import { Milliseconds } from '@kameleoon/javascript-sdk-core';
import { CredentialsType } from './types';
export declare const SILENCE_PERIOD: number;
export declare const TOKEN_EXPIRATION_GAP = Milliseconds.Minute;
export declare const TOKEN_OBSOLESCENCE_GAP: number;
export type AccessTokenResponseType = {
    accessToken: string;
    expiresIn: number;
};
/**
 * Performs one access token request with the given `Authorization` header value;
 * must reject on any failure (network error, abort, non-2xx status, malformed body)
 */
export type FetchAccessTokenType = (basicAuthToken: string, signal: AbortSignal) => Promise<AccessTokenResponseType>;
/**
 * Caches the OAuth access token and refreshes it in the background before it expires.
 * Concurrent callers share one in-flight request, which is bounded by `requestTimeout`
 * independently of the callers. After a failed request the token is not requested for
 * `SILENCE_PERIOD`; callers get `null` and proceed without it.
 */
export declare class AccessTokenSource {
    private readonly basicAuthToken;
    private readonly fetchAccessToken;
    private readonly requestTimeout;
    private cachedToken;
    private silentAfterFetchFailureUntil;
    private fetching;
    constructor({ clientId, clientSecret }: CredentialsType, fetchAccessToken: FetchAccessTokenType, requestTimeout: number);
    /**
     * @param signal - the caller's own signal; once it aborts the caller gets `null`
     * while the shared fetch carries on for the other waiters and the cache
     */
    getToken(signal: AbortSignal | null): Promise<string | null>;
    discardToken(token: string | null): void;
    private fetchToken;
    private waitForFetch;
    private performFetch;
    private newExpiringToken;
}
export declare class ExpiringToken {
    readonly value: string;
    readonly expirationTime: number;
    readonly obsolescenceTime: number;
    constructor(value: string, expirationTime: number, obsolescenceTime: number);
    isExpired(now: number): boolean;
    isObsolete(now: number): boolean;
}