#include <llarp/timer.h>
#include <atomic>
#include <condition_variable>
#include <list>
#include <map>

namespace llarp
{
  struct timer
  {
    static uint64_t
    now()
    {
      return std::chrono::duration_cast< std::chrono::milliseconds >(
                 std::chrono::steady_clock::now().time_since_epoch())
          .count();
    }

    llarp_timer_context* parent;
    void* user;
    uint64_t started;
    uint64_t timeout;
    llarp_timer_handler_func func;
    uint32_t id;

    timer(llarp_timer_context* ctx = nullptr, uint64_t ms = 0,
          void* _user = nullptr, llarp_timer_handler_func _func = nullptr,
          uint32_t _id = 0)
        : parent(ctx)
        , user(_user)
        , started(now())
        , timeout(ms)
        , func(_func)
        , id(_id)
    {
    }

    void
    exec();

    static void
    call(void* user)
    {
      static_cast< timer* >(user)->exec();
    }

    operator llarp_thread_job()
    {
      return {this, timer::call};
    }
  };
};  // namespace llarp

struct llarp_timer_context
{
  llarp_threadpool* threadpool;
  std::mutex timersMutex;
  std::map< uint32_t, llarp::timer > timers;
  std::mutex tickerMutex;
  std::condition_variable ticker;
  std::chrono::milliseconds nextTickLen = std::chrono::milliseconds(10);

  uint32_t ids             = 0;
  std::atomic< bool > _run = true;

  bool
  run()
  {
    return _run.load();
  }

  void
  stop()
  {
    _run.store(false);
  }

  void
  cancel(uint32_t id)
  {
    auto itr = timers.find(id);
    if(itr != timers.end())
    {
      itr->second.exec();
    }
  }

  void
  remove(uint32_t id)
  {
    std::unique_lock< std::mutex > lock(timersMutex);
    timers.erase(id);
  }

  uint32_t
  call_later(void* user, llarp_timer_handler_func func, uint64_t timeout_ms)
  {
    std::unique_lock< std::mutex > lock(timersMutex);
    uint32_t id = ++ids;
    timers[id]  = llarp::timer(this, timeout_ms, user, func, id);
    return id;
  }

  void
  cancel_all()
  {
    std::unique_lock< std::mutex > lock(timersMutex);

    std::list< uint32_t > ids;

    for(auto& item : timers)
    {
      ids.push_back(item.first);
    }

    for(auto id : ids)
    {
      cancel(id);
    }
  }
};

extern "C" {

struct llarp_timer_context*
llarp_init_timer()
{
  return new llarp_timer_context;
}

uint32_t
llarp_timer_call_later(struct llarp_timer_context* t,
                       struct llarp_timeout_job job)
{
  return t->call_later(job.user, job.handler, job.timeout);
}

void
llarp_free_timer(struct llarp_timer_context** t)
{
  if(*t)
    delete *t;
  *t = nullptr;
}

void
llarp_timer_stop(struct llarp_timer_context* t)
{
  t->stop();
  {
    std::unique_lock< std::mutex > lock(t->tickerMutex);

    auto itr = t->timers.begin();
    while(itr != t->timers.end())
    {
      // timer expired
      llarp_threadpool_queue_job(t->threadpool, itr->second);
      ++itr;
    }
  }
}

void
llarp_timer_cancel(struct llarp_timer_context* t, uint32_t id)
{
  t->cancel(id);
}

void
llarp_timer_run(struct llarp_timer_context* t, struct llarp_threadpool* pool)
{
  t->threadpool = pool;
  while(t->run())
  {
    std::unique_lock< std::mutex > lock(t->tickerMutex);
    t->ticker.wait_for(lock, t->nextTickLen);
    // we woke up
    auto now = llarp::timer::now();
    auto itr = t->timers.begin();
    while(itr != t->timers.end())
    {
      if(now - itr->second.started >= itr->second.timeout)
      {
        // timer hit
        llarp_threadpool_queue_job(pool, itr->second);
      }
      ++itr;
    }
  }
}
}

namespace llarp
{
  void
  timer::exec()
  {
    if(func)
    {
      auto ms   = now();
      auto diff = ms - started;
      if(diff >= timeout)
        func(user, timeout, 0);
      else
        func(user, timeout, diff);
    }
    if(parent)
      parent->remove(id);
  }
}