#include "common/config/ttl.h"

namespace Envoy {
namespace Config {

TtlManager::TtlManager(std::function<void(const std::vector<std::string>&)> callback,
                       Event::Dispatcher& dispatcher, TimeSource& time_source)
    : callback_(callback), dispatcher_(dispatcher), time_source_(time_source) {
  timer_ = dispatcher_.createTimer([this]() {
    ScopedTtlUpdate scoped_update(*this);

    std::vector<std::string> expired;
    last_scheduled_time_ = absl::nullopt;

    const auto now = time_source_.monotonicTime();
    auto itr = ttls_.begin();
    while (itr != ttls_.end() && itr->first <= now) {
      expired.push_back(itr->second);
      ttl_lookup_.erase(itr->second);
      itr++;
    }

    if (itr != ttls_.begin()) {
      ttls_.erase(ttls_.begin(), itr);
    }

    if (!expired.empty()) {
      callback_(expired);
    }
  });
}
void TtlManager::add(std::chrono::milliseconds ttl, const std::string& name) {
  ScopedTtlUpdate scoped_update(*this);

  clear(name);

  auto itr_and_inserted = ttls_.insert({time_source_.monotonicTime() + ttl, name});
  ttl_lookup_[name] = itr_and_inserted.first;
}

void TtlManager::clear(const std::string& name) {
  ScopedTtlUpdate scoped_update(*this);

  auto lookup_itr = ttl_lookup_.find(name);
  if (lookup_itr != ttl_lookup_.end()) {
    ttls_.erase(lookup_itr->second);
    ttl_lookup_.erase(lookup_itr);
  }
}

void TtlManager::refreshTimer() {
  // No TTLs, so just disable the timer.
  if (ttls_.empty()) {
    timer_->disableTimer();
    return;
  }

  auto next_ttl_expiry = ttls_.begin()->first;

  // The currently scheduled timer execution matches the next TTL expiry, so do nothing.
  if (timer_->enabled() && last_scheduled_time_ == next_ttl_expiry) {
    return;
  }

  auto timer_duration = std::chrono::duration_cast<std::chrono::milliseconds>(
      next_ttl_expiry - time_source_.monotonicTime());

  // The time until the next TTL changed, so reset the timer to match the new value.
  last_scheduled_time_ = next_ttl_expiry;
  timer_->enableTimer(timer_duration, nullptr);
}
} // namespace Config
} // namespace Envoy