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ChessEngine.py
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ChessEngine.py
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import numpy as np
class GameState():
def __init__(self):
'''
creating a 8x8 2D Board, each element of the list has 2 characters.
the first character represents the color of the piece, 'b' for black and 'w' for white.
the second character represents the type of the piece, 'K'(King), 'Q' (Queen), 'R' (Rook), 'B' (Bishop), 'N' (Knight) and 'P' (Pawn).
'--' reprsents an empty space with no pieces.
'''
self.board = np.array([["bR", "bN", "bB", "bQ", "bK", "bB", "bN", "bR"],
["bP", "bP", "bP", "bP", "bP", "bP", "bP", "bP"],
["--", "--", "--", "--", "--", "--", "--", "--"],
["--", "--", "--", "--", "--", "--", "--", "--"],
["--", "--", "--", "--", "--", "--", "--", "--"],
["--", "--", "--", "--", "--", "--", "--", "--"],
["wP", "wP", "wP", "wP", "wP", "wP", "wP", "wP"],
["wR", "wN", "wB", "wQ", "wK", "wB", "wN", "wR"] ])
self.whiteToMove = True
self.moveLog = []
self.moveFunct = {"P": self.getPawnMoves, "R": self.getRookMoves, "N": self.getKnightMoves, "B": self.getBishopMoves,
"K": self.getKingMoves, "Q": self.getQueenMoves}
self.whiteKingLocation = (7, 4)
self.blackKingLocation = (0, 4)
self.inCheck = False
self.checkmate = False
self.stalemate = False
self.pins = []
self.checks = []
self.currentCastlingRight = CastleRights(True, True, True, True)
self.castleRightsLog = [CastleRights(self.currentCastlingRight.wks, self.currentCastlingRight.bks,
self.currentCastlingRight.wqs, self.currentCastlingRight.bqs)]
def makeMove(self, move):
self.board[move.startRow][move.startCol] = "--"
self.board[move.endRow][move.endCol] = move.pieceMoved
self.moveLog.append(move)
self.whiteToMove = not self.whiteToMove
#update the king's location if moved
if move.pieceMoved == "wK":
self.whiteKingLocation = (move.endRow, move.endCol)
elif move.pieceMoved == "bK":
self.blackKingLocation = (move.endRow, move.endCol)
#pawn promotion
if move.isPawnPromotion:
self.board[move.endRow][move.endCol] = move.pieceMoved[0] + "Q"
#castle move
if move.isCastleMove:
if move.endCol - move.startCol == 2 : #king side castle move
self.board[move.endRow][move.endCol-1] = self.board[move.endRow][move.endCol+1] #moves the rook
self.board[move.endRow][move.endCol+1] = '--' #erase old rook
else: #queenside castle move
self.board[move.endRow][move.endCol+1] = self.board[move.endRow][move.endCol-2] #moves the rook
self.board[move.endRow][move.endCol-2] = '--' #erase old rook
#update castling rights - whenever it is a king or a rook move
self.updateCastlingRights(move)
self.castleRightsLog.append(CastleRights(self.currentCastlingRight.wks, self.currentCastlingRight.bks,
self.currentCastlingRight.wqs, self.currentCastlingRight.bqs))
def undoMove(self):
if len(self.moveLog) != 0:
move = self.moveLog.pop()
self.board[move.startRow][move.startCol] = move.pieceMoved
self.board[move.endRow][move.endCol] = move.pieceCaptured
self.whiteToMove = not self.whiteToMove
if move.pieceMoved == "wK":
self.whiteKingLocation = (move.startRow, move.startCol)
elif move.pieceMoved == "bK":
self.blackKingLocation = (move.startRow, move.startCol)
#undo castling rights
self.castleRightsLog.pop() #get rid of the new castle rights from the move we are undoing
newRights = self.castleRightsLog[-1]
self.currentCastlingRight = CastleRights(newRights.wks, newRights.bks, newRights.wqs, newRights.bqs)
#undo castle move
if move.isCastleMove:
if move.endCol - move.startCol == 2: #kingside
self.board[move.endRow][move.endCol+1] = self.board[move.endRow][move.endCol-1]
self.board[move.endRow][move.endCol-1] = "--"
else: #queen side
self.board[move.endRow][move.endCol-2] = self.board[move.endRow][move.endCol+1]
self.board[move.endRow][move.endCol+1] = '--'
self.checkmate = False
self.stalemate = False
def restartGame(self):
self.board = np.array([["bR", "bN", "bB", "bQ", "bK", "bB", "bN", "bR"],
["bP", "bP", "bP", "bP", "bP", "bP", "bP", "bP"],
["--", "--", "--", "--", "--", "--", "--", "--"],
["--", "--", "--", "--", "--", "--", "--", "--"],
["--", "--", "--", "--", "--", "--", "--", "--"],
["--", "--", "--", "--", "--", "--", "--", "--"],
["wP", "wP", "wP", "wP", "wP", "wP", "wP", "wP"],
["wR", "wN", "wB", "wQ", "wK", "wB", "wN", "wR"] ])
self.whiteToMove = True
self.moveLog = []
self.whiteKingLocation = (7, 4)
self.blackKingLocation = (0, 4)
self.inCheck = False
self.checkmate = False
self.stalemate = False
self.pins = []
self.checks = []
self.currentCastlingRight = CastleRights(True, True, True, True)
self.castleRightsLog = [CastleRights(self.currentCastlingRight.wks, self.currentCastlingRight.bks,
self.currentCastlingRight.wqs, self.currentCastlingRight.bqs)]
def updateCastlingRights(self, move):
if move.pieceMoved == "wK":
self.currentCastlingRight.wks = False
self.currentCastlingRight.wqs = False
elif move.pieceMoved == "bK":
self.currentCastlingRight.bks = False
self.currentCastlingRight.bqs = False
elif move.pieceMoved == "wR":
if move.startRow == 7:
if move.startCol == 0: #left Rook
self.currentCastlingRight.wqs = False
if move.startCol == 7: #right rook
self.currentCastlingRight.wks = False
elif move.pieceMoved == "bR":
if move.startRow == 0:
if move.startCol == 0: #left Rook
self.currentCastlingRight.bqs = False
if move.startCol == 7: #right rook
self.currentCastlingRight.bks = False
#if a rook is captured
if move.pieceCaptured == 'wR':
if move.endRow == 7:
if move.endCol == 0:
self.currentCastlingRight.wqs = False
elif move.endCol == 7:
self.currentCastlingRight.wks = False
elif move.pieceCaptured == 'bR':
if move.endRow == 0:
if move.endCol == 0:
self.currentCastlingRight.bqs = False
elif move.endCol == 7:
self.currentCastlingRight.bks = False
# All moves considering checks
def getValidMoves(self):
tempCastleRights = CastleRights(self.currentCastlingRight.wks, self.currentCastlingRight.bks,
self.currentCastlingRight.wqs, self.currentCastlingRight.bqs) #copy the current castling rights
moves = []
self.inCheck, self.pins, self.checks = self.checkForPinsAndChecks()
if self.whiteToMove:
kingRow = self.whiteKingLocation[0]
kingCol = self.whiteKingLocation[1]
else:
kingRow = self.blackKingLocation[0]
kingCol = self.blackKingLocation[1]
if self.inCheck:
if len(self.checks) == 1: #only 1 check, block check or move king
moves = self.getAllPossibleMoves()
# to block a check you must move a piece into one of the squares between the enemy piec and king
check = self.checks[0]
checkRow = check[0]
checkCol = check[1]
pieceChecking = self.board[checkRow][checkCol]
validSquares = [] #square that pieces can move into
#if knight, must capture knight or move king, other pieces can be blocked
if pieceChecking[1] == "N":
validSquares = [(checkRow, checkCol)]
else:
for i in range(1, 8):
validSquare = (kingRow + check[2] * i, kingCol + check[3] * i) #check[2] and check[3] are the check directions
validSquares.append(validSquare)
if validSquare[0] == checkRow and validSquare[1] == checkCol: # once grts to piece end checks
break
# get rid of any moves that don't block check or move king
for i in range(len(moves)-1, -1, -1):
if moves[i].pieceMoved[1] != "K": #move doesn't move king so it must block or capture
if not (moves[i].endRow, moves[i].endCol) in validSquares: #move doesn't block or capture check piece
moves.remove(moves[i])
else: #double check, king has to move
moves = self.getKingMoves(kingRow, kingCol, moves)
else: #not in check so all moves are fine
moves = self.getAllPossibleMoves()
if moves == None or len(moves) == 0:
if self.inCheck:
self.checkmate = True
else:
self.stalemate = True
else:
self.checkmate = False
self.stalemate = False
self.getCastleMoves(kingRow, kingCol, moves)
self.currentCastlingRight = tempCastleRights
return moves
def checkForPinsAndChecks(self):
pins = [] #squares where the allied pinned piece is and direction pinned from
checks = [] #squares where enemy is applying a check
inCheck = False
if self.whiteToMove:
enemyColor = "b"
allyColor = "w"
startRow = self.whiteKingLocation[0]
startCol = self.whiteKingLocation[1]
else:
enemyColor = "w"
allyColor = "b"
startRow = self.blackKingLocation[0]
startCol = self.blackKingLocation[1]
#check outward from king for pins and checks, keep track of pins
directions = ((-1, 0), (0, -1), (1, 0), (0, 1), (-1, -1), (-1, 1), (1, -1), (1, 1))
for j in range(len(directions)):
d = directions[j]
possiblePin = () #reset possible pins
for i in range(1, 8):
endRow = startRow + d[0] * i
endCol = startCol + d[1] * i
if 0 <= endRow < 8 and 0 <= endCol <8 : #on board
endPiece = self.board[endRow][endCol]
if endPiece[0] == allyColor and endPiece[1] != 'K':
if possiblePin == (): #first allied piece could be pinned
possiblePin = (endRow, endCol, d[0], d[1])
else: #2nd allied piece, so no check possible in this direction
break
elif endPiece[0] == enemyColor:
type = endPiece[1]
# 5 possibilities here:
# 1) orthogonally away from king and piece is a rook
# 2) diagonally away from king and piece is a bishop
# 3) 1 square diagonaly away from the king and piece is a pawn
# 4) any direction and piece is a queen
# 5) any direction 1 square away and piece is a king
if (0 <= j <= 3 and type == "R") or \
(4 <= j <= 7 and type == "B") or \
(i == 1 and type == "P" and ((enemyColor == "w" and 6 <= j <= 7) or (enemyColor == "b" and 4 <= j <= 5))) or\
(type == "Q") or (i == 1 and type == "K"):
if possiblePin == (): # no piece blocking, so check
inCheck = True
checks.append((endRow, endCol, d[0], d[1]))
break
else: # piece blocking so pin
pins.append(possiblePin)
break
else: # enemy piece not applying check
break
else: #off board
break
#check for knight checks
knightMoves = ((-2, -1), (-2, 1), (-1, -2), (1, -2), (-1, 2), (1, 2), (2, -1), (2, 1))
for m in knightMoves:
endRow = startRow + m[0]
endCol = startCol + m[1]
if 0 <= endRow < 8 and 0 <= endCol < 8: # on board
endPiece = self.board[endRow][endCol]
if endPiece[0] == enemyColor and endPiece[1] == "N": #enemy knight attacking king
inCheck == True
checks.append((endRow, endCol, m[0], m[1]))
return inCheck, pins, checks
def squareUnderAttack(self, row, col):
'''
Determine if enemy can attack the square row col
'''
self.whiteToMove = not self.whiteToMove #switch to oponent's point of wiev
opponents_moves = np.array(self.getAllPossibleMoves())
self.whiteToMove = not self.whiteToMove
for move in opponents_moves:
if move.endRow == row and move.endCol == col: #square is under attack
return True
return False
# All moves without considering checks
def getAllPossibleMoves(self):
moves = []
for r in range(8):
for c in range(8):
turn = self.board[r][c][0]
if (turn == 'w' and self.whiteToMove) or (turn == 'b' and not self.whiteToMove):
piece = self.board[r][c][1]
self.moveFunct[piece](r, c, moves)
return moves
def getPawnMoves(self, r, c, moves):
piecePinned = False
pinDirection = ()
for i in range(len(self.pins)-1, -1, -1):
if self.pins[i][0] == r and self.pins[i][1] == c:
piecePinned = True
pinDirection = (self.pins[i][2], self.pins[i][3])
self.pins.remove(self.pins[i])
break
if self.whiteToMove: #White pawn moves
if r - 1 >= 0 and self.board[r-1][c] == "--": # 1 square pawn advance
if not piecePinned or pinDirection == (-1, 0):
moves.append(Move((r, c), (r-1, c), self.board))
if r == 6 and self.board[r-2][c] == "--":
moves.append(Move((r, c), (r-2, c), self.board)) # 2 square pawn advance
if r-1 >= 0 and c-1 >= 0: #capture to the left
if self.board[r-1][c-1][0] == "b":
if not piecePinned or pinDirection == (-1, -1):
moves.append(Move((r, c), (r-1, c-1), self.board))
if r-1 >= 0 and c+1 < 8: #capture to the right
if self.board[r-1][c+1][0] == "b":
if not piecePinned or pinDirection == (-1, 1):
moves.append(Move((r, c), (r-1, c+1), self.board))
else:
if r + 1 < 8 and self.board[r+1][c] == "--": # 1 square pawn advance
if not piecePinned or pinDirection == (1, 0):
moves.append(Move((r, c), (r+1, c), self.board))
if r == 1 and self.board[r+2][c] == "--":
moves.append(Move((r, c), (r+2, c), self.board)) # 2 square pawn advance
if r+1 < 8 and c-1 >= 0: #capture to the left
if self.board[r+1][c-1][0] == "w":
if not piecePinned or pinDirection == (1, -1):
moves.append(Move((r, c), (r+1, c-1), self.board))
if r+1 < 8 and c+1 < 8: #capture to the right
if self.board[r+1][c+1][0] == "w":
if not piecePinned or pinDirection == (1, 1):
moves.append(Move((r, c), (r+1, c+1), self.board))
def getRookMoves(self, r, c, moves):
piecePinned = False
pinDirection = ()
for i in range(len(self.pins)-1, -1, -1):
if self.pins[i][0] == r and self.pins[i][1] == c:
piecePinned = True
pinDirection = (self.pins[i][2], self.pins[i][3])
if self.board[r][c][1] != "Q":
self.pins.remove(self.pins[i])
break
directions = ((-1, 0), (0,-1), (1, 0), (0, 1)) #up, left, down, right
enemyColor = "b" if self.whiteToMove else "w"
for d in directions:
for i in range (1, 8):
endRow = r + d[0] * i
endCol = c + d[1] * i
if 0 <= endRow < 8 and 0 <= endCol < 8: # on board
if not piecePinned or pinDirection == d or pinDirection == (-d[0], -d[1]):
endPiece = self.board[endRow][endCol]
if endPiece == "--": #empty space valid
moves.append(Move((r, c),(endRow, endCol), self.board))
elif endPiece[0] == enemyColor: # enemy piece valid
moves.append(Move((r, c),(endRow, endCol), self.board))
break
else: # friendly piece invalid
break
else: # off the board
break
def getKnightMoves(self, r, c, moves):
piecePinned = False
pinDirection = ()
for i in range(len(self.pins)-1, -1, -1):
if self.pins[i][0] == r and self.pins[i][1] == c:
piecePinned = True
pinDirection = (self.pins[i][2], self.pins[i][3])
self.pins.remove(self.pins[i])
break
knightMoves = ((-2, -1), (-2, 1), (-1, -2), (1, -2), (-1, 2), (1, 2), (2, -1), (2, 1))
allyColor = "w" if self.whiteToMove else "b"
for m in knightMoves:
endRow = r + m[0]
endCol = c + m[1]
if 0 <= endRow < 8 and 0 <= endCol < 8: # on board
if not piecePinned:
endPiece = self.board[endRow][endCol]
if endPiece[0] != allyColor: # not an ally piece (empty or enemy piece)
moves.append(Move((r, c),(endRow, endCol), self.board))
def getBishopMoves(self, r, c, moves):
piecePinned = False
pinDirection = ()
for i in range(len(self.pins)-1, -1, -1):
if self.pins[i][0] == r and self.pins[i][1] == c:
piecePinned = True
pinDirection = (self.pins[i][2], self.pins[i][3])
self.pins.remove(self.pins[i])
break
directions = ((-1, -1), (-1, 1), (1, -1), (1, 1))
enemyColor = "b" if self.whiteToMove else "w"
for d in directions:
for i in range (1, 8): #bishop can move max of 7 squares
endRow = r + d[0] * i
endCol = c + d[1] * i
if 0 <= endRow < 8 and 0 <= endCol < 8: # on board
if not piecePinned or pinDirection == d or pinDirection == (-d[0], -d[1]):
endPiece = self.board[endRow][endCol]
if endPiece == "--": #empty space valid
moves.append(Move((r, c),(endRow, endCol), self.board))
elif endPiece[0] == enemyColor: # enemy piece valid
moves.append(Move((r, c),(endRow, endCol), self.board))
break
else: # friendly piece invalid
break
else: # off the board
break
def getQueenMoves(self, r, c, moves):
self.getRookMoves(r, c, moves)
self.getBishopMoves(r, c, moves)
def getKingMoves(self, r, c, moves):
rowMoves = (-1, -1, -1, 0, 0, 1, 1, 1)
colMoves = (-1, 0, 1, -1, 1, -1, 0, 1)
allyColor = "w" if self.whiteToMove else "b"
for i in range(8):
endRow = r + rowMoves[i]
endCol = c + colMoves[i]
if 0 <= endRow < 8 and 0 <= endCol < 8: # on board
endPiece = self.board[endRow][endCol]
if endPiece[0] != allyColor: # not an ally piece (empty or enemy piece)
#place king on end square and check for checks
if allyColor == "w":
self.whiteKingLocation = (endRow, endCol)
else:
self.blackKingLocation = (endRow, endCol)
inCheck, pins, checks = self.checkForPinsAndChecks()
if not inCheck:
moves.append(Move((r, c),(endRow, endCol), self.board))
#place king back on original location
if allyColor == "w":
self.whiteKingLocation = (r, c)
else:
self.blackKingLocation = (r, c)
def getCastleMoves(self, r, c, moves):
if self.squareUnderAttack(r, c):
return #can't castle while we're in check
if (self.whiteToMove and self.currentCastlingRight.wks) or (not self.whiteToMove and self.currentCastlingRight.bks):
self.getKingsideCastleMoves(r, c, moves)
if (self.whiteToMove and self.currentCastlingRight.wqs) or (not self.whiteToMove and self.currentCastlingRight.bqs):
self.getQueensideCastleMoves(r, c, moves)
def getKingsideCastleMoves(self, r, c, moves):
if self.board[r][c+1] == "--" and self.board[r][c+2] == "--":
if not self.squareUnderAttack(r, c+1) and not self.squareUnderAttack(r, c+2):
moves.append(Move((r, c), (r, c+2), self.board, isCastleMove=True))
def getQueensideCastleMoves(self, r, c, moves):
if self.board[r][c-1] == "--" and self.board[r][c-2] == "--" and self.board[r][c-3] == "--":
if not self.squareUnderAttack(r, c-1) and not self.squareUnderAttack(r, c-2):
moves.append(Move((r, c), (r, c-2), self.board, isCastleMove=True))
class CastleRights():
def __init__(self, wks, bks, wqs, bqs):
self.wks = wks
self.bks = bks
self.wqs = wqs
self.bqs = bqs
class Move():
#maping keys to values:
ranksToRows = {"1": 7, "2": 6, "3": 5, "4": 4,
"5": 3, "6": 2, "7": 1, "8": 0}
rowsToRanks = {v:k for k, v in ranksToRows.items()}
filesToCols = {"a": 0, "b": 1, "c": 2, "d": 3,
"e": 4, "f": 5, "g": 6, "h": 7}
colsToFiles = {v:k for k, v in filesToCols.items()}
def __init__(self, startSq, endSq, board, isCastleMove = False):
self.startRow = startSq[0]
self.startCol = startSq[1]
self.endRow = endSq[0]
self.endCol = endSq[1]
self.pieceMoved = board[self.startRow][self.startCol]
self.pieceCaptured = board[self.endRow][self.endCol]
#pawn promotion:
self.isPawnPromotion = (self.pieceMoved == "wP" and self.endRow == 0) or (self.pieceMoved == "bP" and self.endRow == 7)
#castle move:
self.isCastleMove = isCastleMove
def getChessNotation(self):
return self.colsToFiles[self.startCol] + self.rowsToRanks[self.startRow] +self.colsToFiles[self.endCol] + self.rowsToRanks[self.endRow]
#overriding the equals method
def __eq__(self, other):
if isinstance(other, Move):
return self.getChessNotation() == other.getChessNotation()
else:
return False