const dgram = require('dgram');
const server = dgram.createSocket("udp4")
const config = require('../config');
const debug = require('debug')('peers-scrape');

const ACTION_CONNECT = 0
const ACTION_ANNOUNCE = 1
const ACTION_SCRAPE = 2
const ACTION_ERROR = 3

const connectionIdHigh = 0x417
const connectionIdLow = 0x27101980
const requests = {};

let message = function (buf, host, port) {
    server.send(buf, 0, buf.length, port, host, function(err, bytes) {
        if (err) {
            console.log(err.message);
        }
    });
};

let connectTracker = function(connection) {
    debug('start screape connection');
    let buffer = new Buffer(16);

    const transactionId = Math.floor((Math.random()*100000)+1);

    buffer.fill(0);

    buffer.writeUInt32BE(connectionIdHigh, 0);
    buffer.writeUInt32BE(connectionIdLow, 4);
    buffer.writeUInt32BE(ACTION_CONNECT, 8);
    buffer.writeUInt32BE(transactionId, 12);

    // очистка старых соединений
    for(const transaction in requests) {
        if((new Date).getTime() - requests[transaction].date.getTime() > config.udpTrackersTimeout) {
            delete requests[transaction];
        }
    }

    requests[transactionId] = connection;
    message(buffer, connection.host, connection.port);
};

let scrapeTorrent = function (connectionIdHigh, connectionIdLow, transactionId) {
    let connection = requests[transactionId];
    if(!connection)
        return;

    if(!connection.hash || connection.hash.length != 40)
        return

    debug('start scrape');
    let buffer = new Buffer(56)

    buffer.fill(0);

    buffer.writeUInt32BE(connectionIdHigh, 0);
    buffer.writeUInt32BE(connectionIdLow, 4);
    buffer.writeUInt32BE(ACTION_SCRAPE, 8);
    buffer.writeUInt32BE(transactionId, 12);

    try
    {
        buffer.write(connection.hash, 16, buffer.length, 'hex');
        // do scrape
        message(buffer, connection.host, connection.port);
    } catch(error)
    {
        console.log('ERROR on scrape', error)
    }
};

server.on("message", function (msg, rinfo) {
    let buffer = new Buffer(msg)

    const action = buffer.readUInt32BE(0, 4);
    const transactionId = buffer.readUInt32BE(4, 4);
    
    if(!(transactionId in requests))
        return;

    debug("returned action: " + action);
    debug("returned transactionId: " + transactionId);

    if (action === ACTION_CONNECT) {
        debug("connect response");

        let connectionIdHigh = buffer.readUInt32BE(8, 4);
        let connectionIdLow = buffer.readUInt32BE(12, 4);

        scrapeTorrent(connectionIdHigh, connectionIdLow, transactionId);

    } else if (action === ACTION_SCRAPE) {
        debug("scrape response");

        let seeders = buffer.readUInt32BE(8, 4);
        let completed = buffer.readUInt32BE(12, 4);
        let leechers = buffer.readUInt32BE(16, 4);

        let connection = requests[transactionId];
        connection.callback({
            host: connection.host,
            port: connection.port,
            hash: connection.hash,
            seeders,
            completed,
            leechers
        })
        delete requests[transactionId];
    } else if (action === ACTION_ERROR) {
        delete requests[transactionId];
        console.log("error in scrape response");
    }
});

let getPeersStatistic = (host, port, hash, callback) => {
    let connection = {
        host, port, hash, callback, date: new Date()
    }
    connectTracker(connection);
}

server.on("listening", function () {
    var address = server.address();
    console.log("listening udp tracker respose on " + address.address + ":" + address.port);
});

server.bind(config.udpTrackersPort);

module.exports = getPeersStatistic;

//getPeersStatistic('tracker.glotorrents.com', 6969, "d096ff66557a5ea7030680967610e38b37434ea8", (data) => {
//    console.log(data)
//});