--- /dev/null
+import { ChessRules, PiPo, Move } from "@/base_rules";
+
+export const VariantRules = class EnpassantRules extends ChessRules {
+
+ static IsGoodEnpassant(enpassant) {
+ if (enpassant != "-") {
+ const squares = enpassant.split(",");
+ for (let sq of squares) {
+ const ep = V.SquareToCoords(sq);
+ if (isNaN(ep.x) || !V.OnBoard(ep)) return false;
+ }
+ }
+ return true;
+ }
+
+ getEpSquare(moveOrSquare) {
+ if (!moveOrSquare) return undefined;
+ if (typeof moveOrSquare === "string") {
+ const square = moveOrSquare;
+ if (square == "-") return undefined;
+ let res = [];
+ square.split(",").forEach(sq => {
+ res.push(V.SquareToCoords(sq));
+ });
+ return res;
+ }
+ // Argument is a move: all intermediate squares are en-passant candidates,
+ // except if the moving piece is a king.
+ const move = moveOrSquare;
+ const piece = move.appear[0].p;
+ if (piece == V.KING ||
+ (
+ Math.abs(move.end.x-move.start.x) <= 1 &&
+ Math.abs(move.end.y-move.start.y) <= 1
+ )
+ ) {
+ return undefined;
+ }
+ const delta = [move.end.x-move.start.x, move.end.y-move.start.y];
+ let step = undefined;
+ if (piece == V.KNIGHT) {
+ const divisor = Math.min(Math.abs(delta[0]), Math.abs(delta[1]));
+ step = [delta[0]/divisor || 0, delta[1]/divisor || 0];
+ } else {
+ step = [delta[0]/Math.abs(delta[0]) || 0, delta[1]/Math.abs(delta[1]) || 0];
+ }
+ let res = [];
+ for (
+ let [x,y] = [move.start.x+step[0],move.start.y+step[1]];
+ x != move.end.x || y != move.end.y;
+ x += step[0], y += step[1]
+ ) {
+ res.push({x:x, y:y});
+ }
+ // Add final square to know which piece is taken en passant:
+ res.push(move.end);
+ return res;
+ }
+
+ getEnpassantFen() {
+ const L = this.epSquares.length;
+ if (!this.epSquares[L - 1]) return "-"; //no en-passant
+ let res = "";
+ this.epSquares[L - 1].forEach(sq => {
+ res += V.CoordsToSquare(sq) + ",";
+ });
+ return res.slice(0, -1); //remove last comma
+ }
+
+ // TODO: this getPotentialPawnMovesFrom() is mostly duplicated:
+ // it could be split in "capture", "promotion", "enpassant"...
+ getPotentialPawnMoves([x, y]) {
+ const color = this.turn;
+ let moves = [];
+ const [sizeX, sizeY] = [V.size.x, V.size.y];
+ const shiftX = color == "w" ? -1 : 1;
+ const firstRank = color == "w" ? sizeX - 1 : 0;
+ const startRank = color == "w" ? sizeX - 2 : 1;
+ const lastRank = color == "w" ? 0 : sizeX - 1;
+ const pawnColor = this.getColor(x, y); //can be different for checkered
+
+ // NOTE: next condition is generally true (no pawn on last rank)
+ if (x + shiftX >= 0 && x + shiftX < sizeX) {
+ const finalPieces =
+ x + shiftX == lastRank
+ ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN]
+ : [V.PAWN];
+ // One square forward
+ if (this.board[x + shiftX][y] == V.EMPTY) {
+ for (let piece of finalPieces) {
+ moves.push(
+ this.getBasicMove([x, y], [x + shiftX, y], {
+ c: pawnColor,
+ p: piece
+ })
+ );
+ }
+ // Next condition because pawns on 1st rank can generally jump
+ if (
+ [startRank, firstRank].includes(x) &&
+ this.board[x + 2 * shiftX][y] == V.EMPTY
+ ) {
+ // Two squares jump
+ moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
+ }
+ }
+ // Captures
+ for (let shiftY of [-1, 1]) {
+ if (
+ y + shiftY >= 0 &&
+ y + shiftY < sizeY &&
+ this.board[x + shiftX][y + shiftY] != V.EMPTY &&
+ this.canTake([x, y], [x + shiftX, y + shiftY])
+ ) {
+ for (let piece of finalPieces) {
+ moves.push(
+ this.getBasicMove([x, y], [x + shiftX, y + shiftY], {
+ c: pawnColor,
+ p: piece
+ })
+ );
+ }
+ }
+ }
+ }
+
+ // En passant
+ const Lep = this.epSquares.length;
+ const squares = this.epSquares[Lep - 1];
+ if (!!squares) {
+ const S = squares.length;
+ const taken = squares[S-1];
+ const pipoV = new PiPo({
+ x: taken.x,
+ y: taken.y,
+ p: this.getPiece(taken.x, taken.y),
+ c: this.getColor(taken.x, taken.y)
+ });
+ [...Array(S-1).keys()].forEach(i => {
+ const sq = squares[i];
+ if (sq.x == x + shiftX && Math.abs(sq.y - y) == 1) {
+ let enpassantMove = this.getBasicMove([x, y], [sq.x, sq.y]);
+ enpassantMove.vanish.push(pipoV);
+ moves.push(enpassantMove);
+ }
+ });
+ }
+
+ return moves;
+ }
+
+ // Remove the "onestep" condition: knight promote to knightrider:
+
+ getPotentialKnightMoves(sq) {
+ return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT]);
+ }
+
+ isAttackedByKnight(sq, colors) {
+ return this.isAttackedBySlideNJump(
+ sq,
+ colors,
+ V.KNIGHT,
+ V.steps[V.KNIGHT]
+ );
+ }
+
+ getPotentialMovesFrom([x, y]) {
+ let moves = super.getPotentialMovesFrom([x,y]);
+ // Add en-passant captures from this square:
+ const L = this.epSquares.length;
+ if (!this.epSquares[L - 1]) return moves;
+ const squares = this.epSquares[L - 1];
+ const S = squares.length;
+ // Object describing the removed opponent's piece:
+ const pipoV = new PiPo({
+ x: squares[S-1].x,
+ y: squares[S-1].y,
+ c: V.GetOppCol(this.turn),
+ p: this.getPiece(squares[S-1].x, squares[S-1].y)
+ });
+ // Check if existing non-capturing moves could also capture en passant
+ moves.forEach(m => {
+ if (
+ m.appear[0].p != V.PAWN && //special pawn case is handled elsewhere
+ m.vanish.length <= 1 &&
+ [...Array(S-1).keys()].some(i => {
+ return m.end.x == squares[i].x && m.end.y == squares[i].y;
+ })
+ ) {
+ m.vanish.push(pipoV);
+ }
+ });
+ // Special case of the king knight's movement:
+ if (this.getPiece(x, y) == V.KING) {
+ V.steps[V.KNIGHT].forEach(step => {
+ const endX = x + step[0];
+ const endY = y + step[1];
+ if (
+ V.OnBoard(endX, endY) &&
+ [...Array(S-1).keys()].some(i => {
+ return endX == squares[i].x && endY == squares[i].y;
+ })
+ ) {
+ let enpassantMove = this.getBasicMove([x, y], [endX, endY]);
+ enpassantMove.vanish.push(pipoV);
+ moves.push(enpassantMove);
+ }
+ });
+ }
+ return moves;
+ }
+
+ static get VALUES() {
+ return {
+ p: 1,
+ r: 5,
+ n: 4,
+ b: 3,
+ q: 9,
+ k: 1000
+ };
+ }
+};
projects / vchess.git / blobdiff