client/src/variants/Upsidedown.js

   1 class UpsidedownRules extends ChessRules
   2 {
   3     static get HasFlags() { return false; }
   4
   5     static get HasEnpassant() { return false; }
   6
   7     getPotentialKingMoves(sq)
   8     {
   9         // No castle
  10         return this.getSlideNJumpMoves(sq,
  11             V.steps[V.ROOK].concat(V.steps[V.BISHOP]), "oneStep");
  12     }
  13
  14     static GenRandInitFen()
  15     {
  16         let pieces = { "w": new Array(8), "b": new Array(8) };
  17         for (let c of ["w","b"])
  18         {
  19             let positions = range(8);
  20
  21             let randIndex = random(8);
  22             const kingPos = positions[randIndex];
  23             positions.splice(randIndex, 1);
  24
  25             // At least a knight must be next to the king:
  26             let knight1Pos = undefined;
  27             if (kingPos == 0)
  28                 knight1Pos = 1;
  29             else if (kingPos == V.size.y-1)
  30                 knight1Pos = V.size.y-2;
  31             else
  32                 knight1Pos = kingPos + (Math.random() < 0.5 ? 1 : -1);
  33             // Search for knight1Pos index in positions and remove it
  34             const knight1Index = positions.indexOf(knight1Pos);
  35             positions.splice(knight1Index, 1);
  36
  37             // King+knight1 are on two consecutive squares: one light, one dark
  38             randIndex = 2 * random(3);
  39             const bishop1Pos = positions[randIndex];
  40             let randIndex_tmp = 2 * random(3) + 1;
  41             const bishop2Pos = positions[randIndex_tmp];
  42             positions.splice(Math.max(randIndex,randIndex_tmp), 1);
  43             positions.splice(Math.min(randIndex,randIndex_tmp), 1);
  44
  45             randIndex = random(4);
  46             const knight2Pos = positions[randIndex];
  47             positions.splice(randIndex, 1);
  48
  49             randIndex = random(3);
  50             const queenPos = positions[randIndex];
  51             positions.splice(randIndex, 1);
  52
  53             const rook1Pos = positions[0];
  54             const rook2Pos = positions[1];
  55
  56             pieces[c][rook1Pos] = 'r';
  57             pieces[c][knight1Pos] = 'n';
  58             pieces[c][bishop1Pos] = 'b';
  59             pieces[c][queenPos] = 'q';
  60             pieces[c][kingPos] = 'k';
  61             pieces[c][bishop2Pos] = 'b';
  62             pieces[c][knight2Pos] = 'n';
  63             pieces[c][rook2Pos] = 'r';
  64         }
  65         return pieces["w"].join("").toUpperCase() +
  66             "/PPPPPPPP/8/8/8/8/pppppppp/" +
  67             pieces["b"].join("") +
  68             " w"; //no castle, no en-passant
  69     }
  70 }