client/src/variants/Upsidedown.js

   1 import { ChessRules } from "@/base_rules";
   2 import { randInt } from "@/utils/alea";
   3 import { ArrayFun } from "@/utils/array";
   4
   5 export class UpsidedownRules extends ChessRules {
   6   static get HasFlags() {
   7     return false;
   8   }
   9
  10   static get HasEnpassant() {
  11     return false;
  12   }
  13
  14   static GenRandInitFen(randomness) {
  15     if (randomness == 0)
  16       return "RNBQKBNR/PPPPPPPP/8/8/8/8/pppppppp/rnbqkbnr w 0";
  17
  18     let pieces = { w: new Array(8), b: new Array(8) };
  19     for (let c of ["w", "b"]) {
  20       if (c == 'b' && randomness == 1) {
  21         pieces['b'] = pieces['w'];
  22         break;
  23       }
  24
  25       let positions = ArrayFun.range(8);
  26
  27       let randIndex = randInt(8);
  28       const kingPos = positions[randIndex];
  29       positions.splice(randIndex, 1);
  30
  31       // At least a knight must be next to the king:
  32       let knight1Pos = undefined;
  33       if (kingPos == 0) knight1Pos = 1;
  34       else if (kingPos == V.size.y - 1) knight1Pos = V.size.y - 2;
  35       else knight1Pos = kingPos + (Math.random() < 0.5 ? 1 : -1);
  36       // Search for knight1Pos index in positions and remove it
  37       const knight1Index = positions.indexOf(knight1Pos);
  38       positions.splice(knight1Index, 1);
  39
  40       // King+knight1 are on two consecutive squares: one light, one dark
  41       randIndex = 2 * randInt(3);
  42       const bishop1Pos = positions[randIndex];
  43       let randIndex_tmp = 2 * randInt(3) + 1;
  44       const bishop2Pos = positions[randIndex_tmp];
  45       positions.splice(Math.max(randIndex, randIndex_tmp), 1);
  46       positions.splice(Math.min(randIndex, randIndex_tmp), 1);
  47
  48       randIndex = randInt(4);
  49       const knight2Pos = positions[randIndex];
  50       positions.splice(randIndex, 1);
  51
  52       randIndex = randInt(3);
  53       const queenPos = positions[randIndex];
  54       positions.splice(randIndex, 1);
  55
  56       const rook1Pos = positions[0];
  57       const rook2Pos = positions[1];
  58
  59       pieces[c][rook1Pos] = "r";
  60       pieces[c][knight1Pos] = "n";
  61       pieces[c][bishop1Pos] = "b";
  62       pieces[c][queenPos] = "q";
  63       pieces[c][kingPos] = "k";
  64       pieces[c][bishop2Pos] = "b";
  65       pieces[c][knight2Pos] = "n";
  66       pieces[c][rook2Pos] = "r";
  67     }
  68     return (
  69       pieces["w"].join("").toUpperCase() +
  70       "/PPPPPPPP/8/8/8/8/pppppppp/" +
  71       pieces["b"].join("") +
  72       // No castle, no en-passant:
  73       " w 0"
  74     );
  75   }
  76
  77   static get SEARCH_DEPTH() {
  78     return 2;
  79   }
  80 };