| 1 | import { ChessRules } from "@/base_rules"; |
| 2 | import { randInt } from "@/utils/alea"; |
| 3 | |
| 4 | export const VariantRules = class MarseilleRules 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 | getTurnFen() { |
| 18 | return this.turn + this.subTurn; |
| 19 | } |
| 20 | |
| 21 | // There may be 2 enPassant squares (if 2 pawns jump 2 squares in same turn) |
| 22 | getEnpassantFen() { |
| 23 | return this.epSquares[this.epSquares.length - 1].map( |
| 24 | epsq => epsq === undefined |
| 25 | ? "-" //no en-passant |
| 26 | : V.CoordsToSquare(epsq) |
| 27 | ).join(","); |
| 28 | } |
| 29 | |
| 30 | setOtherVariables(fen) { |
| 31 | const parsedFen = V.ParseFen(fen); |
| 32 | this.setFlags(parsedFen.flags); |
| 33 | this.epSquares = [parsedFen.enpassant.split(",").map(sq => { |
| 34 | if (sq != "-") return V.SquareToCoords(sq); |
| 35 | return undefined; |
| 36 | })]; |
| 37 | this.scanKingsRooks(fen); |
| 38 | // Extract subTurn from turn indicator: "w" (first move), or |
| 39 | // "w1" or "w2" white subturn 1 or 2, and same for black |
| 40 | const fullTurn = V.ParseFen(fen).turn; |
| 41 | this.turn = fullTurn[0]; |
| 42 | this.subTurn = fullTurn[1] || 0; //"w0" = special code for first move in game |
| 43 | } |
| 44 | |
| 45 | getPotentialPawnMoves([x, y]) { |
| 46 | const color = this.turn; |
| 47 | let moves = []; |
| 48 | const [sizeX, sizeY] = [V.size.x, V.size.y]; |
| 49 | const shiftX = color == "w" ? -1 : 1; |
| 50 | const firstRank = color == "w" ? sizeX - 1 : 0; |
| 51 | const startRank = color == "w" ? sizeX - 2 : 1; |
| 52 | const lastRank = color == "w" ? 0 : sizeX - 1; |
| 53 | const finalPieces = |
| 54 | x + shiftX == lastRank ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN] : [V.PAWN]; |
| 55 | |
| 56 | // One square forward |
| 57 | if (this.board[x + shiftX][y] == V.EMPTY) { |
| 58 | for (let piece of finalPieces) { |
| 59 | moves.push( |
| 60 | this.getBasicMove([x, y], [x + shiftX, y], { c: color, p: piece }) |
| 61 | ); |
| 62 | } |
| 63 | // Next condition because pawns on 1st rank can generally jump |
| 64 | if ( |
| 65 | [startRank, firstRank].includes(x) && |
| 66 | this.board[x + 2 * shiftX][y] == V.EMPTY |
| 67 | ) { |
| 68 | // Two squares jump |
| 69 | moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y])); |
| 70 | } |
| 71 | } |
| 72 | // Captures |
| 73 | for (let shiftY of [-1, 1]) { |
| 74 | if ( |
| 75 | y + shiftY >= 0 && |
| 76 | y + shiftY < sizeY && |
| 77 | this.board[x + shiftX][y + shiftY] != V.EMPTY && |
| 78 | this.canTake([x, y], [x + shiftX, y + shiftY]) |
| 79 | ) { |
| 80 | for (let piece of finalPieces) { |
| 81 | moves.push( |
| 82 | this.getBasicMove([x, y], [x + shiftX, y + shiftY], { |
| 83 | c: color, |
| 84 | p: piece |
| 85 | }) |
| 86 | ); |
| 87 | } |
| 88 | } |
| 89 | } |
| 90 | |
| 91 | // En passant: always OK if subturn 1, |
| 92 | // OK on subturn 2 only if enPassant was played at subturn 1 |
| 93 | // (and if there are two e.p. squares available). |
| 94 | const Lep = this.epSquares.length; |
| 95 | const epSquares = this.epSquares[Lep - 1]; //always at least one element |
| 96 | let epSqs = []; |
| 97 | epSquares.forEach(sq => { |
| 98 | if (sq) epSqs.push(sq); |
| 99 | }); |
| 100 | if (epSqs.length == 0) return moves; |
| 101 | const oppCol = V.GetOppCol(color); |
| 102 | for (let sq of epSqs) { |
| 103 | if ( |
| 104 | this.subTurn == 1 || |
| 105 | (epSqs.length == 2 && |
| 106 | // Was this en-passant capture already played at subturn 1 ? |
| 107 | // (Or maybe the opponent filled the en-passant square with a piece) |
| 108 | this.board[epSqs[0].x][epSqs[0].y] != V.EMPTY) |
| 109 | ) { |
| 110 | if ( |
| 111 | sq.x == x + shiftX && |
| 112 | Math.abs(sq.y - y) == 1 && |
| 113 | // Add condition "enemy pawn must be present" |
| 114 | this.getPiece(x, sq.y) == V.PAWN && |
| 115 | this.getColor(x, sq.y) == oppCol |
| 116 | ) { |
| 117 | let epMove = this.getBasicMove([x, y], [sq.x, sq.y]); |
| 118 | epMove.vanish.push({ |
| 119 | x: x, |
| 120 | y: sq.y, |
| 121 | p: "p", |
| 122 | c: oppCol |
| 123 | }); |
| 124 | moves.push(epMove); |
| 125 | } |
| 126 | } |
| 127 | } |
| 128 | |
| 129 | return moves; |
| 130 | } |
| 131 | |
| 132 | play(move) { |
| 133 | move.flags = JSON.stringify(this.aggregateFlags()); |
| 134 | move.turn = this.turn + this.subTurn; |
| 135 | V.PlayOnBoard(this.board, move); |
| 136 | const epSq = this.getEpSquare(move); |
| 137 | if (this.subTurn == 0) { |
| 138 | //first move in game |
| 139 | this.turn = "b"; |
| 140 | this.subTurn = 1; |
| 141 | this.epSquares.push([epSq]); |
| 142 | } |
| 143 | // Does this move give check on subturn 1? If yes, skip subturn 2 |
| 144 | else if (this.subTurn == 1 && this.underCheck(V.GetOppCol(this.turn))) { |
| 145 | this.turn = V.GetOppCol(this.turn); |
| 146 | this.epSquares.push([epSq]); |
| 147 | move.checkOnSubturn1 = true; |
| 148 | } else { |
| 149 | if (this.subTurn == 2) { |
| 150 | this.turn = V.GetOppCol(this.turn); |
| 151 | let lastEpsq = this.epSquares[this.epSquares.length - 1]; |
| 152 | lastEpsq.push(epSq); |
| 153 | } else this.epSquares.push([epSq]); |
| 154 | this.subTurn = 3 - this.subTurn; |
| 155 | } |
| 156 | this.updateVariables(move); |
| 157 | } |
| 158 | |
| 159 | undo(move) { |
| 160 | this.disaggregateFlags(JSON.parse(move.flags)); |
| 161 | V.UndoOnBoard(this.board, move); |
| 162 | if (move.turn[1] == "0" || move.checkOnSubturn1 || this.subTurn == 2) |
| 163 | this.epSquares.pop(); |
| 164 | else { |
| 165 | // this.subTurn == 1 |
| 166 | let lastEpsq = this.epSquares[this.epSquares.length - 1]; |
| 167 | lastEpsq.pop(); |
| 168 | } |
| 169 | this.turn = move.turn[0]; |
| 170 | this.subTurn = parseInt(move.turn[1]); |
| 171 | this.unupdateVariables(move); |
| 172 | } |
| 173 | |
| 174 | // NOTE: GenRandInitFen() is OK, |
| 175 | // since at first move turn indicator is just "w" |
| 176 | |
| 177 | static get VALUES() { |
| 178 | return { |
| 179 | p: 1, |
| 180 | r: 5, |
| 181 | n: 3, |
| 182 | b: 3, |
| 183 | q: 7, //slightly less than in orthodox game |
| 184 | k: 1000 |
| 185 | }; |
| 186 | } |
| 187 | |
| 188 | // No alpha-beta here, just adapted min-max at depth 2(+1) |
| 189 | getComputerMove() { |
| 190 | const maxeval = V.INFINITY; |
| 191 | const color = this.turn; |
| 192 | const oppCol = V.GetOppCol(this.turn); |
| 193 | |
| 194 | // Search best (half) move for opponent turn |
| 195 | const getBestMoveEval = () => { |
| 196 | let score = this.getCurrentScore(); |
| 197 | if (score != "*") { |
| 198 | if (score == "1/2") return 0; |
| 199 | return maxeval * (score == "1-0" ? 1 : -1); |
| 200 | } |
| 201 | let moves = this.getAllValidMoves(); |
| 202 | let res = oppCol == "w" ? -maxeval : maxeval; |
| 203 | for (let m of moves) { |
| 204 | this.play(m); |
| 205 | score = this.getCurrentScore(); |
| 206 | // Now turn is oppCol,2 if m doesn't give check |
| 207 | // Otherwise it's color,1. In both cases the next test makes sense |
| 208 | if (score != "*") { |
| 209 | if (score == "1/2") |
| 210 | res = oppCol == "w" ? Math.max(res, 0) : Math.min(res, 0); |
| 211 | else { |
| 212 | // Found a mate |
| 213 | this.undo(m); |
| 214 | return maxeval * (score == "1-0" ? 1 : -1); |
| 215 | } |
| 216 | } |
| 217 | const evalPos = this.evalPosition(); |
| 218 | res = oppCol == "w" ? Math.max(res, evalPos) : Math.min(res, evalPos); |
| 219 | this.undo(m); |
| 220 | } |
| 221 | return res; |
| 222 | }; |
| 223 | |
| 224 | let moves11 = this.getAllValidMoves(); |
| 225 | let doubleMoves = []; |
| 226 | // Rank moves using a min-max at depth 2 |
| 227 | for (let i = 0; i < moves11.length; i++) { |
| 228 | this.play(moves11[i]); |
| 229 | if (this.turn != color) { |
| 230 | // We gave check with last move: search the best opponent move |
| 231 | doubleMoves.push({ moves: [moves11[i]], eval: getBestMoveEval() }); |
| 232 | } else { |
| 233 | let moves12 = this.getAllValidMoves(); |
| 234 | for (let j = 0; j < moves12.length; j++) { |
| 235 | this.play(moves12[j]); |
| 236 | doubleMoves.push({ |
| 237 | moves: [moves11[i], moves12[j]], |
| 238 | eval: getBestMoveEval() |
| 239 | }); |
| 240 | this.undo(moves12[j]); |
| 241 | } |
| 242 | } |
| 243 | this.undo(moves11[i]); |
| 244 | } |
| 245 | |
| 246 | doubleMoves.sort((a, b) => { |
| 247 | return (color == "w" ? 1 : -1) * (b.eval - a.eval); |
| 248 | }); |
| 249 | let candidates = [0]; //indices of candidates moves |
| 250 | for ( |
| 251 | let i = 1; |
| 252 | i < doubleMoves.length && doubleMoves[i].eval == doubleMoves[0].eval; |
| 253 | i++ |
| 254 | ) { |
| 255 | candidates.push(i); |
| 256 | } |
| 257 | |
| 258 | const selected = doubleMoves[randInt(candidates.length)].moves; |
| 259 | if (selected.length == 1) return selected[0]; |
| 260 | return selected; |
| 261 | } |
| 262 | }; |