export declare type Listener<T> = (payload: T) => void;
export interface BaseSignal<T> {
    add(listener: Listener<T>, ...tags: any[]): void;
    remove(listenerOrTag: any): void;
}
export interface ReadableSignal<T> extends BaseSignal<T> {
    addOnce(listener: Listener<T>, ...tags: any[]): void;
    filter<U extends T>(filter: (payload: T) => payload is U): ReadableSignal<U>;
    filter(filter: (payload: T) => boolean): ReadableSignal<T>;
    map<U>(transform: (payload: T) => U): ReadableSignal<U>;
    merge<U>(...signals: ReadableSignal<U>[]): ReadableSignal<T | U>;
    promisify(rejectSignal?: ReadableSignal<any>): Promise<T>;
    peek(peekaboo: (payload: T) => void): ReadableSignal<T>;
    readOnly(): ReadableSignal<T>;
    cache(cache: Cache<T>): ReadableSignal<T>;
    reduce<U>(accumulator: Accumulator<T, U>, initialValue: U): ReadableSignal<U>;
}
export interface WritableSignal<T> {
    dispatch: (payload: T) => void;
    /**
     * set a listener to be called if no other listeners are available.
     */
    setDefaultListener(listener: Listener<T>): void;
}
export interface Cache<T> {
    add(payload: T): void;
    forEach(callback: (payload: T) => void): void;
}
export declare type Accumulator<T, U> = (accum: U, current: T) => any;
export declare type PayloadOf<S extends BaseSignal<any>> = S extends BaseSignal<infer T> ? T : never;
export declare type ReadOnlyVersionOf<S extends BaseSignal<any>> = S extends BaseSignal<infer T> ? ReadableSignal<T> : never;