--- /dev/null
+import { ChessRules } from "@/base_rules";
+import { randInt } from "@/utils/alea";
+
+export class Doublemove2Rules extends ChessRules {
+ static IsGoodEnpassant(enpassant) {
+ const squares = enpassant.split(",");
+ if (squares.length > 2) return false;
+ for (let sq of squares) {
+ if (sq != "-") {
+ const ep = V.SquareToCoords(sq);
+ if (isNaN(ep.x) || !V.OnBoard(ep)) return false;
+ }
+ }
+ return true;
+ }
+
+ // There may be 2 enPassant squares (if 2 pawns jump 2 squares in same turn)
+ getEnpassantFen() {
+ return this.epSquares[this.epSquares.length - 1].map(
+ epsq => epsq === undefined
+ ? "-" //no en-passant
+ : V.CoordsToSquare(epsq)
+ ).join(",");
+ }
+
+ setOtherVariables(fen) {
+ const parsedFen = V.ParseFen(fen);
+ this.setFlags(parsedFen.flags);
+ this.epSquares = [parsedFen.enpassant.split(",").map(sq => {
+ if (sq != "-") return V.SquareToCoords(sq);
+ return undefined;
+ })];
+ this.scanKings(fen);
+ // Extract subTurn from turn indicator: "w" (first move), or
+ // "w1" or "w2" white subturn 1 or 2, and same for black
+ this.turn = parsedFen.turn;
+ this.subTurn = 1;
+ }
+
+ getEnpassantCaptures([x, y], shiftX) {
+ let moves = [];
+ // En passant: always OK if subturn 1,
+ // OK on subturn 2 only if enPassant was played at subturn 1
+ // (and if there are two e.p. squares available).
+ const Lep = this.epSquares.length;
+ const epSquares = this.epSquares[Lep - 1]; //always at least one element
+ let epSqs = [];
+ epSquares.forEach(sq => {
+ if (sq) epSqs.push(sq);
+ });
+ if (epSqs.length == 0) return moves;
+ const oppCol = V.GetOppCol(this.getColor(x, y));
+ for (let sq of epSqs) {
+ if (
+ this.subTurn == 1 ||
+ (epSqs.length == 2 &&
+ // Was this en-passant capture already played at subturn 1 ?
+ // (Or maybe the opponent filled the en-passant square with a piece)
+ this.board[epSqs[0].x][epSqs[0].y] != V.EMPTY)
+ ) {
+ if (
+ sq.x == x + shiftX &&
+ Math.abs(sq.y - y) == 1 &&
+ // Add condition "enemy pawn must be present"
+ this.getPiece(x, sq.y) == V.PAWN &&
+ this.getColor(x, sq.y) == oppCol
+ ) {
+ let epMove = this.getBasicMove([x, y], [sq.x, sq.y]);
+ epMove.vanish.push({
+ x: x,
+ y: sq.y,
+ p: "p",
+ c: oppCol
+ });
+ moves.push(epMove);
+ }
+ }
+ }
+ return moves;
+ }
+
+ isAttacked(sq, color, castling) {
+ const singleMoveAttack = super.isAttacked(sq, color);
+ if (singleMoveAttack) return true;
+ if (!!castling) {
+ if (this.subTurn == 1)
+ // Castling at move 1 could be done into check
+ return false;
+ return singleMoveAttack;
+ }
+ // Double-move allowed:
+ const curTurn = this.turn;
+ this.turn = color;
+ const moves1 = super.getAllPotentialMoves();
+ this.turn = curTurn;
+ for (let move of moves1) {
+ this.play(move);
+ const res = super.isAttacked(sq, color);
+ this.undo(move);
+ if (res) return res;
+ }
+ return false;
+ }
+
+ filterValid(moves) {
+ if (this.subTurn == 1) {
+ return moves.filter(m1 => {
+ this.play(m1);
+ // NOTE: no recursion because next call will see subTurn == 2
+ const res = super.atLeastOneMove();
+ this.undo(m1);
+ return res;
+ });
+ }
+ return super.filterValid(moves);
+ }
+
+ play(move) {
+ move.flags = JSON.stringify(this.aggregateFlags());
+ V.PlayOnBoard(this.board, move);
+ const epSq = this.getEpSquare(move);
+ if (this.subTurn == 2) {
+ let lastEpsq = this.epSquares[this.epSquares.length - 1];
+ lastEpsq.push(epSq);
+ this.turn = V.GetOppCol(this.turn);
+ }
+ else {
+ this.epSquares.push([epSq]);
+ this.movesCount++;
+ if (this.movesCount == 1) this.turn = "b";
+ }
+ if (this.movesCount > 1) this.subTurn = 3 - this.subTurn;
+ this.postPlay(move);
+ }
+
+ postPlay(move) {
+ const c = move.vanish[0].c;
+ const piece = move.vanish[0].p;
+ const firstRank = c == "w" ? V.size.x - 1 : 0;
+
+ if (piece == V.KING && move.appear.length > 0) {
+ this.kingPos[c][0] = move.appear[0].x;
+ this.kingPos[c][1] = move.appear[0].y;
+ this.castleFlags[c] = [V.size.y, V.size.y];
+ return;
+ }
+ const oppCol = V.GetOppCol(c);
+ const oppFirstRank = V.size.x - 1 - firstRank;
+ if (
+ move.start.x == firstRank && //our rook moves?
+ this.castleFlags[c].includes(move.start.y)
+ ) {
+ const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
+ this.castleFlags[c][flagIdx] = V.size.y;
+ } else if (
+ move.end.x == oppFirstRank && //we took opponent rook?
+ this.castleFlags[oppCol].includes(move.end.y)
+ ) {
+ const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
+ this.castleFlags[oppCol][flagIdx] = V.size.y;
+ }
+ }
+
+ undo(move) {
+ this.disaggregateFlags(JSON.parse(move.flags));
+ V.UndoOnBoard(this.board, move);
+ if (this.subTurn == 2 || this.movesCount == 1) {
+ this.epSquares.pop();
+ this.movesCount--;
+ if (this.movesCount == 0) this.turn = "w";
+ }
+ else {
+ let lastEpsq = this.epSquares[this.epSquares.length - 1];
+ lastEpsq.pop();
+ this.turn = V.GetOppCol(this.turn);
+ }
+ if (this.movesCount > 0) this.subTurn = 3 - this.subTurn;
+ super.postUndo(move);
+ }
+
+ static get VALUES() {
+ return {
+ p: 1,
+ r: 5,
+ n: 3,
+ b: 3,
+ q: 7, //slightly less than in orthodox game
+ k: 1000
+ };
+ }
+
+ // No alpha-beta here, just adapted min-max at depth 2(+1)
+ getComputerMove() {
+ const maxeval = V.INFINITY;
+ const color = this.turn;
+ const oppCol = V.GetOppCol(this.turn);
+
+ // Search best (half) move for opponent turn
+ const getBestMoveEval = () => {
+ let score = this.getCurrentScore();
+ if (score != "*") {
+ if (score == "1/2") return 0;
+ return maxeval * (score == "1-0" ? 1 : -1);
+ }
+ let moves = this.getAllValidMoves();
+ let res = oppCol == "w" ? -maxeval : maxeval;
+ for (let m of moves) {
+ this.play(m);
+ score = this.getCurrentScore();
+ // Now turn is oppCol,2
+ if (score != "*") {
+ if (score == "1/2")
+ res = oppCol == "w" ? Math.max(res, 0) : Math.min(res, 0);
+ else {
+ // King captured
+ this.undo(m);
+ return maxeval * (score == "1-0" ? 1 : -1);
+ }
+ }
+ const evalPos = this.evalPosition();
+ res = oppCol == "w" ? Math.max(res, evalPos) : Math.min(res, evalPos);
+ this.undo(m);
+ }
+ return res;
+ };
+
+ let moves11 = this.getAllValidMoves();
+ let doubleMoves = [];
+ // Rank moves using a min-max at depth 2(+1)
+ for (let i = 0; i < moves11.length; i++) {
+ this.play(moves11[i]);
+ let moves12 = this.getAllValidMoves();
+ for (let j = 0; j < moves12.length; j++) {
+ this.play(moves12[j]);
+ doubleMoves.push({
+ moves: [moves11[i], moves12[j]],
+ eval: getBestMoveEval()
+ });
+ this.undo(moves12[j]);
+ }
+ this.undo(moves11[i]);
+ }
+
+ doubleMoves.sort((a, b) => {
+ return (color == "w" ? 1 : -1) * (b.eval - a.eval);
+ });
+ let candidates = [0]; //indices of candidates moves
+ for (
+ let i = 1;
+ i < doubleMoves.length && doubleMoves[i].eval == doubleMoves[0].eval;
+ i++
+ ) {
+ candidates.push(i);
+ }
+ return doubleMoves[randInt(candidates.length)].moves;
+ }
+};
projects / vchess.git / blobdiff