import { TwirpError } from "../error/index.js";
import { Emitter } from "../eventEmitter/index.js";
export type ClientConfiguration = Partial<{
    /**
     * The base URL for the RPC. The service path will be appended to this string.
     */
    baseURL: string;
    /**
     * HTTP headers to include in the RPC.
     */
    headers: Record<string, string>;
    /**
     * A path prefix such as "/my/custom/prefix". Defaults to "/twirp", but can be set to "".
     */
    prefix: string;
    /**
     * The transport to use for the RPC. Defaults to `fetch`. Overrides must conform to a subset of the fetch interface defined by the `RpcTransport` type.
     */
    rpcTransport: RpcTransport;
}>;
interface MiddlewareConfig {
    /**
     * The URL for the RPC. This is the full URL for the request: the baseURL + prefix + the service path.
     */
    url: string;
    /**
     * HTTP headers to include in the RPC.
     */
    headers: Record<string, string>;
    /**
     * The transport to use for the RPC. Defaults to `fetch`, but will use `nodeHttpTransport` in Node.js environments. Overrides must conform to a subset of the fetch interface defined by the `RpcTransport` type.
     */
    rpcTransport: RpcTransport;
}
type ClientMiddleware<T = unknown> = (context: MiddlewareConfig, next: (context: MiddlewareConfig) => Promise<T>) => Promise<T>;
type HookListener<MiddlewareConfig> = (context: Readonly<MiddlewareConfig>) => void;
type ErrorHookListener<MiddlewareConfig> = (context: Readonly<MiddlewareConfig>, err: TwirpError) => void;
type ClientHooks<MiddlewareConfig> = {
    requestPrepared: HookListener<MiddlewareConfig>;
    responseReceived: HookListener<MiddlewareConfig>;
    error: ErrorHookListener<MiddlewareConfig>;
};
type TwirpClientEvent<MiddlewareConfig> = Emitter<ClientHooks<MiddlewareConfig>>;
interface Client extends ClientConfiguration {
    /**
     * Registers middleware to manipulate the client request / response lifecycle.
     *
     * The middleware handler will receive `context` and `next` parameters. `context` sets the headers and url for the RPC. `next` invokes the next handler in the chain -- either the next registered middleware, or the Twirp RPC.
     *
     * Middleware is called in order of registration, with the Twirp RPC invoked last.
     */
    use: (middleware: ClientMiddleware) => Client;
    /**
     * Registers event handler that can instrument a Twirp-generated client.
     * These callbacks all accept the current request `context`.
     *
     * `requestPrepared` is called as soon as a request has been created and before it has been sent to the Twirp server.
     *
     * `responseReceived` is called after a request has finished sending.
     *
     * `error` is called when an error occurs during the sending or receiving of a request. In addition to `context`, the error that occurred is passed as the second argument.
     */
    on: (...args: Parameters<TwirpClientEvent<MiddlewareConfig>["on"]>) => this;
    /**
     * Removes a registered event handler.
     */
    off: (...args: Parameters<TwirpClientEvent<MiddlewareConfig>["off"]>) => this;
    /**
     * The transport to use for the RPC. Defaults to `fetch`, but will use `nodeHttpTransport` in Node.js environments. Overrides must conform to a subset of the fetch interface defined by the `RpcTransport` type.
     */
    rpcTransport: RpcTransport;
}
export interface RpcTransportOpts {
    method: string;
    headers: Record<string, string>;
    body: string | Uint8Array | undefined | null;
}
/**
 * Subset of [Headers](https://developer.mozilla.org/en-US/docs/Web/API/Headers) from Fetch API. Redefined so that end users don't need to include lib.dom.d.ts in server only applications.
 */
interface Headers {
    get(name: string): string | null;
}
export interface RpcTransportResponse {
    arrayBuffer: () => Promise<ArrayBuffer>;
    json: () => Promise<unknown>;
    readonly headers: Headers;
    readonly ok: boolean;
    readonly status: number;
    text: () => Promise<string>;
}
export type RpcTransport = (url: string, opts: RpcTransportOpts) => Promise<RpcTransportResponse>;
/**
 * Global configuration for the TwirpScript clients.
 */
export declare const client: Client;
export declare function JSONrequest(path: string, body?: string, config?: ClientConfiguration): Promise<string>;
export declare function PBrequest(path: string, body?: Uint8Array, config?: ClientConfiguration): Promise<Uint8Array>;
export {};