claude (duplicate_chess)
52 lines
1.8 KiB
TypeScript
52 lines
1.8 KiB
TypeScript
import type { DuplicateGame } from './game';
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import type { GameStatus, GameResult, BoardId } from './types';
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import { PLAYERS, PLAYER_BOARDS, BOARD_PLAYERS } from './boards';
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import { legalSyncedMoves } from './legality';
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/** PROVISIONAL (spec §6): the 50-move rule fires after this many rounds. */
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const FIFTY_MOVE_ROUNDS = 50;
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const FIFTY_MOVE_PLIES = FIFTY_MOVE_ROUNDS * 4;
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function allDraw(): GameResult {
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return { N: 'draw', S: 'draw', E: 'draw', W: 'draw' };
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}
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/** Evaluate the game from the perspective of the player to move. */
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export function evaluateStatus(game: DuplicateGame): GameStatus {
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const player = game.currentPlayer;
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const [a, b] = PLAYER_BOARDS[player];
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const checks: BoardId[] = [];
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if (game.boards[a].inCheck()) checks.push(a);
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if (game.boards[b].inCheck()) checks.push(b);
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const synced = legalSyncedMoves(game);
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if (synced.length === 0) {
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if (checks.length > 0) {
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// Checkmate. PROVISIONAL (spec §6): every opponent delivering a check wins.
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const winners = checks.map((board) =>
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BOARD_PLAYERS[board].w === player
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? BOARD_PLAYERS[board].b
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: BOARD_PLAYERS[board].w,
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);
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const result = {} as GameResult;
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for (const p of PLAYERS) {
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result[p] = p === player ? 'loss' : winners.includes(p) ? 'win' : 'draw';
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}
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return { state: 'checkmate', result, checks };
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}
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// PROVISIONAL (spec §6): a no-synchronized-move stalemate ends the game, all draw.
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return { state: 'stalemate', result: allDraw(), reason: 'stalemate', checks };
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}
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if (game.repetitionCount() >= 3) {
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return { state: 'draw', result: allDraw(), reason: 'threefold', checks };
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}
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if (game.pliesSinceProgress >= FIFTY_MOVE_PLIES) {
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return { state: 'draw', result: allDraw(), reason: 'fifty-move', checks };
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}
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return { state: 'playing', checks };
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}
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