import RSS from "rss";
import axios from "axios";
import fs from 'fs';

const API_URL = "https://aviationweather.gov/api/data/";
const METAR_SERVICE = "metar";
const feedOutput = process.env.METAR_FEED_OUTPUT;
const icao = process.env.METAR_ICAO;
const rssMetarOptions = {
    title: icao + " METAR",
    description: "METAR feed for " + icao + " Airport",
    feed_url: process.env.METAR_FEED_URL,
    site_url: process.env.METAR_SITE_URL,
    generator: "https://git.entropic.pro/Aiden/metar-rss"
}
const checkInterval = 10 * 1000 * 60; //10 Minute Check Interval


let lastMetar;
let metarRSS = new RSS(rssMetarOptions);

checkMetar(); //Inital check run
const metarCheckJob = setInterval(checkMetar, checkInterval); //Run the check every interval

/**
 * Pulls the current metar and adds it to the feed if it is new
 */
function checkMetar() {
    console.log("Checking METAR for " + icao);
    getMetar().then(res => {
        if (res.data != lastMetar) {
            console.log("New METAR: " + res.data);
            newMetar(metarRSS, res.data);
            writeFeed(metarRSS);
            lastMetar = res.data;
        }
    });
}

/**
 * Adds a new METAR to the given RSS Feed
 * @param {*} rss - RSS Feed to add the entry to
 * @param {*} metar - metar data to add
 */
function newMetar(rss, metar)  {
    let metarSplit = metar.split(" ");
    let date = new Date(Date.now());
    let eventDate = new Date(Date.UTC(date.getFullYear(), date.getMonth(), Number(metarSplit[2].substring(0,2)), Number(metarSplit[2].substring(2,4)), Number(metarSplit[2].substring(4,6))));

    rss.item({
        title: metarSplit[0] + " " + metarSplit[1] + " " + metarSplit[2],
        description: metar,
        url: API_URL + METAR_SERVICE,
        guid: metarSplit[1] + metarSplit[2],
        date: eventDate
    });
}

/**
 * Pulls METAR data from the API
 * @returns Axios generated GET Request Response
 */
function getMetar() {
    let requestURL = API_URL + METAR_SERVICE + "?ids=" + icao;
    return axios.get(requestURL);
}

/**
 * Writes the given RSS feed to the specified file
 * @param {*} rss - RSS Feed to Write
 */
function writeFeed(rss) {
    let xmlFeed = rss.xml({indent: true})
    try {
        fs.writeFileSync(feedOutput, xmlFeed);
    } catch(err) {
        console.error(err);
    }
}