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[vchess.git] / client / src / variants / Berolina.js
1 import { ChessRules } from "@/base_rules";
2
3 export const VariantRules = class BerolinaRules extends ChessRules {
4 // En-passant after 2-sq jump
5 getEpSquare(moveOrSquare) {
6 if (!moveOrSquare) return undefined;
7 if (typeof moveOrSquare === "string") {
8 const square = moveOrSquare;
9 if (square == "-") return undefined;
10 // Enemy pawn initial column must be given too:
11 let res = [];
12 const epParts = square.split(",");
13 res.push(V.SquareToCoords(epParts[0]));
14 res.push(V.ColumnToCoord(epParts[1]));
15 return res;
16 }
17 // Argument is a move:
18 const move = moveOrSquare;
19 const [sx, ex, sy] = [move.start.x, move.end.x, move.start.y];
20 if (this.getPiece(sx, sy) == V.PAWN && Math.abs(sx - ex) == 2) {
21 return [
22 {
23 x: (ex + sx) / 2,
24 y: (move.end.y + sy) / 2
25 },
26 // The arrival column must be remembered, because
27 // potentially two pawns could be candidates to be captured:
28 // one on our left, and one on our right.
29 move.end.y
30 ];
31 }
32 return undefined; //default
33 }
34
35 static IsGoodEnpassant(enpassant) {
36 if (enpassant != "-") {
37 const epParts = enpassant.split(",");
38 const epSq = V.SquareToCoords(epParts[0]);
39 if (isNaN(epSq.x) || isNaN(epSq.y) || !V.OnBoard(epSq)) return false;
40 const arrCol = V.ColumnToCoord(epParts[1]);
41 if (isNaN(arrCol) || arrCol < 0 || arrCol >= V.size.y) return false;
42 }
43 return true;
44 }
45
46 getEnpassantFen() {
47 const L = this.epSquares.length;
48 if (!this.epSquares[L - 1]) return "-"; //no en-passant
49 return (
50 V.CoordsToSquare(this.epSquares[L - 1][0]) +
51 "," +
52 V.CoordToColumn(this.epSquares[L - 1][1])
53 );
54 }
55
56 // Special pawns movements
57 getPotentialPawnMoves([x, y]) {
58 const color = this.turn;
59 let moves = [];
60 const [sizeX, sizeY] = [V.size.x, V.size.y];
61 const shiftX = color == "w" ? -1 : 1;
62 const startRank = color == "w" ? sizeX - 2 : 1;
63 const lastRank = color == "w" ? 0 : sizeX - 1;
64 const finalPieces =
65 x + shiftX == lastRank ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN] : [V.PAWN];
66
67 // One square diagonally
68 for (let shiftY of [-1, 1]) {
69 if (this.board[x + shiftX][y + shiftY] == V.EMPTY) {
70 for (let piece of finalPieces) {
71 moves.push(
72 this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
73 c: color,
74 p: piece
75 })
76 );
77 }
78 if (
79 x == startRank &&
80 y + 2 * shiftY >= 0 &&
81 y + 2 * shiftY < sizeY &&
82 this.board[x + 2 * shiftX][y + 2 * shiftY] == V.EMPTY
83 ) {
84 // Two squares jump
85 moves.push(
86 this.getBasicMove([x, y], [x + 2 * shiftX, y + 2 * shiftY])
87 );
88 }
89 }
90 }
91 // Capture
92 if (
93 this.board[x + shiftX][y] != V.EMPTY &&
94 this.canTake([x, y], [x + shiftX, y])
95 ) {
96 for (let piece of finalPieces)
97 moves.push(
98 this.getBasicMove([x, y], [x + shiftX, y], { c: color, p: piece })
99 );
100 }
101
102 // En passant
103 const Lep = this.epSquares.length;
104 const epSquare = this.epSquares[Lep - 1]; //always at least one element
105 if (
106 !!epSquare &&
107 epSquare[0].x == x + shiftX &&
108 epSquare[0].y == y
109 ) {
110 let enpassantMove = this.getBasicMove([x, y], [x + shiftX, y]);
111 enpassantMove.vanish.push({
112 x: x,
113 y: epSquare[1],
114 p: "p",
115 c: this.getColor(x, epSquare[1])
116 });
117 moves.push(enpassantMove);
118 }
119
120 return moves;
121 }
122
123 isAttackedByPawn([x, y], colors) {
124 for (let c of colors) {
125 let pawnShift = c == "w" ? 1 : -1;
126 if (x + pawnShift >= 0 && x + pawnShift < V.size.x) {
127 if (
128 this.getPiece(x + pawnShift, y) == V.PAWN &&
129 this.getColor(x + pawnShift, y) == c
130 ) {
131 return true;
132 }
133 }
134 }
135 return false;
136 }
137
138 getNotation(move) {
139 const piece = this.getPiece(move.start.x, move.start.y);
140 if (piece == V.PAWN) {
141 // Pawn move
142 const finalSquare = V.CoordsToSquare(move.end);
143 let notation = "";
144 if (move.vanish.length == 2)
145 //capture
146 notation = "Px" + finalSquare;
147 else {
148 // No capture: indicate the initial square for potential ambiguity
149 const startSquare = V.CoordsToSquare(move.start);
150 notation = startSquare + finalSquare;
151 }
152 if (move.appear[0].p != V.PAWN)
153 //promotion
154 notation += "=" + move.appear[0].p.toUpperCase();
155 return notation;
156 }
157 return super.getNotation(move); //all other pieces are orthodox
158 }
159 };