apollo.js

import React, { useMemo } from 'react'
import App from 'next/app'
import Head from 'next/head'
import { ApolloProvider } from '@apollo/react-hooks'
import { ApolloClient } from 'apollo-client'
import { InMemoryCache } from 'apollo-cache-inmemory'
import { HttpLink } from 'apollo-link-http'
import fetch from 'isomorphic-unfetch'

let apolloClient = null

/**
 * Creates and provides the apolloContext
 * to a next.js PageTree. Use it by wrapping
 * your PageComponent via HOC pattern.
 * @param {Function|Class} PageComponent
 * @param {Object} [config]
 * @param {Boolean} [config.ssr=true]
 */
export function withApollo (PageComponent, { ssr = true } = {}) {
  const isAppHoc =
    PageComponent === App || PageComponent.prototype instanceof App

  const WithApollo = ({ apolloClient, apolloState, ...pageProps }) => {
    const client = useMemo(
      () => apolloClient || initApolloClient(apolloState),
      []
    )
    return (
      <ApolloProvider client={client}>
        <PageComponent {...pageProps} />
      </ApolloProvider>
    )
  }

  if (process.env.NODE_ENV !== 'production') {
    if (isAppHoc) {
      console.warn(
        'You are using the "withApollo" HOC on "_app.js" level. Please note that this disables project wide automatic static optimization. Better wrap your PageComponents directly.'
      )
    }
  }

  // Set the correct displayName in development
  if (process.env.NODE_ENV !== 'production') {
    const displayName =
      PageComponent.displayName || PageComponent.name || 'Component'

    WithApollo.displayName = `withApollo(${displayName})`
  }

  if (ssr || PageComponent.getInitialProps) {
    WithApollo.getInitialProps = async ctx => {
      const { AppTree } = ctx

      // Initialize ApolloClient, add it to the ctx object so
      // we can use it in `PageComponent.getInitialProp`.
      const apolloClient = (ctx.apolloClient = initApolloClient())

      // Run wrapped getInitialProps methods
      let pageProps = {}
      if (PageComponent.getInitialProps) {
        pageProps = await PageComponent.getInitialProps(ctx)
      }

      // Only on the server:
      if (typeof window === 'undefined') {
        // When redirecting, the response is finished.
        // No point in continuing to render
        if (ctx.res && ctx.res.finished) {
          return pageProps
        }

        // Only if ssr is enabled
        if (ssr) {
          try {
            // Run all GraphQL queries
            const { getDataFromTree } = await import('@apollo/react-ssr')

            // Since AppComponents and PageComponents have different context types
            // we need to modify their props a little.
            const props = isAppHoc
              ? { ...pageProps, apolloClient }
              : { pageProps: { ...pageProps, apolloClient } }

            await getDataFromTree(<AppTree {...props} />)
          } catch (error) {
            // Prevent Apollo Client GraphQL errors from crashing SSR.
            // Handle them in components via the data.error prop:
            // https://www.apollographql.com/docs/react/api/react-apollo.html#graphql-query-data-error
            console.error('Error while running `getDataFromTree`', error)
          }

          // getDataFromTree does not call componentWillUnmount
          // head side effect therefore need to be cleared manually
          Head.rewind()
        }
      }

      // Extract query data from the Apollo store
      const apolloState = apolloClient.cache.extract()

      return {
        ...pageProps,
        apolloState
      }
    }
  }

  return WithApollo
}

/**
 * Always creates a new apollo client on the server
 * Creates or reuses apollo client in the browser.
 * @param  {Object} initialState
 */
function initApolloClient (initialState) {
  // Make sure to create a new client for every server-side request so that data
  // isn't shared between connections (which would be bad)
  if (typeof window === 'undefined') {
    return createApolloClient(initialState)
  }

  // Reuse client on the client-side
  if (!apolloClient) {
    apolloClient = createApolloClient(initialState)
  }

  return apolloClient
}

/**
 * Creates and configures the ApolloClient
 * @param  {Object} [initialState={}]
 */
function createApolloClient (initialState = {}) {
  // Check out https://github.com/zeit/next.js/pull/4611 if you want to use the AWSAppSyncClient
  return new ApolloClient({
    ssrMode: typeof window === 'undefined', // Disables forceFetch on the server (so queries are only run once)
    link: new HttpLink({
      uri: 'https://api.graph.cool/simple/v1/cixmkt2ul01q00122mksg82pn', // Server URL (must be absolute)
      credentials: 'same-origin', // Additional fetch() options like `credentials` or `headers`
      fetch
    }),
    cache: new InMemoryCache().restore(initialState)
  })
}