client/src/variants/Royalrace.js

   1 import { ChessRules } from "@/base_rules";
   2 import { ArrayFun } from "@/utils/array";
   3 import { randInt, shuffle } from "@/utils/alea";
   4
   5 export class RoyalraceRules extends ChessRules {
   6   static get HasFlags() {
   7     return false;
   8   }
   9
  10   static get HasEnpassant() {
  11     return false;
  12   }
  13
  14   static get CanFlip() {
  15     return false;
  16   }
  17
  18   static get size() {
  19     return { x: 11, y: 11 };
  20   }
  21
  22   static GenRandInitFen(randomness) {
  23     if (randomness == 0)
  24       return "92/92/92/92/92/92/92/92/92/qrbnp1PNBRQ/krbnp1PNBRK w 0";
  25
  26     let pieces = { w: new Array(10), b: new Array(10) };
  27     // Shuffle pieces on first and second rank
  28     for (let c of ["w", "b"]) {
  29       if (c == 'b' && randomness == 1) {
  30         pieces['b'] = JSON.parse(JSON.stringify(pieces['w'])).reverse();
  31         pieces['b'] =
  32           pieces['b'].splice(5,10).reverse().concat(
  33           pieces['b'].splice(0,5).reverse());
  34         break;
  35       }
  36
  37       // Reserve 4 and 5 which are pawns positions
  38       let positions = ArrayFun.range(10).filter(i => i != 4 && i != 5);
  39
  40       // Get random squares for bishops
  41       let randIndex = 2 * randInt(4);
  42       const bishop1Pos = positions[randIndex];
  43       // The second bishop must be on a square of different color
  44       let randIndex_tmp = 2 * randInt(4) + 1;
  45       const bishop2Pos = positions[randIndex_tmp];
  46       // Remove chosen squares
  47       positions.splice(Math.max(randIndex, randIndex_tmp), 1);
  48       positions.splice(Math.min(randIndex, randIndex_tmp), 1);
  49
  50       // Place the king at random on (remaining squares of) first row
  51       let maxIndex = 4;
  52       if (positions[maxIndex-1] >= 4)
  53         maxIndex--;
  54       if (positions[maxIndex-1] >= 4)
  55         maxIndex--;
  56       randIndex = randInt(maxIndex);
  57       const kingPos = positions[randIndex];
  58       positions.splice(randIndex, 1);
  59
  60       // Get random squares for knights
  61       randIndex = randInt(5);
  62       const knight1Pos = positions[randIndex];
  63       positions.splice(randIndex, 1);
  64       randIndex = randInt(4);
  65       const knight2Pos = positions[randIndex];
  66       positions.splice(randIndex, 1);
  67
  68       // Get random squares for rooks
  69       randIndex = randInt(3);
  70       const rook1Pos = positions[randIndex];
  71       positions.splice(randIndex, 1);
  72       randIndex = randInt(2);
  73       const rook2Pos = positions[randIndex];
  74       positions.splice(randIndex, 1);
  75
  76       // Queen position is now determined,
  77       // because pawns are not placed at random
  78       const queenPos = positions[0];
  79
  80       // Finally put the shuffled pieces in the board array
  81       pieces[c][rook1Pos] = "r";
  82       pieces[c][knight1Pos] = "n";
  83       pieces[c][bishop1Pos] = "b";
  84       pieces[c][queenPos] = "q";
  85       pieces[c][kingPos] = "k";
  86       pieces[c][bishop2Pos] = "b";
  87       pieces[c][knight2Pos] = "n";
  88       pieces[c][rook2Pos] = "r";
  89       pieces[c][4] = "p";
  90       pieces[c][5] = "p";
  91     }
  92     const whiteFen = pieces["w"].join("").toUpperCase();
  93     const blackFen = pieces["b"].join("");
  94     return (
  95       "92/92/92/92/92/92/92/92/92/" +
  96       blackFen.substr(5).split("").reverse().join("") +
  97       "1" +
  98       whiteFen.substr(5).split("").join("") +
  99       "/" +
 100       blackFen.substr(0,5) +
 101       "1" +
 102       whiteFen.substr(0,5).split("").reverse().join("") +
 103       " w 0"
 104     );
 105   }
 106
 107   getPotentialPawnMoves([x, y]) {
 108     // Normal moves (as a rook)
 109     let moves =
 110       this.getSlideNJumpMoves([x, y], V.steps[V.ROOK]).filter(m => {
 111         // Remove captures. Alt: redefine canTake
 112         return m.vanish.length == 1;
 113       });
 114
 115     // Captures (in both directions)
 116     for (let shiftX of [-1, 1]) {
 117       for (let shiftY of [-1, 1]) {
 118         if (
 119           V.OnBoard(x + shiftX, y + shiftY) &&
 120           this.board[x + shiftX][y + shiftY] != V.EMPTY &&
 121           this.canTake([x, y], [x + shiftX, y + shiftY])
 122         ) {
 123           moves.push(this.getBasicMove([x, y], [x + shiftX, y + shiftY]));
 124         }
 125       }
 126     }
 127
 128     return moves;
 129   }
 130
 131   getPotentialKnightMoves(sq) {
 132     // Knight becomes knightrider:
 133     return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT]);
 134   }
 135
 136   filterValid(moves) {
 137     if (moves.length == 0) return [];
 138     const color = this.turn;
 139     const oppCol = V.GetOppCol(color);
 140     return moves.filter(m => {
 141       this.play(m);
 142       // Giving check is forbidden as well:
 143       const res = !this.underCheck(color) && !this.underCheck(oppCol);
 144       this.undo(m);
 145       return res;
 146     });
 147   }
 148
 149   isAttackedByPawn([x, y], color) {
 150     // Pawns can capture forward and backward:
 151     for (let pawnShift of [-1, 1]) {
 152       if (0 < x + pawnShift && x + pawnShift < V.size.x) {
 153         for (let i of [-1, 1]) {
 154           if (
 155             y + i >= 0 &&
 156             y + i < V.size.y &&
 157             this.getPiece(x + pawnShift, y + i) == V.PAWN &&
 158             this.getColor(x + pawnShift, y + i) == color
 159           ) {
 160             return true;
 161           }
 162         }
 163       }
 164     }
 165     return false;
 166   }
 167
 168   isAttackedByKnight(sq, color) {
 169     return this.isAttackedBySlideNJump(
 170       sq,
 171       color,
 172       V.KNIGHT,
 173       V.steps[V.KNIGHT]
 174     );
 175   }
 176
 177   getCurrentScore() {
 178     // Turn has changed:
 179     const color = V.GetOppCol(this.turn);
 180     if (this.kingPos[color][0] == 0)
 181       // The opposing edge is reached!
 182       return color == "w" ? "1-0" : "0-1";
 183     if (this.atLeastOneMove()) return "*";
 184     // Stalemate (will probably never happen)
 185     return "1/2";
 186   }
 187
 188   static get SEARCH_DEPTH() {
 189     return 2;
 190   }
 191
 192   static get VALUES() {
 193     return {
 194       p: 2,
 195       r: 5,
 196       n: 3,
 197       b: 3,
 198       q: 9,
 199       k: 1000
 200     };
 201   }
 202
 203   evalPosition() {
 204     // Count material:
 205     let evaluation = super.evalPosition();
 206     // Ponder with king position:
 207     return evaluation/5 + this.kingPos["b"][0] - this.kingPos["w"][0];
 208   }
 209
 210   getNotation(move) {
 211     // Since pawns are much more mobile, treat them as other pieces:
 212     return (
 213       move.vanish[0].p.toUpperCase() +
 214       (move.vanish.length > move.appear.length ? "x" : "") +
 215       V.CoordsToSquare(move.end)
 216     );
 217   }
 218 };