Method subscribe

packages/client/src/sync-engine.ts:591–670

* @hidden

(
    params: CollectionQuery<any, any>,
    options: {
      onQueryFulfilled?: () => void;
      onQueryError?: ErrorCallback;
      onQuerySyncStateChange?: SyncStateCallback;
    } = {}
  )

   * @hidden
   */
  async subscribe(
    params: CollectionQuery<any, any>,
    options: {
      onQueryFulfilled?: () => void;
      onQueryError?: ErrorCallback;
      onQuerySyncStateChange?: SyncStateCallback;
    } = {}
  ) {
    const { onQueryFulfilled, onQueryError, onQuerySyncStateChange } = options;
    const id = hashQuery(params);
    const queryHasMounted = this.queries.has(id);
    if (!queryHasMounted) {
      this.queries.set(id, {
        params,
        syncState: 'NOT_STARTED',
        syncStateCallbacks: new Set(),
        subCount: 0,
        hasSent: false,
        abortController: new AbortController(),
      });
    }
    // Safely using query! here because we just set it
    const query = this.queries.get(id)!;
    query.subCount++;

    if (onQuerySyncStateChange) {
      query.syncStateCallbacks.add(onQuerySyncStateChange);
    }
    let fulfillmentCallback: SyncStateCallback | undefined = undefined;

    if (onQueryFulfilled) {
      query.syncState === 'FULFILLED' && onQueryFulfilled();
      fulfillmentCallback = (state) => {
        if (state === 'FULFILLED') {
          onQueryFulfilled();
        }
      };
      query.syncStateCallbacks.add(fulfillmentCallback);
    }
    let errorCallback: SyncStateCallback | undefined = undefined;
    if (onQueryError) {
      errorCallback = (state, error) => {
        if (state === 'ERROR') {
          onQueryError(error);
        }
      };
      query.syncStateCallbacks.add(errorCallback);
    }
    if (!queryHasMounted) {
      await this.connectQuery(id);
    }

    return () => {
      const query = this.queries.get(id);
      // If we cannot find the query, we may have already disconnected or reset our state
      // just in case send a disconnect signal to the server
      if (!query) {
        this.disconnectQuery(id);