client/src/variants/Checkered.js

   1 // TODO: to detect oppositeMoves, we need last move --> encoded in FEN
   2 // + local moves stack (for AlphaBeta) + lastMove (in FEN)
   3
   4 import { ChessRules } from "@/base_rules";
   5
   6 export const VariantRules = class CheckeredRules extends ChessRules
   7 {
   8     static getPpath(b)
   9     {
  10         return b[0]=='c' ? "Checkered/"+b : b;
  11     }
  12
  13     static board2fen(b)
  14     {
  15         const checkered_codes = {
  16             'p': 's',
  17             'q': 't',
  18             'r': 'u',
  19             'b': 'c',
  20             'n': 'o',
  21         };
  22         if (b[0]=="c")
  23             return checkered_codes[b[1]];
  24         return ChessRules.board2fen(b);
  25     }
  26
  27     static fen2board(f)
  28     {
  29         // Tolerate upper-case versions of checkered pieces (why not?)
  30         const checkered_pieces = {
  31             's': 'p',
  32             'S': 'p',
  33             't': 'q',
  34             'T': 'q',
  35             'u': 'r',
  36             'U': 'r',
  37             'c': 'b',
  38             'C': 'b',
  39             'o': 'n',
  40             'O': 'n',
  41         };
  42         if (Object.keys(checkered_pieces).includes(f))
  43             return 'c'+checkered_pieces[f];
  44         return ChessRules.fen2board(f);
  45     }
  46
  47     static get PIECES()
  48     {
  49         return ChessRules.PIECES.concat(['s','t','u','c','o']);
  50     }
  51
  52     static IsGoodFlags(flags)
  53     {
  54         // 4 for castle + 16 for pawns
  55         return !!flags.match(/^[01]{20,20}$/);
  56     }
  57
  58     setFlags(fenflags)
  59     {
  60         super.setFlags(fenflags); //castleFlags
  61         this.pawnFlags =
  62         {
  63             "w": [...Array(8).fill(true)], //pawns can move 2 squares?
  64             "b": [...Array(8).fill(true)],
  65         };
  66         if (!fenflags)
  67             return;
  68         const flags = fenflags.substr(4); //skip first 4 digits, for castle
  69         for (let c of ['w','b'])
  70         {
  71             for (let i=0; i<8; i++)
  72                 this.pawnFlags[c][i] = (flags.charAt((c=='w'?0:8)+i) == '1');
  73         }
  74     }
  75
  76     aggregateFlags()
  77     {
  78         return [this.castleFlags, this.pawnFlags];
  79     }
  80
  81     disaggregateFlags(flags)
  82     {
  83         this.castleFlags = flags[0];
  84         this.pawnFlags = flags[1];
  85     }
  86
  87     canTake([x1,y1], [x2,y2])
  88     {
  89         const color1 = this.getColor(x1,y1);
  90         const color2 = this.getColor(x2,y2);
  91         // Checkered aren't captured
  92         return color1 != color2 && color2 != 'c' && (color1 != 'c' || color2 != this.turn);
  93     }
  94
  95     // Post-processing: apply "checkerization" of standard moves
  96     getPotentialMovesFrom([x,y])
  97     {
  98         let standardMoves = super.getPotentialMovesFrom([x,y]);
  99         const lastRank = this.turn == "w" ? 0 : 7;
 100         if (this.getPiece(x,y) == V.KING)
 101             return standardMoves; //king has to be treated differently (for castles)
 102         let moves = [];
 103         standardMoves.forEach(m => {
 104             if (m.vanish[0].p == V.PAWN)
 105             {
 106                 if (Math.abs(m.end.x-m.start.x)==2 && !this.pawnFlags[this.turn][m.start.y])
 107                     return; //skip forbidden 2-squares jumps
 108                 if (this.board[m.end.x][m.end.y] == V.EMPTY && m.vanish.length==2
 109                     && this.getColor(m.start.x,m.start.y) == 'c')
 110                 {
 111                     return; //checkered pawns cannot take en-passant
 112                 }
 113             }
 114             if (m.vanish.length == 1)
 115                 moves.push(m); //no capture
 116             else
 117             {
 118                 // A capture occured (m.vanish.length == 2)
 119                 m.appear[0].c = "c";
 120                 moves.push(m);
 121                 if (m.appear[0].p != m.vanish[1].p //avoid promotions (already treated):
 122                     && (m.vanish[0].p != V.PAWN || m.end.x != lastRank))
 123                 {
 124                     // Add transformation into captured piece
 125                     let m2 = JSON.parse(JSON.stringify(m));
 126                     m2.appear[0].p = m.vanish[1].p;
 127                     moves.push(m2);
 128                 }
 129             }
 130         });
 131         return moves;
 132     }
 133
 134     canIplay(side, [x,y])
 135     {
 136         return (side == this.turn && [side,'c'].includes(this.getColor(x,y)));
 137     }
 138
 139     // Does m2 un-do m1 ? (to disallow undoing checkered moves)
 140     oppositeMoves(m1, m2)
 141     {
 142         return m1.appear.length == 1 && m2.appear.length == 1
 143             && m1.vanish.length == 1 && m2.vanish.length == 1
 144             && m1.start.x == m2.end.x && m1.end.x == m2.start.x
 145             && m1.start.y == m2.end.y && m1.end.y == m2.start.y
 146             && m1.appear[0].c == m2.vanish[0].c && m1.appear[0].p == m2.vanish[0].p
 147             && m1.vanish[0].c == m2.appear[0].c && m1.vanish[0].p == m2.appear[0].p;
 148     }
 149
 150     filterValid(moves)
 151     {
 152         if (moves.length == 0)
 153             return [];
 154         const color = this.turn;
 155         return moves.filter(m => {
 156             const L = this.moves.length;
 157             if (L > 0 && this.oppositeMoves(this.moves[L-1], m))
 158                 return false;
 159             this.play(m);
 160             const res = !this.underCheck(color);
 161             this.undo(m);
 162             return res;
 163         });
 164     }
 165
 166     isAttackedByPawn([x,y], colors)
 167     {
 168         for (let c of colors)
 169         {
 170             const color = (c=="c" ? this.turn : c);
 171             let pawnShift = (color=="w" ? 1 : -1);
 172             if (x+pawnShift>=0 && x+pawnShift<8)
 173             {
 174                 for (let i of [-1,1])
 175                 {
 176                     if (y+i>=0 && y+i<8 && this.getPiece(x+pawnShift,y+i)==V.PAWN
 177                         && this.getColor(x+pawnShift,y+i)==c)
 178                     {
 179                         return true;
 180                     }
 181                 }
 182             }
 183         }
 184         return false;
 185     }
 186
 187     underCheck(color)
 188     {
 189         return this.isAttacked(this.kingPos[color], [V.GetOppCol(color),'c']);
 190     }
 191
 192     getCheckSquares(color)
 193     {
 194         // Artifically change turn, for checkered pawns
 195         this.turn = V.GetOppCol(color);
 196         const kingAttacked = this.isAttacked(
 197             this.kingPos[color], [V.GetOppCol(color),'c']);
 198         let res = kingAttacked
 199             ? [JSON.parse(JSON.stringify(this.kingPos[color]))] //need to duplicate!
 200             : [];
 201         this.turn = color;
 202         return res;
 203     }
 204
 205     updateVariables(move)
 206     {
 207         super.updateVariables(move);
 208         // Does this move turn off a 2-squares pawn flag?
 209         const secondRank = [1,6];
 210         if (secondRank.includes(move.start.x) && move.vanish[0].p == V.PAWN)
 211             this.pawnFlags[move.start.x==6 ? "w" : "b"][move.start.y] = false;
 212     }
 213
 214     getCurrentScore()
 215     {
 216     if (this.atLeastOneMove()) // game not over
 217       return "*";
 218
 219     const color = this.turn;
 220         // Artifically change turn, for checkered pawns
 221         this.turn = V.GetOppCol(this.turn);
 222         const res = this.isAttacked(this.kingPos[color], [V.GetOppCol(color),'c'])
 223             ? (color == "w" ? "0-1" : "1-0")
 224             : "1/2";
 225         this.turn = V.GetOppCol(this.turn);
 226         return res;
 227     }
 228
 229     evalPosition()
 230     {
 231         let evaluation = 0;
 232         //Just count material for now, considering checkered neutral (...)
 233         for (let i=0; i<V.size.x; i++)
 234         {
 235             for (let j=0; j<V.size.y; j++)
 236             {
 237                 if (this.board[i][j] != V.EMPTY)
 238                 {
 239                     const sqColor = this.getColor(i,j);
 240                     const sign = sqColor == "w" ? 1 : (sqColor=="b" ? -1 : 0);
 241                     evaluation += sign * V.VALUES[this.getPiece(i,j)];
 242                 }
 243             }
 244         }
 245         return evaluation;
 246     }
 247
 248     static GenRandInitFen()
 249     {
 250         const randFen = ChessRules.GenRandInitFen();
 251         // Add 16 pawns flags:
 252         return randFen.replace(" w 0 1111", " w 0 11111111111111111111");
 253     }
 254
 255     getFlagsFen()
 256     {
 257         let fen = super.getFlagsFen();
 258         // Add pawns flags
 259         for (let c of ['w','b'])
 260         {
 261             for (let i=0; i<8; i++)
 262                 fen += this.pawnFlags[c][i] ? '1' : '0';
 263         }
 264         return fen;
 265     }
 266
 267     getNotation(move)
 268     {
 269         if (move.appear.length == 2)
 270         {
 271             // Castle
 272             if (move.end.y < move.start.y)
 273                 return "0-0-0";
 274             else
 275                 return "0-0";
 276         }
 277
 278         // Translate final square
 279         const finalSquare = V.CoordsToSquare(move.end);
 280
 281         const piece = this.getPiece(move.start.x, move.start.y);
 282         if (piece == V.PAWN)
 283         {
 284             // Pawn move
 285             let notation = "";
 286             if (move.vanish.length > 1)
 287             {
 288                 // Capture
 289                 const startColumn = V.CoordToColumn(move.start.y);
 290                 notation = startColumn + "x" + finalSquare +
 291                     "=" + move.appear[0].p.toUpperCase();
 292             }
 293             else //no capture
 294             {
 295                 notation = finalSquare;
 296                 if (move.appear.length > 0 && piece != move.appear[0].p) //promotion
 297                     notation += "=" + move.appear[0].p.toUpperCase();
 298             }
 299             return notation;
 300         }
 301
 302         else
 303         {
 304             // Piece movement
 305             return piece.toUpperCase() + (move.vanish.length > 1 ? "x" : "") + finalSquare
 306                 + (move.vanish.length > 1 ? "=" + move.appear[0].p.toUpperCase() : "");
 307         }
 308     }
 309 }