| 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(sq, color, castling) { |
| 83 | const singleMoveAttack = super.isAttacked(sq, color); |
| 84 | if (singleMoveAttack) return true; |
| 85 | if (!!castling) { |
| 86 | if (this.subTurn == 1) |
| 87 | // Castling at move 1 could be done into check |
| 88 | return false; |
| 89 | return singleMoveAttack; |
| 90 | } |
| 91 | // Double-move allowed: |
| 92 | const curTurn = this.turn; |
| 93 | this.turn = color; |
| 94 | const moves1 = super.getAllPotentialMoves(); |
| 95 | this.turn = curTurn; |
| 96 | for (let move of moves1) { |
| 97 | this.play(move); |
| 98 | const res = super.isAttacked(sq, color); |
| 99 | this.undo(move); |
| 100 | if (res) return res; |
| 101 | } |
| 102 | return false; |
| 103 | } |
| 104 | |
| 105 | filterValid(moves) { |
| 106 | if (this.subTurn == 1) { |
| 107 | return moves.filter(m1 => { |
| 108 | this.play(m1); |
| 109 | // NOTE: no recursion because next call will see subTurn == 2 |
| 110 | const res = super.atLeastOneMove(); |
| 111 | this.undo(m1); |
| 112 | return res; |
| 113 | }); |
| 114 | } |
| 115 | return super.filterValid(moves); |
| 116 | } |
| 117 | |
| 118 | play(move) { |
| 119 | move.flags = JSON.stringify(this.aggregateFlags()); |
| 120 | V.PlayOnBoard(this.board, move); |
| 121 | const epSq = this.getEpSquare(move); |
| 122 | if (this.subTurn == 2) { |
| 123 | let lastEpsq = this.epSquares[this.epSquares.length - 1]; |
| 124 | lastEpsq.push(epSq); |
| 125 | this.turn = V.GetOppCol(this.turn); |
| 126 | } |
| 127 | else { |
| 128 | this.epSquares.push([epSq]); |
| 129 | this.movesCount++; |
| 130 | if (this.movesCount == 1) this.turn = "b"; |
| 131 | } |
| 132 | if (this.movesCount > 1) this.subTurn = 3 - this.subTurn; |
| 133 | this.postPlay(move); |
| 134 | } |
| 135 | |
| 136 | postPlay(move) { |
| 137 | const c = move.vanish[0].c; |
| 138 | const piece = move.vanish[0].p; |
| 139 | const firstRank = c == "w" ? V.size.x - 1 : 0; |
| 140 | |
| 141 | if (piece == V.KING && move.appear.length > 0) { |
| 142 | this.kingPos[c][0] = move.appear[0].x; |
| 143 | this.kingPos[c][1] = move.appear[0].y; |
| 144 | this.castleFlags[c] = [V.size.y, V.size.y]; |
| 145 | return; |
| 146 | } |
| 147 | const oppCol = V.GetOppCol(c); |
| 148 | const oppFirstRank = V.size.x - 1 - firstRank; |
| 149 | if ( |
| 150 | move.start.x == firstRank && //our rook moves? |
| 151 | this.castleFlags[c].includes(move.start.y) |
| 152 | ) { |
| 153 | const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1); |
| 154 | this.castleFlags[c][flagIdx] = V.size.y; |
| 155 | } else if ( |
| 156 | move.end.x == oppFirstRank && //we took opponent rook? |
| 157 | this.castleFlags[oppCol].includes(move.end.y) |
| 158 | ) { |
| 159 | const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1); |
| 160 | this.castleFlags[oppCol][flagIdx] = V.size.y; |
| 161 | } |
| 162 | } |
| 163 | |
| 164 | undo(move) { |
| 165 | this.disaggregateFlags(JSON.parse(move.flags)); |
| 166 | V.UndoOnBoard(this.board, move); |
| 167 | if (this.subTurn == 2 || this.movesCount == 1) { |
| 168 | this.epSquares.pop(); |
| 169 | this.movesCount--; |
| 170 | if (this.movesCount == 0) this.turn = "w"; |
| 171 | } |
| 172 | else { |
| 173 | let lastEpsq = this.epSquares[this.epSquares.length - 1]; |
| 174 | lastEpsq.pop(); |
| 175 | this.turn = V.GetOppCol(this.turn); |
| 176 | } |
| 177 | if (this.movesCount > 0) this.subTurn = 3 - this.subTurn; |
| 178 | super.postUndo(move); |
| 179 | } |
| 180 | |
| 181 | static get VALUES() { |
| 182 | return { |
| 183 | p: 1, |
| 184 | r: 5, |
| 185 | n: 3, |
| 186 | b: 3, |
| 187 | q: 7, //slightly less than in orthodox game |
| 188 | k: 1000 |
| 189 | }; |
| 190 | } |
| 191 | |
| 192 | // No alpha-beta here, just adapted min-max at depth 2(+1) |
| 193 | getComputerMove() { |
| 194 | const maxeval = V.INFINITY; |
| 195 | const color = this.turn; |
| 196 | const oppCol = V.GetOppCol(this.turn); |
| 197 | |
| 198 | // Search best (half) move for opponent turn |
| 199 | const getBestMoveEval = () => { |
| 200 | let score = this.getCurrentScore(); |
| 201 | if (score != "*") { |
| 202 | if (score == "1/2") return 0; |
| 203 | return maxeval * (score == "1-0" ? 1 : -1); |
| 204 | } |
| 205 | let moves = this.getAllValidMoves(); |
| 206 | let res = oppCol == "w" ? -maxeval : maxeval; |
| 207 | for (let m of moves) { |
| 208 | this.play(m); |
| 209 | score = this.getCurrentScore(); |
| 210 | // Now turn is oppCol,2 |
| 211 | if (score != "*") { |
| 212 | if (score == "1/2") |
| 213 | res = oppCol == "w" ? Math.max(res, 0) : Math.min(res, 0); |
| 214 | else { |
| 215 | // King captured |
| 216 | this.undo(m); |
| 217 | return maxeval * (score == "1-0" ? 1 : -1); |
| 218 | } |
| 219 | } |
| 220 | const evalPos = this.evalPosition(); |
| 221 | res = oppCol == "w" ? Math.max(res, evalPos) : Math.min(res, evalPos); |
| 222 | this.undo(m); |
| 223 | } |
| 224 | return res; |
| 225 | }; |
| 226 | |
| 227 | let moves11 = this.getAllValidMoves(); |
| 228 | let doubleMoves = []; |
| 229 | // Rank moves using a min-max at depth 2(+1) |
| 230 | for (let i = 0; i < moves11.length; i++) { |
| 231 | this.play(moves11[i]); |
| 232 | let moves12 = this.getAllValidMoves(); |
| 233 | for (let j = 0; j < moves12.length; j++) { |
| 234 | this.play(moves12[j]); |
| 235 | doubleMoves.push({ |
| 236 | moves: [moves11[i], moves12[j]], |
| 237 | eval: getBestMoveEval() |
| 238 | }); |
| 239 | this.undo(moves12[j]); |
| 240 | } |
| 241 | this.undo(moves11[i]); |
| 242 | } |
| 243 | |
| 244 | doubleMoves.sort((a, b) => { |
| 245 | return (color == "w" ? 1 : -1) * (b.eval - a.eval); |
| 246 | }); |
| 247 | let candidates = [0]; //indices of candidates moves |
| 248 | for ( |
| 249 | let i = 1; |
| 250 | i < doubleMoves.length && doubleMoves[i].eval == doubleMoves[0].eval; |
| 251 | i++ |
| 252 | ) { |
| 253 | candidates.push(i); |
| 254 | } |
| 255 | return doubleMoves[randInt(candidates.length)].moves; |
| 256 | } |
| 257 | }; |