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Previews in Headless WordPress

NOTE: This is prerelease software. As we work towards our first release, we will 💯 introduce breaking changes.

In this guide, we'll walk through how to configure a Next.js site for previews.

We're going to use Next with TypeScript for this example.

npx create-next-app previews
cd previews
rm -r ./pages/*
npm i @wpengine/headless @apollo/client graphql
npm i typescript @types/react @types/react-dom @types/node -D

TL;DR Checkout the example project to see how it works.

WPE Headless Plugin

In order to enable previews in WordPress, you'll first need to install the wpe-headless plugin. You also need to install WPGraphQL.

The plugin enables an OAuth flow for users to authenticate with WordPress and receive an access token which is used for subsequent API calls (i.e. GQL/REST).

In addition, the plugin will rewrite URLs in WordPress so that when a user clicks view/preview on a post, they will be taken to the frontend rather than WP.

Plugin Settings

Go to Settings->Headless to view the plugin's settings page:

Headless Plugin Menu

There are 2 settings that assist in previews. The first setting is the location of your frontend. You'll need to enter a Front-end site URL, which will be http://localhost:3000 for this example.

The second one is read-only. It gives you an API secret key that you need to use on your backend for your frontend.

Headless Plugin Auth Settings

Headless Framework (@wpengine/headless)

The @wpengine/headless package provides helpers to get previews working in a React application.

Install the npm package via:

npm i @wpengine/headless

The package contains an auth handler to get an access token for a user when trying to view a preview/draft post as well as React hooks to pull post(s).

Authorization Flow

In order to submit secure requests to WordPress, we need to be able to verify that a user has access to the content that is being requested. The plugin exposes routes that allow us to create access codes and exchange them for access tokens.

The flow looks like this:

  • User makes a request to a secure route (i.e. draft post)
  • User is redirected to WordPress to login
  • WordPress redirects back to frontend with a temporary code
  • The frontend server exchanges the code for an access token
  • The access token is stored in a cookie
  • The user is finally redirected back to the original URL and uses the access token in the cookie to make the authenticated request

The framework provides a Node.js auth handler to do the exchange for you.

Auth Hander

In order to support the exchange of the access code for an access token, the framework provides a Node authorization handler:

import { authorizeHandler } from '@wpengine/headless';

authorizeHandler accepts a Node request (IncomingMessage) and response (ServerResponse) which are compatible with ExpressJS, Next APIs, etc.

In order to enable the handler in Next, create a new API route:

/pages/api/authorize.ts

import { authorizeHandler } from '@wpengine/headless';

export default authorizeHandler;

Next Integration

The framework provides a provider and hooks that assist in routing and server side rendering.

HeadlessProvider

The provider is the glue that allows the framework to communicate with WordPress. To set it up, create /pages/_app.tsx.

import React from 'react';
import { AppContext, AppInitialProps } from 'next/app';
import { HeadlessProvider } from '@wpengine/headless';

export default function App({
  Component,
  pageProps,
}: AppContext & AppInitialProps) {
  return (
    <HeadlessProvider pageProps={pageProps}>
      <Component {...pageProps} />
    </HeadlessProvider>
  );
}

Routes and Hooks

For this example, we're only going to need one page to handle all of our routes /pages/[[...page]].tsx. This is a catch-all route in Next. We'll use hooks provided by the framework to load the right content for each URL.

import React from 'react';
import {
  useUriInfo,
  getNextServerSideProps,
} from '@wpengine/headless/next';
import { GetServerSidePropsContext } from 'next';
import Posts from '../lib/components/Posts';
import Post from '../lib/components/Post';

export default function Page() {
  const pageInfo = useUriInfo();

  if (!pageInfo) {
    return <></>;
  }

  if (pageInfo.isPostsPage) {
    return <Posts />;
  }

  return <Post />;
}

export function getServerSideProps(context: GetServerSidePropsContext) {
  return getNextServerSideProps(context);
}

useUriInfo gets the URL from the Next Router and queries WP to get information about the route. If the route has a list of posts, we'll show one component. If it has a single post, we'll show another. Let's add those components to /lib/components.

getNextServerSideProps is used to allow for Server Side Rendering. It knows how to get URL information on the server so that we can query WP and pull the right pageInfo on the initial request. This is critical for SEO. We want to return the rendered page on the first request so that search engines can index our content.

/lib/components/Post.tsx

import React from 'react';
import { usePost } from '@wpengine/headless/next';

export default function Post() {
  const post = usePost();

  return (
    <div>
      {post && (
        <div>
          <div>
            <h5>{post.title}</h5>
            <p
              dangerouslySetInnerHTML={{
                __html: post.content ?? '',
              }}
            />
          </div>
        </div>
      )}
    </div>
  );
}

/lib/components/Posts.tsx

import React from 'react';
import Link from 'next/link';
import { usePosts } from '@wpengine/headless/react';

export default function Posts() {
  const posts = usePosts();

  return (
    <div>
      {posts &&
        posts.map((post) => (
          <div key={post.id} id={`post-${post.id}`}>
            <div>
              <Link href={post.uri}>
                <h5>
                  <a href={post.uri}>{post.title}</a>
                </h5>
              </Link>
              <p
                dangerouslySetInnerHTML={{
                  __html: post.excerpt ?? '',
                }}
              />
            </div>
          </div>
        ))}
    </div>
  );
}

Configuration

We need to let the frontend know about our WordPress instance. The framework expects a few environment variables with this information. Create a file in the root of the project /.env.local.

# Base URL for WordPress
NEXT_PUBLIC_WORDPRESS_URL=http://yourwpsite.com

# Plugin secret found in WordPress Settings->Headless
WP_HEADLESS_SECRET=YOUR_PLUGIN_SECRET

# Location of the auth handler endpoint
NEXT_PUBLIC_AUTHORIZATION_URL=/api/authorize

Try it out!

You can run the project via:

npm run dev

The server will start on port 3000 by default: http://localhost:3000

You should see a list of posts on the home page and be able to view a single post.

For previews, go to WP and create a new post, but don't publish it. Click preview, and you'll be sent to the frontend through the authorization flow.

NOTE: If you open the preview link in a private window, you'll be prompted to login to WP before being redirected back to the frontend.