import { TrainData } from '../game/TrainData';
import { AiAction, AiObservation, AiPlayAction, CandidateGenerator } from './types';
/**
 * Indices (into `obs.trains`) the player may legally build on under standard
 * Mexican Train access: your own train, plus any train flagged public. Games
 * with richer access rules (Warp12's Distress Beacon, locked fractures, …)
 * supply their own {@link CandidateGenerator}.
 */
export declare function getAccessibleTrainIndices(obs: AiObservation): number[];
/** Union of every played tile's key across all trains (uniqueness is global). */
export declare function collectAllPlayedKeys(trains: readonly TrainData[]): Set<string>;
/** Every legal placement of a hand tile onto an accessible train. */
export declare function generatePlayActions(obs: AiObservation): AiPlayAction[];
export interface CandidateGeneratorOptions {
    /**
     * Offer `draw` even when legal plays exist. Off by default (canonical "must
     * play if you can"). Turn on for variants where drawing is always optional —
     * combined with a high blunder rate this is what makes a beginner draw when
     * they didn't have to.
     */
    allowOptionalDraw?: boolean;
}
/**
 * Builds the standard candidate set: all legal plays, plus `draw` when the pile
 * isn't empty (and either there are no plays, or optional drawing is enabled),
 * falling back to `pass` only when nothing else is possible.
 */
export declare function createCandidateGenerator(options?: CandidateGeneratorOptions): CandidateGenerator<AiAction>;
export declare const defaultCandidateGenerator: CandidateGenerator<AiAction>;