apollo.js

import { useMemo } from "react";
import createApolloClient from "./apollo-client";

let apolloClient;

export function initializeApollo(initialState = null) {
	const _apolloClient = apolloClient ?? createApolloClient();

	// If your page has Next.js data fetching methods that use Apollo Client,
	// the initial state gets hydrated here
	if (initialState) {
		// Get existing cache, loaded during client side data fetching
		const existingCache = _apolloClient.extract();

		// Restore the cache using the data passed from
		// getStaticProps/getServerSideProps combined with the existing cached data
		_apolloClient.cache.restore({ ...existingCache, ...initialState });
	}

	// For SSG and SSR always create a new Apollo Client
	if (typeof window === "undefined") return _apolloClient;

	// Create the Apollo Client once in the client
	if (!apolloClient) apolloClient = _apolloClient;
	return _apolloClient;
}

export function useApollo(initialState) {
	const store = useMemo(() => initializeApollo(initialState), [initialState]);
	return store;
}