2-stage asynchronous cancelling of downloads

src/contentmanager.cpp

@@ -101,6 +101,9 @@ ContentManager::ContentManager(Library* library, kiwix::Downloader* downloader)
     connect(this, &DownloadManager::downloadUpdated,
             this, &ContentManager::updateDownload);
 
+    connect(this, &DownloadManager::downloadCancelled,
+            this, &ContentManager::downloadWasCancelled);
+
     connect(this, &DownloadManager::downloadDisappeared,
             this, &ContentManager::downloadDisappeared);
 
@@ -641,15 +644,12 @@ void ContentManager::cancelBook(const QString& id)
     auto text = gt("cancel-download-text");
     text = text.replace("{{ZIM}}", QString::fromStdString(mp_library->getBookById(id).getTitle()));
     showConfirmBox(gt("cancel-download"), text, mp_view, [=]() {
-        reallyCancelBook(id);
+        DownloadManager::addRequest(DownloadState::CANCEL, id);
     });
 }
 
-void ContentManager::reallyCancelBook(const QString& id)
+void ContentManager::downloadWasCancelled(const QString& id)
 {
-    if ( !DownloadManager::cancelDownload(id) )
-        return;
-
     removeDownload(id);
 
     // incompleted downloaded file should be perma deleted

src/contentmanager.h

@@ -98,16 +98,14 @@ public slots:
     void updateCategories(const QString& content);
     void pauseBook(const QString& id, QModelIndex index);
     void resumeBook(const QString& id, QModelIndex index);
-    // cancelBook() asks for confirmation (reallyCancelBook() doesn't)
     void cancelBook(const QString& id);
     void onCustomContextMenu(const QPoint &point);
     void openBookWithIndex(const QModelIndex& index);
     void updateDownload(QString bookId, const DownloadInfo& downloadInfo);
+    void downloadWasCancelled(const QString& id);
 
 private: // functions
     QStringList getBookIds();
-    // reallyCancelBook() doesn't ask for confirmation (unlike cancelBook())
-    void reallyCancelBook(const QString& id);
     // reallyEraseBook() doesn't ask for confirmation (unlike eraseBook())
     void reallyEraseBook(const QString& id, bool moveToTrash);
     void eraseBookFilesFromComputer(const std::string& bookPath, bool moveToTrash);

src/downloadmanagement.cpp

@@ -84,6 +84,10 @@ void DownloadState::changeState(Action action)
         if ( status == PAUSED ) {
             status = RESUME_REQUESTED;
         }
+    } else if ( action == CANCEL ) {
+        if ( status == DOWNLOADING || status == PAUSED ) {
+            status = CANCEL_REQUESTED;
+        }
     }
 
     if ( status != oldStatus ) {
@@ -130,7 +134,7 @@ void DownloadManager::processDownloadActions()
             case DownloadState::START:  /* startDownload(req.bookId); */ break;  // API problem
             case DownloadState::PAUSE:  pauseDownload(req.bookId);  break;
             case DownloadState::RESUME: resumeDownload(req.bookId); break;
-            case DownloadState::CANCEL: /* cancelDownload(req.bookId); */ break; // API problem
+            case DownloadState::CANCEL: cancelDownload(req.bookId); break;
             case DownloadState::UPDATE: updateDownload(req.bookId); break;
             }
         }
@@ -322,19 +326,18 @@ void DownloadManager::resumeDownload(const QString& bookId)
     }
 }
 
-bool DownloadManager::cancelDownload(const QString& bookId)
+void DownloadManager::cancelDownload(const QString& bookId)
 {
     const auto downloadId = mp_library->getBookById(bookId).getDownloadId();
     if ( downloadId.empty() ) {
         // Completion of the download has been detected (and its id was reset)
         // before the confirmation to cancel the download was granted.
-        return false;
+        return;
     }
 
     auto download = mp_downloader->getDownload(downloadId);
     try {
         download->cancelDownload();
-        return true;
     } catch (const kiwix::AriaError&) {
         // Download has completed before the cancel request was handled.
         // Most likely the download was already complete at the time
@@ -342,8 +345,9 @@ bool DownloadManager::cancelDownload(const QString& bookId)
         // its completion was not yet detected (and/or handled) by the
         // download updater thread (letting the code pass past the empty
         // downloadId check above).
-        return false;
+        return;
     }
+    emit downloadCancelled(bookId);
 }
 
 void DownloadManager::removeDownload(QString bookId)

src/downloadmanagement.h

@@ -71,7 +71,8 @@ public: // types
         DOWNLOADING,
         PAUSE_REQUESTED,
         PAUSED,
-        RESUME_REQUESTED
+        RESUME_REQUESTED,
+        CANCEL_REQUESTED
     };
 
 public: // data
@@ -157,7 +158,6 @@ public: // functions
 
     // returns the download id
     std::string startDownload(const kiwix::Book& book, const QString& downloadDirPath);
-    bool cancelDownload(const QString& bookId);
     void removeDownload(QString bookId);
 
     DownloadStatePtr getDownloadState(QString bookId) const
@@ -167,6 +167,7 @@ public: // functions
 
 signals:
     void downloadUpdated(QString bookId, const DownloadInfo& );
+    void downloadCancelled(QString bookId);
     void downloadDisappeared(QString bookId);
 
 private: // types
@@ -187,6 +188,7 @@ private: // functions
     void pauseDownload(const QString& bookId);
     void resumeDownload(const QString& bookId);
     void updateDownload(QString bookId);
+    void cancelDownload(const QString& bookId);
 
 private: // data
     const Library* const     mp_library;