function bp_members_invitations_get_registration_welcome_message() {
	$message = '';
	if ( ! bp_get_members_invitations_allowed() ) {
		return $message;
	}

	$invite = bp_get_members_invitation_from_request();
	if ( ! $invite->id || ! $invite->invitee_email ) {
		return $message;
	}

	// Check if the user is already a site member.
	$maybe_user = get_user_by( 'email', $invite->invitee_email );

	// This user is already a member
	if ( $maybe_user ) {
		$message = sprintf(
			/* translators: %s: The log in link `<a href="login_url">log in</a>` */
			esc_html__( 'Welcome! You are already a member of this site. Please %s to continue.', 'buddypress' ),
			sprintf(
				'<a href="%1$s">%2$s</a>',
				esc_url( wp_login_url( bp_get_root_domain() ) ),
				esc_html__( 'log in', 'buddypress' )
			)
		);

	// This user can register!
	} else {

		// Fetch the display names of all inviters to personalize the welcome message.
		$args = array(
			'invitee_email' => $invite->invitee_email,
			'invite_sent'   => 'sent',
		);

		$all_invites = bp_members_invitations_get_invites( $args );
		$inviters    = array();

		foreach ( $all_invites as $inv ) {
			$inviters[] = bp_core_get_user_displayname( $inv->inviter_id );
		}

		if ( ! empty( $inviters ) ) {
			$message = sprintf(
				/* translators: %s: The comma separated list of inviters display names */
				_n( 'Welcome! You&#8217;ve been invited to join the site by the following user: %s.', 'Welcome! You&#8217;ve been invited to join the site by the following users: %s.', count( $inviters ), 'buddypress' ),
				implode( ', ', $inviters )
			);
		} else {
			$message = __( 'Welcome! You&#8217;ve been invited to join the site. ', 'buddypress' );
		}
	}

	return $message;
}