import { IServerEntry } from '../interfaces/IDnsResult';
import resolveDns from './resolveDns';

/** Time when this script started, for delta time calculations */
const startTime = Date.now();
let lastUpdate = 0;

/** List of servers, sorted by reliability */
let servers: IServerEntry[] = [];
//the master source is included by default
servers.push({ ip: '159.153.92.51', type: 'master', lastSeen: Infinity, weight: Infinity });

/** Updates the list of servers based on current DNS data */
async function heartbeatDns(domain: string) {
    //Get list of current patch servers
    const dnsResults = await resolveDns(domain);

    //Remeber time when response came in
    const now = Date.now() - startTime;

    //Schedule next check based on time-to-live, but never longer than 1 minute
    const ttl = Math.min(60, ...(dnsResults.map((obj) => obj.ttl))) + 1;
    setTimeout(heartbeatDns.bind(null, domain), ttl * 1000);

    //Update array with new information
    dnsResults.forEach(
        ({ address, type }, index) => {
            //Calculate weight:
            //on cdn-patch.swtor.com: 3 if first, 2 if second, otherwise 1
            let weight = (index < 2) ? (3 - index) : 1;
            //on Level3 US: 1.2 is first, 1 if second
            if (domain !== 'cdn-patch.swtor.com') {
              weight = (index === 0) ? 1.2 : 1;
            }

            //if ip is already contained
            for (let i = 0, il = servers.length; i < il; i += 1) {
                const server = servers[i];
                if (server.ip === address) {
                    server.lastSeen = now;
                    server.weight += weight;
                    if (server.type !== type) { server.type = type; }
                    return;
                }
            }

            //if not yet contained, add to array
            servers.push({
                ip: address,
                lastSeen: now,
                type,
                weight: weight + 1, //give a boost to new values compared to existing values
            });
        },
    );

    //Remove old entries - old = not seen for one hour
    servers = servers.filter((server) => (now - server.lastSeen) < 3600000);

    //Decay weights - reduce them based on update frequency (-50% if full minute, but less if TTL was shorter than a minute)
    const decayFactor = 0.5 ** ((now - lastUpdate) / 60000);
    lastUpdate = now;
    servers.forEach((server) => { server.weight *= decayFactor; });

    //Sort the array by weight
    servers.sort((a, b) => b.weight - a.weight);

    //Output current list
    let output = '';
    servers.forEach((server) => {
        //set colors based on server type, see https://en.wikipedia.org/wiki/ANSI_escape_code#Colors
        //bright color if seen within last 5 minutes
        if (now - server.lastSeen < 300000) { output += '\x1b[1m'; } else { output += '\x1b[0m'; }
        switch (server.type) {
            case 'master': output += '\x1b[37m'; break; //white
            case 'akamai': output += '\x1b[35m'; break; //magenta
            case 'level3-us': output += '\x1b[32m'; break; //green
            case 'level3-eu': output += '\x1b[36m'; break; //cyan
            case 'unknown': default: output += '\x1b[31m'; //red
        }
        output += server.ip;
        output += '\t';
    });
    //Reset color to default
    output += '\x1b[0m';
    console.log(output);
}

//start loading additional addresses, both from CDN, and specifically from Level3/North_America so we have more than just European servers
heartbeatDns('cdn-patch.swtor.com');
heartbeatDns('na.lvlt.cdn.ea.com.c.footprint.net');