Chess: Prevent board changes when waiting for ChessEngine to move

Author: https://github.com/bcoles
Commit: https://github.com/SerenityOS/serenity/commit/172707a9458
Pull-request: https://github.com/SerenityOS/serenity/pull/4440
Issue: https://github.com/SerenityOS/serenity/issues/3875

Games/Chess/ChessWidget.cpp

@@ -273,7 +273,7 @@ void ChessWidget::mouseup_event(GUI::MouseEvent& event)
                 GUI::MessageBox::show(window(), msg, "Game Over", GUI::MessageBox::Type::Information);
             }
         } else {
-            maybe_input_engine_move();
+            input_engine_move();
         }
     }
 
@@ -372,7 +372,7 @@ void ChessWidget::reset()
     m_board = Chess::Board();
     m_side = (arc4random() % 2) ? Chess::Colour::White : Chess::Colour::Black;
     m_drag_enabled = true;
-    maybe_input_engine_move();
+    input_engine_move();
     update();
 }
 
@@ -391,9 +391,18 @@ void ChessWidget::set_board_theme(const StringView& name)
     }
 }
 
-void ChessWidget::maybe_input_engine_move()
+bool ChessWidget::want_engine_move()
 {
-    if (!m_engine || board().turn() == side())
+    if (!m_engine)
+        return false;
+    if (board().turn() == side())
+        return false;
+    return true;
+}
+
+void ChessWidget::input_engine_move()
+{
+    if (!want_engine_move())
         return;
 
     bool drag_was_enabled = drag_enabled();
@@ -401,6 +410,8 @@ void ChessWidget::maybe_input_engine_move()
         set_drag_enabled(false);
 
     m_engine->get_best_move(board(), 4000, [this, drag_was_enabled](Chess::Move move) {
+        if (!want_engine_move())
+            return;
         set_drag_enabled(drag_was_enabled);
         ASSERT(board().apply_move(move));
         m_playback_move_number = m_board.moves().size();
@@ -614,21 +625,32 @@ bool ChessWidget::export_pgn(const StringView& export_path) const
 
 void ChessWidget::flip_board()
 {
+    if (want_engine_move()) {
+        GUI::MessageBox::show(window(), "You can only flip the board on your turn.", "Flip Board", GUI::MessageBox::Type::Information);
+        return;
+    }
     m_side = Chess::opposing_colour(m_side);
+    input_engine_move();
     update();
 }
 
-void ChessWidget::resign()
+int ChessWidget::resign()
 {
-    if (m_engine && m_board.turn() != m_side) {
+    if (want_engine_move()) {
         GUI::MessageBox::show(window(), "You can only resign on your turn.", "Resign", GUI::MessageBox::Type::Information);
-        return;
+        return -1;
     }
 
+    auto result = GUI::MessageBox::show(window(), "Are you sure you wish to resign?", "Resign", GUI::MessageBox::Type::Warning, GUI::MessageBox::InputType::YesNo);
+    if (result != GUI::MessageBox::ExecYes)
+        return -1;
+
     board().set_resigned(m_board.turn());
 
     set_drag_enabled(false);
     update();
     const String msg = Chess::Board::result_to_string(m_board.game_result(), m_board.turn());
     GUI::MessageBox::show(window(), msg, "Game Over", GUI::MessageBox::Type::Information);
+
+    return 0;
 }

Games/Chess/ChessWidget.h

@@ -70,7 +70,7 @@ public:
     bool import_pgn(const StringView& import_path);
     bool export_pgn(const StringView& export_path) const;
 
-    void resign();
+    int resign();
     void flip_board();
     void reset();
 
@@ -95,7 +95,8 @@ public:
 
     void set_engine(RefPtr<Engine> engine) { m_engine = engine; }
 
-    void maybe_input_engine_move();
+    void input_engine_move();
+    bool want_engine_move();
 
     void set_coordinates(bool coordinates) { m_coordinates = coordinates; }
     bool coordinates() const { return m_coordinates; }

Games/Chess/main.cpp

@@ -139,6 +139,10 @@ int main(int argc, char** argv)
     app_menu.add_separator();
 
     app_menu.add_action(GUI::Action::create("New game", { Mod_None, Key_F2 }, [&](auto&) {
+        if (widget.board().game_result() == Chess::Board::Result::NotFinished) {
+            if (widget.resign() < 0)
+                return;
+        }
         widget.reset();
     }));
     app_menu.add_separator();
@@ -206,7 +210,7 @@ int main(int argc, char** argv)
                 widget.set_engine(nullptr);
             } else {
                 widget.set_engine(Engine::construct(action.text()));
-                widget.maybe_input_engine_move();
+                widget.input_engine_move();
             }
         });
         engines_action_group.add_action(*action);