Based on this post – Programmatically adding images to media library I’m trying to add image from my theme to media library, once, after theme activation. My code:

add_action( 'after_setup_theme', 'image_on_theme_install' );

function image_on_theme_install() {
     
    $image_url = get_template_directory_uri().'/media/ml-special-hero-placeholder.jpg';
    $upload_dir = wp_upload_dir();
    $image_data = file_get_contents( $image_url );
    $filename = basename( $image_url );

    if ( wp_mkdir_p( $upload_dir['path'] ) ) {
    $file = $upload_dir['path'] . "https://wordpress.stackexchange.com/" . $filename;
    }
    else {
    $file = $upload_dir['basedir'] . "https://wordpress.stackexchange.com/" . $filename;
    }

    file_put_contents( $file, $image_data );

    $wp_filetype = wp_check_filetype( $filename, null );

    $attachment = array(
    'post_mime_type' => $wp_filetype['type'],
    'post_title' => sanitize_file_name( $filename ),
    'post_content' => '',
    'post_status' => 'inherit'
    );

    $attach_id = wp_insert_attachment( $attachment, $file );
    require_once( ABSPATH . 'wp-admin/includes/image.php' );
    $attach_data = wp_generate_attachment_metadata( $attach_id, $file );
    wp_update_attachment_metadata( $attach_id, $attach_data );

}

Problem: image is added multiple times, in loop, not only once after theme activation. How to do that properly?