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
   7   static get HasFlags() {
   8     return false;
   9   }
  10
  11   static get HasEnpassant() {
  12     return false;
  13   }
  14
  15   static GenRandInitFen(options) {
  16     if (options.randomness == 0)
  17       return "RNBQKBNR/PPPPPPPP/8/8/8/8/pppppppp/rnbqkbnr w 0";
  18
  19     let pieces = { w: new Array(8), b: new Array(8) };
  20     for (let c of ["w", "b"]) {
  21       if (c == 'b' && options.randomness == 1) {
  22         pieces['b'] = pieces['w'];
  23         break;
  24       }
  25
  26       let positions = ArrayFun.range(8);
  27
  28       let randIndex = randInt(8);
  29       const kingPos = positions[randIndex];
  30       positions.splice(randIndex, 1);
  31
  32       // At least a knight must be next to the king:
  33       let knight1Pos = undefined;
  34       if (kingPos == 0) knight1Pos = 1;
  35       else if (kingPos == V.size.y - 1) knight1Pos = V.size.y - 2;
  36       else knight1Pos = kingPos + (Math.random() < 0.5 ? 1 : -1);
  37       // Search for knight1Pos index in positions and remove it
  38       const knight1Index = positions.indexOf(knight1Pos);
  39       positions.splice(knight1Index, 1);
  40
  41       // King+knight1 are on two consecutive squares: one light, one dark
  42       randIndex = 2 * randInt(3);
  43       const bishop1Pos = positions[randIndex];
  44       let randIndex_tmp = 2 * randInt(3) + 1;
  45       const bishop2Pos = positions[randIndex_tmp];
  46       positions.splice(Math.max(randIndex, randIndex_tmp), 1);
  47       positions.splice(Math.min(randIndex, randIndex_tmp), 1);
  48
  49       randIndex = randInt(4);
  50       const knight2Pos = positions[randIndex];
  51       positions.splice(randIndex, 1);
  52
  53       randIndex = randInt(3);
  54       const queenPos = positions[randIndex];
  55       positions.splice(randIndex, 1);
  56
  57       const rook1Pos = positions[0];
  58       const rook2Pos = positions[1];
  59
  60       pieces[c][rook1Pos] = "r";
  61       pieces[c][knight1Pos] = "n";
  62       pieces[c][bishop1Pos] = "b";
  63       pieces[c][queenPos] = "q";
  64       pieces[c][kingPos] = "k";
  65       pieces[c][bishop2Pos] = "b";
  66       pieces[c][knight2Pos] = "n";
  67       pieces[c][rook2Pos] = "r";
  68     }
  69     return (
  70       pieces["w"].join("").toUpperCase() +
  71       "/PPPPPPPP/8/8/8/8/pppppppp/" +
  72       pieces["b"].join("") +
  73       // No castle, no en-passant:
  74       " w 0"
  75     );
  76   }
  77
  78   static get SEARCH_DEPTH() {
  79     return 2;
  80   }
  81
  82 };