systemstats: Add "Remaining time" property

Reports the time until the battery is fully charged (when charging)
or empty (when discharging).

It doesn't do any rounding, so the value is reported down to the second
even though it's of course nowhere as accurate.

src/systemstats/livedataobject.cpp

@@ -118,6 +118,12 @@ LiveDataObject::LiveDataObject(QAlphaCloud::Connector *connector, const QString
     // m_batteryDischargeProperty->setMax(photovoltaicDesignPower * 1000);
     connect(m_batteryDischargeProperty, &KSysGuard::SensorProperty::subscribedChanged, this, &LiveDataObject::update);
 
+    m_batteryTimeProperty = new KSysGuard::SensorProperty(QStringLiteral("batteryTime"), tr("Remaining Time"), 0, this);
+    m_batteryTimeProperty->setShortName(tr("Remaining"));
+    m_batteryTimeProperty->setUnit(KSysGuard::Unit::UnitTime);
+    m_batteryTimeProperty->setVariantType(QVariant::Int);
+    connect(m_batteryTimeProperty, &KSysGuard::SensorProperty::subscribedChanged, this, &LiveDataObject::update);
+
 #if PRESENTATION_BUILD
     //: Sensor object name with live data
     setName(tr("Live"));
@@ -161,7 +167,8 @@ void LiveDataObject::update()
     m_gridConsumptionProperty->setValue(gridConsumption);
 
     m_batterySocProperty->setValue(m_liveData->batterySoc());
-    m_batteryEnergyProperty->setValue(std::round(m_batteryRemainingCapacityWh * m_liveData->batterySoc() / 100.0));
+    const int batteryEnergy = std::round(m_batteryRemainingCapacityWh * m_liveData->batterySoc() / 100.0);
+    m_batteryEnergyProperty->setValue(batteryEnergy);
 
     const int batteryPower = m_liveData->batteryPower();
     int batteryCharge = 0;
@@ -175,6 +182,18 @@ void LiveDataObject::update()
 
     m_batteryChargeProperty->setValue(batteryCharge);
     m_batteryDischargeProperty->setValue(batteryDischarge);
+
+    if (batteryCharge > 0) {
+        m_batteryTimeProperty->setName(tr("Time until full"));
+
+        if (m_batteryRemainingCapacityWh > 0) {
+            const int neededCapacity = std::max(0, m_batteryRemainingCapacityWh - batteryEnergy);
+            m_batteryTimeProperty->setValue(neededCapacity / qreal(batteryCharge) * 60 * 60);
+        }
+    } else if (batteryDischarge > 0) {
+        m_batteryTimeProperty->setName(tr("Time until empty"));
+        m_batteryTimeProperty->setValue(batteryEnergy / qreal(batteryDischarge) * 60 * 60);
+    }
 }
 
 void LiveDataObject::updateSystem(const QModelIndex &index)

src/systemstats/livedataobject.h

@@ -50,6 +50,8 @@ class LiveDataObject : public KSysGuard::SensorObject
 
     KSysGuard::SensorProperty *m_batteryChargeProperty = nullptr;
     KSysGuard::SensorProperty *m_batteryDischargeProperty = nullptr;
+
+    KSysGuard::SensorProperty *m_batteryTimeProperty = nullptr;
     // TODO battery status property
 
     // Mirrored from StorageSystemsModel