// Prelude for PyTorch cpp binding.

#include <torch/extension.h>
#include <ATen/cuda/CUDAContext.h>
#include <ATen/cuda/CUDAUtils.h>
#include <vector>
#include <stdexcept>
#include <string>

#ifdef SLANG_LLVM
#include "slang-llvm.h"
#else // SLANG_LLVM
#   if SLANG_GCC_FAMILY && __GNUC__ < 6
#       include <cmath>
#       define SLANG_PRELUDE_STD std::
#   else
#       include <math.h>
#       define SLANG_PRELUDE_STD
#   endif

#   include <assert.h>
#   include <stdlib.h>
#   include <string.h>
#   include <stdint.h>
#endif // SLANG_LLVM

#include "../source/core/slang-string.h"

#if defined(_MSC_VER)
#   define SLANG_PRELUDE_SHARED_LIB_EXPORT __declspec(dllexport)
#else
#   define SLANG_PRELUDE_SHARED_LIB_EXPORT __attribute__((__visibility__("default")))
//#   define SLANG_PRELUDE_SHARED_LIB_EXPORT __attribute__ ((dllexport)) __attribute__((__visibility__("default")))
#endif    

#ifdef __cplusplus    
#   define SLANG_PRELUDE_EXTERN_C extern "C"
#   define SLANG_PRELUDE_EXTERN_C_START extern "C" {
#   define SLANG_PRELUDE_EXTERN_C_END }
#else
#   define SLANG_PRELUDE_EXTERN_C 
#   define SLANG_PRELUDE_EXTERN_C_START
#   define SLANG_PRELUDE_EXTERN_C_END 
#endif    

#define SLANG_PRELUDE_NAMESPACE

#ifndef SLANG_NO_THROW
#   define SLANG_NO_THROW
#endif
#ifndef SLANG_STDCALL
#   define SLANG_STDCALL
#endif
#ifndef SLANG_MCALL
#   define SLANG_MCALL SLANG_STDCALL
#endif
#ifndef SLANG_FORCE_INLINE
#    define SLANG_FORCE_INLINE inline
#endif
#include "slang-cpp-types-core.h"
#include "slang-cpp-scalar-intrinsics.h"


static const int kSlangTorchTensorMaxDim = 5;

struct TensorView
{
    uint8_t* data;
    uint32_t strides[kSlangTorchTensorMaxDim];
    uint32_t sizes[kSlangTorchTensorMaxDim];
    uint32_t dimensionCount;
};


TensorView make_tensor_view(torch::Tensor val, const char* name, torch::ScalarType targetScalarType, bool requireContiguous)
{
    // We're currently not trying to implicitly cast or transfer to device for two reasons:
    // 1. There appears to be a bug with .to() where successive calls after the first one fail.
    // 2. Silent casts like this can cause large memory allocations & unexpected overheads. 
    //    It's better to be explicit.

    // Expect tensors to be on CUDA device
    if (!val.device().is_cuda())
        throw std::runtime_error(std::string(name).append(": tensor is not on CUDA device.").c_str());

    // Expect tensors to be the right type.
    if (val.dtype() != targetScalarType)
        throw std::runtime_error(std::string(name).append(": tensor is not of the expected type.").c_str());

    // Check that the tensor is contiguous
    if (requireContiguous && !val.is_contiguous())
        throw std::runtime_error(std::string(name).append(": tensor is not contiguous.").c_str());

    TensorView res = {};
    res.dimensionCount = val.dim();
    res.data = nullptr;
    size_t elementSize = 4;

    switch (val.scalar_type())
    {
    case torch::kInt8:
    case torch::kUInt8:
        elementSize = 1;
        res.data = (uint8_t*)val.data_ptr<uint8_t>();
        break;
    case torch::kBFloat16:
        elementSize = 2;
        res.data = (uint8_t*)val.data_ptr<torch::BFloat16>();
        break;
    case torch::kFloat16:
        elementSize = 2;
        res.data = (uint8_t*)val.data_ptr<at::Half>();
        break;
    case torch::kInt16:
        elementSize = 2;
        res.data = (uint8_t*)val.data_ptr<int16_t>();
        break;
    case torch::kFloat32:
        elementSize = 4;
        res.data = (uint8_t*)val.data_ptr<float>();
        break;
    case torch::kInt32:
        elementSize = 4;
        res.data = (uint8_t*)val.data_ptr<int32_t>();
        break;
    case torch::kFloat64:
        elementSize = 8;
        res.data = (uint8_t*)val.data_ptr<double>();
        break;
    case torch::kInt64:
        elementSize = 8;
        res.data = (uint8_t*)val.data_ptr<int64_t>();
        break;
    case torch::kBool:
        elementSize = 1;
        res.data = (uint8_t*)val.data_ptr<bool>();
        break;
    }

    if (val.dim() > kSlangTorchTensorMaxDim)
        throw std::runtime_error(std::string(name).append(": number of dimensions exceeds limit (").append(std::to_string(kSlangTorchTensorMaxDim)).append(")").c_str());

    bool isEmpty = true;
    for (int i = 0; i < val.dim(); ++i)
    {
        res.strides[i] = val.stride(i) * elementSize;
        if (res.strides[i] == 0)
            throw std::runtime_error(std::string(name).append(": tensors with broadcasted dimensions are not supported (use tensor.contiguous() to make tensor whole)").c_str());

        res.sizes[i] = val.size(i);
        if (res.sizes[i] > 0)
            isEmpty = false;
    }

    if (!res.data && !isEmpty)
        throw std::runtime_error(std::string(name).append(": data pointer is invalid.").c_str());

    return res;
}

#define SLANG_PRELUDE_EXPORT
