client/src/variants/Marseille.js

   1 import { ChessRules } from "@/base_rules";
   2
   3 export const VariantRules = class MarseilleRules extends ChessRules
   4 {
   5     static IsGoodEnpassant(enpassant)
   6     {
   7         if (enpassant != "-")
   8         {
   9             const squares = enpassant.split(",");
  10             if (squares.length > 2)
  11                 return false;
  12             for (let sq of squares)
  13             {
  14                 const ep = V.SquareToCoords(sq);
  15                 if (isNaN(ep.x) || !V.OnBoard(ep))
  16                     return false;
  17             }
  18         }
  19         return true;
  20     }
  21
  22     getTurnFen()
  23     {
  24         return this.turn + this.subTurn;
  25     }
  26
  27     // There may be 2 enPassant squares (if 2 pawns jump 2 squares in same turn)
  28     getEnpassantFen()
  29     {
  30         const L = this.epSquares.length;
  31         if (this.epSquares[L-1].every(epsq => epsq === undefined))
  32             return "-"; //no en-passant
  33         let res = "";
  34         this.epSquares[L-1].forEach(epsq => {
  35             if (!!epsq)
  36                 res += V.CoordsToSquare(epsq) + ",";
  37         });
  38         return res.slice(0,-1); //remove last comma
  39     }
  40
  41     setOtherVariables(fen)
  42     {
  43         const parsedFen = V.ParseFen(fen);
  44         this.setFlags(parsedFen.flags);
  45         if (parsedFen.enpassant == "-")
  46             this.epSquares = [ [undefined] ];
  47         else
  48         {
  49             let res = [];
  50             const squares = parsedFen.enpassant.split(",");
  51             for (let sq of squares)
  52                 res.push(V.SquareToCoords(sq));
  53             this.epSquares = [ res ];
  54         }
  55         this.scanKingsRooks(fen);
  56         // Extract subTurn from turn indicator: "w" (first move), or
  57         // "w1" or "w2" white subturn 1 or 2, and same for black
  58         const fullTurn = V.ParseFen(fen).turn;
  59         this.turn = fullTurn[0];
  60         this.subTurn = (fullTurn[1] || 0); //"w0" = special code for first move in game
  61     }
  62
  63     getPotentialPawnMoves([x,y])
  64     {
  65         const color = this.turn;
  66         let moves = [];
  67         const [sizeX,sizeY] = [V.size.x,V.size.y];
  68         const shiftX = (color == "w" ? -1 : 1);
  69         const firstRank = (color == 'w' ? sizeX-1 : 0);
  70         const startRank = (color == "w" ? sizeX-2 : 1);
  71         const lastRank = (color == "w" ? 0 : sizeX-1);
  72         const finalPieces = x + shiftX == lastRank
  73             ? [V.ROOK,V.KNIGHT,V.BISHOP,V.QUEEN]
  74             : [V.PAWN];
  75
  76         // One square forward
  77         if (this.board[x+shiftX][y] == V.EMPTY)
  78         {
  79             for (let piece of finalPieces)
  80             {
  81                 moves.push(this.getBasicMove([x,y], [x+shiftX,y],
  82                     {c:color,p:piece}));
  83             }
  84             // Next condition because pawns on 1st rank can generally jump
  85             if ([startRank,firstRank].includes(x)
  86                 && this.board[x+2*shiftX][y] == V.EMPTY)
  87             {
  88                 // Two squares jump
  89                 moves.push(this.getBasicMove([x,y], [x+2*shiftX,y]));
  90             }
  91         }
  92         // Captures
  93         for (let shiftY of [-1,1])
  94         {
  95             if (y + shiftY >= 0 && y + shiftY < sizeY
  96                 && this.board[x+shiftX][y+shiftY] != V.EMPTY
  97                 && this.canTake([x,y], [x+shiftX,y+shiftY]))
  98             {
  99                 for (let piece of finalPieces)
 100                 {
 101                     moves.push(this.getBasicMove([x,y], [x+shiftX,y+shiftY],
 102                         {c:color,p:piece}));
 103                 }
 104             }
 105         }
 106
 107         // En passant: always OK if subturn 1,
 108         // OK on subturn 2 only if enPassant was played at subturn 1
 109         // (and if there are two e.p. squares available).
 110         const Lep = this.epSquares.length;
 111         const epSquares = this.epSquares[Lep-1]; //always at least one element
 112         let epSqs = [];
 113         epSquares.forEach(sq => {
 114             if (!!sq)
 115                 epSqs.push(sq);
 116         });
 117         if (epSqs.length == 0)
 118             return moves;
 119         const oppCol = V.GetOppCol(color);
 120         for (let sq of epSqs)
 121         {
 122             if (this.subTurn == 1 || (epSqs.length == 2 &&
 123                 // Was this en-passant capture already played at subturn 1 ?
 124                 // (Or maybe the opponent filled the en-passant square with a piece)
 125                 this.board[epSqs[0].x][epSqs[0].y] != V.EMPTY))
 126             {
 127                 if (sq.x == x+shiftX && Math.abs(sq.y - y) == 1
 128                     // Add condition "enemy pawn must be present"
 129                     && this.getPiece(x,sq.y) == V.PAWN && this.getColor(x,sq.y) == oppCol)
 130                 {
 131                     let epMove = this.getBasicMove([x,y], [sq.x,sq.y]);
 132                     epMove.vanish.push({
 133                         x: x,
 134                         y: sq.y,
 135                         p: 'p',
 136                         c: oppCol
 137                     });
 138                     moves.push(epMove);
 139                 }
 140             }
 141         }
 142
 143         return moves;
 144     }
 145
 146     play(move)
 147     {
 148         move.flags = JSON.stringify(this.aggregateFlags());
 149         move.turn = this.turn + this.subTurn;
 150         V.PlayOnBoard(this.board, move);
 151         const epSq = this.getEpSquare(move);
 152         if (this.subTurn == 0) //first move in game
 153         {
 154             this.turn = "b";
 155       this.subTurn = 1;
 156             this.epSquares.push([epSq]);
 157         }
 158         // Does this move give check on subturn 1? If yes, skip subturn 2
 159         else if (this.subTurn==1 && this.underCheck(V.GetOppCol(this.turn)))
 160         {
 161             this.turn = V.GetOppCol(this.turn);
 162             this.epSquares.push([epSq]);
 163             move.checkOnSubturn1 = true;
 164         }
 165         else
 166         {
 167             if (this.subTurn == 2)
 168             {
 169                 this.turn = V.GetOppCol(this.turn);
 170                 let lastEpsq = this.epSquares[this.epSquares.length-1];
 171                 lastEpsq.push(epSq);
 172             }
 173             else
 174                 this.epSquares.push([epSq]);
 175             this.subTurn = 3 - this.subTurn;
 176         }
 177         this.updateVariables(move);
 178     }
 179
 180     undo(move)
 181     {
 182         this.disaggregateFlags(JSON.parse(move.flags));
 183         V.UndoOnBoard(this.board, move);
 184         if (move.turn[1] == '0' || move.checkOnSubturn1 || this.subTurn == 2)
 185             this.epSquares.pop();
 186         else //this.subTurn == 1
 187         {
 188             let lastEpsq = this.epSquares[this.epSquares.length-1];
 189             lastEpsq.pop();
 190         }
 191         this.turn = move.turn[0];
 192         this.subTurn = parseInt(move.turn[1]);
 193         this.unupdateVariables(move);
 194     }
 195
 196     // NOTE:  GenRandInitFen() is OK,
 197     // since at first move turn indicator is just "w"
 198
 199     static get VALUES()
 200     {
 201         return {
 202             'p': 1,
 203             'r': 5,
 204             'n': 3,
 205             'b': 3,
 206             'q': 7, //slightly less than in orthodox game
 207             'k': 1000
 208         };
 209     }
 210
 211   // TODO: this is wrong: revise following base_rules.getComputerMove()
 212     // No alpha-beta here, just adapted min-max at depth 2(+1)
 213     getComputerMove()
 214     {
 215         if (this.subTurn == 2)
 216             return null; //TODO: imperfect interface setup
 217
 218         const maxeval = V.INFINITY;
 219         const color = this.turn;
 220         const oppCol = V.GetOppCol(this.turn);
 221
 222         // Search best (half) move for opponent turn
 223         const getBestMoveEval = () => {
 224             const turnBefore = this.turn + this.subTurn;
 225             let moves = this.getAllValidMoves();
 226             if (moves.length == 0)
 227             {
 228                 const score = this.getCurrentScore();
 229                 if (score == "1/2")
 230                     return 0;
 231                 return maxeval * (score == "1-0" ? 1 : -1);
 232             }
 233             let res = (oppCol == "w" ? -maxeval : maxeval);
 234             for (let m of moves)
 235             {
 236                 this.play(m);
 237                 // Now turn is oppCol,2 if m doesn't give check
 238                 // Otherwise it's color,1. In both cases the next test makes sense
 239                 if (!this.atLeastOneMove())
 240                 {
 241                     const score = this.getCurrentScore();
 242                     if (score == "1/2")
 243                         res = (oppCol == "w" ? Math.max(res, 0) : Math.min(res, 0));
 244                     else
 245                     {
 246                         // Found a mate
 247                         this.undo(m);
 248                         return maxeval * (score == "1-0" ? 1 : -1);
 249                     }
 250                 }
 251                 const evalPos = this.evalPosition();
 252                 res = (oppCol == "w" ? Math.max(res, evalPos) : Math.min(res, evalPos));
 253                 this.undo(m);
 254             }
 255             return res;
 256         };
 257
 258         let moves11 = this.getAllValidMoves();
 259         let doubleMoves = [];
 260         // Rank moves using a min-max at depth 2
 261         for (let i=0; i<moves11.length; i++)
 262         {
 263             this.play(moves11[i]);
 264             if (this.turn != color)
 265             {
 266                 // We gave check with last move: search the best opponent move
 267                 doubleMoves.push({moves:[moves11[i]], eval:getBestMoveEval()});
 268             }
 269             else
 270             {
 271                 let moves12 = this.getAllValidMoves();
 272                 for (let j=0; j<moves12.length; j++)
 273                 {
 274                     this.play(moves12[j]);
 275                     doubleMoves.push({
 276                         moves:[moves11[i],moves12[j]],
 277                         eval:getBestMoveEval()});
 278                     this.undo(moves12[j]);
 279                 }
 280             }
 281             this.undo(moves11[i]);
 282         }
 283
 284         doubleMoves.sort( (a,b) => {
 285             return (color=="w" ? 1 : -1) * (b.eval - a.eval); });
 286         let candidates = [0]; //indices of candidates moves
 287         for (let i=1;
 288             i<doubleMoves.length && doubleMoves[i].eval == doubleMoves[0].eval;
 289             i++)
 290         {
 291             candidates.push(i);
 292         }
 293
 294         const selected = doubleMoves[sample(candidates)].moves;
 295         if (selected.length == 1)
 296             return selected[0];
 297         return selected;
 298     }
 299 }