// 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

/*! \file paddle_api.h
 */

/*! \mainpage Paddle Inference APIs
 * \section intro_sec Introduction
 * The Paddle inference library aims to offer an high performance inference SDK
 * for Paddle users.
 */

#include <cassert>
#include <memory>
#include <string>
#include <vector>

/*! \namespace paddle
 */
namespace paddle {

/** paddle data type.
 */
enum PaddleDType {
  FLOAT32,
  INT64,
  // TODO(Superjomn) support more data types if needed.
};

/**
 * \brief Memory manager for `PaddleTensor`.
 *
 * The PaddleBuf holds a buffer for data input or output. The memory can be
 * allocated by user or by PaddleBuf itself, but in any case, the PaddleBuf
 * should be reused for better performance.
 *
 * For user allocated memory, the following API can be used:
 * - PaddleBuf(void* data, size_t length) to set an external memory by
 * specifying the memory address and length.
 * - Reset(void* data, size_t length) to reset the PaddleBuf with an external
 *memory.
 * ATTENTION, for user allocated memory, deallocation should be done by users
 *externally after the program finished. The PaddleBuf won't do any allocation
 *or deallocation.
 *
 * To have the PaddleBuf allocate and manage the memory:
 * - PaddleBuf(size_t length) will allocate a memory of size `length`.
 * - Resize(size_t length) resize the memory to no less than `length`, ATTENTION
 *  if the allocated memory is larger than `length`, nothing will done.
 *
 * Usage:
 *
 * Let PaddleBuf manage the memory internally.
 * \code{cpp}
 * const int num_elements = 128;
 * PaddleBuf buf(num_elements * sizeof(float));
 * \endcode
 *
 * Or
 * \code{cpp}
 * PaddleBuf buf;
 * buf.Resize(num_elements * sizeof(float));
 * \endcode
 * Works the exactly the same.
 *
 * One can also make the `PaddleBuf` use the external memory.
 * \code{cpp}
 * PaddleBuf buf;
 * void* external_memory = new float[num_elements];
 * buf.Reset(external_memory, num_elements*sizeof(float));
 * ...
 * delete[] external_memory; // manage the memory lifetime outside.
 * \endcode
 */
class PaddleBuf {
 public:
  /** PaddleBuf allocate memory internally, and manage it.
   */
  explicit PaddleBuf(size_t length)
      : data_(new char[length]), length_(length), memory_owned_(true) {}
  /** Set external memory, the PaddleBuf won't manage it.
   */
  PaddleBuf(void* data, size_t length)
      : data_(data), length_(length), memory_owned_{false} {}
  /** Copy only available when memory is managed externally.
   */
  explicit PaddleBuf(const PaddleBuf&);

  /** Resize the memory.
   */
  void Resize(size_t length);
  /** Reset to external memory, with address and length set.
   */
  void Reset(void* data, size_t length);
  /** Tell whether the buffer is empty.
   */
  bool empty() const { return length_ == 0; }
  /** Get the data's memory address.
   */
  void* data() const { return data_; }
  /** Get the memory length.
   */
  size_t length() const { return length_; }

  ~PaddleBuf() { Free(); }
  PaddleBuf& operator=(const PaddleBuf&);
  PaddleBuf& operator=(PaddleBuf&&);
  PaddleBuf() = default;
  PaddleBuf(PaddleBuf&& other);

 private:
  void Free();
  void* data_{nullptr};  // pointer to the data memory.
  size_t length_{0};     // number of memory bytes.
  bool memory_owned_{true};
};

/** Basic input and output data structure for PaddlePredictor.
 */
struct PaddleTensor {
  PaddleTensor() = default;
  std::string name;  // variable name.
  std::vector<int> shape;
  PaddleBuf data;  // blob of data.
  PaddleDType dtype;
  std::vector<std::vector<size_t>> lod;  // Tensor+LoD equals LoDTensor
};

enum class PaddlePlace { kUNK = -1, kCPU, kGPU };

/** Tensor without copy, currently only supports `AnalysisPredictor`.
 */
class ZeroCopyTensor {
 public:
  void Reshape(const std::vector<int>& shape);

  /** Get the memory in CPU or GPU with specific data type, should Reshape first
   * to tell the data size.
   * Once can directly call this data to feed the data.
   * This is for write the input tensor.
   */
  template <typename T>
  T* mutable_data(PaddlePlace place);
  /** Get the memory directly, will return the place and element size by
   * pointer.
   * This is for reading the output tensor.
   */
  template <typename T>
  T* data(PaddlePlace* place, int* size) const;

  std::vector<int64_t> shape() const;

  void SetLoD(const std::vector<std::vector<size_t>>& x);
  std::vector<std::vector<size_t>> lod() const;
  const std::string& name() const { return name_; }

 protected:
  explicit ZeroCopyTensor(void* scope) : scope_{scope} {}
  void SetName(const std::string& name) { name_ = name; }
  void* FindTensor() const;

 private:
  std::string name_;
  bool input_or_output_;
  friend class AnalysisPredictor;
  void* scope_{nullptr};
  // The corresponding tensor pointer inside Paddle workspace is cached for
  // performance.
  mutable void* tensor_{nullptr};
};

/** A simple Inference API for Paddle.
 */
class PaddlePredictor {
 public:
  struct Config;
  PaddlePredictor() = default;
  PaddlePredictor(const PaddlePredictor&) = delete;
  PaddlePredictor& operator=(const PaddlePredictor&) = delete;

  /** Predict an record.
   * The caller should be responsible for allocating and releasing the memory of
   * `inputs`. `inputs` should be available until Run returns. Caller should be
   * responsible for the output tensor's buffer, either allocated or passed from
   * outside.
   */
  virtual bool Run(const std::vector<PaddleTensor>& inputs,
                   std::vector<PaddleTensor>* output_data,
                   int batch_size = -1) = 0;

  /** \brief Get a mutable tensor directly.
   *
   * NOTE Only works in AnalysisPredictor.
   *
   * One can also use this to modify any temporary variable related tensors in
   * the predictor.
   *
   */
  virtual std::unique_ptr<ZeroCopyTensor> GetInputTensor(
      const std::string& name) {
    return nullptr;
  }
  /**
   * \brief Get an immutable tensor without copy.
   *
   * NOTE Only works in AnalysisPredictor.
   * One can use this API to get any temporary tensors in the predictor and
   * read it.
   */
  virtual std::unique_ptr<ZeroCopyTensor> GetOutputTensor(
      const std::string& name) {
    return nullptr;
  }
  /**
   * \brief Run the predictor with zero-copied inputs and outputs.
   *
   * NOTE Only works in AnalysisPredictor.
   *
   * This will save the IO copy for transfering inputs and outputs to predictor
   * workspace and get some performance improvement.
   * To use it, one should call the `AnalysisConfig.SwitchUseFeedFetchOp(true)`
   * and then use the `GetInputTensor` and `GetOutputTensor` to directly write
   * or read the input/output tensors.
   */
  virtual bool ZeroCopyRun() { return false; }

  /** Clone a predictor that share the model weights, the Cloned predictor
   * should be thread-safe.
   */
  virtual std::unique_ptr<PaddlePredictor> Clone() = 0;

  /** Destroy the Predictor.
   */
  virtual ~PaddlePredictor() = default;

  /** \brief Get the serialized model program that executes in inference phase.
   * Its data type is ProgramDesc, which is a protobuf message.
   */
  virtual std::string GetSerializedProgram() const {
    assert(false);  // Force raise error.
    return "NotImplemented";
  }

  /** The common configs for all the predictors.
   */
  struct Config {
    std::string model_dir; /*!< path to the model directory. */
  };
};

struct NativeConfig : public PaddlePredictor::Config {
  // GPU related fields.
  bool use_gpu{false};
  int device{0};
  float fraction_of_gpu_memory{
      -1.f}; /*!< Change to a float in (0,1] if needed. */

  // Specify the exact path of program and parameter files.
  std::string prog_file;
  std::string param_file;

  /** Specify the variable's name of each input if input tensors don't follow
   * the
   * `feeds` and `fetches` of the phase `save_inference_model`.
   */
  bool specify_input_name{false};

  /** Set and get the number of cpu math library threads.
   */
  void SetCpuMathLibraryNumThreads(int cpu_math_library_num_threads) {
    cpu_math_library_num_threads_ = cpu_math_library_num_threads;
  }
  int cpu_math_library_num_threads() const {
    return cpu_math_library_num_threads_;
  }

 protected:
  // number of cpu math library (such as MKL, OpenBlas) threads for each
  // instance.
  int cpu_math_library_num_threads_{1};
};

/*! \fn std::unique_ptr<PaddlePredictor> CreatePaddlePredictor(const ConfigT&
 * config);
 *
 * \brief A factory to help create different predictors.
 *
 * Usage:
 *
 * \code{.cpp}
 * NativeConfig config;
 * ... // change the configs.
 * auto native_predictor = CreatePaddlePredictor(config);
 * \endcode
 *
 * FOR EXTENSION DEVELOPER:
 * Different predictors are designated by config type. Similar configs can be
 * merged, but there shouldn't be a huge config containing different fields for
 * more than one kind of predictors.
 */
template <typename ConfigT>
std::unique_ptr<PaddlePredictor> CreatePaddlePredictor(const ConfigT& config);

/** NOTE The following APIs are too trivial, we will discard it in the following
 * versions.
 */
enum class PaddleEngineKind {
  kNative = 0,        /*!< Use the native Fluid facility. */
  kAutoMixedTensorRT, /*!< Automatically mix Fluid with TensorRT. */
  kAnalysis,          /*!< More optimization. */
  kAnakin             /*!< Use Anakin for inference, not mature yet. */
};

template <typename ConfigT, PaddleEngineKind engine>
std::unique_ptr<PaddlePredictor> CreatePaddlePredictor(const ConfigT& config);

int PaddleDtypeSize(PaddleDType dtype);

std::string get_version();

}  // namespace paddle