/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * 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 <folly/io/async/VirtualEventBase.h>

namespace folly {

VirtualEventBase::VirtualEventBase(EventBase& evb)
    : evb_(getKeepAliveToken(evb)) {}

std::future<void> VirtualEventBase::destroy() {
  evb_->runInEventBaseThread([this] { loopKeepAlive_.reset(); });

  return std::move(destroyFuture_);
}

void VirtualEventBase::destroyImpl() noexcept {
  try {
    {
      // After destroyPromise_ is posted this object may be destroyed, so make
      // sure we release EventBase's keep-alive token before that.
      SCOPE_EXIT { evb_.reset(); };

      clearCobTimeouts();

      while (!onDestructionCallbacks_.rlock()->empty()) {
        // To avoid potential deadlock, do not hold the mutex while invoking
        // user-supplied callbacks.
        EventBase::OnDestructionCallback::List callbacks;
        onDestructionCallbacks_.swap(callbacks);
        while (!callbacks.empty()) {
          auto& callback = callbacks.front();
          callbacks.pop_front();
          callback.runCallback();
        }
      }
    }

    destroyPromise_.set_value();
  } catch (...) {
    destroyPromise_.set_exception(std::current_exception());
  }
}

VirtualEventBase::~VirtualEventBase() {
  if (!destroyFuture_.valid()) {
    return;
  }
  CHECK(!evb_->inRunningEventBaseThread());
  destroy().get();
}

void VirtualEventBase::runOnDestruction(
    EventBase::OnDestructionCallback& callback) {
  callback.schedule(
      [this](auto& cb) { onDestructionCallbacks_.wlock()->push_back(cb); },
      [this](auto& cb) {
        onDestructionCallbacks_.withWLock(
            [&](auto& list) { list.erase(list.iterator_to(cb)); });
      });
}

void VirtualEventBase::runOnDestruction(Func f) {
  auto* callback = new EventBase::FunctionOnDestructionCallback(std::move(f));
  runOnDestruction(*callback);
}

} // namespace folly
