simoncreates
551 lines
19 KiB
Python
551 lines
19 KiB
Python
from enum import Enum, auto
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from dataclasses import dataclass
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from typing import Iterator, Optional, List, Tuple
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import random
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class PieceType(Enum):
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PAWN = auto()
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KNIGHT = auto()
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BISHOP = auto()
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ROOK = auto()
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QUEEN = auto()
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KING = auto()
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class Color(Enum):
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WHITE = auto()
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BLACK = auto()
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@property
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def opposite(self) -> "Color":
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if self == Color.WHITE:
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return Color.BLACK
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else:
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return Color.WHITE
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@dataclass
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class BoardPos:
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p: Tuple[int, int]
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def __str__(self) -> str:
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return f"({self.p[0]},{self.p[1]})"
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@property
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def x (self) -> int:
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return self.p[0]
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@property
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def y (self) -> int:
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return self.p[1]
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@dataclass
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class Piece:
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type: PieceType
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color: Color
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# uppercase = White, lowercase = Black
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def char(self) -> str:
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mapping = {
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PieceType.PAWN: "p",
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PieceType.KNIGHT: "n",
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PieceType.BISHOP: "b",
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PieceType.ROOK: "r",
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PieceType.QUEEN: "q",
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PieceType.KING: "k",
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}
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ch = mapping[self.type]
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return ch.upper() if self.color == Color.WHITE else ch
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def __str__(self) -> str:
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return self.char()
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def __repr__(self) -> str:
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return f"Piece({self.type.name},{self.color.name})"
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class MoveType(Enum):
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NORMAL = auto()
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CASTLING_KINGSIDE = auto() #todo: implement
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CASTLING_QUEENSIDE = auto() #todo: implement
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EN_PASSANT = auto() #todo: implement
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PROMOTION = auto() #todo: implement
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@dataclass
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class BoardMove:
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m_from: BoardPos
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m_to: BoardPos
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move_type: MoveType = MoveType.NORMAL #todo: implement and handle
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promotion_piece: Optional[PieceType] = None #todo: implement and handle
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def __str__(self) -> str:
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return f"{self.m_from}->{self.m_to}"
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@dataclass
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class BoardField:
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piece: Optional[Piece] = None
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def __str__(self) -> str:
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return str(self.piece) if self.piece is not None else "."
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@dataclass
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class ChessBoard:
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fields: List[List[BoardField]]
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num_moves: int
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move_history: List[Tuple['BoardMove', Optional[Piece]]]
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def place(self, row: int, col: int, piece_type: PieceType, color: Color):
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self.fields[row][col].piece = Piece(piece_type, color)
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# initialize default starting position
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@classmethod
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def init_default(cls) -> "ChessBoard":
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brd = cls(
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[[BoardField() for _ in range(8)] for _ in range(8)], 0, []
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)
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# place pawns
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for col in range(8):
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brd.place(1, col, PieceType.PAWN, Color.BLACK)
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brd.place(6, col, PieceType.PAWN, Color.WHITE)
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# back rank order
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back_rank = [
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PieceType.ROOK,
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PieceType.KNIGHT,
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PieceType.BISHOP,
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PieceType.QUEEN,
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PieceType.KING,
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PieceType.BISHOP,
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PieceType.KNIGHT,
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PieceType.ROOK,
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]
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# place black back rank
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for col, piece_type in enumerate(back_rank):
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brd.place(0, col, piece_type, Color.BLACK)
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# place white back rank
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for col, piece_type in enumerate(back_rank):
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brd.place(7, col, piece_type, Color.WHITE)
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return brd
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# attempt to make move for color
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# returns true on success
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def make_move(self, move: BoardMove, color: Color) -> bool:
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sr, sc = move.m_from.p
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tr, tc = move.m_to.p
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src_field = self.fields[sr][sc]
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# validate move using legal moves for the player color
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legal = self.moves_basic(color)
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if not any(m.m_from.p == move.m_from.p and m.m_to.p == move.m_to.p for m in legal):
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return False
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# perform move and record history for unmaking
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captured = self.fields[tr][tc].piece
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self.fields[tr][tc].piece = src_field.piece
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src_field.piece = None
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self.move_history.append((move, captured))
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self.num_moves += 1
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return True
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# returns false if there is no move to unmake
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def unmake_move(self) -> bool:
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if not self.move_history or len(self.move_history) == 0:
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return False
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move, captured = self.move_history.pop()
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sr, sc = move.m_from.p
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tr, tc = move.m_to.p
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moving_piece = self.fields[tr][tc].piece
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# restore
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self.fields[sr][sc].piece = moving_piece
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self.fields[tr][tc].piece = captured
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self.num_moves = max(0, self.num_moves - 1)
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return True
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def moves_unchecked(self, piece: Piece, pos: BoardPos) -> List[List[Tuple[int, int]]]:
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row, column = pos.p
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rays: List[List[Tuple[int, int]]] = []
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if piece.type == PieceType.KING:
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king_offsets = [(1, 1), (1, 0), (0, 1), (-1, -1), (-1, 0), (0, -1), (1, -1), (-1, 1)]
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rays.append([(row + dr, column + dc) for dr, dc in king_offsets])
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elif piece.type == PieceType.KNIGHT:
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knight_offsets = [
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(2, 1), (2, -1), (-2, 1), (-2, -1),
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(1, 2), (1, -2), (-1, 2), (-1, -2)
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]
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rays.append([(row + dr, column + dc) for dr, dc in knight_offsets])
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elif piece.type == PieceType.PAWN:
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# correct forward direction and start row depending on color
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if piece.color == Color.WHITE:
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forward = -1
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start_row = 6
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else:
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forward = 1
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start_row = 1
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forward_ray: List[Tuple[int, int]] = []
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forward_ray.append((row + forward, column))
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# if the pawn is at the start row, include the double-step
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if row == start_row:
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forward_ray.append((row + 2 * forward, column))
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rays.append(forward_ray)
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# capture moves
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captures = [(row + forward, column - 1), (row + forward, column + 1)]
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rays.extend([[(rr, cc)] for rr, cc in captures])
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elif piece.type == PieceType.BISHOP:
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directions = [(1, 1), (1, -1), (-1, 1), (-1, -1)]
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for dr, dc in directions:
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ray = []
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for k in range(1, 8):
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ray.append((row + k * dr, column + k * dc))
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rays.append(ray)
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elif piece.type == PieceType.ROOK:
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directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
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for dr, dc in directions:
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ray = []
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for k in range(1, 8):
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ray.append((row + k * dr, column + k * dc))
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rays.append(ray)
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elif piece.type == PieceType.QUEEN:
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directions = [
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(1, 0), (-1, 0), (0, 1), (0, -1),
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(1, 1), (1, -1), (-1, 1), (-1, -1)
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]
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for dr, dc in directions:
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ray = []
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for k in range(1, 8):
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ray.append((row + k * dr, column + k * dc))
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rays.append(ray)
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return rays
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def on_board(self, rr: int, cc: int) -> bool:
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return 0 <= rr < 8 and 0 <= cc < 8
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# takes the color of the player whos possible moves will be returned
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def moves_basic(self, color: Color) -> List[BoardMove]:
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moves: List[BoardMove] = []
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for pos, piece in self.iter_pieces():
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if piece.color != color:
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continue
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rays = self.moves_unchecked(piece, pos)
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for ray in rays:
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# detect pawn capture ray and dont allow movement in that ray without capturing
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is_pawn_capture_ray = (
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piece.type == PieceType.PAWN
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and len(ray) == 1
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and ray[0][1] != pos.y
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and abs(ray[0][0] - pos.x) == 1
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)
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# non sliding rays get treated individually
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non_sliding = piece.type in (PieceType.KNIGHT, PieceType.KING) or is_pawn_capture_ray
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for (tr, tc) in ray:
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if not self.on_board(tr, tc):
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if non_sliding:
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continue
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break
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target_field = self.fields[tr][tc]
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if target_field.piece is None:
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# empty target
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if is_pawn_capture_ray:
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# pawn cant move diagonally into empty square
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break
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moves.append(BoardMove(pos, BoardPos((tr, tc))))
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continue
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else:
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# occupied
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if target_field.piece.color == piece.color:
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break
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else:
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# opponent piece
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moves.append(BoardMove(pos, BoardPos((tr, tc))))
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break
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# manually adding castling
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row_height = 7 if color == Color.WHITE else 0
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expected_king_pos = BoardPos((row_height, 4))
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# if king moved
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if self.has_piece_moved(expected_king_pos):
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return moves
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expected_lhs_rook_pos = BoardPos((row_height, 0))
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expected_rhs_rook_pos = BoardPos((row_height, 7))
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# squares that must be empty between rook and king
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lhs_pieces_inbetween = [BoardPos((row_height, i)) for i in range(1, 4)] # cols 1,2,3
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rhs_pieces_inbetween = [BoardPos((row_height, i)) for i in range(5, 7)] # cols 5,6
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# squares that must not be attacked by the opponent
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lhs_fields_attacked = [BoardPos((row_height, i)) for i in (4, 3, 2)]
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rhs_fields_attacked = [BoardPos((row_height, i)) for i in (4, 5, 6)]
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if (not self.has_piece_moved(expected_lhs_rook_pos)
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and self.are_pieces_none(lhs_pieces_inbetween)
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and not self.are_fields_attacked(lhs_fields_attacked, color.opposite)):
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# todo: allow castling here
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pass
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if (not self.has_piece_moved(expected_rhs_rook_pos)
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and self.are_pieces_none(rhs_pieces_inbetween)
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and not self.are_fields_attacked(rhs_fields_attacked, color.opposite)):
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# todo: allow castling here
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pass
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return moves
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def has_piece_moved(self, pos: BoardPos) -> bool:
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for move in self.move_history:
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if move[0].m_from == pos:
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return True
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elif move[0].m_to == pos:
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return True
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return False
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def are_pieces_none(self, positions: List[BoardPos]):
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are_gone = True
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for pos in positions:
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if not self.is_piece_none(pos):
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are_gone = False
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return are_gone
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def is_piece_none(self, pos: BoardPos) -> bool:
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piece = self.fields[pos.x][pos.y].piece
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if piece is None:
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return True
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else:
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return False
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def is_piece_of_type(self, pos: BoardPos, piece_type: PieceType) -> bool:
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piece = self.fields[pos.x][pos.y].piece
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if piece is None:
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return False
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return piece.type == piece_type
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def iter_pieces(self) -> Iterator[Tuple[BoardPos, Piece]]:
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for row_idx, row in enumerate(self.fields):
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for col_idx, field in enumerate(row):
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if field.piece is not None:
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yield BoardPos((row_idx, col_idx)), field.piece
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def pos_of_king(self, color: Color) -> BoardPos:
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for pos, piece in self.iter_pieces():
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if piece.type == PieceType.KING and piece.color == color:
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return pos
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raise ValueError("player has no king")
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# returns true if one field is actively being attacked
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def are_fields_attacked(self, fields: List[BoardPos], attacker_color: Color) -> bool:
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for field in fields:
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if self.is_field_attacked(field, attacker_color):
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return True
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return False
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# checks if the field is being actively attacked by any of the pieces of the attacker color
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# this "complicated" implementation was necessary to not rely on recursive calls
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def is_field_attacked(self, pos: BoardPos, attacker_color: Color) -> bool:
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# iterate opponent pieces and check whether they attack
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for attacker_pos, attacker in self.iter_pieces():
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if attacker.color != attacker_color:
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continue
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rays = self.moves_unchecked(attacker, attacker_pos)
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if attacker.type == PieceType.PAWN:
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# pawn attacks are the pawn capture rays only
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forward = -1 if attacker.color == Color.WHITE else 1
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for dc in (-1, 1):
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rr = attacker_pos.x + forward
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cc = attacker_pos.y + dc
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if not self.on_board(rr, cc):
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continue
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if BoardPos((rr, cc)) == pos:
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return True
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continue
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if attacker.type in (PieceType.KNIGHT, PieceType.KING):
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# non-sliding
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for (rr, cc) in rays[0]:
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if not self.on_board(rr, cc):
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continue
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if BoardPos((rr, cc)) == pos:
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return True
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continue
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# sliding pieces
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for ray in rays:
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for (rr, cc) in ray:
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if not self.on_board(rr, cc):
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break
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if BoardPos((rr, cc)) == pos:
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return True
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# stop at first occupied square (blocker)
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if self.fields[rr][cc].piece is not None:
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break
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return False
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# if a player does not have any moves, it has lost
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def generate_moves(self, color: Color) -> List[BoardMove]:
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# only moves after which the king is not in check are allowed
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# todo: the current method of checking what move will resolve the check is based on bruteforcing
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# maybe there is a better way of doing it, but for now this should suffice
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us_moves_wo_check = []
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for move in self.moves_basic(color):
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# do a move and then check, if the king is still in check
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# if it isnt, add the move to the possibles ones
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if not self.make_move(move, color):
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raise ValueError("self moves basic created a move, which cannot be done (hopefully unreachable)")
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all_basic_enemy_moves = self.moves_basic(color.opposite)
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king_pos = self.pos_of_king(color)
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king_in_check = False
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for mv in all_basic_enemy_moves:
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if mv.m_to == king_pos:
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king_in_check = True
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if not king_in_check:
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us_moves_wo_check.append(move)
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if not self.unmake_move():
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raise ValueError("failed to unmake move, shouldnt be an issue here")
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# check if our move lands directly on the enemies king, if it does, its illigal
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us_moves_rule_compliant = []
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king_pos = self.pos_of_king(color.opposite)
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for move in us_moves_wo_check:
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if move.m_to != king_pos:
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us_moves_rule_compliant.append(move)
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return us_moves_wo_check
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def __str__(self) -> str:
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"""
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example string repr of starting pos:
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rnbqkbnr
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pppppppp
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........
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........
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........
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........
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PPPPPPPP
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RNBQKBNR
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"""
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lines: List[str] = []
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for r in range(8):
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row_chars = [str(self.fields[r][c]) for c in range(8)]
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lines.append("".join(row_chars))
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return "\n".join(lines)
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def play_random_game(board: Optional[ChessBoard] = None, max_moves: int = 400, verbose: bool = False) -> Tuple[ ChessBoard, int]:
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if board is None:
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board = ChessBoard.init_default()
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current = Color.WHITE # white moves first
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moves_played = 0
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while moves_played < max_moves:
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legal = board.generate_moves(current)
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if not legal:
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# no legal moves
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if verbose:
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print(f"no legal moves for {current.name} after {moves_played} moves")
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return board, moves_played
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move = random.choice(legal)
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ok = board.make_move(move, current)
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# debug assert
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if not ok:
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# if an unexpected failure happens, break and treat as draw
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if verbose:
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print(f"make_move returned False for move {move} by {current}")
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return board, moves_played
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moves_played += 1
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if verbose:
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print(f"{moves_played:03d}: {current.name} played {move}\nboard:\n{board}")
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# check whether the captured piece was a king
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_, captured = board.move_history[-1]
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if captured is not None and captured.type == PieceType.KING:
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if verbose:
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print(f"king captured by {current.name} on move {moves_played}.")
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raise RuntimeWarning("this should not be possible")
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return board, moves_played
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current = current.opposite
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if verbose:
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print(f"reached move limit ({max_moves})")
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return board, moves_played
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def run_random_games(n: int = 100, max_moves: int = 400, verbose: bool = False):
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for i in range(n):
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final_board, moves = play_random_game(None, max_moves=max_moves, verbose=verbose and (i < 3))
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if verbose and (i < 3):
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print(f"game {i+1}: moves={moves}\nfinal_board:\n{final_board}")
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return
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# used only for testing purposesa
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def main():
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default_brd = ChessBoard.init_default()
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default_brd.generate_moves
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# standardized expected string for initial position
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expected_start = (
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"rnbqkbnr\n"
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"pppppppp\n"
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"........\n"
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"........\n"
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"........\n"
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"........\n"
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"PPPPPPPP\n"
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"RNBQKBNR"
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)
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# test string representation of board
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actual_start = str(default_brd)
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if actual_start != expected_start:
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raise AssertionError(f"initial board mismatch:\nexpected:\n{expected_start}\n\nactual:\n{actual_start}")
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|
|
|
# test num moves
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mvs = default_brd.moves_basic(Color.BLACK)
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expected_move_count = 20 # 16 pawn moves and 4 knight
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|
if len(mvs) != expected_move_count:
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raise AssertionError(f"initial move count for black mismatch: expected {expected_move_count}, got {len(mvs)}")
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|
|
|
|
|
mvs = default_brd.moves_basic(Color.WHITE)
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|
expected_move_count = 20 # 16 pawn moves and 4 knight
|
|
if len(mvs) != expected_move_count:
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|
raise AssertionError(f"Initial move count for white mismatch: expected {expected_move_count}, got {len(mvs)}")
|
|
play_random_game(verbose=True)
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|
|
|
print(f"all tests passed")
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|
|
|
|
|
if __name__ == '__main__':
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|
main()
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|
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|