// Copyright (c) 2018 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.

#pragma once

#include <cstdlib>
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
#include <unordered_map>
#include <vector>

#include "paddle/fluid/framework/reader.h"
#include "paddle/fluid/framework/threadpool.h"
#include "paddle/fluid/operators/reader/lod_tensor_blocking_queue.h"

namespace paddle {
namespace operators {
namespace reader {

enum ReaderThreadStatus { Running, Stopped };

void ReadThread(const std::vector<std::string>& file_list,
                const std::vector<std::string>& slots, int batch_size,
                int thread_id, std::vector<ReaderThreadStatus>* thread_status,
                std::shared_ptr<LoDTensorBlockingQueue> queue);

class CTRReader : public framework::FileReader {
 public:
  explicit CTRReader(const std::shared_ptr<LoDTensorBlockingQueue>& queue,
                     int batch_size, int thread_num,
                     const std::vector<std::string>& slots,
                     const std::vector<std::string>& file_list)
      : batch_size_(batch_size), slots_(slots), file_list_(file_list) {
    PADDLE_ENFORCE(queue != nullptr, "LoDTensorBlockingQueue must not be null");
    PADDLE_ENFORCE_GT(file_list.size(), 0, "file list should not be empty");
    thread_num_ =
        file_list_.size() > thread_num_ ? thread_num_ : file_list_.size();
    queue_ = queue;
    SplitFiles();
    for (int i = 0; i < thread_num; ++i) {
      read_thread_status_.push_back(Stopped);
    }
  }

  ~CTRReader() { queue_->Close(); }

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

  void Shutdown() override {
    VLOG(3) << "Shutdown reader";
    for (auto& read_thread : read_threads_) {
      read_thread->join();
    }
    read_threads_.clear();
    queue_->Close();
  }

  void Start() override {
    VLOG(3) << "Start reader";
    queue_->ReOpen();
    for (int thread_id = 0; thread_id < file_groups_.size(); thread_id++) {
      read_threads_.emplace_back(new std::thread(
          std::bind(&ReadThread, file_groups_[thread_id], slots_, batch_size_,
                    thread_id, &read_thread_status_, queue_)));
    }
  }

 private:
  void SplitFiles() {
    file_groups_.resize(thread_num_);
    for (int i = 0; i < file_list_.size(); ++i) {
      file_groups_[i % thread_num_].push_back(file_list_[i]);
    }
  }

 private:
  int thread_num_;
  const int batch_size_;
  const std::vector<std::string> slots_;
  const std::vector<std::string> file_list_;
  std::shared_ptr<LoDTensorBlockingQueue> queue_;
  std::vector<std::unique_ptr<std::thread>> read_threads_;
  std::vector<ReaderThreadStatus> read_thread_status_;
  std::vector<std::vector<std::string>> file_groups_;
};

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