//===- TFUtils.cpp - tensorflow evaluation utilities ----------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements utilities for interfacing with tensorflow C APIs.
//
//===----------------------------------------------------------------------===//
#include "llvm/Config/config.h"
#if defined(LLVM_HAVE_TF_API)

#include "llvm/ADT/Twine.h"
#include "llvm/Analysis/Utils/TFUtils.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/JSON.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/raw_ostream.h"

#include "tensorflow/c/c_api.h"
#include "tensorflow/c/c_api_experimental.h"

#include <cassert>
#include <numeric>

using namespace llvm;

namespace {

using TFGraphPtr = std::unique_ptr<TF_Graph, decltype(&TF_DeleteGraph)>;
using TFSessionOptionsPtr =
    std::unique_ptr<TF_SessionOptions, decltype(&TF_DeleteSessionOptions)>;
using TFStatusPtr = std::unique_ptr<TF_Status, decltype(&TF_DeleteStatus)>;

struct TFInitializer {
  TFInitializer() {
    assert(!IsInitialized && "TFInitialized should be called only once");
    int Argc = 1;
    const char *Name = "";
    const char **NamePtr = &Name;
    TF_InitMain(Name, &Argc, const_cast<char ***>(&NamePtr));
    IsInitialized = true;
  }
  bool IsInitialized = false;
};

llvm::ManagedStatic<TFInitializer> TFLibInitializer;

bool ensureInitTF() { return TFLibInitializer->IsInitialized; }

TFGraphPtr createTFGraph() {
  return TFGraphPtr(TF_NewGraph(), &TF_DeleteGraph);
}

TFStatusPtr createTFStatus() {
  return TFStatusPtr(TF_NewStatus(), &TF_DeleteStatus);
}

TFSessionOptionsPtr createTFSessionOptions() {
  return TFSessionOptionsPtr(TF_NewSessionOptions(), &TF_DeleteSessionOptions);
}
} // namespace

namespace llvm {
class EvaluationResultImpl {
public:
  EvaluationResultImpl(size_t OutputSize)
      : OutputSize(OutputSize), Output(OutputSize){};

  ~EvaluationResultImpl() {
    for (auto *P : Output)
      if (P)
        TF_DeleteTensor(P);
  }

  EvaluationResultImpl(const EvaluationResultImpl &) = delete;
  EvaluationResultImpl(EvaluationResultImpl &&Other) = delete;
  std::vector<TF_Tensor *> &getOutput() { return Output; }

private:
  const size_t OutputSize;
  std::vector<TF_Tensor *> Output;
};

size_t TensorSpec::getElementByteSize() const {
  return TF_DataTypeSize(static_cast<TF_DataType>(TypeIndex));
}

TensorSpec::TensorSpec(const std::string &Name, int Port, int TypeIndex,
                       const std::vector<int64_t> &Shape)
    : Name(Name), Port(Port), TypeIndex(TypeIndex), Shape(Shape),
      ElementCount(std::accumulate(Shape.begin(), Shape.end(), 1,
                                   std::multiplies<int64_t>())) {}

Optional<TensorSpec> getTensorSpecFromJSON(LLVMContext &Ctx,
                                           const json::Value &Value) {
  auto EmitError = [&](const llvm::Twine &Message) -> Optional<TensorSpec> {
    std::string S;
    llvm::raw_string_ostream OS(S);
    OS << Value;
    Ctx.emitError("Unable to parse JSON Value as spec (" + Message + "): " + S);
    return None;
  };
  json::ObjectMapper Mapper(Value);
  if (!Mapper)
    return EmitError("Value is not a dict");

  std::string TensorName;
  int TensorPort = -1;
  std::string TensorType;
  std::vector<int64_t> TensorShape;

  if (!Mapper.map<std::string>("name", TensorName))
    return EmitError("'name' property not present or not a string");
  if (!Mapper.map<std::string>("type", TensorType))
    return EmitError("'type' property not present or not a string");
  if (!Mapper.map<int>("port", TensorPort))
    return EmitError("'port' property not present or not an int");
  if (!Mapper.map<std::vector<int64_t>>("shape", TensorShape))
    return EmitError("'shape' property not present or not an int array");

#define PARSE_TYPE(T, S, E)                                                    \
  if (TensorType == #S)                                                        \
    return TensorSpec::createSpec<T>(TensorName, TensorShape, TensorPort);
  TFUTILS_SUPPORTED_TYPES(PARSE_TYPE)
#undef PARSE_TYPE
  return None;
}

class TFModelEvaluatorImpl {
public:
  TFModelEvaluatorImpl(StringRef SavedModelPath,
                       const std::vector<TensorSpec> &InputSpecs,
                       const std::vector<TensorSpec> &OutputSpecs,
                       const char *Tags);

  bool isValid() const { return IsValid; }
  size_t OutputSize() const { return OutputFeed.size(); }

  void evaluate(TF_Tensor **Output, TF_Status *Status) {
    TF_SessionRun(Session, nullptr, InputFeed.data(), Input.data(),
                  Input.size(), OutputFeed.data(), Output, OutputFeed.size(),
                  nullptr, 0, nullptr, Status);
  }

  void initInput(size_t Index, TF_DataType Type,
                 const std::vector<int64_t> &Dimensions);
  const std::vector<TF_Tensor *> &getInput() const { return Input; }

  ~TFModelEvaluatorImpl();

private:
  /// The objects necessary for carrying out an evaluation of the SavedModel.
  /// They are expensive to set up, and we maintain them accross all the
  /// evaluations of the model.
  TF_Session *Session = nullptr;
  TFGraphPtr Graph;
  TFSessionOptionsPtr Options;

  /// The specification of the input nodes.
  std::vector<TF_Output> InputFeed;

  /// The input tensors. They must match by index of the corresponding InputFeed
  /// value. We set up the tensors once and just mutate theirs scalars before
  /// each evaluation. The input tensors keep their value after an evaluation.
  std::vector<TF_Tensor *> Input;

  /// The specification of the output nodes. When evaluating, the tensors in the
  /// output tensor vector must match by index the corresponding element in the
  /// OutputFeed.
  std::vector<TF_Output> OutputFeed;

  void invalidate() { IsValid = false; }

  bool IsValid = true;

  /// Reusable utility for ensuring we can bind the requested Name to a node in
  /// the SavedModel Graph.
  bool checkReportAndInvalidate(const TF_Output &Output,
                                const TensorSpec &OutputSpec);
};
} // namespace llvm

TFModelEvaluatorImpl::TFModelEvaluatorImpl(
    StringRef SavedModelPath, const std::vector<TensorSpec> &InputSpecs,
    const std::vector<TensorSpec> &OutputSpecs, const char *Tags)
    : Graph(createTFGraph()), Options(createTFSessionOptions()),
      InputFeed(InputSpecs.size()), Input(InputSpecs.size()),
      OutputFeed(OutputSpecs.size()) {
  if (!ensureInitTF()) {
    errs() << "Tensorflow should have been initialized";
    return;
  }
  auto Status = createTFStatus();

  Session = TF_LoadSessionFromSavedModel(Options.get(), nullptr,
                                         SavedModelPath.str().c_str(), &Tags, 1,
                                         Graph.get(), nullptr, Status.get());
  if (TF_GetCode(Status.get()) != TF_Code::TF_OK) {
    errs() << TF_Message(Status.get());
    invalidate();
  }
  for (size_t I = 0; I < InputSpecs.size(); ++I) {
    auto &InputSpec = InputSpecs[I];
    InputFeed[I] = {
        TF_GraphOperationByName(Graph.get(), (InputSpec.name()).c_str()),
        InputSpec.port()};
    if (!checkReportAndInvalidate(InputFeed[I], InputSpec))
      return;
    initInput(I, static_cast<TF_DataType>(InputSpec.typeIndex()),
              InputSpec.shape());
  }
  for (size_t I = 0; I < OutputSpecs.size(); ++I) {
    auto &OutputSpec = OutputSpecs[I];
    OutputFeed[I] = {
        TF_GraphOperationByName(Graph.get(), (OutputSpec.name()).c_str()),
        OutputSpec.port()};
    if (!checkReportAndInvalidate(OutputFeed[I], OutputSpec))
      return;
  }
}

TFModelEvaluator::TFModelEvaluator(StringRef SavedModelPath,
                                   const std::vector<TensorSpec> &InputSpecs,
                                   const std::vector<TensorSpec> &OutputSpecs,
                                   const char *Tags)
    : Impl(new TFModelEvaluatorImpl(SavedModelPath, InputSpecs, OutputSpecs,
                                    Tags)) {
  if (!Impl->isValid())
    Impl.reset();
}

TFModelEvaluatorImpl::~TFModelEvaluatorImpl() {
  for (auto *T : Input) {
    TF_DeleteTensor(T);
  }
  if (Session == nullptr)
    return;
  auto Status = createTFStatus();
  TF_DeleteSession(Session, Status.get());
  Session = nullptr;
  if (TF_GetCode(Status.get()) != TF_Code::TF_OK)
    errs() << "Could not delete TF session";
}

bool TFModelEvaluatorImpl::checkReportAndInvalidate(
    const TF_Output &Output, const TensorSpec &OutputSpec) {
  if (Output.oper)
    return true;
  errs() << "Could not find TF_Output named: " + OutputSpec.name();
  IsValid = false;
  return IsValid;
}

Optional<TFModelEvaluator::EvaluationResult> TFModelEvaluator::evaluate() {
  if (!isValid())
    return None;
  std::unique_ptr<EvaluationResultImpl> Ret =
      std::make_unique<EvaluationResultImpl>(Impl->OutputSize());
  auto Status = createTFStatus();
  Impl->evaluate(Ret->getOutput().data(), Status.get());
  if (TF_GetCode(Status.get()) != TF_Code::TF_OK) {
    errs() << TF_Message(Status.get());
    Impl.reset();
    return None;
  }
  return EvaluationResult(std::move(Ret));
}

void TFModelEvaluatorImpl::initInput(size_t Index, TF_DataType Type,
                                     const std::vector<int64_t> &Dimensions) {
  int64_t TotalSize = TF_DataTypeSize(Type);
  for (auto &D : Dimensions)
    TotalSize *= D;

  Input[Index] =
      TF_AllocateTensor(Type, Dimensions.data(), Dimensions.size(), TotalSize);
  std::memset(TF_TensorData(Input[Index]), 0, TotalSize);
}

void *TFModelEvaluator::getUntypedInput(size_t Index) {
  return TF_TensorData(Impl->getInput()[Index]);
}

TFModelEvaluator::EvaluationResult::EvaluationResult(
    std::unique_ptr<EvaluationResultImpl> Impl)
    : Impl(std::move(Impl)) {}

TFModelEvaluator::EvaluationResult::EvaluationResult(EvaluationResult &&Other)
    : Impl(std::move(Other.Impl)) {}

void *TFModelEvaluator::EvaluationResult::getUntypedTensorValue(size_t Index) {
  return TF_TensorData(Impl->getOutput()[Index]);
}

#define TFUTILS_GETDATATYPE_IMPL(T, S, E)                                      \
  template <> int TensorSpec::getDataType<T>() { return TF_##E; }

TFUTILS_SUPPORTED_TYPES(TFUTILS_GETDATATYPE_IMPL)

#undef TFUTILS_GETDATATYPE_IMPL

TFModelEvaluator::EvaluationResult::~EvaluationResult() {}
TFModelEvaluator::~TFModelEvaluator() {}
#endif // defined(LLVM_HAVE_TF_API)