client/src/variants/Dark.js

   1 import { ChessRules } from "@/base_rules";
   2 import { ArrayFun } from "@/utils/array";
   3 import { randInt } from "@/utils/alea";
   4
   5 export class DarkRules extends ChessRules {
   6   // Analyse in Dark mode makes no sense
   7   static get CanAnalyze() {
   8     return false;
   9   }
  10
  11   // Moves are revealed only when game ends
  12   static get ShowMoves() {
  13     return "none";
  14   }
  15
  16   setOtherVariables(fen) {
  17     super.setOtherVariables(fen);
  18     const [sizeX, sizeY] = [V.size.x, V.size.y];
  19     this.enlightened = {
  20       w: ArrayFun.init(sizeX, sizeY),
  21       b: ArrayFun.init(sizeX, sizeY)
  22     };
  23     // Setup enlightened: squares reachable by each side
  24     // (TODO: one side would be enough ?)
  25     this.updateEnlightened();
  26   }
  27
  28   updateEnlightened() {
  29     for (let i = 0; i < V.size.x; i++) {
  30       for (let j = 0; j < V.size.y; j++) {
  31         this.enlightened["w"][i][j] = false;
  32         this.enlightened["b"][i][j] = false;
  33       }
  34     }
  35     const pawnShift = { w: -1, b: 1 };
  36     // Initialize with pieces positions (which are seen)
  37     for (let i = 0; i < V.size.x; i++) {
  38       for (let j = 0; j < V.size.y; j++) {
  39         if (this.board[i][j] != V.EMPTY) {
  40           const c = this.getColor(i, j);
  41           this.enlightened[c][i][j] = true;
  42           // Add potential squares visible by "impossible pawn capture"
  43           if (this.getPiece(i, j) == V.PAWN) {
  44             for (let shiftY of [-1, 1]) {
  45               if (
  46                 V.OnBoard(i + pawnShift[c], j + shiftY) &&
  47                 this.board[i + pawnShift[c]][j + shiftY] == V.EMPTY
  48               ) {
  49                 this.enlightened[c][i + pawnShift[c]][j + shiftY] = true;
  50               }
  51             }
  52           }
  53         }
  54       }
  55     }
  56     const currentTurn = this.turn;
  57     this.turn = "w";
  58     const movesWhite = this.getAllValidMoves();
  59     this.turn = "b";
  60     const movesBlack = this.getAllValidMoves();
  61     this.turn = currentTurn;
  62     for (let move of movesWhite)
  63       this.enlightened["w"][move.end.x][move.end.y] = true;
  64     for (let move of movesBlack)
  65       this.enlightened["b"][move.end.x][move.end.y] = true;
  66     // Include en-passant capturing square if any:
  67     let moves = currentTurn == "w" ? movesWhite : movesBlack;
  68     for (let m of moves) {
  69       if (
  70         m.appear[0].p == V.PAWN &&
  71         m.vanish.length == 2 &&
  72         m.vanish[1].x != m.end.x
  73       ) {
  74         const psq = m.vanish[1];
  75         this.enlightened[currentTurn][psq.x][psq.y] = true;
  76         break;
  77       }
  78     }
  79   }
  80
  81   filterValid(moves) {
  82     // Used in the interface
  83     return moves;
  84   }
  85
  86   // Has to be redefined to avoid an infinite loop
  87   getAllValidMoves() {
  88     const color = this.turn;
  89     let potentialMoves = [];
  90     for (let i = 0; i < V.size.x; i++) {
  91       for (let j = 0; j < V.size.y; j++) {
  92         if (this.board[i][j] != V.EMPTY && this.getColor(i, j) == color)
  93           Array.prototype.push.apply(
  94             potentialMoves,
  95             this.getPotentialMovesFrom([i, j])
  96           );
  97       }
  98     }
  99     return potentialMoves; //because there are no checks
 100   }
 101
 102   getCheckSquares() {
 103     return [];
 104   }
 105
 106   postPlay(move) {
 107     super.postPlay(move);
 108     if (move.vanish.length >= 2 && move.vanish[1].p == V.KING)
 109       // We took opponent king (because if castle vanish[1] is a rook)
 110       this.kingPos[this.turn] = [-1, -1];
 111
 112     // Update lights for both colors:
 113     this.updateEnlightened();
 114   }
 115
 116   postUndo(move) {
 117     super.postUndo(move);
 118     const c = move.vanish[0].c;
 119     const oppCol = V.GetOppCol(c);
 120     if (this.kingPos[oppCol][0] < 0)
 121       // Last move took opponent's king:
 122       this.kingPos[oppCol] = [move.vanish[1].x, move.vanish[1].y];
 123
 124     // Update lights for both colors:
 125     this.updateEnlightened();
 126   }
 127
 128   getCurrentScore() {
 129     const color = this.turn;
 130     const kp = this.kingPos[color];
 131     if (kp[0] < 0)
 132       // King disappeared
 133       return color == "w" ? "0-1" : "1-0";
 134     // Assume that stalemate is impossible (I think so. Would need proof...)
 135     return "*";
 136   }
 137
 138   static get THRESHOLD_MATE() {
 139     return 500; //checkmates evals may be slightly below 1000
 140   }
 141
 142   // In this special situation, we just look 1 half move ahead
 143   getComputerMove() {
 144     const maxeval = V.INFINITY;
 145     const color = this.turn;
 146     const oppCol = V.GetOppCol(color);
 147     const pawnShift = color == "w" ? -1 : 1;
 148
 149     // Do not cheat: the current enlightment is all we can see
 150     const myLight = JSON.parse(JSON.stringify(this.enlightened[color]));
 151
 152     // Can a slider on (i,j) apparently take my king?
 153     // NOTE: inaccurate because assume yes if some squares are shadowed
 154     const sliderTake = ([i, j], piece) => {
 155       const kp = this.kingPos[color];
 156       let step = undefined;
 157       if (piece == V.BISHOP) {
 158         if (Math.abs(kp[0] - i) == Math.abs(kp[1] - j)) {
 159           step = [
 160             (i - kp[0]) / Math.abs(i - kp[0]),
 161             (j - kp[1]) / Math.abs(j - kp[1])
 162           ];
 163         }
 164       } else if (piece == V.ROOK) {
 165         if (kp[0] == i) step = [0, (j - kp[1]) / Math.abs(j - kp[1])];
 166         else if (kp[1] == j) step = [(i - kp[0]) / Math.abs(i - kp[0]), 0];
 167       }
 168       if (!step) return false;
 169       // Check for obstacles
 170       let obstacle = false;
 171       for (
 172         let x = kp[0] + step[0], y = kp[1] + step[1];
 173         x != i && y != j;
 174         x += step[0], y += step[1]
 175       ) {
 176         if (myLight[x][y] && this.board[x][y] != V.EMPTY) {
 177           obstacle = true;
 178           break;
 179         }
 180       }
 181       if (!obstacle) return true;
 182       return false;
 183     };
 184
 185     // Do I see something which can take my king ?
 186     const kingThreats = () => {
 187       const kp = this.kingPos[color];
 188       for (let i = 0; i < V.size.x; i++) {
 189         for (let j = 0; j < V.size.y; j++) {
 190           if (
 191             myLight[i][j] &&
 192             this.board[i][j] != V.EMPTY &&
 193             this.getColor(i, j) != color
 194           ) {
 195             switch (this.getPiece(i, j)) {
 196               case V.PAWN:
 197                 if (kp[0] + pawnShift == i && Math.abs(kp[1] - j) == 1)
 198                   return true;
 199                 break;
 200               case V.KNIGHT:
 201                 if (
 202                   (Math.abs(kp[0] - i) == 2 && Math.abs(kp[1] - j) == 1) ||
 203                   (Math.abs(kp[0] - i) == 1 && Math.abs(kp[1] - j) == 2)
 204                 ) {
 205                   return true;
 206                 }
 207                 break;
 208               case V.KING:
 209                 if (Math.abs(kp[0] - i) == 1 && Math.abs(kp[1] - j) == 1)
 210                   return true;
 211                 break;
 212               case V.BISHOP:
 213                 if (sliderTake([i, j], V.BISHOP)) return true;
 214                 break;
 215               case V.ROOK:
 216                 if (sliderTake([i, j], V.ROOK)) return true;
 217                 break;
 218               case V.QUEEN:
 219                 if (sliderTake([i, j], V.BISHOP) || sliderTake([i, j], V.ROOK))
 220                   return true;
 221                 break;
 222             }
 223           }
 224         }
 225       }
 226       return false;
 227     };
 228
 229     let moves = this.getAllValidMoves();
 230     for (let move of moves) {
 231       this.play(move);
 232       if (this.kingPos[oppCol][0] >= 0 && kingThreats()) {
 233         // We didn't take opponent king, and our king will be captured: bad
 234         move.eval = -maxeval;
 235       }
 236       this.undo(move);
 237
 238       if (move.eval) continue;
 239
 240       move.eval = 0; //a priori...
 241
 242       // Can I take something ? If yes, do it if it seems good...
 243       if (move.vanish.length == 2 && move.vanish[1].c != color) {
 244         // OK this isn't a castling move
 245         const myPieceVal = V.VALUES[move.appear[0].p];
 246         const hisPieceVal = V.VALUES[move.vanish[1].p];
 247         // Favor captures
 248         if (myPieceVal <= hisPieceVal)
 249           move.eval = hisPieceVal - myPieceVal + 1;
 250         else {
 251           // Taking a pawn with minor piece,
 252           // or minor piece or pawn with a rook,
 253           // or anything but a queen with a queen,
 254           // or anything with a king.
 255           move.eval = hisPieceVal - myPieceVal;
 256                       //Math.random() < 0.5 ? 1 : -1;
 257         }
 258       }
 259     }
 260
 261     // TODO: also need to implement the case when an opponent piece (in light)
 262     // is threatening something - maybe not the king, but e.g. pawn takes rook.
 263
 264     moves.sort((a, b) => b.eval - a.eval);
 265     let candidates = [0];
 266     for (let j = 1; j < moves.length && moves[j].eval == moves[0].eval; j++)
 267       candidates.push(j);
 268     return moves[candidates[randInt(candidates.length)]];
 269   }
 270 };