ThinkDeepTech/thinkdeep

import {ApolloLink, Observable} from '@apollo/client/core';

import {print} from 'graphql';
import {createClient} from 'graphql-ws';

/**
 * Web socker link used to tie apollo and graphql-ws together.
 *
 * See: https://github.com/enisdenjo/graphql-ws in the recipes section.
 */
class WebSocketLink extends ApolloLink {
  /**
   * @param {Object} clientOptions
   * @param {Object} request
   */
  constructor(clientOptions, request) {
    super(request);
    this.client = createClient(clientOptions);
  }

  /**
   * Function to call on request.
   * @param {Object} operation
   * @return {Observable}
   */
  request(operation) {
    return new Observable((sink) => {
      return this.client.subscribe(
        {...operation, query: print(operation.query)},
        {
          next: sink.next.bind(sink),
          complete: sink.complete.bind(sink),
          error: (err) => {
            if (Array.isArray(err))
              return sink.error(
                new Error(err.map(({message}) => message).join(', '))
              );

            if (err instanceof CloseEvent)
              return sink.error(
                new Error(
                  `Socket closed with event ${err.code} ${err.reason || ''}` // reason will be available on clean closes only
                )
              );

            return sink.error(err);
          },
        }
      );
    });
  }
}

export {WebSocketLink};