// Copyright 2015 The Cobalt Authors. All Rights Reserved.
//
// 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 "cobalt/dom/window_timers.h"

#include <limits>
#include <memory>

#include "base/bind.h"
#include "base/bind_helpers.h"
#include "base/threading/sequenced_task_runner_handle.h"
#include "base/trace_event/trace_event.h"
#include "cobalt/base/application_state.h"
#include "cobalt/base/polymorphic_downcast.h"
#include "cobalt/dom/global_stats.h"
#include "nb/memory_scope.h"

namespace cobalt {
namespace dom {

int WindowTimers::TryAddNewTimer(Timer::TimerType type,
                                 const TimerCallbackArg& handler, int timeout) {
  int handle = GetFreeTimerHandle();
  DCHECK(handle);

  if (handle == 0) {  // unable to get a free timer handle
    // avoid accidentally overwriting existing timers
    return 0;
  }

  if (callbacks_active_) {
    auto* timer = new Timer(type, owner_, handler, timeout, handle, this);
    if (application_state_ != base::kApplicationStateFrozen) {
      timer->StartOrResume();
    }
    timers_[handle] = timer;
    debugger_hooks_.AsyncTaskScheduled(
        timers_[handle], type == Timer::kOneShot ? "SetTimeout" : "SetInterval",
        type == Timer::kOneShot
            ? base::DebuggerHooks::AsyncTaskFrequency::kOneshot
            : base::DebuggerHooks::AsyncTaskFrequency::kRecurring);
  } else {
    timers_[handle] = nullptr;
  }

  return handle;
}

int WindowTimers::SetTimeout(const TimerCallbackArg& handler, int timeout) {
  TRACK_MEMORY_SCOPE("DOM");
  return TryAddNewTimer(Timer::kOneShot, handler, timeout);
}

void WindowTimers::ClearTimeout(int handle) { timers_.erase(handle); }

int WindowTimers::SetInterval(const TimerCallbackArg& handler, int timeout) {
  TRACK_MEMORY_SCOPE("DOM");
  return TryAddNewTimer(Timer::kRepeating, handler, timeout);
}

void WindowTimers::ClearInterval(int handle) {
  Timers::iterator timer = timers_.find(handle);
  if (timer != timers_.end()) {
    debugger_hooks_.AsyncTaskCanceled(timer->second);
    timers_.erase(timer);
  }
}

void WindowTimers::ClearAllIntervalsAndTimeouts() {
  for (auto& timer_entry : timers_) {
    debugger_hooks_.AsyncTaskCanceled(timer_entry.second);
  }
  timers_.clear();
}

void WindowTimers::DisableCallbacks() {
  callbacks_active_ = false;
  // Immediately cancel any pending timers.
  for (auto& timer_entry : timers_) {
    debugger_hooks_.AsyncTaskCanceled(timer_entry.second);
    timer_entry.second = nullptr;
  }
}

int WindowTimers::GetFreeTimerHandle() {
  int next_timer_index = current_timer_index_;
  while (true) {
    if (next_timer_index == std::numeric_limits<int>::max()) {
      next_timer_index = 1;
    } else {
      ++next_timer_index;
    }
    if (timers_.find(next_timer_index) == timers_.end()) {
      current_timer_index_ = next_timer_index;
      return current_timer_index_;
    }
    if (next_timer_index == current_timer_index_) {
      break;
    }
  }
  DLOG(INFO) << "No available timer handle.";
  return 0;
}

void WindowTimers::RunTimerCallback(int handle) {
  TRACE_EVENT0("cobalt::dom", "WindowTimers::RunTimerCallback");
  DCHECK(callbacks_active_)
      << "All timer callbacks should have already been cancelled.";
  Timers::iterator timer = timers_.find(handle);
  DCHECK(timer != timers_.end());

  // The callback is now being run. Track it in the global stats.
  GlobalStats::GetInstance()->StartJavaScriptEvent();

  {
    // Keep a |TimerInfo| reference, so it won't be released when running the
    // callback.
    scoped_refptr<Timer> timer_info = timer->second;
    base::ScopedAsyncTask async_task(debugger_hooks_, timer_info);
    timer_info->callback_reference().value().Run();
  }

  // After running the callback, double check whether the timer is still there
  // since it might be deleted inside the callback.
  timer = timers_.find(handle);
  // If the timer is not deleted and is not running, it means it is an oneshot
  // timer and has just fired the shot, and it should be deleted now.
  if (timer != timers_.end() && !timer->second->timer()->IsRunning()) {
    debugger_hooks_.AsyncTaskCanceled(timer->second);
    timers_.erase(timer);
  }

  // The callback has finished running. Stop tracking it in the global stats.
  GlobalStats::GetInstance()->StopJavaScriptEvent();
}

void WindowTimers::SetApplicationState(base::ApplicationState state) {
  switch (state) {
    case base::kApplicationStateFrozen:
      DCHECK_EQ(application_state_, base::kApplicationStateConcealed);
      for (auto timer : timers_) {
        timer.second->Pause();
      }
      break;
    case base::kApplicationStateConcealed:
      if (application_state_ == base::kApplicationStateFrozen) {
        for (auto timer : timers_) {
          timer.second->StartOrResume();
        }
      }
      break;
    case base::kApplicationStateStopped:
    case base::kApplicationStateBlurred:
    case base::kApplicationStateStarted:
      break;
  }
  application_state_ = state;
}

WindowTimers::Timer::Timer(TimerType type, script::Wrappable* const owner,
                           const TimerCallbackArg& callback, int timeout,
                           int handle, WindowTimers* window_timers)
    : type_(type),
      callback_(owner, callback),
      timeout_(timeout),
      handle_(handle),
      window_timers_(window_timers) {}

void WindowTimers::Timer::Pause() {
  if (timer_) {
    // The desired runtime is preserved here to determine whether the timer
    // should fire immediately when resuming.
    desired_run_time_ = timer_->desired_run_time();
    timer_.reset();
  }
}

void WindowTimers::Timer::StartOrResume() {
  if (timer_ != nullptr) return;
  switch (type_) {
    case kOneShot:
      if (desired_run_time_) {
        // Adjust the new timeout for the time spent while paused.
        auto now = base::TimeTicks::Now();
        if (desired_run_time_ <= now) {
          // The previous desired run time was in the past or is right now, so
          // it should fire immediately.
          timeout_ = 0;
        } else {
          // Set the timeout to keep the same desired run time. Note that since
          // the timer uses the timeout that we request to set a new desired
          // run time from the clock, the resumed timer will likely fire
          // slightly later.
          base::TimeDelta time_delta(desired_run_time_.value() - now);
          timeout_ = static_cast<int>(time_delta.InMilliseconds());
        }
      }
      timer_ = CreateAndStart<base::OneShotTimer>();
      break;
    case kRepeating:
      timer_ = CreateAndStart<base::RepeatingTimer>();
      if (timeout_ && desired_run_time_ &&
          desired_run_time_ < base::TimeTicks::Now()) {
        // The timer was paused and the desired run time is in the past.
        // Call the callback once before continuing the repeating timer.
        base::SequencedTaskRunnerHandle::Get()->PostTask(
            FROM_HERE, base::Bind(&WindowTimers::RunTimerCallback,
                                  base::Unretained(window_timers_), handle_));
      }
      break;
  }
}

template <class TimerClass>
std::unique_ptr<base::internal::TimerBase>
WindowTimers::Timer::CreateAndStart() {
  auto* timer = new TimerClass();
  timer->Start(FROM_HERE, base::TimeDelta::FromMilliseconds(timeout_),
               base::Bind(&WindowTimers::RunTimerCallback,
                          base::Unretained(window_timers_), handle_));
  return std::unique_ptr<base::internal::TimerBase>(timer);
}

}  // namespace dom
}  // namespace cobalt