// Copyright 2013 the V8 project 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/libplatform/default-platform.h"

#include <algorithm>
#include <queue>

#include "src/base/logging.h"
#include "src/base/platform/platform.h"
#include "src/base/platform/time.h"
#include "src/base/sys-info.h"
#include "src/libplatform/worker-thread.h"

namespace v8 {
namespace platform {


v8::Platform* CreateDefaultPlatform(int thread_pool_size) {
  DefaultPlatform* platform = new DefaultPlatform();
  platform->SetThreadPoolSize(thread_pool_size);
  platform->EnsureInitialized();
  return platform;
}


bool PumpMessageLoop(v8::Platform* platform, v8::Isolate* isolate) {
  return reinterpret_cast<DefaultPlatform*>(platform)->PumpMessageLoop(isolate);
}

const int DefaultPlatform::kMaxThreadPoolSize = 8;

DefaultPlatform::DefaultPlatform()
    : initialized_(false), thread_pool_size_(0) {}


DefaultPlatform::~DefaultPlatform() {
  base::LockGuard<base::Mutex> guard(&lock_);
  queue_.Terminate();
  if (initialized_) {
    for (auto i = thread_pool_.begin(); i != thread_pool_.end(); ++i) {
      delete *i;
    }
  }
  for (auto i = main_thread_queue_.begin(); i != main_thread_queue_.end();
       ++i) {
    while (!i->second.empty()) {
      delete i->second.front();
      i->second.pop();
    }
  }
  for (auto i = main_thread_delayed_queue_.begin();
       i != main_thread_delayed_queue_.end(); ++i) {
    while (!i->second.empty()) {
      delete i->second.top().second;
      i->second.pop();
    }
  }
}


void DefaultPlatform::SetThreadPoolSize(int thread_pool_size) {
  base::LockGuard<base::Mutex> guard(&lock_);
  DCHECK(thread_pool_size >= 0);
  if (thread_pool_size < 1) {
    thread_pool_size = base::SysInfo::NumberOfProcessors() - 1;
  }
  thread_pool_size_ =
      std::max(std::min(thread_pool_size, kMaxThreadPoolSize), 1);
}


void DefaultPlatform::EnsureInitialized() {
  base::LockGuard<base::Mutex> guard(&lock_);
  if (initialized_) return;
  initialized_ = true;

  for (int i = 0; i < thread_pool_size_; ++i)
    thread_pool_.push_back(new WorkerThread(&queue_));
}


Task* DefaultPlatform::PopTaskInMainThreadQueue(v8::Isolate* isolate) {
  auto it = main_thread_queue_.find(isolate);
  if (it == main_thread_queue_.end() || it->second.empty()) {
    return NULL;
  }
  Task* task = it->second.front();
  it->second.pop();
  return task;
}


Task* DefaultPlatform::PopTaskInMainThreadDelayedQueue(v8::Isolate* isolate) {
  auto it = main_thread_delayed_queue_.find(isolate);
  if (it == main_thread_delayed_queue_.end() || it->second.empty()) {
    return NULL;
  }
  double now = MonotonicallyIncreasingTime();
  std::pair<double, Task*> deadline_and_task = it->second.top();
  if (deadline_and_task.first > now) {
    return NULL;
  }
  it->second.pop();
  return deadline_and_task.second;
}


bool DefaultPlatform::PumpMessageLoop(v8::Isolate* isolate) {
  Task* task = NULL;
  {
    base::LockGuard<base::Mutex> guard(&lock_);

    // Move delayed tasks that hit their deadline to the main queue.
    task = PopTaskInMainThreadDelayedQueue(isolate);
    while (task != NULL) {
      main_thread_queue_[isolate].push(task);
      task = PopTaskInMainThreadDelayedQueue(isolate);
    }

    task = PopTaskInMainThreadQueue(isolate);

    if (task == NULL) {
      return false;
    }
  }
  task->Run();
  delete task;
  return true;
}


void DefaultPlatform::CallOnBackgroundThread(Task *task,
                                             ExpectedRuntime expected_runtime) {
  EnsureInitialized();
  queue_.Append(task);
}


void DefaultPlatform::CallOnForegroundThread(v8::Isolate* isolate, Task* task) {
  base::LockGuard<base::Mutex> guard(&lock_);
  main_thread_queue_[isolate].push(task);
}


void DefaultPlatform::CallDelayedOnForegroundThread(Isolate* isolate,
                                                    Task* task,
                                                    double delay_in_seconds) {
  base::LockGuard<base::Mutex> guard(&lock_);
  double deadline = MonotonicallyIncreasingTime() + delay_in_seconds;
  main_thread_delayed_queue_[isolate].push(std::make_pair(deadline, task));
}


void DefaultPlatform::CallIdleOnForegroundThread(Isolate* isolate,
                                                 IdleTask* task) {
  UNREACHABLE();
}


bool DefaultPlatform::IdleTasksEnabled(Isolate* isolate) { return false; }


double DefaultPlatform::MonotonicallyIncreasingTime() {
  return base::TimeTicks::HighResolutionNow().ToInternalValue() /
         static_cast<double>(base::Time::kMicrosecondsPerSecond);
}


uint64_t DefaultPlatform::AddTraceEvent(
    char phase, const uint8_t* category_enabled_flag, const char* name,
    const char* scope, uint64_t id, uint64_t bind_id, int num_args,
    const char** arg_names, const uint8_t* arg_types,
    const uint64_t* arg_values, unsigned int flags) {
  return 0;
}


void DefaultPlatform::UpdateTraceEventDuration(
    const uint8_t* category_enabled_flag, const char* name, uint64_t handle) {}


const uint8_t* DefaultPlatform::GetCategoryGroupEnabled(const char* name) {
  static uint8_t no = 0;
  return &no;
}


const char* DefaultPlatform::GetCategoryGroupName(
    const uint8_t* category_enabled_flag) {
  static const char dummy[] = "dummy";
  return dummy;
}


size_t DefaultPlatform::NumberOfAvailableBackgroundThreads() {
  return static_cast<size_t>(thread_pool_size_);
}

}  // namespace platform
}  // namespace v8