import { NodeDefinition, NodeLike, StatelessGraphNode, StatelessNodeDefinition, StatelessNodeType } from '../../types/graph';
/**
 * An instance of the [[ifPending]] node.
 * See the [[ifPending]] documentation to find out more.
 */
export interface IfPendingNode extends StatelessGraphNode<'ifPending', IfPendingNodeProperties> {
}
/**
 * A definition of the [[ifPending]] node.
 * See the [[ifPending]] documentation to find out more.
 */
export interface IfPendingNodeDefinition extends StatelessNodeDefinition<'ifPending', IfPendingNodeProperties> {
}
export declare type PendingFallbackGenerator = (previousValue: NodeDefinition | undefined) => NodeDefinition;
export interface IfPendingNodeProperties {
    target: NodeDefinition;
    fallback: PendingFallbackGenerator | NodeDefinition | NodeLike;
}
/**
 * The implementation of the [[ifPending]].
 * See the [[ifPending]] documentation to learn more.
 */
export declare const IfPendingNodeType: StatelessNodeType<'ifPending', IfPendingNodeProperties>;
/**
 * Creates a new instance of a [[ifPending]] node, which is a type of a [[NodeDefinition]] used when there's a need
 * to always return a value for a certain node even if the `target` is not resolved (is pending).
 * This node is used by Muster-React to decide whether a certain query is loading. It works in a similar way to the
 * [[ifError]] with a difference that the [[ifError]] provides a fallback for the [[error]], while this
 * node provides a fallback for the [[pending]].
 *
 * The `fallback` can be either a pre-defined [[NodeDefinition]] or a fallback generator. The fallback
 * generator receives a previous value the `target` was resolved to (undefined if this is the
 * first time `target` is being resolved) and is expected to return a [[NodeLike]].
 *
 *
 * @example **Prevent `pending` state**
 * ```ts
 * import muster, { fromPromise, ifPending, ref, value } from '@dws/muster';
 *
 * const app = muster({
 *   asyncName: fromPromise(() => Promise.resolve('Bob')),
 *   syncName: ifPending(
 *     (previous) => previous || value('Loading...'),
 *     ref('asyncName'),
 *   ),
 * });
 *
 * app.resolve(ref('syncName')).subscribe((name) => {
 *   console.log(name);
 * });
 *
 * // Console output:
 * // Loading...
 * // Bob
 * ```
 * This example shows how to use the [[ifPending]] to synchronously return a name. It makes sure
 * that the `asyncName` node does not block the query.
 */
export declare function ifPending(fallback: PendingFallbackGenerator | NodeDefinition | NodeLike, target: NodeDefinition | NodeLike): IfPendingNodeDefinition;
export declare function isIfPendingNodeDefinition(value: NodeDefinition): value is IfPendingNodeDefinition;