downloader.hpp

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#pragma once
 
#include <cstdint>
#include <memory>
#include <optional>
 
#include "download/bitfield.hpp"
#include "download/message.hpp"
#include "download/socket.hpp"
#include "peer.hpp"
#include "tfriend_fw.hpp"
#include "torrent.hpp"
#include "util/result.hpp"
 
using namespace fur::util;
using namespace fur::peer;
using namespace fur::download::socket;
using namespace fur::download::message;
 
namespace fur::download {
 
struct Downloaded {
  int64_t index;
  std::vector<uint8_t> content;
};
 
}  // namespace fur::download
 
namespace fur::download::downloader {
 
enum class DownloaderError {
  DifferentInfoHash,
  InvalidMessage,
  NoBitfield,
  MissingPiece,
  CorruptPiece,
  SocketTimeout,
  SocketOther,
};
 
DownloaderError from_socket_error(const socket::SocketError& err);
 
class Downloader {
 public:
  explicit Downloader(const TorrentFile& torrent, const Peer& peer);
 
  [[nodiscard]] Result<Downloaded, DownloaderError> try_download(const Piece&);
 
 private:
  const TorrentFile& torrent;
  const Peer& peer;
 
  std::optional<Socket> socket;
 
  bool choked = true;
  std::optional<Bitfield> bitfield;
 
 public:
  Outcome<DownloaderError> ensure_connected();
 
 private:
  Outcome<DownloaderError> handshake();
 
  Outcome<DownloaderError> send_message(const Message& msg, timeout timeout);
  Result<std::unique_ptr<Message>, DownloaderError> recv_message(
      timeout timeout);
 
  void destroy_socket();
 
  // Befriend this class so the unit tests are able to access private members.
  friend TestingFriend;
};
}  // namespace fur::download::downloader