// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/observation_store/memory_observation_store.h"

#include <utility>

#include "src/logger/logger_interface.h"
#include "src/logging.h"

namespace cobalt::observation_store {

namespace {

constexpr float kSendThresholdPercent = 0.6;

}

MemoryObservationStore::MemoryObservationStore(size_t max_bytes_per_observation,
                                               size_t max_bytes_per_envelope,
                                               size_t max_bytes_total,
                                               logger::InternalMetrics* internal_metrics)
    : ObservationStore(max_bytes_per_observation, max_bytes_per_envelope, max_bytes_total),
      envelope_send_threshold_size_(size_t(kSendThresholdPercent * max_bytes_per_envelope_)),
      current_envelope_(new EnvelopeMaker(max_bytes_per_observation, max_bytes_per_envelope)),
      finalized_envelopes_size_(0) {
  ResetInternalMetrics(internal_metrics);
}

ObservationStore::StoreStatus MemoryObservationStore::StoreObservation(
    std::unique_ptr<StoredObservation> observation, std::unique_ptr<ObservationMetadata> metadata) {
  if (IsDisabled()) {
    return kOk;
  }

  std::unique_lock<std::mutex> lock(envelope_mutex_);

  internal_metrics_->BytesStored(logger::PerProjectBytesStoredMetricDimensionStatus::Attempted,
                                 SizeLocked(), metadata->customer_id(), metadata->project_id());

  if (SizeLocked() > max_bytes_total_) {
    VLOG(4) << "MemoryObservationStore::StoreObservation(): Rejecting "
               "observation because the store is full. ("
            << SizeLocked() << " > " << max_bytes_total_ << ")";
    return kStoreFull;
  }

  ObservationStore::StoreStatus status_peek = current_envelope_->CanAddObservation(*observation);

  if (status_peek == kStoreFull) {
    VLOG(4) << "MemoryObservationStore::StoreObservation(): Current "
               "envelope would return kStoreFull. Swapping it out for "
               "a new EnvelopeMaker";
    AddEnvelopeToSend(std::move(current_envelope_));
    current_envelope_ = NewEnvelopeMaker();
  }

  uint32_t customer_id = metadata->customer_id();
  uint32_t project_id = metadata->project_id();
  uint32_t metric_id = metadata->metric_id();
  uint32_t report_id = metadata->report_id();

  ObservationStore::StoreStatus status =
      current_envelope_->StoreObservation(std::move(observation), std::move(metadata));
  if (status == kOk) {
    num_obs_per_report_[{.customer_id = customer_id,
                         .project_id = project_id,
                         .metric_id = metric_id,
                         .report_id = report_id}]++;
    internal_metrics_->BytesStored(logger::PerProjectBytesStoredMetricDimensionStatus::Succeeded,
                                   SizeLocked(), customer_id, project_id);
  }
  return status;
}

std::unique_ptr<EnvelopeMaker> MemoryObservationStore::NewEnvelopeMaker() {
  return std::make_unique<EnvelopeMaker>(max_bytes_per_observation_, max_bytes_per_envelope_);
}

std::unique_ptr<ObservationStore::EnvelopeHolder>
MemoryObservationStore::TakeOldestEnvelopeHolderLocked() {
  auto retval = std::move(finalized_envelopes_.front());
  finalized_envelopes_.pop_front();
  if (retval->Size() > finalized_envelopes_size_) {
    finalized_envelopes_size_ = 0;
  } else {
    finalized_envelopes_size_ -= retval->Size();
  }
  return retval;
}

void MemoryObservationStore::AddEnvelopeToSend(std::unique_ptr<EnvelopeHolder> holder, bool back) {
  finalized_envelopes_size_ += holder->Size();
  if (back) {
    finalized_envelopes_.push_back(std::move(holder));
  } else {
    finalized_envelopes_.push_front(std::move(holder));
  }
}

std::unique_ptr<ObservationStore::EnvelopeHolder> MemoryObservationStore::TakeNextEnvelopeHolder() {
  std::unique_lock<std::mutex> lock(envelope_mutex_);

  auto retval = NewEnvelopeMaker();
  size_t retval_size = 0;
  while (!finalized_envelopes_.empty() &&
         (retval_size == 0 ||
          (retval_size + finalized_envelopes_.front()->Size() <= max_bytes_per_envelope_))) {
    retval->MergeWith(TakeOldestEnvelopeHolderLocked());
    retval_size = retval->Size();
  }

  if (retval_size + current_envelope_->Size() <= max_bytes_per_envelope_) {
    retval->MergeWith(std::move(current_envelope_));
    current_envelope_ = NewEnvelopeMaker();
  }

  if (retval->Size() == 0) {
    return nullptr;
  }

  return retval;
}

void MemoryObservationStore::ReturnEnvelopeHolder(
    std::unique_ptr<ObservationStore::EnvelopeHolder> envelope) {
  std::unique_lock<std::mutex> lock(envelope_mutex_);
  AddEnvelopeToSend(std::move(envelope));
}

size_t MemoryObservationStore::SizeLocked() const {
  return current_envelope_->Size() + finalized_envelopes_size_;
}

size_t MemoryObservationStore::Size() const {
  std::unique_lock<std::mutex> lock(envelope_mutex_);
  return SizeLocked();
}

bool MemoryObservationStore::Empty() const {
  std::unique_lock<std::mutex> lock(envelope_mutex_);
  return current_envelope_->Empty() && finalized_envelopes_.empty();
}

void MemoryObservationStore::DeleteData() {
  VLOG(4) << "MemoryObservationStore: Deleting stored data";

  std::unique_lock<std::mutex> lock(envelope_mutex_);
  current_envelope_ = NewEnvelopeMaker();
  finalized_envelopes_.clear();
  finalized_envelopes_size_ = 0;
}

}  // namespace cobalt::observation_store