#if ENABLE_S3

#include "libstore/s3-binary-cache-store.hh"

#include <absl/strings/ascii.h>
#include <absl/strings/match.h>
#include <aws/core/Aws.h>
#include <aws/core/VersionConfig.h>
#include <aws/core/auth/AWSCredentialsProvider.h>
#include <aws/core/auth/AWSCredentialsProviderChain.h>
#include <aws/core/client/ClientConfiguration.h>
#include <aws/core/client/DefaultRetryStrategy.h>
#include <aws/core/utils/logging/FormattedLogSystem.h>
#include <aws/core/utils/logging/LogMacros.h>
#include <aws/core/utils/threading/Executor.h>
#include <aws/s3/S3Client.h>
#include <aws/s3/model/GetObjectRequest.h>
#include <aws/s3/model/HeadObjectRequest.h>
#include <aws/s3/model/ListObjectsRequest.h>
#include <aws/s3/model/PutObjectRequest.h>
#include <aws/transfer/TransferManager.h>

#include "libstore/download.hh"
#include "libstore/globals.hh"
#include "libstore/nar-info-disk-cache.hh"
#include "libstore/nar-info.hh"
#include "libstore/s3.hh"
#include "libutil/compression.hh"
#include "libutil/istringstream_nocopy.hh"

using namespace Aws::Transfer;

namespace nix {

struct S3Error : public Error {
  Aws::S3::S3Errors err;
  S3Error(Aws::S3::S3Errors err, const FormatOrString& fs)
      : Error(fs), err(err){};
};

/* Helper: given an Outcome<R, E>, return R in case of success, or
   throw an exception in case of an error. */
template <typename R, typename E>
R&& checkAws(const FormatOrString& fs, Aws::Utils::Outcome<R, E>&& outcome) {
  if (!outcome.IsSuccess())
    throw S3Error(outcome.GetError().GetErrorType(),
                  fs.s + ": " + outcome.GetError().GetMessage());
  return outcome.GetResultWithOwnership();
}

class AwsLogger : public Aws::Utils::Logging::FormattedLogSystem {
  using Aws::Utils::Logging::FormattedLogSystem::FormattedLogSystem;

  void ProcessFormattedStatement(Aws::String&& statement) override {
    debug("AWS: %s", absl::StripTrailingAsciiWhitespace(statement));
  }
};

static void initAWS() {
  static std::once_flag flag;
  std::call_once(flag, []() {
    Aws::SDKOptions options;

    /* We install our own OpenSSL locking function (see
       shared.cc), so don't let aws-sdk-cpp override it. */
    options.cryptoOptions.initAndCleanupOpenSSL = false;

    if (verbosity >= lvlDebug) {
      options.loggingOptions.logLevel =
          verbosity == lvlDebug ? Aws::Utils::Logging::LogLevel::Debug
                                : Aws::Utils::Logging::LogLevel::Trace;
      options.loggingOptions.logger_create_fn = [options]() {
        return std::make_shared<AwsLogger>(options.loggingOptions.logLevel);
      };
    }

    Aws::InitAPI(options);
  });
}

S3Helper::S3Helper(const std::string& profile, const std::string& region,
                   const std::string& scheme, const std::string& endpoint)
    : config(makeConfig(region, scheme, endpoint)),
      client(make_ref<Aws::S3::S3Client>(
          profile == ""
              ? std::dynamic_pointer_cast<Aws::Auth::AWSCredentialsProvider>(
                    std::make_shared<
                        Aws::Auth::DefaultAWSCredentialsProviderChain>())
              : std::dynamic_pointer_cast<Aws::Auth::AWSCredentialsProvider>(
                    std::make_shared<
                        Aws::Auth::ProfileConfigFileAWSCredentialsProvider>(
                        profile.c_str())),
          *config,
// FIXME: https://github.com/aws/aws-sdk-cpp/issues/759
#if AWS_VERSION_MAJOR == 1 && AWS_VERSION_MINOR < 3
          false,
#else
          Aws::Client::AWSAuthV4Signer::PayloadSigningPolicy::Never,
#endif
          endpoint.empty())) {
}

/* Log AWS retries. */
class RetryStrategy : public Aws::Client::DefaultRetryStrategy {
  bool ShouldRetry(const Aws::Client::AWSError<Aws::Client::CoreErrors>& error,
                   long attemptedRetries) const override {
    auto retry =
        Aws::Client::DefaultRetryStrategy::ShouldRetry(error, attemptedRetries);
    if (retry)
      printError("AWS error '%s' (%s), will retry in %d ms",
                 error.GetExceptionName(), error.GetMessage(),
                 CalculateDelayBeforeNextRetry(error, attemptedRetries));
    return retry;
  }
};

ref<Aws::Client::ClientConfiguration> S3Helper::makeConfig(
    const std::string& region, const std::string& scheme,
    const std::string& endpoint) {
  initAWS();
  auto res = make_ref<Aws::Client::ClientConfiguration>();
  res->region = region;
  if (!scheme.empty()) {
    res->scheme = Aws::Http::SchemeMapper::FromString(scheme.c_str());
  }
  if (!endpoint.empty()) {
    res->endpointOverride = endpoint;
  }
  res->requestTimeoutMs = 600 * 1000;
  res->connectTimeoutMs = 5 * 1000;
  res->retryStrategy = std::make_shared<RetryStrategy>();
  res->caFile = settings.caFile;
  return res;
}

S3Helper::DownloadResult S3Helper::getObject(const std::string& bucketName,
                                             const std::string& key) {
  debug("fetching 's3://%s/%s'...", bucketName, key);

  auto request =
      Aws::S3::Model::GetObjectRequest().WithBucket(bucketName).WithKey(key);

  request.SetResponseStreamFactory(
      [&]() { return Aws::New<std::stringstream>("STRINGSTREAM"); });

  DownloadResult res;

  auto now1 = std::chrono::steady_clock::now();

  try {
    auto result = checkAws(fmt("AWS error fetching '%s'", key),
                           client->GetObject(request));

    res.data =
        decompress(result.GetContentEncoding(),
                   dynamic_cast<std::stringstream&>(result.GetBody()).str());

  } catch (S3Error& e) {
    if (e.err != Aws::S3::S3Errors::NO_SUCH_KEY) {
      throw;
    }
  }

  auto now2 = std::chrono::steady_clock::now();

  res.durationMs =
      std::chrono::duration_cast<std::chrono::milliseconds>(now2 - now1)
          .count();

  return res;
}

struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore {
  const Setting<std::string> profile{
      this, "", "profile", "The name of the AWS configuration profile to use."};
  const Setting<std::string> region{
      this, Aws::Region::US_EAST_1, "region", {"aws-region"}};
  const Setting<std::string> scheme{
      this, "", "scheme",
      "The scheme to use for S3 requests, https by default."};
  const Setting<std::string> endpoint{
      this, "", "endpoint",
      "An optional override of the endpoint to use when talking to S3."};
  const Setting<std::string> narinfoCompression{
      this, "", "narinfo-compression", "compression method for .narinfo files"};
  const Setting<std::string> lsCompression{this, "", "ls-compression",
                                           "compression method for .ls files"};
  const Setting<std::string> logCompression{
      this, "", "log-compression", "compression method for log/* files"};
  const Setting<bool> multipartUpload{this, false, "multipart-upload",
                                      "whether to use multi-part uploads"};
  const Setting<uint64_t> bufferSize{
      this, 5 * 1024 * 1024, "buffer-size",
      "size (in bytes) of each part in multi-part uploads"};

  std::string bucketName;

  Stats stats;

  S3Helper s3Helper;

  S3BinaryCacheStoreImpl(const Params& params, const std::string& bucketName)
      : S3BinaryCacheStore(params),
        bucketName(bucketName),
        s3Helper(profile, region, scheme, endpoint) {
    diskCache = getNarInfoDiskCache();
  }

  std::string getUri() override { return "s3://" + bucketName; }

  void init() override {
    if (!diskCache->cacheExists(getUri(), wantMassQuery_, priority)) {
      BinaryCacheStore::init();

      diskCache->createCache(getUri(), storeDir, wantMassQuery_, priority);
    }
  }

  const Stats& getS3Stats() override { return stats; }

  /* This is a specialisation of isValidPath() that optimistically
     fetches the .narinfo file, rather than first checking for its
     existence via a HEAD request. Since .narinfos are small, doing
     a GET is unlikely to be slower than HEAD. */
  bool isValidPathUncached(const Path& storePath) override {
    try {
      queryPathInfo(storePath);
      return true;
    } catch (InvalidPath& e) {
      return false;
    }
  }

  bool fileExists(const std::string& path) override {
    stats.head++;

    auto res = s3Helper.client->HeadObject(Aws::S3::Model::HeadObjectRequest()
                                               .WithBucket(bucketName)
                                               .WithKey(path));

    if (!res.IsSuccess()) {
      auto& error = res.GetError();
      if (error.GetErrorType() == Aws::S3::S3Errors::RESOURCE_NOT_FOUND ||
          error.GetErrorType() == Aws::S3::S3Errors::NO_SUCH_KEY
          // If bucket listing is disabled, 404s turn into 403s
          || error.GetErrorType() == Aws::S3::S3Errors::ACCESS_DENIED)
        return false;
      throw Error(format("AWS error fetching '%s': %s") % path %
                  error.GetMessage());
    }

    return true;
  }

  std::shared_ptr<TransferManager> transferManager;
  std::once_flag transferManagerCreated;

  void uploadFile(const std::string& path, const std::string& data,
                  const std::string& mimeType,
                  const std::string& contentEncoding) {
    auto stream = std::make_shared<istringstream_nocopy>(data);

    auto maxThreads = std::thread::hardware_concurrency();

    static std::shared_ptr<Aws::Utils::Threading::PooledThreadExecutor>
        executor =
            std::make_shared<Aws::Utils::Threading::PooledThreadExecutor>(
                maxThreads);

    std::call_once(transferManagerCreated, [&]() {
      if (multipartUpload) {
        TransferManagerConfiguration transferConfig(executor.get());

        transferConfig.s3Client = s3Helper.client;
        transferConfig.bufferSize = bufferSize;

        transferConfig.uploadProgressCallback =
            [](const TransferManager* transferManager,
               const std::shared_ptr<const TransferHandle>& transferHandle) {
              // FIXME: find a way to properly abort the multipart upload.
              // checkInterrupt();
              debug("upload progress ('%s'): '%d' of '%d' bytes",
                    transferHandle->GetKey(),
                    transferHandle->GetBytesTransferred(),
                    transferHandle->GetBytesTotalSize());
            };

        transferManager = TransferManager::Create(transferConfig);
      }
    });

    auto now1 = std::chrono::steady_clock::now();

    if (transferManager) {
      if (contentEncoding != "")
        throw Error(
            "setting a content encoding is not supported with S3 multi-part "
            "uploads");

      std::shared_ptr<TransferHandle> transferHandle =
          transferManager->UploadFile(stream, bucketName, path, mimeType,
                                      Aws::Map<Aws::String, Aws::String>(),
                                      nullptr /*, contentEncoding */);

      transferHandle->WaitUntilFinished();

      if (transferHandle->GetStatus() == TransferStatus::FAILED)
        throw Error("AWS error: failed to upload 's3://%s/%s': %s", bucketName,
                    path, transferHandle->GetLastError().GetMessage());

      if (transferHandle->GetStatus() != TransferStatus::COMPLETED)
        throw Error(
            "AWS error: transfer status of 's3://%s/%s' in unexpected state",
            bucketName, path);

    } else {
      auto request = Aws::S3::Model::PutObjectRequest()
                         .WithBucket(bucketName)
                         .WithKey(path);

      request.SetContentType(mimeType);

      if (contentEncoding != "") {
        request.SetContentEncoding(contentEncoding);
      }

      auto stream = std::make_shared<istringstream_nocopy>(data);

      request.SetBody(stream);

      auto result = checkAws(fmt("AWS error uploading '%s'", path),
                             s3Helper.client->PutObject(request));
    }

    auto now2 = std::chrono::steady_clock::now();

    auto duration =
        std::chrono::duration_cast<std::chrono::milliseconds>(now2 - now1)
            .count();

    printInfo(format("uploaded 's3://%1%/%2%' (%3% bytes) in %4% ms") %
              bucketName % path % data.size() % duration);

    stats.putTimeMs += duration;
    stats.putBytes += data.size();
    stats.put++;
  }

  void upsertFile(const std::string& path, const std::string& data,
                  const std::string& mimeType) override {
    if (narinfoCompression != "" && absl::EndsWith(path, ".narinfo"))
      uploadFile(path, *compress(narinfoCompression, data), mimeType,
                 narinfoCompression);
    else if (lsCompression != "" && absl::EndsWith(path, ".ls"))
      uploadFile(path, *compress(lsCompression, data), mimeType, lsCompression);
    else if (logCompression != "" && absl::StartsWith(path, "log/"))
      uploadFile(path, *compress(logCompression, data), mimeType,
                 logCompression);
    else
      uploadFile(path, data, mimeType, "");
  }

  void getFile(const std::string& path, Sink& sink) override {
    stats.get++;

    // FIXME: stream output to sink.
    auto res = s3Helper.getObject(bucketName, path);

    stats.getBytes += res.data ? res.data->size() : 0;
    stats.getTimeMs += res.durationMs;

    if (res.data) {
      printTalkative("downloaded 's3://%s/%s' (%d bytes) in %d ms", bucketName,
                     path, res.data->size(), res.durationMs);

      sink((unsigned char*)res.data->data(), res.data->size());
    } else
      throw NoSuchBinaryCacheFile(
          "file '%s' does not exist in binary cache '%s'", path, getUri());
  }

  PathSet queryAllValidPaths() override {
    PathSet paths;
    std::string marker;

    do {
      debug(format("listing bucket 's3://%s' from key '%s'...") % bucketName %
            marker);

      auto res = checkAws(
          format("AWS error listing bucket '%s'") % bucketName,
          s3Helper.client->ListObjects(Aws::S3::Model::ListObjectsRequest()
                                           .WithBucket(bucketName)
                                           .WithDelimiter("/")
                                           .WithMarker(marker)));

      auto& contents = res.GetContents();

      debug(format("got %d keys, next marker '%s'") % contents.size() %
            res.GetNextMarker());

      for (auto object : contents) {
        auto& key = object.GetKey();
        if (key.size() != 40 || !absl::EndsWith(key, ".narinfo")) {
          continue;
        }
        paths.insert(storeDir + "/" + key.substr(0, key.size() - 8));
      }

      marker = res.GetNextMarker();
    } while (!marker.empty());

    return paths;
  }
};

static RegisterStoreImplementation regStore(
    [](const std::string& uri,
       const Store::Params& params) -> std::shared_ptr<Store> {
      if (std::string(uri, 0, 5) != "s3://") {
        return 0;
      }
      auto store =
          std::make_shared<S3BinaryCacheStoreImpl>(params, std::string(uri, 5));
      store->init();
      return store;
    });

}  // namespace nix

#endif