client/src/variants/Marseille.js

   1 import { ChessRules } from "@/base_rules";
   2 import { randInt } from "@/utils/alea";
   3
   4 export class MarseilleRules extends ChessRules {
   5   static IsGoodEnpassant(enpassant) {
   6     const squares = enpassant.split(",");
   7     if (squares.length > 2) return false;
   8     for (let sq of squares) {
   9       if (sq != "-") {
  10         const ep = V.SquareToCoords(sq);
  11         if (isNaN(ep.x) || !V.OnBoard(ep)) return false;
  12       }
  13     }
  14     return true;
  15   }
  16
  17   getTurnFen() {
  18     return this.turn + this.subTurn;
  19   }
  20
  21   // There may be 2 enPassant squares (if 2 pawns jump 2 squares in same turn)
  22   getEnpassantFen() {
  23     return this.epSquares[this.epSquares.length - 1].map(
  24       epsq => epsq === undefined
  25         ? "-" //no en-passant
  26         : V.CoordsToSquare(epsq)
  27     ).join(",");
  28   }
  29
  30   setOtherVariables(fen) {
  31     const parsedFen = V.ParseFen(fen);
  32     this.setFlags(parsedFen.flags);
  33     this.epSquares = [parsedFen.enpassant.split(",").map(sq => {
  34       if (sq != "-") return V.SquareToCoords(sq);
  35       return undefined;
  36     })];
  37     this.scanKings(fen);
  38     // Extract subTurn from turn indicator: "w" (first move), or
  39     // "w1" or "w2" white subturn 1 or 2, and same for black
  40     const fullTurn = V.ParseFen(fen).turn;
  41     this.turn = fullTurn[0];
  42     // At move 1, the subTurn doesn't need to be specified:
  43     this.subTurn = fullTurn[1] || 1;
  44   }
  45
  46   getEnpassantCaptures([x, y], shiftX) {
  47     let moves = [];
  48     // En passant: always OK if subturn 1,
  49     // OK on subturn 2 only if enPassant was played at subturn 1
  50     // (and if there are two e.p. squares available).
  51     const Lep = this.epSquares.length;
  52     const epSquares = this.epSquares[Lep - 1]; //always at least one element
  53     let epSqs = [];
  54     epSquares.forEach(sq => {
  55       if (sq) epSqs.push(sq);
  56     });
  57     if (epSqs.length == 0) return moves;
  58     const oppCol = V.GetOppCol(this.getColor(x, y));
  59     for (let sq of epSqs) {
  60       if (
  61         this.subTurn == 1 ||
  62         (epSqs.length == 2 &&
  63           // Was this en-passant capture already played at subturn 1 ?
  64           // (Or maybe the opponent filled the en-passant square with a piece)
  65           this.board[epSqs[0].x][epSqs[0].y] != V.EMPTY)
  66       ) {
  67         if (
  68           sq.x == x + shiftX &&
  69           Math.abs(sq.y - y) == 1 &&
  70           // Add condition "enemy pawn must be present"
  71           this.getPiece(x, sq.y) == V.PAWN &&
  72           this.getColor(x, sq.y) == oppCol
  73         ) {
  74           let epMove = this.getBasicMove([x, y], [sq.x, sq.y]);
  75           epMove.vanish.push({
  76             x: x,
  77             y: sq.y,
  78             p: "p",
  79             c: oppCol
  80           });
  81           moves.push(epMove);
  82         }
  83       }
  84     }
  85     return moves;
  86   }
  87
  88   play(move) {
  89     move.flags = JSON.stringify(this.aggregateFlags());
  90     move.turn = this.turn + this.subTurn;
  91     V.PlayOnBoard(this.board, move);
  92     const epSq = this.getEpSquare(move);
  93     if (this.movesCount == 0) {
  94       // First move in game
  95       this.turn = "b";
  96       this.epSquares.push([epSq]);
  97       this.movesCount = 1;
  98     }
  99     // Does this move give check on subturn 1? If yes, skip subturn 2
 100     else if (this.subTurn == 1 && this.underCheck(V.GetOppCol(this.turn))) {
 101       this.turn = V.GetOppCol(this.turn);
 102       this.epSquares.push([epSq]);
 103       move.checkOnSubturn1 = true;
 104       this.movesCount++;
 105     } else {
 106       if (this.subTurn == 2) {
 107         this.turn = V.GetOppCol(this.turn);
 108         let lastEpsq = this.epSquares[this.epSquares.length - 1];
 109         lastEpsq.push(epSq);
 110       } else {
 111         this.epSquares.push([epSq]);
 112         this.movesCount++;
 113       }
 114       this.subTurn = 3 - this.subTurn;
 115     }
 116     this.postPlay(move);
 117   }
 118
 119   postPlay(move) {
 120     const c = move.turn.charAt(0);
 121     const piece = move.vanish[0].p;
 122     const firstRank = c == "w" ? V.size.x - 1 : 0;
 123
 124     if (piece == V.KING && move.appear.length > 0) {
 125       this.kingPos[c][0] = move.appear[0].x;
 126       this.kingPos[c][1] = move.appear[0].y;
 127       if (V.HasCastle) this.castleFlags[c] = [V.size.y, V.size.y];
 128       return;
 129     }
 130     const oppCol = V.GetOppCol(c);
 131     const oppFirstRank = V.size.x - 1 - firstRank;
 132     if (
 133       move.start.x == firstRank && //our rook moves?
 134       this.castleFlags[c].includes(move.start.y)
 135     ) {
 136       const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
 137       this.castleFlags[c][flagIdx] = V.size.y;
 138     } else if (
 139       move.end.x == oppFirstRank && //we took opponent rook?
 140       this.castleFlags[oppCol].includes(move.end.y)
 141     ) {
 142       const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
 143       this.castleFlags[oppCol][flagIdx] = V.size.y;
 144     }
 145   }
 146
 147   undo(move) {
 148     this.disaggregateFlags(JSON.parse(move.flags));
 149     V.UndoOnBoard(this.board, move);
 150     if (this.movesCount == 1 || !!move.checkOnSubturn1 || this.subTurn == 2) {
 151       // The move may not be full, but is fully undone:
 152       this.epSquares.pop();
 153       // Moves counter was just incremented:
 154       this.movesCount--;
 155     } else {
 156       // Undo the second half of a move
 157       let lastEpsq = this.epSquares[this.epSquares.length - 1];
 158       lastEpsq.pop();
 159     }
 160     this.turn = move.turn[0];
 161     this.subTurn = parseInt(move.turn[1]);
 162     super.postUndo(move);
 163   }
 164
 165   // NOTE:  GenRandInitFen() is OK,
 166   // since at first move turn indicator is just "w"
 167
 168   static get VALUES() {
 169     return {
 170       p: 1,
 171       r: 5,
 172       n: 3,
 173       b: 3,
 174       q: 7, //slightly less than in orthodox game
 175       k: 1000
 176     };
 177   }
 178
 179   // No alpha-beta here, just adapted min-max at depth 2(+1)
 180   getComputerMove() {
 181     const maxeval = V.INFINITY;
 182     const color = this.turn;
 183     const oppCol = V.GetOppCol(this.turn);
 184
 185     // Search best (half) move for opponent turn
 186     const getBestMoveEval = () => {
 187       let score = this.getCurrentScore();
 188       if (score != "*") {
 189         if (score == "1/2") return 0;
 190         return maxeval * (score == "1-0" ? 1 : -1);
 191       }
 192       let moves = this.getAllValidMoves();
 193       let res = oppCol == "w" ? -maxeval : maxeval;
 194       for (let m of moves) {
 195         this.play(m);
 196         score = this.getCurrentScore();
 197         // Now turn is oppCol,2 if m doesn't give check
 198         // Otherwise it's color,1. In both cases the next test makes sense
 199         if (score != "*") {
 200           if (score == "1/2")
 201             res = oppCol == "w" ? Math.max(res, 0) : Math.min(res, 0);
 202           else {
 203             // Found a mate
 204             this.undo(m);
 205             return maxeval * (score == "1-0" ? 1 : -1);
 206           }
 207         }
 208         const evalPos = this.evalPosition();
 209         res = oppCol == "w" ? Math.max(res, evalPos) : Math.min(res, evalPos);
 210         this.undo(m);
 211       }
 212       return res;
 213     };
 214
 215     let moves11 = this.getAllValidMoves();
 216     let doubleMoves = [];
 217     // Rank moves using a min-max at depth 2
 218     for (let i = 0; i < moves11.length; i++) {
 219       this.play(moves11[i]);
 220       if (this.turn != color) {
 221         // We gave check with last move: search the best opponent move
 222         doubleMoves.push({ moves: [moves11[i]], eval: getBestMoveEval() });
 223       } else {
 224         let moves12 = this.getAllValidMoves();
 225         for (let j = 0; j < moves12.length; j++) {
 226           this.play(moves12[j]);
 227           doubleMoves.push({
 228             moves: [moves11[i], moves12[j]],
 229             eval: getBestMoveEval()
 230           });
 231           this.undo(moves12[j]);
 232         }
 233       }
 234       this.undo(moves11[i]);
 235     }
 236
 237     doubleMoves.sort((a, b) => {
 238       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
 239     });
 240     let candidates = [0]; //indices of candidates moves
 241     for (
 242       let i = 1;
 243       i < doubleMoves.length && doubleMoves[i].eval == doubleMoves[0].eval;
 244       i++
 245     ) {
 246       candidates.push(i);
 247     }
 248
 249     const selected = doubleMoves[randInt(candidates.length)].moves;
 250     if (selected.length == 1) return selected[0];
 251     return selected;
 252   }
 253 };