import * as wmill from "https://deno.land/x/windmill@v1.85.0/mod.ts";

import { parse } from "https://deno.land/x/xml/mod.ts";

type Rss = {

  url: string;

};

export async function main(rss_feed: Rss) {

  const rss_feed_url = rss_feed.url;

  let feedStates = (await wmill.getInternalState()) || {};

  const newestItem: Date = new Date(feedStates[rss_feed_url] || 0);

  const items = await fetch(rss_feed_url)

    .then((response) => response.text())

    .then((str) => parse(str))

    .then((feed) => {

      let items = [];

      if (feed["rss"]) {

        items = rss2_items(feed);

      } else if (feed["feed"]) {

        items = atom_items(feed);

      }

      const new_items = items.filter((item) => item.pubDate > newestItem);

      return new_items;

    });

  if (items.length > 0) {

    let newState = (await wmill.getInternalState()) || {};

    const dates = items.map((item) => item.pubDate);

    newState[rss_feed_url] = new Date(Math.max(...dates));

    await wmill.setInternalState(newState);

  }

  return items.reverse();

}

function rss2_items(feed) {

  var items = feed["rss"]["channel"]["item"] || [];

  if (items.length === "undefined") {

    // Single entry

    items = [items];

  }

  return items.map((item) => ({

    title: item.title,

    link: item.link,

    pubDate: new Date(item.pubDate),

  }));

}

function atom_items(feed) {

  var items = feed["feed"]["entry"] || [];

  if (items.length === "undefined") {

    // Single entry

    items = [items];

  }

  return items.map((item) => ({

    title: typeof item.title === "string" ? item.title : item.title["#text"],

    link:

      item.link instanceof Array ? item.link[0]["@href"] : item.link["@href"],

    pubDate: new Date(item.updated),

  }));

}