import { ApolloClient, InMemoryCache, HttpLink, from } from '@apollo/client';
import { Config } from '../config';
import { WebSocketLink } from "@apollo/client/link/ws";
import { RetryLink } from "@apollo/client/link/retry";
import { onError } from "@apollo/client/link/error";
import { SubscriptionClient } from "subscriptions-transport-ws";
import { User } from '../types/user';

export function createClient(setLoggedIn: (boolean) => void) {
  const subscriptionClient = new SubscriptionClient(Config.subscriptionEndpoint, {
    reconnect: true,
  });
  
  const errorLink = onError(({ operation }) => {
    const { response } = operation.getContext();
    if (response.status === 401) setLoggedIn(false);
  });
  
  const retryLink = new RetryLink({attempts: {max: 2}}).split(
    (operation) => operation.operationName === 'subscription',
    new WebSocketLink(subscriptionClient),
    new HttpLink({ 
      uri: Config.graphQLEndpoint, 
      credentials: 'include',
    })
  );
  
  const cache = new InMemoryCache({});
  
  return new ApolloClient<any>({
    cache: cache,
    link: from([
      errorLink,
      retryLink
    ]),
    defaultOptions: {
      watchQuery: {
        fetchPolicy: 'cache-and-network',
        errorPolicy: 'ignore',
      },
      query: {
        fetchPolicy: 'network-only',
        errorPolicy: 'all',
      },
      mutate: {
        errorPolicy: 'all',
      },
    }
  });
}

export function mergeArrayByField<T>(fieldName: string) {
  return (existing: T[] = [], incoming: T[], { readField, mergeObjects }) => {
    const merged: any[] = existing ? existing.slice(0) : [];
    
    const objectFieldToIndex: Record<string, number> = Object.create(null);
    if (existing) {
      existing.forEach((obj, index) => {
        objectFieldToIndex[readField(fieldName, obj)] = index;
      });
    }

    incoming.forEach(obj => {
      const field = readField(fieldName, obj);
      const index = objectFieldToIndex[field];
      if (typeof index === "number") {
        merged[index] = mergeObjects(merged[index], obj);
      } else {
        objectFieldToIndex[name] = merged.length;
        merged.push(obj);
      }
    });
    
    return merged;
  }
}