#pragma once

#include <future>
#include <string>

#include "libstore/globals.hh"
#include "libutil/hash.hh"
#include "libutil/types.hh"

namespace nix {

struct DownloadSettings : Config {
  Setting<bool> enableHttp2{this, true, "http2",
                            "Whether to enable HTTP/2 support."};

  Setting<std::string> userAgentSuffix{
      this, "", "user-agent-suffix",
      "String appended to the user agent in HTTP requests."};

  Setting<size_t> httpConnections{this,
                                  25,
                                  "http-connections",
                                  "Number of parallel HTTP connections.",
                                  {"binary-caches-parallel-connections"}};

  Setting<unsigned long> connectTimeout{
      this, 0, "connect-timeout",
      "Timeout for connecting to servers during downloads. 0 means use curl's "
      "builtin default."};

  Setting<unsigned long> stalledDownloadTimeout{
      this, 300, "stalled-download-timeout",
      "Timeout (in seconds) for receiving data from servers during download. "
      "Nix cancels idle downloads after this timeout's duration."};

  Setting<unsigned int> tries{
      this, 5, "download-attempts",
      "How often Nix will attempt to download a file before giving up."};
};

extern DownloadSettings downloadSettings;

struct DownloadRequest {
  std::string uri;
  std::string expectedETag;
  bool verifyTLS = true;
  bool head = false;
  size_t tries = downloadSettings.tries;
  unsigned int baseRetryTimeMs = 250;
  bool decompress = true;
  std::shared_ptr<std::string> data;
  std::string mimeType;
  std::function<void(char*, size_t)> dataCallback;

  DownloadRequest(const std::string& uri) : uri(uri) {}

  std::string verb() { return data ? "upload" : "download"; }
};

struct DownloadResult {
  bool cached = false;
  std::string etag;
  std::string effectiveUri;
  std::shared_ptr<std::string> data;
  uint64_t bodySize = 0;
};

struct CachedDownloadRequest {
  std::string uri;
  bool unpack = false;
  std::string name;
  Hash expectedHash;
  unsigned int ttl = settings.tarballTtl;

  CachedDownloadRequest(const std::string& uri) : uri(uri) {}
};

struct CachedDownloadResult {
  // Note: 'storePath' may be different from 'path' when using a
  // chroot store.
  Path storePath;
  Path path;
  std::optional<std::string> etag;
  std::string effectiveUri;
};

class Store;

struct Downloader {
  virtual ~Downloader() {}

  /* Enqueue a download request, returning a future to the result of
     the download. The future may throw a DownloadError
     exception. */
  virtual void enqueueDownload(const DownloadRequest& request,
                               Callback<DownloadResult> callback) = 0;

  std::future<DownloadResult> enqueueDownload(const DownloadRequest& request);

  /* Synchronously download a file. */
  DownloadResult download(const DownloadRequest& request);

  /* Download a file, writing its data to a sink. The sink will be
     invoked on the thread of the caller. */
  void download(DownloadRequest&& request, Sink& sink);

  /* Check if the specified file is already in ~/.cache/nix/tarballs
     and is more recent than ‘tarball-ttl’ seconds. Otherwise,
     use the recorded ETag to verify if the server has a more
     recent version, and if so, download it to the Nix store. */
  CachedDownloadResult downloadCached(const ref<Store>& store,
                                      const CachedDownloadRequest& request);

  enum Error { NotFound, Forbidden, Misc, Transient, Interrupted };
};

/* Return a shared Downloader object. Using this object is preferred
   because it enables connection reuse and HTTP/2 multiplexing. */
ref<Downloader> getDownloader();

/* Return a new Downloader object. */
ref<Downloader> makeDownloader();

class DownloadError : public Error {
 public:
  Downloader::Error error;
  DownloadError(Downloader::Error error, const FormatOrString& fs)
      : Error(fs), error(error) {}
};

bool isUri(const std::string& s);

}  // namespace nix