[site-reviews] Translate categories

/**
 * Get the languages of the website
 * @return array
 */
function glsr_get_pll_languages () {
    if (!function_exists('pll_languages_list') || !function_exists('pll_default_language')) {
        return [];
    }
    $slugs = pll_languages_list();
    $names = pll_languages_list(['fields' => 'name']);
    $languages = array_combine($slugs, $names);
    unset($languages[pll_default_language()]);
    return $languages;
}

/**
 * Add a language field to new categories
 */
function glsr_add_category_fields () {
    $languages = glsr_get_pll_languages();
    $html = '' .
        '<div class="form-field">' .
            '<label for="%1$s-slug">%2$s</label>' .
            '<input type="text" name="%1$s" id="%1$s-slug" />' .
        '</div>';
    foreach ($languages as $slug => $label) {
        printf($html, $slug, $label);
    }
}

/**
 * Add a language field to existing categories
 * @param \WP_Term $term
 */
function glsr_edit_category_fields ($term) {
    $languages = glsr_get_pll_languages();
    $html = '' .
        '<tr class="form-field">' .
            '<th><label for="%1$s-slug">%2$s</label></th>' .
            '<td><input type="text" name="%1$s" id="%1$s-slug" value="%3$s" /></td>' .
        '</tr>';
    foreach ($languages as $slug => $label) {
        $value = esc_attr(get_term_meta($term->term_id, $slug, true));
        printf($html, $slug, $label, $value);
    }
}

/**
 * Save the language field when creating or editing a category
 * @param int $termId
 */
function glsr_save_category_fields ($termId) {
    $languages = glsr_get_pll_languages();
    foreach ($languages as $slug => $label) {
        $value = sanitize_text_field(filter_input(INPUT_POST, $slug));
        update_term_meta($termId, $slug, $value);
    }
}

/**
 * Translate the category on the frontend
 * @param array $terms
 * @param array $taxonomies
 * @param array $args
 * @return array
 */
function glsr_translate_category ($terms, $taxonomies, $args) {
    if ($taxonomies !== ['site-review-category'] || !function_exists('pll_current_language')) {
        return $terms;
    }
    $lang = pll_current_language();
    if ($args['fields'] === 'id=>name') {
        foreach ($terms as $termId => $label) {
            $label = get_term_meta($termId, $lang, true);
            if (!empty($label)) {
                $terms[$termId] = $label;
            }
        }
    }
    elseif ($args['fields'] === 'all') {
        foreach ($terms as &$term) {
            $label = get_term_meta($term->term_id, $lang, true);
            if (!empty($label)) {
                $term->name = $label;
            }
        }
    }
    return $terms;
}

add_action('site-review-category_add_form_fields', 'glsr_add_category_fields');
add_action('site-review-category_edit_form_fields', 'glsr_edit_category_fields');
add_action('created_site-review-category', 'glsr_save_category_fields');
add_action('edited_site-review-category', 'glsr_save_category_fields');
add_filter('get_terms', 'glsr_translate_category', 10, 3);