Undo: make dive site merging undoable

This one was rather trivial, as there is no actual merging
done. Quite simply, a number of dive sites are removed and
their dive added to a different dive site.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

desktop-widgets/command.cpp

@@ -118,4 +118,9 @@ void addDiveSite(const QString &name)
 	execute(new AddDiveSite(name));
 }
 
+void mergeDiveSites(dive_site *ds, const QVector<dive_site *> &sites)
+{
+	execute(new MergeDiveSites(ds, sites));
+}
+
 } // namespace Command

desktop-widgets/command.h

@@ -48,6 +48,7 @@ void editDiveSiteCountry(dive_site *ds, const QString &value);
 void editDiveSiteLocation(dive_site *ds, location_t value);
 void editDiveSiteTaxonomy(dive_site *ds, taxonomy_data &value); // value is consumed (i.e. will be erased after call)!
 void addDiveSite(const QString &name);
+void mergeDiveSites(dive_site *ds, const QVector<dive_site *> &sites);
 
 } // namespace Command
 

desktop-widgets/command_divesite.cpp

@@ -266,4 +266,45 @@ void EditDiveSiteTaxonomy::undo()
 	redo();
 }
 
+MergeDiveSites::MergeDiveSites(dive_site *dsIn, const QVector<dive_site *> &sites) : ds(dsIn)
+{
+	setText(tr("merge dive sites"));
+	sitesToRemove.reserve(sites.size());
+	for (dive_site *site: sites) {
+		if (site != ds)
+			sitesToRemove.push_back(site);
+	}
+}
+
+bool MergeDiveSites::workToBeDone()
+{
+	return !sitesToRemove.empty();
+}
+
+void MergeDiveSites::redo()
+{
+	// First, remove all dive sites
+	sitesToAdd = std::move(removeDiveSites(sitesToRemove));
+
+	// The dives of the above dive sites were reset to no dive sites.
+	// Add them to the merged-into dive site. Thankfully, we remember
+	// the dives in the sitesToAdd vector.
+	for (const OwningDiveSitePtr &site: sitesToAdd) {
+		for (int i = 0; i < site->dives.nr; ++i)
+			add_dive_to_dive_site(site->dives.dives[i], ds); // TODO: send dive changed signal
+	}
+}
+
+void MergeDiveSites::undo()
+{
+	// Before readding the dive sites, unregister the corresponding dives so that they can be
+	// readded to their old dive sites.
+	for (const OwningDiveSitePtr &site: sitesToAdd) {
+		for (int i = 0; i < site->dives.nr; ++i)
+			unregister_dive_from_dive_site(site->dives.dives[i]);
+	}
+
+	sitesToRemove = std::move(addDiveSites(sitesToAdd));
+}
+
 } // namespace Command

desktop-widgets/command_divesite.h

@@ -117,6 +117,23 @@ private:
 	taxonomy_data value; // Value to be set
 };
 
+class MergeDiveSites : public Base {
+public:
+	MergeDiveSites(dive_site *ds, const QVector<dive_site *> &sites);
+private:
+	bool workToBeDone() override;
+	void undo() override;
+	void redo() override;
+
+	dive_site *ds;
+
+	// For redo
+	std::vector<dive_site *> sitesToRemove;
+
+	// For undo
+	std::vector<OwningDiveSitePtr> sitesToAdd;
+};
+
 } // namespace Command
 
 #endif // COMMAND_DIVESITE_H

desktop-widgets/locationinformation.cpp

@@ -62,24 +62,16 @@ void LocationInformationWidget::mergeSelectedDiveSites()
 {
 	if (!diveSite)
 		return;
-	if (QMessageBox::warning(MainWindow::instance(), tr("Merging dive sites"),
-				 tr("You are about to merge dive sites, you can't undo that action \n Are you sure you want to continue?"),
-				 QMessageBox::Ok, QMessageBox::Cancel) != QMessageBox::Ok)
-		return;
 
 	const QModelIndexList selection = ui.diveSiteListView->selectionModel()->selectedIndexes();
-	// std::vector guarantees contiguous storage and can therefore be passed to C-code
-	std::vector<struct dive_site *> selected_dive_sites;
+	QVector<dive_site *> selected_dive_sites;
 	selected_dive_sites.reserve(selection.count());
 	for (const QModelIndex &idx: selection) {
 		dive_site *ds = idx.data(LocationInformationModel::DIVESITE_ROLE).value<dive_site *>();
 		if (ds)
 			selected_dive_sites.push_back(ds);
 	}
-	merge_dive_sites(diveSite, selected_dive_sites.data(), (int)selected_dive_sites.size());
-	LocationInformationModel::instance()->update();
-	QSortFilterProxyModel *m = (QSortFilterProxyModel *)ui.diveSiteListView->model();
-	m->invalidate();
+	Command::mergeDiveSites(diveSite, selected_dive_sites);
 }
 
 void LocationInformationWidget::updateLabels()