const DHT = require('bittorrent-dht');

class DhtWrapper {
  constructor(DHT_PORT = 20000) {
    this._peerMap = new Map();
    this._port = DHT_PORT;

    this._dht = new DHT();
    this._dht.listen(this._port);
    this._dht.on('peer', ({ host, port }, infoHash) => {
      const hexHash = Buffer.from(infoHash).toString('hex');
      if (!this._peerMap.has(hexHash)) {
        return;
      }
      this._peerMap.get(hexHash).add(`${host}:${port}`);
    });
  }
  async lookup(infoHash) {
    const peers = new Set();
    this._peerMap.set(infoHash, peers);
    return await new Promise((resolve, reject) => {
      this._dht.lookup(infoHash, (e) => {
        if (!!e) {
          reject(e);
          return;
        }
        if (this._peerMap.get(infoHash) === peers) {
          this._peerMap.delete(infoHash);
        }
        resolve(Array.from(peers));
      });
    });
  }
}

module.exports = DhtWrapper;