create migration plan

src/rpc.h

@@ -46,6 +46,55 @@ public:
     void newZaddr               (bool sapling, const std::function<void(json)>& cb);
     void newTaddr               (const std::function<void(json)>& cb);
     
+    // Batch method. Note: Because of the template, it has to be in the header file. 
+    template<class T>
+    void getBatchRPC(const QList<T>& payloads,
+                     std::function<json(T)> payloadGenerator,
+                     std::function<void(QMap<T, json>*)> cb) {    
+        auto responses = new QMap<T, json>(); // zAddr -> list of responses for each call. 
+        int totalSize = payloads.size();
+
+        for (auto item: payloads) {
+            json payload = payloadGenerator(item);
+            
+            QNetworkReply *reply = restclient->post(request, QByteArray::fromStdString(payload.dump()));
+
+            QObject::connect(reply, &QNetworkReply::finished, [=] {
+                reply->deleteLater();
+                
+                auto all = reply->readAll();            
+                auto parsed = json::parse(all.toStdString(), nullptr, false);
+
+                if (reply->error() != QNetworkReply::NoError) {            
+                    qDebug() << QString::fromStdString(parsed.dump());
+                    qDebug() << reply->errorString();
+
+                    (*responses)[item] = json::object();    // Empty object
+                } else {
+                    if (parsed.is_discarded()) {
+                        (*responses)[item] = json::object();    // Empty object
+                    } else {
+                        (*responses)[item] = parsed["result"];
+                    }
+                }
+            });
+        }
+
+        auto waitTimer = new QTimer(main);
+        QObject::connect(waitTimer, &QTimer::timeout, [=]() {
+            if (responses->size() == totalSize) {
+                waitTimer->stop();
+
+                cb(responses);
+
+                waitTimer->deleteLater();            
+            }
+        });
+        waitTimer->start(100);    
+    }
+
+
+
 private:
     void doRPC      (const json& payload, const std::function<void(json)>& cb);
     void doSendRPC  (const json& payload, const std::function<void(json)>& cb);
@@ -71,11 +120,6 @@ private:
     void handleConnectionError  (const QString& error);
     void handleTxError          (const QString& error);
 
-    // Batch
-    void                getBatchRPC(const QList<QString>& payloads,
-                                    std::function<json(QString)> payloadGenerator,
-                                    std::function<void(QMap<QString, json>*)> cb);
-
     QNetworkAccessManager*      restclient;    
     QNetworkRequest             request;