import { IEnumerator } from '../enumerator';
import type { IEnumerable } from '../enumerable';
/**
 * A symbol, indicating to the state machine
 * that the sequence has no more elements.
 */
export declare const DONE: unique symbol;
export declare type Next<T> = typeof DONE | T;
declare type EnumeratorStateMachineSetup<T> = () => EnumeratorStateMachineNextGenerator<T>;
declare type EnumeratorStateMachineNextGenerator<T> = () => T | typeof DONE;
export declare const enum EnumeratorState {
    /**
     * The state machine will be set to this state, if the
     * sequence has no more elements.
     */
    Stop = -1,
    /**
     * Sets up variables like the enumerator for iteration.
     * This happens, when moveNext is called while the state is Setup.
     * The State will then be set to Stop.
     */
    Setup = 0,
    /**
     * Is set after the `next` call to get the next
     * element of the sequence. If `next` returns DONE, the state
     * will be kept as `Stop`.
     */
    HasNextElement = 1
}
/**
 * An alternative implementation to the JavaScript
 * generator function that uses a bit more memory
 * but is significantly faster.
 */
export declare abstract class EnumeratorStateMachine<TEnumerator, TEnumerable extends TEnumerator = NonNullable<TEnumerator>> implements IEnumerator<TEnumerator> {
    current?: TEnumerator;
    protected state: EnumeratorState;
    /**
     * Creates a new instance of a state machine
     * using the setup function to create the next generator.
     */
    static create<T>(setup: EnumeratorStateMachineSetup<T>): EnumeratorStateMachine<T>;
    /**
     * Resets the internal state to be `Setup`.
     */
    reset(): void;
    moveNext(): boolean;
    /**
     * Returns the next value, the enumerator
     * should return or DONE if the sequence
     * has no more elements.
     */
    abstract next(): Next<TEnumerator>;
    /**
     * Sets up the state machine;
     * this is called the first time moveNext
     * is called or after the state machine is reset.
     */
    abstract setup(): void;
    getEnumerator(): IEnumerator<TEnumerable>;
    [Symbol.iterator](): Iterator<TEnumerable>;
}
export interface EnumeratorStateMachine<TEnumerator, TEnumerable extends TEnumerator = NonNullable<TEnumerator>> extends IEnumerable<TEnumerable> {
}
export {};