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[vchess.git] / client / src / variants / Doublemove1.js
1 import { ChessRules } from "@/base_rules";
2 import { randInt } from "@/utils/alea";
3
4 export class Doublemove1Rules 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 this.turn = parsedFen.turn;
35 this.subTurn = 1;
36 }
37
38 getEnpassantCaptures([x, y], shiftX) {
39 let moves = [];
40 // En passant: always OK if subturn 1,
41 // OK on subturn 2 only if enPassant was played at subturn 1
42 // (and if there are two e.p. squares available).
43 const Lep = this.epSquares.length;
44 const epSquares = this.epSquares[Lep - 1]; //always at least one element
45 let epSqs = [];
46 epSquares.forEach(sq => {
47 if (sq) epSqs.push(sq);
48 });
49 if (epSqs.length == 0) return moves;
50 const oppCol = V.GetOppCol(this.getColor(x, y));
51 for (let sq of epSqs) {
52 if (
53 this.subTurn == 1 ||
54 (epSqs.length == 2 &&
55 // Was this en-passant capture already played at subturn 1 ?
56 // (Or maybe the opponent filled the en-passant square with a piece)
57 this.board[epSqs[0].x][epSqs[0].y] != V.EMPTY)
58 ) {
59 if (
60 sq.x == x + shiftX &&
61 Math.abs(sq.y - y) == 1 &&
62 // Add condition "enemy pawn must be present"
63 this.getPiece(x, sq.y) == V.PAWN &&
64 this.getColor(x, sq.y) == oppCol
65 ) {
66 let epMove = this.getBasicMove([x, y], [sq.x, sq.y]);
67 epMove.vanish.push({
68 x: x,
69 y: sq.y,
70 p: "p",
71 c: oppCol
72 });
73 moves.push(epMove);
74 }
75 }
76 }
77 return moves;
78 }
79
80 play(move) {
81 move.flags = JSON.stringify(this.aggregateFlags());
82 move.turn = this.turn + this.subTurn;
83 V.PlayOnBoard(this.board, move);
84 const epSq = this.getEpSquare(move);
85 if (this.movesCount == 0) {
86 // First move in game
87 this.turn = "b";
88 this.epSquares.push([epSq]);
89 this.movesCount = 1;
90 }
91 // Does this move give check on subturn 1? If yes, skip subturn 2
92 else if (this.subTurn == 1 && this.underCheck(V.GetOppCol(this.turn))) {
93 this.turn = V.GetOppCol(this.turn);
94 this.epSquares.push([epSq]);
95 move.checkOnSubturn1 = true;
96 this.movesCount++;
97 } else {
98 if (this.subTurn == 2) {
99 this.turn = V.GetOppCol(this.turn);
100 let lastEpsq = this.epSquares[this.epSquares.length - 1];
101 lastEpsq.push(epSq);
102 } else {
103 this.epSquares.push([epSq]);
104 this.movesCount++;
105 }
106 this.subTurn = 3 - this.subTurn;
107 }
108 this.postPlay(move);
109 }
110
111 postPlay(move) {
112 const c = move.turn.charAt(0);
113 const piece = move.vanish[0].p;
114 const firstRank = c == "w" ? V.size.x - 1 : 0;
115
116 if (piece == V.KING && move.appear.length > 0) {
117 this.kingPos[c][0] = move.appear[0].x;
118 this.kingPos[c][1] = move.appear[0].y;
119 this.castleFlags[c] = [V.size.y, V.size.y];
120 return;
121 }
122 const oppCol = V.GetOppCol(c);
123 const oppFirstRank = V.size.x - 1 - firstRank;
124 if (
125 move.start.x == firstRank && //our rook moves?
126 this.castleFlags[c].includes(move.start.y)
127 ) {
128 const flagIdx = (move.start.y == this.castleFlags[c][0] ? 0 : 1);
129 this.castleFlags[c][flagIdx] = V.size.y;
130 } else if (
131 move.end.x == oppFirstRank && //we took opponent rook?
132 this.castleFlags[oppCol].includes(move.end.y)
133 ) {
134 const flagIdx = (move.end.y == this.castleFlags[oppCol][0] ? 0 : 1);
135 this.castleFlags[oppCol][flagIdx] = V.size.y;
136 }
137 }
138
139 undo(move) {
140 this.disaggregateFlags(JSON.parse(move.flags));
141 V.UndoOnBoard(this.board, move);
142 if (this.movesCount == 1 || !!move.checkOnSubturn1 || this.subTurn == 2) {
143 // The move may not be full, but is fully undone:
144 this.epSquares.pop();
145 // Moves counter was just incremented:
146 this.movesCount--;
147 } else {
148 // Undo the second half of a move
149 let lastEpsq = this.epSquares[this.epSquares.length - 1];
150 lastEpsq.pop();
151 }
152 this.turn = move.turn[0];
153 this.subTurn = parseInt(move.turn[1]);
154 super.postUndo(move);
155 }
156
157 static get VALUES() {
158 return {
159 p: 1,
160 r: 5,
161 n: 3,
162 b: 3,
163 q: 7, //slightly less than in orthodox game
164 k: 1000
165 };
166 }
167
168 // No alpha-beta here, just adapted min-max at depth 2(+1)
169 getComputerMove() {
170 const maxeval = V.INFINITY;
171 const color = this.turn;
172 const oppCol = V.GetOppCol(this.turn);
173
174 // Search best (half) move for opponent turn
175 const getBestMoveEval = () => {
176 let score = this.getCurrentScore();
177 if (score != "*") {
178 if (score == "1/2") return 0;
179 return maxeval * (score == "1-0" ? 1 : -1);
180 }
181 let moves = this.getAllValidMoves();
182 let res = oppCol == "w" ? -maxeval : maxeval;
183 for (let m of moves) {
184 this.play(m);
185 score = this.getCurrentScore();
186 // Now turn is oppCol,2 if m doesn't give check
187 // Otherwise it's color,1. In both cases the next test makes sense
188 if (score != "*") {
189 if (score == "1/2")
190 res = oppCol == "w" ? Math.max(res, 0) : Math.min(res, 0);
191 else {
192 // Found a mate
193 this.undo(m);
194 return maxeval * (score == "1-0" ? 1 : -1);
195 }
196 }
197 const evalPos = this.evalPosition();
198 res = oppCol == "w" ? Math.max(res, evalPos) : Math.min(res, evalPos);
199 this.undo(m);
200 }
201 return res;
202 };
203
204 let moves11 = this.getAllValidMoves();
205 let doubleMoves = [];
206 // Rank moves using a min-max at depth 2
207 for (let i = 0; i < moves11.length; i++) {
208 this.play(moves11[i]);
209 if (this.turn != color) {
210 // We gave check with last move: search the best opponent move
211 doubleMoves.push({ moves: [moves11[i]], eval: getBestMoveEval() });
212 } else {
213 let moves12 = this.getAllValidMoves();
214 for (let j = 0; j < moves12.length; j++) {
215 this.play(moves12[j]);
216 doubleMoves.push({
217 moves: [moves11[i], moves12[j]],
218 eval: getBestMoveEval()
219 });
220 this.undo(moves12[j]);
221 }
222 }
223 this.undo(moves11[i]);
224 }
225
226 doubleMoves.sort((a, b) => {
227 return (color == "w" ? 1 : -1) * (b.eval - a.eval);
228 });
229 let candidates = [0]; //indices of candidates moves
230 for (
231 let i = 1;
232 i < doubleMoves.length && doubleMoves[i].eval == doubleMoves[0].eval;
233 i++
234 ) {
235 candidates.push(i);
236 }
237
238 const selected = doubleMoves[randInt(candidates.length)].moves;
239 if (selected.length == 1) return selected[0];
240 return selected;
241 }
242 };