import { Injectable, NestMiddleware } from "@nestjs/common";
import { NextFunction, Request, Response } from "express";
import { Xdb } from "./xml-data-bridge.constants";

/**
 * Middleware for parsing XML data from requests.
 */
@Injectable()
export class XmlDataBridgeMiddleware implements NestMiddleware {
  private readonly parser = Xdb.getXmlParser();

  /**
   * Parses XML data from the request and modifies the request body.
   * @param req - The request object.
   * @param res - The response object.
   * @param next - The next function to call.
   */
  async use(req: Request, res: Response, next: NextFunction) {
    if (req.headers["content-type"] === "application/xml") {
      req.body = await this.parseXMLFromRequest(req);
      req.body = Xdb.parseXmlBody(req.body);
    }
    next();
  }

  /**
   * Parses XML data from the request.
   * @param req - The request object.
   * @returns A promise that resolves to the parsed XML data.
   */
  private parseXMLFromRequest(req: Request): Promise<object> {
    return new Promise((resolve, reject) => {
      let xmlData = "";
      req.on("data", (chunk) => {
        xmlData += chunk;
      });
      req.on("end", () => {
        this.parser.parseString(xmlData, (err, result) => {
          if (err) {
            reject(err);
          } else {
            resolve(result as object);
          }
        });
      });
    });
  }
}