Trigger everytime a new item text on HackerNews match at least one mention

import {

  getState,

  setState,

} from "https://deno.land/x/[email protected]/mod.ts";

const MAX_LOOKBACK = 100;

/**

 * @param mentions Case **insensitive** phrases that should be searched for.

 */

export async function main(mentions: string[]) {

  let lastState = await getState();

  let maxItem = await getMaxItem();

  if (!lastState) {

    lastState = maxItem - MAX_LOOKBACK;

  }

  maxItem = Math.min(maxItem, lastState + MAX_LOOKBACK);

  const items = [];

  for (let i = lastState; i < maxItem; i++) {

    const item = await getItem(i);

    if (

      mentions.find((mention) => {

        if (!item.text) return false;

        const m = mention.trim().toLowerCase();

        return item.text.toLowerCase().includes(m);

      })

    ) {

      items.push(item);

    }

  }

  await setState(maxItem);

  return items;

}

export async function getMaxItem() {

  const res = await fetch("https://hacker-news.firebaseio.com/v0/maxitem.json");

  return Number(await res.text());

}

export async function getItem(id: number) {

  const res = await fetch(

    `https://hacker-news.firebaseio.com/v0/item/${id}.json`,

  );

  return res.json();

}