#include <utility>

#include <glog/logging.h>

#include "libstore/binary-cache-store.hh"
#include "libstore/download.hh"
#include "libstore/globals.hh"
#include "libstore/nar-info-disk-cache.hh"

namespace nix {

MakeError(UploadToHTTP, Error);

class HttpBinaryCacheStore : public BinaryCacheStore {
 private:
  Path cacheUri;

  struct State {
    bool enabled = true;
    std::chrono::steady_clock::time_point disabledUntil;
  };

  Sync<State> _state;

 public:
  HttpBinaryCacheStore(const Params& params, Path _cacheUri)
      : BinaryCacheStore(params), cacheUri(std::move(_cacheUri)) {
    if (cacheUri.back() == '/') {
      cacheUri.pop_back();
    }

    diskCache = getNarInfoDiskCache();
  }

  std::string getUri() override { return cacheUri; }

  void init() override {
    // FIXME: do this lazily?
    if (!diskCache->cacheExists(cacheUri, wantMassQuery_, priority)) {
      try {
        BinaryCacheStore::init();
      } catch (UploadToHTTP&) {
        throw Error("'%s' does not appear to be a binary cache", cacheUri);
      }
      diskCache->createCache(cacheUri, storeDir, wantMassQuery_, priority);
    }
  }

 protected:
  void maybeDisable() {
    auto state(_state.lock());
    if (state->enabled && settings.tryFallback) {
      int t = 60;
      LOG(WARNING) << "disabling binary cache '" << getUri() << "' for " << t
                   << " seconds";
      state->enabled = false;
      state->disabledUntil =
          std::chrono::steady_clock::now() + std::chrono::seconds(t);
    }
  }

  void checkEnabled() {
    auto state(_state.lock());
    if (state->enabled) {
      return;
    }
    if (std::chrono::steady_clock::now() > state->disabledUntil) {
      state->enabled = true;
      DLOG(INFO) << "re-enabling binary cache '" << getUri() << "'";
      return;
    }
    throw SubstituterDisabled("substituter '%s' is disabled", getUri());
  }

  bool fileExists(const std::string& path) override {
    checkEnabled();

    try {
      DownloadRequest request(cacheUri + "/" + path);
      request.head = true;
      getDownloader()->download(request);
      return true;
    } catch (DownloadError& e) {
      /* S3 buckets return 403 if a file doesn't exist and the
         bucket is unlistable, so treat 403 as 404. */
      if (e.error == Downloader::NotFound || e.error == Downloader::Forbidden) {
        return false;
      }
      maybeDisable();
      throw;
    }
  }

  void upsertFile(const std::string& path, const std::string& data,
                  const std::string& mimeType) override {
    auto req = DownloadRequest(cacheUri + "/" + path);
    req.data = std::make_shared<std::string>(data);  // FIXME: inefficient
    req.mimeType = mimeType;
    try {
      getDownloader()->download(req);
    } catch (DownloadError& e) {
      throw UploadToHTTP("while uploading to HTTP binary cache at '%s': %s",
                         cacheUri, e.msg());
    }
  }

  DownloadRequest makeRequest(const std::string& path) {
    DownloadRequest request(cacheUri + "/" + path);
    return request;
  }

  void getFile(const std::string& path, Sink& sink) override {
    checkEnabled();
    auto request(makeRequest(path));
    try {
      getDownloader()->download(std::move(request), sink);
    } catch (DownloadError& e) {
      if (e.error == Downloader::NotFound || e.error == Downloader::Forbidden) {
        throw NoSuchBinaryCacheFile(
            "file '%s' does not exist in binary cache '%s'", path, getUri());
      }
      maybeDisable();
      throw;
    }
  }

  void getFile(
      const std::string& path,
      Callback<std::shared_ptr<std::string>> callback) noexcept override {
    checkEnabled();

    auto request(makeRequest(path));

    auto callbackPtr =
        std::make_shared<decltype(callback)>(std::move(callback));

    getDownloader()->enqueueDownload(
        request, {[callbackPtr, this](std::future<DownloadResult> result) {
          try {
            (*callbackPtr)(result.get().data);
          } catch (DownloadError& e) {
            if (e.error == Downloader::NotFound ||
                e.error == Downloader::Forbidden) {
              return (*callbackPtr)(std::shared_ptr<std::string>());
            }
            maybeDisable();
            callbackPtr->rethrow();
          } catch (...) {
            callbackPtr->rethrow();
          }
        }});
  }
};

static RegisterStoreImplementation regStore(
    [](const std::string& uri,
       const Store::Params& params) -> std::shared_ptr<Store> {
      if (std::string(uri, 0, 7) != "http://" &&
          std::string(uri, 0, 8) != "https://" &&
          (getEnv("_NIX_FORCE_HTTP_BINARY_CACHE_STORE") != "1" ||
           std::string(uri, 0, 7) != "file://")) {
        return nullptr;
      }
      auto store = std::make_shared<HttpBinaryCacheStore>(params, uri);
      store->init();
      return store;
    });

}  // namespace nix