Wordpress: How to automatically attache youtube/vimeo thumbnail as a post feature image from a post meta key

functions.php

<?php

// https://github.com/WebDevStudios/Automatic-Featured-Images-from-Videos/blob/1.2.0/automatic-featured-images-from-videos.php
/**
 * If a YouTube or Vimeo video is added in the post content, grab its thumbnail and set it as the featured image.
 *
 * @since 1.0.0
 *
 * @param int    $post_id             ID of the post being saved.
 * @param string $video_thumbnail_url URL of the image thumbnail.
 * @param string $video_id            Video ID from embed.
 */
function wds_set_video_thumbnail_as_featured_image( $post_id, $video_thumbnail_url, $video_id = '' ) {

    // Bail if no valid video thumbnail URL.
    if ( ! $video_thumbnail_url || is_wp_error( $video_thumbnail_url ) ) {
        return;
    }

    $post_title = sanitize_title( preg_replace( '/[^a-zA-Z0-9\s]/', '-', get_the_title() ) ) . '-' . $video_id;

    global $wpdb;

    $stmt = "SELECT ID FROM {$wpdb->posts}";
    $stmt .= $wpdb->prepare(
        ' WHERE post_type = %s AND guid LIKE %s',
        'attachment',
        '%' . $wpdb->esc_like( $video_id ) . '%'
    );
    $attachment = $wpdb->get_col( $stmt );
    if ( !empty( $attachment[0] ) ) {
        $attachment_id = $attachment[0];
    } else {
        // Try to sideload the image.
        $attachment_id = wds_ms_media_sideload_image_with_new_filename( $video_thumbnail_url, $post_id, $post_title, $video_id );
    }

    // Bail if unable to sideload (happens if the URL or post ID is invalid, or if the URL 404s).
    if ( is_wp_error( $attachment_id ) ) {
        return;
    }

    // Woot! We got an image, so set it as the post thumbnail.
    set_post_thumbnail( $post_id, $attachment_id );
}

// https://github.com/WebDevStudios/Automatic-Featured-Images-from-Videos/blob/1.2.0/automatic-featured-images-from-videos.php
/**
 * Handle the upload of a new image.
 *
 * @since 1.0.0
 *
 * @param string      $url      URL to sideload.
 * @param int         $post_id  Post ID to attach to.
 * @param string|null $filename Filename to use.
 * @param string      $video_id Video ID.
 *
 * @return mixed
 */
function wds_ms_media_sideload_image_with_new_filename( $url, $post_id, $filename = null, $video_id = null ) {

    if ( ! $url || ! $post_id ) {
        return new WP_Error( 'missing', esc_html__( 'Need a valid URL and post ID...', 'automatic-featured-images-from-videos' ) );
    }

    require_once( ABSPATH . 'wp-admin/includes/file.php' );

    // Download file to temp location, returns full server path to temp file, ex; /home/user/public_html/mysite/wp-content/26192277_640.tmp.
    $tmp = download_url( $url );

    // If error storing temporarily, unlink.
    if ( is_wp_error( $tmp ) ) {
        // And output wp_error.
        return $tmp;
    }

    // Fix file filename for query strings.
    preg_match( '/[^\?]+\.(jpg|JPG|jpe|JPE|jpeg|JPEG|gif|GIF|png|PNG)/', $url, $matches );
    // Extract filename from url for title.
    $url_filename = basename( $matches[0] );
    // Determine file type (ext and mime/type).
    $url_type = wp_check_filetype( $url_filename );

    // Override filename if given, reconstruct server path.
    if ( ! empty( $filename ) ) {
        $filename = sanitize_file_name( $filename );
        // Extract path parts.
        $tmppath = pathinfo( $tmp );
        // Build new path.
        $new = $tmppath['dirname'] . '/' . $filename . '.' . $tmppath['extension'];
        // Renames temp file on server.
        rename( $tmp, $new );
        // Push new filename (in path) to be used in file array later.
        $tmp = $new;
    }

    /* Assemble file data (should be built like $_FILES since wp_handle_sideload() will be using). */

    // Full server path to temp file.
    $file_array['tmp_name'] = $tmp;

    if ( ! empty( $filename ) ) {
        // User given filename for title, add original URL extension.
        $file_array['name'] = $filename . '.' . $url_type['ext'];
    } else {
        // Just use original URL filename.
        $file_array['name'] = $url_filename;
    }

    $post_data = [
        // Just use the original filename (no extension).
        'post_title'  => get_the_title( $post_id ),
        // Make sure gets tied to parent.
        'post_parent' => $post_id,
    ];

    // Required libraries for media_handle_sideload.
    require_once( ABSPATH . 'wp-admin/includes/file.php' );
    require_once( ABSPATH . 'wp-admin/includes/media.php' );
    require_once( ABSPATH . 'wp-admin/includes/image.php' );

    // Do the validation and storage stuff.
    // $post_data can override the items saved to wp_posts table, like post_mime_type, guid, post_parent, post_title, post_content, post_status.
    $att_id = media_handle_sideload( $file_array, $post_id, null, $post_data );

    // If error storing permanently, unlink.
    if ( is_wp_error( $att_id ) ) {
        // Clean up.
        @unlink( $file_array['tmp_name'] );

        // And output wp_error.
        return $att_id;
    }

    return $att_id;
}


// https://github.com/WebDevStudios/Automatic-Featured-Images-from-Videos/blob/1.2.0/automatic-featured-images-from-videos.php
/**
 * Check if the content contains a vimeo url.
 *
 * Props to @rzen for lending his massive brain smarts to help with the regex.
 *
 * @author Gary Kovar
 *
 * @param $content
 *
 * @return string The value of the vimeo id.
 *
 */
function wds_check_for_vimeo( $content ) {
	if ( preg_match( '#\/\/(.+\.)?(vimeo\.com)\/(\d*)#', $content, $vimeo_matches ) ) {
		return $vimeo_matches[3];
	}

	return false;
}

// https://github.com/WebDevStudios/Automatic-Featured-Images-from-Videos/blob/1.2.0/automatic-featured-images-from-videos.php
/**
 * Get the image thumbnail and the video url from a vimeo id.
 *
 * @author Gary Kovar
 *
 * @since 1.0.5
 *
 * @param string $vimeo_id Vimeo video ID.
 * @return array Video information.
 */
function wds_get_vimeo_details( $vimeo_id ) {
	$video = [];

	// @todo Get remote checking matching with wds_get_youtube_details.
	$vimeo_data = wp_remote_get( 'https://www.vimeo.com/api/v2/video/' . intval( $vimeo_id ) . '.json' );
	if ( 200 === wp_remote_retrieve_response_code( $vimeo_data ) ) {
		$response                     = json_decode( $vimeo_data['body'] );

		$large = isset( $response[0]->thumbnail_large ) ? $response[0]->thumbnail_large : '';
		if ( $large ) {
			$larger_test = explode( '_', $large );
			$test_result = wp_remote_head(
				$larger_test[0]
			);
			if ( 200 === wp_remote_retrieve_response_code( $test_result ) ) {
				$large = $larger_test[0];
			}
		}

		// For the moment, we will force jpg since WebP is still iffy.
		$video['video_thumbnail_url'] = isset( $large ) ? $large . '.jpg' : false;
		$video['video_url']           = $response[0]->url;
		$video['video_embed_url']     = 'https://player.vimeo.com/video/' . $vimeo_id;
	}

	return $video;
}

function set_featured_image_from_post_meta($post_id, $post, $update) {	
    $post_type = 'lecture'; // the custom post type
    $meta_key = 'preview_vimeo_oembed'; // the custom meta key

    if ($post_type !== get_post_type($post_id) || has_post_thumbnail($post_id)) {
        return;
    }
    $video_url = get_post_meta($post_id, $meta_key, true);
    if(!$video_url) {
        return;
    }
    $vimeo_id = wds_check_for_vimeo($video_url);
    if (!$vimeo_id) {
        return;
    }
    $vimeo_details  = wds_get_vimeo_details($vimeo_id);
    if (empty($vimeo_details)) {
        return;
    }
    $video_thumbnail_url = $vimeo_details['video_thumbnail_url'];

    wds_set_video_thumbnail_as_featured_image($post_id, $video_thumbnail_url, $vimeo_id);
}
add_action('wp_after_insert_post', 'set_featured_image_from_post_meta', 10, 4);