+ getEpSquare(moveOrSquare) {
+ if (!moveOrSquare) return undefined;
+ if (typeof moveOrSquare === "string") {
+ const square = moveOrSquare;
+ if (square == "-") return undefined;
+ return V.SquareToCoords(square);
+ }
+ // Argument is a move:
+ const move = moveOrSquare;
+ const s = move.start,
+ e = move.end;
+ if (
+ s.y == e.y &&
+ Math.abs(s.x - e.x) == 2 &&
+ // Special conditions: a pawn can be on the other side
+ ['p','s'].includes(move.appear[0].p) &&
+ ['p','s'].includes(move.vanish[0].p)
+ ) {
+ return {
+ x: (s.x + e.x) / 2,
+ y: s.y
+ };
+ }
+ return undefined; //default
+ }
+
+ // king can be l or L (on the other mirror side)
+ static IsGoodPosition(position) {
+ if (position.length == 0) return false;
+ const rows = position.split("/");
+ if (rows.length != V.size.x) return false;
+ let kings = { "k": 0, "K": 0, 'l': 0, 'L': 0 };
+ for (let row of rows) {
+ let sumElts = 0;
+ for (let i = 0; i < row.length; i++) {
+ if (['K','k','L','l'].includes(row[i])) kings[row[i]]++;
+ if (V.PIECES.includes(row[i].toLowerCase())) sumElts++;
+ else {
+ const num = parseInt(row[i]);
+ if (isNaN(num)) return false;
+ sumElts += num;
+ }
+ }
+ if (sumElts != V.size.y) return false;
+ }
+ if (kings['k'] + kings['l'] != 1 || kings['K'] + kings['L'] != 1)
+ return false;
+ return true;
+ }
+