Expose default revision and metadata

Default system is the system that is scheduled to be
booted into during the next system startup. With the
previous 3 metadata versions it was possible to rotate
to a state where we can't access and present to the user
what currently is scheduled for the next system boot:

Booted  : b
Remote  : b
Rollback: a

call ::rollback() => [ a -> b ]

Booted   : b
Remote   : b
Rollback : b

Now if we want to present a message box to a user when
the system shutdown has been initiated, we don't know what
the system will boot into. This of course could be worked
around by saving a state in user application, but the better
solution is to expose default revision.

With this API, the previous example after the rollback will
contain:

Booted   : b
Remote   : b
Rollback : b
Default  : a

Change-Id: Id123ed8ef76f0284a02899daf22aef0716c78e4e
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

7 files changed, 103 insertions, 27 deletions

diff --git a/examples/qml/basic/main.qml b/examples/qml/basic/main.qml
index b715403..68a70ab 100644
--- a/examples/qml/basic/main.qml
+++ b/examples/qml/basic/main.qml
@@ -108,6 +108,9 @@ Window {
     function updateRollbackMetadataLabel() {
         updateMetadataLabel(rollbackMetadataLabel, OtaClient.rollbackMetadata, OtaClient.rollbackRevision)
     }
+    function updateDefaultMetadataLabel() {
+        updateMetadataLabel(defaultMetadataLabel, OtaClient.defaultMetadata, OtaClient.defaultRevision)
+    }
 
     Flickable {
         anchors.fill: parent
@@ -129,6 +132,9 @@ Window {
             Label { text: "ROLLBACK"; Layout.bottomMargin: 14; Layout.topMargin: 14; font.underline: true }
             Label { id: rollbackMetadataLabel; lineHeight : 1.3 }
 
+            Label { text: "DEFAULT"; Layout.bottomMargin: 14; Layout.topMargin: 14; font.underline: true }
+            Label { id: defaultMetadataLabel; lineHeight : 1.3 }
+
             Label { text: "REPOSITORY CONFIGURATION"; Layout.bottomMargin: 14; Layout.topMargin: 14; font.underline: true }
             Label { id: repoConfigLabel; lineHeight : 1.3 }
 
@@ -255,6 +261,7 @@ Window {
         onRepositoryConfigChanged: updateConfigView(config)
         onRemoteMetadataChanged: updateRemoteMetadataLabel()
         onRollbackMetadataChanged: updateRollbackMetadataLabel()
+        onDefaultMetadataChanged: updateDefaultMetadataLabel()
     }
 
     Component.onCompleted: {
@@ -272,5 +279,6 @@ Window {
         updateBootedMetadataLabel()
         updateRemoteMetadataLabel()
         updateRollbackMetadataLabel()
+        updateDefaultMetadataLabel()
     }
 }
diff --git a/src/imports/pluginmain.cpp b/src/imports/pluginmain.cpp
index 6112b3f..2087b93 100644
--- a/src/imports/pluginmain.cpp
+++ b/src/imports/pluginmain.cpp
@@ -100,6 +100,27 @@ QT_BEGIN_NAMESPACE
 */
 
 /*!
+    \qmlproperty string OtaClient::defaultRevision
+    \readonly
+
+    This property holds a string containing the default system's revision (a
+    checksum in the OSTree repository).
+*/
+
+/*!
+    \qmlproperty string OtaClient::defaultMetadata
+    \readonly
+
+    \include qotaclient.cpp default-metadata
+*/
+
+/*!
+    \qmlsignal OtaClient::defaultMetadataChanged()
+
+    This signal is emitted when the default metadata changes.
+*/
+
+/*!
     \qmlmethod bool OtaClient::fetchRemoteMetadata()
 
     \include qotaclient.cpp fetchremotemetadata-description
@@ -137,14 +158,7 @@ QT_BEGIN_NAMESPACE
 
 /*!
     \qmlmethod bool OtaClient::rollback()
-
-    Rollback to the previous system version.
-
-    This method is asynchronous and returns immediately. The return value
-    holds whether the operation was started successfully.
-
-    \note This method mutates system's state/metadata.
-    \sa rollbackFinished(), restartRequired
+    \include qotaclient.cpp rollback-description
 */
 
 /*!
@@ -229,10 +243,9 @@ QT_BEGIN_NAMESPACE
     \qmlproperty bool OtaClient::updateAvailable
     \readonly
 
-    Holds a bool indicating the availability of a system update. This
-    information is cached; to update the local cache, call fetchRemoteMetadata().
+    Holds a bool indicating the availability of a system update.
 
-    \sa update()
+    \include qotaclient.cpp update-available-description
 */
 
 /*!
@@ -263,9 +276,8 @@ QT_BEGIN_NAMESPACE
     \qmlproperty bool OtaClient::restartRequired
     \readonly
 
-    Holds a bool indicating whether a reboot is required. Reboot is required
-    after update(), updateOffline() and rollback(), to boot into the new default
-    system.
+    Holds a bool indicating whether a reboot is required.
+    Reboot is required when the default system differ from the booted system.
 */
 
 /*!
diff --git a/src/lib/qotaclient.cpp b/src/lib/qotaclient.cpp
index a3e8f37..329c545 100644
--- a/src/lib/qotaclient.cpp
+++ b/src/lib/qotaclient.cpp
@@ -75,7 +75,9 @@ void QOtaClientPrivate::handleStateChanges()
 {
     Q_Q(QOtaClient);
 
-    bool updateAvailable = m_defaultRev != m_remoteRev && m_remoteRev != m_bootedRev;
+    // The default system is used as the configuration merge source
+    // when performing a system update.
+    bool updateAvailable = m_defaultRev != m_remoteRev;
     if (m_updateAvailable != updateAvailable) {
         m_updateAvailable = updateAvailable;
         emit q->updateAvailableChanged(m_updateAvailable);
@@ -148,13 +150,17 @@ void QOtaClientPrivate::remoteMetadataChanged(const QString &remoteRev, const QS
     emit q->remoteMetadataChanged();
 }
 
-void QOtaClientPrivate::defaultRevisionChanged(const QString &defaultRevision)
+void QOtaClientPrivate::defaultRevisionChanged(const QString &defaultRevision, const QString &defaultMetadata)
 {
+    Q_Q(QOtaClient);
     if (m_defaultRev == defaultRevision)
         return;
 
     m_defaultRev = defaultRevision;
+    m_defaultMetadata = defaultMetadata;
     handleStateChanges();
+
+    emit q->defaultMetadataChanged();
 }
 
 /*!
@@ -240,6 +246,12 @@ void QOtaClientPrivate::defaultRevisionChanged(const QString &defaultRevision)
 */
 
 /*!
+    \fn void QOtaClient::defaultMetadataChanged()
+
+    This signal is emitted when the default metadata changes.
+*/
+
+/*!
     \fn void QOtaClient::updateAvailableChanged(bool available)
 
     This signal is emitted when the value of updateAvailable changes. The
@@ -367,13 +379,16 @@ bool QOtaClient::update()
 }
 
 /*!
-    Rollback to the previous system version.
+//! [rollback-description]
+    Rollback to the previous system version. The currently booted system
+    becomes the new rollback system.
 
     This method is asynchronous and returns immediately. The return value
     holds whether the operation was started successfully.
 
     \note This method mutates system's state/metadata.
     \sa rollbackFinished(), restartRequired
+//! [rollback-description]
 */
 bool QOtaClient::rollback()
 {
@@ -644,8 +659,12 @@ QString QOtaClient::statusString() const
     \property QOtaClient::updateAvailable
     \brief whether a system update is available.
 
-    This information is cached; to update the local cache, call
-    fetchRemoteMetadata().
+//! [update-available-description]
+    This information is cached; to update the local cache, call fetchRemoteMetadata().
+    The return value holds whether a system update is available for the default system.
+
+    \sa update()
+//! [update-available-description]
 */
 bool QOtaClient::updateAvailable() const
 {
@@ -671,9 +690,9 @@ bool QOtaClient::rollbackAvailable() const
     \property QOtaClient::restartRequired
     \brief whether a reboot is required.
 
-    Reboot is required after update(), updateOffline() and rollback(),
-    to boot into the new default system.
+    Reboot is required when the default system differ from the booted system.
 
+    \sa defaultRevision, defaultMetadata
 */
 bool QOtaClient::restartRequired() const
 {
@@ -685,7 +704,7 @@ bool QOtaClient::restartRequired() const
     \property QOtaClient::bootedRevision
     \brief a QString containing the booted system's revision.
 
-    A booted revision is a checksum in the OSTree repository.
+    A checksum in the OSTree repository.
 */
 QString QOtaClient::bootedRevision() const
 {
@@ -754,4 +773,32 @@ QString QOtaClient::rollbackMetadata() const
     return d_func()->m_rollbackMetadata;
 }
 
+/*!
+    \property QOtaClient::defaultRevision
+    \brief a QString containing the default system's revision.
+
+    A checksum in the OSTree repository.
+*/
+QString QOtaClient::defaultRevision() const
+{
+    return d_func()->m_defaultRev;
+}
+
+/*!
+    \property QOtaClient::defaultMetadata
+    \brief a QString containing the default system's OTA metadata.
+
+//! [default-metadata]
+    A default system represents what the host will boot into the next time
+    system is rebooted. A default system changes after system updates or rollbacks.
+
+    Returns a JSON-formatted QString containing OTA metadata for the default
+    system. Metadata is bundled with each system's version.
+//! [default-metadata]
+*/
+QString QOtaClient::defaultMetadata() const
+{
+    return d_func()->m_defaultMetadata;
+}
+
 QT_END_NAMESPACE
diff --git a/src/lib/qotaclient.h b/src/lib/qotaclient.h
index 2708a02..28cb422 100644
--- a/src/lib/qotaclient.h
+++ b/src/lib/qotaclient.h
@@ -52,6 +52,8 @@ class Q_DECL_EXPORT QOtaClient : public QObject
     Q_PROPERTY(QString remoteMetadata READ remoteMetadata NOTIFY remoteMetadataChanged)
     Q_PROPERTY(QString rollbackRevision READ rollbackRevision NOTIFY rollbackMetadataChanged)
     Q_PROPERTY(QString rollbackMetadata READ rollbackMetadata NOTIFY rollbackMetadataChanged)
+    Q_PROPERTY(QString defaultRevision READ defaultRevision NOTIFY defaultMetadataChanged)
+    Q_PROPERTY(QString defaultMetadata READ defaultMetadata NOTIFY defaultMetadataChanged)
 public:
     static QOtaClient& instance();
     virtual ~QOtaClient();
@@ -80,10 +82,13 @@ public:
     QString remoteMetadata() const;
     QString rollbackRevision() const;
     QString rollbackMetadata() const;
+    QString defaultRevision() const;
+    QString defaultMetadata() const;
 
 Q_SIGNALS:
     void remoteMetadataChanged();
     void rollbackMetadataChanged();
+    void defaultMetadataChanged();
     void updateAvailableChanged(bool available);
     void rollbackAvailableChanged();
     void restartRequiredChanged(bool required);
diff --git a/src/lib/qotaclient_p.h b/src/lib/qotaclient_p.h
index a58a7ec..7e25b39 100644
--- a/src/lib/qotaclient_p.h
+++ b/src/lib/qotaclient_p.h
@@ -57,7 +57,7 @@ public:
     void setBootedMetadata(const QString &bootedRev, const QString &bootedMetadata);
     void rollbackMetadataChanged(const QString &rollbackRev, const QString &rollbackMetadata, int treeCount);
     void remoteMetadataChanged(const QString &remoteRev, const QString &remoteMetadata);
-    void defaultRevisionChanged(const QString &defaultRevision);
+    void defaultRevisionChanged(const QString &defaultRevision, const QString &defaultMetadata);
 
     // members
     QOtaClient *const q_ptr;
@@ -69,7 +69,6 @@ public:
     QString m_error;
     QThread *m_otaAsyncThread;
     QScopedPointer<QOtaClientAsync> m_otaAsync;
-    QString m_defaultRev;
 
     QString m_bootedRev;
     QString m_bootedMetadata;
@@ -77,6 +76,8 @@ public:
     QString m_remoteMetadata;
     QString m_rollbackRev;
     QString m_rollbackMetadata;
+    QString m_defaultRev;
+    QString m_defaultMetadata;
 };
 
 QT_END_NAMESPACE
diff --git a/src/lib/qotaclientasync.cpp b/src/lib/qotaclientasync.cpp
index 987a879..738a8f1 100644
--- a/src/lib/qotaclientasync.cpp
+++ b/src/lib/qotaclientasync.cpp
@@ -258,14 +258,17 @@ bool QOtaClientAsync::handleRevisionChanges(OstreeSysroot *sysroot, bool reloadS
 
     g_autoptr(GPtrArray) deployments = ostree_sysroot_get_deployments (sysroot);
     OstreeDeployment *firstDeployment = (OstreeDeployment*)deployments->pdata[0];
+    bool ok = true;
     QString defaultRev(QLatin1String(ostree_deployment_get_csum (firstDeployment)));
-    emit defaultRevisionChanged(defaultRev);
+    QString defaultMetadata = metadataFromRev(defaultRev, &ok);
+    if (!ok)
+        return false;
+    emit defaultRevisionChanged(defaultRev, defaultMetadata);
 
     int index = rollbackIndex(sysroot);
     if (index != -1) {
         OstreeDeployment *rollbackDeployment = (OstreeDeployment*)deployments->pdata[index];
         QString rollbackRev(QLatin1String(ostree_deployment_get_csum (rollbackDeployment)));
-        bool ok = true;
         QString rollbackMetadata = metadataFromRev(rollbackRev, &ok);
         if (!ok)
             return false;
diff --git a/src/lib/qotaclientasync_p.h b/src/lib/qotaclientasync_p.h
index 6252878..e5756e0 100644
--- a/src/lib/qotaclientasync_p.h
+++ b/src/lib/qotaclientasync_p.h
@@ -68,7 +68,7 @@ signals:
     void errorOccurred(const QString &error);
     void statusStringChanged(const QString &status);
     void remoteMetadataChanged(const QString &remoteRev, const QString &remoteMetadata);
-    void defaultRevisionChanged(const QString &defaultRevision);
+    void defaultRevisionChanged(const QString &defaultRevision, const QString &defaultMetadata);
 
 protected:
     OstreeSysroot* defaultSysroot();