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7d8bf63e BA |
1 | import { ChessRules, PiPo, Move } from "@/base_rules"; |
2 | ||
3 | export const VariantRules = class EnpassantRules extends ChessRules { | |
4 | ||
5 | static IsGoodEnpassant(enpassant) { | |
6 | if (enpassant != "-") { | |
7 | const squares = enpassant.split(","); | |
8 | for (let sq of squares) { | |
9 | const ep = V.SquareToCoords(sq); | |
10 | if (isNaN(ep.x) || !V.OnBoard(ep)) return false; | |
11 | } | |
12 | } | |
13 | return true; | |
14 | } | |
15 | ||
16 | getEpSquare(moveOrSquare) { | |
17 | if (!moveOrSquare) return undefined; | |
18 | if (typeof moveOrSquare === "string") { | |
19 | const square = moveOrSquare; | |
20 | if (square == "-") return undefined; | |
21 | let res = []; | |
22 | square.split(",").forEach(sq => { | |
23 | res.push(V.SquareToCoords(sq)); | |
24 | }); | |
25 | return res; | |
26 | } | |
27 | // Argument is a move: all intermediate squares are en-passant candidates, | |
28 | // except if the moving piece is a king. | |
29 | const move = moveOrSquare; | |
30 | const piece = move.appear[0].p; | |
31 | if (piece == V.KING || | |
32 | ( | |
33 | Math.abs(move.end.x-move.start.x) <= 1 && | |
34 | Math.abs(move.end.y-move.start.y) <= 1 | |
35 | ) | |
36 | ) { | |
37 | return undefined; | |
38 | } | |
39 | const delta = [move.end.x-move.start.x, move.end.y-move.start.y]; | |
40 | let step = undefined; | |
41 | if (piece == V.KNIGHT) { | |
42 | const divisor = Math.min(Math.abs(delta[0]), Math.abs(delta[1])); | |
43 | step = [delta[0]/divisor || 0, delta[1]/divisor || 0]; | |
44 | } else { | |
45 | step = [delta[0]/Math.abs(delta[0]) || 0, delta[1]/Math.abs(delta[1]) || 0]; | |
46 | } | |
47 | let res = []; | |
48 | for ( | |
49 | let [x,y] = [move.start.x+step[0],move.start.y+step[1]]; | |
50 | x != move.end.x || y != move.end.y; | |
51 | x += step[0], y += step[1] | |
52 | ) { | |
53 | res.push({x:x, y:y}); | |
54 | } | |
55 | // Add final square to know which piece is taken en passant: | |
56 | res.push(move.end); | |
57 | return res; | |
58 | } | |
59 | ||
60 | getEnpassantFen() { | |
61 | const L = this.epSquares.length; | |
62 | if (!this.epSquares[L - 1]) return "-"; //no en-passant | |
63 | let res = ""; | |
64 | this.epSquares[L - 1].forEach(sq => { | |
65 | res += V.CoordsToSquare(sq) + ","; | |
66 | }); | |
67 | return res.slice(0, -1); //remove last comma | |
68 | } | |
69 | ||
70 | // TODO: this getPotentialPawnMovesFrom() is mostly duplicated: | |
71 | // it could be split in "capture", "promotion", "enpassant"... | |
72 | getPotentialPawnMoves([x, y]) { | |
73 | const color = this.turn; | |
74 | let moves = []; | |
75 | const [sizeX, sizeY] = [V.size.x, V.size.y]; | |
76 | const shiftX = color == "w" ? -1 : 1; | |
77 | const firstRank = color == "w" ? sizeX - 1 : 0; | |
78 | const startRank = color == "w" ? sizeX - 2 : 1; | |
79 | const lastRank = color == "w" ? 0 : sizeX - 1; | |
80 | const pawnColor = this.getColor(x, y); //can be different for checkered | |
81 | ||
82 | // NOTE: next condition is generally true (no pawn on last rank) | |
83 | if (x + shiftX >= 0 && x + shiftX < sizeX) { | |
84 | const finalPieces = | |
85 | x + shiftX == lastRank | |
86 | ? [V.ROOK, V.KNIGHT, V.BISHOP, V.QUEEN] | |
87 | : [V.PAWN]; | |
88 | // One square forward | |
89 | if (this.board[x + shiftX][y] == V.EMPTY) { | |
90 | for (let piece of finalPieces) { | |
91 | moves.push( | |
92 | this.getBasicMove([x, y], [x + shiftX, y], { | |
93 | c: pawnColor, | |
94 | p: piece | |
95 | }) | |
96 | ); | |
97 | } | |
98 | // Next condition because pawns on 1st rank can generally jump | |
99 | if ( | |
100 | [startRank, firstRank].includes(x) && | |
101 | this.board[x + 2 * shiftX][y] == V.EMPTY | |
102 | ) { | |
103 | // Two squares jump | |
104 | moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y])); | |
105 | } | |
106 | } | |
107 | // Captures | |
108 | for (let shiftY of [-1, 1]) { | |
109 | if ( | |
110 | y + shiftY >= 0 && | |
111 | y + shiftY < sizeY && | |
112 | this.board[x + shiftX][y + shiftY] != V.EMPTY && | |
113 | this.canTake([x, y], [x + shiftX, y + shiftY]) | |
114 | ) { | |
115 | for (let piece of finalPieces) { | |
116 | moves.push( | |
117 | this.getBasicMove([x, y], [x + shiftX, y + shiftY], { | |
118 | c: pawnColor, | |
119 | p: piece | |
120 | }) | |
121 | ); | |
122 | } | |
123 | } | |
124 | } | |
125 | } | |
126 | ||
127 | // En passant | |
128 | const Lep = this.epSquares.length; | |
129 | const squares = this.epSquares[Lep - 1]; | |
130 | if (!!squares) { | |
131 | const S = squares.length; | |
132 | const taken = squares[S-1]; | |
133 | const pipoV = new PiPo({ | |
134 | x: taken.x, | |
135 | y: taken.y, | |
136 | p: this.getPiece(taken.x, taken.y), | |
137 | c: this.getColor(taken.x, taken.y) | |
138 | }); | |
139 | [...Array(S-1).keys()].forEach(i => { | |
140 | const sq = squares[i]; | |
141 | if (sq.x == x + shiftX && Math.abs(sq.y - y) == 1) { | |
142 | let enpassantMove = this.getBasicMove([x, y], [sq.x, sq.y]); | |
143 | enpassantMove.vanish.push(pipoV); | |
144 | moves.push(enpassantMove); | |
145 | } | |
146 | }); | |
147 | } | |
148 | ||
149 | return moves; | |
150 | } | |
151 | ||
152 | // Remove the "onestep" condition: knight promote to knightrider: | |
153 | ||
154 | getPotentialKnightMoves(sq) { | |
155 | return this.getSlideNJumpMoves(sq, V.steps[V.KNIGHT]); | |
156 | } | |
157 | ||
158 | isAttackedByKnight(sq, colors) { | |
159 | return this.isAttackedBySlideNJump( | |
160 | sq, | |
161 | colors, | |
162 | V.KNIGHT, | |
163 | V.steps[V.KNIGHT] | |
164 | ); | |
165 | } | |
166 | ||
167 | getPotentialMovesFrom([x, y]) { | |
168 | let moves = super.getPotentialMovesFrom([x,y]); | |
169 | // Add en-passant captures from this square: | |
170 | const L = this.epSquares.length; | |
171 | if (!this.epSquares[L - 1]) return moves; | |
172 | const squares = this.epSquares[L - 1]; | |
173 | const S = squares.length; | |
174 | // Object describing the removed opponent's piece: | |
175 | const pipoV = new PiPo({ | |
176 | x: squares[S-1].x, | |
177 | y: squares[S-1].y, | |
178 | c: V.GetOppCol(this.turn), | |
179 | p: this.getPiece(squares[S-1].x, squares[S-1].y) | |
180 | }); | |
181 | // Check if existing non-capturing moves could also capture en passant | |
182 | moves.forEach(m => { | |
183 | if ( | |
184 | m.appear[0].p != V.PAWN && //special pawn case is handled elsewhere | |
185 | m.vanish.length <= 1 && | |
186 | [...Array(S-1).keys()].some(i => { | |
187 | return m.end.x == squares[i].x && m.end.y == squares[i].y; | |
188 | }) | |
189 | ) { | |
190 | m.vanish.push(pipoV); | |
191 | } | |
192 | }); | |
193 | // Special case of the king knight's movement: | |
194 | if (this.getPiece(x, y) == V.KING) { | |
195 | V.steps[V.KNIGHT].forEach(step => { | |
196 | const endX = x + step[0]; | |
197 | const endY = y + step[1]; | |
198 | if ( | |
199 | V.OnBoard(endX, endY) && | |
200 | [...Array(S-1).keys()].some(i => { | |
201 | return endX == squares[i].x && endY == squares[i].y; | |
202 | }) | |
203 | ) { | |
204 | let enpassantMove = this.getBasicMove([x, y], [endX, endY]); | |
205 | enpassantMove.vanish.push(pipoV); | |
206 | moves.push(enpassantMove); | |
207 | } | |
208 | }); | |
209 | } | |
210 | return moves; | |
211 | } | |
212 | ||
213 | static get VALUES() { | |
214 | return { | |
215 | p: 1, | |
216 | r: 5, | |
217 | n: 4, | |
218 | b: 3, | |
219 | q: 9, | |
220 | k: 1000 | |
221 | }; | |
222 | } | |
223 | }; |