FixElevation - Use post instead of get for open-elevation requests

This allows to request all points at once since post api has
no limits according the documentation.
Break logic is preserve just in case we need it in the future.
Fixes #4261

src/FileIO/FixElevation.cpp

@@ -140,34 +140,48 @@ FixElevation::postProcess(RideFile *ride, DataProcessorConfig *config=0, QString
     QString latLngCollection = "";
     int pointCount = 0;
     try {
+
         for (std::vector<elevationGPSPoint>::iterator point = elvPoints.begin();
              point != elvPoints.end(); ++point) {
-            if (latLngCollection.length() != 0) {
-                latLngCollection.append('|');
+
+            if (latLngCollection.length() == 0) {
+                latLngCollection.append("{\"locations\":[");
+            } else {
+                latLngCollection.append(',');
             }
+
             // these values need extended precision or place marker jumps around.
-            latLngCollection.append(QString::number(point->lat,'g',10));
+            latLngCollection.append("{\"latitude\":" + QString::number(point->lat,'g',10));
             latLngCollection.append(',');
-            latLngCollection.append(QString::number(point->lon,'g',10));
-            if (pointCount == 45) { // Open-Elevation has a 1024 bytes limit for Get requests
+            latLngCollection.append("\"longitude\":" + QString::number(point->lon,'g',10) + "}");
+
+            // this should not happen, it is preserve just in case we need to break the requests
+            if (pointCount == 86400) {
+                latLngCollection.append("]}");
                 elevationPoints = elevationPoints + FetchElevationData(latLngCollection);
                 latLngCollection = "";
                 pointCount = 0;
             } else {
                 ++pointCount;
             }
         }
+
+        // send a request for the remainder points, currently all at once for efficiency
         if (pointCount > 0) {
+            latLngCollection.append("]}");
             elevationPoints = elevationPoints + FetchElevationData(latLngCollection);
         }
+
     } catch (QString err) {
+
         qDebug() << "Cannot fetch elevation data: " << err;
         QMessageBox oops(QMessageBox::Critical, tr("Fix Elevation Data not possible"),
                          tr("The following problem occured: %1").arg(err));
         oops.exec();
         // close LUW
         ride->command->endLUW();
         return false;
+
     }
 
 
@@ -261,11 +275,14 @@ FixElevation::postProcess(RideFile *ride, DataProcessorConfig *config=0, QString
 QList<double>
 FixElevation::FetchElevationData(QString latLngCollection)
 {
-    // https://api.open-elevation.com/api/v1/lookup?locations=10,10|20,20|41.161758,-8.583933
     QList<double> elevationPoints;
+
+    QNetworkRequest request(QUrl(QString("https://api.open-elevation.com/api/v1/lookup")));
+    request.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");
+    request.setRawHeader("Accept", "application/json");
+
     QNetworkAccessManager *networkMgr = new QNetworkAccessManager();
-    QNetworkReply *reply = networkMgr->get( QNetworkRequest(
-            QUrl( QString("https://api.open-elevation.com/api/v1/lookup?locations=" + latLngCollection ) ) ) );
+    QNetworkReply *reply = networkMgr->post(request, latLngCollection.toUtf8());
 
     QEventLoop loop;
     QObject::connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));