Is there an easy way to separate themes on network?

Question

Assume we have a multisite network. All sites in the network are separated into groups by some option value. What I want to do is to separate network available themes to be available to specific groups.

For instance, I have A-Z themes installed. I want to activate A-K themes to group 1, L-O themes to group 2 and P-Z themes to group 3.

Is there an easy way to do it?

Answer 1

You'd have to make you site categories slug match your theme categories folder names.

Here's how to filter themes: Hide a theme on list of themes in wp-admin without editing core files

And then, supposing a site has the category a-p and the themes are stored in themes/a-p/, this will filter them out:

add_filter( 'all_themes', 'remove_themes_ms_wpse_117537' );

function remove_themes_ms_wpse_117537( $themes )
{
    if( 'site-themes-network' != get_current_screen()->id )
        return $themes;

    $site_cat = get_blog_option( absint( $_GET['id'] ), 'site_category' );
    if( $site_cat )
    {
        # Unset themes not in the folder /themes/$site_cat/
        foreach( $themes as $key => $theme )
        {
            if( strpos( $key, "$site_cat/" ) === false )
                unset($themes[$key]);
        }
    }
    return $themes;
}