| 1 | import { ChessRules, PiPo, Move } from "@/base_rules"; |
| 2 | |
| 3 | export class EnpassantRules extends ChessRules { |
| 4 | static IsGoodEnpassant(enpassant) { |
| 5 | if (enpassant != "-") { |
| 6 | const squares = enpassant.split(","); |
| 7 | for (let sq of squares) { |
| 8 | const ep = V.SquareToCoords(sq); |
| 9 | if (isNaN(ep.x) || !V.OnBoard(ep)) return false; |
| 10 | } |
| 11 | } |
| 12 | return true; |
| 13 | } |
| 14 | |
| 15 | getEpSquare(moveOrSquare) { |
| 16 | if (!moveOrSquare) return undefined; |
| 17 | if (typeof moveOrSquare === "string") { |
| 18 | const square = moveOrSquare; |
| 19 | if (square == "-") return undefined; |
| 20 | let res = []; |
| 21 | square.split(",").forEach(sq => { |
| 22 | res.push(V.SquareToCoords(sq)); |
| 23 | }); |
| 24 | return res; |
| 25 | } |
| 26 | // Argument is a move: all intermediate squares are en-passant candidates, |
| 27 | // except if the moving piece is a king. |
| 28 | const move = moveOrSquare; |
| 29 | const piece = move.appear[0].p; |
| 30 | if (piece == V.KING || |
| 31 | ( |
| 32 | Math.abs(move.end.x-move.start.x) <= 1 && |
| 33 | Math.abs(move.end.y-move.start.y) <= 1 |
| 34 | ) |
| 35 | ) { |
| 36 | return undefined; |
| 37 | } |
| 38 | const delta = [move.end.x-move.start.x, move.end.y-move.start.y]; |
| 39 | let step = undefined; |
| 40 | if (piece == V.KNIGHT) { |
| 41 | const divisor = Math.min(Math.abs(delta[0]), Math.abs(delta[1])); |
| 42 | step = [delta[0]/divisor || 0, delta[1]/divisor || 0]; |
| 43 | } else { |
| 44 | step = [delta[0]/Math.abs(delta[0]) || 0, delta[1]/Math.abs(delta[1]) || 0]; |
| 45 | } |
| 46 | let res = []; |
| 47 | for ( |
| 48 | let [x,y] = [move.start.x+step[0],move.start.y+step[1]]; |
| 49 | x != move.end.x || y != move.end.y; |
| 50 | x += step[0], y += step[1] |
| 51 | ) { |
| 52 | res.push({x:x, y:y}); |
| 53 | } |
| 54 | // Add final square to know which piece is taken en passant: |
| 55 | res.push(move.end); |
| 56 | return res; |
| 57 | } |
| 58 | |
| 59 | getEnpassantFen() { |
| 60 | const L = this.epSquares.length; |
| 61 | if (!this.epSquares[L - 1]) return "-"; //no en-passant |
| 62 | let res = ""; |
| 63 | this.epSquares[L - 1].forEach(sq => { |
| 64 | res += V.CoordsToSquare(sq) + ","; |
| 65 | }); |
| 66 | return res.slice(0, -1); //remove last comma |
| 67 | } |
| 68 | |
| 69 | getPotentialMovesFrom([x, y]) { |
| 70 | let moves = super.getPotentialMovesFrom([x,y]); |
| 71 | // Add en-passant captures from this square: |
| 72 | const L = this.epSquares.length; |
| 73 | if (!this.epSquares[L - 1]) return moves; |
| 74 | const squares = this.epSquares[L - 1]; |
| 75 | const S = squares.length; |
| 76 | // Object describing the removed opponent's piece: |
| 77 | const pipoV = new PiPo({ |
| 78 | x: squares[S-1].x, |
| 79 | y: squares[S-1].y, |
| 80 | c: V.GetOppCol(this.turn), |
| 81 | p: this.getPiece(squares[S-1].x, squares[S-1].y) |
| 82 | }); |
| 83 | // Check if existing non-capturing moves could also capture en passant |
| 84 | moves.forEach(m => { |
| 85 | if ( |
| 86 | m.appear[0].p != V.PAWN && //special pawn case is handled elsewhere |
| 87 | m.vanish.length <= 1 && |
| 88 | [...Array(S-1).keys()].some(i => { |
| 89 | return m.end.x == squares[i].x && m.end.y == squares[i].y; |
| 90 | }) |
| 91 | ) { |
| 92 | m.vanish.push(pipoV); |
| 93 | } |
| 94 | }); |
| 95 | // Special case of the king knight's movement: |
| 96 | if (this.getPiece(x, y) == V.KING) { |
| 97 | V.steps[V.KNIGHT].forEach(step => { |
| 98 | const endX = x + step[0]; |
| 99 | const endY = y + step[1]; |
| 100 | if ( |
| 101 | V.OnBoard(endX, endY) && |
| 102 | [...Array(S-1).keys()].some(i => { |
| 103 | return endX == squares[i].x && endY == squares[i].y; |
| 104 | }) |
| 105 | ) { |
| 106 | let enpassantMove = this.getBasicMove([x, y], [endX, endY]); |
| 107 | enpassantMove.vanish.push(pipoV); |
| 108 | moves.push(enpassantMove); |
| 109 | } |
| 110 | }); |
| 111 | } |
| 112 | return moves; |
| 113 | } |
| 114 | |
| 115 | getEnpassantCaptures([x, y], shiftX) { |
| 116 | const Lep = this.epSquares.length; |
| 117 | const squares = this.epSquares[Lep - 1]; |
| 118 | let moves = []; |
| 119 | if (!!squares) { |
| 120 | const S = squares.length; |
| 121 | const taken = squares[S-1]; |
| 122 | const pipoV = new PiPo({ |
| 123 | x: taken.x, |
| 124 | y: taken.y, |
| 125 | p: this.getPiece(taken.x, taken.y), |
| 126 | c: this.getColor(taken.x, taken.y) |
| 127 | }); |
| 128 | [...Array(S-1).keys()].forEach(i => { |
| 129 | const sq = squares[i]; |
| 130 | if (sq.x == x + shiftX && Math.abs(sq.y - y) == 1) { |
| 131 | let enpassantMove = this.getBasicMove([x, y], [sq.x, sq.y]); |
| 132 | enpassantMove.vanish.push(pipoV); |
| 133 | moves.push(enpassantMove); |
| 134 | } |
| 135 | }); |
| 136 | } |
| 137 | return moves; |
| 138 | } |
| 139 | |
| 140 | // Remove the "onestep" condition: knight promote to knightrider: |
| 141 | getPotentialKnightMoves(sq) { |
| 142 | return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT]); |
| 143 | } |
| 144 | |
| 145 | filterValid(moves) { |
| 146 | const filteredMoves = super.filterValid(moves); |
| 147 | // If at least one full move made, everything is allowed: |
| 148 | if (this.movesCount >= 2) |
| 149 | return filteredMoves; |
| 150 | // Else, forbid captures: |
| 151 | return filteredMoves.filter(m => m.vanish.length == 1); |
| 152 | } |
| 153 | |
| 154 | isAttackedByKnight(sq, color) { |
| 155 | return this.isAttackedBySlideNJump( |
| 156 | sq, |
| 157 | color, |
| 158 | V.KNIGHT, |
| 159 | V.steps[V.KNIGHT] |
| 160 | ); |
| 161 | } |
| 162 | |
| 163 | static get SEARCH_DEPTH() { |
| 164 | return 2; |
| 165 | } |
| 166 | |
| 167 | static get VALUES() { |
| 168 | return { |
| 169 | p: 1, |
| 170 | r: 5, |
| 171 | n: 4, |
| 172 | b: 3, |
| 173 | q: 9, |
| 174 | k: 1000 |
| 175 | }; |
| 176 | } |
| 177 | }; |