swaf/src/components/RedirectBackComponent.ts

import ApplicationComponent from "../ApplicationComponent";
import {Request, Router} from "express";
import {ServerError} from "../HttpError";
import onFinished from "on-finished";

export default class RedirectBackComponent extends ApplicationComponent {
    public static getPreviousURL(req: Request, defaultUrl?: string): string | undefined {
        return req.session?.previousUrl || defaultUrl;
    }

    public async handle(router: Router): Promise<void> {
        router.use((req, res, next) => {
            res.redirectBack = (defaultUrl?: string): void => {
                const previousUrl = RedirectBackComponent.getPreviousURL(req, defaultUrl);
                if (!previousUrl) throw new ServerError(`Couldn't redirect you back.`);
                res.redirect(previousUrl);
            };

            res.locals.getPreviousURL = (defaultUrl?: string) => {
                return RedirectBackComponent.getPreviousURL(req, defaultUrl);
            };

            onFinished(res, (err) => {
                const session = req.session;
                if (session) {
                    const contentType = res.getHeader('content-type');
                    if (!err && res.statusCode === 200 && (
                        contentType && typeof contentType !== 'number' && contentType.indexOf('text/html') >= 0
                    )) {
                        session.previousUrl = req.originalUrl;
                        req.log.debug('Prev url set to', session.previousUrl);
                        session.save((err) => {
                            if (err) {
                                req.log.error(err, 'Error while saving session');
                            }
                        });
                    }
                }
            });

            next();
        });
    }
}