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   static get SomeHiddenMoves() {
  17     return true;
  18   }
  19
  20   setOtherVariables(fen) {
  21     super.setOtherVariables(fen);
  22     const [sizeX, sizeY] = [V.size.x, V.size.y];
  23     this.enlightened = {
  24       w: ArrayFun.init(sizeX, sizeY),
  25       b: ArrayFun.init(sizeX, sizeY)
  26     };
  27     // Setup enlightened: squares reachable by each side
  28     // (TODO: one side would be enough ?)
  29     this.updateEnlightened();
  30   }
  31
  32   updateEnlightened() {
  33     for (let i = 0; i < V.size.x; i++) {
  34       for (let j = 0; j < V.size.y; j++) {
  35         this.enlightened["w"][i][j] = false;
  36         this.enlightened["b"][i][j] = false;
  37       }
  38     }
  39     const pawnShift = { w: -1, b: 1 };
  40     // Initialize with pieces positions (which are seen)
  41     for (let i = 0; i < V.size.x; i++) {
  42       for (let j = 0; j < V.size.y; j++) {
  43         if (this.board[i][j] != V.EMPTY) {
  44           const c = this.getColor(i, j);
  45           this.enlightened[c][i][j] = true;
  46           // Add potential squares visible by "impossible pawn capture"
  47           if (this.getPiece(i, j) == V.PAWN) {
  48             for (let shiftY of [-1, 1]) {
  49               if (
  50                 V.OnBoard(i + pawnShift[c], j + shiftY) &&
  51                 this.board[i + pawnShift[c]][j + shiftY] == V.EMPTY
  52               ) {
  53                 this.enlightened[c][i + pawnShift[c]][j + shiftY] = true;
  54               }
  55             }
  56           }
  57         }
  58       }
  59     }
  60     const currentTurn = this.turn;
  61     this.turn = "w";
  62     const movesWhite = this.getAllValidMoves();
  63     this.turn = "b";
  64     const movesBlack = this.getAllValidMoves();
  65     this.turn = currentTurn;
  66     for (let move of movesWhite)
  67       this.enlightened["w"][move.end.x][move.end.y] = true;
  68     for (let move of movesBlack)
  69       this.enlightened["b"][move.end.x][move.end.y] = true;
  70     // Include en-passant capturing square if any:
  71     let moves = currentTurn == "w" ? movesWhite : movesBlack;
  72     for (let m of moves) {
  73       if (
  74         m.appear[0].p == V.PAWN &&
  75         m.vanish.length == 2 &&
  76         m.vanish[1].x != m.end.x
  77       ) {
  78         const psq = m.vanish[1];
  79         this.enlightened[currentTurn][psq.x][psq.y] = true;
  80         break;
  81       }
  82     }
  83   }
  84
  85   filterValid(moves) {
  86     // Used in the interface
  87     return moves;
  88   }
  89
  90   // Has to be redefined to avoid an infinite loop
  91   getAllValidMoves() {
  92     const color = this.turn;
  93     let potentialMoves = [];
  94     for (let i = 0; i < V.size.x; i++) {
  95       for (let j = 0; j < V.size.y; j++) {
  96         if (this.board[i][j] != V.EMPTY && this.getColor(i, j) == color)
  97           Array.prototype.push.apply(
  98             potentialMoves,
  99             this.getPotentialMovesFrom([i, j])
 100           );
 101       }
 102     }
 103     return potentialMoves; //because there are no checks
 104   }
 105
 106   getCheckSquares() {
 107     return [];
 108   }
 109
 110   postPlay(move) {
 111     super.postPlay(move);
 112     if (move.vanish.length == 2 && move.vanish[1].p == V.KING)
 113       // We took opponent king (because if castle vanish[1] is a rook)
 114       this.kingPos[this.turn] = [-1, -1];
 115
 116     // Update lights for both colors:
 117     this.updateEnlightened();
 118   }
 119
 120   postUndo(move) {
 121     super.postUndo(move);
 122     if (move.vanish.length == 2 && move.vanish[1].p == V.KING)
 123       // Last move took opponent's king:
 124       this.kingPos[move.vanish[1].c] = [move.vanish[1].x, move.vanish[1].y];
 125
 126     // Update lights for both colors:
 127     this.updateEnlightened();
 128   }
 129
 130   getCurrentScore() {
 131     const color = this.turn;
 132     const kp = this.kingPos[color];
 133     if (kp[0] < 0)
 134       // King disappeared
 135       return color == "w" ? "0-1" : "1-0";
 136     // Assume that stalemate is impossible (I think so. Would need proof...)
 137     return "*";
 138   }
 139
 140   static get THRESHOLD_MATE() {
 141     return 500; //checkmates evals may be slightly below 1000
 142   }
 143
 144   // In this special situation, we just look 1 half move ahead
 145   getComputerMove() {
 146     const maxeval = V.INFINITY;
 147     const color = this.turn;
 148     const oppCol = V.GetOppCol(color);
 149     const pawnShift = color == "w" ? -1 : 1;
 150
 151     // Do not cheat: the current enlightment is all we can see
 152     const myLight = JSON.parse(JSON.stringify(this.enlightened[color]));
 153
 154     // Can a slider on (i,j) apparently take my king?
 155     // NOTE: inaccurate because assume yes if some squares are shadowed
 156     const sliderTake = ([i, j], piece) => {
 157       const kp = this.kingPos[color];
 158       let step = undefined;
 159       if (piece == V.BISHOP) {
 160         if (Math.abs(kp[0] - i) == Math.abs(kp[1] - j)) {
 161           step = [
 162             (i - kp[0]) / Math.abs(i - kp[0]),
 163             (j - kp[1]) / Math.abs(j - kp[1])
 164           ];
 165         }
 166       } else if (piece == V.ROOK) {
 167         if (kp[0] == i) step = [0, (j - kp[1]) / Math.abs(j - kp[1])];
 168         else if (kp[1] == j) step = [(i - kp[0]) / Math.abs(i - kp[0]), 0];
 169       }
 170       if (!step) return false;
 171       // Check for obstacles
 172       let obstacle = false;
 173       for (
 174         let x = kp[0] + step[0], y = kp[1] + step[1];
 175         x != i && y != j;
 176         x += step[0], y += step[1]
 177       ) {
 178         if (myLight[x][y] && this.board[x][y] != V.EMPTY) {
 179           obstacle = true;
 180           break;
 181         }
 182       }
 183       if (!obstacle) return true;
 184       return false;
 185     };
 186
 187     // Do I see something which can take my king ?
 188     const kingThreats = () => {
 189       const kp = this.kingPos[color];
 190       for (let i = 0; i < V.size.x; i++) {
 191         for (let j = 0; j < V.size.y; j++) {
 192           if (
 193             myLight[i][j] &&
 194             this.board[i][j] != V.EMPTY &&
 195             this.getColor(i, j) != color
 196           ) {
 197             switch (this.getPiece(i, j)) {
 198               case V.PAWN:
 199                 if (kp[0] + pawnShift == i && Math.abs(kp[1] - j) == 1)
 200                   return true;
 201                 break;
 202               case V.KNIGHT:
 203                 if (
 204                   (Math.abs(kp[0] - i) == 2 && Math.abs(kp[1] - j) == 1) ||
 205                   (Math.abs(kp[0] - i) == 1 && Math.abs(kp[1] - j) == 2)
 206                 ) {
 207                   return true;
 208                 }
 209                 break;
 210               case V.KING:
 211                 if (Math.abs(kp[0] - i) == 1 && Math.abs(kp[1] - j) == 1)
 212                   return true;
 213                 break;
 214               case V.BISHOP:
 215                 if (sliderTake([i, j], V.BISHOP)) return true;
 216                 break;
 217               case V.ROOK:
 218                 if (sliderTake([i, j], V.ROOK)) return true;
 219                 break;
 220               case V.QUEEN:
 221                 if (sliderTake([i, j], V.BISHOP) || sliderTake([i, j], V.ROOK))
 222                   return true;
 223                 break;
 224             }
 225           }
 226         }
 227       }
 228       return false;
 229     };
 230
 231     let moves = this.getAllValidMoves();
 232     for (let move of moves) {
 233       this.play(move);
 234       if (this.kingPos[oppCol][0] >= 0 && kingThreats()) {
 235         // We didn't take opponent king, and our king will be captured: bad
 236         move.eval = -maxeval;
 237       }
 238       this.undo(move);
 239
 240       if (move.eval) continue;
 241
 242       move.eval = 0; //a priori...
 243
 244       // Can I take something ? If yes, do it if it seems good...
 245       if (move.vanish.length == 2 && move.vanish[1].c != color) {
 246         // OK this isn't a castling move
 247         const myPieceVal = V.VALUES[move.appear[0].p];
 248         const hisPieceVal = V.VALUES[move.vanish[1].p];
 249         // Favor captures
 250         if (myPieceVal <= hisPieceVal)
 251           move.eval = hisPieceVal - myPieceVal + 1;
 252         else {
 253           // Taking a pawn with minor piece,
 254           // or minor piece or pawn with a rook,
 255           // or anything but a queen with a queen,
 256           // or anything with a king.
 257           move.eval = hisPieceVal - myPieceVal;
 258                       //Math.random() < 0.5 ? 1 : -1;
 259         }
 260       }
 261     }
 262
 263     // TODO: also need to implement the case when an opponent piece (in light)
 264     // is threatening something - maybe not the king, but e.g. pawn takes rook.
 265
 266     moves.sort((a, b) => b.eval - a.eval);
 267     let candidates = [0];
 268     for (let j = 1; j < moves.length && moves[j].eval == moves[0].eval; j++)
 269       candidates.push(j);
 270     return moves[candidates[randInt(candidates.length)]];
 271   }
 272 };