nats-micro/src/types/broker.ts

NATS micro compatible extra-lightweight microservice library

import { MaybePromise, PartialBy } from './types.js';

export type Headers = Iterable<[string, string]>;

export type HandlerInfo = {
  microservice?: string;
  method: string;
};

export type RequestContext = Record<string, unknown>

export interface Request<T> {
  data: T;
  subject: string;
  headers?: Headers;
  handler: HandlerInfo;
  context?: RequestContext;
}

export const noResponse = Symbol('no reponse');

export type ResponseData<R> = {
  data: R | symbol;
  headers: [string, string][];
};

export type Response<R> = {
  get closeWaiter(): Promise<ResponseData<R>>;
  get isClosed(): boolean;
  setHeaders: (headers: Headers) => void;
  send: (data: R) => void;
  sendNoResponse: () => void;
};

export type Handler<T, R, RR = MaybePromise<void>> = (req: Request<T>, res: Response<R>) => RR;

export type MicroserviceSubject = {
  microservice: string;
  instance?: string; // for calls to "local" methods
};

export type RawSubject = string;

export type MethodSubject = MicroserviceSubject & {
  method: string;
};

export type Subject = RawSubject | MethodSubject;

export type Message<T> = {
  data: T,
  headers?: Headers,
};

export type MessageReplyTo<T> = Message<T> & {
  replyTo: RawSubject,
};

export type MessageMaybeReplyTo<T> = PartialBy<MessageReplyTo<T>, 'replyTo'>;

export type MessageHandler<T> = (data: MessageMaybeReplyTo<T>, subject: string) => void;

export type BrokerResponse<T> = Message<T> & {
  subject: string;
  error?: Error;
};

export type RequestOptions = Pick<Message<unknown>, 'headers'> & {
  timeout?: number;
};

export type RequestManyOptions = RequestOptions & {
  limit?: number, // -1 for unlimited
};

export type SendOptions = Omit<MessageMaybeReplyTo<never>, 'data'>;

export const headersPrefixContext = 'context-';