import type { FetchEngineCore } from '../engine/types.ts';
/**
 * Manages instance state for FetchEngine with event emission.
 *
 * Provides a clean API for getting, setting, and resetting state
 * with automatic event emission on mutations. Validation is pulled
 * from engine options, not passed as a constructor parameter.
 *
 * @template S - State type
 *
 * @example
 * ```typescript
 * // Access via engine.state
 * engine.state.set('authToken', 'bearer-123');
 * engine.state.set({ user: 'john', role: 'admin' });
 *
 * const state = engine.state.get();
 * console.log(state.authToken);
 *
 * engine.state.reset();
 * ```
 */
export declare class FetchState<S> {
    constructor(engine: FetchEngineCore<unknown, unknown, S>);
    /**
     * Get a deep clone of the current state.
     *
     * Returns a cloned copy to prevent external mutations.
     *
     * @example
     * ```typescript
     * const state = engine.state.get();
     * console.log(state.authToken);
     * ```
     */
    get(): S;
    /**
     * Set state by key-value or by partial object merge.
     *
     * Emits 'state-set' event after successful update.
     *
     * @example
     * ```typescript
     * // Set single property
     * engine.state.set('authToken', 'bearer-123');
     *
     * // Merge multiple properties
     * engine.state.set({ user: 'john', role: 'admin' });
     * ```
     */
    set<K extends keyof S>(key: K, value: S[K]): void;
    set(partial: Partial<S>): void;
    /**
     * Reset state to empty object.
     *
     * Emits 'state-reset' event after reset.
     *
     * @example
     * ```typescript
     * engine.state.reset();
     * console.log(engine.state.get()); // {}
     * ```
     */
    reset(): void;
    /**
     * Internal method to set state directly without events.
     * Used during engine initialization.
     * @internal
     */
    _setDirect(state: S): void;
}