implemented en passant

legal moves

src/controller/controller.py

@@ -40,11 +40,11 @@ class Controller:
 
     def on_tile_selected(self, x: int, y: int) -> None:
         pos = Position(x, y)
-        print(f"Clicked on {pos.to_algebraic()}")
 
         piece = self._board.piece_at(x, y)
 
-        if self._selected_piece is None or (piece is not None and piece != self._selected_piece):
+        if self._selected_piece is None \
+            or (piece is not None and piece != self._selected_piece and piece.colour == self._selected_piece.colour):
             self._show_legal_moves(pos)
         else:
             legal_moves_positions = [move for move in self._legal_moves if move.pos == pos]
@@ -55,3 +55,9 @@ class Controller:
             else:
                 move = legal_moves_positions[0]
                 self._make_move(move)
+
+        if self._board.is_checkmate_for(self._board._turn):
+            self._view.notify_checkmate(self._board._turn)
+            
+        if self._board.is_stalemate_for(self._board._turn):
+            self._view.notify_stalemate(self._board._turn)

src/logic/board.py

@@ -1,4 +1,4 @@
-from logic.move import Move
+from logic.move import CastleSide, Move
 from logic.pieces.bishop import Bishop
 from logic.pieces.king import King
 from logic.pieces.knight import Knight
@@ -15,8 +15,8 @@ class Board:
         self._white: dict[Position, Piece] = {}
         self._black: dict[Position, Piece] = {}
         self._turn = None
-        self._white_castling_write = set()
+        self._white_castling_rights = set()
-        self._black_castling_write = set()
+        self._black_castling_rights = set()
         self._en_passant_target = None
 
     @staticmethod
@@ -76,7 +76,7 @@ class Board:
             ret._turn = Colour.BLACK
         else:
             raise ValueError(f"The FEN position is malformed, the active colour should be either 'w' or 'b', but is '{position[index]}'")
-        index += 1
+        index += 2
 
 
         # -- Castling Rights
@@ -88,13 +88,13 @@ class Board:
             sides = "kq"
             assert c in sides or c in sides.upper(), f"The FEN position is malformed, the castling rights should be either k or q (both either lower- or upper-case), instead is '{c}'"
             if c == "K":
-                ret._white_castling_write.add(Board.KING_SIDE_CASTLE)
+                ret._white_castling_rights.add(CastleSide.King)
             if c == "Q":
-                ret._white_castling_write.add(Board.QUEEN_SIDE_CASTLE)
+                ret._white_castling_rights.add(CastleSide.Queen)
             if c == "k":
-                ret._black_castling_write.add(Board.KING_SIDE_CASTLE)
+                ret._black_castling_rights.add(CastleSide.King)
             if c == "q":
-                ret._black_castling_write.add(Board.QUEEN_SIDE_CASTLE)
+                ret._black_castling_rights.add(CastleSide.Queen)
 
         # -- En passant target
         if position[index] != "-":
@@ -113,31 +113,117 @@ class Board:
             return white_piece
         return black_piece
 
+    def is_check_for(self, colour: Colour) -> bool:
+        """ Is it check for the defending colour passed as parameter """
+        defending_pieces, attacking_pieces = (self._white, self._black) if colour == Colour.WHITE else (self._black, self._white)
+
+        kings = [piece for piece in defending_pieces.values() if type(piece) == King]
+        assert len(kings) == 1, f"We have more than one king for {colour}, that is no buono..."
+        king = kings[0]
+
+        for piece in attacking_pieces.values():
+            possible_pos = []
+            if type(piece) == King: 
+                # special case for the king, because it creates infinite recursion (since he looks if he's walking into a check)
+                for dx in [-1, 0, 1]:
+                    for dy in [-1, 0, 1]:
+                        x, y = piece.pos.x + dx, piece.pos.y + dy
+                        if Position.is_within_bounds(x, y):
+                            possible_pos.append(Position(x, y))
+            else:
+                possible_pos += [move.pos for move in piece.legal_moves(self, looking_for_check=True)]
+            if king.pos in possible_pos:
+                return True
+        return False
+
+    def is_checkmate_for(self, colour: Colour) -> bool:
+        """ Is it checkmate for the defending colour passed as parameter """
+        return self.is_check_for(colour) and self._no_legal_moves_for(colour)
+
+    def is_stalemate_for(self, colour: Colour) -> bool:
+        """ Is it stalemate for the defending colour passed as parameter """
+        return not self.is_check_for(colour) and self._no_legal_moves_for(colour)
+
+    def _no_legal_moves_for(self, colour: Colour) -> bool:
+        """ Return true if there are indeed no legal moves for the given colour (for checkmate or stalemate)"""
+        pieces = self._white if colour == Colour.WHITE else self._black
+        for piece in pieces.values():
+            if len(piece.legal_moves(self)) > 0:
+                return False
+        return True
+
+    def castling_rights_for(self, colour: Colour) -> set[CastleSide]:
+        return self._white_castling_rights if colour == Colour.WHITE else self._black_castling_rights
+
     def make_move(self, move: Move) -> "Board":
         dest_piece = self.piece_at(move.pos.x, move.pos.y) 
 
         if dest_piece:
             assert dest_piece.colour != move.piece.colour, "A piece cannot cannot eat another piece of the same colour"
 
+        # -- Copy current state
         ret = Board()
         ret._white = self._white.copy()
         ret._black = self._black.copy()
         ret._turn = Colour.WHITE if self._turn == Colour.BLACK else Colour.BLACK
-        ret._white_castling_write = self._white_castling_write.copy()
+        ret._white_castling_rights = self._white_castling_rights.copy()
-        ret._black_castling_write = self._black_castling_write.copy()
+        ret._black_castling_rights = self._black_castling_rights.copy()
-        ret._en_passant_target = self._en_passant_target
+
 
         piece = move.piece
 
-        if piece.colour == Colour.WHITE:
+        # -- Actually make the move
-            del ret._white[piece.pos]
+        pieces_moving, other_pieces = (ret._white, ret._black) if piece.colour == Colour.WHITE else (ret._black, ret._white)
-            ret._white[move.pos] = piece.move_to(move.pos)
+
-            if move.pos in ret._black:
+        del pieces_moving[piece.pos]
-                del ret._black[move.pos]
+        pieces_moving[move.pos] = piece.move_to(move.pos)
+        if move.pos in other_pieces:
+            del other_pieces[move.pos]
+
+        if move.en_passant:
+            pos_to_remove = Position(move.pos.x, move.pos.y + (1 if self._turn == Colour.BLACK else -1))
+            del other_pieces[pos_to_remove]
+
+        # -- Set en passant target if needed
+        if move.becomes_en_passant_target:
+            ret._en_passant_target = pieces_moving[move.pos]
         else:
-            del ret._black[piece.pos]
+            ret._en_passant_target = None
-            ret._black[move.pos] = piece.move_to(move.pos)
+
-            if move.pos in ret._white:
+        # -- Handle castling (just move the rook over)
-                del ret._white[move.pos]
+        if move.castle_side == CastleSide.King:
+            rook_pos = Position(7, piece.pos.y)
+            assert rook_pos in pieces_moving and type(pieces_moving[rook_pos]) == Rook, "Either rook is absent from the king side or you are trying to castle with something else than a rook..."
+            del pieces_moving[rook_pos]
+            new_rook_pos = Position(5, piece.pos.y)
+            pieces_moving[new_rook_pos] = Rook(new_rook_pos, piece.colour)
+
+        elif move.castle_side == CastleSide.Queen:
+            rook_pos = Position(0, piece.pos.y)
+            assert rook_pos in pieces_moving and type(pieces_moving[rook_pos]) == Rook, "Either rook is absent from the queen side or you are trying to castle with something else than a rook..."
+            del pieces_moving[rook_pos]
+            new_rook_pos = Position(3, piece.pos.y)
+            pieces_moving[new_rook_pos] = Rook(new_rook_pos, piece.colour)
+
+        # -- Check for castling rights
+        if piece.colour == Colour.WHITE:
+            if type(piece) == King:
+                ret._white_castling_rights = set()
+
+            if type(piece) == Rook:
+                if piece.pos.x == 0 and CastleSide.Queen in ret._white_castling_rights:
+                    ret._white_castling_rights.remove(CastleSide.Queen)
+                elif piece.pos.x == 7 and CastleSide.King in ret._white_castling_rights:
+                    ret._white_castling_rights.remove(CastleSide.King)
+        else:
+            if type(piece) == King:
+                ret._black_castling_rights = set()
+
+            if type(piece) == Rook:
+                if piece.pos.x == 0 and CastleSide.Queen in ret._black_castling_rights:
+                    ret._black_castling_rights.remove(CastleSide.Queen)
+                elif piece.pos.x == 7 and CastleSide.King in ret._black_castling_rights:
+                    ret._black_castling_rights.remove(CastleSide.King)
+
 
         return ret

src/logic/move.py

@@ -2,9 +2,19 @@
 from logic.position import Position
 from enum import Enum
 
+class CastleSide(Enum):
+    Neither = ""
+    King = "O-O"
+    Queen = "O-O-O"
+
 class Move:
-    def __init__(self, is_capturing: bool) -> None:
+    def __init__(self, piece: "Piece", pos: Position,/, is_capturing: bool = False, castle_side: CastleSide = CastleSide.Neither, en_passant: bool = False, becomes_en_passant_target: bool = False) -> None:
+        self.piece = piece
+        self.pos = pos
         self.is_capturing = is_capturing
+        self.castle_side = castle_side
+        self.becomes_en_passant_target = becomes_en_passant_target
+        self.en_passant = en_passant
 
     def to_algebraic(self) -> str:
         raise NotImplementedError("The move can't be translated to algbraic notation, as it was not implemented")
@@ -13,13 +23,18 @@ class Move:
     def from_algebraic(move: str) -> "Move":
         raise NotImplementedError("The move can't be translated from algbraic notation, as it was not implemented")
 
+    def __str__(self) -> str:
+        if self.castle_side == CastleSide.King:
+            return "O-O"
+        if self.castle_side == CastleSide.Queen:
+            return "O-O-O"
 
-class PieceMove(Move):
+        ret = ""
-    def __init__(self, piece: "Piece", pos: Position,/, is_capturing: bool = False) -> None:
+        if type(self.piece).__name__ != "Pawn":
-        super().__init__(is_capturing)
+            ret += self.piece.letter().upper()
-        self.piece = piece
-        self.pos = pos
 
-class Castle(Move, Enum):
+        ret += str(self.pos)
-    KING_SIDE_CASTLE = False
+        return ret
-    QUEEN_SIDE_CASTLE = False
+    
+    def __repr__(self) -> str:
+        return str(self)

src/logic/pieces/bishop.py

@@ -2,7 +2,7 @@ from logic.move import Move
 from .piece import Piece
 
 class Bishop(Piece):
-    def legal_moves(self, board: "Board") -> list[Move]:
+    def legal_moves(self, board: "Board", / , looking_for_check = False) -> list[Move]:
         ret = []
 
         # looking north east
@@ -17,5 +17,8 @@ class Bishop(Piece):
         # looking north west
         ret.extend(self._look_direction(board, -1, 1))
 
+        if not looking_for_check and board.is_check_for(self.colour):
+            return self.keep_only_blocking(ret, board)
+
         return ret
 

src/logic/pieces/king.py

@@ -1,5 +1,69 @@
+from logic.move import CastleSide, Move
+from logic.position import Position
 from .piece import Piece
 
 class King(Piece):
-    pass
+    def legal_moves(self, board: "Board") -> list[Move]:
+        ret = []
+
+        # -- Regular moves
+        for dx in [-1, 0, 1]:
+            for dy in [-1, 0, 1]:
+                if dx == 0 and dy == 0: # skip current position
+                    continue
+                x = self.pos.x + dx
+                y = self.pos.y + dy
+                move = self._move_for_position(board, x, y)
+                if move:
+                    board_after_move = board.make_move(move)
+                    if not board_after_move.is_check_for(self.colour):
+                        ret.append(move)
+
+        if board.is_check_for(self.colour):
+            return self.keep_only_blocking(ret, board)
+
+        # -- Castles
+        castling_rights = board.castling_rights_for(self.colour)
+        if len(castling_rights) == 0:
+            return ret
+
+        if CastleSide.King in castling_rights:
+            clear = True
+            for dx in range(1, 3):
+                x = self.pos.x + dx
+                y = self.pos.y
+                if board.piece_at(x, y) is not None:
+                    clear = False
+                    break
+
+                move = self._move_for_position(board, x, y)
+                board_after_move = board.make_move(move)
+                if board_after_move.is_check_for(self.colour):
+                    clear = False
+                    break
+
+            if clear:
+                ret.append(Move(self, Position(6, self.pos.y), castle_side=CastleSide.King))
+
+        if CastleSide.Queen in castling_rights:
+            clear = True
+            for dx in range(1, 3):
+                x = self.pos.x - dx
+                y = self.pos.y
+
+                if board.piece_at(x, y) is not None:
+                    clear = False
+                    break
+
+                move = self._move_for_position(board, x, y)
+                board_after_move = board.make_move(move)
+                if board_after_move.is_check_for(self.colour):
+                    clear = False
+                    break
+
+            if clear:
+                ret.append(Move(self, Position(2, self.pos.y), castle_side=CastleSide.Queen))
+
+        return ret
+
 

src/logic/pieces/knight.py

@@ -1,7 +1,10 @@
 from .piece import Piece
 
 class Knight(Piece):
-    def legal_moves(self, board: "Board") -> list["Move"]:
+    def letter(self):
+        return "n"
+
+    def legal_moves(self, board: "Board", / , looking_for_check = False) -> list["Move"]:
         ret = []
         for dx, dy in [
             (+2, +1), (+1, +2), # north east
@@ -12,5 +15,9 @@ class Knight(Piece):
             move = self._move_for_position(board, self.pos.x + dx, self.pos.y + dy)
             if move is not None:
                 ret.append(move)
+
+        if not looking_for_check and board.is_check_for(self.colour):
+            return self.keep_only_blocking(ret, board)
+
         return ret
 

src/logic/pieces/pawn.py

@@ -1,9 +1,9 @@
-from logic.move import Move, PieceMove
+from logic.move import Move
 from logic.pieces.piece import Colour, Piece
 from logic.position import Position
 
 class Pawn(Piece):
-    def legal_moves(self, board) -> list[Move]:
+    def legal_moves(self, board, / , looking_for_check = False) -> list[Move]:
         ret = []
 
         # can we capture to the left?
@@ -13,7 +13,7 @@ class Pawn(Piece):
             (self.colour == Colour.BLACK and (capturable_piece := board.piece_at(self.pos.x - 1, self.pos.y - 1)))
         ):
             if capturable_piece.colour != self.colour:
-                ret.append(PieceMove(self, capturable_piece.pos, is_capturing = True))
+                ret.append(Move(self, capturable_piece.pos, is_capturing = True))
 
         # can we capture to the right?
         if self.pos.x < 7 and (
@@ -22,19 +22,34 @@ class Pawn(Piece):
             (self.colour == Colour.BLACK and (capturable_piece := board.piece_at(self.pos.x + 1, self.pos.y - 1)))
         ):
             if capturable_piece.colour != self.colour:
-                ret.append(PieceMove(self, capturable_piece.pos, is_capturing = True))
+                ret.append(Move(self, capturable_piece.pos, is_capturing = True))
 
+        # -- Can we capture en passant?
+        if board._en_passant_target is not None and \
+            board._en_passant_target.pos.y == self.pos.y and (
+                board._en_passant_target.pos.x == self.pos.x - 1
+                or board._en_passant_target.pos.x == self.pos.x + 1
+        ):
+            if board._en_passant_target.colour != self.colour:
+                old_pos = board._en_passant_target.pos
+                new_pos = Position(old_pos.x, old_pos.y + (1 if self.colour == Colour.WHITE else -1))
+                ret.append(Move(self, new_pos, is_capturing = True, en_passant = True))
+
+        # -- Normal moves
         if self.colour == Colour.WHITE:
             for dy in range(1, 3 if self.pos.y == 1 else 2):
                 if self.pos.y + dy > 7 or board.piece_at(self.pos.x, self.pos.y + dy):
                     break
                 pos = Position(self.pos.x, self.pos.y + dy)
-                ret.append(PieceMove(self, pos))
+                ret.append(Move(self, pos, becomes_en_passant_target=dy==2))
         else:
             for dy in range(1, 3 if self.pos.y == 6 else 2):
                 if self.pos.y - dy < 0 or board.piece_at(self.pos.x, self.pos.y - dy):
                     break
                 pos = Position(self.pos.x, self.pos.y - dy)
-                ret.append(PieceMove(self, pos))
+                ret.append(Move(self, pos, becomes_en_passant_target=dy==2))
+
+        if not looking_for_check and board.is_check_for(self.colour):
+            return self.keep_only_blocking(ret, board)
 
         return ret

src/logic/pieces/piece.py

@@ -1,4 +1,4 @@
-from logic.move import Move, PieceMove
+from logic.move import Move
 from logic.position import Position
 from enum import Enum
 
@@ -7,12 +7,26 @@ class Colour(Enum):
     WHITE = "white"
     BLACK = "black"
 
+    def __str__(self) -> str:
+        return self.value
+
 class Piece:
     def __init__(self, pos: Position, colour: Colour) -> None:
         self.pos = pos
         assert colour == Colour.WHITE or colour == Colour.BLACK, "The colour of the piece must be either Piece.WHITE or Piece.BLACK"
         self.colour = colour
 
+    def letter(self):
+        return type(self).__name__[0].lower()
+
+    def keep_only_blocking(self, candidates: list[Move], board: "Board") -> list[Move]:
+        ret = []
+        for move in candidates:
+            board_after_move = board.make_move(move)
+            if not board_after_move.is_check_for(self.colour):
+                ret.append(move)
+        return ret
+
     def _look_direction(self, board: "Board", mult_dx: int, mult_dy: int):
         ret = []
         for d in range(1, 8):
@@ -34,10 +48,10 @@ class Piece:
         piece = board.piece_at(x, y) 
 
         if piece is None:
-            return PieceMove(self, Position(x, y))
+            return Move(self, Position(x, y))
 
         if piece.colour != self.colour:
-            return PieceMove(self, Position(x, y), is_capturing=True)
+            return Move(self, Position(x, y), is_capturing=True)
         return None
 
     def position(self) -> Position:
@@ -47,5 +61,5 @@ class Piece:
         ret = type(self)(pos, self.colour)
         return ret
 
-    def legal_moves(self, board: "Board") -> list["Move"]:
+    def legal_moves(self, board: "Board", / , looking_for_check = False) -> list["Move"]:
         raise NotImplementedError(f"Can't say what the legal moves are for {type(self).__name__}, the method hasn't been implemented yet")

src/logic/pieces/queen.py

@@ -2,7 +2,7 @@ from logic.move import Move
 from .piece import Piece
 
 class Queen(Piece):
-    def legal_moves(self, board: "Board") -> list[Move]:
+    def legal_moves(self, board: "Board", / , looking_for_check = False) -> list[Move]:
         ret = []
 
         # looking north east
@@ -29,4 +29,7 @@ class Queen(Piece):
         # looking north
         ret.extend(self._look_direction(board, 0, 1))
 
+        if not looking_for_check and board.is_check_for(self.colour):
+            return self.keep_only_blocking(ret, board)
+
         return ret

src/logic/pieces/rook.py

@@ -2,7 +2,7 @@ from logic.move import Move
 from .piece import Piece
 
 class Rook(Piece):
-    def legal_moves(self, board: "Board") -> list[Move]:
+    def legal_moves(self, board: "Board", / , looking_for_check = False) -> list[Move]:
         ret = []
 
         # looking east
@@ -17,4 +17,7 @@ class Rook(Piece):
         # looking north
         ret.extend(self._look_direction(board, 0, 1))
 
+        if not looking_for_check and board.is_check_for(self.colour):
+            return self.keep_only_blocking(ret, board)
+
         return ret

src/logic/position.py

@@ -29,8 +29,7 @@ class Position:
         return hash((self.x, self.y))
 
     def __str__(self) -> str:
-        return f"{self.x, self.y}"
+        return f"{Position._FILES[self.x]}{Position._RANKS[self.y]}"
 
     def __repr__(self) -> str:
         return str(self)
-

src/view/gui.py

@@ -1,4 +1,5 @@
 import tkinter as tk
+from tkinter import messagebox
 from typing import Type
 from PIL import ImageTk, Image
 import os
@@ -37,8 +38,6 @@ class GUI(View):
 
         path = os.path.join(root, f"{"white" if colour == Colour.WHITE else "black"}-{piece_name}.png")
         img = Image.open(path)
-        size = int(self.tile_size * .85)
-        # img = img.resize((size, size))
 
         if img.mode == "LA":
             img = img.convert(mode="RGBA")
@@ -62,6 +61,12 @@ class GUI(View):
 
         self._controller.on_tile_selected(x, y)
 
+    def notify_checkmate(self, colour: Colour) -> None:
+        messagebox.showinfo("Checkmate",  f"{colour} is currently checkmated") 
+        
+    def notify_stalemate(self, colour: Colour) -> None:
+        messagebox.showinfo("Stalemate",  f"{colour} is currently stalemated") 
+        
 
     def update_board(self, board: Board, selected_piece: Piece, legal_moves: list[Move]) -> None:
         self.canvas.delete("all")
@@ -92,17 +97,29 @@ class GUI(View):
                 if selected_piece is not None:
                     possible_positions = [move.pos for move in legal_moves] 
                     if pos in possible_positions:
-                        radius = .15 * self.tile_size
                         colour = circle_colours[(x + y) % 2]
-                        self.canvas.create_oval(
+                        move = [move for move in legal_moves if move.pos == pos][0]
-                            (x + .5) * self.tile_size - radius,
+                        if move.is_capturing:
-                            (y + .5) * self.tile_size - radius,
+                            radius = .40 * self.tile_size
-                            (x + .5) * self.tile_size + radius,
+                            self.canvas.create_oval(
-                            (y + .5) * self.tile_size + radius,
+                                (x + .5) * self.tile_size - radius,
-                            fill=colour,
+                                (y + .5) * self.tile_size - radius,
-                            outline=colour,
+                                (x + .5) * self.tile_size + radius,
-                        )
+                                (y + .5) * self.tile_size + radius,
-
+                                fill="",
+                                outline=colour,
+                                width=.075 * self.tile_size,
+                            )
+                        else:
+                            radius = .15 * self.tile_size
+                            self.canvas.create_oval(
+                                (x + .5) * self.tile_size - radius,
+                                (y + .5) * self.tile_size - radius,
+                                (x + .5) * self.tile_size + radius,
+                                (y + .5) * self.tile_size + radius,
+                                fill=colour,
+                                outline=colour,
+                            )
 
                 piece = board.piece_at(x, 7-y)
 

src/view/view.py

@@ -1,6 +1,6 @@
 from logic.board import Board
 from logic.move import Move
-from logic.pieces.piece import Piece
+from logic.pieces.piece import Colour, Piece
 
 
 class View:
@@ -13,6 +13,12 @@ class View:
     def update_board(self, board: Board, selected_piece: Piece, legal_moves: list[Move]) -> None:
         raise NotImplementedError(f"Can't update the board, the update_board() method of {type(self)} is not implemented")
 
+    def notify_checkmate(self, colour: Colour) -> None:
+        raise NotImplementedError(f"Can't notify of the checkmate, the notify_checkmate() method of {type(self)} is not implemented")
+
+    def notify_stalemate(self, colour: Colour) -> None:
+        raise NotImplementedError(f"Can't notify of the stalemate, the notify_stalemate() method of {type(self)} is not implemented")
+
     def set_controller(self, controller: "Controller") -> None:
         self._controller = controller