Undo: make weight-deletion an undoable action

This one is a bit more complicated than weight adding, because the
multiple-dive case is not well defined. If multiple dives are selected,
this implementation will search for weights that are identical to the
weight deleted in the currently shown dive. The position of the weight
in the list is ignored.

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

commands/command_edit.cpp

@@ -985,4 +985,75 @@ void AddWeight::redo()
 	}
 }
 
+static int find_weightsystem_index(const struct dive *d, weightsystem_t ws)
+{
+	for (int idx = 0; idx < d->weightsystems.nr; ++idx) {
+		if (same_weightsystem(d->weightsystems.weightsystems[idx], ws))
+			return idx;
+	}
+	return -1;
+}
+
+RemoveWeight::RemoveWeight(int index, bool currentDiveOnly) :
+	EditDivesBase(currentDiveOnly),
+	ws{ {0}, nullptr }
+{
+	// Get the old weightsystem, bail if index is invalid
+	if (!current || index < 0 || index >= current->weightsystems.nr) {
+		dives.clear();
+		return;
+	}
+	ws = clone_weightsystem(current->weightsystems.weightsystems[index]);
+
+	// Deleting a weightsystem from multiple dives is semantically ill-defined.
+	// What we will do is trying to delete the same weightsystem if it exists.
+	// For that purpose, we will determine the indices of the same weightsystem.
+	std::vector<dive *> divesNew;
+	divesNew.reserve(dives.size());
+	indexes.reserve(dives.size());
+
+	for (dive *d: dives) {
+		if (d == current) {
+			divesNew.push_back(d);
+			indexes.push_back(index);
+			continue;
+		}
+		int idx = find_weightsystem_index(d, ws);
+		if (idx >= 0) {
+			divesNew.push_back(d);
+			indexes.push_back(idx);
+		}
+	}
+	dives = std::move(divesNew);
+
+	//: remove the part in parentheses for %n = 1
+	setText(tr("Remove weight (%n dive(s))", "", dives.size()));
+}
+
+RemoveWeight::~RemoveWeight()
+{
+	free((void *)ws.description);
+}
+
+bool RemoveWeight::workToBeDone()
+{
+	return !dives.empty();
+}
+
+void RemoveWeight::undo()
+{
+	for (size_t i = 0; i < dives.size(); ++i) {
+		add_to_weightsystem_table(&dives[i]->weightsystems, indexes[i], clone_weightsystem(ws));
+		emit diveListNotifier.weightAdded(dives[i], indexes[i]);
+	}
+}
+
+void RemoveWeight::redo()
+{
+	for (size_t i = 0; i < dives.size(); ++i) {
+		remove_weightsystem(dives[i], indexes[i]);
+		emit diveListNotifier.weightRemoved(dives[i], indexes[i]);
+	}
+}
+
 } // namespace Command