import { HookSubscriber, TransformInput, TapInput, TapOutput } from '@known-as-bmf/hookable';
/**
 * A store instance.
 *
 * @public
 */
export interface Store<S> {
}
/**
 * Hooks available to middlewares.
 *
 * @public
 */
export interface Hooks<S> {
    /**
     * Register a function that will be invoked each time a state change is requested.
     * This function can transform the state and must return an array containing the new state.
     * An array must be returned because of implementation details behind the scene.
     *
     * @param fn - A state transformation function.
     */
    transformState: HookSubscriber<TransformInput<(state: S) => S>>;
    /**
     * Register a function that will be invoked when the state is about to change.
     * It is invoked after all `transformState` hooks.
     *
     * @param fn - A function invoked when the state is about to change.
     */
    stateWillChange: HookSubscriber<TapInput<(state: S) => S>>;
    /**
     * Register a function that will be invoked after the state changed.
     * It is invoked after all `transformState` and `stateWillChange` hooks.
     *
     * @param fn - A function invoked when the state has changed.
     */
    stateDidChange: HookSubscriber<TapOutput<(state: S) => S>>;
}
/**
 * Data provided when a subscription to state change is called.
 *
 * @public
 */
export interface StateChangedEvent<S> {
    /**
     * The previous value of the state.
     */
    previous: S;
    /**
     * The new value of the state.
     */
    current: S;
}
/**
 * State selector function.
 *
 * @public
 */
export declare type Selector<S, R> = (state: S) => R;
/**
 * Subscription callback function.
 *
 * @public
 */
export declare type SubscriptionCallback<S> = (event: StateChangedEvent<S>) => void;
/**
 * Middleware function signature.
 *
 * @public
 */
export declare type Middleware<S> = (store: Store<S>, hooks: Hooks<S>) => void;
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