import { ApolloClient, HttpLink, InMemoryCache } from "@apollo/client";
import { RetryLink } from "@apollo/client/link/retry";

const directionalLink = new RetryLink().split(
  (operation) => operation.getContext().version === 1,
  new HttpLink({ uri: "http://localhost:4000/v1/graphql" }),
  new HttpLink({ uri: "http://localhost:4000/v2/graphql" })
);

const client = new ApolloClient({
  cache: new InMemoryCache(),
  link: directionalLink,
});

import { ApolloLink, HttpLink } from '@apollo/client';
import { RetryLink } from '@apollo/client/link/retry';

const directionalLink = new RetryLink().split(
  (operation) => operation.getContext().version === 1,
  new HttpLink({ uri: "http://localhost:4000/v1/graphql" }),
  new HttpLink({ uri: "http://localhost:4000/v2/graphql" })
);

import { ApolloClient, InMemoryCache } from '@apollo/client';

// ...code from the above example goes here...

const client = new ApolloClient({
  link: splitLink,
  cache: new InMemoryCache()
});

import { split, HttpLink } from '@apollo/client';
import { getMainDefinition } from '@apollo/client/utilities';
import { GraphQLWsLink } from '@apollo/client/link/subscriptions';
import { createClient } from 'graphql-ws';

const httpLink = new HttpLink({
  uri: 'http://localhost:4000/graphql'
});

const wsLink = new GraphQLWsLink(createClient({
  url: 'ws://localhost:4000/subscriptions',
}));

// The split function takes three parameters:
//
// * A function that's called for each operation to execute
// * The Link to use for an operation if the function returns a "truthy" value
// * The Link to use for an operation if the function returns a "falsy" value
const splitLink = split(
  ({ query }) => {
    const definition = getMainDefinition(query);
    return (
      definition.kind === 'OperationDefinition' &&
      definition.operation === 'subscription'
    );
  },
  wsLink,
  httpLink,
);

import { ApolloClient, InMemoryCache } from '@apollo/client';

const client = new ApolloClient({
  cache: new InMemoryCache({
    typePolicies: {
      Query: {
        fields: {
          book: {
            read(_, { args, toReference }) {
              return toReference({
                __typename: 'Book',
                id: args.id,
              });
            }
          }
        }
      }
    }
  })
});