import { BehaviorSubject, Observable } from 'rxjs';
/**
 * State of an observable in the given moment.
 */
export declare enum SnapshotState {
    /**
     * Waiting for the first emission
     */
    WAITING = "WAITING",
    /**
     * Observable has already emitted
     */
    EMITTING = "EMITTING",
    /**
     * Observable has successfully completed emitting (there will be no more emissions)
     */
    COMPLETED = "COMPLETED",
    /**
     * Observable threw an error
     */
    FAILED = "FAILED"
}
/**
 * A tuple of latest emission, state of an observable and eventual error thrown by the observable.
 *
 * * value - latest emission of the observable or `null` if it hasn't started emitting yet and no default value was provided
 * * state - determines whether the observable already started emitting, whether it completed or failed (see [[SnapshotState]])
 * * error - eventual error thrown by the observable
 *
 * @typeParam T type of the emitted value
 * @typeParam S `null` determines that state is nullable, the only only other acceptable type is `never`
 */
export declare type Snapshot<T, S extends never | null = never> = [T, SnapshotState | S, Error | any | null];
export declare function useSnapshot<T>(observable: BehaviorSubject<T>): Snapshot<T>;
export declare function useSnapshot<T>(observable: Observable<T>): Snapshot<T | null>;
export declare function useSnapshot<T>(observable: Observable<T>, defaultValue: T): Snapshot<T>;
export declare function useSnapshot<T>(observable: BehaviorSubject<T> | undefined | null): Snapshot<T, null>;
export declare function useSnapshot<T>(observable: Observable<T> | undefined | null): Snapshot<T | null, null>;
export declare function useSnapshot<T>(observable: Observable<T> | undefined | null, defaultValue: T): Snapshot<T, null>;
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