import type { IAction, IActorArgs, IActorOutput, IActorTest, Mediate } from '@comunica/core';
import { Actor } from '@comunica/core';
import type { MetadataBindings } from '@comunica/types';
/**
 * A comunica actor for rdf-metadata-accumulate events.
 *
 * Actor types:
 * * Input:  IActionRdfMetadataAccumulate:      The metadata objects to accumulate,
 *                                              or a trigger for initializing a new value.
 * * Test:   <none>
 * * Output: IActorRdfMetadataAccumulateOutput: The accumulated metadata object.
 *
 * @see IActionRdfMetadataAccumulate
 * @see IActorRdfMetadataAccumulateOutput
 */
export declare abstract class ActorRdfMetadataAccumulate<TS = undefined> extends Actor<IActionRdfMetadataAccumulate, IActorTest, IActorRdfMetadataAccumulateOutput, TS> {
    /**
     * @param args -
     *   \ @defaultNested {<default_bus> a <cc:components/Bus.jsonld#Bus>} bus
     *   \ @defaultNested {Metadata accumulation failed: none of the configured actors were able to accumulate metadata in mode ${action.mode}} busFailMessage
     */
    constructor(args: IActorRdfMetadataAccumulateArgs<TS>);
}
export type IActionRdfMetadataAccumulate = IActionRdfMetadataAccumulateInitialize | IActionRdfMetadataAccumulateAppend;
export interface IActionRdfMetadataAccumulateInitialize extends IAction {
    /**
     * Indicates that metadata fields should be initialized to default values.
     */
    mode: 'initialize';
}
export interface IActionRdfMetadataAccumulateAppend extends IAction {
    /**
     * Indicates that metadata fields should be accumulated.
     * The initialize step is guaranteed to have been called before this on the `accumulatedMetadata` object.
     */
    mode: 'append';
    /**
     * The metadata object that already has some accumulated fields.
     * This object should not be mutated.
     */
    accumulatedMetadata: MetadataBindings;
    /**
     * The metadata object with fields to append.
     * This object should not be mutated.
     */
    appendingMetadata: MetadataBindings;
}
export interface IActorRdfMetadataAccumulateOutput extends IActorOutput {
    /**
     * The initialized or accumulated metadata object.
     * This should only contain those fields that are applicable to this actor.
     */
    metadata: Partial<MetadataBindings>;
}
export type IActorRdfMetadataAccumulateArgs<TS = undefined> = IActorArgs<IActionRdfMetadataAccumulate, IActorTest, IActorRdfMetadataAccumulateOutput, TS>;
export type MediatorRdfMetadataAccumulate = Mediate<IActionRdfMetadataAccumulate, IActorRdfMetadataAccumulateOutput>;