// Copyright 2020 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/lib/metrics_buffer/metrics_buffer.h"

#include <inttypes.h>
#include <lib/async-loop/default.h>
#include <lib/async-loop/loop.h>
//#include <lib/syslog/global.h>
#include <lib/async/cpp/task.h>
#include <zircon/assert.h>
#include <zircon/types.h>

#include <mutex>

#include <src/lib/cobalt/cpp/cobalt_event_builder.h>

#include "log.h"

namespace cobalt {

// static
std::shared_ptr<MetricsBuffer> MetricsBuffer::Create(uint32_t project_id) {
  return std::shared_ptr<MetricsBuffer>(new MetricsBuffer(project_id));
}

// static
std::shared_ptr<MetricsBuffer> MetricsBuffer::Create(
    uint32_t project_id, std::shared_ptr<sys::ServiceDirectory> service_directory) {
  return std::shared_ptr<MetricsBuffer>(new MetricsBuffer(project_id, service_directory));
}

MetricsBuffer::MetricsBuffer(uint32_t project_id) : project_id_(project_id) {
  std::lock_guard<std::mutex> lock(lock_);
  ZX_DEBUG_ASSERT(!loop_ && !cobalt_logger_);
}

MetricsBuffer::MetricsBuffer(uint32_t project_id,
                             std::shared_ptr<sys::ServiceDirectory> service_directory)
    : project_id_(project_id) {
  SetServiceDirectory(service_directory);
}

MetricsBuffer::~MetricsBuffer() { SetServiceDirectory(nullptr); }

void MetricsBuffer::SetServiceDirectory(std::shared_ptr<sys::ServiceDirectory> service_directory) {
  std::unique_ptr<cobalt::CobaltLogger> logger_to_delete_outside_lock;
  std::unique_ptr<async::Loop> loop_to_stop_outside_lock;
  {  // scope lock
    std::lock_guard<std::mutex> lock(lock_);
    ZX_DEBUG_ASSERT(!!loop_ == !!cobalt_logger_);
    if (cobalt_logger_) {
      ZX_DEBUG_ASSERT(loop_);
      // Clean these up after we've released lock_, to avoid potential deadlock waiting on a thread
      // that may be trying to get lock_.
      loop_to_stop_outside_lock = std::move(loop_);
      logger_to_delete_outside_lock = std::move(cobalt_logger_);
    }
    ZX_DEBUG_ASSERT(!loop_ && !cobalt_logger_);
    if (service_directory) {
      std::unique_ptr<cobalt::CobaltLogger> new_logger;
      auto loop = std::make_unique<async::Loop>(&kAsyncLoopConfigNoAttachToCurrentThread);
      zx_status_t status = loop->StartThread("MetricsBuffer");
      if (status != ZX_OK) {
        LOG(WARNING, "MetricsBuffer::SetServiceDirectory() thread creation failed.");
        // ~loop
        // ~service_directory
        return;
      }
      zx::event cobalt_logger_creation_done;
      status = zx::event::create(/*options=*/0, &cobalt_logger_creation_done);
      if (status != ZX_OK) {
        LOG(WARNING, "zx::event::create() failed - status: %d", status);
        // ~loop
        // ~service_directory
        return;
      }
      // Must create cobalt::CobaltLogger on same dispatcher that it'll use.
      async::PostTask(loop->dispatcher(),
                      [this, &loop, &service_directory, &new_logger, &cobalt_logger_creation_done] {
                        new_logger = cobalt::NewCobaltLoggerFromProjectId(
                            loop->dispatcher(), service_directory, project_id_);
                        cobalt_logger_creation_done.signal(0, ZX_EVENT_SIGNALED);
                      });
      zx_signals_t observed = 0;
      status =
          cobalt_logger_creation_done.wait_one(ZX_EVENT_SIGNALED, zx::time::infinite(), &observed);
      if (status != ZX_OK) {
        // ~loop
        // ~new_logger
        return;
      }
      ZX_DEBUG_ASSERT((observed & ZX_EVENT_SIGNALED) != 0);
      loop_ = std::move(loop);
      cobalt_logger_ = std::move(new_logger);
      ZX_DEBUG_ASSERT(!!loop_ && !!cobalt_logger_);
      if (!pending_counts_.empty()) {
        LOG(INFO, "MetricsBuffer::SetServiceDirectory() flushing counts soon.");
        TryPostFlushCountsLocked();
      }
    }
    ZX_DEBUG_ASSERT(!!loop_ == !!cobalt_logger_);
  }  // ~lock
  ZX_DEBUG_ASSERT(!!loop_to_stop_outside_lock == !!logger_to_delete_outside_lock);
  if (loop_to_stop_outside_lock) {
    // Stop the loop first, to avoid any async tasks queued by the CobaltLogger outlasting the
    // CobaltLogger.
    loop_to_stop_outside_lock->Quit();
    loop_to_stop_outside_lock->JoinThreads();
    loop_to_stop_outside_lock->Shutdown();
    // Delete here for clarity.
    loop_to_stop_outside_lock = nullptr;
    // Now it's safe to delete the CobaltLogger, which we do here manually for clarity.
    logger_to_delete_outside_lock = nullptr;
  }
}

void MetricsBuffer::SetMinLoggingPeriod(zx::duration min_logging_period) {
  std::lock_guard<std::mutex> lock(lock_);
  ZX_DEBUG_ASSERT(last_flushed_ == zx::time::infinite_past());
  min_logging_period_ = min_logging_period;
}

void MetricsBuffer::LogEventCount(uint32_t metric_id, std::vector<uint32_t> dimension_values,
                                  uint32_t count) {
  std::lock_guard<std::mutex> lock(lock_);
  ZX_DEBUG_ASSERT(!!loop_ == !!cobalt_logger_);
  bool was_empty = pending_counts_.empty();
  PendingCountsKey key(metric_id, std::move(dimension_values));
  pending_counts_[key] += count;
  if (was_empty) {
    // We don't try to process locally, because if we're logging infrequently then the optimization
    // wouldn't matter, and if we're logging frequently then we need to post in order to delay
    // anyway.  So we opt to keep the code simpler and always post even if the deadline is in the
    // past.
    TryPostFlushCountsLocked();
  }
}

void MetricsBuffer::LogEvent(uint32_t metric_id, std::vector<uint32_t> dimension_values) {
  LogEventCount(metric_id, std::move(dimension_values), 1);
}

void MetricsBuffer::FlushPendingEventCounts() {
  std::lock_guard<std::mutex> lock(lock_);
  ZX_DEBUG_ASSERT(!!loop_ == !!cobalt_logger_);
  if (!cobalt_logger_) {
    // In some testing scenarios, we may not have access to a real LoggerFactory, and we can end up
    // here if SetServiceDirectory() hit an error while (or shortly after) switching from an old
    // loop_ and cobalt_logger_ to a new loop_ and cobalt_logger_.
    //
    // If later we get a new cobalt_logger_ from a new SetServiceDirectory(), this method will run
    // again.
    return;
  }
  last_flushed_ = zx::clock::get_monotonic();
  PendingCounts snapped_pending_event_counts;
  snapped_pending_event_counts.swap(pending_counts_);
  auto iter = snapped_pending_event_counts.begin();
  constexpr uint32_t kMaxBatchSize = 64;
  std::vector<fuchsia::cobalt::CobaltEvent> batch;
  while (iter != snapped_pending_event_counts.end()) {
    auto [key, count] = *iter;
    iter++;
    batch.emplace_back(cobalt::CobaltEventBuilder(key.metric_id())
                           .with_event_codes(key.dimension_values())
                           .as_count_event(/*period_duration_micros=*/0, count));
    ZX_DEBUG_ASSERT(batch.size() <= kMaxBatchSize);
    if (batch.size() == kMaxBatchSize || iter == snapped_pending_event_counts.end()) {
      cobalt_logger_->LogCobaltEvents(std::move(batch));
      ZX_DEBUG_ASSERT(batch.empty());
    }
  }
}

void MetricsBuffer::TryPostFlushCountsLocked() {
  ZX_DEBUG_ASSERT(!!loop_ == !!cobalt_logger_);
  if (cobalt_logger_) {
    ZX_DEBUG_ASSERT(loop_);
    async::PostTaskForTime(
        loop_->dispatcher(), [this] { FlushPendingEventCounts(); },
        last_flushed_ + min_logging_period_);
  }
}

MetricsBuffer::PendingCountsKey::PendingCountsKey(uint32_t metric_id,
                                                  std::vector<uint32_t> dimension_values)
    : metric_id_(metric_id), dimension_values_(dimension_values) {}

uint32_t MetricsBuffer::PendingCountsKey::metric_id() const { return metric_id_; }

const std::vector<uint32_t>& MetricsBuffer::PendingCountsKey::dimension_values() const {
  return dimension_values_;
}

size_t MetricsBuffer::PendingCountsKeyHash::operator()(const PendingCountsKey& key) const noexcept {
  // Rely on size_t being unsigned so it'll wrap without being undefined behavior.
  size_t hash = hash_uint32_(key.metric_id());
  for (auto value : key.dimension_values()) {
    hash += hash_uint32_(value);
  }
  return hash;
}

bool MetricsBuffer::PendingCountsKeyEqual::operator()(const PendingCountsKey& lhs,
                                                      const PendingCountsKey& rhs) const noexcept {
  if (lhs.metric_id() != rhs.metric_id()) {
    return false;
  }
  if (lhs.dimension_values().size() != rhs.dimension_values().size()) {
    return false;
  }
  size_t size = lhs.dimension_values().size();
  for (uint32_t i = 0; i < size; ++i) {
    if (lhs.dimension_values()[i] != rhs.dimension_values()[i]) {
      return false;
    }
  }
  return true;
}

MetricBuffer MetricsBuffer::CreateMetricBuffer(uint32_t metric_id) {
  return MetricBuffer(shared_from_this(), metric_id);
}

MetricBuffer::MetricBuffer(std::shared_ptr<MetricsBuffer> parent, uint32_t metric_id)
    : parent_(parent), metric_id_(metric_id) {}

void MetricBuffer::LogEvent(std::vector<uint32_t> dimension_values) {
  parent_->LogEvent(metric_id_, std::move(dimension_values));
}

void MetricBuffer::LogEventCount(std::vector<uint32_t> dimension_values, uint32_t count) {
  parent_->LogEventCount(metric_id_, std::move(dimension_values), count);
}

}  // namespace cobalt