import { Injectable, NestMiddleware } from '@nestjs/common';
import { NextFunction, Request, Response } from 'express';
import { SessionData } from 'express-session';
import { format } from 'util';

@Injectable()
export class FlashMiddleware implements NestMiddleware {
  private _flash(
    session: SessionData,
    type: string,
    ...msg: any[]
  ): Record<string, any> {
    const msgs = (session.flash = session.flash || {});

    if (type && msg?.length) {
      let result: string;

      if (Array.isArray(msg[0])) {
        msg[0].forEach((val) => {
          (msgs[type] = msgs[type] || []).push(val);
        });

        return msgs;
      } else {
        result = msg.length > 1 ? format(...msg) : msg[0];
      }

      return (msgs[type] = msgs[type] || []).push(result);
    } else if (type) {
      const arr = msgs[type];
      delete msgs[type];
      return arr || [];
    } else {
      session.flash = {};
      return msgs;
    }
  }

  use(req: Request, res: Response, next: NextFunction) {
    if (req.flash) {
      return next();
    }

    req.flash = this._flash.bind(this, req.session);
    next();
  }
}