// https://github.com/vercel/next.js/blob/canary/examples/with-typescript-graphql/lib/apollo.ts

import {
  ApolloClient,
  InMemoryCache,
  NormalizedCacheObject,
} from "@apollo/client";
import { Context } from "nexus-plugin-prisma/typegen";
import { useMemo } from "react";

let apolloClient: ApolloClient<NormalizedCacheObject> | undefined;

function createIsomorphLink(context: Context | {} = {}) {
  if (typeof window === "undefined") {
    const { SchemaLink } = require("@apollo/client/link/schema");
    const { schema } = require("graphql/schema");
    return new SchemaLink({ schema, context });
  } else {
    const { HttpLink } = require("@apollo/client");
    return new HttpLink({
      uri: "/api/graphql",
      credentials: "same-origin",
    });
  }
}

function createApolloClient(context?: Context) {
  return new ApolloClient({
    ssrMode: typeof window === "undefined",
    link: createIsomorphLink(context),
    cache: new InMemoryCache({
      typePolicies: {
        User: {
          fields: {
            profile: {
              merge: false,
            },
          },
        },
      },
    }),
  });
}

export function initializeApollo(
  initialState: any = null,
  // Pages with Next.js data fetching methods, like `getStaticProps`, can send
  // a custom context which will be used by `SchemaLink` to server render pages
  context?: Context
) {
  const _apolloClient = apolloClient ?? createApolloClient(context);

  // If your page has Next.js data fetching methods that use Apollo Client, the initial state
  // get hydrated here
  if (initialState) {
    _apolloClient.cache.restore(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: any) {
  const store = useMemo(() => initializeApollo(initialState), [initialState]);
  return store;
}