Endgame Chess is our version of the capstone project for The Firehose Project, an intensive 15 week programming bootcamp. We are Team Endgame, 5 junior developers with different backgrounds working remotely to build the best chess app we can. With the support of our mentor, Travis Johnston, we followed Agile Methodology with weekly stand-ups to plan our sprints, kept our code in check using Git, and made sure everything worked with an extensive test suite. Some highlights include:

• Check and Mate Detection (view source)

        # Check Detection
        def check(users_id, opponent_id)
          opponent_pieces = pieces.where(user_id: opponent_id, captured: false)
          king = pieces.find_by(user_id: users_id, type: "King")
          opponent_pieces.each do |piece|
            return true if piece.valid_move?(king.row_position, king.col_position)
          end
          false
        end

        # Checkmate Detection
        def checkmate(id)
          current_pieces = pieces.where(user_id: id, captured: false)
          status = true
          current_pieces.each do |piece|
            8.times do |row|
              8.times do |col|
                next unless piece.reload.valid_move?(row, col)
                status = false unless checkmate_check(piece, row, col)
              end
            end
          end
          status
        end

        # Transaction for Checkmate Detection
        def checkmate_check(piece, row, col)
          status = true
          Piece.transaction do
            piece.move_to!(row, col)
            status = false unless determine_check
            fail ActiveRecord::Rollback
          end
          status
        end
      

• State is important in chess. To determine the state of the game, we loop through each of your opponent’s pieces each turn and test them against your King. If one of those pieces has a valid move, the game is in Check. Check is never the result of user error (except for in strategy) -- you can’t purposely move into Check.
• You’ll want to get out of Check as soon as possible, since Checkmate means game over. In order to determine Checkmate, we loop through each of your pieces and see whether they can a) avoid b) block or c) capture the opponent piece that has your King in check. These checks are run in database transaction to ensure that none of the movements the game tries are saved (inadvertently helping you out).
• Drag and Drop Movement (view source)

        // Drag and drop using jQuery draggable and droppable
        $('.move_mode').draggable({ containment: '.board'});
        $( '.piece' ).droppable({
          drop: function( event, ui ) {
            $(ui.draggable).detach().css({top: 0,left: 0});
            $(this).replaceWith(ui.draggable);
            var draggableId = ui.draggable.attr("id");
            var droppableId = $(this).attr("pos");
            var updateUrl = "/pieces/" + draggableId
            var row = droppableId[0];
            var col = droppableId[1];

            // Update piece via AJAX  
            $.ajax({
              type: 'PUT',
              url: updateUrl,
              dataType: 'json',
              data: { piece: { 
                      row_position: row, 
                      col_position: col 
              }},
              complete: function(){
                location.reload(true);
              }
            });
          }     
        });

        // Pusher for Real-Time Connection
        var pusher = new Pusher(ENV['pusher_key'], {
            encrypted: true
        });  

        var gameId = $('.pusherInfo').data('pusherinfo');

        var channel = pusher.subscribe(gameId);

        channel.bind('update-piece', function(data) {
          location.reload(true);
        });
      

• Through the magic of jQuery, pieces are simply picked up and put down where you want them to go. An AJAX request handles updating the database and a Websockets connection with Pusher handles refreshing the page for both you and your opponent. Not too shabby.