client/src/variants/Doublemove1.js

   1 import { ChessRules } from "@/base_rules";
   2 import { randInt } from "@/utils/alea";
   3
   4 export class Doublemove1Rules 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     this.turn = parsedFen.turn;
  35     this.subTurn = 1;
  36   }
  37
  38   getEnpassantCaptures([x, y], shiftX) {
  39     let moves = [];
  40     // En passant: always OK if subturn 1,
  41     // OK on subturn 2 only if enPassant was played at subturn 1
  42     // (and if there are two e.p. squares available).
  43     const Lep = this.epSquares.length;
  44     const epSquares = this.epSquares[Lep - 1]; //always at least one element
  45     let epSqs = [];
  46     epSquares.forEach(sq => {
  47       if (sq) epSqs.push(sq);
  48     });
  49     if (epSqs.length == 0) return moves;
  50     const oppCol = V.GetOppCol(this.getColor(x, y));
  51     for (let sq of epSqs) {
  52       if (
  53         this.subTurn == 1 ||
  54         (epSqs.length == 2 &&
  55           // Was this en-passant capture already played at subturn 1 ?
  56           // (Or maybe the opponent filled the en-passant square with a piece)
  57           this.board[epSqs[0].x][epSqs[0].y] != V.EMPTY)
  58       ) {
  59         if (
  60           sq.x == x + shiftX &&
  61           Math.abs(sq.y - y) == 1 &&
  62           // Add condition "enemy pawn must be present"
  63           this.getPiece(x, sq.y) == V.PAWN &&
  64           this.getColor(x, sq.y) == oppCol
  65         ) {
  66           let epMove = this.getBasicMove([x, y], [sq.x, sq.y]);
  67           epMove.vanish.push({
  68             x: x,
  69             y: sq.y,
  70             p: "p",
  71             c: oppCol
  72           });
  73           moves.push(epMove);
  74         }
  75       }
  76     }
  77     return moves;
  78   }
  79
  80   play(move) {
  81     move.flags = JSON.stringify(this.aggregateFlags());
  82     move.turn = this.turn + this.subTurn;
  83     V.PlayOnBoard(this.board, move);
  84     const epSq = this.getEpSquare(move);
  85     if (this.movesCount == 0) {
  86       // First move in game
  87       this.turn = "b";
  88       this.epSquares.push([epSq]);
  89       this.movesCount = 1;
  90     }
  91     // Does this move give check on subturn 1? If yes, skip subturn 2
  92     else if (this.subTurn == 1 && this.underCheck(V.GetOppCol(this.turn))) {
  93       this.turn = V.GetOppCol(this.turn);
  94       this.epSquares.push([epSq]);
  95       move.checkOnSubturn1 = true;
  96       this.movesCount++;
  97     } else {
  98       if (this.subTurn == 2) {
  99         this.turn = V.GetOppCol(this.turn);
 100         let lastEpsq = this.epSquares[this.epSquares.length - 1];
 101         lastEpsq.push(epSq);
 102       } else {
 103         this.epSquares.push([epSq]);
 104         this.movesCount++;
 105       }
 106       this.subTurn = 3 - this.subTurn;
 107     }
 108     this.postPlay(move);
 109   }
 110
 111   postPlay(move) {
 112     const c = move.turn.charAt(0);
 113     const piece = move.vanish[0].p;
 114     const firstRank = c == "w" ? V.size.x - 1 : 0;
 115
 116     if (piece == V.KING && move.appear.length > 0) {
 117       this.kingPos[c][0] = move.appear[0].x;
 118       this.kingPos[c][1] = move.appear[0].y;
 119       this.castleFlags[c] = [V.size.y, V.size.y];
 120       return;
 121     }
 122     const oppCol = V.GetOppCol(c);
 123     const oppFirstRank = V.size.x - 1 - firstRank;
 124     if (
 125       move.start.x == firstRank && //our rook moves?
 126       this.castleFlags[c].includes(move.start.y)
 127     ) {
 128       const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
 129       this.castleFlags[c][flagIdx] = V.size.y;
 130     } else if (
 131       move.end.x == oppFirstRank && //we took opponent rook?
 132       this.castleFlags[oppCol].includes(move.end.y)
 133     ) {
 134       const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
 135       this.castleFlags[oppCol][flagIdx] = V.size.y;
 136     }
 137   }
 138
 139   undo(move) {
 140     this.disaggregateFlags(JSON.parse(move.flags));
 141     V.UndoOnBoard(this.board, move);
 142     if (this.movesCount == 1 || !!move.checkOnSubturn1 || this.subTurn == 2) {
 143       // The move may not be full, but is fully undone:
 144       this.epSquares.pop();
 145       // Moves counter was just incremented:
 146       this.movesCount--;
 147     } else {
 148       // Undo the second half of a move
 149       let lastEpsq = this.epSquares[this.epSquares.length - 1];
 150       lastEpsq.pop();
 151     }
 152     this.turn = move.turn[0];
 153     this.subTurn = parseInt(move.turn[1]);
 154     super.postUndo(move);
 155   }
 156
 157   static get VALUES() {
 158     return {
 159       p: 1,
 160       r: 5,
 161       n: 3,
 162       b: 3,
 163       q: 7, //slightly less than in orthodox game
 164       k: 1000
 165     };
 166   }
 167
 168   // No alpha-beta here, just adapted min-max at depth 2(+1)
 169   getComputerMove() {
 170     const maxeval = V.INFINITY;
 171     const color = this.turn;
 172     const oppCol = V.GetOppCol(this.turn);
 173
 174     // Search best (half) move for opponent turn
 175     const getBestMoveEval = () => {
 176       let score = this.getCurrentScore();
 177       if (score != "*") {
 178         if (score == "1/2") return 0;
 179         return maxeval * (score == "1-0" ? 1 : -1);
 180       }
 181       let moves = this.getAllValidMoves();
 182       let res = oppCol == "w" ? -maxeval : maxeval;
 183       for (let m of moves) {
 184         this.play(m);
 185         score = this.getCurrentScore();
 186         // Now turn is oppCol,2 if m doesn't give check
 187         // Otherwise it's color,1. In both cases the next test makes sense
 188         if (score != "*") {
 189           if (score == "1/2")
 190             res = oppCol == "w" ? Math.max(res, 0) : Math.min(res, 0);
 191           else {
 192             // Found a mate
 193             this.undo(m);
 194             return maxeval * (score == "1-0" ? 1 : -1);
 195           }
 196         }
 197         const evalPos = this.evalPosition();
 198         res = oppCol == "w" ? Math.max(res, evalPos) : Math.min(res, evalPos);
 199         this.undo(m);
 200       }
 201       return res;
 202     };
 203
 204     let moves11 = this.getAllValidMoves();
 205     let doubleMoves = [];
 206     // Rank moves using a min-max at depth 2
 207     for (let i = 0; i < moves11.length; i++) {
 208       this.play(moves11[i]);
 209       if (this.turn != color) {
 210         // We gave check with last move: search the best opponent move
 211         doubleMoves.push({ moves: [moves11[i]], eval: getBestMoveEval() });
 212       } else {
 213         let moves12 = this.getAllValidMoves();
 214         for (let j = 0; j < moves12.length; j++) {
 215           this.play(moves12[j]);
 216           doubleMoves.push({
 217             moves: [moves11[i], moves12[j]],
 218             eval: getBestMoveEval()
 219           });
 220           this.undo(moves12[j]);
 221         }
 222       }
 223       this.undo(moves11[i]);
 224     }
 225
 226     doubleMoves.sort((a, b) => {
 227       return (color == "w" ? 1 : -1) * (b.eval - a.eval);
 228     });
 229     let candidates = [0]; //indices of candidates moves
 230     for (
 231       let i = 1;
 232       i < doubleMoves.length && doubleMoves[i].eval == doubleMoves[0].eval;
 233       i++
 234     ) {
 235       candidates.push(i);
 236     }
 237
 238     const selected = doubleMoves[randInt(candidates.length)].moves;
 239     if (selected.length == 1) return selected[0];
 240     return selected;
 241   }
 242 };