import type { RefreshErrorCode } from "./ConfigServiceBase.js";
import type { ProjectConfig } from "./ProjectConfig.js";
import type { Message } from "./Utils.js";
export declare enum FetchStatus {
    Fetched = 0,
    NotModified = 1,
    Errored = 2
}
export type FetchResult = {
    readonly config: ProjectConfig;
} & ({
    readonly status: FetchStatus.Fetched | FetchStatus.NotModified;
    readonly errorCode: RefreshErrorCode.None;
    readonly errorMessage?: undefined;
    readonly errorException?: undefined;
} | {
    readonly status: FetchStatus.Errored;
    readonly errorCode: Exclude<RefreshErrorCode, RefreshErrorCode.None>;
    readonly errorMessage: Message;
    readonly errorException?: any;
});
export declare function fetchResultFromSuccess(config: ProjectConfig): FetchResult;
export declare function fetchResultFromNotModified(config: ProjectConfig): FetchResult;
export declare function fetchResultFromError(config: ProjectConfig, errorCode: Exclude<RefreshErrorCode, RefreshErrorCode.None>, errorMessage: Message, errorException?: any): FetchResult;
/** The request parameters for a ConfigCat config fetch operation. */
export declare class FetchRequest {
    /** The URL of the config. */
    readonly url: string;
    /**
     * The value of the `ETag` HTTP response header received during the last successful request (if any).
     * If available, should be included in the HTTP request, either in the `If-None-Match` header or in the `ccetag` query string parameter.
     *
     * @remarks In browser runtime environments the `If-None-Match` header should be avoided because that may cause unnecessary CORS preflight requests.
     */
    readonly lastETag: string | undefined;
    /** Additional HTTP request headers. Should be included in every HTTP request. */
    readonly headers: ReadonlyArray<readonly [name: string, value: string]>;
    /** The request timeout to apply, configured via `IOptions.requestTimeoutMs`. */
    readonly timeoutMs: number;
    constructor(
    /** The URL of the config. */
    url: string, 
    /**
     * The value of the `ETag` HTTP response header received during the last successful request (if any).
     * If available, should be included in the HTTP request, either in the `If-None-Match` header or in the `ccetag` query string parameter.
     *
     * @remarks In browser runtime environments the `If-None-Match` header should be avoided because that may cause unnecessary CORS preflight requests.
     */
    lastETag: string | undefined, 
    /** Additional HTTP request headers. Should be included in every HTTP request. */
    headers: ReadonlyArray<readonly [name: string, value: string]>, 
    /** The request timeout to apply, configured via `IOptions.requestTimeoutMs`. */
    timeoutMs: number);
}
/** The response data of a ConfigCat config fetch operation. */
export declare class FetchResponse {
    /** The HTTP status code. */
    readonly statusCode: number;
    /** The HTTP reason phrase. */
    readonly reasonPhrase: string;
    /** The response body. */
    readonly body?: string | undefined;
    /** The value of the `ETag` HTTP response header. */
    readonly eTag?: string;
    private readonly rayId?;
    constructor(
    /** The HTTP status code. */
    statusCode: number, 
    /** The HTTP reason phrase. */
    reasonPhrase: string, 
    /** The HTTP response headers. */
    headers: ReadonlyArray<readonly [name: string, value: string]>, 
    /** The response body. */
    body?: string | undefined);
}
export type FetchErrorCauses = {
    abort: [];
    timeout: [timeoutMs: number];
    failure: [err?: any];
};
export declare class FetchError<TCause extends keyof FetchErrorCauses = keyof FetchErrorCauses> extends Error {
    cause: TCause;
    readonly name: string;
    readonly args: FetchErrorCauses[TCause];
    constructor(cause: TCause, ...args: FetchErrorCauses[TCause]);
}
/** Defines the interface used by the ConfigCat SDK to perform ConfigCat config fetch operations. */
export interface IConfigCatConfigFetcher {
    /**
     * Fetches the JSON content of the requested config asynchronously.
     * @param request The fetch request.
     * @returns A promise that fulfills with the fetch response.
     * @throws {FetchErrorException} The fetch operation failed.
     */
    fetchAsync(request: FetchRequest): Promise<FetchResponse>;
}