Add category name to post

you could consider to use post_class() https://codex.www.ads-software.com/Function_Reference/post_class which would, in your case, output class="category-beans" plus a lot of other categories;

or you could build on get_the_category() https://codex.www.ads-software.com/Function_Reference/get_the_category to make your own output.

using just the category slug might lead to problems, if the slug by chance equals one of the existing css classes.

I see waht you mean I’ve found this which adds the categories id, I prsume that would be better?

function category_id_class($classes) {
     global $post;
          foreach((get_the_category($post->ID)) as $category)
               $classes [] = 'cat-' . $category->cat_ID . '-id';

     return $classes;
}

add_filter('post_class', 'category_id_class');
add_filter('body_class', 'category_id_class');

that code is a filter function for post_class() and body_class() to additionally output css classes with category ids.

using post_class() in your div would automatically give you post category specific css classes with a prefix and the category slug;

<div id="post-wraper" <?php post_class(); ?>>

would among other css classes also output .category-beans

Yea it did that and then some, which is quite anoying as I only need the one class.

Also it would be handy if it posted a link to the archive of that particular category

Also it would be handy if it posted a link to the archive of that particular category

check https://codex.www.ads-software.com/Function_Reference/the_category

Thanks will do.