/*
 * Copyright (c) Facebook, Inc. and its 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.
 */

/*
 *  This file serves as a helper for bridging folly fibers and python
 *  asyncio.future.
 */

#pragma once

#include <Python.h>
#include <folly/Function.h>
#include <folly/fibers/FiberManagerInternal.h>

namespace folly {
namespace python {

// Must be called from main context
folly::fibers::FiberManager* getFiberManager(
    const folly::fibers::FiberManager::Options& opts = {});

/**
 * Helper function with similar callback/userData parameters as bridgeFuture.
 * This can be convenient in code that calls both (notably our tests),
 * but most callsites should directly use getFiberManager().
 */
template <typename T>
void bridgeFibers(
    folly::Function<T()>&& function,
    folly::Function<void(folly::Try<T>&&, PyObject*)> callback,
    PyObject* userData) {
  auto* fiberManager = getFiberManager();
  // We are handing over a pointer to a python object to c++ and need
  // to make sure it isn't removed by python in that time.
  Py_INCREF(userData);
  auto guard = folly::makeGuard([=] { Py_DECREF(userData); });
  fiberManager->addTask([function = std::move(function),
                         callback = std::move(callback),
                         userData,
                         guard = std::move(guard)]() mutable {
    // This will run from inside the gil, called by the asyncio add_reader
    auto res = folly::makeTryWith([&] { return function(); });
    callback(std::move(res), userData);
    // guard goes out of scope here, and its stored function is called
  });
}

} // namespace python
} // namespace folly
