text: /*
   * 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.
   */
  
  #include <folly/Benchmark.h>
  #include <folly/Portability.h>
  
  #include <folly/experimental/coro/BlockingWait.h>
  #include <folly/experimental/coro/CurrentExecutor.h>
  #include <folly/experimental/coro/Task.h>
  
  #include <memory>
  
  #if FOLLY_HAS_COROUTINES
  
  BENCHMARK(SingleVoidSynchronousTaskInLoop, iters) {
    folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
      auto completeSynchronously = []() -> folly::coro::Task<void> { co_return; };
      for (std::size_t i = 0; i < iters; ++i) {
        co_await completeSynchronously();
      }
    }());
  }
  
  BENCHMARK(AsyncTaskInLoop, iters) {
    folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
      auto asyncReschedule = []() -> folly::coro::Task<void> {
        co_await folly::coro::co_reschedule_on_current_executor;
      };
      for (std::size_t i = 0; i < iters; ++i) {
        co_await asyncReschedule();
      }
    }());
  }
  
  BENCHMARK(AsyncRescheduleNoTask, iters) {
    folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
      for (std::size_t i = 0; i < iters; ++i) {
        co_await folly::coro::co_reschedule_on_current_executor;
      }
    }());
  }
  
  class Base {
   public:
    virtual ~Base() {}
  
    virtual folly::coro::Task<int> virtualMethod() = 0;
  };
  
  template <int Tag>
  class Derived : public Base {
   public:
    FOLLY_NOINLINE
    folly::coro::Task<int> virtualMethod() override { co_return Tag; }
  };
  
  FOLLY_NOINLINE
  static std::unique_ptr<Base> makeBase(size_t iters) {
    switch (iters % 3) {
      case 0:
        return std::make_unique<Derived<1>>();
      case 1:
        return std::make_unique<Derived<2>>();
      default:
        return std::make_unique<Derived<3>>();
    }
  }
  
  BENCHMARK(VirtualTaskMethod, iters) {
    folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
      auto base = makeBase(iters);
      size_t count = 0;
      for (std::size_t i = 0; i < iters; ++i) {
        count += co_await base->virtualMethod();
      }
      if (count != iters * ((iters % 3) + 1)) {
        std::terminate();
      }
    }());
  }
  
  template <size_t N>
  static folly::coro::Task<void> staticNestedCalls() {
    if constexpr (N > 0) {
      co_await staticNestedCalls<N - 1>();
    }
    co_return;
  }
  
  template <size_t N>
  static void benchStaticNestedCalls(size_t iters) {
    folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
      for (size_t i = 0; i < iters; ++i) {
        co_await staticNestedCalls<N>();
      }
    }());
  }
  
  BENCHMARK(StaticNestedCalls3, iters) {
    benchStaticNestedCalls<3>(iters / 3);
  }
  
  BENCHMARK(StaticNestedCalls10, iters) {
    benchStaticNestedCalls<10>(iters / 10);
  }
  
  static folly::coro::Task<void> nestedCalls(size_t depth) {
    if (depth > 0) {
      co_await nestedCalls(depth - 1);
    }
    co_return;
  }
  
  static void benchNestedCalls(size_t depth, size_t iters) {
    folly::coro::blockingWait([depth, iters]() -> folly::coro::Task<void> {
      for (size_t i = 0; i < iters; ++i) {
        co_await nestedCalls(depth);
      }
    }());
  }
  
  BENCHMARK(NestedCalls3, iters) {
    benchNestedCalls(3, iters / 3);
  }
  
  BENCHMARK(NestedCalls10, iters) {
    benchNestedCalls(10, iters / 10);
  }
  
  static void benchNestedCallsWithCancellation(size_t depth, size_t iters) {
    folly::CancellationSource cancelSource;
    folly::coro::blockingWait(folly::coro::co_withCancellation(
        cancelSource.getToken(), [depth, iters]() -> folly::coro::Task<void> {
          for (size_t i = 0; i < iters; ++i) {
            co_await nestedCalls(depth);
          }
        }()));
  }
  
  BENCHMARK(NestedCallsWithCancellation3, iters) {
    benchNestedCallsWithCancellation(3, iters / 3);
  }
  
  BENCHMARK(NestedCallsWithCancellation10, iters) {
    benchNestedCallsWithCancellation(10, iters / 10);
  }
  
  #endif // FOLLY_HAS_COROUTINES
  
  int main(int argc, char** argv) {
    gflags::ParseCommandLineFlags(&argc, &argv, true);
    folly::runBenchmarks();
    return 0;
  }
  