1 // (Orthodox) Chess rules are defined in ChessRules class.
2 // Variants generally inherit from it, and modify some parts.
4 import { ArrayFun
} from "@/utils/array";
5 import { randInt
, shuffle
} from "@/utils/alea";
7 // class "PiPo": Piece + Position
8 export const PiPo
= class PiPo
{
9 // o: {piece[p], color[c], posX[x], posY[y]}
18 export const Move
= class Move
{
19 // o: {appear, vanish, [start,] [end,]}
20 // appear,vanish = arrays of PiPo
21 // start,end = coordinates to apply to trigger move visually (think castle)
23 this.appear
= o
.appear
;
24 this.vanish
= o
.vanish
;
25 this.start
= o
.start
|| { x: o
.vanish
[0].x
, y: o
.vanish
[0].y
};
26 this.end
= o
.end
|| { x: o
.appear
[0].x
, y: o
.appear
[0].y
};
30 // NOTE: x coords = top to bottom; y = left to right
31 // (from white player perspective)
32 export const ChessRules
= class ChessRules
{
37 // Some variants don't have flags:
38 static get HasFlags() {
43 static get HasCastle() {
47 // Pawns specifications
48 static get PawnSpecs() {
50 directions: { 'w': -1, 'b': 1 },
51 initShift: { w: 1, b: 1 },
54 promotions: [V
.ROOK
, V
.KNIGHT
, V
.BISHOP
, V
.QUEEN
],
56 captureBackward: false,
61 // En-passant captures need a stack of squares:
62 static get HasEnpassant() {
66 // Some variants cannot have analyse mode
67 static get CanAnalyze() {
70 // Patch: issues with javascript OOP, objects can't access static fields.
75 // Some variants show incomplete information,
76 // and thus show only a partial moves list or no list at all.
77 static get ShowMoves() {
84 // Sometimes moves must remain hidden until game ends
85 static get SomeHiddenMoves() {
88 get someHiddenMoves() {
89 return V
.SomeHiddenMoves
;
92 // Generally true, unless the variant includes random effects
93 static get CorrConfirm() {
97 // Used for Monochrome variant (TODO: harmonize: !canFlip ==> showFirstTurn)
102 // Some variants always show the same orientation
103 static get CanFlip() {
110 // For (generally old) variants without checkered board
111 static get Monochrome() {
115 // Some games are drawn unusually (bottom right corner is black)
116 static get DarkBottomRight() {
120 // Some variants require lines drawing
124 // Draw all inter-squares lines
125 for (let i
= 0; i
<= V
.size
.x
; i
++)
126 lines
.push([[i
, 0], [i
, V
.size
.y
]]);
127 for (let j
= 0; j
<= V
.size
.y
; j
++)
128 lines
.push([[0, j
], [V
.size
.x
, j
]]);
134 // In some variants, the player who repeat a position loses
135 static get LoseOnRepetition() {
138 // And in some others (Iceage), repetitions should be ignored:
139 static get IgnoreRepetition() {
143 // In some variants, result depends on the position:
144 return V
.LoseOnRepetition
;
147 // At some stages, some games could wait clicks only:
152 // Some variants use click infos:
157 // Some variants may need to highlight squares on hover (Hamilton, Weiqi...)
162 static get IMAGE_EXTENSION() {
163 // All pieces should be in the SVG format
167 // Turn "wb" into "B" (for FEN)
168 static board2fen(b
) {
169 return b
[0] == "w" ? b
[1].toUpperCase() : b
[1];
172 // Turn "p" into "bp" (for board)
173 static fen2board(f
) {
174 return f
.charCodeAt(0) <= 90 ? "w" + f
.toLowerCase() : "b" + f
;
177 // Check if FEN describes a board situation correctly
178 static IsGoodFen(fen
) {
179 const fenParsed
= V
.ParseFen(fen
);
181 if (!V
.IsGoodPosition(fenParsed
.position
)) return false;
183 if (!fenParsed
.turn
|| !V
.IsGoodTurn(fenParsed
.turn
)) return false;
184 // 3) Check moves count
185 if (!fenParsed
.movesCount
|| !(parseInt(fenParsed
.movesCount
, 10) >= 0))
188 if (V
.HasFlags
&& (!fenParsed
.flags
|| !V
.IsGoodFlags(fenParsed
.flags
)))
190 // 5) Check enpassant
193 (!fenParsed
.enpassant
|| !V
.IsGoodEnpassant(fenParsed
.enpassant
))
200 // Is position part of the FEN a priori correct?
201 static IsGoodPosition(position
) {
202 if (position
.length
== 0) return false;
203 const rows
= position
.split("/");
204 if (rows
.length
!= V
.size
.x
) return false;
205 let kings
= { "k": 0, "K": 0 };
206 for (let row
of rows
) {
208 for (let i
= 0; i
< row
.length
; i
++) {
209 if (['K','k'].includes(row
[i
])) kings
[row
[i
]]++;
210 if (V
.PIECES
.includes(row
[i
].toLowerCase())) sumElts
++;
212 const num
= parseInt(row
[i
], 10);
213 if (isNaN(num
) || num
<= 0) return false;
217 if (sumElts
!= V
.size
.y
) return false;
219 // Both kings should be on board. Exactly one per color.
220 if (Object
.values(kings
).some(v
=> v
!= 1)) return false;
225 static IsGoodTurn(turn
) {
226 return ["w", "b"].includes(turn
);
230 static IsGoodFlags(flags
) {
231 // NOTE: a little too permissive to work with more variants
232 return !!flags
.match(/^[a-z]{4,4}$/);
235 // NOTE: not with regexp to adapt to different board sizes. (TODO?)
236 static IsGoodEnpassant(enpassant
) {
237 if (enpassant
!= "-") {
238 const ep
= V
.SquareToCoords(enpassant
);
239 if (isNaN(ep
.x
) || !V
.OnBoard(ep
)) return false;
244 // 3 --> d (column number to letter)
245 static CoordToColumn(colnum
) {
246 return String
.fromCharCode(97 + colnum
);
249 // d --> 3 (column letter to number)
250 static ColumnToCoord(column
) {
251 return column
.charCodeAt(0) - 97;
255 static SquareToCoords(sq
) {
257 // NOTE: column is always one char => max 26 columns
258 // row is counted from black side => subtraction
259 x: V
.size
.x
- parseInt(sq
.substr(1), 10),
260 y: sq
[0].charCodeAt() - 97
265 static CoordsToSquare(coords
) {
266 return V
.CoordToColumn(coords
.y
) + (V
.size
.x
- coords
.x
);
269 // Path to pieces (standard ones in pieces/ folder)
274 // Path to promotion pieces (usually the same)
276 return this.getPpath(m
.appear
[0].c
+ m
.appear
[0].p
);
279 // Aggregates flags into one object
281 return this.castleFlags
;
285 disaggregateFlags(flags
) {
286 this.castleFlags
= flags
;
289 // En-passant square, if any
290 getEpSquare(moveOrSquare
) {
291 if (!moveOrSquare
) return undefined; //TODO: necessary line?!
292 if (typeof moveOrSquare
=== "string") {
293 const square
= moveOrSquare
;
294 if (square
== "-") return undefined;
295 return V
.SquareToCoords(square
);
297 // Argument is a move:
298 const move = moveOrSquare
;
299 const s
= move.start
,
303 Math
.abs(s
.x
- e
.x
) == 2 &&
304 // Next conditions for variants like Atomic or Rifle, Recycle...
305 (move.appear
.length
> 0 && move.appear
[0].p
== V
.PAWN
) &&
306 (move.vanish
.length
> 0 && move.vanish
[0].p
== V
.PAWN
)
313 return undefined; //default
316 // Can thing on square1 take thing on square2
317 canTake([x1
, y1
], [x2
, y2
]) {
318 return this.getColor(x1
, y1
) !== this.getColor(x2
, y2
);
321 // Is (x,y) on the chessboard?
322 static OnBoard(x
, y
) {
323 return x
>= 0 && x
< V
.size
.x
&& y
>= 0 && y
< V
.size
.y
;
326 // Used in interface: 'side' arg == player color
327 canIplay(side
, [x
, y
]) {
328 return this.turn
== side
&& this.getColor(x
, y
) == side
;
331 // On which squares is color under check ? (for interface)
333 const color
= this.turn
;
335 this.underCheck(color
)
336 // kingPos must be duplicated, because it may change:
337 ? [JSON
.parse(JSON
.stringify(this.kingPos
[color
]))]
345 // Setup the initial random (asymmetric) position
346 static GenRandInitFen(randomness
) {
349 return "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w 0 ahah -";
351 let pieces
= { w: new Array(8), b: new Array(8) };
353 // Shuffle pieces on first (and last rank if randomness == 2)
354 for (let c
of ["w", "b"]) {
355 if (c
== 'b' && randomness
== 1) {
356 pieces
['b'] = pieces
['w'];
361 let positions
= ArrayFun
.range(8);
363 // Get random squares for bishops
364 let randIndex
= 2 * randInt(4);
365 const bishop1Pos
= positions
[randIndex
];
366 // The second bishop must be on a square of different color
367 let randIndex_tmp
= 2 * randInt(4) + 1;
368 const bishop2Pos
= positions
[randIndex_tmp
];
369 // Remove chosen squares
370 positions
.splice(Math
.max(randIndex
, randIndex_tmp
), 1);
371 positions
.splice(Math
.min(randIndex
, randIndex_tmp
), 1);
373 // Get random squares for knights
374 randIndex
= randInt(6);
375 const knight1Pos
= positions
[randIndex
];
376 positions
.splice(randIndex
, 1);
377 randIndex
= randInt(5);
378 const knight2Pos
= positions
[randIndex
];
379 positions
.splice(randIndex
, 1);
381 // Get random square for queen
382 randIndex
= randInt(4);
383 const queenPos
= positions
[randIndex
];
384 positions
.splice(randIndex
, 1);
386 // Rooks and king positions are now fixed,
387 // because of the ordering rook-king-rook
388 const rook1Pos
= positions
[0];
389 const kingPos
= positions
[1];
390 const rook2Pos
= positions
[2];
392 // Finally put the shuffled pieces in the board array
393 pieces
[c
][rook1Pos
] = "r";
394 pieces
[c
][knight1Pos
] = "n";
395 pieces
[c
][bishop1Pos
] = "b";
396 pieces
[c
][queenPos
] = "q";
397 pieces
[c
][kingPos
] = "k";
398 pieces
[c
][bishop2Pos
] = "b";
399 pieces
[c
][knight2Pos
] = "n";
400 pieces
[c
][rook2Pos
] = "r";
401 flags
+= V
.CoordToColumn(rook1Pos
) + V
.CoordToColumn(rook2Pos
);
403 // Add turn + flags + enpassant
405 pieces
["b"].join("") +
406 "/pppppppp/8/8/8/8/PPPPPPPP/" +
407 pieces
["w"].join("").toUpperCase() +
408 " w 0 " + flags
+ " -"
412 // "Parse" FEN: just return untransformed string data
413 static ParseFen(fen
) {
414 const fenParts
= fen
.split(" ");
416 position: fenParts
[0],
418 movesCount: fenParts
[2]
421 if (V
.HasFlags
) Object
.assign(res
, { flags: fenParts
[nextIdx
++] });
422 if (V
.HasEnpassant
) Object
.assign(res
, { enpassant: fenParts
[nextIdx
] });
426 // Return current fen (game state)
429 this.getBaseFen() + " " +
430 this.getTurnFen() + " " +
432 (V
.HasFlags
? " " + this.getFlagsFen() : "") +
433 (V
.HasEnpassant
? " " + this.getEnpassantFen() : "")
438 // Omit movesCount, only variable allowed to differ
440 this.getBaseFen() + "_" +
442 (V
.HasFlags
? "_" + this.getFlagsFen() : "") +
443 (V
.HasEnpassant
? "_" + this.getEnpassantFen() : "")
447 // Position part of the FEN string
449 const format
= (count
) => {
450 // if more than 9 consecutive free spaces, break the integer,
451 // otherwise FEN parsing will fail.
452 if (count
<= 9) return count
;
453 // Most boards of size < 18:
454 if (count
<= 18) return "9" + (count
- 9);
456 return "99" + (count
- 18);
459 for (let i
= 0; i
< V
.size
.x
; i
++) {
461 for (let j
= 0; j
< V
.size
.y
; j
++) {
462 if (this.board
[i
][j
] == V
.EMPTY
) emptyCount
++;
464 if (emptyCount
> 0) {
465 // Add empty squares in-between
466 position
+= format(emptyCount
);
469 position
+= V
.board2fen(this.board
[i
][j
]);
472 if (emptyCount
> 0) {
474 position
+= format(emptyCount
);
476 if (i
< V
.size
.x
- 1) position
+= "/"; //separate rows
485 // Flags part of the FEN string
489 for (let c
of ["w", "b"])
490 flags
+= this.castleFlags
[c
].map(V
.CoordToColumn
).join("");
494 // Enpassant part of the FEN string
496 const L
= this.epSquares
.length
;
497 if (!this.epSquares
[L
- 1]) return "-"; //no en-passant
498 return V
.CoordsToSquare(this.epSquares
[L
- 1]);
501 // Turn position fen into double array ["wb","wp","bk",...]
502 static GetBoard(position
) {
503 const rows
= position
.split("/");
504 let board
= ArrayFun
.init(V
.size
.x
, V
.size
.y
, "");
505 for (let i
= 0; i
< rows
.length
; i
++) {
507 for (let indexInRow
= 0; indexInRow
< rows
[i
].length
; indexInRow
++) {
508 const character
= rows
[i
][indexInRow
];
509 const num
= parseInt(character
, 10);
510 // If num is a number, just shift j:
511 if (!isNaN(num
)) j
+= num
;
512 // Else: something at position i,j
513 else board
[i
][j
++] = V
.fen2board(character
);
519 // Extract (relevant) flags from fen
521 // white a-castle, h-castle, black a-castle, h-castle
522 this.castleFlags
= { w: [-1, -1], b: [-1, -1] };
523 for (let i
= 0; i
< 4; i
++) {
524 this.castleFlags
[i
< 2 ? "w" : "b"][i
% 2] =
525 V
.ColumnToCoord(fenflags
.charAt(i
));
532 // Fen string fully describes the game state
535 // In printDiagram() fen isn't supply because only getPpath() is used
536 // TODO: find a better solution!
538 const fenParsed
= V
.ParseFen(fen
);
539 this.board
= V
.GetBoard(fenParsed
.position
);
540 this.turn
= fenParsed
.turn
;
541 this.movesCount
= parseInt(fenParsed
.movesCount
, 10);
542 this.setOtherVariables(fen
);
545 // Scan board for kings positions
546 // TODO: should be done from board, no need for the complete FEN
548 // Squares of white and black king:
549 this.kingPos
= { w: [-1, -1], b: [-1, -1] };
550 const fenRows
= V
.ParseFen(fen
).position
.split("/");
551 for (let i
= 0; i
< fenRows
.length
; i
++) {
552 let k
= 0; //column index on board
553 for (let j
= 0; j
< fenRows
[i
].length
; j
++) {
554 switch (fenRows
[i
].charAt(j
)) {
556 this.kingPos
["b"] = [i
, k
];
559 this.kingPos
["w"] = [i
, k
];
562 const num
= parseInt(fenRows
[i
].charAt(j
), 10);
563 if (!isNaN(num
)) k
+= num
- 1;
571 // Some additional variables from FEN (variant dependant)
572 setOtherVariables(fen
) {
573 // Set flags and enpassant:
574 const parsedFen
= V
.ParseFen(fen
);
575 if (V
.HasFlags
) this.setFlags(parsedFen
.flags
);
576 if (V
.HasEnpassant
) {
578 parsedFen
.enpassant
!= "-"
579 ? this.getEpSquare(parsedFen
.enpassant
)
581 this.epSquares
= [epSq
];
583 // Search for kings positions:
587 /////////////////////
591 return { x: 8, y: 8 };
594 // Color of thing on square (i,j). 'undefined' if square is empty
596 return this.board
[i
][j
].charAt(0);
599 // Piece type on square (i,j). 'undefined' if square is empty
601 return this.board
[i
][j
].charAt(1);
604 // Get opponent color
605 static GetOppCol(color
) {
606 return color
== "w" ? "b" : "w";
609 // Pieces codes (for a clearer code)
616 static get KNIGHT() {
619 static get BISHOP() {
630 static get PIECES() {
631 return [V
.PAWN
, V
.ROOK
, V
.KNIGHT
, V
.BISHOP
, V
.QUEEN
, V
.KING
];
639 // Some pieces movements
670 // All possible moves from selected square
671 getPotentialMovesFrom(sq
) {
672 switch (this.getPiece(sq
[0], sq
[1])) {
673 case V
.PAWN: return this.getPotentialPawnMoves(sq
);
674 case V
.ROOK: return this.getPotentialRookMoves(sq
);
675 case V
.KNIGHT: return this.getPotentialKnightMoves(sq
);
676 case V
.BISHOP: return this.getPotentialBishopMoves(sq
);
677 case V
.QUEEN: return this.getPotentialQueenMoves(sq
);
678 case V
.KING: return this.getPotentialKingMoves(sq
);
680 return []; //never reached (but some variants may use it: Bario...)
683 // Build a regular move from its initial and destination squares.
684 // tr: transformation
685 getBasicMove([sx
, sy
], [ex
, ey
], tr
) {
686 const initColor
= this.getColor(sx
, sy
);
687 const initPiece
= this.board
[sx
][sy
].charAt(1);
693 c: !!tr
? tr
.c : initColor
,
694 p: !!tr
? tr
.p : initPiece
707 // The opponent piece disappears if we take it
708 if (this.board
[ex
][ey
] != V
.EMPTY
) {
713 c: this.getColor(ex
, ey
),
714 p: this.board
[ex
][ey
].charAt(1)
722 // Generic method to find possible moves of non-pawn pieces:
723 // "sliding or jumping"
724 getSlideNJumpMoves([x
, y
], steps
, oneStep
) {
726 outerLoop: for (let step
of steps
) {
729 while (V
.OnBoard(i
, j
) && this.board
[i
][j
] == V
.EMPTY
) {
730 moves
.push(this.getBasicMove([x
, y
], [i
, j
]));
731 if (!!oneStep
) continue outerLoop
;
735 if (V
.OnBoard(i
, j
) && this.canTake([x
, y
], [i
, j
]))
736 moves
.push(this.getBasicMove([x
, y
], [i
, j
]));
741 // Special case of en-passant captures: treated separately
742 getEnpassantCaptures([x
, y
], shiftX
) {
743 const Lep
= this.epSquares
.length
;
744 const epSquare
= this.epSquares
[Lep
- 1]; //always at least one element
745 let enpassantMove
= null;
748 epSquare
.x
== x
+ shiftX
&&
749 Math
.abs(epSquare
.y
- y
) == 1
751 enpassantMove
= this.getBasicMove([x
, y
], [epSquare
.x
, epSquare
.y
]);
752 enpassantMove
.vanish
.push({
755 p: this.board
[x
][epSquare
.y
].charAt(1),
756 c: this.getColor(x
, epSquare
.y
)
759 return !!enpassantMove
? [enpassantMove
] : [];
762 // Consider all potential promotions:
763 addPawnMoves([x1
, y1
], [x2
, y2
], moves
, promotions
) {
764 let finalPieces
= [V
.PAWN
];
765 const color
= this.turn
; //this.getColor(x1, y1);
766 const lastRank
= (color
== "w" ? 0 : V
.size
.x
- 1);
767 if (x2
== lastRank
) {
768 // promotions arg: special override for Hiddenqueen variant
769 if (!!promotions
) finalPieces
= promotions
;
770 else if (!!V
.PawnSpecs
.promotions
) finalPieces
= V
.PawnSpecs
.promotions
;
773 for (let piece
of finalPieces
) {
774 tr
= (piece
!= V
.PAWN
? { c: color
, p: piece
} : null);
775 moves
.push(this.getBasicMove([x1
, y1
], [x2
, y2
], tr
));
779 // What are the pawn moves from square x,y ?
780 getPotentialPawnMoves([x
, y
], promotions
) {
781 const color
= this.turn
; //this.getColor(x, y);
782 const [sizeX
, sizeY
] = [V
.size
.x
, V
.size
.y
];
783 const pawnShiftX
= V
.PawnSpecs
.directions
[color
];
784 const firstRank
= (color
== "w" ? sizeX
- 1 : 0);
785 const forward
= (color
== 'w' ? -1 : 1);
787 // Pawn movements in shiftX direction:
788 const getPawnMoves
= (shiftX
) => {
790 // NOTE: next condition is generally true (no pawn on last rank)
791 if (x
+ shiftX
>= 0 && x
+ shiftX
< sizeX
) {
792 if (this.board
[x
+ shiftX
][y
] == V
.EMPTY
) {
793 // One square forward (or backward)
794 this.addPawnMoves([x
, y
], [x
+ shiftX
, y
], moves
, promotions
);
795 // Next condition because pawns on 1st rank can generally jump
797 V
.PawnSpecs
.twoSquares
&&
799 (color
== 'w' && x
>= V
.size
.x
- 1 - V
.PawnSpecs
.initShift
['w'])
801 (color
== 'b' && x
<= V
.PawnSpecs
.initShift
['b'])
806 this.board
[x
+ 2 * shiftX
][y
] == V
.EMPTY
809 moves
.push(this.getBasicMove([x
, y
], [x
+ 2 * shiftX
, y
]));
811 V
.PawnSpecs
.threeSquares
&&
812 this.board
[x
+ 3 * shiftX
][y
] == V
.EMPTY
814 // Three squares jump
815 moves
.push(this.getBasicMove([x
, y
], [x
+ 3 * shiftX
, y
]));
821 if (V
.PawnSpecs
.canCapture
) {
822 for (let shiftY
of [-1, 1]) {
823 if (y
+ shiftY
>= 0 && y
+ shiftY
< sizeY
) {
825 this.board
[x
+ shiftX
][y
+ shiftY
] != V
.EMPTY
&&
826 this.canTake([x
, y
], [x
+ shiftX
, y
+ shiftY
])
829 [x
, y
], [x
+ shiftX
, y
+ shiftY
],
834 V
.PawnSpecs
.captureBackward
&& shiftX
== forward
&&
835 x
- shiftX
>= 0 && x
- shiftX
< V
.size
.x
&&
836 this.board
[x
- shiftX
][y
+ shiftY
] != V
.EMPTY
&&
837 this.canTake([x
, y
], [x
- shiftX
, y
+ shiftY
])
840 [x
, y
], [x
- shiftX
, y
+ shiftY
],
851 let pMoves
= getPawnMoves(pawnShiftX
);
852 if (V
.PawnSpecs
.bidirectional
)
853 pMoves
= pMoves
.concat(getPawnMoves(-pawnShiftX
));
855 if (V
.HasEnpassant
) {
856 // NOTE: backward en-passant captures are not considered
857 // because no rules define them (for now).
858 Array
.prototype.push
.apply(
860 this.getEnpassantCaptures([x
, y
], pawnShiftX
)
867 // What are the rook moves from square x,y ?
868 getPotentialRookMoves(sq
) {
869 return this.getSlideNJumpMoves(sq
, V
.steps
[V
.ROOK
]);
872 // What are the knight moves from square x,y ?
873 getPotentialKnightMoves(sq
) {
874 return this.getSlideNJumpMoves(sq
, V
.steps
[V
.KNIGHT
], "oneStep");
877 // What are the bishop moves from square x,y ?
878 getPotentialBishopMoves(sq
) {
879 return this.getSlideNJumpMoves(sq
, V
.steps
[V
.BISHOP
]);
882 // What are the queen moves from square x,y ?
883 getPotentialQueenMoves(sq
) {
884 return this.getSlideNJumpMoves(
886 V
.steps
[V
.ROOK
].concat(V
.steps
[V
.BISHOP
])
890 // What are the king moves from square x,y ?
891 getPotentialKingMoves(sq
) {
892 // Initialize with normal moves
893 let moves
= this.getSlideNJumpMoves(
895 V
.steps
[V
.ROOK
].concat(V
.steps
[V
.BISHOP
]),
898 if (V
.HasCastle
&& this.castleFlags
[this.turn
].some(v
=> v
< V
.size
.y
))
899 moves
= moves
.concat(this.getCastleMoves(sq
));
903 // "castleInCheck" arg to let some variants castle under check
904 getCastleMoves([x
, y
], finalSquares
, castleInCheck
, castleWith
) {
905 const c
= this.getColor(x
, y
);
908 const oppCol
= V
.GetOppCol(c
);
911 finalSquares
= finalSquares
|| [ [2, 3], [V
.size
.y
- 2, V
.size
.y
- 3] ];
912 const castlingKing
= this.board
[x
][y
].charAt(1);
916 castleSide
++ //large, then small
918 if (this.castleFlags
[c
][castleSide
] >= V
.size
.y
) continue;
919 // If this code is reached, rook and king are on initial position
921 // NOTE: in some variants this is not a rook
922 const rookPos
= this.castleFlags
[c
][castleSide
];
923 const castlingPiece
= this.board
[x
][rookPos
].charAt(1);
925 this.board
[x
][rookPos
] == V
.EMPTY
||
926 this.getColor(x
, rookPos
) != c
||
927 (!!castleWith
&& !castleWith
.includes(castlingPiece
))
929 // Rook is not here, or changed color (see Benedict)
933 // Nothing on the path of the king ? (and no checks)
934 const finDist
= finalSquares
[castleSide
][0] - y
;
935 let step
= finDist
/ Math
.max(1, Math
.abs(finDist
));
939 (!castleInCheck
&& this.isAttacked([x
, i
], oppCol
)) ||
941 this.board
[x
][i
] != V
.EMPTY
&&
942 // NOTE: next check is enough, because of chessboard constraints
943 (this.getColor(x
, i
) != c
|| ![y
, rookPos
].includes(i
))
946 continue castlingCheck
;
949 } while (i
!= finalSquares
[castleSide
][0]);
951 // Nothing on the path to the rook?
952 step
= castleSide
== 0 ? -1 : 1;
953 for (i
= y
+ step
; i
!= rookPos
; i
+= step
) {
954 if (this.board
[x
][i
] != V
.EMPTY
) continue castlingCheck
;
957 // Nothing on final squares, except maybe king and castling rook?
958 for (i
= 0; i
< 2; i
++) {
960 finalSquares
[castleSide
][i
] != rookPos
&&
961 this.board
[x
][finalSquares
[castleSide
][i
]] != V
.EMPTY
&&
963 finalSquares
[castleSide
][i
] != y
||
964 this.getColor(x
, finalSquares
[castleSide
][i
]) != c
967 continue castlingCheck
;
971 // If this code is reached, castle is valid
977 y: finalSquares
[castleSide
][0],
983 y: finalSquares
[castleSide
][1],
989 // King might be initially disguised (Titan...)
990 new PiPo({ x: x
, y: y
, p: castlingKing
, c: c
}),
991 new PiPo({ x: x
, y: rookPos
, p: castlingPiece
, c: c
})
994 Math
.abs(y
- rookPos
) <= 2
995 ? { x: x
, y: rookPos
}
996 : { x: x
, y: y
+ 2 * (castleSide
== 0 ? -1 : 1) }
1004 ////////////////////
1007 // For the interface: possible moves for the current turn from square sq
1008 getPossibleMovesFrom(sq
) {
1009 return this.filterValid(this.getPotentialMovesFrom(sq
));
1012 // TODO: promotions (into R,B,N,Q) should be filtered only once
1013 filterValid(moves
) {
1014 if (moves
.length
== 0) return [];
1015 const color
= this.turn
;
1016 return moves
.filter(m
=> {
1018 const res
= !this.underCheck(color
);
1024 getAllPotentialMoves() {
1025 const color
= this.turn
;
1026 let potentialMoves
= [];
1027 for (let i
= 0; i
< V
.size
.x
; i
++) {
1028 for (let j
= 0; j
< V
.size
.y
; j
++) {
1029 if (this.board
[i
][j
] != V
.EMPTY
&& this.getColor(i
, j
) == color
) {
1030 Array
.prototype.push
.apply(
1032 this.getPotentialMovesFrom([i
, j
])
1037 return potentialMoves
;
1040 // Search for all valid moves considering current turn
1041 // (for engine and game end)
1042 getAllValidMoves() {
1043 return this.filterValid(this.getAllPotentialMoves());
1046 // Stop at the first move found
1047 // TODO: not really, it explores all moves from a square (one is enough).
1048 // Possible fix: add extra arg "oneMove" to getPotentialMovesFrom,
1049 // and then return only boolean true at first move found
1050 // (in all getPotentialXXXMoves() ... for all variants ...)
1052 const color
= this.turn
;
1053 for (let i
= 0; i
< V
.size
.x
; i
++) {
1054 for (let j
= 0; j
< V
.size
.y
; j
++) {
1055 if (this.board
[i
][j
] != V
.EMPTY
&& this.getColor(i
, j
) == color
) {
1056 const moves
= this.getPotentialMovesFrom([i
, j
]);
1057 if (moves
.length
> 0) {
1058 for (let k
= 0; k
< moves
.length
; k
++)
1059 if (this.filterValid([moves
[k
]]).length
> 0) return true;
1067 // Check if pieces of given color are attacking (king) on square x,y
1068 isAttacked(sq
, color
) {
1070 this.isAttackedByPawn(sq
, color
) ||
1071 this.isAttackedByRook(sq
, color
) ||
1072 this.isAttackedByKnight(sq
, color
) ||
1073 this.isAttackedByBishop(sq
, color
) ||
1074 this.isAttackedByQueen(sq
, color
) ||
1075 this.isAttackedByKing(sq
, color
)
1079 // Generic method for non-pawn pieces ("sliding or jumping"):
1080 // is x,y attacked by a piece of given color ?
1081 isAttackedBySlideNJump([x
, y
], color
, piece
, steps
, oneStep
) {
1082 for (let step
of steps
) {
1083 let rx
= x
+ step
[0],
1085 while (V
.OnBoard(rx
, ry
) && this.board
[rx
][ry
] == V
.EMPTY
&& !oneStep
) {
1090 V
.OnBoard(rx
, ry
) &&
1091 this.board
[rx
][ry
] != V
.EMPTY
&&
1092 this.getPiece(rx
, ry
) == piece
&&
1093 this.getColor(rx
, ry
) == color
1101 // Is square x,y attacked by 'color' pawns ?
1102 isAttackedByPawn(sq
, color
) {
1103 const pawnShift
= (color
== "w" ? 1 : -1);
1104 return this.isAttackedBySlideNJump(
1108 [[pawnShift
, 1], [pawnShift
, -1]],
1113 // Is square x,y attacked by 'color' rooks ?
1114 isAttackedByRook(sq
, color
) {
1115 return this.isAttackedBySlideNJump(sq
, color
, V
.ROOK
, V
.steps
[V
.ROOK
]);
1118 // Is square x,y attacked by 'color' knights ?
1119 isAttackedByKnight(sq
, color
) {
1120 return this.isAttackedBySlideNJump(
1129 // Is square x,y attacked by 'color' bishops ?
1130 isAttackedByBishop(sq
, color
) {
1131 return this.isAttackedBySlideNJump(sq
, color
, V
.BISHOP
, V
.steps
[V
.BISHOP
]);
1134 // Is square x,y attacked by 'color' queens ?
1135 isAttackedByQueen(sq
, color
) {
1136 return this.isAttackedBySlideNJump(
1140 V
.steps
[V
.ROOK
].concat(V
.steps
[V
.BISHOP
])
1144 // Is square x,y attacked by 'color' king(s) ?
1145 isAttackedByKing(sq
, color
) {
1146 return this.isAttackedBySlideNJump(
1150 V
.steps
[V
.ROOK
].concat(V
.steps
[V
.BISHOP
]),
1155 // Is color under check after his move ?
1157 return this.isAttacked(this.kingPos
[color
], V
.GetOppCol(color
));
1163 // Apply a move on board
1164 static PlayOnBoard(board
, move) {
1165 for (let psq
of move.vanish
) board
[psq
.x
][psq
.y
] = V
.EMPTY
;
1166 for (let psq
of move.appear
) board
[psq
.x
][psq
.y
] = psq
.c
+ psq
.p
;
1168 // Un-apply the played move
1169 static UndoOnBoard(board
, move) {
1170 for (let psq
of move.appear
) board
[psq
.x
][psq
.y
] = V
.EMPTY
;
1171 for (let psq
of move.vanish
) board
[psq
.x
][psq
.y
] = psq
.c
+ psq
.p
;
1178 // if (!this.states) this.states = [];
1179 // const stateFen = this.getFen() + JSON.stringify(this.kingPos);
1180 // this.states.push(stateFen);
1183 // Save flags (for undo)
1184 if (V
.HasFlags
) move.flags
= JSON
.stringify(this.aggregateFlags());
1185 if (V
.HasEnpassant
) this.epSquares
.push(this.getEpSquare(move));
1186 V
.PlayOnBoard(this.board
, move);
1187 this.turn
= V
.GetOppCol(this.turn
);
1189 this.postPlay(move);
1192 updateCastleFlags(move, piece
, color
) {
1193 // TODO: check flags. If already off, no need to always re-evaluate
1194 const c
= color
|| V
.GetOppCol(this.turn
);
1195 const firstRank
= (c
== "w" ? V
.size
.x
- 1 : 0);
1196 // Update castling flags if rooks are moved
1197 const oppCol
= this.turn
;
1198 const oppFirstRank
= V
.size
.x
- 1 - firstRank
;
1199 if (piece
== V
.KING
&& move.appear
.length
> 0)
1200 this.castleFlags
[c
] = [V
.size
.y
, V
.size
.y
];
1202 move.start
.x
== firstRank
&& //our rook moves?
1203 this.castleFlags
[c
].includes(move.start
.y
)
1205 const flagIdx
= (move.start
.y
== this.castleFlags
[c
][0] ? 0 : 1);
1206 this.castleFlags
[c
][flagIdx
] = V
.size
.y
;
1208 // NOTE: not "else if" because a rook could take an opposing rook
1210 move.end
.x
== oppFirstRank
&& //we took opponent rook?
1211 this.castleFlags
[oppCol
].includes(move.end
.y
)
1213 const flagIdx
= (move.end
.y
== this.castleFlags
[oppCol
][0] ? 0 : 1);
1214 this.castleFlags
[oppCol
][flagIdx
] = V
.size
.y
;
1218 // After move is played, update variables + flags
1220 const c
= V
.GetOppCol(this.turn
);
1221 let piece
= undefined;
1222 if (move.vanish
.length
>= 1)
1223 // Usual case, something is moved
1224 piece
= move.vanish
[0].p
;
1226 // Crazyhouse-like variants
1227 piece
= move.appear
[0].p
;
1229 // Update king position + flags
1230 if (piece
== V
.KING
&& move.appear
.length
> 0)
1231 this.kingPos
[c
] = [move.appear
[0].x
, move.appear
[0].y
];
1232 if (V
.HasCastle
) this.updateCastleFlags(move, piece
);
1239 if (V
.HasEnpassant
) this.epSquares
.pop();
1240 if (V
.HasFlags
) this.disaggregateFlags(JSON
.parse(move.flags
));
1241 V
.UndoOnBoard(this.board
, move);
1242 this.turn
= V
.GetOppCol(this.turn
);
1244 this.postUndo(move);
1247 // const stateFen = this.getFen() + JSON.stringify(this.kingPos);
1248 // if (stateFen != this.states[this.states.length-1]) debugger;
1249 // this.states.pop();
1252 // After move is undo-ed *and flags resetted*, un-update other variables
1253 // TODO: more symmetry, by storing flags increment in move (?!)
1255 // (Potentially) Reset king position
1256 const c
= this.getColor(move.start
.x
, move.start
.y
);
1257 if (this.getPiece(move.start
.x
, move.start
.y
) == V
.KING
)
1258 this.kingPos
[c
] = [move.start
.x
, move.start
.y
];
1264 // What is the score ? (Interesting if game is over)
1266 if (this.atLeastOneMove()) return "*";
1268 const color
= this.turn
;
1269 // No valid move: stalemate or checkmate?
1270 if (!this.underCheck(color
)) return "1/2";
1272 return (color
== "w" ? "0-1" : "1-0");
1279 static get VALUES() {
1290 // "Checkmate" (unreachable eval)
1291 static get INFINITY() {
1295 // At this value or above, the game is over
1296 static get THRESHOLD_MATE() {
1300 // Search depth: 1,2 for e.g. higher branching factor, 4 for smaller
1301 static get SEARCH_DEPTH() {
1305 // 'movesList' arg for some variants to provide a custom list
1306 getComputerMove(movesList
) {
1307 const maxeval
= V
.INFINITY
;
1308 const color
= this.turn
;
1309 let moves1
= movesList
|| this.getAllValidMoves();
1311 if (moves1
.length
== 0)
1312 // TODO: this situation should not happen
1315 // Rank moves using a min-max at depth 2 (if search_depth >= 2!)
1316 for (let i
= 0; i
< moves1
.length
; i
++) {
1317 this.play(moves1
[i
]);
1318 const score1
= this.getCurrentScore();
1319 if (score1
!= "*") {
1323 : (score1
== "1-0" ? 1 : -1) * maxeval
;
1325 if (V
.SEARCH_DEPTH
== 1 || score1
!= "*") {
1326 if (!moves1
[i
].eval
) moves1
[i
].eval
= this.evalPosition();
1327 this.undo(moves1
[i
]);
1330 // Initial self evaluation is very low: "I'm checkmated"
1331 moves1
[i
].eval
= (color
== "w" ? -1 : 1) * maxeval
;
1332 // Initial enemy evaluation is very low too, for him
1333 let eval2
= (color
== "w" ? 1 : -1) * maxeval
;
1334 // Second half-move:
1335 let moves2
= this.getAllValidMoves();
1336 for (let j
= 0; j
< moves2
.length
; j
++) {
1337 this.play(moves2
[j
]);
1338 const score2
= this.getCurrentScore();
1339 let evalPos
= 0; //1/2 value
1342 evalPos
= this.evalPosition();
1352 (color
== "w" && evalPos
< eval2
) ||
1353 (color
== "b" && evalPos
> eval2
)
1357 this.undo(moves2
[j
]);
1360 (color
== "w" && eval2
> moves1
[i
].eval
) ||
1361 (color
== "b" && eval2
< moves1
[i
].eval
)
1363 moves1
[i
].eval
= eval2
;
1365 this.undo(moves1
[i
]);
1367 moves1
.sort((a
, b
) => {
1368 return (color
== "w" ? 1 : -1) * (b
.eval
- a
.eval
);
1370 // console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));
1372 // Skip depth 3+ if we found a checkmate (or if we are checkmated in 1...)
1373 if (V
.SEARCH_DEPTH
>= 3 && Math
.abs(moves1
[0].eval
) < V
.THRESHOLD_MATE
) {
1374 for (let i
= 0; i
< moves1
.length
; i
++) {
1375 this.play(moves1
[i
]);
1376 // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
1378 0.1 * moves1
[i
].eval
+
1379 this.alphabeta(V
.SEARCH_DEPTH
- 1, -maxeval
, maxeval
);
1380 this.undo(moves1
[i
]);
1382 moves1
.sort((a
, b
) => {
1383 return (color
== "w" ? 1 : -1) * (b
.eval
- a
.eval
);
1387 let candidates
= [0];
1388 for (let i
= 1; i
< moves1
.length
&& moves1
[i
].eval
== moves1
[0].eval
; i
++)
1390 return moves1
[candidates
[randInt(candidates
.length
)]];
1393 alphabeta(depth
, alpha
, beta
) {
1394 const maxeval
= V
.INFINITY
;
1395 const color
= this.turn
;
1396 const score
= this.getCurrentScore();
1398 return score
== "1/2" ? 0 : (score
== "1-0" ? 1 : -1) * maxeval
;
1399 if (depth
== 0) return this.evalPosition();
1400 const moves
= this.getAllValidMoves();
1401 let v
= color
== "w" ? -maxeval : maxeval
;
1403 for (let i
= 0; i
< moves
.length
; i
++) {
1404 this.play(moves
[i
]);
1405 v
= Math
.max(v
, this.alphabeta(depth
- 1, alpha
, beta
));
1406 this.undo(moves
[i
]);
1407 alpha
= Math
.max(alpha
, v
);
1408 if (alpha
>= beta
) break; //beta cutoff
1413 for (let i
= 0; i
< moves
.length
; i
++) {
1414 this.play(moves
[i
]);
1415 v
= Math
.min(v
, this.alphabeta(depth
- 1, alpha
, beta
));
1416 this.undo(moves
[i
]);
1417 beta
= Math
.min(beta
, v
);
1418 if (alpha
>= beta
) break; //alpha cutoff
1426 // Just count material for now
1427 for (let i
= 0; i
< V
.size
.x
; i
++) {
1428 for (let j
= 0; j
< V
.size
.y
; j
++) {
1429 if (this.board
[i
][j
] != V
.EMPTY
) {
1430 const sign
= this.getColor(i
, j
) == "w" ? 1 : -1;
1431 evaluation
+= sign
* V
.VALUES
[this.getPiece(i
, j
)];
1438 /////////////////////////
1439 // MOVES + GAME NOTATION
1440 /////////////////////////
1442 // Context: just before move is played, turn hasn't changed
1443 // TODO: un-ambiguous notation (switch on piece type, check directions...)
1445 if (move.appear
.length
== 2 && move.appear
[0].p
== V
.KING
)
1447 return move.end
.y
< move.start
.y
? "0-0-0" : "0-0";
1449 // Translate final square
1450 const finalSquare
= V
.CoordsToSquare(move.end
);
1452 const piece
= this.getPiece(move.start
.x
, move.start
.y
);
1453 if (piece
== V
.PAWN
) {
1456 if (move.vanish
.length
> move.appear
.length
) {
1458 const startColumn
= V
.CoordToColumn(move.start
.y
);
1459 notation
= startColumn
+ "x" + finalSquare
;
1461 else notation
= finalSquare
;
1462 if (move.appear
.length
> 0 && move.appear
[0].p
!= V
.PAWN
)
1464 notation
+= "=" + move.appear
[0].p
.toUpperCase();
1469 piece
.toUpperCase() +
1470 (move.vanish
.length
> move.appear
.length
? "x" : "") +
1475 static GetUnambiguousNotation(move) {
1476 // Machine-readable format with all the informations about the move
1478 (!!move.start
&& V
.OnBoard(move.start
.x
, move.start
.y
)
1479 ? V
.CoordsToSquare(move.start
)
1482 (!!move.end
&& V
.OnBoard(move.end
.x
, move.end
.y
)
1483 ? V
.CoordsToSquare(move.end
)
1486 (!!move.appear
&& move.appear
.length
> 0
1487 ? move.appear
.map(a
=>
1488 a
.c
+ a
.p
+ V
.CoordsToSquare({ x: a
.x
, y: a
.y
})).join(".")
1491 (!!move.vanish
&& move.vanish
.length
> 0
1492 ? move.vanish
.map(a
=>
1493 a
.c
+ a
.p
+ V
.CoordsToSquare({ x: a
.x
, y: a
.y
})).join(".")