feat: seeking support and Last.fm scrobbling

Seeking:
- Rust player: seek_requested/seek_target_secs atomics on PlayerStatus
- Decoder loop checks for seek each iteration, calls format.seek() and resets decoder
- New qobuz_backend_seek C FFI + QobuzBackend::seek(quint64)
- Progress slider onProgressReleased now seeks to the dragged position

Last.fm:
- LastFmScrobbler: now-playing + scrobble (50% or 240s threshold, min 30s)
- API signature follows Last.fm spec (sorted params, md5)
- Settings dialog: API key/secret, username/password, Connect button with status
- AppSettings: lastfm/enabled, api_key, api_secret, session_key
- Scrobbler wired to trackChanged, positionChanged, trackFinished in MainWindow

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/CMakeLists.txt

@@ -44,6 +44,9 @@ target_sources(qobuz-qt PRIVATE
     dialog/settings.hpp
     dialog/settings.cpp
 
+    # Scrobbler (header-only)
+    scrobbler/lastfm.hpp
+
     # Widgets (header-only)
     widget/clickableslider.hpp
     widget/volumebutton.hpp

src/backend/qobuzbackend.cpp

@@ -128,6 +128,11 @@ void QobuzBackend::setVolume(int volume)
     qobuz_backend_set_volume(m_backend, static_cast<quint8>(qBound(0, volume, 100)));
 }
 
+void QobuzBackend::seek(quint64 positionSecs)
+{
+    qobuz_backend_seek(m_backend, positionSecs);
+}
+
 quint64 QobuzBackend::position() const { return qobuz_backend_get_position(m_backend); }
 quint64 QobuzBackend::duration() const { return qobuz_backend_get_duration(m_backend); }
 int     QobuzBackend::volume()   const { return qobuz_backend_get_volume(m_backend); }

src/backend/qobuzbackend.hpp

@@ -48,6 +48,7 @@ public:
     void resume();
     void stop();
     void setVolume(int volume);
+    void seek(quint64 positionSecs);
 
     quint64 position() const;
     quint64 duration() const;

src/dialog/settings.cpp

@@ -1,15 +1,20 @@
 #include "settings.hpp"
 #include "../util/settings.hpp"
+#include "../scrobbler/lastfm.hpp"
 
 #include <QVBoxLayout>
 #include <QFormLayout>
 #include <QDialogButtonBox>
 #include <QGroupBox>
+#include <QHBoxLayout>
+#include <QNetworkReply>
 
 SettingsDialog::SettingsDialog(QWidget *parent) : QDialog(parent)
 {
     setWindowTitle(tr("Settings"));
-    setMinimumWidth(400);
+    setMinimumWidth(420);
+
+    m_nam = new QNetworkAccessManager(this);
 
     auto *layout = new QVBoxLayout(this);
 
@@ -30,25 +35,98 @@ SettingsDialog::SettingsDialog(QWidget *parent) : QDialog(parent)
             break;
         }
     }
-
     playLayout->addRow(tr("Preferred quality:"), m_formatBox);
     layout->addWidget(playGroup);
 
+    // --- Last.fm group ---
+    auto *lfmGroup  = new QGroupBox(tr("Last.fm Scrobbling"), this);
+    auto *lfmLayout = new QFormLayout(lfmGroup);
+
+    m_lastFmEnabled = new QCheckBox(tr("Enable scrobbling"), lfmGroup);
+    m_lastFmEnabled->setChecked(AppSettings::instance().lastFmEnabled());
+    lfmLayout->addRow(m_lastFmEnabled);
+
+    m_lastFmApiKey = new QLineEdit(AppSettings::instance().lastFmApiKey(), lfmGroup);
+    m_lastFmApiKey->setPlaceholderText(tr("Get one at last.fm/api"));
+    lfmLayout->addRow(tr("API Key:"), m_lastFmApiKey);
+
+    m_lastFmApiSecret = new QLineEdit(AppSettings::instance().lastFmApiSecret(), lfmGroup);
+    m_lastFmApiSecret->setEchoMode(QLineEdit::Password);
+    lfmLayout->addRow(tr("API Secret:"), m_lastFmApiSecret);
+
+    m_lastFmUsername = new QLineEdit(lfmGroup);
+    m_lastFmUsername->setPlaceholderText(tr("Last.fm username"));
+    lfmLayout->addRow(tr("Username:"), m_lastFmUsername);
+
+    m_lastFmPassword = new QLineEdit(lfmGroup);
+    m_lastFmPassword->setEchoMode(QLineEdit::Password);
+    m_lastFmPassword->setPlaceholderText(tr("Last.fm password"));
+    lfmLayout->addRow(tr("Password:"), m_lastFmPassword);
+
+    auto *connectRow = new QHBoxLayout;
+    m_lastFmConnect = new QPushButton(tr("Connect"), lfmGroup);
+    m_lastFmStatus  = new QLabel(lfmGroup);
+
+    const bool hasSession = !AppSettings::instance().lastFmSessionKey().isEmpty();
+    m_lastFmStatus->setText(hasSession ? tr("Connected ✓") : tr("Not connected"));
+    m_lastFmStatus->setStyleSheet(hasSession ? "color: green;" : "color: gray;");
+
+    connectRow->addWidget(m_lastFmConnect);
+    connectRow->addWidget(m_lastFmStatus, 1);
+    lfmLayout->addRow(connectRow);
+
+    layout->addWidget(lfmGroup);
     layout->addStretch();
 
     auto *buttons = new QDialogButtonBox(
         QDialogButtonBox::Ok | QDialogButtonBox::Cancel, this);
     layout->addWidget(buttons);
 
-    connect(buttons, &QDialogButtonBox::accepted, this, [this] {
-        applyChanges();
-        accept();
-    });
+    connect(m_lastFmConnect, &QPushButton::clicked, this, &SettingsDialog::onLastFmConnect);
+    connect(buttons, &QDialogButtonBox::accepted, this, [this] { applyChanges(); accept(); });
     connect(buttons, &QDialogButtonBox::rejected, this, &QDialog::reject);
 }
 
 void SettingsDialog::applyChanges()
 {
-    AppSettings::instance().setPreferredFormat(
-        m_formatBox->currentData().toInt());
+    AppSettings::instance().setPreferredFormat(m_formatBox->currentData().toInt());
+    AppSettings::instance().setLastFmEnabled(m_lastFmEnabled->isChecked());
+    AppSettings::instance().setLastFmApiKey(m_lastFmApiKey->text().trimmed());
+    AppSettings::instance().setLastFmApiSecret(m_lastFmApiSecret->text().trimmed());
+}
+
+void SettingsDialog::onLastFmConnect()
+{
+    const QString apiKey    = m_lastFmApiKey->text().trimmed();
+    const QString apiSecret = m_lastFmApiSecret->text().trimmed();
+    const QString username  = m_lastFmUsername->text().trimmed();
+    const QString password  = m_lastFmPassword->text();
+
+    if (apiKey.isEmpty() || apiSecret.isEmpty() || username.isEmpty() || password.isEmpty()) {
+        m_lastFmStatus->setText(tr("Fill in all fields first."));
+        m_lastFmStatus->setStyleSheet("color: red;");
+        return;
+    }
+
+    // Temporarily apply so the scrobbler util can use them for signing
+    AppSettings::instance().setLastFmApiKey(apiKey);
+    AppSettings::instance().setLastFmApiSecret(apiSecret);
+
+    m_lastFmConnect->setEnabled(false);
+    m_lastFmStatus->setText(tr("Connecting…"));
+    m_lastFmStatus->setStyleSheet("color: gray;");
+
+    // Reuse LastFmScrobbler::authenticate as a utility (temp instance)
+    auto *tmp = new LastFmScrobbler(this);
+    tmp->authenticate(username, password, [this, tmp](bool ok, const QString &err) {
+        tmp->deleteLater();
+        m_lastFmConnect->setEnabled(true);
+        if (ok) {
+            m_lastFmStatus->setText(tr("Connected ✓"));
+            m_lastFmStatus->setStyleSheet("color: green;");
+        } else {
+            m_lastFmStatus->setText(tr("Error: %1").arg(err));
+            m_lastFmStatus->setStyleSheet("color: red;");
+        }
+    });
 }

src/dialog/settings.hpp

@@ -3,6 +3,10 @@
 #include <QDialog>
 #include <QComboBox>
 #include <QLabel>
+#include <QLineEdit>
+#include <QCheckBox>
+#include <QPushButton>
+#include <QNetworkAccessManager>
 
 class SettingsDialog : public QDialog
 {
@@ -12,7 +16,19 @@ public:
     explicit SettingsDialog(QWidget *parent = nullptr);
 
 private:
+    // Playback
     QComboBox *m_formatBox = nullptr;
 
+    // Last.fm
+    QCheckBox  *m_lastFmEnabled    = nullptr;
+    QLineEdit  *m_lastFmApiKey     = nullptr;
+    QLineEdit  *m_lastFmApiSecret  = nullptr;
+    QLineEdit  *m_lastFmUsername   = nullptr;
+    QLineEdit  *m_lastFmPassword   = nullptr;
+    QPushButton *m_lastFmConnect   = nullptr;
+    QLabel      *m_lastFmStatus    = nullptr;
+    QNetworkAccessManager *m_nam   = nullptr;
+
     void applyChanges();
+    void onLastFmConnect();
 };

src/mainwindow.cpp

@@ -60,6 +60,15 @@ MainWindow::MainWindow(QobuzBackend *backend, QWidget *parent)
     setupMenuBar();
     statusBar()->showMessage(tr("Ready"));
 
+    // ---- Scrobbler ----
+    m_scrobbler = new LastFmScrobbler(this);
+    connect(m_backend, &QobuzBackend::trackChanged,
+            m_scrobbler, &LastFmScrobbler::onTrackStarted);
+    connect(m_backend, &QobuzBackend::positionChanged,
+            m_scrobbler, &LastFmScrobbler::onPositionChanged);
+    connect(m_backend, &QobuzBackend::trackFinished,
+            m_scrobbler, &LastFmScrobbler::onTrackFinished);
+
     // ---- Backend signals ----
     connect(m_backend, &QobuzBackend::loginSuccess,   this, &MainWindow::onLoginSuccess);
     connect(m_backend, &QobuzBackend::loginError,     this, &MainWindow::onLoginError);

src/mainwindow.hpp

@@ -8,6 +8,7 @@
 #include "view/queuepanel.hpp"
 #include "view/sidepanel/view.hpp"
 #include "list/library.hpp"
+#include "scrobbler/lastfm.hpp"
 
 #include <QMainWindow>
 #include <QDockWidget>
@@ -51,6 +52,7 @@ private:
     QueuePanel      *m_queuePanel  = nullptr;
     SidePanel::View *m_sidePanel   = nullptr;
     QDockWidget     *m_libraryDock = nullptr;
+    LastFmScrobbler *m_scrobbler   = nullptr;
 
     void setupMenuBar();
     void tryRestoreSession();

src/scrobbler/lastfm.hpp

@@ -0,0 +1,179 @@
+#pragma once
+
+#include "../util/settings.hpp"
+
+#include <QObject>
+#include <QNetworkAccessManager>
+#include <QNetworkReply>
+#include <QNetworkRequest>
+#include <QUrlQuery>
+#include <QUrl>
+#include <QCryptographicHash>
+#include <QDateTime>
+#include <QJsonDocument>
+#include <QJsonObject>
+#include <QMap>
+#include <functional>
+
+/// Handles Last.fm now-playing updates and scrobbling.
+/// Connect to QobuzBackend signals and call onTrackStarted / onPositionChanged / onTrackFinished.
+class LastFmScrobbler : public QObject
+{
+    Q_OBJECT
+
+public:
+    explicit LastFmScrobbler(QObject *parent = nullptr)
+        : QObject(parent)
+        , m_nam(new QNetworkAccessManager(this))
+    {}
+
+    /// Authenticate via auth.getMobileSession and store the session key.
+    /// callback(success, errorMessage)
+    void authenticate(const QString &username, const QString &password,
+                      std::function<void(bool, const QString &)> callback)
+    {
+        const QString apiKey    = AppSettings::instance().lastFmApiKey();
+        const QString apiSecret = AppSettings::instance().lastFmApiSecret();
+        if (apiKey.isEmpty() || apiSecret.isEmpty()) {
+            callback(false, tr("API key or secret is not set."));
+            return;
+        }
+
+        QMap<QString,QString> params;
+        params["method"]   = QStringLiteral("auth.getMobileSession");
+        params["api_key"]  = apiKey;
+        params["username"] = username;
+        params["password"] = password;
+        params["api_sig"]  = buildSig(params, apiSecret);
+        params["format"]   = QStringLiteral("json");
+
+        auto *reply = m_nam->post(apiRequest(), encodeBody(params));
+        connect(reply, &QNetworkReply::finished, this, [reply, callback] {
+            reply->deleteLater();
+            const QJsonObject obj = QJsonDocument::fromJson(reply->readAll()).object();
+            const QString key = obj["session"].toObject()["key"].toString();
+            if (!key.isEmpty()) {
+                AppSettings::instance().setLastFmSessionKey(key);
+                callback(true, {});
+            } else {
+                callback(false, obj["message"].toString(tr("Authentication failed.")));
+            }
+        });
+    }
+
+    bool isEnabled() const
+    {
+        return AppSettings::instance().lastFmEnabled()
+            && !AppSettings::instance().lastFmApiKey().isEmpty()
+            && !AppSettings::instance().lastFmApiSecret().isEmpty()
+            && !AppSettings::instance().lastFmSessionKey().isEmpty();
+    }
+
+public slots:
+    void onTrackStarted(const QJsonObject &track)
+    {
+        m_title    = track["title"].toString();
+        m_artist   = track["performer"].toObject()["name"].toString();
+        if (m_artist.isEmpty())
+            m_artist = track["album"].toObject()["artist"].toObject()["name"].toString();
+        m_album    = track["album"].toObject()["title"].toString();
+        m_duration = static_cast<qint64>(track["duration"].toDouble());
+        m_startTime   = QDateTime::currentSecsSinceEpoch();
+        m_playedSecs  = 0;
+        m_scrobbled   = false;
+
+        if (!isEnabled() || m_title.isEmpty() || m_duration < 30) return;
+        updateNowPlaying();
+    }
+
+    void onPositionChanged(quint64 positionSecs, quint64 /*duration*/)
+    {
+        m_playedSecs = positionSecs;
+        if (!isEnabled() || m_scrobbled || m_title.isEmpty() || m_duration < 30) return;
+        // Scrobble after 50% or 240 seconds played, whichever comes first, min 30 seconds.
+        const quint64 threshold = static_cast<quint64>(qMin((qint64)240, m_duration / 2));
+        if (positionSecs >= 30 && positionSecs >= threshold)
+            scrobble();
+    }
+
+    void onTrackFinished()
+    {
+        if (!isEnabled() || m_scrobbled || m_title.isEmpty() || m_duration < 30) return;
+        if (m_playedSecs >= 30) scrobble();
+    }
+
+private:
+    QNetworkAccessManager *m_nam = nullptr;
+
+    QString m_title;
+    QString m_artist;
+    QString m_album;
+    qint64  m_duration   = 0;
+    qint64  m_startTime  = 0;
+    quint64 m_playedSecs = 0;
+    bool    m_scrobbled  = false;
+
+    void updateNowPlaying()
+    {
+        QMap<QString,QString> params;
+        params["method"]   = QStringLiteral("track.updateNowPlaying");
+        params["api_key"]  = AppSettings::instance().lastFmApiKey();
+        params["sk"]       = AppSettings::instance().lastFmSessionKey();
+        params["artist"]   = m_artist;
+        params["track"]    = m_title;
+        params["album"]    = m_album;
+        params["duration"] = QString::number(m_duration);
+        params["api_sig"]  = buildSig(params, AppSettings::instance().lastFmApiSecret());
+        params["format"]   = QStringLiteral("json");
+
+        auto *reply = m_nam->post(apiRequest(), encodeBody(params));
+        connect(reply, &QNetworkReply::finished, reply, &QNetworkReply::deleteLater);
+    }
+
+    void scrobble()
+    {
+        m_scrobbled = true;
+        QMap<QString,QString> params;
+        params["method"]    = QStringLiteral("track.scrobble");
+        params["api_key"]   = AppSettings::instance().lastFmApiKey();
+        params["sk"]        = AppSettings::instance().lastFmSessionKey();
+        params["artist"]    = m_artist;
+        params["track"]     = m_title;
+        params["album"]     = m_album;
+        params["timestamp"] = QString::number(m_startTime);
+        params["duration"]  = QString::number(m_duration);
+        params["api_sig"]   = buildSig(params, AppSettings::instance().lastFmApiSecret());
+        params["format"]    = QStringLiteral("json");
+
+        auto *reply = m_nam->post(apiRequest(), encodeBody(params));
+        connect(reply, &QNetworkReply::finished, reply, &QNetworkReply::deleteLater);
+    }
+
+    /// Build the Last.fm API signature: sort params, concatenate key+value, append secret, md5.
+    static QString buildSig(const QMap<QString,QString> &params, const QString &secret)
+    {
+        QString s;
+        for (auto it = params.constBegin(); it != params.constEnd(); ++it) {
+            if (it.key() != "format" && it.key() != "api_sig")
+                s += it.key() + it.value();
+        }
+        s += secret;
+        return QCryptographicHash::hash(s.toUtf8(), QCryptographicHash::Md5).toHex();
+    }
+
+    static QNetworkRequest apiRequest()
+    {
+        QNetworkRequest req(QUrl(QStringLiteral("https://ws.audioscrobbler.com/2.0/")));
+        req.setHeader(QNetworkRequest::ContentTypeHeader,
+                      QStringLiteral("application/x-www-form-urlencoded"));
+        return req;
+    }
+
+    static QByteArray encodeBody(const QMap<QString,QString> &params)
+    {
+        QUrlQuery q;
+        for (auto it = params.constBegin(); it != params.constEnd(); ++it)
+            q.addQueryItem(it.key(), it.value());
+        return q.toString(QUrl::FullyEncoded).toUtf8();
+    }
+};

src/util/settings.hpp

@@ -31,6 +31,19 @@ public:
     bool rememberLogin() const       { return m_settings.value("auth/remember", true).toBool(); }
     void setRememberLogin(bool r)    { m_settings.setValue("auth/remember", r); }
 
+    // --- Last.fm ---
+    bool    lastFmEnabled()   const  { return m_settings.value("lastfm/enabled", false).toBool(); }
+    void    setLastFmEnabled(bool v) { m_settings.setValue("lastfm/enabled", v); }
+
+    QString lastFmApiKey()    const  { return m_settings.value("lastfm/api_key").toString(); }
+    void    setLastFmApiKey(const QString &v)    { m_settings.setValue("lastfm/api_key", v); }
+
+    QString lastFmApiSecret() const  { return m_settings.value("lastfm/api_secret").toString(); }
+    void    setLastFmApiSecret(const QString &v) { m_settings.setValue("lastfm/api_secret", v); }
+
+    QString lastFmSessionKey() const { return m_settings.value("lastfm/session_key").toString(); }
+    void    setLastFmSessionKey(const QString &v){ m_settings.setValue("lastfm/session_key", v); }
+
 private:
     AppSettings() : m_settings("qobuz-qt", "qobuz-qt") {}
     QSettings m_settings;

src/view/maintoolbar.cpp

@@ -177,6 +177,11 @@ void MainToolBar::onNext()
 void MainToolBar::onProgressReleased()
 {
     m_seeking = false;
+    const quint64 dur = m_backend->duration();
+    if (dur > 0) {
+        const quint64 target = dur * static_cast<quint64>(m_progress->value()) / 1000;
+        m_backend->seek(target);
+    }
 }
 
 void MainToolBar::onVolumeChanged(int volume)