#include "tlbmc/service/hft_service.h"

#include <cstddef>
#include <cstdint>
#include <memory>
#include <queue>
#include <string>
#include <utility>

#include "absl/base/thread_annotations.h"
#include "absl/functional/any_invocable.h"
#include "absl/log/log.h"
#include "absl/strings/substitute.h"
#include "absl/synchronization/mutex.h"
#include "grpcpp/server_context.h"
#include "grpcpp/support/server_callback.h"
#include "grpcpp/support/status.h"
#include "hft_service.pb.h"
#include "tlbmc/subscription/manager.h"
#include "payload.pb.h"
#include "subscription_params.pb.h"
#include "bmcweb_authorizer_singleton.h"
#include "zatar/bmcweb_cert_provider.h"

namespace milotic_hft {

using ::milotic::authz::BmcWebAuthorizerSingleton;
using ::milotic::redfish::BmcWebCertProvider;

namespace internal {

ServerReactorImpl::ServerReactorImpl(
    absl::AnyInvocable<void(ServerReactorImpl *)> on_done,
    std::size_t maximum_event_queue_size)
    : on_done_(std::move(on_done)),
      maximum_event_queue_size_(maximum_event_queue_size) {}

void ServerReactorImpl::SafeFinish(const grpc::Status &status)
    ABSL_LOCKS_EXCLUDED(mutex_) {
  absl::MutexLock lock(&mutex_);
  if (status_ == Status::kFinishCalled || status_ == Status::kFinished) {
    return;
  }
  status_ = Status::kFinishCalled;
  Finish(status);
}

bool ServerReactorImpl::AddResponse(HftResponse &&response)
    ABSL_LOCKS_EXCLUDED(mutex_) {
  absl::MutexLock lock(&mutex_);
  switch (status_) {
    case Status::kIdle:
    case Status::kWriteInFlight:
      break;
    case Status::kFinishCalled:
    case Status::kFinished:
      DLOG(WARNING) << "Stream is finished or finishing";
      return false;
  }
  if (response_queue_.size() >= maximum_event_queue_size_) {
    DLOG(WARNING) << "Response queue is full, dropping response";
    return false;
  }
  response_queue_.push(response);
  if (status_ == Status::kIdle) {
    status_ = Status::kWriteInFlight;
    DLOG(INFO) << "StartWrite from idle";
    StartWrite(&response_queue_.front());
  }
  return true;
}

ServerReactorImpl::Status ServerReactorImpl::GetStatus() const
    ABSL_LOCKS_EXCLUDED(mutex_) {
  absl::MutexLock lock(&mutex_);
  return status_;
}

void ServerReactorImpl::OnWriteDone(bool ok) ABSL_LOCKS_EXCLUDED(mutex_) {
  DLOG(INFO) << "OnWriteDone";
  absl::MutexLock lock(&mutex_);
  if (status_ != Status::kWriteInFlight) {
    LOG(WARNING)
        << "OnWriteDone called when the stream is not write in flight: "
        << StatusToString(status_);
    return;
  }
  if (!ok) {
    LOG(ERROR) << "Failed to write response";
    status_ = Status::kFinishCalled;
    Finish(
        grpc::Status(grpc::StatusCode::INTERNAL, "Failed to write response"));
    return;
  }
  response_queue_.pop();
  if (response_queue_.empty()) {
    status_ = Status::kIdle;
  } else {
    DLOG(INFO) << "StartWrite from OnWriteDone";
    StartWrite(&response_queue_.front());
  }
}

void ServerReactorImpl::OnCancel() {
  DLOG(INFO) << "OnCancel";
  absl::MutexLock lock(&mutex_);
  if (status_ == Status::kFinishCalled || status_ == Status::kFinished) {
    return;
  }
  status_ = Status::kFinishCalled;
  Finish(
      grpc::Status(grpc::StatusCode::CANCELLED, "Client cancelled requests."));
}

void ServerReactorImpl::OnDone() {
  DLOG(INFO) << "OnDone";
  {
    absl::MutexLock lock(&mutex_);
    if (status_ == Status::kFinished) {
      return;
    }
    status_ = Status::kFinished;
  }
  on_done_(this);
  // At this moment, the reactor must not be used anymore.
}

}  // namespace internal

uint64_t HftServiceImpl::GetAccumulativeSampleRate(
    const std::string &role) const {
  absl::MutexLock lock(&mutex_);
  auto it = role_to_total_sample_rate_.find(role);
  if (it != role_to_total_sample_rate_.end()) {
    return it->second;
  }
  return 0;
}

uint64_t HftServiceImpl::GetDecreaseSampleRateWhenFinishedCount() const {
  absl::MutexLock lock(&mutex_);
  return reactor_should_decrease_sample_rate_when_finished_.size();
}

uint64_t HftServiceImpl::GetReactorsCount() const {
  absl::MutexLock lock(&mutex_);
  return reactor_map_.size();
}

uint64_t HftServiceImpl::GetRoleToTotalSampleRateCount() const {
  absl::MutexLock lock(&mutex_);
  return role_to_total_sample_rate_.size();
}

uint64_t HftServiceImpl::GetReactorToSubscriptionIdsCount() const {
  absl::MutexLock lock(&mutex_);
  return reactor_to_subscription_ids_.size();
}

HftServiceImpl::HftServiceImpl(
    const HftServiceOptions &options,
    std::unique_ptr<SubscriptionManager> subscription_manager)
    : options_(options),
      subscription_manager_(std::move(subscription_manager)) {}

grpc::ServerWriteReactor<HftResponse> *HftServiceImpl::Subscribe(
    grpc::CallbackServerContext *context, const HftRequest *request) {
  BmcWebAuthorizerSingleton &bmcweb_authorizer =
      BmcWebAuthorizerSingleton::GetInstance();
  std::string role;
  grpc::Status authz_status = bmcweb_authorizer.GetPeerRoleFromAuthContext(
      *context->auth_context(), role);
  return SubscribeWithStatus(request, role, authz_status);
}

grpc::ServerWriteReactor<HftResponse> *HftServiceImpl::SubscribeWithStatus(
    const HftRequest *request, const std::string &role,
    grpc::Status authz_status) {
  using internal::ServerReactorImpl;
  BmcWebAuthorizerSingleton &bmcweb_authorizer =
      BmcWebAuthorizerSingleton::GetInstance();
  uint64_t total_sample_rate = 0;
  // TODO(nanzhou): limit subscriptions for "all" resources as well. For now,
  // assume that subscriptions all come with explicit identifiers.
  for (const SubscriptionParams &subscription : request->subscriptions()) {
    total_sample_rate += 1000 / subscription.sampling_interval_ms();
  }
  // Only allows subscriptions if the server has root certs and prod signed
  // cert.
  if (options_.cert_provider == nullptr ||
      options_.cert_provider->GetServerStatus() !=
          BmcWebCertProvider::ServerStatus::kWithRootCertsAndProdSignedCert) {
    authz_status = grpc::Status(
        grpc::StatusCode::PERMISSION_DENIED,
        "The server does not have root certs and prod signed cert.");
  }

  absl::AnyInvocable<void(ServerReactorImpl *)> on_reactor_done =
      [this, total_sample_rate, role](ServerReactorImpl *reactor) {
        absl::MutexLock lock(&mutex_);
        if (auto it = role_to_total_sample_rate_.find(role);
            !role.empty() &&
            reactor_should_decrease_sample_rate_when_finished_.contains(
                reactor) &&
            it != role_to_total_sample_rate_.end()) {
          it->second = it->second - total_sample_rate;
          DLOG(INFO) << "role: " << role
                     << " total_sample_rate: " << total_sample_rate
                     << " role_to_total_sample_rate_: "
                     << role_to_total_sample_rate_[role];
          if (it->second == 0) {
            role_to_total_sample_rate_.erase(it);
          }
        }
        reactor_should_decrease_sample_rate_when_finished_.erase(reactor);
        for (const SubscriptionManager::SubscriptionId &subscription_id :
             reactor_to_subscription_ids_[reactor]) {
          if (absl::Status status =
                  subscription_manager_->Unsubscribe(subscription_id);
              !status.ok()) {
            LOG(WARNING) << "Failed to unsubscribe subscription: " << status;
          }
        }
        reactor_to_subscription_ids_.erase(reactor);
        reactor_map_.erase(reactor);
      };

  std::shared_ptr<ServerReactorImpl> reactor =
      std::make_shared<ServerReactorImpl>(std::move(on_reactor_done),
                                          options_.maximum_event_queue_size);
  {
    absl::MutexLock lock(&mutex_);
    reactor_map_[reactor.get()] = reactor;
  }

  if (!authz_status.ok() && options_.enable_authorization) {
    reactor->SafeFinish(authz_status);
  }
  if (authz_status.ok() && options_.enable_authorization) {
    absl::MutexLock lock(&mutex_);
    uint64_t new_total_sample_rate = total_sample_rate;
    auto it = role_to_total_sample_rate_.find(role);
    if (it != role_to_total_sample_rate_.end()) {
      new_total_sample_rate += it->second;
    }
    uint64_t sample_rate_limit = bmcweb_authorizer.GetSampleRateLimit(role);
    if (new_total_sample_rate > sample_rate_limit &&
        options_.enable_authorization) {
      reactor->SafeFinish(grpc::Status(
          grpc::StatusCode::RESOURCE_EXHAUSTED,
          absl::Substitute(
              "Role $0 has reached the maximum allowed sample "
              "rate of $1, currently $2, new total sample rate "
              "after this RPC: $3",
              role, sample_rate_limit,
              it == role_to_total_sample_rate_.end() ? 0 : it->second,
              new_total_sample_rate)));
    } else {
      role_to_total_sample_rate_[role] = new_total_sample_rate;
      reactor_should_decrease_sample_rate_when_finished_.insert(reactor.get());
    }
  }

  if (reactor->GetStatus() != ServerReactorImpl::Status::kFinishCalled &&
      reactor->GetStatus() != ServerReactorImpl::Status::kFinished) {
    for (const SubscriptionParams &subscription : request->subscriptions()) {
      absl::AnyInvocable<void(Payload &&)> on_data_callback =
          [reactor](Payload &&payload) mutable {
            if (!reactor) return;
            // If reactor ever reports that it is finished, we should never
            // access it again.
            if (reactor->GetStatus() == ServerReactorImpl::Status::kFinished) {
              reactor = nullptr;
              return;
            }
            // If reactor is about to finish, we should return and wait until
            // it is actually finished. We must not start a new StartWrite().
            if (reactor->GetStatus() ==
                ServerReactorImpl::Status::kFinishCalled) {
              return;
            }
            HftResponse response;
            *response.add_payloads() = std::move(payload);
            bool added = reactor->AddResponse(std::move(response));
            if (!added) {
              DLOG(WARNING) << "Failed to add response";
            }
          };
      absl::StatusOr<SubscriptionManager::SubscriptionId> subscription_id =
          subscription_manager_->AddSubscription(subscription,
                                                 std::move(on_data_callback));
      if (!subscription_id.ok()) {
        reactor->SafeFinish(
            grpc::Status(grpc::StatusCode::INTERNAL,
                         absl::Substitute("Failed to add subscription: $0",
                                          subscription_id.status().message())));
      } else {
        absl::MutexLock lock(&mutex_);
        reactor_to_subscription_ids_[reactor.get()].push_back(*subscription_id);
      }
    }
  }

  if (request->subscriptions_size() == 0) {
    reactor->SafeFinish(grpc::Status(grpc::StatusCode::INVALID_ARGUMENT,
                                     "No subscription is provided."));
  }
  return reactor.get();
}

}  // namespace milotic_hft