undo: implement gas switch

This is a bit hairy as - in theory - one gas switch can remove
other gas switch(es) at the same timestamp. However, I did not
find a way to test it. Moreover, it is not clear whether the
dive-tabs are properly updated on undo/redo.

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

CHANGELOG.md

@@ -16,6 +16,7 @@ Mobile: make sure filter header and virtual keyboard are shown when tapping on f
 Mobile: fix issue where in some circumstances changes weren't written to storage
 Mobile: fix issues with filtering while editing dives
 Desktop: implement dive invalidation
+Undo: implement undo of event handling (viz. bookmarks, setpoints, gas switches)
 Desktop: fix tab-order in filter widget
 Desktop: implement fulltext search
 Desktop: add starts-with and exact filter modes for textual search

commands/command.cpp

@@ -354,4 +354,9 @@ void removeEvent(struct dive *d, int dcNr, struct event *ev)
 	execute(new RemoveEvent(d, dcNr, ev));
 }
 
+void addGasSwitch(struct dive *d, int dcNr, int seconds, int tank)
+{
+	execute(new AddGasSwitch(d, dcNr, seconds, tank));
+}
+
 } // namespace Command

commands/command.h

@@ -111,6 +111,7 @@ void addEventDivemodeSwitch(struct dive *d, int dcNr, int seconds, int divemode)
 void addEventSetpointChange(struct dive *d, int dcNr, int seconds, pressure_t pO2);
 void renameEvent(struct dive *d, int dcNr, struct event *ev, const char *name);
 void removeEvent(struct dive *d, int dcNr, struct event *ev);
+void addGasSwitch(struct dive *d, int dcNr, int seconds, int tank);
 
 } // namespace Command
 

commands/command_event.cpp

@@ -5,6 +5,7 @@
 #include "core/subsurface-qt/divelistnotifier.h"
 #include "core/libdivecomputer.h"
 #include "core/gettextfromc.h"
+#include <QVector>
 
 namespace Command {
 
@@ -123,4 +124,65 @@ void RemoveEvent::undoit()
 	add_event_to_dc(dc, eventToAdd.release()); // return ownership to backend
 }
 
+AddGasSwitch::AddGasSwitch(struct dive *d, int dcNr, int seconds, int tank) : EventBase(d, dcNr)
+{
+	// If there is a gas change at this time stamp, remove it before adding the new one.
+	// There shouldn't be more than one gas change per time stamp. Just in case we'll
+	// support that anyway.
+	struct divecomputer *dc = get_dive_dc(d, dcNr);
+	struct event *gasChangeEvent = dc->events;
+	while ((gasChangeEvent = get_next_event_mutable(gasChangeEvent, "gaschange")) != NULL) {
+		if (gasChangeEvent->time.seconds == seconds) {
+			eventsToRemove.push_back(gasChangeEvent);
+			int idx = gasChangeEvent->gas.index;
+			if (std::find(cylinders.begin(), cylinders.end(), idx) == cylinders.end())
+				cylinders.push_back(idx); // cylinders might have changed their status
+		}
+		gasChangeEvent = gasChangeEvent->next;
+	}
+
+	eventsToAdd.emplace_back(create_gas_switch_event(d, dc, seconds, tank));
+}
+
+bool AddGasSwitch::workToBeDone()
+{
+	return true;
+}
+
+void AddGasSwitch::redoit()
+{
+	std::vector<OwningEventPtr> newEventsToAdd;
+	std::vector<event *> newEventsToRemove;
+	newEventsToAdd.reserve(eventsToRemove.size());
+	newEventsToRemove.reserve(eventsToAdd.size());
+	struct divecomputer *dc = get_dive_dc(d, dcNr);
+
+	for (event *ev: eventsToRemove) {
+		remove_event_from_dc(dc, ev);
+		newEventsToAdd.emplace_back(ev); // take ownership of event
+	}
+	for (OwningEventPtr &ev: eventsToAdd) {
+		newEventsToRemove.push_back(ev.get());
+		add_event_to_dc(dc, ev.release()); // return ownership to backend
+	}
+	eventsToAdd = std::move(newEventsToAdd);
+	eventsToRemove = std::move(newEventsToRemove);
+
+	// this means we potentially have a new tank that is being used and needs to be shown
+	fixup_dive(d);
+
+	for (int idx: cylinders)
+		emit diveListNotifier.cylinderEdited(d, idx);
+
+	// TODO: This is silly we send a DURATION change event so that the statistics are recalculated.
+	// We should instead define a proper DiveField that expresses the change caused by a gas switch.
+	emit diveListNotifier.divesChanged(QVector<dive *>{ d }, DiveField::DURATION | DiveField::DEPTH);
+}
+
+void AddGasSwitch::undoit()
+{
+	// Undo and redo do the same thing, as the dives-to-be-added and dives-to-be-removed are exchanged.
+	redoit();
+}
+
 } // namespace Command

commands/command_event.h

@@ -82,6 +82,19 @@ private:
 	event *eventToRemove;		// for redo
 };
 
+class AddGasSwitch : public EventBase {
+public:
+	AddGasSwitch(struct dive *d, int dcNr, int seconds, int tank);
+private:
+	bool workToBeDone() override;
+	void undoit() override;
+	void redoit() override;
+
+	std::vector<int> cylinders; // cylinders that are modified
+	std::vector<OwningEventPtr> eventsToAdd;
+	std::vector<event *> eventsToRemove;
+};
+
 } // namespace Command
 
 #endif // COMMAND_EVENT_H

profile-widget/profilewidget2.cpp

@@ -1645,26 +1645,7 @@ void ProfileWidget2::changeGas(int tank, int seconds)
 	if (!current_dive || tank < 0 || tank >= current_dive->cylinders.nr)
 		return;
 
-	// if there is a gas change at this time stamp, remove it before adding the new one
+	Command::addGasSwitch(current_dive, dc_number, seconds, tank);
-	struct event *gasChangeEvent = current_dc->events;
-	while ((gasChangeEvent = get_next_event_mutable(gasChangeEvent, "gaschange")) != NULL) {
-		if (gasChangeEvent->time.seconds == seconds) {
-			remove_event(gasChangeEvent);
-			gasChangeEvent = current_dc->events;
-		} else {
-			gasChangeEvent = gasChangeEvent->next;
-		}
-	}
-	add_gas_switch_event(current_dive, current_dc, seconds, tank);
-	// this means we potentially have a new tank that is being used and needs to be shown
-	fixup_dive(current_dive);
-	invalidate_dive_cache(current_dive);
-
-	// FIXME - this no longer gets written to the dive list - so we need to enableEdition() here
-
-	emit updateDiveInfo();
-	mark_divelist_changed(true);
-	replot();
 }
 #endif