client/src/variants/Swap.js

   1 import { ChessRules, PiPo } from "@/base_rules";
   2 import { randInt } from "@/utils/alea";
   3
   4 export class SwapRules extends ChessRules {
   5
   6   setOtherVariables(fen) {
   7     super.setOtherVariables(fen);
   8     // Local stack of swaps
   9     this.swaps = [];
  10     const smove = V.ParseFen(fen).smove;
  11     if (smove == "-") this.swaps.push(null);
  12     else {
  13       this.swaps.push({
  14         start: ChessRules.SquareToCoords(smove.substr(0, 2)),
  15         end: ChessRules.SquareToCoords(smove.substr(2))
  16       });
  17     }
  18     this.subTurn = 1;
  19   }
  20
  21   static ParseFen(fen) {
  22     return Object.assign(
  23       ChessRules.ParseFen(fen),
  24       { smove: fen.split(" ")[5] }
  25     );
  26   }
  27
  28   static IsGoodFen(fen) {
  29     if (!ChessRules.IsGoodFen(fen)) return false;
  30     const fenParts = fen.split(" ");
  31     if (fenParts.length != 6) return false;
  32     if (fenParts[5] != "-" && !fenParts[5].match(/^([a-h][1-8]){2}$/))
  33       return false;
  34     return true;
  35   }
  36
  37   getPPpath(m) {
  38     if (m.appear.length == 1) return super.getPPpath(m);
  39     // Swap promotion:
  40     return m.appear[1].c + m.appear[1].p;
  41   }
  42
  43   getSwapMoves([x1, y1], [x2, y2]) {
  44     let move = super.getBasicMove([x1, y1], [x2, y2]);
  45     move.appear.push(
  46       new PiPo({
  47         x: x1,
  48         y: y1,
  49         c: this.getColor(x2, y2),
  50         p: this.getPiece(x2, y2)
  51       })
  52     );
  53     const lastRank = (move.appear[1].c == 'w' ? 0 : 7);
  54     if (move.appear[1].p == V.PAWN && move.appear[1].x == lastRank) {
  55       // Promotion:
  56       move.appear[1].p = V.ROOK;
  57       let moves = [move];
  58       [V.KNIGHT, V.BISHOP, V.QUEEN].forEach(p => {
  59         let m = JSON.parse(JSON.stringify(move));
  60         m.appear[1].p = p;
  61         moves.push(m);
  62       });
  63       return moves;
  64     }
  65     return [move];
  66   }
  67
  68   getPotentialMovesFrom([x, y]) {
  69     if (this.subTurn == 1) return super.getPotentialMovesFrom([x, y]);
  70     // SubTurn == 2: only swaps
  71     let moves = [];
  72     const color = this.turn;
  73     const piece = this.getPiece(x, y);
  74     const addSmoves = (i, j) => {
  75       if (this.getPiece(i, j) != piece || this.getColor(i, j) != color)
  76         Array.prototype.push.apply(moves, this.getSwapMoves([x, y], [i, j]));
  77     };
  78     switch (piece) {
  79       case V.PAWN: {
  80         const forward = (color == 'w' ? -1 : 1);
  81         const startRank = (color == 'w' ? [6, 7] : [0, 1]);
  82         if (
  83           x == startRank &&
  84           this.board[x + forward][y] == V.EMPTY &&
  85           this.board[x + 2 * forward][y] != V.EMPTY
  86         ) {
  87           // Swap using 2 squares move
  88           addSmoves(x + 2 * forward, y);
  89         }
  90         for (let shift of [-1, 0, 1]) {
  91           const [i, j] = [x + forward, y + shift];
  92           if (V.OnBoard(i, j) && this.board[i][j] != V.EMPTY) addSmoves(i, j);
  93         }
  94         break;
  95       }
  96       case V.KNIGHT:
  97         V.steps[V.KNIGHT].forEach(s => {
  98           const [i, j] = [x + s[0], y + s[1]];
  99           if (V.OnBoard(i, j) && this.board[i][j] != V.EMPTY) addSmoves(i, j);
 100         });
 101         break;
 102       case V.KING:
 103         V.steps[V.ROOK].concat(V.steps[V.BISHOP]).forEach(s => {
 104           const [i, j] = [x + s[0], y + s[1]];
 105           if (V.OnBoard(i, j) && this.board[i][j] != V.EMPTY) addSmoves(i, j);
 106         });
 107         break;
 108       case V.ROOK:
 109       case V.BISHOP:
 110       case V.QUEEN: {
 111         const steps =
 112           piece != V.QUEEN
 113             ? V.steps[piece]
 114             : V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
 115         steps.forEach(s => {
 116           let [i, j] = [x + s[0], y + s[1]];
 117           while (V.OnBoard(i, j) && this.board[i][j] == V.EMPTY) {
 118             i += s[0];
 119             j += s[1];
 120           }
 121           if (V.OnBoard(i, j) && this.board[i][j] != V.EMPTY) addSmoves(i, j);
 122         });
 123         break;
 124       }
 125     }
 126     return moves;
 127   }
 128
 129   // Does m2 un-do m1 ? (to disallow undoing swaps)
 130   oppositeSwaps(m1, m2) {
 131     return (
 132       !!m1 &&
 133       m1.start.x == m2.start.x &&
 134       m1.end.x == m2.end.x &&
 135       m1.start.y == m2.start.y &&
 136       m1.end.y == m2.end.y
 137     );
 138   }
 139
 140   filterValid(moves) {
 141     const fmoves = super.filterValid(moves);
 142     if (this.subTurn == 1) return fmoves;
 143     return fmoves.filter(m => {
 144       const L = this.swaps.length; //at least 1: init from FEN
 145       return !this.oppositeSwaps(this.swaps[L - 1], m);
 146     });
 147   }
 148
 149   static GenRandInitFen(options) {
 150     // Add empty smove:
 151     return ChessRules.GenRandInitFen(options) + " -";
 152   }
 153
 154   getSmoveFen() {
 155     const L = this.swaps.length;
 156     return (
 157       !this.swaps[L - 1]
 158         ? "-"
 159         : ChessRules.CoordsToSquare(this.swaps[L - 1].start) +
 160           ChessRules.CoordsToSquare(this.swaps[L - 1].end)
 161     );
 162   }
 163
 164   getFen() {
 165     return super.getFen() + " " + this.getSmoveFen();
 166   }
 167
 168   getFenForRepeat() {
 169     return super.getFenForRepeat() + "_" + this.getSmoveFen();
 170   }
 171
 172   getCurrentScore() {
 173     const L = this.swaps.length;
 174     if (this.movesCount >= 2 && !this.swaps[L-1])
 175       // Opponent had no swap moves: I win
 176       return (this.turn == "w" ? "1-0" : "0-1");
 177     if (this.atLeastOneMove()) return "*";
 178     // No valid move: I lose
 179     return (this.turn == "w" ? "0-1" : "1-0");
 180   }
 181
 182   noSwapAfter(move) {
 183     this.subTurn = 2;
 184     const res = !this.atLeastOneMove();
 185     this.subTurn = 1;
 186     return res;
 187   }
 188
 189   play(move) {
 190     move.flags = JSON.stringify(this.aggregateFlags());
 191     move.turn = [this.turn, this.subTurn];
 192     V.PlayOnBoard(this.board, move);
 193     let epSq = undefined;
 194     if (this.subTurn == 1) epSq = this.getEpSquare(move);
 195     if (this.movesCount == 0) {
 196       // First move in game
 197       this.turn = "b";
 198       this.epSquares.push(epSq);
 199       this.movesCount = 1;
 200     }
 201     // Any swap available after move? If no, skip subturn 2
 202     else if (this.subTurn == 1 && this.noSwapAfter(move)) {
 203       this.turn = V.GetOppCol(this.turn);
 204       this.epSquares.push(epSq);
 205       move.noSwap = true;
 206       this.movesCount++;
 207     }
 208     else {
 209       if (this.subTurn == 2) {
 210         this.turn = V.GetOppCol(this.turn);
 211         this.swaps.push({ start: move.start, end: move.end });
 212       }
 213       else {
 214         this.epSquares.push(epSq);
 215         this.movesCount++;
 216       }
 217       this.subTurn = 3 - this.subTurn;
 218     }
 219     this.postPlay(move);
 220   }
 221
 222   postPlay(move) {
 223     const firstRank = { 7: 'w', 0: 'b' };
 224     // Did some king move?
 225     move.appear.forEach(a => {
 226       if (a.p == V.KING) {
 227         this.kingPos[a.c] = [a.x, a.y];
 228         this.castleFlags[a.c] = [V.size.y, V.size.y];
 229       }
 230     });
 231     for (let coords of [move.start, move.end]) {
 232       if (
 233         Object.keys(firstRank).includes(coords.x) &&
 234         this.castleFlags[firstRank[coords.x]].includes(coords.y)
 235       ) {
 236         const c = firstRank[coords.x];
 237         const flagIdx = (coords.y == this.castleFlags[c][0] ? 0 : 1);
 238         this.castleFlags[c][flagIdx] = V.size.y;
 239       }
 240     }
 241   }
 242
 243   undo(move) {
 244     this.disaggregateFlags(JSON.parse(move.flags));
 245     V.UndoOnBoard(this.board, move);
 246     if (move.turn[1] == 1) {
 247       // The move may not be full, but is fully undone:
 248       this.epSquares.pop();
 249       // Moves counter was just incremented:
 250       this.movesCount--;
 251     }
 252     else
 253       // Undo the second half of a move
 254       this.swaps.pop();
 255     this.turn = move.turn[0];
 256     this.subTurn = move.turn[1];
 257     this.postUndo(move);
 258   }
 259
 260   postUndo(move) {
 261     // Did some king move?
 262     move.vanish.forEach(v => {
 263       if (v.p == V.KING) this.kingPos[v.c] = [v.x, v.y];
 264     });
 265   }
 266
 267   // No alpha-beta here, just adapted min-max at depth 2(+1)
 268   getComputerMove() {
 269     const maxeval = V.INFINITY;
 270     const color = this.turn;
 271     const oppCol = V.GetOppCol(this.turn);
 272
 273     // NOTE: searching best (half) move for opponent turn is a bit too slow.
 274     // => Only 2 half moves depth here.
 275
 276     const moves11 = this.getAllValidMoves();
 277     if (this.movesCount == 0)
 278       // Just play first move at random:
 279       return moves11[randInt(moves11.length)];
 280     let bestMove = undefined;
 281     // Rank moves using a min-max at depth 2
 282     for (let i = 0; i < moves11.length; i++) {
 283       this.play(moves11[i]);
 284       if (!!moves11[i].noSwap) {
 285         // I lose
 286         if (!bestMove) bestMove = {
 287           moves: moves11[i],
 288           eval: (color == 'w' ? -maxeval : maxeval)
 289         };
 290       }
 291       else {
 292         let moves12 = this.getAllValidMoves();
 293         for (let j = 0; j < moves12.length; j++) {
 294           this.play(moves12[j]);
 295           const evalMove = this.evalPosition() + 0.05 - Math.random() / 10;
 296           if (
 297             !bestMove ||
 298             (color == 'w' && evalMove > bestMove.eval) ||
 299             (color == 'b' && evalMove < bestMove.eval)
 300           ) {
 301             bestMove = {
 302               moves: [moves11[i], moves12[j]],
 303               eval: evalMove
 304             };
 305           }
 306           this.undo(moves12[j]);
 307         }
 308       }
 309       this.undo(moves11[i]);
 310     }
 311     return bestMove.moves;
 312   }
 313
 314   getNotation(move) {
 315     if (move.appear.length == 1)
 316       // Normal move
 317       return super.getNotation(move);
 318     if (move.appear[0].p == V.KING && move.appear[1].p == V.ROOK)
 319       // Castle
 320       return (move.end.y < move.start.y ? "0-0-0" : "0-0");
 321     // Swap
 322     return "S" + V.CoordsToSquare(move.start) + V.CoordsToSquare(move.end);
 323   }
 324
 325 };