ContentManagerModel maintains the download state

This fixes the bugs related to pending download statuses being discarded
by filtering and similar operations that result in full update of the
ContentManagerModel.

Instead this commit leads to a new bug - completion of a download
is not always properly detected for very small (and thus instantaneous)
downloads. This is caused by library update events triggered by ZIM
directory monitoring (which notifies about a new ZIM file appearing
in the download directory) interfering with the download status update
signal.

src/contentmanagermodel.cpp

@@ -136,6 +136,7 @@ std::shared_ptr<RowNode> ContentManagerModel::createNode(BookInfo bookItem, QMap
                                    }, id, weakRoot));
     std::weak_ptr<RowNode> weakRowNodePtr = rowNodePtr;
     const auto descNodePtr = std::make_shared<DescriptionNode>(DescriptionNode(bookItem["description"].toString(), weakRowNodePtr));
+
     rowNodePtr->appendChild(descNodePtr);
     return rowNodePtr;
 }
@@ -144,7 +145,15 @@ void ContentManagerModel::setupNodes()
 {
     beginResetModel();
     for (auto bookItem : m_data) {
-        rootNode->appendChild(createNode(bookItem, iconMap));
+        const auto rowNode = createNode(bookItem, iconMap);
+
+        // Restore download state during model updates (filtering, etc)
+        const auto downloadIter = m_downloads.constFind(rowNode->getBookId());
+        if ( downloadIter != m_downloads.constEnd() ) {
+            rowNode->setDownloadState(downloadIter.value());
+        }
+
+        rootNode->appendChild(rowNode);
     }
     endResetModel();
 }
@@ -239,10 +248,16 @@ std::shared_ptr<RowNode> getSharedPointer(RowNode* ptr)
 void ContentManagerModel::startDownload(QModelIndex index)
 {
     auto node = getSharedPointer(static_cast<RowNode*>(index.internalPointer()));
-    node->setDownloadState(new DownloadState);
+    const auto bookId = node->getBookId();
-    QTimer *timer = node->getDownloadState()->getDownloadUpdateTimer();
+    const auto newDownload = std::make_shared<DownloadState>();
+    m_downloads[bookId] = newDownload;
+    node->setDownloadState(newDownload);
+    QTimer *timer = newDownload->getDownloadUpdateTimer();
     connect(timer, &QTimer::timeout, this, [=]() {
-        node->getDownloadState()->update(node->getBookId());
+        if ( ! newDownload->update(bookId) ) {
+            m_downloads.remove(bookId);
+            node->setDownloadState(nullptr);
+        }
         emit dataChanged(index, index);
     });
 }
@@ -265,6 +280,7 @@ void ContentManagerModel::cancelDownload(QModelIndex index)
 {
     auto node = static_cast<RowNode*>(index.internalPointer());
     node->setDownloadState(nullptr);
+    m_downloads.remove(node->getBookId());
     emit dataChanged(index, index);
 }
 

src/contentmanagermodel.h

@@ -6,6 +6,7 @@
 #include <QVariant>
 #include <QIcon>
 #include "thumbnaildownloader.h"
+#include "rownode.h"
 #include <memory>
 
 class RowNode;
@@ -58,6 +59,7 @@ private: // data
     int zimCount = 0;
     ThumbnailDownloader td;
     QMap<QString, QByteArray> iconMap;
+    QMap<QString, std::shared_ptr<DownloadState>> m_downloads;
 };
 
 #endif // CONTENTMANAGERMODEL_H

src/rownode.cpp

@@ -33,7 +33,7 @@ QString convertToUnits(QString size)
 
 } // unnamed namespace
 
-void DownloadState::update(QString id)
+bool DownloadState::update(QString id)
 {
     auto downloadInfos = KiwixApp::instance()->getContentManager()->updateDownloadInfos(id, {"status", "completedLength", "totalLength", "downloadSpeed"});
     double percent = downloadInfos["completedLength"].toDouble() / downloadInfos["totalLength"].toDouble();
@@ -51,7 +51,9 @@ void DownloadState::update(QString id)
         // from another thread.
         m_downloadUpdateTimer.reset();
         m_downloadInfo = {0, "", "", false};
+        return false;
     }
+    return true;
 }
 
 void DownloadState::pause()

src/rownode.h

@@ -24,7 +24,7 @@ public:
     QTimer* getDownloadUpdateTimer() const { return m_downloadUpdateTimer.get(); }
     void pause();
     void resume();
-    void update(QString id);
+    bool update(QString id);
 
 protected:
     // This is non-NULL only for a pending (even if paused) download