-//https://www.chessvariants.com/diffmove.dir/switching.html
class SwitchingRules extends ChessRules
{
- //TODO:
- // Move completion: promote switched pawns (as in Magnetic)
+ // Build switch move between squares x1,y1 and x2,y2
+ getSwitchMove_s([x1,y1],[x2,y2])
+ {
- // To every piece potential moves: add switchings
+ const c = this.getColor(x1,y1); //same as color at square 2
+ const p1 = this.getPiece(x1,y1);
+ const p2 = this.getPiece(x2,y2);
+ let move = new Move({
+ appear: [
+ new PiPo({x:x2,y:y2,c:c,p:p1}),
+ new PiPo({x:x1,y:y1,c:c,p:p2})
+ ],
+ vanish: [
+ new PiPo({x:x1,y:y1,c:c,p:p1}),
+ new PiPo({x:x2,y:y2,c:c,p:p2})
+ ],
+ start: {x:x1,y:y1},
+ end: {x:x2,y:y2}
+ });
+ // Move completion: promote switched pawns (as in Magnetic)
+ const sizeX = VariantRules.size[0];
+ const lastRank = (c == "w" ? 0 : sizeX-1);
+ const V = VariantRules;
+ let moves = [];
+ if (p1==V.PAWN && x2==lastRank) //TODO: also the case p2==V.PAWN and x1==lastRank! see Magnetic chess
+ {
+ move.appear[0].p = V.ROOK;
+ moves.push(move);
+ for (let piece of [V.KNIGHT, V.BISHOP, V.QUEEN])
+ {
+ let cmove = JSON.parse(JSON.stringify(move));
+ cmove.appear[0].p = piece;
+ moves.push(cmove);
+ }
+ }
+ else //other cases
+ moves.push(move);
+ return moves;
+ }
- // Prevent king switching if under check
+ getPotentialMovesFrom([x,y])
+ {
+ let moves = super.getPotentialMovesFrom([x,y]);
+ // Add switches:
+ const V = VariantRules;
+ const color = this.turn;
+ const piece = this.getPiece(x,y);
+ const [sizeX,sizeY] = V.size;
+ const steps = V.steps[V.ROOK].concat(V.steps[V.BISHOP]);
+ const kp = this.kingPos[color];
+ const oppCol = this.getOppCol(color);
+ for (let step of steps)
+ {
+ let [i,j] = [x+step[0],y+step[1]];
+ if (i>=0 && i<sizeX && j>=0 && j<sizeY && this.board[i][j]!=V.EMPTY
+ && this.getColor(i,j)==color && this.getPiece(i,j)!=piece
+ // No switching under check (theoretically non-king pieces could, but not)
+ && !this.isAttacked(kp, [oppCol]))
+ {
+ let switchMove_s = this.getSwitchMove_s([x,y],[i,j]);
+ if (switchMove_s.length == 1)
+ moves.push(switchMove_s[0]);
+ else //promotion
+ moves = moves.concat(switchMove_s);
+ }
+ }
+ return moves;
+ }
+
+ static get SEARCH_DEPTH() { return 2; } //branching factor is quite high
}