utils/setupPieces.js

   1 import {Random} from "/utils/alea.js";
   2
   3 export class FenUtil = {
   4
   5   // arg o (constraints): "between" with p1 and p2.
   6   //                      "flags", "diffCol": array of pieceType
   7   setupRow(arr, o) {
   8     let res = JSON.parse(JSON.stringify(arr));
   9     if (o.randomness >= 1)
  10       res = Random.shuffle(arr);
  11     let flags = "";
  12     if (o.flags) {
  13       res.forEach((p, i) => {
  14         if (o.flags.includes(p))
  15           flags += i;
  16       });
  17     }
  18     if (o.diffCol) {
  19       o.diffCol.forEach(p => {
  20         // Pieces of type p on different colors:
  21         const firstP = res.indexOf(p),
  22               lastP = res.lastIndexOf(p);
  23         if ((firstP - lastP) % 2 != 0) {
  24           const choice1 = Random.randBool() ? firstP : lastP;
  25           let choice2;
  26           do {
  27             choice2 = Random.randInt(arr.length);
  28           }
  29           while (
  30             choice2 == choice1 ||
  31             o.diffCol.includes(choice2) ||
  32             (choice2 - choice1) % 2 != 0
  33           );
  34           res[choice1] = res[choice2];
  35           res[choice2] = p;
  36         }
  37       });
  38     }
  39     if (o.between) {
  40       // Locate p1. If appearing first, exchange with first p2.
  41       // If appearing last, exchange with last p2.
  42       const p1 = res.indexOf(o.between["p1"]);
  43       const firstP2 = res.indexOf(o.between["p2"]),
  44             lastP2 = res.lastIndexOf(o.between["p2"]);
  45       if (p1 < firstP2 || p1 > lastP2) {
  46         res[p1] = o.between["p2"];
  47         if (p1 < firstP2)
  48           res[firstP2] = o.between["p1"];
  49         else //p1 > lastP2
  50           res[lastP2] = o.between["p1"];
  51       }
  52     }
  53     return {fen: res, flags: flags};
  54   }
  55
  56   setupPieces(arr, o) {
  57     const row1 = FenUtil.setupRow(arr, o);
  58     const row2 = o.randomness == 2 ? FenUtil.setupRow(arr, o) : row1;
  59     return {
  60       w: row1.fen,
  61       b: row2.fen,
  62       flags: row1.flags + row2.flags
  63     };
  64   }
  65
  66 };