introduced parsing uci moves, conversion to fen nad algebraic support

app/chess_sim/test.py

@@ -69,7 +69,7 @@ class MoveType(Enum):
     NORMAL = auto()
     CASTLING_KINGSIDE = auto()
     CASTLING_QUEENSIDE = auto()
-    EN_PASSANT = auto() #todo: implement
+    EN_PASSANT = auto()
     PROMOTION = auto() #todo: implement
 
 @dataclass
@@ -142,7 +142,7 @@ class ChessBoard:
         row_height = 7 if color == Color.WHITE else 0
 
         # validate move using legal moves for the player color
-        legal = self.moves_basic(color)
+        legal = self.moves_unfiltered(color)
         if not any(m.m_from.p == move.m_from.p and m.m_to.p == move.m_to.p and m.move_type == move.move_type and  m.promotion_piece == move.promotion_piece for m in legal):
             return False
         if move.move_type == MoveType.NORMAL:
@@ -165,6 +165,14 @@ class ChessBoard:
             ks_rook_dest = BoardPos((row_height, 3))
             self.move_piece(king_src, king_dest)
             self.move_piece(ks_rook_src, ks_rook_dest)
+        
+        elif move.move_type == MoveType.EN_PASSANT:
+            # direction the enemys pawn moved in
+            en_passant_dir = 1 if color == Color.WHITE else -1
+            self.move_piece(move.m_from, move.m_to)
+            affected_pawn_pos = BoardPos((move.m_to.x - en_passant_dir, move.m_to.y))
+            captured = self.get_field(affected_pawn_pos)
+            self.fields[affected_pawn_pos.x][affected_pawn_pos.y].piece = None
 
         self.move_history.append((move, captured))
         self.num_moves += 1
@@ -184,7 +192,10 @@ class ChessBoard:
         return captured
 
     def get_field(self, pos: BoardPos) -> Optional[Piece]:
+        if not self.on_board(pos.x, pos.y):
+            return None
         return self.fields[pos.x][pos.y].piece
+    
     # returns false if there is no move to unmake
     def unmake_move(self) -> bool:
         if not self.move_history or len(self.move_history) == 0:
@@ -265,7 +276,7 @@ class ChessBoard:
         return 0 <= rr < 8 and 0 <= cc < 8
 
     # takes the color of the player whos possible moves will be returned
-    def moves_basic(self, color: Color) -> List[BoardMove]:
+    def moves_unfiltered(self, color: Color) -> List[BoardMove]:
         moves: List[BoardMove] = []
         for pos, piece in self.iter_pieces():
             if piece.color != color:
@@ -293,7 +304,20 @@ class ChessBoard:
                     if target_field.piece is None:
                         # empty target
                         if is_pawn_capture_ray:
-                            # pawn cant move diagonally into empty square
+                            move_history_len = len(self.move_history)
+                            # pawn can only move diagonally into an empty square during en passant, check for that
+                            en_passant_dir = 1 if color == Color.WHITE else -1
+                            if move_history_len > 0:
+                                # check if there is a pawn in the correct position
+                                if self.get_field(BoardPos((tr, tc - en_passant_dir))) == Piece(
+                                    PieceType.PAWN,
+                                    color.opposite,
+                                ):  
+                                    # check if the last move moved the pawn there from the starting square
+                                    last_move = self.move_history[move_history_len][0]
+
+                                    if last_move.m_from == BoardPos((tr, tc + en_passant_dir)) and last_move.m_to == BoardPos((tr, tc - en_passant_dir)): 
+                                        moves.append(BoardMove(pos, BoardPos((tr, tc))))
                             break
                         moves.append(BoardMove(pos, BoardPos((tr, tc))))
                         continue    
@@ -439,13 +463,13 @@ class ChessBoard:
         # maybe there is a better way of doing it, but for now this should suffice
 
         us_moves_wo_check = []
-        for move in self.moves_basic(color):
+        for move in self.moves_unfiltered(color):
             # do a move and then check, if the king is still in check
             # if it isnt, add the move to the possibles ones
             if not self.make_move(move, color):
                 raise ValueError(f"self.moves_basic created a move, which cannot be done (hopefully unreachable). move: {move}")
             
-            all_basic_enemy_moves = self.moves_basic(color.opposite)
+            all_basic_enemy_moves = self.moves_unfiltered(color.opposite)
             king_pos = self.pos_of_king(color)
             king_in_check = False
             for mv in all_basic_enemy_moves:
@@ -486,6 +510,125 @@ class ChessBoard:
             lines.append("".join(row_chars))
         return "\n".join(lines)
 
+    # https://en.wikipedia.org/wiki/Algebraic_notation_(chess)
+    @staticmethod
+    def pos_to_algebraic(pos: BoardPos) -> str:
+        file = chr(ord('a') + pos.y)
+        rank = str(8 - pos.x)
+        return f"{file}{rank}"
+
+    @staticmethod
+    def algebraic_to_pos(s: str) -> BoardPos:
+        if len(s) != 2:
+            raise ValueError("invalid algebraic square")
+        col = ord(s[0].lower()) - ord('a')
+        row = 8 - int(s[1])
+        return BoardPos((row, col))
+
+    # https://www.chess.com/de/terms/forsyth-edwards-notation-fen
+    def to_fen(self) -> str:
+        # piece placement
+        ranks: List[str] = []
+
+        for r in range(8):
+            empty = 0
+            row_str = ""
+            for c in range(8):
+                p = self.fields[r][c].piece
+                if p is None:
+                    empty += 1
+                else:
+                    if empty > 0:
+                        row_str += str(empty)
+                        empty = 0
+                    row_str += p.char()
+            if empty > 0:
+                row_str += str(empty)
+            ranks.append(row_str)
+        placement = "/".join(ranks)
+
+        active = 'w' if (self.num_moves % 2) == 0 else 'b'
+
+        # castling availability
+        castling = ''
+        # white K/Q
+        if (self.fields[7][4].piece is not None and self.fields[7][4].piece.type == PieceType.KING and self.fields[7][4].piece.color == Color.WHITE
+                and self.fields[7][7].piece is not None and self.fields[7][7].piece.type == PieceType.ROOK and self.fields[7][7].piece.color == Color.WHITE
+                and not self.has_piece_moved(BoardPos((7,4))) and not self.has_piece_moved(BoardPos((7,7)))):
+            castling += 'K'
+        if (self.fields[7][4].piece is not None and self.fields[7][4].piece.type == PieceType.KING and self.fields[7][4].piece.color == Color.WHITE
+                and self.fields[7][0].piece is not None and self.fields[7][0].piece.type == PieceType.ROOK and self.fields[7][0].piece.color == Color.WHITE
+                and not self.has_piece_moved(BoardPos((7,4))) and not self.has_piece_moved(BoardPos((7,0)))):
+            castling += 'Q'
+        # black k/q
+        if (self.fields[0][4].piece is not None and self.fields[0][4].piece.type == PieceType.KING and self.fields[0][4].piece.color == Color.BLACK
+                and self.fields[0][7].piece is not None and self.fields[0][7].piece.type == PieceType.ROOK and self.fields[0][7].piece.color == Color.BLACK
+                and not self.has_piece_moved(BoardPos((0,4))) and not self.has_piece_moved(BoardPos((0,7)))):
+            castling += 'k'
+        if (self.fields[0][4].piece is not None and self.fields[0][4].piece.type == PieceType.KING and self.fields[0][4].piece.color == Color.BLACK
+                and self.fields[0][0].piece is not None and self.fields[0][0].piece.type == PieceType.ROOK and self.fields[0][0].piece.color == Color.BLACK
+                and not self.has_piece_moved(BoardPos((0,4))) and not self.has_piece_moved(BoardPos((0,0)))):
+            castling += 'q'
+        if castling == '':
+            castling = '-'
+
+        # en passant target square: if last move was a pawn double-step, set the square behind it
+        ep = '-'
+        if len(self.move_history) > 0:
+            last_move = self.move_history[-1][0]
+            moved_piece = self.get_field(last_move.m_to)
+            if moved_piece is not None and moved_piece.type == PieceType.PAWN and abs(last_move.m_from.x - last_move.m_to.x) == 2:
+                passed_row = (last_move.m_from.x + last_move.m_to.x) // 2
+                passed_col = last_move.m_from.y
+                ep = self.pos_to_algebraic(BoardPos((passed_row, passed_col)))
+
+        # todo half moves not yet tracked
+        halfmove = 0
+
+        # fullmove number
+        fullmove = (self.num_moves // 2) + 1
+
+        return f"{placement} {active} {castling} {ep} {halfmove} {fullmove}"
+
+    # https://backscattering.de/chess/uci/
+    def make_move_uci(self, uci: str, color: Color) -> bool:
+        if uci == '0000':
+            return False
+        if len(uci) < 4:
+            return False
+        src = self.algebraic_to_pos(uci[0:2])
+        dst = self.algebraic_to_pos(uci[2:4])
+        promo_piece = None
+        if len(uci) == 5:
+            pc = uci[4].lower()
+            mapping = {'q': PieceType.QUEEN, 'r': PieceType.ROOK, 'b': PieceType.BISHOP, 'n': PieceType.KNIGHT}
+            promo_piece = mapping.get(pc, None)
+
+        moving = self.get_field(src)
+        if moving is None or moving.color != color:
+            return False
+
+        # detect castling by king moving two files
+        move_type = MoveType.NORMAL
+        if moving.type == PieceType.KING and abs(src.y - dst.y) == 2:
+            move_type = MoveType.CASTLING_KINGSIDE if dst.y > src.y else MoveType.CASTLING_QUEENSIDE
+        else:
+            # en passant detection: pawn moves diagonally to empty square
+            if moving.type == PieceType.PAWN and src.y != dst.y and self.get_field(dst) is None:
+                if len(self.move_history) > 0:
+                    # make sure the last move was a pawn move for this en passant to be possible
+                    last = self.move_history[-1][0]
+                    if last.m_from.x - last.m_to.x == 2 and last.m_to.x == src.x and last.m_to.y == dst.y:
+                        move_type = MoveType.EN_PASSANT
+
+        # promotion
+        if promo_piece is not None:
+            move_type = MoveType.PROMOTION
+
+        bm = BoardMove(src, dst, move_type, promotion_piece=promo_piece)
+        return self.make_move(bm, color)
+
+
 
 def play_random_game(board: Optional[ChessBoard] = None, max_moves: int = 400, verbose: bool = False) -> Tuple[ ChessBoard, int]:
     if board is None:
@@ -514,13 +657,9 @@ def play_random_game(board: Optional[ChessBoard] = None, max_moves: int = 400, v
         ok = board.make_move(move, current)
         # debug assert
         if not ok:
-            # if an unexpected failure happens, break and treat as draw
             if verbose:
                 print(f"make_move returned False for move {move} by {current}")
             return  board, moves_played
-        if move.move_type == MoveType.CASTLING_KINGSIDE or move.move_type == MoveType.CASTLING_QUEENSIDE:
-            print("hell yeah we castled")
-            raise ValueError("casling")
         moves_played += 1
         if verbose:
             print(f"{moves_played:03d}: {current.name} played {move}\nboard:\n{board}")
@@ -611,13 +750,13 @@ def main():
         raise AssertionError(f"initial board mismatch:\nexpected:\n{expected_start}\n\nactual:\n{actual_start}")
 
     # test num moves
-    mvs = default_brd.moves_basic(Color.BLACK)
+    mvs = default_brd.moves_unfiltered(Color.BLACK)
     expected_move_count = 20  # 16 pawn moves and 4 knight
     if len(mvs) != expected_move_count:
         raise AssertionError(f"initial move count for black mismatch: expected {expected_move_count}, got {len(mvs)}")
     
 
-    mvs = default_brd.moves_basic(Color.WHITE)
+    mvs = default_brd.moves_unfiltered(Color.WHITE)
     expected_move_count = 20  # 16 pawn moves and 4 knight
     if len(mvs) != expected_move_count:
         raise AssertionError(f"Initial move count for white mismatch: expected {expected_move_count}, got {len(mvs)}")