undo/redo import town

src/scenedit/scen.main.cpp

@@ -649,7 +649,8 @@ void handle_menu_choice(eMenu item_hit) {
 		case eMenu::TOWN_IMPORT:
 			if(cTown* town = pick_import_town()) {
 				town->reattach(scenario);
-				delete scenario.towns[cur_town];
+				undo_list.add(action_ptr(new aImportTown(cur_town, scenario.towns[cur_town], town)));
+				update_edit_menu();
 				scenario.towns[cur_town] = town;
 				::town = town;
 				change_made = true;

src/scenedit/scen.undo.cpp

@@ -540,4 +540,28 @@ bool aResizeOutdoors::redo_me() {
 	cur_out.y += mod.top;
 	clamp_current_section();
 	return true;
+}
+
+// The action is cleared from the tree, so erase objects it owns
+aImportTown::~aImportTown() {
+	// If the import happened, delete the old town
+	if(isDone()){
+		delete old_town;
+	}
+	// If it was undone, delete the new town
+	else{
+		delete new_town;
+	}
+}
+
+bool aImportTown::undo_me() {
+	scenario.towns[which] = old_town;
+	set_current_town(which);
+	return true;
+}
+
+bool aImportTown::redo_me() {
+	scenario.towns[which] = new_town;
+	set_current_town(which);
+	return true;
 }

src/scenedit/scen.undo.hpp

@@ -356,4 +356,17 @@ public:
 	~aResizeOutdoors();
 };
 
+/// Action which imports a town from another scenario
+class aImportTown : public cAction {
+	size_t which;
+	cTown* old_town;
+	cTown* new_town;
+	bool undo_me() override;
+	bool redo_me() override;
+public:
+	aImportTown(size_t which, cTown* old_town, cTown* new_town) :
+		cAction("Import Town"), which(which), old_town(old_town), new_town(new_town) {}
+	~aImportTown();
+};
+
 #endif