import { Observable } from 'rxjs';
import { PolarisQuery, PolarisQueryResult } from './polaris-query';
/**
 * Common superclass that can be used for implementing `PolarisQuery` realizations.
 *
 * Since Polaris queries are supposed to be used as a fluent API, `PolarisQueryBase` is designed
 * to establish a chain of `PolarisQuery` instances, with each query referring to its predecessor.
 */
export declare abstract class PolarisQueryBase<T> implements PolarisQuery<T> {
    /**
     * The query that precedes this one in the chain.
     *
     * If this is the first query in the chain, this value is `null`.
     */
    protected readonly predecessor: PolarisQueryBase<T>;
    /**
     * Creates a new instance of `PolarisBaseQuery`.
     *
     * @param predecessor The query that precedes this one in the chain. This should be `null`,
     * if this is the first query in the chain.
     */
    protected constructor(predecessor: PolarisQueryBase<T>);
    execute(): Promise<PolarisQueryResult<T>>;
    toObservable(): Observable<PolarisQueryResult<T>>;
    /**
     * Executes the query and returns a promise that can be used to obtain the result.
     *
     * @param queryChain The entire query chain with the first element being the beginning of the chain
     * and the last element being the end of the chain (i.e., the query object on which `execute()` was called).
     * @returns A promise that resolves to the result of the query or rejects with an error.
     */
    protected abstract executeInternal(queryChain: PolarisQueryBase<T>[]): Promise<PolarisQueryResult<T>>;
    /**
     * Transforms the query into a cold observable, i.e., you must call `subscribe()`
     * on the observable to execute the query.
     *
     * If the underlying data store is a streaming engine, the observable may emit multiple times.
     *
     * @param queryChain The entire query chain with the first element being the beginning of the chain
     * and the last element being the end of the chain (i.e., the query object on which `toObservable()` was called).
     * @returns A cold observable for the query result.
     */
    protected abstract toObservableInternal(queryChain: PolarisQueryBase<T>[]): Observable<PolarisQueryResult<T>>;
    /**
     * Builds an array that represents the entire query chain.
     *
     * The first element is the beginning of the chain (e.g., the query that resulted from the `select()` call)
     * and the last element is the end of the chain (i.e., the query on which `execute()` or `toObservable()` was called).
     */
    protected buildQueryChain(): PolarisQueryBase<T>[];
}