implemented en passant

src/controller/controller.py

@@ -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

@@ -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
@@ -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(CastleSide.King)
+                ret._white_castling_rights.add(CastleSide.King)
             if c == "Q":
-                ret._white_castling_write.add(CastleSide.Queen)
+                ret._white_castling_rights.add(CastleSide.Queen)
             if c == "k":
-                ret._black_castling_write.add(CastleSide.King)
+                ret._black_castling_rights.add(CastleSide.King)
             if c == "q":
-                ret._black_castling_write.add(CastleSide.Queen)
+                ret._black_castling_rights.add(CastleSide.Queen)
 
         # -- En passant target
         if position[index] != "-":
@@ -131,13 +131,29 @@ class Board:
                         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)]
+                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 castling_writes_for(self, colour: Colour) -> set[CastleSide]:
+    def is_checkmate_for(self, colour: Colour) -> bool:
-        return self._white_castling_write if colour == Colour.WHITE else self._black_castling_write
+        """ 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) 
@@ -145,15 +161,18 @@ class Board:
         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
+
+        # -- Actually make the move
         pieces_moving, other_pieces = (ret._white, ret._black) if piece.colour == Colour.WHITE else (ret._black, ret._white)
 
         del pieces_moving[piece.pos]
@@ -161,6 +180,17 @@ class Board:
         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:
+            ret._en_passant_target = None
+
+        # -- Handle castling (just move the rook over)
         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..."
@@ -175,24 +205,25 @@ class Board:
             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_write = set()
+                ret._white_castling_rights = set()
 
             if type(piece) == Rook:
-                if piece.pos.x == 0 and CastleSide.Queen in ret._white_castling_write:
+                if piece.pos.x == 0 and CastleSide.Queen in ret._white_castling_rights:
-                    ret._white_castling_write.remove(CastleSide.Queen)
+                    ret._white_castling_rights.remove(CastleSide.Queen)
-                elif piece.pos.x == 7 and CastleSide.King in ret._white_castling_write:
+                elif piece.pos.x == 7 and CastleSide.King in ret._white_castling_rights:
-                    ret._white_castling_write.remove(CastleSide.King)
+                    ret._white_castling_rights.remove(CastleSide.King)
         else:
             if type(piece) == King:
-                ret._black_castling_write = set()
+                ret._black_castling_rights = set()
 
             if type(piece) == Rook:
-                if piece.pos.x == 0 and CastleSide.Queen in ret._black_castling_write:
+                if piece.pos.x == 0 and CastleSide.Queen in ret._black_castling_rights:
-                    ret._black_castling_write.remove(CastleSide.Queen)
+                    ret._black_castling_rights.remove(CastleSide.Queen)
-                elif piece.pos.x == 7 and CastleSide.King in ret._black_castling_write:
+                elif piece.pos.x == 7 and CastleSide.King in ret._black_castling_rights:
-                    ret._black_castling_write.remove(CastleSide.King)
+                    ret._black_castling_rights.remove(CastleSide.King)
 
 
         return ret

src/logic/move.py

@@ -8,11 +8,13 @@ class CastleSide(Enum):
     Queen = "O-O-O"
 
 class Move:
-    def __init__(self, piece: "Piece", pos: Position,/, is_capturing: bool = False, castle_side: CastleSide = CastleSide.Neither) -> 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")

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

@@ -19,13 +19,15 @@ class King(Piece):
                     if not board_after_move.is_check_for(self.colour):
                         ret.append(move)
 
-        # -- Castles
+        if board.is_check_for(self.colour):
-        castling_writes = board.castling_writes_for(self.colour)
+            return self.keep_only_blocking(ret, board)
-        if len(castling_writes) == 0:
-            return ret
-        print(castling_writes)
 
-        if CastleSide.King in castling_writes:
+        # -- 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
@@ -43,7 +45,7 @@ class King(Piece):
             if clear:
                 ret.append(Move(self, Position(6, self.pos.y), castle_side=CastleSide.King))
 
-        if CastleSide.Queen in castling_writes:
+        if CastleSide.Queen in castling_rights:
             clear = True
             for dx in range(1, 3):
                 x = self.pos.x - dx
@@ -62,8 +64,6 @@ class King(Piece):
             if clear:
                 ret.append(Move(self, Position(2, self.pos.y), castle_side=CastleSide.Queen))
 
-        print(ret)
-
         return ret
 
 

src/logic/pieces/knight.py

@@ -4,7 +4,7 @@ class Knight(Piece):
     def letter(self):
         return "n"
 
-    def legal_moves(self, board: "Board") -> list["Move"]:
+    def legal_moves(self, board: "Board", / , looking_for_check = False) -> list["Move"]:
         ret = []
         for dx, dy in [
             (+2, +1), (+1, +2), # north east
@@ -15,5 +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

@@ -3,7 +3,7 @@ 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?
@@ -24,17 +24,32 @@ class Pawn(Piece):
             if capturable_piece.colour != self.colour:
                 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(Move(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(Move(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

@@ -7,6 +7,9 @@ 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
@@ -16,6 +19,14 @@ class Piece:
     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):
@@ -50,5 +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/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
@@ -60,6 +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")

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