// Copyright 2019 The MediaPipe Authors.
//
// 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.

#ifndef MEDIAPIPE_FRAMEWORK_OUTPUT_STREAM_POLLER_H_
#define MEDIAPIPE_FRAMEWORK_OUTPUT_STREAM_POLLER_H_

#include <memory>

#include "mediapipe/framework/graph_output_stream.h"

namespace mediapipe {

// The public interface of output stream poller.
class OutputStreamPoller {
 public:
  OutputStreamPoller(const OutputStreamPoller&) = delete;
  OutputStreamPoller& operator=(const OutputStreamPoller&) = delete;
  OutputStreamPoller(OutputStreamPoller&&) = default;
  // Move assignment needs to be explicitly defaulted to allow ASSIGN_OR_RETURN
  // on `StatusOr<OutputStreamPoller>`.
  OutputStreamPoller& operator=(OutputStreamPoller&&) = default;

  // Resets OutputStramPollerImpl and cleans the internal packet queue.
  void Reset() {
    auto poller = internal_poller_impl_.lock();
    CHECK(poller) << "OutputStreamPollerImpl is already destroyed.";
    poller->Reset();
  }

  // Gets the next packet (block until it is available or the stream is
  // done).  Returns true if successful.
  ABSL_MUST_USE_RESULT bool Next(Packet* packet) {
    auto poller = internal_poller_impl_.lock();
    if (!poller) {
      return false;
    }
    return poller->Next(packet);
  }

  void SetMaxQueueSize(int queue_size) {
    auto poller = internal_poller_impl_.lock();
    CHECK(poller) << "OutputStreamPollerImpl is already destroyed.";
    return poller->SetMaxQueueSize(queue_size);
  }

  // Returns the number of packets in the queue.
  int QueueSize() {
    auto poller = internal_poller_impl_.lock();
    CHECK(poller) << "OutputStreamPollerImpl is already destroyed.";
    return poller->QueueSize();
  }

 private:
  OutputStreamPoller(
      std::shared_ptr<internal::OutputStreamPollerImpl> internal_poller_impl)
      : internal_poller_impl_(internal_poller_impl) {}

  std::weak_ptr<internal::OutputStreamPollerImpl> internal_poller_impl_;

  // Friend class to connect OutputStreamPoller with
  // internal::OutputStreamPollerImpl.
  friend class CalculatorGraph;
};

}  // namespace mediapipe

#endif  // MEDIAPIPE_FRAMEWORK_OUTPUT_STREAM_POLLER_H_