Form_Upload_Manager::upload_file( string $file_id, awsmug\Torro_Forms\DB_Objects\Submissions\Submission $submission, awsmug\Torro_Forms\DB_Objects\Forms\Form $form, int $element_id, string $field = '_main', array $allowed_mimes = null, int $allowed_filesize = null )

	public function upload_file( $file_id, $submission, $form, $element_id, $field = '_main', $allowed_mimes = null, $allowed_filesize = null ) {
		if ( ! isset( $_FILES[ $file_id ] ) ) {
			return new WP_Error( 'missing_file', __( 'No file was provided to upload.', 'torro-forms' ) );
		}

		$prefix = $this->get_prefix();

		if ( ! $field ) {
			$field = '_main';
		}

		$attachment_data = array(
			'post_title' => sprintf( __( 'Form upload for submission #%1$s (form “%2$s”)', 'torro-forms' ), $submission->id, $form->title ),
			'meta_input' => array(
				$prefix . 'parent_submission_id' => $submission->id,
				$prefix . 'parent_form_id'       => $form->id,
				$prefix . 'parent_element_id'    => $element->id,
				$prefix . 'parent_element_field' => $field,
			),
		);

		$post_id = 0;
		if ( $this->should_set_parent_form( $form->id ) ) {
			$post_id = $form->id;
		}

		$overrides = array(
			'mimes'     => $allowed_mimes,
			'test_form'	=> false,
			'test_type'	=> true,
			'test_size'	=> true,
		);

		if ( $allowed_filesize ) {
			$filesize = isset( $_FILES[ $file_id ]['size'] ) ? $_FILES[ $file_id ]['size'] : filesize( $_FILES[ $file_id ]['tmp_name'] );
			if ( (int) $filesize > (int) $allowed_filesize ) {
				return new WP_Error( 'upload_error', __( 'The file exceeds the maximum allowed size.', 'torro-forms' ) );
			}
		}

		if ( ! function_exists( 'wp_handle_upload' ) ) {
			require_once ABSPATH . 'wp-admin/includes/file.php';
		}
		if ( ! function_exists( 'wp_read_image_metadata' ) ) {
			require_once ABSPATH . 'wp-admin/includes/image.php';
		}
		if ( ! function_exists( 'media_handle_upload' ) ) {
			require_once ABSPATH . 'wp-admin/includes/media.php';
		}

		$added_filter = false;
		if ( ! $this->should_generate_image_sizes( $form->id ) ) {
			$added_filter = true;
			add_filter( 'intermediate_image_sizes_advanced', '__return_empty_array', 9999 );
		}

		$attachment_id = media_handle_upload( $file_id, $post_id, $attachment_data, $overrides );

		if ( $added_filter ) {
			remove_filter( 'intermediate_image_sizes_advanced', '__return_empty_array', 9999 );
		}

		if ( is_wp_error( $attachment_id ) ) {
			// The following line has no textdomain on purpose as it's a WP core message.
			if ( $allowed_mimes && 'upload_error' === $attachment_id->get_error_code() && __( 'Sorry, this file type is not permitted for security reasons.' ) === $attachment_id->get_error_message() ) {
				return new WP_Error( 'upload_error', __( 'The file type is not permitted.', 'torro-forms' ) );
			}

			return $attachment_id;
		}

		if ( ! $attachment_id ) {
			return new WP_Error( 'upload_error', __( 'The file could not be registered with the database.', 'torro-forms' ) );
		}

		$attachment_id = (int) $attachment_id;

		// Set the default attachment taxonomy term for form uploads.
		$taxonomy_slug = $this->taxonomies()->get_attachment_taxonomy_slug();
		if ( ! empty( $taxonomy_slug ) ) {
			$taxonomy_term_id = $this->taxonomies()->get_attachment_taxonomy_term_id();
			if ( ! empty( $taxonomy_term_id ) ) {
				wp_set_post_terms( $attachment_id, array( $taxonomy_term_id ), $taxonomy_slug );
			}
		}

		return $attachment_id;
	}