From 42f7f9d0f804b4d94c9baf5ecc6228d39c58e321 Mon Sep 17 00:00:00 2001
From: lucastarche <lucastarche@gmail.com>
Date: Sat, 27 Mar 2021 17:59:54 -0300
Subject: [PATCH] Chess: Show available moves from current piece

---
 Userland/Games/Chess/ChessWidget.cpp | 24 ++++++++++++++++++++++++
 Userland/Games/Chess/ChessWidget.h   |  2 ++
 2 files changed, 26 insertions(+)

diff --git a/Userland/Games/Chess/ChessWidget.cpp b/Userland/Games/Chess/ChessWidget.cpp
index ec622f012f..e3b31b33e3 100644
--- a/Userland/Games/Chess/ChessWidget.cpp
+++ b/Userland/Games/Chess/ChessWidget.cpp
@@ -155,6 +155,21 @@ void ChessWidget::paint_event(GUI::PaintEvent& event)
     }
 
     if (m_dragging_piece) {
+        if (m_show_available_moves) {
+            Gfx::IntPoint move_point;
+            Gfx::IntPoint point_offset = { tile_width / 3, tile_height / 3 };
+            Gfx::IntSize rect_size = { tile_width / 3, tile_height / 3 };
+            for (const auto& square : m_available_moves) {
+                if (side() == Chess::Color::White) {
+                    move_point = { square.file * tile_width, (7 - square.rank) * tile_height };
+                } else {
+                    move_point = { (7 - square.file) * tile_width, square.rank * tile_height };
+                }
+
+                painter.fill_ellipse({ move_point + point_offset, rect_size }, Gfx::Color::LightGray);
+            }
+        }
+
         auto bmp = m_pieces.get(active_board.get_piece(m_moving_square));
         if (bmp.has_value()) {
             auto center = m_drag_point - Gfx::IntPoint(tile_width / 2, tile_height / 2);
@@ -170,6 +185,7 @@ void ChessWidget::mousedown_event(GUI::MouseEvent& event)
     if (event.button() == GUI::MouseButton::Right) {
         if (m_dragging_piece) {
             m_dragging_piece = false;
+            m_available_moves.clear();
         } else {
             m_current_marking.from = mouse_to_square(event);
         }
@@ -183,6 +199,13 @@ void ChessWidget::mousedown_event(GUI::MouseEvent& event)
         m_dragging_piece = true;
         m_drag_point = event.position();
         m_moving_square = square;
+
+        m_board.generate_moves([&](Chess::Move move) {
+            if (move.from == m_moving_square) {
+                m_available_moves.append(move.to);
+            }
+            return IterationDecision::Continue;
+        });
     }
 
     update();
@@ -211,6 +234,7 @@ void ChessWidget::mouseup_event(GUI::MouseEvent& event)
         return;
 
     m_dragging_piece = false;
+    m_available_moves.clear();
 
     auto target_square = mouse_to_square(event);
 
diff --git a/Userland/Games/Chess/ChessWidget.h b/Userland/Games/Chess/ChessWidget.h
index 772fe3f24a..c2d4320cce 100644
--- a/Userland/Games/Chess/ChessWidget.h
+++ b/Userland/Games/Chess/ChessWidget.h
@@ -142,6 +142,8 @@ private:
     Gfx::IntPoint m_drag_point;
     bool m_dragging_piece { false };
     bool m_drag_enabled { true };
+    bool m_show_available_moves { true };
+    Vector<Chess::Square> m_available_moves;
     RefPtr<Engine> m_engine;
     bool m_coordinates { true };
 };