/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree.
 */

#include <executorch/kernels/portable/cpu/util/reduce_util.h>
#include <executorch/runtime/kernel/kernel_includes.h>
#include <algorithm>
#include <cinttypes>
#include <cmath>

/**
 * For an input tensor, use the scale and zero_point arguments to quantize it.
 */
namespace torch {
namespace executor {
namespace native {

using Tensor = exec_aten::Tensor;
using Scalar = exec_aten::Scalar;
using ScalarType = exec_aten::ScalarType;

namespace {

/**
 * Asserts that the parameters are valid.
 */
void check_quantize_per_tensor_args(
    const Tensor& input,
    int64_t quant_min,
    int64_t quant_max,
    ScalarType dtype,
    Tensor& out) {
  // Ensure self and out has the same shape
  ET_CHECK_MSG(
      torch::executor::isFloatingType(input.scalar_type()),
      "input.scalar_type() %" PRId8 " is not floating type",
      static_cast<int8_t>(input.scalar_type()));

  int32_t quant_min_lower_bound = 0, quant_max_upper_bound = 0;
  ScalarType out_dtype = out.scalar_type();
  ET_CHECK_MSG(
      out_dtype == dtype,
      "out.scalar_type() %" PRId8 " is not matching dtype argument %" PRId8,
      static_cast<int8_t>(out_dtype),
      static_cast<int8_t>(dtype));
  if (out_dtype == ScalarType::Byte) {
    quant_min_lower_bound =
        static_cast<int32_t>(std::numeric_limits<uint8_t>::min());
    quant_max_upper_bound =
        static_cast<int32_t>(std::numeric_limits<uint8_t>::max());
  } else if (dtype == ScalarType::Char) {
    quant_min_lower_bound =
        static_cast<int32_t>(std::numeric_limits<int8_t>::min());
    quant_max_upper_bound =
        static_cast<int32_t>(std::numeric_limits<int8_t>::max());
  } else if (dtype == ScalarType::Bits16 || dtype == ScalarType::UInt16) {
    quant_min_lower_bound = std::numeric_limits<uint16_t>::min();
    quant_max_upper_bound = std::numeric_limits<uint16_t>::max();
  } else if (dtype == ScalarType::Short) {
    quant_min_lower_bound = std::numeric_limits<int16_t>::min();
    quant_max_upper_bound = std::numeric_limits<int16_t>::max();
  } else if (dtype == ScalarType::Int) {
    quant_min_lower_bound = std::numeric_limits<int32_t>::min();
    quant_max_upper_bound = std::numeric_limits<int32_t>::max();
  } else {
    ET_CHECK_MSG(
        false, "Unsupported dtype: %" PRId8, static_cast<int8_t>(out_dtype));
  }
  ET_CHECK_MSG(
      quant_min >= quant_min_lower_bound,
      "quant_min out of bound for dtype, expected quant_min_lower_bound: %" PRId32
      " actual quant_min: %" PRId64,
      quant_min_lower_bound,
      quant_min);

  ET_CHECK_MSG(
      quant_max <= quant_max_upper_bound,
      "quant_max out of bound for dtype, expected quant_max_upper_bound: %" PRId32
      " actual quant_max: %" PRId64,
      quant_max_upper_bound,
      quant_max);
}

} // namespace

template <typename T, typename K>
T quantize_val(
    double scale,
    int64_t zero_point,
    K value,
    int64_t quant_min,
    int64_t quant_max) {
  int64_t qvalue;
  float inv_scale = 1.0f / static_cast<float>(scale);
  qvalue = static_cast<int64_t>(
      static_cast<int32_t>(zero_point) +
      std::nearbyint(static_cast<float>(inv_scale * value)));

  qvalue = std::max<int64_t>(qvalue, quant_min);
  qvalue = std::min<int64_t>(qvalue, quant_max);
  return static_cast<T>(qvalue);
}

Tensor& quantize_per_tensor_out(
    const Tensor& input,
    double scale,
    int64_t zero_point,
    int64_t quant_min,
    int64_t quant_max,
    ScalarType dtype,
    Tensor& out) {
  torch::executor::Error err = resize_tensor(out, input.sizes());
  ET_CHECK_MSG(
      err == torch::executor::Error::Ok,
      "Failed to resize out Tensor in quantize_per_tensor_out");

  check_quantize_per_tensor_args(input, quant_min, quant_max, dtype, out);

  // calculate the quantized input
#define QUANTIZE_IMPL(IN_CTYPE, OUT_CTYPE, out_dtype)                          \
  case ScalarType::out_dtype: {                                                \
    /* Hoist these function calls out of our inner loop because they might not \
     * get inlined without LTO, particularly in ATen mode. */                  \
    auto* out_data_ptr = out.mutable_data_ptr<OUT_CTYPE>();                    \
    const auto* input_data_ptr = input.const_data_ptr<IN_CTYPE>();             \
    const auto input_numel = input.numel();                                    \
    for (size_t i = 0; i < input_numel; i++) {                                 \
      IN_CTYPE value = input_data_ptr[i];                                      \
      out_data_ptr[i] = quantize_val<OUT_CTYPE, IN_CTYPE>(                     \
          scale, zero_point, value, quant_min, quant_max);                     \
    }                                                                          \
  } break;
#define CALCULATE_FLOAT_TYPE(IN_CTYPE, in_dtype)         \
  case ScalarType::in_dtype:                             \
    switch (out.scalar_type()) {                         \
      ET_FORALL_INT_TYPES_WITH(IN_CTYPE, QUANTIZE_IMPL); \
      QUANTIZE_IMPL(IN_CTYPE, uint16_t, Bits16)          \
      QUANTIZE_IMPL(IN_CTYPE, uint16_t, UInt16)          \
      default:                                           \
        ET_CHECK_MSG(                                    \
            false,                                       \
            "Unhandled output dtype %" PRId8,            \
            static_cast<int8_t>(out.scalar_type()));     \
    }                                                    \
    break;

  switch (input.scalar_type()) {
    ET_FORALL_FLOAT_TYPES(CALCULATE_FLOAT_TYPE);
    default:
      ET_CHECK_MSG(
          false,
          "Unhandled input dtype %" PRId8,
          static_cast<int8_t>(input.scalar_type()));
  }
#undef CALCULATE_FLOAT_TYPE
#undef QUANTIZE_IMPL
  return out;
}

Tensor& quantize_per_tensor_tensor_args_out(
    KernelRuntimeContext& context,
    const Tensor& input,
    const Tensor& scale,
    const Tensor& zero_point,
    int64_t quant_min,
    int64_t quant_max,
    ScalarType dtype,
    Tensor& out) {
  // Temporary change to allow not fatal failure for now to unblock some
  // expected failure tests that are dying instead of failure. Will revisit
  // after ET_KERNEL_CHECK is fully implemented and properly allows non fatal
  // failures.
  if (scale.scalar_type() != ScalarType::Double) {
    context.fail(torch::executor::Error::InvalidArgument);
    return out;
  }
  ET_CHECK_MSG(
      scale.scalar_type() == ScalarType::Double,
      "Expected scale to be Double tensor received: %" PRId8,
      static_cast<int8_t>(scale.scalar_type()));
  ET_CHECK_MSG(
      zero_point.scalar_type() == ScalarType::Long,
      "Expected zero_point to be Long tensor received: %" PRId8,
      static_cast<int8_t>(zero_point.scalar_type()));
  ET_CHECK_MSG(
      scale.numel() == 1,
      "Exepcted scale to only have one element received: %zd",
      ssize_t(scale.numel()));
  ET_CHECK_MSG(
      zero_point.numel() == 1,
      "Exepcted zero_point to only have one element received: %zd",
      ssize_t(zero_point.numel()));

  quantize_per_tensor_out(
      input,
      scale.const_data_ptr<double>()[0],
      zero_point.const_data_ptr<int64_t>()[0],
      quant_min,
      quant_max,
      dtype,
      out);
  return out;
}

Tensor& quantize_per_tensor_tensor_args_out(
    const Tensor& input,
    const Tensor& scale,
    const Tensor& zero_point,
    int64_t quant_min,
    int64_t quant_max,
    ScalarType dtype,
    Tensor& out) {
  auto context = executorch::runtime::KernelRuntimeContext();
  auto& res = quantize_per_tensor_tensor_args_out(
      context, input, scale, zero_point, quant_min, quant_max, dtype, out);
  ET_CHECK(context.failure_state() == Error::Ok);
  return res;
}

Tensor& quantize_per_tensor_out(
    KernelRuntimeContext& context,
    const Tensor& input,
    double scale,
    int64_t zero_point,
    int64_t quant_min,
    int64_t quant_max,
    ScalarType dtype,
    Tensor& out) {
  // TODO(larryliu): Add a context arg to the real op function and remove this
  // wrapper
  (void)context;
  return quantize_per_tensor_out(
      input, scale, zero_point, quant_min, quant_max, dtype, out);
}

Tensor& quantize_per_channel_out(
    const Tensor& input,
    const Tensor& scale,
    const Tensor& zero_point,
    int64_t axis,
    int64_t quant_min,
    int64_t quant_max,
    ScalarType dtype,
    Tensor& out) {
  // normalize axis
  ET_CHECK_MSG(
      tensor_has_dim(input, axis),
      "axis %zd is not legal it should be -input.dim() <= axis < input.dim() %zd",
      ssize_t(axis),
      ssize_t(input.dim()));

  if (axis < 0) {
    axis += nonzero_dim(input);
  }

  ET_CHECK_MSG(
      scale.scalar_type() == ScalarType::Double,
      "scale.scalar_type() %" PRId8 " is not double type",
      static_cast<int8_t>(scale.scalar_type()));

  ET_CHECK_MSG(
      scale.numel() == input.size(axis),
      "scale.numel() %zd != input.size(axis) %zd",
      scale.numel(),
      input.size(axis));

  ET_CHECK_MSG(
      zero_point.scalar_type() == ScalarType::Long,
      "zero_point.scalar_type() %" PRId8 " is not integer type",
      static_cast<int8_t>(zero_point.scalar_type()));

  ET_CHECK_MSG(
      zero_point.numel() == input.size(axis),
      "zero_point.numel() %zd != input.size(axis) %zd",
      zero_point.numel(),
      input.size(axis));

  check_quantize_per_tensor_args(input, quant_min, quant_max, dtype, out);

  // a list contains all dimensions except axis
  int64_t dims[kTensorDimensionLimit];
  for (int64_t i = 0; i < input.dim() - 1; i++) {
    if (i < axis) {
      dims[i] = i;
    } else {
      dims[i] = i - 1;
    }
  }
  const double* scale_data = scale.const_data_ptr<double>();
  const int64_t* zero_point_data = zero_point.const_data_ptr<int64_t>();

  exec_aten::optional<exec_aten::ArrayRef<int64_t>> optional_dim_list{
      exec_aten::ArrayRef<int64_t>{dims, size_t(input.dim() - 1)}};

  // Actual quantization logic
  // input, out are the input and output tensors
  // channel_ix is the index along the axis dimension. 0 <= channel_ix <
  // input.size(axis).
  //   i.e. if the tensor has shape (N,C,H,W), axis being 1, then channel_ix
  //   will be 0, 1, 2, ... C-1
  // in_ix is the flat index of the element you are quantizing.
  //   in other words you are quantizing in_data[in_ix]
#define QUANTIZE_IMPL(CTYPE_IN, CTYPE_OUT, out_dtype)                          \
  case ScalarType::out_dtype:                                                  \
    for (size_t channel_ix = 0; channel_ix < input.size(axis); ++channel_ix) { \
      double _scale = scale_data[channel_ix];                                  \
      int64_t _zero_point = zero_point_data[channel_ix];                       \
      auto* out_data_ptr = out.mutable_data_ptr<CTYPE_OUT>();                  \
      const auto* input_data_ptr = input.const_data_ptr<CTYPE_IN>();           \
      apply_over_dim_list(                                                     \
          [input_data_ptr,                                                     \
           out_data_ptr,                                                       \
           _scale,                                                             \
           _zero_point,                                                        \
           quant_min,                                                          \
           quant_max](size_t in_ix) {                                          \
            out_data_ptr[in_ix] = quantize_val<CTYPE_OUT, CTYPE_IN>(           \
                _scale,                                                        \
                _zero_point,                                                   \
                input_data_ptr[in_ix],                                         \
                quant_min,                                                     \
                quant_max);                                                    \
          },                                                                   \
          input,                                                               \
          optional_dim_list,                                                   \
          channel_ix);                                                         \
    }                                                                          \
    break;
#define CALCULATE_FLOAT_TYPE(CTYPE_IN, in_dtype)         \
  case ScalarType::in_dtype:                             \
    switch (out.scalar_type()) {                         \
      ET_FORALL_INT_TYPES_WITH(CTYPE_IN, QUANTIZE_IMPL); \
      QUANTIZE_IMPL(CTYPE_IN, uint16_t, Bits16)          \
      QUANTIZE_IMPL(CTYPE_IN, uint16_t, UInt16)          \
      default:                                           \
        ET_CHECK_MSG(                                    \
            false,                                       \
            "Unhandled output dtype %" PRId8,            \
            static_cast<int8_t>(out.scalar_type()));     \
    }                                                    \
    break;

  switch (input.scalar_type()) {
    ET_FORALL_FLOAT_TYPES(CALCULATE_FLOAT_TYPE);
    default:
      ET_CHECK_MSG(
          false,
          "Unhandled input dtype %" PRId8,
          static_cast<int8_t>(input.scalar_type()));
  }
#undef CALCULATE_FLOAT_TYPE
#undef QUANTIZE_IMPL

  return out;
}

Tensor& quantize_per_channel_out(
    KernelRuntimeContext& context,
    const Tensor& input,
    const Tensor& scale,
    const Tensor& zero_point,
    int64_t axis,
    int64_t quant_min,
    int64_t quant_max,
    ScalarType dtype,
    Tensor& out) {
  (void)context;
  torch::executor::Error err = resize_tensor(out, input.sizes());
  ET_CHECK_MSG(
      err == torch::executor::Error::Ok,
      "Failed to resize out Tensor in quantize_per_channel_out");

  return quantize_per_channel_out(
      input, scale, zero_point, axis, quant_min, quant_max, dtype, out);
}

Tensor& quantize_per_token_out(
    const Tensor& input,
    const Tensor& scale,
    const Tensor& zero_point,
    int64_t quant_min,
    int64_t quant_max,
    ScalarType dtype,
    Tensor& out) {
  size_t num_tokens = 1;
  for (size_t i = 0; i < input.dim() - 1; i++) {
    num_tokens *= input.size(i);
  }
// This unfortunate change is needed because we compile op_quantize for aten
// mode as well
#ifdef USE_ATEN_LIB
  std::vector<int64_t> sizes(2);
  sizes[0] = num_tokens;
  sizes[1] = input.size(input.dim() - 1);
  Tensor reshaped_input = at::from_blob(
      input.mutable_data_ptr(), sizes, at::TensorOptions(input.scalar_type()));
#else
  std::array<exec_aten::DimOrderType, 2> input_dim_order{0, 1};
  std::array<exec_aten::SizesType, 2> input_sizes;
  input_sizes[0] = num_tokens;
  input_sizes[1] = input.size(input.dim() - 1);
  std::array<exec_aten::StridesType, 2> input_strides;
  dim_order_to_stride_nocheck(
      input_sizes.data(), input_dim_order.data(), 2, input_strides.data());
  void* input_data = input.mutable_data_ptr();
  TensorImpl reshaped_input_impl = TensorImpl(
      input.scalar_type(),
      2,
      input_sizes.data(),
      input_data,
      input_dim_order.data(),
      input_strides.data(),
      TensorShapeDynamism::STATIC);
  Tensor reshaped_input(&reshaped_input_impl);
  torch::executor::Error err = resize_tensor(out, input.sizes());
  ET_CHECK_MSG(
      err == torch::executor::Error::Ok,
      "Failed to resize out Tensor in quantize_per_channel_out");
#endif

  return quantize_per_channel_out(
      reshaped_input, scale, zero_point, 0, quant_min, quant_max, dtype, out);
}

Tensor& quantize_per_token_out(
    RuntimeContext& context,
    const Tensor& input,
    const Tensor& scale,
    const Tensor& zero_point,
    int64_t quant_min,
    int64_t quant_max,
    ScalarType dtype,
    Tensor& out) {
  (void)context;
  return quantize_per_token_out(
      input, scale, zero_point, quant_min, quant_max, dtype, out);
}
} // namespace native
} // namespace executor
} // namespace torch