// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

#include "kudu/util/test_graph.h"

#include <mutex>
#include <ostream>
#include <thread>
#include <utility>

#include <glog/logging.h>

#include "kudu/gutil/stringprintf.h"
#include "kudu/gutil/walltime.h"
#include "kudu/util/faststring.h"
#include "kudu/util/monotime.h"

using std::shared_ptr;
using std::string;
using std::thread;

namespace kudu {

void TimeSeries::AddValue(double val) {
  std::lock_guard<simple_spinlock> l(lock_);
  val_ += val;
}

void TimeSeries::SetValue(double val) {
  std::lock_guard<simple_spinlock> l(lock_);
  val_ = val;
}

double TimeSeries::value() const {
  std::lock_guard<simple_spinlock> l(lock_);
  return val_;
}

TimeSeriesCollector::~TimeSeriesCollector() {
  if (started_) {
    StopDumperThread();
  }
}

shared_ptr<TimeSeries> TimeSeriesCollector::GetTimeSeries(const string& key) {
  MutexLock l(series_lock_);
  SeriesMap::const_iterator it = series_map_.find(key);
  if (it != series_map_.end()) {
    return (*it).second;
  }

  auto ts(std::make_shared<TimeSeries>());
  series_map_[key] = ts;
  return ts;
}

void TimeSeriesCollector::StartDumperThread() {
  LOG(INFO) << "Starting metrics dumper";
  CHECK(!started_);
  exit_latch_.Reset(1);
  started_ = true;
  dumper_thread_ = thread([this]() { this->DumperThread(); });
}

void TimeSeriesCollector::StopDumperThread() {
  CHECK(started_);
  exit_latch_.CountDown();
  dumper_thread_.join();
  started_ = false;
}

void TimeSeriesCollector::DumperThread() {
  CHECK(started_);
  WallTime start_time = WallTime_Now();

  faststring metrics_str;
  while (true) {
    metrics_str.clear();
    metrics_str.append("metrics: ");
    BuildMetricsString(WallTime_Now() - start_time, &metrics_str);
    LOG(INFO) << metrics_str.ToString();

    // Sleep until next dump time, or return if we should exit
    if (exit_latch_.WaitFor(MonoDelta::FromMilliseconds(250))) {
      return;
    }
  }
}

void TimeSeriesCollector::BuildMetricsString(
  WallTime time_since_start, faststring* dst_buf) const {
  MutexLock l(series_lock_);

  dst_buf->append(StringPrintf("{ \"scope\": \"%s\", \"time\": %.3f",
                               scope_.c_str(), time_since_start));

  for (SeriesMap::const_reference entry : series_map_) {
    dst_buf->append(StringPrintf(", \"%s\": %.3f",
                                 entry.first.c_str(),  entry.second->value()));
  }
  dst_buf->append("}");
}

} // namespace kudu