// Copyright (c) 2018, NVIDIA CORPORATION.  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.

// Implements the required interoperability API from ISO_Fortran_binding.h
// as specified in section 18.5.5 of Fortran 2018.

#include "descriptor.h"

namespace Fortran::ISO {
extern "C" {

void *CFI_address(
    const CFI_cdesc_t *descriptor, const CFI_index_t subscripts[]) {
  auto p = reinterpret_cast<char *>(descriptor->base_addr);
  std::size_t rank{descriptor->rank};
  const CFI_dim_t *dim{descriptor->dim};
  for (std::size_t j{0}; j < rank; ++j, ++dim) {
    p += (subscripts[j] - dim->lower_bound) * dim->sm;
  }
  return reinterpret_cast<void *>(p);
}

int CFI_allocate(CFI_cdesc_t *descriptor, const CFI_index_t lower_bounds[],
    const CFI_index_t upper_bounds[], std::size_t elem_len) {
  if (descriptor->version != CFI_VERSION) {
    return CFI_INVALID_DESCRIPTOR;
  }
  if (descriptor->attribute != CFI_attribute_allocatable &&
      descriptor->attribute != CFI_attribute_pointer) {
    // Non-interoperable object
    return CFI_INVALID_DESCRIPTOR;
  }
  if (descriptor->attribute == CFI_attribute_allocatable &&
      descriptor->base_addr != nullptr) {
    return CFI_ERROR_BASE_ADDR_NOT_NULL;
  }
  if (descriptor->rank > CFI_MAX_RANK) {
    return CFI_INVALID_RANK;
  }
  if (descriptor->type < CFI_type_signed_char ||
      descriptor->type > CFI_type_struct) {
    return CFI_INVALID_TYPE;
  }
  if (descriptor->type != CFI_type_cptr) {
    elem_len = descriptor->elem_len;
    if (elem_len <= 0) {
      return CFI_INVALID_ELEM_LEN;
    }
  }
  std::size_t rank{descriptor->rank};
  CFI_dim_t *dim{descriptor->dim};
  std::size_t byteSize{elem_len};
  for (std::size_t j{0}; j < rank; ++j, ++dim) {
    CFI_index_t lb{lower_bounds[j]};
    CFI_index_t ub{upper_bounds[j]};
    CFI_index_t extent{ub >= lb ? ub - lb + 1 : 0};
    dim->lower_bound = lb;
    dim->extent = extent;
    dim->sm = byteSize;
    byteSize *= extent;
  }
  void *p{new char[byteSize]};
  if (p == nullptr) {
    return CFI_ERROR_MEM_ALLOCATION;
  }
  descriptor->base_addr = p;
  descriptor->elem_len = elem_len;
  return CFI_SUCCESS;
}

int CFI_deallocate(CFI_cdesc_t *descriptor) {
  if (descriptor->version != CFI_VERSION) {
    return CFI_INVALID_DESCRIPTOR;
  }
  if (descriptor->attribute != CFI_attribute_allocatable &&
      descriptor->attribute != CFI_attribute_pointer) {
    // Non-interoperable object
    return CFI_INVALID_DESCRIPTOR;
  }
  if (descriptor->base_addr == nullptr) {
    return CFI_ERROR_BASE_ADDR_NULL;
  }
  delete[] static_cast<char *>(descriptor->base_addr);
  descriptor->base_addr = nullptr;
  return CFI_SUCCESS;
}

static constexpr std::size_t MinElemLen(CFI_type_t type) {
  std::size_t minElemLen{0};
  switch (type) {
  case CFI_type_signed_char: minElemLen = sizeof(signed char); break;
  case CFI_type_short: minElemLen = sizeof(short); break;
  case CFI_type_int: minElemLen = sizeof(int); break;
  case CFI_type_long: minElemLen = sizeof(long); break;
  case CFI_type_long_long: minElemLen = sizeof(long long); break;
  case CFI_type_size_t: minElemLen = sizeof(std::size_t); break;
  case CFI_type_int8_t: minElemLen = sizeof(std::int8_t); break;
  case CFI_type_int16_t: minElemLen = sizeof(std::int16_t); break;
  case CFI_type_int32_t: minElemLen = sizeof(std::int32_t); break;
  case CFI_type_int64_t: minElemLen = sizeof(std::int64_t); break;
  case CFI_type_int128_t: minElemLen = 2 * sizeof(std::int64_t); break;
  case CFI_type_int_least8_t: minElemLen = sizeof(std::int_least8_t); break;
  case CFI_type_int_least16_t: minElemLen = sizeof(std::int_least16_t); break;
  case CFI_type_int_least32_t: minElemLen = sizeof(std::int_least32_t); break;
  case CFI_type_int_least64_t: minElemLen = sizeof(std::int_least64_t); break;
  case CFI_type_int_least128_t:
    minElemLen = 2 * sizeof(std::int_least64_t);
    break;
  case CFI_type_int_fast8_t: minElemLen = sizeof(std::int_fast8_t); break;
  case CFI_type_int_fast16_t: minElemLen = sizeof(std::int_fast16_t); break;
  case CFI_type_int_fast32_t: minElemLen = sizeof(std::int_fast32_t); break;
  case CFI_type_int_fast64_t: minElemLen = sizeof(std::int_fast64_t); break;
  case CFI_type_intmax_t: minElemLen = sizeof(std::intmax_t); break;
  case CFI_type_intptr_t: minElemLen = sizeof(std::intptr_t); break;
  case CFI_type_ptrdiff_t: minElemLen = sizeof(std::ptrdiff_t); break;
  case CFI_type_float: minElemLen = sizeof(float); break;
  case CFI_type_double: minElemLen = sizeof(double); break;
  case CFI_type_long_double: minElemLen = sizeof(long double); break;
  case CFI_type_float_Complex: minElemLen = 2 * sizeof(float); break;
  case CFI_type_double_Complex: minElemLen = 2 * sizeof(double); break;
  case CFI_type_long_double_Complex:
    minElemLen = 2 * sizeof(long double);
    break;
  case CFI_type_Bool: minElemLen = 1; break;
  case CFI_type_char: minElemLen = sizeof(char); break;
  }
  return minElemLen;
}

int CFI_establish(CFI_cdesc_t *descriptor, void *base_addr,
    CFI_attribute_t attribute, CFI_type_t type, std::size_t elem_len,
    CFI_rank_t rank, const CFI_index_t extents[]) {
  if (attribute != CFI_attribute_other && attribute != CFI_attribute_pointer &&
      attribute != CFI_attribute_allocatable) {
    return CFI_INVALID_ATTRIBUTE;
  }
  if (rank > CFI_MAX_RANK) {
    return CFI_INVALID_RANK;
  }
  if (base_addr != nullptr && attribute != CFI_attribute_pointer) {
    return CFI_ERROR_BASE_ADDR_NOT_NULL;
  }
  if (rank > 0 && base_addr != nullptr && extents == nullptr) {
    return CFI_INVALID_EXTENT;
  }
  if (type < CFI_type_signed_char || type > CFI_type_struct) {
    return CFI_INVALID_TYPE;
  }
  std::size_t minElemLen{MinElemLen(type)};
  if (minElemLen > 0) {
    elem_len = minElemLen;
  } else if (elem_len <= 0) {
    return CFI_INVALID_ELEM_LEN;
  }
  descriptor->base_addr = base_addr;
  descriptor->elem_len = elem_len;
  descriptor->version = CFI_VERSION;
  descriptor->rank = rank;
  descriptor->type = type;
  descriptor->attribute = attribute;
  descriptor->f18Addendum = 0;
  std::size_t byteSize{elem_len};
  for (std::size_t j{0}; j < rank; ++j) {
    descriptor->dim[j].lower_bound = 1;
    descriptor->dim[j].extent = extents[j];
    descriptor->dim[j].sm = byteSize;
    byteSize *= extents[j];
  }
  return CFI_SUCCESS;
}

int CFI_is_contiguous(const CFI_cdesc_t *descriptor) {
  CFI_index_t bytes = descriptor->elem_len;
  for (int j{0}; j < descriptor->rank; ++j) {
    if (bytes != descriptor->dim[j].sm) {
      return 0;
    }
    bytes *= descriptor->dim[j].extent;
  }
  return 1;
}

int CFI_section(CFI_cdesc_t *result, const CFI_cdesc_t *source,
    const CFI_index_t lower_bounds[], const CFI_index_t upper_bounds[],
    const CFI_index_t strides[]) {
  return CFI_INVALID_DESCRIPTOR;  // TODO
}

int CFI_select_part(CFI_cdesc_t *result, const CFI_cdesc_t *source,
    std::size_t displacement, std::size_t elem_len) {
  return CFI_INVALID_DESCRIPTOR;  // TODO
}

int CFI_setpointer(CFI_cdesc_t *result, const CFI_cdesc_t *source,
    const CFI_index_t lower_bounds[]) {
  return CFI_INVALID_DESCRIPTOR;  // TODO
}
}  // extern "C"
}  // namespace Fortran::ISO