--- /dev/null
+import { ChessRules } from "@/base_rules";
+
+export const VariantRules = class Knightrelay2Rules extends ChessRules {
+ getPotentialMovesFrom([x, y]) {
+ let moves = super.getPotentialMovesFrom([x, y]);
+
+ // Expand possible moves if guarded by a knight:
+ const piece = this.getPiece(x,y);
+ if (piece != V.KNIGHT) {
+ const color = this.turn;
+ let guardedByKnight = false;
+ for (const step of V.steps[V.KNIGHT]) {
+ if (
+ V.OnBoard(x+step[0],y+step[1]) &&
+ this.getPiece(x+step[0],y+step[1]) == V.KNIGHT &&
+ this.getColor(x+step[0],y+step[1]) == color
+ ) {
+ guardedByKnight = true;
+ break;
+ }
+ }
+ if (guardedByKnight) {
+ const lastRank = color == "w" ? 0 : V.size.x - 1;
+ for (const step of V.steps[V.KNIGHT]) {
+ if (
+ V.OnBoard(x+step[0],y+step[1]) &&
+ this.getColor(x+step[0],y+step[1]) != color
+ ) {
+ // Potential promotions:
+ const finalPieces = piece == V.PAWN && x + step[0] == lastRank
+ ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN]
+ : [piece];
+ for (let p of finalPieces) {
+ moves.push(
+ this.getBasicMove([x,y], [x+step[0],y+step[1]], {
+ c: color,
+ p: p
+ })
+ );
+ }
+ }
+ }
+ }
+ }
+
+ return moves;
+ }
+
+ isAttacked(sq, color) {
+ if (super.isAttacked(sq, color)) return true;
+
+ // Check if a (non-knight) piece at knight distance
+ // is guarded by a knight (and thus attacking)
+ const x = sq[0],
+ y = sq[1];
+ for (const step of V.steps[V.KNIGHT]) {
+ if (
+ V.OnBoard(x+step[0],y+step[1]) &&
+ this.getColor(x+step[0],y+step[1]) == color &&
+ this.getPiece(x+step[0],y+step[1]) != V.KNIGHT
+ ) {
+ for (const step2 of V.steps[V.KNIGHT]) {
+ const xx = x+step[0]+step2[0],
+ yy = y+step[1]+step2[1];
+ if (
+ V.OnBoard(xx,yy) &&
+ this.getColor(xx,yy) == color &&
+ this.getPiece(xx,yy) == V.KNIGHT
+ ) {
+ return true;
+ }
+ }
+ }
+ }
+
+ return false;
+ }
+
+ static get VALUES() {
+ return {
+ p: 1,
+ r: 5,
+ n: 7, //the knight is valuable
+ b: 3,
+ q: 9,
+ k: 1000
+ };
+ }
+
+ static get SEARCH_DEPTH() {
+ return 2;
+ }
+
+ getNotation(move) {
+ if (move.appear.length == 2 && move.appear[0].p == V.KING)
+ // Castle
+ return move.end.y < move.start.y ? "0-0-0" : "0-0";
+
+ // Translate final and initial square
+ const initSquare = V.CoordsToSquare(move.start);
+ const finalSquare = V.CoordsToSquare(move.end);
+ const piece = this.getPiece(move.start.x, move.start.y);
+
+ // Since pieces and pawns could move like knight, indicate start and end squares
+ let notation =
+ piece.toUpperCase() +
+ initSquare +
+ (move.vanish.length > move.appear.length ? "x" : "") +
+ finalSquare
+
+ if (
+ piece == V.PAWN &&
+ move.appear.length > 0 &&
+ move.appear[0].p != V.PAWN
+ ) {
+ // Promotion
+ notation += "=" + move.appear[0].p.toUpperCase();
+ }
+
+ return notation;
+ }
+};