.Length()),
                                    target, length, status);
        });
  }

  /**
   * Get a pattern of the form "{1} {0}" to combine separate date and time
   * patterns into a single pattern. The "{0}" part is the placeholder for the
   * time pattern and "{1}" is the placeholder for the date pattern.
   *
   * See dateTimeFormat from
   * https://unicode.org/reports/tr35/tr35-dates.html#dateTimeFormat
   *
   * Note:
   * In CLDR, it's called Date-Time Combined Format
   * https://cldr.unicode.org/translation/date-time/datetime-patterns#h.x7ca7qwzh4m
   *
   * The naming 'placeholder pattern' is from ICU4X.
   * https://unicode-org.github.io/icu4x-docs/doc/icu_pattern/index.html
   */
  Span<const char16_t> GetPlaceholderPattern() const {
    int32_t length;
    const char16_t* combined =
        udatpg_getDateTimeFormat(mGenerator.GetConst(), &length);
    return Span{combined, static_cast<size_t>(length)};
  }

 private:
  // Allow other mozilla::intl components to access the underlying
  // UDateTimePatternGenerator.
  friend class DisplayNames;

  UDateTimePatternGenerator* GetUDateTimePatternGenerator() {
    return mGenerator.GetMut();
  }

  ICUPointer<UDateTimePatternGenerator> mGenerator =
      ICUPointer<UDateTimePatternGenerator>(nullptr);

  static UDateTimePatternMatchOptions toUDateTimePatternMatchOptions(
      EnumSet<PatternMatchOption> options) {
    struct OptionMap {
      PatternMatchOption from;
      UDateTimePatternMatchOptions to;
    } static constexpr map[] = {
        {PatternMatchOption::HourField, UDATPG_MATCH_HOUR_FIELD_LENGTH},
#ifndef U_HIDE_INTERNAL_API
        {PatternMatchOption::MinuteField, UDATPG_MATCH_MINUTE_FIELD_LENGTH},
        {PatternMatchOption::SecondField, UDATPG_MATCH_SECOND_FIELD_LENGTH},
#endif
    };

    UDateTimePatternMatchOptions result = UDATPG_MATCH_NO_OPTIONS;
    for (const auto& entry : map) {
      if (options.contains(entry.from)) {
        result = UDateTimePatternMatchOptions(result | entry.to);
      }
    }
    return result;
  }
};

}  // namespace mozilla::intl
#endif