export interface IStreamObserver<T> {
    next?(value: T): void;
    error?(error: any): void;
    complete?(): void;
}
export interface ISubscription {
    unsubscribe(): void;
}
export interface IObservableStream<T> {
    subscribe(observer?: IStreamObserver<T> | null): ISubscription;
    subscribe(observer?: ((value: T) => void) | null): ISubscription;
}
/**
 * Converts an expression to an observable stream (a.k.a. TC 39 Observable / RxJS observable).
 * The provided expression is tracked by mobx as long as there are subscribers, automatically
 * emitting when new values become available. The expressions respect (trans)actions.
 *
 * @example
 *
 * const user = observable({
 *   firstName: "C.S",
 *   lastName: "Lewis"
 * })
 *
 * Rx.Observable
 *   .from(mobxUtils.toStream(() => user.firstname + user.lastName))
 *   .scan(nameChanges => nameChanges + 1, 0)
 *   .subscribe(nameChanges => console.log("Changed name ", nameChanges, "times"))
 *
 * @export
 * @template T
 * @param {() => T} expression
 * @param {boolean} fireImmediately (by default false)
 * @returns {IObservableStream<T>}
 */
export declare function toStream<T>(expression: () => T, fireImmediately?: boolean): IObservableStream<T>;
/**
 * Converts a subscribable, observable stream (TC 39 observable / RxJS stream)
 * into an object which stores the current value (as `current`). The subscription can be cancelled through the `dispose` method.
 * Takes an initial value as second optional argument
 *
 * @example
 * const debouncedClickDelta = MobxUtils.fromStream(Rx.Observable.fromEvent(button, 'click')
 *     .throttleTime(1000)
 *     .map(event => event.clientX)
 *     .scan((count, clientX) => count + clientX, 0)
 * )
 *
 * autorun(() => {
 *     console.log("distance moved", debouncedClickDelta.current)
 * })
 */
export declare function fromStream<T>(observable: IObservableStream<T>): IStreamListener<T | undefined>;
export declare function fromStream<T, I>(observable: IObservableStream<T>, initialValue: I): IStreamListener<T | I>;
export interface IStreamListener<T> {
    current: T;
    dispose(): void;
}