import Parser from "rss-parser/index";
import { ListenerRSSInfos as ListenerInfo } from "./Models/ListenerRSSInfos";
import EventEmitter from "events";

const DEFAULT_TIMELOOP: number = 5 * 60; // default timeloop is 5 min

/**
 * Emit 'update' when he's making a fetch during the start fun
 * Emit 'update_err' when the fetch has an issue
 */
export class ListenerRss extends EventEmitter {
  name: string = "";
  address: string = "";
  timeloop: number = DEFAULT_TIMELOOP; // time in seconds
  customfields?: { [key: string]: string[] | string };

  // private fields
  parser: Parser | undefined = undefined;
  loopRunning: boolean = false;

  /**
   * @brief constructor
   * @param config ListenerRSSInfos interface who's contain the ListenerInfos
   */
  constructor(config: ListenerInfo) {
    super();

    this.setData(config);
    this.setParser();
  }

  /**
   * @brief Private function. Is useed to initilize the parser object with the customfields var
   */
  setParser() {
    // set parser
    this.parser = new Parser(
      this.customfields !== undefined
        ? {
            customFields: {
              feed: [],
              item: Object.entries(this.customfields).map(([, value]) => {
                return Array.isArray(value) ? value[0] : value;
              }),
            },
          }
        : {}
    ); // if customfield is set -> let's set the parser with, else let the option empty
  }

  /**
   * @brief Private function. Initialized the listener with an ListenerRSSInfos interface
   * @param infos ListenerRSSInfos interface who's contain the ListenerInfos
   */
  setData(infos: ListenerInfo) {
    // Set data
    this.name = infos.name;
    this.address = infos.address;
    this.timeloop =
      infos.timeloop === undefined ? DEFAULT_TIMELOOP : infos.timeloop;
    this.customfields = infos.customfields;
  }

  /**
   * @brief use the parseURL function from rss-parser with the objects datas
   * @return return a promise with the received data
   */
  fetchRSS(): Promise<Parser.Output<any>> {
    if (this.parser !== undefined && this.address !== undefined) {
      return this.parser.parseURL(this.address).catch((err) => {
        throw new Error("bad address or no access : " + err);
      });
    } else throw new Error("listener must be first initialized");
  }

  /**
   * @brief call the callback function each looptime
   * @param callback function who's going to be called with the latest get
   */
  start(): void {
    this.loopRunning = true;

    const fun: () => void = () => {
      this.fetchRSS()
        .then((obj: { [key: string]: any }) => this.emit("update", obj))
        .catch((err) => this.emit("update_err", err));
    };

    (async () => {
      while (this.loopRunning) {
        await fun();
        await new Promise((res) => setTimeout(res, this.timeloop * 1000));
      }
    })();
  }

  /**
   * @brief stop the async function
   */
  stop(): void {
    this.loopRunning = false;
  }
}