Beacon scores in post meta

functions.php

function carbon_rating_meta() {
    add_meta_box(
        'custom_post_metabox',
        'Carbon rating',
        function () {
            global $post;

            if ($post->post_status != 'publish') {
                echo 'Publish content first';
            }
            $link = urlencode(get_permalink($post->ID));
            $rating = get_post_meta($post->ID, 'rating', 1);
            $size = get_post_meta($post->ID, 'size', 1);
            $co2 = get_post_meta($post->ID, 'co2', 1);

            if ($size == null) {
                echo 'Click button to get initial score';
            }

            if ($size) {
            // get current rating
            ob_start(); ?>
            <table>
                <tr>
                    <th>Rating:</th>
                    <td><?= ucwords($rating); ?></td>
                </tr>
                <tr>
                    <th>Size:</th>
                    <td><?= $size; ?></td>
                </tr>
                <tr>
                    <th>Emissions: </th>
                    <td><?= $co2; ?></td>
                </tr>
            </table>
            <?php
            }
            echo ob_get_clean();
            ob_start();?>
            <p id="carbonratingoutput"></p>
            <p><button id="carbonrating" data-id="<?= $post->ID ?>" data-url="<?= $link; ?>" class="button button-primary button-large">Update scores</button></p>
            <script>
                jQuery('#carbonrating').click((e) => {
                    e.preventDefault();
                    jQuery('#carbonrating').attr('disabled', 'disabled');
                    jQuery.get("https://digitalbeacon.co/badge?renew=true&url=" + jQuery('#carbonrating').data('url'), (data) => {
                        console.log(data);
                        jQuery.post({
                            url: window.ajaxurl,
                            data: {
                                action: 'carbon_rating',
                                post_id: jQuery('#carbonrating').data('id'),
                                scores: data
                            },
                            success: () => {
                                jQuery('#carbonrating').removeAttr('disabled');
                                location.reload();
                            }
                        })
                    }).fail(() => {
                        jQuery('#carbonratingoutput').text('Page cannot be tested. Please try again later');
                    });
                })
            </script>
            <?php
            echo ob_get_clean();
        },
        ['post', 'page'],
        'side',
        'core'
    );
}

add_action('add_meta_boxes', 'carbon_rating_meta');

add_action('wp_ajax_carbon_rating', function() {
    $data = $_POST['scores'];
    $id = $_POST['post_id'];

    update_post_meta($id, 'rating', $data['rating']);
    update_post_meta($id, 'size', $data['size']);
    update_post_meta($id, 'co2', $data['co2']);

    echo 'updated';

    exit();
});

add_shortcode('carbon_rating', function ($atts) {
    $rating = get_post_meta($post->ID, 'rating', 1);
    $size = get_post_meta($post->ID, 'size', 1);
    $co2 = get_post_meta($post->ID, 'co2', 1);
    $url = get_post_meta($post->ID, 'beacon_url', 1);

    if ($size == null) {
        echo '';
        exit();
    }


    ob_start(); ?>
    <div id="dbb">
        <a href="<?= $url; ?>" class="dbb__link dbb__el" target="_blank">
                <div class="dbb">
                    <div class="dbb__logo">Beac<span class="dbb__logo__o <?= $rating; ?>">o</span>n</div>
                    <div class="dbb__stats"><?= $size; ?> | <?= $co2; ?></div>
                </div>
            </a></div>
    <?php
    echo ob_get_clean();
});