| 1 | import { ChessRules } from "@/base_rules"; |
| 2 | import { randInt } from "@/utils/alea"; |
| 3 | |
| 4 | export class Doublemove2Rules extends ChessRules { |
| 5 | static IsGoodEnpassant(enpassant) { |
| 6 | const squares = enpassant.split(","); |
| 7 | if (squares.length > 2) return false; |
| 8 | for (let sq of squares) { |
| 9 | if (sq != "-") { |
| 10 | const ep = V.SquareToCoords(sq); |
| 11 | if (isNaN(ep.x) || !V.OnBoard(ep)) return false; |
| 12 | } |
| 13 | } |
| 14 | return true; |
| 15 | } |
| 16 | |
| 17 | // There may be 2 enPassant squares (if 2 pawns jump 2 squares in same turn) |
| 18 | getEnpassantFen() { |
| 19 | return this.epSquares[this.epSquares.length - 1].map( |
| 20 | epsq => epsq === undefined |
| 21 | ? "-" //no en-passant |
| 22 | : V.CoordsToSquare(epsq) |
| 23 | ).join(","); |
| 24 | } |
| 25 | |
| 26 | setOtherVariables(fen) { |
| 27 | const parsedFen = V.ParseFen(fen); |
| 28 | this.setFlags(parsedFen.flags); |
| 29 | this.epSquares = [parsedFen.enpassant.split(",").map(sq => { |
| 30 | if (sq != "-") return V.SquareToCoords(sq); |
| 31 | return undefined; |
| 32 | })]; |
| 33 | this.scanKings(fen); |
| 34 | // Extract subTurn from turn indicator: "w" (first move), or |
| 35 | // "w1" or "w2" white subturn 1 or 2, and same for black |
| 36 | this.turn = parsedFen.turn; |
| 37 | this.subTurn = 1; |
| 38 | } |
| 39 | |
| 40 | getEnpassantCaptures([x, y], shiftX) { |
| 41 | let moves = []; |
| 42 | // En passant: always OK if subturn 1, |
| 43 | // OK on subturn 2 only if enPassant was played at subturn 1 |
| 44 | // (and if there are two e.p. squares available). |
| 45 | const Lep = this.epSquares.length; |
| 46 | const epSquares = this.epSquares[Lep - 1]; //always at least one element |
| 47 | let epSqs = []; |
| 48 | epSquares.forEach(sq => { |
| 49 | if (sq) epSqs.push(sq); |
| 50 | }); |
| 51 | if (epSqs.length == 0) return moves; |
| 52 | const oppCol = V.GetOppCol(this.getColor(x, y)); |
| 53 | for (let sq of epSqs) { |
| 54 | if ( |
| 55 | this.subTurn == 1 || |
| 56 | (epSqs.length == 2 && |
| 57 | // Was this en-passant capture already played at subturn 1 ? |
| 58 | // (Or maybe the opponent filled the en-passant square with a piece) |
| 59 | this.board[epSqs[0].x][epSqs[0].y] != V.EMPTY) |
| 60 | ) { |
| 61 | if ( |
| 62 | sq.x == x + shiftX && |
| 63 | Math.abs(sq.y - y) == 1 && |
| 64 | // Add condition "enemy pawn must be present" |
| 65 | this.getPiece(x, sq.y) == V.PAWN && |
| 66 | this.getColor(x, sq.y) == oppCol |
| 67 | ) { |
| 68 | let epMove = this.getBasicMove([x, y], [sq.x, sq.y]); |
| 69 | epMove.vanish.push({ |
| 70 | x: x, |
| 71 | y: sq.y, |
| 72 | p: "p", |
| 73 | c: oppCol |
| 74 | }); |
| 75 | moves.push(epMove); |
| 76 | } |
| 77 | } |
| 78 | } |
| 79 | return moves; |
| 80 | } |
| 81 | |
| 82 | isAttacked() { |
| 83 | // Goal is king capture => no checks |
| 84 | return false; |
| 85 | } |
| 86 | |
| 87 | filterValid(moves) { |
| 88 | return moves; |
| 89 | } |
| 90 | |
| 91 | getCheckSquares() { |
| 92 | return []; |
| 93 | } |
| 94 | |
| 95 | getCurrentScore() { |
| 96 | const color = this.turn; |
| 97 | if (this.kingPos[color][0] < 0) return (color == 'w' ? "0-1" : "1-0"); |
| 98 | return "*"; |
| 99 | } |
| 100 | |
| 101 | play(move) { |
| 102 | move.flags = JSON.stringify(this.aggregateFlags()); |
| 103 | V.PlayOnBoard(this.board, move); |
| 104 | const epSq = this.getEpSquare(move); |
| 105 | if (this.subTurn == 2) { |
| 106 | let lastEpsq = this.epSquares[this.epSquares.length - 1]; |
| 107 | lastEpsq.push(epSq); |
| 108 | this.turn = V.GetOppCol(this.turn); |
| 109 | } |
| 110 | else { |
| 111 | this.epSquares.push([epSq]); |
| 112 | this.movesCount++; |
| 113 | if ( |
| 114 | this.movesCount == 1 || |
| 115 | // King is captured at subTurn 1? |
| 116 | (move.vanish.length == 2 && move.vanish[1].p == V.KING) |
| 117 | ) { |
| 118 | this.turn = "b"; |
| 119 | } |
| 120 | } |
| 121 | if (this.movesCount > 1) this.subTurn = 3 - this.subTurn; |
| 122 | this.postPlay(move); |
| 123 | } |
| 124 | |
| 125 | postPlay(move) { |
| 126 | const c = move.vanish[0].c; |
| 127 | const piece = move.vanish[0].p; |
| 128 | const firstRank = c == "w" ? V.size.x - 1 : 0; |
| 129 | |
| 130 | if (piece == V.KING && move.appear.length > 0) { |
| 131 | this.kingPos[c] = [move.appear[0].x, move.appear[0].y]; |
| 132 | this.castleFlags[c] = [V.size.y, V.size.y]; |
| 133 | return; |
| 134 | } |
| 135 | const oppCol = V.GetOppCol(c); |
| 136 | if (move.vanish.length == 2 && move.vanish[1].p == V.KING) { |
| 137 | // Opponent's king is captured, game over |
| 138 | this.kingPos[oppCol] = [-1, -1]; |
| 139 | move.captureKing = true; //for undo |
| 140 | } |
| 141 | const oppFirstRank = V.size.x - 1 - firstRank; |
| 142 | if ( |
| 143 | move.start.x == firstRank && //our rook moves? |
| 144 | this.castleFlags[c].includes(move.start.y) |
| 145 | ) { |
| 146 | const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1); |
| 147 | this.castleFlags[c][flagIdx] = V.size.y; |
| 148 | } |
| 149 | else if ( |
| 150 | move.end.x == oppFirstRank && //we took opponent rook? |
| 151 | this.castleFlags[oppCol].includes(move.end.y) |
| 152 | ) { |
| 153 | const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1); |
| 154 | this.castleFlags[oppCol][flagIdx] = V.size.y; |
| 155 | } |
| 156 | } |
| 157 | |
| 158 | undo(move) { |
| 159 | this.disaggregateFlags(JSON.parse(move.flags)); |
| 160 | V.UndoOnBoard(this.board, move); |
| 161 | if (this.subTurn == 2 || this.movesCount == 1 || !!move.captureKing) { |
| 162 | this.epSquares.pop(); |
| 163 | this.movesCount--; |
| 164 | if (this.movesCount == 0) this.turn = "w"; |
| 165 | } |
| 166 | else { |
| 167 | let lastEpsq = this.epSquares[this.epSquares.length - 1]; |
| 168 | lastEpsq.pop(); |
| 169 | this.turn = V.GetOppCol(this.turn); |
| 170 | } |
| 171 | if (this.movesCount > 0) this.subTurn = 3 - this.subTurn; |
| 172 | this.postUndo(move); |
| 173 | } |
| 174 | |
| 175 | postUndo(move) { |
| 176 | if (move.vanish.length == 2 && move.vanish[1].p == V.KING) |
| 177 | // Opponent's king was captured |
| 178 | this.kingPos[move.vanish[1].c] = [move.vanish[1].x, move.vanish[1].y]; |
| 179 | super.postUndo(move); |
| 180 | } |
| 181 | |
| 182 | // No alpha-beta here, just adapted min-max at depth 2(+1) |
| 183 | getComputerMove() { |
| 184 | const maxeval = V.INFINITY; |
| 185 | const color = this.turn; |
| 186 | const oppCol = V.GetOppCol(this.turn); |
| 187 | |
| 188 | // Search best (half) move for opponent turn |
| 189 | const getBestMoveEval = () => { |
| 190 | let score = this.getCurrentScore(); |
| 191 | if (score != "*") return maxeval * (score == "1-0" ? 1 : -1); |
| 192 | let moves = this.getAllValidMoves(); |
| 193 | let res = oppCol == "w" ? -maxeval : maxeval; |
| 194 | for (let m of moves) { |
| 195 | this.play(m); |
| 196 | score = this.getCurrentScore(); |
| 197 | if (score != "*") { |
| 198 | // King captured |
| 199 | this.undo(m); |
| 200 | return maxeval * (score == "1-0" ? 1 : -1); |
| 201 | } |
| 202 | const evalPos = this.evalPosition(); |
| 203 | res = oppCol == "w" ? Math.max(res, evalPos) : Math.min(res, evalPos); |
| 204 | this.undo(m); |
| 205 | } |
| 206 | return res; |
| 207 | }; |
| 208 | |
| 209 | const moves11 = this.getAllValidMoves(); |
| 210 | if (this.movesCount == 0) |
| 211 | // First white move at random: |
| 212 | return moves11[randInt(moves11.length)]; |
| 213 | let doubleMoves = []; |
| 214 | // Rank moves using a min-max at depth 2 |
| 215 | for (let i = 0; i < moves11.length; i++) { |
| 216 | this.play(moves11[i]); |
| 217 | const moves12 = this.getAllValidMoves(); |
| 218 | for (let j = 0; j < moves12.length; j++) { |
| 219 | this.play(moves12[j]); |
| 220 | doubleMoves.push({ |
| 221 | moves: [moves11[i], moves12[j]], |
| 222 | // Small fluctuations to uniformize play a little |
| 223 | eval: getBestMoveEval() + 0.05 - Math.random() / 10 |
| 224 | }); |
| 225 | this.undo(moves12[j]); |
| 226 | } |
| 227 | this.undo(moves11[i]); |
| 228 | } |
| 229 | |
| 230 | doubleMoves.sort((a, b) => { |
| 231 | return (color == "w" ? 1 : -1) * (b.eval - a.eval); |
| 232 | }); |
| 233 | let candidates = [0]; //indices of candidates moves |
| 234 | for ( |
| 235 | let i = 1; |
| 236 | i < doubleMoves.length && doubleMoves[i].eval == doubleMoves[0].eval; |
| 237 | i++ |
| 238 | ) { |
| 239 | candidates.push(i); |
| 240 | } |
| 241 | return doubleMoves[randInt(candidates.length)].moves; |
| 242 | } |
| 243 | }; |