client/src/variants/Doublemove2.js

   1 import { ChessRules } from "@/base_rules";
   2 import { randInt } from "@/utils/alea";
   3
   4 export class Doublemove2Rules 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   // There may be 2 enPassant squares (if 2 pawns jump 2 squares in same turn)
  18   getEnpassantFen() {
  19     return this.epSquares[this.epSquares.length - 1].map(
  20       epsq => epsq === undefined
  21         ? "-" //no en-passant
  22         : V.CoordsToSquare(epsq)
  23     ).join(",");
  24   }
  25
  26   setOtherVariables(fen) {
  27     const parsedFen = V.ParseFen(fen);
  28     this.setFlags(parsedFen.flags);
  29     this.epSquares = [parsedFen.enpassant.split(",").map(sq => {
  30       if (sq != "-") return V.SquareToCoords(sq);
  31       return undefined;
  32     })];
  33     this.scanKings(fen);
  34     // Extract subTurn from turn indicator: "w" (first move), or
  35     // "w1" or "w2" white subturn 1 or 2, and same for black
  36     this.turn = parsedFen.turn;
  37     this.subTurn = 1;
  38   }
  39
  40   getEnpassantCaptures([x, y], shiftX) {
  41     let moves = [];
  42     // En passant: always OK if subturn 1,
  43     // OK on subturn 2 only if enPassant was played at subturn 1
  44     // (and if there are two e.p. squares available).
  45     const Lep = this.epSquares.length;
  46     const epSquares = this.epSquares[Lep - 1]; //always at least one element
  47     let epSqs = [];
  48     epSquares.forEach(sq => {
  49       if (sq) epSqs.push(sq);
  50     });
  51     if (epSqs.length == 0) return moves;
  52     const oppCol = V.GetOppCol(this.getColor(x, y));
  53     for (let sq of epSqs) {
  54       if (
  55         this.subTurn == 1 ||
  56         (epSqs.length == 2 &&
  57           // Was this en-passant capture already played at subturn 1 ?
  58           // (Or maybe the opponent filled the en-passant square with a piece)
  59           this.board[epSqs[0].x][epSqs[0].y] != V.EMPTY)
  60       ) {
  61         if (
  62           sq.x == x + shiftX &&
  63           Math.abs(sq.y - y) == 1 &&
  64           // Add condition "enemy pawn must be present"
  65           this.getPiece(x, sq.y) == V.PAWN &&
  66           this.getColor(x, sq.y) == oppCol
  67         ) {
  68           let epMove = this.getBasicMove([x, y], [sq.x, sq.y]);
  69           epMove.vanish.push({
  70             x: x,
  71             y: sq.y,
  72             p: "p",
  73             c: oppCol
  74           });
  75           moves.push(epMove);
  76         }
  77       }
  78     }
  79     return moves;
  80   }
  81
  82   isAttacked(sq, color, castling) {
  83     const singleMoveAttack = super.isAttacked(sq, color);
  84     if (singleMoveAttack) return true;
  85     if (!!castling) {
  86       if (this.subTurn == 1)
  87         // Castling at move 1 could be done into check
  88         return false;
  89       return singleMoveAttack;
  90     }
  91     // Double-move allowed:
  92     const curTurn = this.turn;
  93     this.turn = color;
  94     const moves1 = super.getAllPotentialMoves();
  95     this.turn = curTurn;
  96     for (let move of moves1) {
  97       this.play(move);
  98       const res = super.isAttacked(sq, color);
  99       this.undo(move);
 100       if (res) return res;
 101     }
 102     return false;
 103   }
 104
 105   filterValid(moves) {
 106     if (this.subTurn == 1) {
 107       return moves.filter(m1 => {
 108         this.play(m1);
 109         // NOTE: no recursion because next call will see subTurn == 2
 110         const res = super.atLeastOneMove();
 111         this.undo(m1);
 112         return res;
 113       });
 114     }
 115     return super.filterValid(moves);
 116   }
 117
 118   play(move) {
 119     move.flags = JSON.stringify(this.aggregateFlags());
 120     V.PlayOnBoard(this.board, move);
 121     const epSq = this.getEpSquare(move);
 122     if (this.subTurn == 2) {
 123       let lastEpsq = this.epSquares[this.epSquares.length - 1];
 124       lastEpsq.push(epSq);
 125       this.turn = V.GetOppCol(this.turn);
 126     }
 127     else {
 128       this.epSquares.push([epSq]);
 129       this.movesCount++;
 130       if (this.movesCount == 1) this.turn = "b";
 131     }
 132     if (this.movesCount > 1) this.subTurn = 3 - this.subTurn;
 133     this.postPlay(move);
 134   }
 135
 136   postPlay(move) {
 137     const c = move.vanish[0].c;
 138     const piece = move.vanish[0].p;
 139     const firstRank = c == "w" ? V.size.x - 1 : 0;
 140
 141     if (piece == V.KING && move.appear.length > 0) {
 142       this.kingPos[c][0] = move.appear[0].x;
 143       this.kingPos[c][1] = move.appear[0].y;
 144       this.castleFlags[c] = [V.size.y, V.size.y];
 145       return;
 146     }
 147     const oppCol = V.GetOppCol(c);
 148     const oppFirstRank = V.size.x - 1 - firstRank;
 149     if (
 150       move.start.x == firstRank && //our rook moves?
 151       this.castleFlags[c].includes(move.start.y)
 152     ) {
 153       const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
 154       this.castleFlags[c][flagIdx] = V.size.y;
 155     } else if (
 156       move.end.x == oppFirstRank && //we took opponent rook?
 157       this.castleFlags[oppCol].includes(move.end.y)
 158     ) {
 159       const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
 160       this.castleFlags[oppCol][flagIdx] = V.size.y;
 161     }
 162   }
 163
 164   undo(move) {
 165     this.disaggregateFlags(JSON.parse(move.flags));
 166     V.UndoOnBoard(this.board, move);
 167     if (this.subTurn == 2 || this.movesCount == 1) {
 168       this.epSquares.pop();
 169       this.movesCount--;
 170       if (this.movesCount == 0) this.turn = "w";
 171     }
 172     else {
 173       let lastEpsq = this.epSquares[this.epSquares.length - 1];
 174       lastEpsq.pop();
 175       this.turn = V.GetOppCol(this.turn);
 176     }
 177     if (this.movesCount > 0) this.subTurn = 3 - this.subTurn;
 178     super.postUndo(move);
 179   }
 180
 181   static get VALUES() {
 182     return {
 183       p: 1,
 184       r: 5,
 185       n: 3,
 186       b: 3,
 187       q: 7, //slightly less than in orthodox game
 188       k: 1000
 189     };
 190   }
 191
 192   // No alpha-beta here, just adapted min-max at depth 1(+1)
 193   getComputerMove() {
 194     const color = this.turn;
 195     const moves11 = this.getAllValidMoves();
 196     if (this.movesCount == 0)
 197       // First white move at random:
 198       return moves11[randInt(moves11.length)];
 199
 200     let doubleMoves = [];
 201     // Rank moves using a min-max at depth 2
 202     for (let i = 0; i < moves11.length; i++) {
 203       this.play(moves11[i]);
 204       const moves12 = this.getAllValidMoves();
 205       for (let j = 0; j < moves12.length; j++) {
 206         this.play(moves12[j]);
 207         doubleMoves.push({
 208           moves: [moves11[i], moves12[j]],
 209           eval: this.evalPosition()
 210         });
 211         this.undo(moves12[j]);
 212       }
 213       this.undo(moves11[i]);
 214     }
 215
 216     doubleMoves.sort((a, b) => {
 217       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
 218     });
 219     let candidates = [0]; //indices of candidates moves
 220     for (
 221       let i = 1;
 222       i < doubleMoves.length && doubleMoves[i].eval == doubleMoves[0].eval;
 223       i++
 224     ) {
 225       candidates.push(i);
 226     }
 227     return doubleMoves[randInt(candidates.length)].moves;
 228   }
 229 };