client/src/variants/Allmate2.js

   1 import { ChessRules, PiPo, Move } from "@/base_rules";
   2
   3 export const VariantRules = class Allmate2Rules extends ChessRules {
   4   static get HasEnpassant() {
   5     return false;
   6   }
   7
   8   getCheckSquares() {
   9     // No notion of check
  10     return [];
  11   }
  12
  13   static GenRandInitFen() {
  14     return ChessRules.GenRandInitFen().replace(/ -$/, "");
  15   }
  16
  17   getPotentialMovesFrom([x, y]) {
  18     let moves = super.getPotentialMovesFrom([x, y]);
  19     // Remove standard captures (without removing castling):
  20     moves = moves.filter(m => {
  21       return m.vanish.length == 1 || m.appear.length == 2;
  22     });
  23
  24     // Augment moves with "mate-captures":
  25     // TODO: this is coded in a highly inefficient way...
  26     const color = this.turn;
  27     const oppCol = V.GetOppCol(this.turn);
  28     moves.forEach(m => {
  29       this.play(m);
  30
  31       // 1) What is attacked?
  32       let attacked = {};
  33       for (let i=0; i<V.size.x; i++) {
  34         for (let j=0; j<V.size.y; j++) {
  35           if (this.getColor(i,j) == oppCol && this.isAttacked([i,j], [color]))
  36             attacked[i+"_"+j] = [i,j];
  37         }
  38       }
  39
  40       // 2) Among attacked pieces, which cannot escape capture?
  41       // --> without (normal-)capturing: difference with Allmate variant
  42       // Avoid "oppMoves = this.getAllValidMoves();" => infinite recursion
  43       outerLoop: for (let i=0; i<V.size.x; i++) {
  44         for (let j=0; j<V.size.y; j++) {
  45           if (this.getColor(i,j) == oppCol) {
  46             let oppMoves = [];
  47             switch (this.getPiece(i, j)) {
  48               case V.PAWN:
  49                 oppMoves = this.getPotentialPawnMoves([i, j]);
  50                 break;
  51               case V.ROOK:
  52                 oppMoves = this.getPotentialRookMoves([i, j]);
  53                 break;
  54               case V.KNIGHT:
  55                 oppMoves = this.getPotentialKnightMoves([i, j]);
  56                 break;
  57               case V.BISHOP:
  58                 oppMoves = this.getPotentialBishopMoves([i, j]);
  59                 break;
  60               case V.QUEEN:
  61                 oppMoves = this.getPotentialQueenMoves([i, j]);
  62                 break;
  63               case V.KING:
  64                 oppMoves = this.getPotentialKingMoves([i, j]);
  65                 break;
  66             }
  67             for (let om of oppMoves) {
  68               if (om.vanish.length == 2 && om.appear.length == 1)
  69                 // Skip captures: forbidden in this mode
  70                 continue;
  71               V.PlayOnBoard(this.board, om);
  72               Object.values(attacked).forEach(sq => {
  73                 const origSq = [sq[0], sq[1]];
  74                 if (om.start.x == sq[0] && om.start.y == sq[1])
  75                   // Piece moved:
  76                   sq = [om.appear[0].x, om.appear[0].y];
  77                 if (!this.isAttacked(sq, [color]))
  78                   delete attacked[origSq[0]+"_"+origSq[1]];
  79               });
  80               V.UndoOnBoard(this.board, om);
  81               if (Object.keys(attacked).length == 0)
  82                 // No need to explore more moves
  83                 break outerLoop;
  84             }
  85           }
  86         }
  87       }
  88
  89       // 3) Add mate-captures:
  90       Object.values(attacked).forEach(sq => {
  91         m.vanish.push(new PiPo({
  92           x: sq[0],
  93           y: sq[1],
  94           c: oppCol,
  95           p: this.getPiece(sq[0], sq[1])
  96         }));
  97       });
  98
  99       this.undo(m);
 100     });
 101
 102     return moves;
 103   }
 104
 105   // No "under check" conditions in castling
 106   getCastleMoves([x, y]) {
 107     const c = this.getColor(x, y);
 108     if (x != (c == "w" ? V.size.x - 1 : 0) || y != this.INIT_COL_KING[c])
 109       return []; //x isn't first rank, or king has moved (shortcut)
 110
 111     // Castling ?
 112     const oppCol = V.GetOppCol(c);
 113     let moves = [];
 114     let i = 0;
 115     // King, then rook:
 116     const finalSquares = [
 117       [2, 3],
 118       [V.size.y - 2, V.size.y - 3]
 119     ];
 120     castlingCheck: for (
 121       let castleSide = 0;
 122       castleSide < 2;
 123       castleSide++ //large, then small
 124     ) {
 125       if (!this.castleFlags[c][castleSide]) continue;
 126       // If this code is reached, rooks and king are on initial position
 127
 128       // Nothing on the path of the king ? (and no checks)
 129       const finDist = finalSquares[castleSide][0] - y;
 130       let step = finDist / Math.max(1, Math.abs(finDist));
 131       for (let i = y; i != finalSquares[castleSide][0]; i += step) {
 132         if (
 133           this.board[x][i] != V.EMPTY &&
 134             // NOTE: next check is enough, because of chessboard constraints
 135             (this.getColor(x, i) != c ||
 136               ![V.KING, V.ROOK].includes(this.getPiece(x, i)))
 137         ) {
 138           continue castlingCheck;
 139         }
 140       }
 141
 142       // Nothing on the path to the rook?
 143       step = castleSide == 0 ? -1 : 1;
 144       for (i = y + step; i != this.INIT_COL_ROOK[c][castleSide]; i += step) {
 145         if (this.board[x][i] != V.EMPTY) continue castlingCheck;
 146       }
 147       const rookPos = this.INIT_COL_ROOK[c][castleSide];
 148
 149       // Nothing on final squares, except maybe king and castling rook?
 150       for (i = 0; i < 2; i++) {
 151         if (
 152           this.board[x][finalSquares[castleSide][i]] != V.EMPTY &&
 153           this.getPiece(x, finalSquares[castleSide][i]) != V.KING &&
 154           finalSquares[castleSide][i] != rookPos
 155         ) {
 156           continue castlingCheck;
 157         }
 158       }
 159
 160       // If this code is reached, castle is valid
 161       moves.push(
 162         new Move({
 163           appear: [
 164             new PiPo({ x: x, y: finalSquares[castleSide][0], p: V.KING, c: c }),
 165             new PiPo({ x: x, y: finalSquares[castleSide][1], p: V.ROOK, c: c })
 166           ],
 167           vanish: [
 168             new PiPo({ x: x, y: y, p: V.KING, c: c }),
 169             new PiPo({ x: x, y: rookPos, p: V.ROOK, c: c })
 170           ],
 171           end:
 172             Math.abs(y - rookPos) <= 2
 173               ? { x: x, y: rookPos }
 174               : { x: x, y: y + 2 * (castleSide == 0 ? -1 : 1) }
 175         })
 176       );
 177     }
 178
 179     return moves;
 180   }
 181
 182   // TODO: allow pieces to "commit suicide"? (Currently yes except king)
 183   filterValid(moves) {
 184     // Remove moves which let the king mate-captured:
 185     if (moves.length == 0) return [];
 186     const color = this.turn;
 187     const oppCol = V.GetOppCol(color);
 188     return moves.filter(m => {
 189       let res = true;
 190       this.play(m);
 191       if (this.underCheck(color)) {
 192         res = false;
 193         const attacked = this.kingPos[color];
 194         // Try to find a move to escape check
 195         // TODO: very inefficient method.
 196         outerLoop: for (let i=0; i<V.size.x; i++) {
 197           for (let j=0; j<V.size.y; j++) {
 198             if (this.getColor(i,j) == color) {
 199               let emoves = [];
 200               // Artficial turn change to "play twice":
 201               this.turn = color;
 202               switch (this.getPiece(i, j)) {
 203                 case V.PAWN:
 204                   emoves = this.getPotentialPawnMoves([i, j]);
 205                   break;
 206                 case V.ROOK:
 207                   emoves = this.getPotentialRookMoves([i, j]);
 208                   break;
 209                 case V.KNIGHT:
 210                   emoves = this.getPotentialKnightMoves([i, j]);
 211                   break;
 212                 case V.BISHOP:
 213                   emoves = this.getPotentialBishopMoves([i, j]);
 214                   break;
 215                 case V.QUEEN:
 216                   emoves = this.getPotentialQueenMoves([i, j]);
 217                   break;
 218                 case V.KING:
 219                   emoves = this.getPotentialKingMoves([i, j]);
 220                   break;
 221               }
 222               this.turn = oppCol;
 223               for (let em of emoves) {
 224                 V.PlayOnBoard(this.board, em);
 225                 let sq = attacked;
 226                 if (em.start.x == attacked[0] && em.start.y == attacked[1])
 227                   // King moved:
 228                   sq = [em.appear[0].x, em.appear[0].y];
 229                 if (!this.isAttacked(sq, [oppCol]))
 230                   res = true;
 231                 V.UndoOnBoard(this.board, em);
 232                 if (res)
 233                   // No need to explore more moves
 234                   break outerLoop;
 235               }
 236             }
 237           }
 238         }
 239       }
 240       this.undo(m);
 241       return res;
 242     });
 243   }
 244
 245   updateVariables(move) {
 246     super.updateVariables(move);
 247     const color = V.GetOppCol(this.turn);
 248     if (move.vanish.length >= 2 && move.appear.length == 1) {
 249       move.vanish.forEach(v => {
 250         if (v.c == color)
 251           return;
 252         // Did opponent king disappeared?
 253         if (v.p == V.KING)
 254           this.kingPos[this.turn] = [-1, -1];
 255         // Or maybe a rook?
 256         else if (v.p == V.ROOK) {
 257           if (v.y < this.INIT_COL_KING[v.c])
 258             this.castleFlags[v.c][0] = false;
 259           else
 260             // v.y > this.INIT_COL_KING[v.c]
 261             this.castleFlags[v.c][1] = false;
 262         }
 263       });
 264     }
 265   }
 266
 267   unupdateVariables(move) {
 268     super.unupdateVariables(move);
 269     const color = this.turn;
 270     if (move.vanish.length >= 2 && move.appear.length == 1) {
 271       // Did opponent king disappeared?
 272       const psq = move.vanish.find(v => v.p == V.KING && v.c != color)
 273       if (psq)
 274         this.kingPos[psq.c] = [psq.x, psq.y];
 275     }
 276   }
 277
 278   getCurrentScore() {
 279     const color = this.turn;
 280     const kp = this.kingPos[color];
 281     if (kp[0] < 0)
 282       // King disappeared
 283       return color == "w" ? "0-1" : "1-0";
 284     if (this.atLeastOneMove())
 285       return "*";
 286     // Kings still there, no moves:
 287     return "1/2";
 288   }
 289
 290   static get SEARCH_DEPTH() {
 291     return 2;
 292   }
 293
 294   getNotation(move) {
 295     let notation = super.getNotation(move);
 296     // Add a capture mark (not describing what is captured...):
 297     if (move.vanish.length > 1 && move.appear.length == 1) {
 298       if (notation.match(/^[a-h]x/))
 299         // Pawn capture: remove initial "b" in bxc4 for example
 300         notation = notation.substr(1);
 301       notation = notation.replace("x","") + "X";
 302     }
 303     return notation;
 304   }
 305 };