index.js

'use strict';

let fs = require('fs');
let mguri = require('magnet-uri');
let request = require('request');
let zlib = require('zlib');

let servUrl = [
    function(hash) {
        return 'http://bt.box.n0808.com/' + hash.slice(0, 2) + '/' + hash.slice(-2) + '/' + hash + '.torrent';
    },
    function(hash) {
        return 'https://torrage.com/torrent/' + hash + '.torrent';
    },
    function(hash) {
        return 'http://torcache.net/torrent/' + hash + '.torrent';
    }
    //http://btcache.me/torrent/013060CD7E3C6CD61A2CC983F1714C9359928EFE
];

function parseInfoHash(uri) {
    let uriObj = mguri.decode(uri);
    let hash = uriObj.infoHash || uri;
    if (/^[A-Za-z0-9]{40}$/.test(hash)) {
        return hash.toUpperCase();
    }
}

function getTorrent(url, hash, cb) {
    console.log('Get torrent from:', url);
    let options = {
        url: url,
        headers: {
            'User-Agent': 'Node.js/12.0 io.js/2.0',
            'Accept-Encoding': 'gzip,deflate'
        }
    };
    request.get(options)
        .on('error', function(err) {
            cb(err);
        })
        .on('response', function(response) {
            if (response.statusCode === 200) {
                if (response.headers['content-type'] === 'application/octet-stream' ||
                    response.headers['content-type'] === 'application/x-bittorrent') {
                    let filename = hash + '.torrent';
                    let dest;
                    switch (response.headers['content-encoding']) {
                    case 'gzip':
                    case 'deflate':
                        dest = response.pipe(zlib.createUnzip()).on('error', function(err) {
                            cb(err);
                        })
                        .pipe(fs.createWriteStream(filename));
                        break;
                    default:
                        dest = response.pipe(fs.createWriteStream(filename));
                        break;
                    }

                    dest.on('finish', function() {
                        cb(null, filename);
                    })
                    .on('error', function(err) {
                        cb(err);
                    });
                } else {
                    cb('Invalid content type: ' + response.headers['content-type']);
                }
            } else {
                cb('Error response: ' + response.statusCode);
            }
        });
}

module.exports = function(uri, cb) {
    let hash = parseInfoHash(uri);
    if (!hash) {
        process.nextTick(cb, 'Invalid magnet uri or info hash.');
        return;
    }

    let servIdx = 0;
    let getNext = function() {
        if (servIdx !== servUrl.length) {
            getTorrent(servUrl[servIdx++](hash), hash, function(err, filename) {
                if (err) {
                    console.log(err);
                    getNext();
                } else {
                    cb(null, filename);
                }
            });
        } else {
            process.nextTick(cb, 'All services tried.');
        }
    };

    getNext();
};