1 // (Orthodox) Chess rules are defined in ChessRules class.
2 // Variants generally inherit from it, and modify some parts.
4 class PiPo
//Piece+Position
6 // o: {piece[p], color[c], posX[x], posY[y]}
16 // TODO: for animation, moves should contains "moving" and "fading" maybe...
19 // o: {appear, vanish, [start,] [end,]}
20 // appear,vanish = arrays of PiPo
21 // start,end = coordinates to apply to trigger move visually (think castle)
24 this.appear
= o
.appear
;
25 this.vanish
= o
.vanish
;
26 this.start
= !!o
.start
? o
.start : {x:o
.vanish
[0].x
, y:o
.vanish
[0].y
};
27 this.end
= !!o
.end
? o
.end : {x:o
.appear
[0].x
, y:o
.appear
[0].y
};
31 // NOTE: x coords = top to bottom; y = left to right (from white player perspective)
37 static get HasFlags() { return true; } //some variants don't have flags
39 static get HasEnpassant() { return true; } //some variants don't have ep.
44 return b
; //usual pieces in pieces/ folder
47 // Turn "wb" into "B" (for FEN)
50 return b
[0]=='w' ? b
[1].toUpperCase() : b
[1];
53 // Turn "p" into "bp" (for board)
56 return f
.charCodeAt()<=90 ? "w"+f
.toLowerCase() : "b"+f
;
59 // Check if FEN describe a position
62 const fenParsed
= V
.ParseFen(fen
);
64 if (!V
.IsGoodPosition(fenParsed
.position
))
67 if (!fenParsed
.turn
|| !V
.IsGoodTurn(fenParsed
.turn
))
70 if (V
.HasFlags
&& (!fenParsed
.flags
|| !V
.IsGoodFlags(fenParsed
.flags
)))
74 (!fenParsed
.enpassant
|| !V
.IsGoodEnpassant(fenParsed
.enpassant
)))
81 // Is position part of the FEN a priori correct?
82 static IsGoodPosition(position
)
84 if (position
.length
== 0)
86 const rows
= position
.split("/");
87 if (rows
.length
!= V
.size
.x
)
92 for (let i
=0; i
<row
.length
; i
++)
94 if (V
.PIECES
.includes(row
[i
].toLowerCase()))
98 const num
= parseInt(row
[i
]);
104 if (sumElts
!= V
.size
.y
)
111 static IsGoodTurn(turn
)
113 return ["w","b"].includes(turn
);
117 static IsGoodFlags(flags
)
119 return !!flags
.match(/^[01]{4,4}$/);
122 static IsGoodEnpassant(enpassant
)
124 if (enpassant
!= "-")
126 const ep
= V
.SquareToCoords(fenParsed
.enpassant
);
127 if (isNaN(ep
.x
) || !V
.OnBoard(ep
))
133 // 3 --> d (column number to letter)
134 static CoordToColumn(colnum
)
136 return String
.fromCharCode(97 + colnum
);
139 // d --> 3 (column letter to number)
140 static ColumnToCoord(column
)
142 return column
.charCodeAt(0) - 97;
146 static SquareToCoords(sq
)
149 // NOTE: column is always one char => max 26 columns
150 // row is counted from black side => subtraction
151 x: V
.size
.x
- parseInt(sq
.substr(1)),
152 y: sq
[0].charCodeAt() - 97
157 static CoordsToSquare(coords
)
159 return V
.CoordToColumn(coords
.y
) + (V
.size
.x
- coords
.x
);
162 // Aggregates flags into one object
165 return this.castleFlags
;
169 disaggregateFlags(flags
)
171 this.castleFlags
= flags
;
174 // En-passant square, if any
175 getEpSquare(moveOrSquare
)
179 if (typeof moveOrSquare
=== "string")
181 const square
= moveOrSquare
;
184 return V
.SquareToCoords(square
);
186 // Argument is a move:
187 const move = moveOrSquare
;
188 const [sx
,sy
,ex
] = [move.start
.x
,move.start
.y
,move.end
.x
];
189 if (this.getPiece(sx
,sy
) == V
.PAWN
&& Math
.abs(sx
- ex
) == 2)
196 return undefined; //default
199 // Can thing on square1 take thing on square2
200 canTake([x1
,y1
], [x2
,y2
])
202 return this.getColor(x1
,y1
) !== this.getColor(x2
,y2
);
205 // Is (x,y) on the chessboard?
208 return (x
>=0 && x
<V
.size
.x
&& y
>=0 && y
<V
.size
.y
);
211 // Used in interface: 'side' arg == player color
212 canIplay(side
, [x
,y
])
214 return (this.turn
== side
&& this.getColor(x
,y
) == side
);
217 // On which squares is color under check ? (for interface)
218 getCheckSquares(color
)
220 return this.isAttacked(this.kingPos
[color
], [this.getOppCol(color
)])
221 ? [JSON
.parse(JSON
.stringify(this.kingPos
[color
]))] //need to duplicate!
228 // Setup the initial random (assymetric) position
229 static GenRandInitFen()
231 let pieces
= { "w": new Array(8), "b": new Array(8) };
232 // Shuffle pieces on first and last rank
233 for (let c
of ["w","b"])
235 let positions
= _
.range(8);
237 // Get random squares for bishops
238 let randIndex
= 2 * _
.random(3);
239 const bishop1Pos
= positions
[randIndex
];
240 // The second bishop must be on a square of different color
241 let randIndex_tmp
= 2 * _
.random(3) + 1;
242 const bishop2Pos
= positions
[randIndex_tmp
];
243 // Remove chosen squares
244 positions
.splice(Math
.max(randIndex
,randIndex_tmp
), 1);
245 positions
.splice(Math
.min(randIndex
,randIndex_tmp
), 1);
247 // Get random squares for knights
248 randIndex
= _
.random(5);
249 const knight1Pos
= positions
[randIndex
];
250 positions
.splice(randIndex
, 1);
251 randIndex
= _
.random(4);
252 const knight2Pos
= positions
[randIndex
];
253 positions
.splice(randIndex
, 1);
255 // Get random square for queen
256 randIndex
= _
.random(3);
257 const queenPos
= positions
[randIndex
];
258 positions
.splice(randIndex
, 1);
260 // Rooks and king positions are now fixed,
261 // because of the ordering rook-king-rook
262 const rook1Pos
= positions
[0];
263 const kingPos
= positions
[1];
264 const rook2Pos
= positions
[2];
266 // Finally put the shuffled pieces in the board array
267 pieces
[c
][rook1Pos
] = 'r';
268 pieces
[c
][knight1Pos
] = 'n';
269 pieces
[c
][bishop1Pos
] = 'b';
270 pieces
[c
][queenPos
] = 'q';
271 pieces
[c
][kingPos
] = 'k';
272 pieces
[c
][bishop2Pos
] = 'b';
273 pieces
[c
][knight2Pos
] = 'n';
274 pieces
[c
][rook2Pos
] = 'r';
276 return pieces
["b"].join("") +
277 "/pppppppp/8/8/8/8/PPPPPPPP/" +
278 pieces
["w"].join("").toUpperCase() +
279 " w 1111 -"; //add turn + flags + enpassant
282 // "Parse" FEN: just return untransformed string data
285 const fenParts
= fen
.split(" ");
288 position: fenParts
[0],
293 Object
.assign(res
, {flags: fenParts
[nextIdx
++]});
295 Object
.assign(res
, {enpassant: fenParts
[nextIdx
]});
299 // Return current fen (game state)
302 return this.getBaseFen() + " " + this.getTurnFen() +
303 (V
.HasFlags
? (" " + this.getFlagsFen()) : "") +
304 (V
.HasEnpassant
? (" " + this.getEnpassantFen()) : "");
307 // Position part of the FEN string
311 for (let i
=0; i
<V
.size
.x
; i
++)
314 for (let j
=0; j
<V
.size
.y
; j
++)
316 if (this.board
[i
][j
] == V
.EMPTY
)
322 // Add empty squares in-between
323 position
+= emptyCount
;
326 position
+= V
.board2fen(this.board
[i
][j
]);
332 position
+= emptyCount
;
334 if (i
< V
.size
.x
- 1)
335 position
+= "/"; //separate rows
345 // Flags part of the FEN string
349 // Add castling flags
350 for (let i
of ['w','b'])
352 for (let j
=0; j
<2; j
++)
353 flags
+= (this.castleFlags
[i
][j
] ? '1' : '0');
358 // Enpassant part of the FEN string
361 const L
= this.epSquares
.length
;
362 if (!this.epSquares
[L
-1])
363 return "-"; //no en-passant
364 return V
.CoordsToSquare(this.epSquares
[L
-1]);
367 // Turn position fen into double array ["wb","wp","bk",...]
368 static GetBoard(position
)
370 const rows
= position
.split("/");
371 let board
= doubleArray(V
.size
.x
, V
.size
.y
, "");
372 for (let i
=0; i
<rows
.length
; i
++)
375 for (let indexInRow
= 0; indexInRow
< rows
[i
].length
; indexInRow
++)
377 const character
= rows
[i
][indexInRow
];
378 const num
= parseInt(character
);
380 j
+= num
; //just shift j
381 else //something at position i,j
382 board
[i
][j
++] = V
.fen2board(character
);
388 // Extract (relevant) flags from fen
391 // white a-castle, h-castle, black a-castle, h-castle
392 this.castleFlags
= {'w': [true,true], 'b': [true,true]};
395 for (let i
=0; i
<4; i
++)
396 this.castleFlags
[i
< 2 ? 'w' : 'b'][i
%2] = (fenflags
.charAt(i
) == '1');
402 // Fen string fully describes the game state
403 constructor(fen
, moves
)
406 const fenParsed
= V
.ParseFen(fen
);
407 this.board
= V
.GetBoard(fenParsed
.position
);
408 this.turn
= fenParsed
.turn
[0]; //[0] to work with MarseilleRules
409 this.setOtherVariables(fen
);
412 // Scan board for kings and rooks positions
415 this.INIT_COL_KING
= {'w':-1, 'b':-1};
416 this.INIT_COL_ROOK
= {'w':[-1,-1], 'b':[-1,-1]};
417 this.kingPos
= {'w':[-1,-1], 'b':[-1,-1]}; //squares of white and black king
418 const fenRows
= V
.ParseFen(fen
).position
.split("/");
419 for (let i
=0; i
<fenRows
.length
; i
++)
421 let k
= 0; //column index on board
422 for (let j
=0; j
<fenRows
[i
].length
; j
++)
424 switch (fenRows
[i
].charAt(j
))
427 this.kingPos
['b'] = [i
,k
];
428 this.INIT_COL_KING
['b'] = k
;
431 this.kingPos
['w'] = [i
,k
];
432 this.INIT_COL_KING
['w'] = k
;
435 if (this.INIT_COL_ROOK
['b'][0] < 0)
436 this.INIT_COL_ROOK
['b'][0] = k
;
438 this.INIT_COL_ROOK
['b'][1] = k
;
441 if (this.INIT_COL_ROOK
['w'][0] < 0)
442 this.INIT_COL_ROOK
['w'][0] = k
;
444 this.INIT_COL_ROOK
['w'][1] = k
;
447 const num
= parseInt(fenRows
[i
].charAt(j
));
456 // Some additional variables from FEN (variant dependant)
457 setOtherVariables(fen
)
459 // Set flags and enpassant:
460 const parsedFen
= V
.ParseFen(fen
);
462 this.setFlags(parsedFen
.flags
);
465 const epSq
= parsedFen
.enpassant
!= "-"
466 ? V
.SquareToCoords(parsedFen
.enpassant
)
468 this.epSquares
= [ epSq
];
470 // Search for king and rooks positions:
471 this.scanKingsRooks(fen
);
474 /////////////////////
482 // Color of thing on suqare (i,j). 'undefined' if square is empty
485 return this.board
[i
][j
].charAt(0);
488 // Piece type on square (i,j). 'undefined' if square is empty
491 return this.board
[i
][j
].charAt(1);
494 // Get opponent color
497 return (color
=="w" ? "b" : "w");
502 const L
= this.moves
.length
;
503 return (L
>0 ? this.moves
[L
-1] : null);
506 // Pieces codes (for a clearer code)
507 static get PAWN() { return 'p'; }
508 static get ROOK() { return 'r'; }
509 static get KNIGHT() { return 'n'; }
510 static get BISHOP() { return 'b'; }
511 static get QUEEN() { return 'q'; }
512 static get KING() { return 'k'; }
517 return [V
.PAWN
,V
.ROOK
,V
.KNIGHT
,V
.BISHOP
,V
.QUEEN
,V
.KING
];
521 static get EMPTY() { return ""; }
523 // Some pieces movements
527 'r': [ [-1,0],[1,0],[0,-1],[0,1] ],
528 'n': [ [-1,-2],[-1,2],[1,-2],[1,2],[-2,-1],[-2,1],[2,-1],[2,1] ],
529 'b': [ [-1,-1],[-1,1],[1,-1],[1,1] ],
536 // All possible moves from selected square (assumption: color is OK)
537 getPotentialMovesFrom([x
,y
])
539 switch (this.getPiece(x
,y
))
542 return this.getPotentialPawnMoves([x
,y
]);
544 return this.getPotentialRookMoves([x
,y
]);
546 return this.getPotentialKnightMoves([x
,y
]);
548 return this.getPotentialBishopMoves([x
,y
]);
550 return this.getPotentialQueenMoves([x
,y
]);
552 return this.getPotentialKingMoves([x
,y
]);
556 // Build a regular move from its initial and destination squares.
557 // tr: transformation
558 getBasicMove([sx
,sy
], [ex
,ey
], tr
)
565 c: !!tr
? tr
.c : this.getColor(sx
,sy
),
566 p: !!tr
? tr
.p : this.getPiece(sx
,sy
)
573 c: this.getColor(sx
,sy
),
574 p: this.getPiece(sx
,sy
)
579 // The opponent piece disappears if we take it
580 if (this.board
[ex
][ey
] != V
.EMPTY
)
586 c: this.getColor(ex
,ey
),
587 p: this.getPiece(ex
,ey
)
594 // Generic method to find possible moves of non-pawn pieces:
595 // "sliding or jumping"
596 getSlideNJumpMoves([x
,y
], steps
, oneStep
)
598 const color
= this.getColor(x
,y
);
601 for (let step
of steps
)
605 while (V
.OnBoard(i
,j
) && this.board
[i
][j
] == V
.EMPTY
)
607 moves
.push(this.getBasicMove([x
,y
], [i
,j
]));
608 if (oneStep
!== undefined)
613 if (V
.OnBoard(i
,j
) && this.canTake([x
,y
], [i
,j
]))
614 moves
.push(this.getBasicMove([x
,y
], [i
,j
]));
619 // What are the pawn moves from square x,y ?
620 getPotentialPawnMoves([x
,y
])
622 const color
= this.turn
;
624 const [sizeX
,sizeY
] = [V
.size
.x
,V
.size
.y
];
625 const shiftX
= (color
== "w" ? -1 : 1);
626 const firstRank
= (color
== 'w' ? sizeX
-1 : 0);
627 const startRank
= (color
== "w" ? sizeX
-2 : 1);
628 const lastRank
= (color
== "w" ? 0 : sizeX
-1);
629 const pawnColor
= this.getColor(x
,y
); //can be different for checkered
631 if (x
+shiftX
>= 0 && x
+shiftX
< sizeX
) //TODO: always true
633 const finalPieces
= x
+ shiftX
== lastRank
634 ? [V
.ROOK
,V
.KNIGHT
,V
.BISHOP
,V
.QUEEN
]
636 // One square forward
637 if (this.board
[x
+shiftX
][y
] == V
.EMPTY
)
639 for (let piece
of finalPieces
)
641 moves
.push(this.getBasicMove([x
,y
], [x
+shiftX
,y
],
642 {c:pawnColor
,p:piece
}));
644 // Next condition because pawns on 1st rank can generally jump
645 if ([startRank
,firstRank
].includes(x
)
646 && this.board
[x
+2*shiftX
][y
] == V
.EMPTY
)
649 moves
.push(this.getBasicMove([x
,y
], [x
+2*shiftX
,y
]));
653 for (let shiftY
of [-1,1])
655 if (y
+ shiftY
>= 0 && y
+ shiftY
< sizeY
656 && this.board
[x
+shiftX
][y
+shiftY
] != V
.EMPTY
657 && this.canTake([x
,y
], [x
+shiftX
,y
+shiftY
]))
659 for (let piece
of finalPieces
)
661 moves
.push(this.getBasicMove([x
,y
], [x
+shiftX
,y
+shiftY
],
662 {c:pawnColor
,p:piece
}));
671 const Lep
= this.epSquares
.length
;
672 const epSquare
= this.epSquares
[Lep
-1]; //always at least one element
673 if (!!epSquare
&& epSquare
.x
== x
+shiftX
&& Math
.abs(epSquare
.y
- y
) == 1)
675 let enpassantMove
= this.getBasicMove([x
,y
], [epSquare
.x
,epSquare
.y
]);
676 enpassantMove
.vanish
.push({
680 c: this.getColor(x
,epSquare
.y
)
682 moves
.push(enpassantMove
);
689 // What are the rook moves from square x,y ?
690 getPotentialRookMoves(sq
)
692 return this.getSlideNJumpMoves(sq
, V
.steps
[V
.ROOK
]);
695 // What are the knight moves from square x,y ?
696 getPotentialKnightMoves(sq
)
698 return this.getSlideNJumpMoves(sq
, V
.steps
[V
.KNIGHT
], "oneStep");
701 // What are the bishop moves from square x,y ?
702 getPotentialBishopMoves(sq
)
704 return this.getSlideNJumpMoves(sq
, V
.steps
[V
.BISHOP
]);
707 // What are the queen moves from square x,y ?
708 getPotentialQueenMoves(sq
)
710 return this.getSlideNJumpMoves(sq
,
711 V
.steps
[V
.ROOK
].concat(V
.steps
[V
.BISHOP
]));
714 // What are the king moves from square x,y ?
715 getPotentialKingMoves(sq
)
717 // Initialize with normal moves
718 let moves
= this.getSlideNJumpMoves(sq
,
719 V
.steps
[V
.ROOK
].concat(V
.steps
[V
.BISHOP
]), "oneStep");
720 return moves
.concat(this.getCastleMoves(sq
));
723 getCastleMoves([x
,y
])
725 const c
= this.getColor(x
,y
);
726 if (x
!= (c
=="w" ? V
.size
.x
-1 : 0) || y
!= this.INIT_COL_KING
[c
])
727 return []; //x isn't first rank, or king has moved (shortcut)
730 const oppCol
= this.getOppCol(c
);
733 const finalSquares
= [ [2,3], [V
.size
.y
-2,V
.size
.y
-3] ]; //king, then rook
735 for (let castleSide
=0; castleSide
< 2; castleSide
++) //large, then small
737 if (!this.castleFlags
[c
][castleSide
])
739 // If this code is reached, rooks and king are on initial position
741 // Nothing on the path of the king ?
742 // (And no checks; OK also if y==finalSquare)
743 let step
= finalSquares
[castleSide
][0] < y
? -1 : 1;
744 for (i
=y
; i
!=finalSquares
[castleSide
][0]; i
+=step
)
746 if (this.isAttacked([x
,i
], [oppCol
]) || (this.board
[x
][i
] != V
.EMPTY
&&
747 // NOTE: next check is enough, because of chessboard constraints
748 (this.getColor(x
,i
) != c
749 || ![V
.KING
,V
.ROOK
].includes(this.getPiece(x
,i
)))))
751 continue castlingCheck
;
755 // Nothing on the path to the rook?
756 step
= castleSide
== 0 ? -1 : 1;
757 for (i
= y
+ step
; i
!= this.INIT_COL_ROOK
[c
][castleSide
]; i
+= step
)
759 if (this.board
[x
][i
] != V
.EMPTY
)
760 continue castlingCheck
;
762 const rookPos
= this.INIT_COL_ROOK
[c
][castleSide
];
764 // Nothing on final squares, except maybe king and castling rook?
767 if (this.board
[x
][finalSquares
[castleSide
][i
]] != V
.EMPTY
&&
768 this.getPiece(x
,finalSquares
[castleSide
][i
]) != V
.KING
&&
769 finalSquares
[castleSide
][i
] != rookPos
)
771 continue castlingCheck
;
775 // If this code is reached, castle is valid
776 moves
.push( new Move({
778 new PiPo({x:x
,y:finalSquares
[castleSide
][0],p:V
.KING
,c:c
}),
779 new PiPo({x:x
,y:finalSquares
[castleSide
][1],p:V
.ROOK
,c:c
})],
781 new PiPo({x:x
,y:y
,p:V
.KING
,c:c
}),
782 new PiPo({x:x
,y:rookPos
,p:V
.ROOK
,c:c
})],
783 end: Math
.abs(y
- rookPos
) <= 2
785 : {x:x
, y:y
+ 2 * (castleSide
==0 ? -1 : 1)}
795 // For the interface: possible moves for the current turn from square sq
796 getPossibleMovesFrom(sq
)
798 return this.filterValid( this.getPotentialMovesFrom(sq
) );
801 // TODO: promotions (into R,B,N,Q) should be filtered only once
804 if (moves
.length
== 0)
806 const color
= this.turn
;
807 return moves
.filter(m
=> {
809 const res
= !this.underCheck(color
);
815 // Search for all valid moves considering current turn
816 // (for engine and game end)
819 const color
= this.turn
;
820 const oppCol
= this.getOppCol(color
);
821 let potentialMoves
= [];
822 for (let i
=0; i
<V
.size
.x
; i
++)
824 for (let j
=0; j
<V
.size
.y
; j
++)
826 // Next condition "!= oppCol" to work with checkered variant
827 if (this.board
[i
][j
] != V
.EMPTY
&& this.getColor(i
,j
) != oppCol
)
829 Array
.prototype.push
.apply(potentialMoves
,
830 this.getPotentialMovesFrom([i
,j
]));
834 return this.filterValid(potentialMoves
);
837 // Stop at the first move found
840 const color
= this.turn
;
841 const oppCol
= this.getOppCol(color
);
842 for (let i
=0; i
<V
.size
.x
; i
++)
844 for (let j
=0; j
<V
.size
.y
; j
++)
846 if (this.board
[i
][j
] != V
.EMPTY
&& this.getColor(i
,j
) != oppCol
)
848 const moves
= this.getPotentialMovesFrom([i
,j
]);
849 if (moves
.length
> 0)
851 for (let k
=0; k
<moves
.length
; k
++)
853 if (this.filterValid([moves
[k
]]).length
> 0)
863 // Check if pieces of color in 'colors' are attacking (king) on square x,y
864 isAttacked(sq
, colors
)
866 return (this.isAttackedByPawn(sq
, colors
)
867 || this.isAttackedByRook(sq
, colors
)
868 || this.isAttackedByKnight(sq
, colors
)
869 || this.isAttackedByBishop(sq
, colors
)
870 || this.isAttackedByQueen(sq
, colors
)
871 || this.isAttackedByKing(sq
, colors
));
874 // Is square x,y attacked by 'colors' pawns ?
875 isAttackedByPawn([x
,y
], colors
)
877 for (let c
of colors
)
879 let pawnShift
= (c
=="w" ? 1 : -1);
880 if (x
+pawnShift
>=0 && x
+pawnShift
<V
.size
.x
)
882 for (let i
of [-1,1])
884 if (y
+i
>=0 && y
+i
<V
.size
.y
&& this.getPiece(x
+pawnShift
,y
+i
)==V
.PAWN
885 && this.getColor(x
+pawnShift
,y
+i
)==c
)
895 // Is square x,y attacked by 'colors' rooks ?
896 isAttackedByRook(sq
, colors
)
898 return this.isAttackedBySlideNJump(sq
, colors
, V
.ROOK
, V
.steps
[V
.ROOK
]);
901 // Is square x,y attacked by 'colors' knights ?
902 isAttackedByKnight(sq
, colors
)
904 return this.isAttackedBySlideNJump(sq
, colors
,
905 V
.KNIGHT
, V
.steps
[V
.KNIGHT
], "oneStep");
908 // Is square x,y attacked by 'colors' bishops ?
909 isAttackedByBishop(sq
, colors
)
911 return this.isAttackedBySlideNJump(sq
, colors
, V
.BISHOP
, V
.steps
[V
.BISHOP
]);
914 // Is square x,y attacked by 'colors' queens ?
915 isAttackedByQueen(sq
, colors
)
917 return this.isAttackedBySlideNJump(sq
, colors
, V
.QUEEN
,
918 V
.steps
[V
.ROOK
].concat(V
.steps
[V
.BISHOP
]));
921 // Is square x,y attacked by 'colors' king(s) ?
922 isAttackedByKing(sq
, colors
)
924 return this.isAttackedBySlideNJump(sq
, colors
, V
.KING
,
925 V
.steps
[V
.ROOK
].concat(V
.steps
[V
.BISHOP
]), "oneStep");
928 // Generic method for non-pawn pieces ("sliding or jumping"):
929 // is x,y attacked by a piece of color in array 'colors' ?
930 isAttackedBySlideNJump([x
,y
], colors
, piece
, steps
, oneStep
)
932 for (let step
of steps
)
934 let rx
= x
+step
[0], ry
= y
+step
[1];
935 while (V
.OnBoard(rx
,ry
) && this.board
[rx
][ry
] == V
.EMPTY
&& !oneStep
)
940 if (V
.OnBoard(rx
,ry
) && this.getPiece(rx
,ry
) === piece
941 && colors
.includes(this.getColor(rx
,ry
)))
949 // Is color under check after his move ?
952 return this.isAttacked(this.kingPos
[color
], [this.getOppCol(color
)]);
958 // Apply a move on board
959 static PlayOnBoard(board
, move)
961 for (let psq
of move.vanish
)
962 board
[psq
.x
][psq
.y
] = V
.EMPTY
;
963 for (let psq
of move.appear
)
964 board
[psq
.x
][psq
.y
] = psq
.c
+ psq
.p
;
966 // Un-apply the played move
967 static UndoOnBoard(board
, move)
969 for (let psq
of move.appear
)
970 board
[psq
.x
][psq
.y
] = V
.EMPTY
;
971 for (let psq
of move.vanish
)
972 board
[psq
.x
][psq
.y
] = psq
.c
+ psq
.p
;
975 // After move is played, update variables + flags
976 updateVariables(move)
978 let piece
= undefined;
980 if (move.vanish
.length
>= 1)
982 // Usual case, something is moved
983 piece
= move.vanish
[0].p
;
984 c
= move.vanish
[0].c
;
988 // Crazyhouse-like variants
989 piece
= move.appear
[0].p
;
990 c
= move.appear
[0].c
;
992 if (c
== "c") //if (!["w","b"].includes(c))
994 // 'c = move.vanish[0].c' doesn't work for Checkered
995 c
= this.getOppCol(this.turn
);
997 const firstRank
= (c
== "w" ? V
.size
.x
-1 : 0);
999 // Update king position + flags
1000 if (piece
== V
.KING
&& move.appear
.length
> 0)
1002 this.kingPos
[c
][0] = move.appear
[0].x
;
1003 this.kingPos
[c
][1] = move.appear
[0].y
;
1004 this.castleFlags
[c
] = [false,false];
1007 const oppCol
= this.getOppCol(c
);
1008 const oppFirstRank
= (V
.size
.x
-1) - firstRank
;
1009 if (move.start
.x
== firstRank
//our rook moves?
1010 && this.INIT_COL_ROOK
[c
].includes(move.start
.y
))
1012 const flagIdx
= (move.start
.y
== this.INIT_COL_ROOK
[c
][0] ? 0 : 1);
1013 this.castleFlags
[c
][flagIdx
] = false;
1015 else if (move.end
.x
== oppFirstRank
//we took opponent rook?
1016 && this.INIT_COL_ROOK
[oppCol
].includes(move.end
.y
))
1018 const flagIdx
= (move.end
.y
== this.INIT_COL_ROOK
[oppCol
][0] ? 0 : 1);
1019 this.castleFlags
[oppCol
][flagIdx
] = false;
1023 // After move is undo-ed *and flags resetted*, un-update other variables
1024 // TODO: more symmetry, by storing flags increment in move (?!)
1025 unupdateVariables(move)
1027 // (Potentially) Reset king position
1028 const c
= this.getColor(move.start
.x
,move.start
.y
);
1029 if (this.getPiece(move.start
.x
,move.start
.y
) == V
.KING
)
1030 this.kingPos
[c
] = [move.start
.x
, move.start
.y
];
1036 // if (!this.states) this.states = [];
1037 // if (!ingame) this.states.push(this.getFen());
1040 move.notation
= [this.getNotation(move), this.getLongNotation(move)];
1043 move.flags
= JSON
.stringify(this.aggregateFlags()); //save flags (for undo)
1045 this.epSquares
.push( this.getEpSquare(move) );
1046 V
.PlayOnBoard(this.board
, move);
1047 this.turn
= this.getOppCol(this.turn
);
1048 this.moves
.push(move);
1049 this.updateVariables(move);
1053 // Hash of current game state *after move*, to detect repetitions
1054 move.hash
= hex_md5(this.getFen());
1061 this.epSquares
.pop();
1063 this.disaggregateFlags(JSON
.parse(move.flags
));
1064 V
.UndoOnBoard(this.board
, move);
1065 this.turn
= this.getOppCol(this.turn
);
1067 this.unupdateVariables(move);
1070 // if (this.getFen() != this.states[this.states.length-1])
1072 // this.states.pop();
1078 // Check for 3 repetitions (position + flags + turn)
1081 if (!this.hashStates
)
1082 this.hashStates
= {};
1084 Object
.values(this.hashStates
).reduce((a
,b
) => { return a
+b
; }, 0)
1085 // Update this.hashStates with last move (or all moves if continuation)
1086 // NOTE: redundant storage, but faster and moderate size
1087 for (let i
=startIndex
; i
<this.moves
.length
; i
++)
1089 const move = this.moves
[i
];
1090 if (!this.hashStates
[move.hash
])
1091 this.hashStates
[move.hash
] = 1;
1093 this.hashStates
[move.hash
]++;
1095 return Object
.values(this.hashStates
).some(elt
=> { return (elt
>= 3); });
1098 // Is game over ? And if yes, what is the score ?
1101 if (this.checkRepetition())
1104 if (this.atLeastOneMove()) // game not over
1108 return this.checkGameEnd();
1111 // No moves are possible: compute score
1114 const color
= this.turn
;
1115 // No valid move: stalemate or checkmate?
1116 if (!this.isAttacked(this.kingPos
[color
], [this.getOppCol(color
)]))
1119 return (color
== "w" ? "0-1" : "1-0");
1138 // "Checkmate" (unreachable eval)
1139 static get INFINITY() { return 9999; }
1141 // At this value or above, the game is over
1142 static get THRESHOLD_MATE() { return V
.INFINITY
; }
1144 // Search depth: 2 for high branching factor, 4 for small (Loser chess, eg.)
1145 static get SEARCH_DEPTH() { return 3; }
1147 // Assumption: at least one legal move
1148 // NOTE: works also for extinction chess because depth is 3...
1151 const maxeval
= V
.INFINITY
;
1152 const color
= this.turn
;
1153 // Some variants may show a bigger moves list to the human (Switching),
1154 // thus the argument "computer" below (which is generally ignored)
1155 let moves1
= this.getAllValidMoves("computer");
1157 // Can I mate in 1 ? (for Magnetic & Extinction)
1158 for (let i
of _
.shuffle(_
.range(moves1
.length
)))
1160 this.play(moves1
[i
]);
1161 let finish
= (Math
.abs(this.evalPosition()) >= V
.THRESHOLD_MATE
);
1162 if (!finish
&& !this.atLeastOneMove())
1164 // Test mate (for other variants)
1165 const score
= this.checkGameEnd();
1169 this.undo(moves1
[i
]);
1174 // Rank moves using a min-max at depth 2
1175 for (let i
=0; i
<moves1
.length
; i
++)
1177 // Initial self evaluation is very low: "I'm checkmated"
1178 moves1
[i
].eval
= (color
=="w" ? -1 : 1) * maxeval
;
1179 this.play(moves1
[i
]);
1180 let eval2
= undefined;
1181 if (this.atLeastOneMove())
1183 // Initial enemy evaluation is very low too, for him
1184 eval2
= (color
=="w" ? 1 : -1) * maxeval
;
1185 // Second half-move:
1186 let moves2
= this.getAllValidMoves("computer");
1187 for (let j
=0; j
<moves2
.length
; j
++)
1189 this.play(moves2
[j
]);
1190 let evalPos
= undefined;
1191 if (this.atLeastOneMove())
1192 evalPos
= this.evalPosition()
1195 // Working with scores is more accurate (necessary for Loser variant)
1196 const score
= this.checkGameEnd();
1197 evalPos
= (score
=="1/2" ? 0 : (score
=="1-0" ? 1 : -1) * maxeval
);
1199 if ((color
== "w" && evalPos
< eval2
)
1200 || (color
=="b" && evalPos
> eval2
))
1204 this.undo(moves2
[j
]);
1209 const score
= this.checkGameEnd();
1210 eval2
= (score
=="1/2" ? 0 : (score
=="1-0" ? 1 : -1) * maxeval
);
1212 if ((color
=="w" && eval2
> moves1
[i
].eval
)
1213 || (color
=="b" && eval2
< moves1
[i
].eval
))
1215 moves1
[i
].eval
= eval2
;
1217 this.undo(moves1
[i
]);
1219 moves1
.sort( (a
,b
) => { return (color
=="w" ? 1 : -1) * (b
.eval
- a
.eval
); });
1221 let candidates
= [0]; //indices of candidates moves
1222 for (let j
=1; j
<moves1
.length
&& moves1
[j
].eval
== moves1
[0].eval
; j
++)
1224 let currentBest
= moves1
[_
.sample(candidates
, 1)];
1226 // From here, depth >= 3: may take a while, so we control time
1227 const timeStart
= Date
.now();
1229 // Skip depth 3+ if we found a checkmate (or if we are checkmated in 1...)
1230 if (V
.SEARCH_DEPTH
>= 3 && Math
.abs(moves1
[0].eval
) < V
.THRESHOLD_MATE
)
1232 for (let i
=0; i
<moves1
.length
; i
++)
1234 if (Date
.now()-timeStart
>= 5000) //more than 5 seconds
1235 return currentBest
; //depth 2 at least
1236 this.play(moves1
[i
]);
1237 // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
1238 moves1
[i
].eval
= 0.1*moves1
[i
].eval
+
1239 this.alphabeta(V
.SEARCH_DEPTH
-1, -maxeval
, maxeval
);
1240 this.undo(moves1
[i
]);
1242 moves1
.sort( (a
,b
) => {
1243 return (color
=="w" ? 1 : -1) * (b
.eval
- a
.eval
); });
1247 //console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
1250 for (let j
=1; j
<moves1
.length
&& moves1
[j
].eval
== moves1
[0].eval
; j
++)
1252 return moves1
[_
.sample(candidates
, 1)];
1255 alphabeta(depth
, alpha
, beta
)
1257 const maxeval
= V
.INFINITY
;
1258 const color
= this.turn
;
1259 if (!this.atLeastOneMove())
1261 switch (this.checkGameEnd())
1266 const score
= this.checkGameEnd();
1267 return (score
=="1/2" ? 0 : (score
=="1-0" ? 1 : -1) * maxeval
);
1271 return this.evalPosition();
1272 const moves
= this.getAllValidMoves("computer");
1273 let v
= color
=="w" ? -maxeval : maxeval
;
1276 for (let i
=0; i
<moves
.length
; i
++)
1278 this.play(moves
[i
]);
1279 v
= Math
.max(v
, this.alphabeta(depth
-1, alpha
, beta
));
1280 this.undo(moves
[i
]);
1281 alpha
= Math
.max(alpha
, v
);
1283 break; //beta cutoff
1288 for (let i
=0; i
<moves
.length
; i
++)
1290 this.play(moves
[i
]);
1291 v
= Math
.min(v
, this.alphabeta(depth
-1, alpha
, beta
));
1292 this.undo(moves
[i
]);
1293 beta
= Math
.min(beta
, v
);
1295 break; //alpha cutoff
1304 // Just count material for now
1305 for (let i
=0; i
<V
.size
.x
; i
++)
1307 for (let j
=0; j
<V
.size
.y
; j
++)
1309 if (this.board
[i
][j
] != V
.EMPTY
)
1311 const sign
= this.getColor(i
,j
) == "w" ? 1 : -1;
1312 evaluation
+= sign
* V
.VALUES
[this.getPiece(i
,j
)];
1319 /////////////////////////
1320 // MOVES + GAME NOTATION
1321 /////////////////////////
1323 // Context: just before move is played, turn hasn't changed
1326 if (move.appear
.length
== 2 && move.appear
[0].p
== V
.KING
) //castle
1327 return (move.end
.y
< move.start
.y
? "0-0-0" : "0-0");
1329 // Translate final square
1330 const finalSquare
= V
.CoordsToSquare(move.end
);
1332 const piece
= this.getPiece(move.start
.x
, move.start
.y
);
1333 if (piece
== V
.PAWN
)
1337 if (move.vanish
.length
> move.appear
.length
)
1340 const startColumn
= V
.CoordToColumn(move.start
.y
);
1341 notation
= startColumn
+ "x" + finalSquare
;
1344 notation
= finalSquare
;
1345 if (move.appear
.length
> 0 && move.appear
[0].p
!= V
.PAWN
) //promotion
1346 notation
+= "=" + move.appear
[0].p
.toUpperCase();
1353 return piece
.toUpperCase() +
1354 (move.vanish
.length
> move.appear
.length
? "x" : "") + finalSquare
;
1358 // Complete the usual notation, may be required for de-ambiguification
1359 getLongNotation(move)
1361 // Not encoding move. But short+long is enough
1362 return V
.CoordsToSquare(move.start
) + V
.CoordsToSquare(move.end
);
1365 // The score is already computed when calling this function
1366 getPGN(mycolor
, score
, fenStart
, mode
)
1369 pgn
+= '[Site "vchess.club"]<br>';
1370 const opponent
= mode
=="human" ? "Anonymous" : "Computer";
1371 pgn
+= '[Variant "' + variant
+ '"]<br>';
1372 pgn
+= '[Date "' + getDate(new Date()) + '"]<br>';
1373 pgn
+= '[White "' + (mycolor
=='w'?'Myself':opponent
) + '"]<br>';
1374 pgn
+= '[Black "' + (mycolor
=='b'?'Myself':opponent
) + '"]<br>';
1375 pgn
+= '[FenStart "' + fenStart
+ '"]<br>';
1376 pgn
+= '[Fen "' + this.getFen() + '"]<br>';
1377 pgn
+= '[Result "' + score
+ '"]<br><br>';
1380 for (let i
=0; i
<this.moves
.length
; i
++)
1383 pgn
+= ((i
/2)+1) + ".";
1384 pgn
+= this.moves
[i
].notation
[0] + " ";
1388 // "Complete moves" PGN (helping in ambiguous cases)
1389 for (let i
=0; i
<this.moves
.length
; i
++)
1392 pgn
+= ((i
/2)+1) + ".";
1393 pgn
+= this.moves
[i
].notation
[1] + " ";