Needing To Attach Unique Post ID To Uploaded Image and Add to Media Library

Here is a snippet of code from the EXIF plugin:

//render shortcode
		function shortcode($atts, $content = null) {
			global $post;
			$post_options = get_post_meta($post->ID, '_use_exif', true);
			if ($post_options)
				$post_options = $post_options;
			else
				$post_options = "all";

			extract(shortcode_atts(array(
				'show' => $post_options,
				'id' => '',
			), $atts));

			$images = get_children(array(
				'post_parent' => $post->ID,
				'post_type' => 'attachment',
				'numberposts' => 1,
				'post_mime_type' => 'image',
				'orderby' => 'ID',
				'order' => 'ASC'
				));
			if ($images) {
				foreach ($images as $image) {
					$imageID = $image->ID;
				}
			}

			if ($id == '')
				$imgID = $imageID;
			else
				$imgID = $id;

			$display = $show;

			return $this->display_exif($display,$imgID);
		}

		//auto insert
		function auto_insert($content) {
			$options = $this->get_options();
			if (isset($options['auto_insert']) && (!is_page()))
				return $content . $this->display_exif();
			else
				return $content;
		}

So here's my updated code that seems to be working, but then the thumbnail isn't showing up in media library and then the link is created as a a href to the image instead of the image itself showing when viewing the attachment page:

//Add upload field images to media library
add_action("gform_after_submission", "set_post_content", 10, 2);
	function set_post_content($entry, $form){

	    if($_FILES['input_5']) {

			require_once(ABSPATH . 'wp-admin/includes/file.php');

			require_once(ABSPATH . 'wp-admin/includes/image.php');

			require_once(ABSPATH . 'wp-admin/includes/media.php');

			$filename = $entry[5];

			$attachment = array(
				'guid' => $wp_upload_dir['url'] . '/' . basename( $filename ),
				'post_mime_type' => $wp_filetype['type'],
				'post_title' => preg_replace('/\.[^.]+$/', '', basename($filename)),
			);

			$attach_id = wp_insert_attachment($attachment, $filename);;

			$attach_data = wp_generate_attachment_metadata($attach_id, $filename);

			wp_update_attachment_metadata($attach_id, $attach_data);
		}
}