import { StompHeaders } from '@stomp/stompjs';

/**
 * Options for [RxStomp#watch]{@link RxStomp#watch}.
 *
 * Part of `@stomp/rx-stomp`
 */
export interface IWatchParams {
  /**
   * The subscription target. It is likely to be broker dependent.
   */
  readonly destination?: string;

  /**
   * Subscription headers, defaults to `{}`
   *
   * If header information can change over time, and you are allowing automatic re-subscriptions,
   * consider using a callback as the value rather than a string literal.
   *
   * ```typescript
   *              const subHeadersCallback = () => {
   *                  return {bye: 'world'};
   *              };
   *              const sub = rxStomp.watch({ destination: queueName, subHeaders: subHeadersCallback})
   *                                 .subscribe((message) => {
   *                                    // handle message
   *                                 });
   *              // The subHeadersCallback will be invoked before every (re)subscription.
   * ```
   */
  readonly subHeaders?: StompHeaders | (() => StompHeaders);

  /**
   * Headers to be passed while unsubscribing, defaults to `{}`.
   *
   * Occasionally, headers may not be known while invoking [RxStomp#watch]{@link RxStomp#watch},
   * in such cases a callback can be passed that would return the headers.
   *
   * ```typescript
   *              const unsubHeadersCallback = () => {
   *                  return {bye: 'world'};
   *              };
   *              const sub = rxStomp.watch({ destination: queueName, unsubHeaders: unsubHeadersCallback})
   *                                 .subscribe((message) => {
   *                                    // handle message
   *                                 });
   *              // Unsubscribe from RxJS Observable, internally unsubscribe will be issued to the broker.
   *              // `unsubHeadersCallback` will be invoked to get the headers.
   *              sub.unsubscribe();
   * ```
   */
  readonly unsubHeaders?: StompHeaders | (() => StompHeaders);

  /**
   * By default, the destination will be subscribed after each successful (re)connection to the broker.
   * Set this flag to not automatically resubscribe.
   */
  readonly subscribeOnlyOnce?: boolean;
}