flutter_flutter/sky/engine/platform/Language.cpp

/*
 * Copyright (C) 2010, 2013 Apple Inc. All rights reserved.
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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();
}

}