fb_video_image_auto_import.php

<?php
// Save post Hook
  function grab_fb_video_image( $post_id, $post) {

    if ( wp_is_post_revision( $post_id ) )
      return;

    $image = get_field('featured_image');

    if ($image || is_null($image)) { // No need to continue - image is already there, or no field exists
      return;
    }

    preg_match('/videos%2F([^"]+)%2F/', $post->post_content, $match);

    if (!isset($match[1])) {
      return;
    }

    $videoId = $match[1];

    $fb = new Facebook\Facebook([
      'app_id' => FB_APP_ID,
      'app_secret' => FB_APP_SECRET,
      'default_graph_version' => 'v2.7',
    ]);

    // Temporary access token for now 60 days - it's barebones access -
    // PUBLIC data only - so not worried about including this in repository
    $userAccessToken = 'EAAJfdgJVlNEBAMHpqsi6HAFtPpWUQFzlZCPnRd934fuz1ZBhBZB7wdgowF7gdOY9aoyDYuxZC4KaSlq23JqKBKOgE9zB3sRVqzMEu5YNgDRofZBzFvCtuAmow2lH3sqLCm55aT3K3YKC8zd7UoKZAw';

    $response = $fb->get("/$videoId/thumbnails", $userAccessToken);

    $videoJSON = $response->getBody();

    // @TODO - check if is not JSON
    if (!$videoJSON) {
      return;
    }

    $videoData = json_decode($videoJSON);

    if (!isset($videoData->data[0])) {
      return;
    }

    $tmp = download_url( $videoData->data[0]->uri );

    $file_array = array(
      'name' => basename( strtok($videoData->data[0]->uri, '?') ),
      'tmp_name' => $tmp
    );

    if ( is_wp_error( $tmp ) ) {
      @unlink( $file_array[ 'tmp_name' ] );
      return $tmp;
    }

    $free_post_id = 0; // 0 not to attach it to any post

    $id = media_handle_sideload( $file_array, $free_post_id );

    if ( is_wp_error( $id ) ) {
      @unlink( $file_array['tmp_name'] );
      return $id;
    }

    $absoluteFileURI = get_attached_file($id);
    $image = wp_get_image_editor( $absoluteFileURI );

    if ( ! is_wp_error( $image ) ) {

      $current_size = $image->get_size();
      $smallest_size = min($current_size);

      //$image->resize( $smallest_size, $smallest_size , true);
      $image->crop(0, 0, $smallest_size, $smallest_size);

      $filename = $image->generate_filename();

      $image->save( $filename );

      // Attachment Creation - Needed to add this to Media Uploads Library
      $filetype = wp_check_filetype( basename( $filename), null );

      $wp_upload_dir = wp_upload_dir();

      $attachment = array(
        'guid'           => $wp_upload_dir['url'] . '/' . basename( $filename ),
        'post_mime_type' => $filetype['type'],
        'post_title'     => get_the_title($post_id),
        'post_content'   => '',
        'post_status'    => 'inherit'
      );

      $uploadDir = $wp_upload_dir['path'] . '/' . basename( $filename );

      $attach_id = wp_insert_attachment( $attachment, $uploadDir, $post_id );

      $attach_data = wp_generate_attachment_metadata( $attach_id, $filename );
      wp_update_attachment_metadata( $attach_id, $attach_data );
      // End of attachment creation

      // Finally add this to ACF field
      update_field('featured_image', $attach_id, $post_id);

    }
  }
  add_action( 'save_post', 'grab_fb_video_image', 10, 3 );
  
  ?>