//===-- runtime/command.cpp -----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "flang/Runtime/command.h"
#include "environment.h"
#include "stat.h"
#include "terminator.h"
#include "flang/Runtime/descriptor.h"
#include <cstdlib>
#include <limits>

namespace Fortran::runtime {
std::int32_t RTNAME(ArgumentCount)() {
  int argc{executionEnvironment.argc};
  if (argc > 1) {
    // C counts the command name as one of the arguments, but Fortran doesn't.
    return argc - 1;
  }
  return 0;
}

// Returns the length of the \p string. Assumes \p string is valid.
static std::int64_t StringLength(const char *string) {
  std::size_t length{std::strlen(string)};
  if constexpr (sizeof(std::size_t) <= sizeof(std::int64_t)) {
    return static_cast<std::int64_t>(length);
  } else {
    std::size_t max{std::numeric_limits<std::int64_t>::max()};
    return length > max ? 0 // Just fail.
                        : static_cast<std::int64_t>(length);
  }
}

std::int64_t RTNAME(ArgumentLength)(std::int32_t n) {
  if (n < 0 || n >= executionEnvironment.argc ||
      !executionEnvironment.argv[n]) {
    return 0;
  }

  return StringLength(executionEnvironment.argv[n]);
}

static bool IsValidCharDescriptor(const Descriptor *value) {
  return value && value->IsAllocated() &&
      value->type() == TypeCode(TypeCategory::Character, 1) &&
      value->rank() == 0;
}

static void FillWithSpaces(const Descriptor *value) {
  std::memset(value->OffsetElement(), ' ', value->ElementBytes());
}

static std::int32_t CopyToDescriptor(const Descriptor &value,
    const char *rawValue, std::int64_t rawValueLength,
    const Descriptor *errmsg) {
  std::int64_t toCopy{std::min(
      rawValueLength, static_cast<std::int64_t>(value.ElementBytes()))};
  std::memcpy(value.OffsetElement(), rawValue, toCopy);

  if (rawValueLength > toCopy) {
    return ToErrmsg(errmsg, StatValueTooShort);
  }

  return StatOk;
}

std::int32_t RTNAME(ArgumentValue)(
    std::int32_t n, const Descriptor *value, const Descriptor *errmsg) {
  if (IsValidCharDescriptor(value)) {
    FillWithSpaces(value);
  }

  if (n < 0 || n >= executionEnvironment.argc) {
    return ToErrmsg(errmsg, StatInvalidArgumentNumber);
  }

  if (IsValidCharDescriptor(value)) {
    const char *arg{executionEnvironment.argv[n]};
    std::int64_t argLen{StringLength(arg)};
    if (argLen <= 0) {
      return ToErrmsg(errmsg, StatMissingArgument);
    }

    return CopyToDescriptor(*value, arg, argLen, errmsg);
  }

  return StatOk;
}

static std::size_t LengthWithoutTrailingSpaces(const Descriptor &d) {
  std::size_t s{d.ElementBytes() - 1};
  while (*d.OffsetElement(s) == ' ') {
    --s;
  }
  return s + 1;
}

static const char *GetEnvVariableValue(
    const Descriptor &name, bool trim_name, const char *sourceFile, int line) {
  std::size_t nameLength{
      trim_name ? LengthWithoutTrailingSpaces(name) : name.ElementBytes()};
  if (nameLength == 0) {
    return nullptr;
  }

  Terminator terminator{sourceFile, line};
  const char *value{executionEnvironment.GetEnv(
      name.OffsetElement(), nameLength, terminator)};
  return value;
}

std::int32_t RTNAME(EnvVariableValue)(const Descriptor &name,
    const Descriptor *value, bool trim_name, const Descriptor *errmsg,
    const char *sourceFile, int line) {
  if (IsValidCharDescriptor(value)) {
    FillWithSpaces(value);
  }

  const char *rawValue{GetEnvVariableValue(name, trim_name, sourceFile, line)};
  if (!rawValue) {
    return ToErrmsg(errmsg, StatMissingEnvVariable);
  }

  if (IsValidCharDescriptor(value)) {
    return CopyToDescriptor(*value, rawValue, StringLength(rawValue), errmsg);
  }

  return StatOk;
}

std::int64_t RTNAME(EnvVariableLength)(
    const Descriptor &name, bool trim_name, const char *sourceFile, int line) {
  const char *value{GetEnvVariableValue(name, trim_name, sourceFile, line)};
  if (!value) {
    return 0;
  }
  return StringLength(value);
}
} // namespace Fortran::runtime