// excerpts from http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)

#define __STDC_LIMIT_MACROS
#include "TimerQueue.h"

#include "logging/Logging.h"
#include "EventLoop.h"
#include "Timer.h"
#include "TimerId.h"

#include <boost/bind.hpp>

#include <sys/timerfd.h>

namespace muduo
{
namespace detail
{

int createTimerfd()
{
  int timerfd = ::timerfd_create(CLOCK_MONOTONIC,
                                 TFD_NONBLOCK | TFD_CLOEXEC);
  if (timerfd < 0)
  {
    LOG_SYSFATAL << "Failed in timerfd_create";
  }
  return timerfd;
}

struct timespec howMuchTimeFromNow(Timestamp when)
{
  int64_t microseconds = when.microSecondsSinceEpoch()
                         - Timestamp::now().microSecondsSinceEpoch();
  if (microseconds < 100)
  {
    microseconds = 100;
  }
  struct timespec ts;
  ts.tv_sec = static_cast<time_t>(
      microseconds / Timestamp::kMicroSecondsPerSecond);
  ts.tv_nsec = static_cast<long>(
      (microseconds % Timestamp::kMicroSecondsPerSecond) * 1000);
  return ts;
}

void readTimerfd(int timerfd, Timestamp now)
{
  uint64_t howmany;
  ssize_t n = ::read(timerfd, &howmany, sizeof howmany);
  LOG_TRACE << "TimerQueue::handleRead() " << howmany << " at " << now.toString();
  if (n != sizeof howmany)
  {
    LOG_ERROR << "TimerQueue::handleRead() reads " << n << " bytes instead of 8";
  }
}

void resetTimerfd(int timerfd, Timestamp expiration)
{
  // wake up loop by timerfd_settime()
  struct itimerspec newValue;
  struct itimerspec oldValue;
  bzero(&newValue, sizeof newValue);
  bzero(&oldValue, sizeof oldValue);
  newValue.it_value = howMuchTimeFromNow(expiration);
  int ret = ::timerfd_settime(timerfd, 0, &newValue, &oldValue);
  if (ret)
  {
    LOG_SYSERR << "timerfd_settime()";
  }
}

}
}

using namespace muduo;
using namespace muduo::detail;

TimerQueue::TimerQueue(EventLoop* loop)
  : loop_(loop),
    timerfd_(createTimerfd()),
    timerfdChannel_(loop, timerfd_),
    timers_()
{
  timerfdChannel_.setReadCallback(
      boost::bind(&TimerQueue::handleRead, this));
  // we are always reading the timerfd, we disarm it with timerfd_settime.
  timerfdChannel_.enableReading();
}

TimerQueue::~TimerQueue()
{
  ::close(timerfd_);
  // do not remove channel, since we're in EventLoop::dtor();
  for (TimerList::iterator it = timers_.begin();
      it != timers_.end(); ++it)
  {
    delete it->second;
  }
}

TimerId TimerQueue::addTimer(const TimerCallback& cb,
                             Timestamp when,
                             double interval)
{
  Timer* timer = new Timer(cb, when, interval);
  loop_->runInLoop(
      boost::bind(&TimerQueue::addTimerInLoop, this, timer));
  return TimerId(timer);
}

void TimerQueue::addTimerInLoop(Timer* timer)
{
  loop_->assertInLoopThread();
  bool earliestChanged = insert(timer);

  if (earliestChanged)
  {
    resetTimerfd(timerfd_, timer->expiration());
  }
}

void TimerQueue::handleRead()
{
  loop_->assertInLoopThread();
  Timestamp now(Timestamp::now());
  readTimerfd(timerfd_, now);

  std::vector<Entry> expired = getExpired(now);

  // safe to callback outside critical section
  for (std::vector<Entry>::iterator it = expired.begin();
      it != expired.end(); ++it)
  {
    it->second->run();
  }

  reset(expired, now);
}

std::vector<TimerQueue::Entry> TimerQueue::getExpired(Timestamp now)
{
  std::vector<Entry> expired;
  Entry sentry = std::make_pair(now, reinterpret_cast<Timer*>(UINTPTR_MAX));
  TimerList::iterator it = timers_.lower_bound(sentry);
  assert(it == timers_.end() || now < it->first);
  std::copy(timers_.begin(), it, back_inserter(expired));
  timers_.erase(timers_.begin(), it);

  return expired;
}

void TimerQueue::reset(const std::vector<Entry>& expired, Timestamp now)
{
  Timestamp nextExpire;

  for (std::vector<Entry>::const_iterator it = expired.begin();
      it != expired.end(); ++it)
  {
    if (it->second->repeat())
    {
      it->second->restart(now);
      insert(it->second);
    }
    else
    {
      // FIXME move to a free list
      delete it->second;
    }
  }

  if (!timers_.empty())
  {
    nextExpire = timers_.begin()->second->expiration();
  }

  if (nextExpire.valid())
  {
    resetTimerfd(timerfd_, nextExpire);
  }
}

bool TimerQueue::insert(Timer* timer)
{
  bool earliestChanged = false;
  Timestamp when = timer->expiration();
  TimerList::iterator it = timers_.begin();
  if (it == timers_.end() || when < it->first)
  {
    earliestChanged = true;
  }
  std::pair<TimerList::iterator, bool> result =
          timers_.insert(std::make_pair(when, timer));
  assert(result.second);
  return earliestChanged;
}