flutter_flutter/sky/engine/platform/Language.cpp

/*
 * Copyright (C) 2010, 2013 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
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#include "flutter/sky/engine/platform/Language.h"

#include "flutter/sky/engine/public/platform/Platform.h"
#include "flutter/sky/engine/wtf/text/WTFString.h"

namespace blink {

static const AtomicString& platformLanguage() {
  DEFINE_STATIC_LOCAL(AtomicString, computedDefaultLanguage, ());
  if (computedDefaultLanguage.isEmpty()) {
    std::string defaultLocale = blink::Platform::current()->defaultLocale();
    computedDefaultLanguage =
        AtomicString::fromUTF8(defaultLocale.data(), defaultLocale.size());
    ASSERT(!computedDefaultLanguage.isEmpty());
  }
  return computedDefaultLanguage;
}

AtomicString defaultLanguage() {
  Vector<AtomicString> languages = userPreferredLanguages();
  if (!languages.isEmpty())
    return languages[0];

  return emptyAtom;
}

static Vector<AtomicString>& preferredLanguagesOverride() {
  DEFINE_STATIC_LOCAL(Vector<AtomicString>, override, ());
  return override;
}

Vector<AtomicString> userPreferredLanguagesOverride() {
  return preferredLanguagesOverride();
}

void overrideUserPreferredLanguages(const Vector<AtomicString>& override) {
  preferredLanguagesOverride() = override;
}

Vector<AtomicString> userPreferredLanguages() {
  Vector<AtomicString>& override = preferredLanguagesOverride();
  if (!override.isEmpty())
    return override;

  Vector<AtomicString> languages;
  languages.reserveInitialCapacity(1);
  languages.append(platformLanguage());
  return languages;
}

static String canonicalLanguageIdentifier(const String& languageCode) {
  String lowercaseLanguageCode = languageCode.lower();

  if (lowercaseLanguageCode.length() >= 3 && lowercaseLanguageCode[2] == '_')
    lowercaseLanguageCode.replace(2, 1, "-");

  return lowercaseLanguageCode;
}

size_t indexOfBestMatchingLanguageInList(
    const AtomicString& language,
    const Vector<AtomicString>& languageList) {
  AtomicString languageWithoutLocaleMatch;
  AtomicString languageMatchButNotLocale;
  size_t languageWithoutLocaleMatchIndex = 0;
  size_t languageMatchButNotLocaleMatchIndex = 0;
  bool canMatchLanguageOnly = (language.length() == 2 ||
                               (language.length() >= 3 && language[2] == '-'));

  for (size_t i = 0; i < languageList.size(); ++i) {
    String canonicalizedLanguageFromList =
        canonicalLanguageIdentifier(languageList[i]);

    if (language == canonicalizedLanguageFromList)
      return i;

    if (canMatchLanguageOnly && canonicalizedLanguageFromList.length() >= 2) {
      if (language[0] == canonicalizedLanguageFromList[0] &&
          language[1] == canonicalizedLanguageFromList[1]) {
        if (!languageWithoutLocaleMatch.length() &&
            canonicalizedLanguageFromList.length() == 2) {
          languageWithoutLocaleMatch = languageList[i];
          languageWithoutLocaleMatchIndex = i;
        }
        if (!languageMatchButNotLocale.length() &&
            canonicalizedLanguageFromList.length() >= 3) {
          languageMatchButNotLocale = languageList[i];
          languageMatchButNotLocaleMatchIndex = i;
        }
      }
    }
  }

  // If we have both a language-only match and a languge-but-not-locale match,
  // return the languge-only match as is considered a "better" match. For
  // example, if the list provided has both "en-GB" and "en" and the user
  // prefers "en-US" we will return "en".
  if (languageWithoutLocaleMatch.length())
    return languageWithoutLocaleMatchIndex;

  if (languageMatchButNotLocale.length())
    return languageMatchButNotLocaleMatchIndex;

  return languageList.size();
}

}  // namespace blink