import { useContext, useState, useEffect, useRef, useCallback } from "react";
import { ServicesContext } from "../../services";
import { BrowserServices } from "../../models/interfaces";
import { FeatureChannelList, GetChannelsResponse } from "../../../server/models/interfaces";
import { ServerResponse } from "../../../server/models/types";

let listenCount = 0;
let promise: Promise<ServerResponse<GetChannelsResponse>> | undefined = undefined;
const LISTEN_KEY = "GET_CHANNELS_LISTEN";

const getChannels = async (props: { services: BrowserServices; force?: boolean }): Promise<ServerResponse<GetChannelsResponse>> => {
  if (promise) {
    return await promise;
  }
  try {
    promise = props.services.notificationService.getChannels();
    const result = await promise;
    window.dispatchEvent(new CustomEvent(LISTEN_KEY));
    return result;
  } catch (err) {
    return Promise.reject(err);
  }
};

export const useChannels = () => {
  const services = useContext(ServicesContext) as BrowserServices;
  const [channels, setChannels] = useState<FeatureChannelList[]>([]);
  const [loading, setLoading] = useState(true);
  const destroyRef = useRef<boolean>(false);
  const refresh = useCallback((force?: boolean) => {
    setLoading(true);
    getChannels({
      services,
      force,
    })
      .then((res) => {
        if (destroyRef.current) {
          return;
        }
        if (res && res.ok) {
          setChannels(res.response.channel_list);
        }
      })
      .finally(() => {
        if (destroyRef.current) {
          return;
        }
        setLoading(false);
      });
  }, []);
  const listenHandler = useCallback(() => {
    refresh();
  }, [refresh]);
  useEffect(() => {
    refresh();
    return () => {
      destroyRef.current = true;
    };
  }, []);

  useEffect(() => {
    window.addEventListener(LISTEN_KEY, listenHandler);
    listenCount++;
    return () => {
      window.removeEventListener(LISTEN_KEY, listenHandler);
      listenCount--;
      if (listenCount === 0) {
        promise = undefined;
      }
    };
  }, [listenHandler]);

  return {
    channels,
    loading,
    refresh,
  };
};