// Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
//
// 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 "paddle/fluid/operators/reader/py_reader.h"

namespace paddle {
namespace operators {
namespace reader {

PyReader::PyReader(const std::shared_ptr<LoDTensorBlockingQueue>& queue)
    : framework::FileReader() {
  PADDLE_ENFORCE(queue != nullptr, "LoDTensorBlockingQueue must not be null");
  queue_ = queue;
}

void PyReader::ReadNext(std::vector<framework::LoDTensor>* out) {
  bool success;
  *out = queue_->Pop(&success);
  if (!success) out->clear();
}

PyReader::~PyReader() { queue_->Close(); }

void PyReader::Shutdown() { queue_->Close(); }

void PyReader::Start() { queue_->ReOpen(); }

MultiQueuePyReader::MultiQueuePyReader(
    const std::vector<std::shared_ptr<LoDTensorBlockingQueue>>& queues)
    : queues_(queues) {
  PADDLE_ENFORCE(!queues_.empty());
  for (auto& q : queues_) {
    PADDLE_ENFORCE_NOT_NULL(q);
  }
}

void MultiQueuePyReader::ReadNext(std::vector<framework::LoDTensor>* out) {
  auto idx = read_out_idx_.fetch_add(1) % queues_.size();
  for (size_t i = 0; i < queues_.size(); ++i) {
    *out = queues_[idx]->Pop();
    if (!out->empty()) return;
    idx = (idx + 1) % queues_.size();
  }
}

MultiQueuePyReader::~MultiQueuePyReader() {
  for (auto& q : queues_) {
    q->Close();
  }
}

void MultiQueuePyReader::Shutdown() {
  for (auto& q : queues_) {
    q->Close();
  }
  read_out_idx_.store(0, std::memory_order::memory_order_seq_cst);
}

void MultiQueuePyReader::Start() {
  for (auto& q : queues_) {
    q->ReOpen();
  }
}

}  // namespace reader
}  // namespace operators
}  // namespace paddle