/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * Licensed 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 <folly/experimental/ThreadedRepeatingFunctionRunner.h>

#include <iostream>

#include <folly/system/ThreadName.h>

#include <glog/logging.h>

namespace folly {

ThreadedRepeatingFunctionRunner::ThreadedRepeatingFunctionRunner() = default;

ThreadedRepeatingFunctionRunner::~ThreadedRepeatingFunctionRunner() {
  if (stopImpl()) {
    LOG(ERROR)
        << "ThreadedRepeatingFunctionRunner::stop() should already have been "
        << "called, since we are now in the Runner's destructor. This is "
        << "because it means that its threads may be accessing object state "
        << "that was already destroyed -- e.g. members that were declared "
        << "after the ThreadedRepeatingFunctionRunner.";
  }
}

void ThreadedRepeatingFunctionRunner::stop() {
  stopImpl();
}

bool ThreadedRepeatingFunctionRunner::stopImpl() {
  {
    std::unique_lock<std::mutex> lock(stopMutex_);
    if (stopping_) {
      return false; // Do nothing if stop() is called twice.
    }
    stopping_ = true;
  }
  stopCv_.notify_all();
  for (auto& t : threads_) {
    t.join();
  }
  return true;
}

void ThreadedRepeatingFunctionRunner::add(
    std::string name, RepeatingFn fn, std::chrono::milliseconds initialSleep) {
  threads_.emplace_back([name = std::move(name),
                         fn = std::move(fn),
                         initialSleep,
                         this]() mutable {
    setThreadName(name);
    executeInLoop(std::move(fn), initialSleep);
  });
}

bool ThreadedRepeatingFunctionRunner::waitFor(
    std::chrono::milliseconds duration) noexcept {
  using clock = std::chrono::steady_clock;
  const auto deadline = clock::now() + duration;
  std::unique_lock<std::mutex> lock(stopMutex_);
  stopCv_.wait_until(
      lock, deadline, [&] { return stopping_ || clock::now() > deadline; });
  return !stopping_;
}

void ThreadedRepeatingFunctionRunner::executeInLoop(
    RepeatingFn fn, std::chrono::milliseconds initialSleep) noexcept {
  auto duration = initialSleep;
  while (waitFor(duration)) {
    duration = fn();
  }
}

} // namespace folly
