Method readAccessToken

ui-linux/src/backend.cpp:796–893

}

QString Backend::readAccessToken() const
{
    QString tokenPath;
    if (m_providerName == "gdrive") {
        tokenPath = m_providerPath.isEmpty() ? defaultTokenPath("gdrive") : m_providerPath;
    } else if (m_providerName == "onedrive") {
        tokenPath = m_providerPath.isEmpty() ? defaultTokenPath("onedrive") : m_providerPath;
    } else {
        return QString();
    }
    
    QFile f(tokenPath);
    if (!f.open(QIODevice::ReadOnly)) return QString();
    
    QJsonDocument doc = QJsonDocument::fromJson(f.readAll());
    f.close();
    QJsonObject obj = doc.object();
    
    // Check if token is expired and refresh if needed
    qint64 expiresAt = obj.value("expires_at").toInteger(0);
    if (expiresAt > 0 && QDateTime::currentSecsSinceEpoch() >= expiresAt - 60) {
        // Thread-safe re-entrancy guard
        static QAtomicInt s_refreshing{0};
        if (!s_refreshing.testAndSetAcquire(0, 1)) return QString();
        struct RefreshGuard {
            QAtomicInt& flag;
            RefreshGuard(QAtomicInt& f) : flag(f) {}
            ~RefreshGuard() { flag.storeRelease(0); }
        } guard(s_refreshing);
        
        QString refreshToken = obj.value("refresh_token").toString();
        if (refreshToken.isEmpty()) return QString();
        
        // Synchronous refresh with reduced timeout
        QNetworkAccessManager nam;
        QUrlQuery body;
        body.addQueryItem("client_id", m_providerName == "onedrive" ? ONEDRIVE_CLIENT_ID : GDRIVE_CLIENT_ID);
        body.addQueryItem("client_secret", m_providerName == "onedrive" ? ONEDRIVE_CLIENT_SECRET : GDRIVE_CLIENT_SECRET);
        body.addQueryItem("refresh_token", refreshToken);
        body.addQueryItem("grant_type", "refresh_token");
        if (m_providerName == "onedrive")
            body.addQueryItem("scope", "Files.ReadWrite offline_access");
        
        QNetworkRequest req(QUrl(m_providerName == "onedrive"
            ? "https://login.microsoftonline.com/common/oauth2/v2.0/token"
            : "https://oauth2.googleapis.com/token"));
        req.setHeader(QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencoded");
        
        // Retry up to 2 times (broken IPv6 fails instantly, retry gives IPv4 a chance)
        QNetworkReply *reply = nullptr;
        for (int attempt = 0; attempt < 3; ++attempt) {
            QEventLoop loop;
            QTimer timeout;
            timeout.setSingleShot(true);
            reply = nam.post(req, body.toString(QUrl::FullyEncoded).toUtf8());
            QObject::connect(reply, &QNetworkReply::finished, &loop, &QEventLoop::quit);
            QObject::connect(&timeout, &QTimer::timeout, reply, &QNetworkReply::abort);
            timeout.start(10000);