#include "fast_float/fast_float.h"

#include <cassert>
#include <cmath>
#include <cstdio>
#include <ios>
#include <iostream>
#include <limits>
#include <stdexcept>

#if defined(__CYGWIN__) || defined(__MINGW32__) || defined(__MINGW64__)
// Anything at all that is related to cygwin, msys and so forth will
// always use this fallback because we cannot rely on it behaving as normal
// gcc.
#include <locale>
#include <sstream>

// workaround for CYGWIN
double cygwin_strtod_l(char const *start, char **end) {
  double d;
  std::stringstream ss;
  ss.imbue(std::locale::classic());
  ss << start;
  ss >> d;
  if (ss.fail()) {
    *end = nullptr;
  }
  if (ss.eof()) {
    ss.clear();
  }
  auto nread = ss.tellg();
  *end = const_cast<char *>(start) + nread;
  return d;
}

float cygwin_strtof_l(char const *start, char **end) {
  float d;
  std::stringstream ss;
  ss.imbue(std::locale::classic());
  ss << start;
  ss >> d;
  if (ss.fail()) {
    *end = nullptr;
  }
  if (ss.eof()) {
    ss.clear();
  }
  auto nread = ss.tellg();
  *end = const_cast<char *>(start) + nread;
  return d;
}
#endif

template <typename T> char *to_string(T d, char *buffer) {
  auto written = std::snprintf(buffer, 64, "%.*e",
                               std::numeric_limits<T>::max_digits10 - 1, d);
  return buffer + written;
}

void strtof_from_string(char const *st, float &d) {
  char *pr = (char *)st;
#if defined(__CYGWIN__) || defined(__MINGW32__) || defined(__MINGW64__) ||     \
    defined(sun) || defined(__sun)
  d = cygwin_strtof_l(st, &pr);
#elif defined(_WIN32)
  static _locale_t c_locale = _create_locale(LC_ALL, "C");
  d = _strtof_l(st, &pr, c_locale);
#else
  static locale_t c_locale = newlocale(LC_ALL_MASK, "C", NULL);
  d = strtof_l(st, &pr, c_locale);
#endif
  if (pr == st) {
    throw std::runtime_error("bug in strtod_from_string");
  }
}

bool allvalues() {
  char buffer[64];
  for (uint64_t w = 0; w <= 0xFFFFFFFF; w++) {
    float v;
    if ((w % 1048576) == 0) {
      std::cout << ".";
      std::cout.flush();
    }
    uint32_t word = uint32_t(w);
    memcpy(&v, &word, sizeof(v));
    if (std::isfinite(v)) {
      float nextf = std::nextafterf(v, INFINITY);
      if (copysign(1, v) != copysign(1, nextf)) {
        continue;
      }
      if (!std::isfinite(nextf)) {
        continue;
      }
      double v1{v};
      assert(float(v1) == v);
      double v2{nextf};
      assert(float(v2) == nextf);
      double midv{v1 + (v2 - v1) / 2};
      float expected_midv = float(midv);

      char const *string_end = to_string(midv, buffer);
      float str_answer;
      strtof_from_string(buffer, str_answer);

      float result_value;
      auto result = fast_float::from_chars(buffer, string_end, result_value);
      // Starting with version 4.0 for fast_float, we return result_out_of_range
      // if the value is either too small (too close to zero) or too large
      // (effectively infinity). So std::errc::result_out_of_range is normal for
      // well-formed input strings.
      if (result.ec != std::errc() &&
          result.ec != std::errc::result_out_of_range) {
        std::cerr << "parsing error ? " << buffer << std::endl;
        return false;
      }
      if (std::isnan(v)) {
        if (!std::isnan(result_value)) {
          std::cerr << "not nan" << buffer << std::endl;
          std::cerr << "v " << std::hexfloat << v << std::endl;
          std::cerr << "v2 " << std::hexfloat << v2 << std::endl;
          std::cerr << "midv " << std::hexfloat << midv << std::endl;
          std::cerr << "expected_midv " << std::hexfloat << expected_midv
                    << std::endl;
          return false;
        }
      } else if (copysign(1, result_value) != copysign(1, v)) {
        std::cerr << buffer << std::endl;
        std::cerr << "v " << std::hexfloat << v << std::endl;
        std::cerr << "v2 " << std::hexfloat << v2 << std::endl;
        std::cerr << "midv " << std::hexfloat << midv << std::endl;
        std::cerr << "expected_midv " << std::hexfloat << expected_midv
                  << std::endl;
        std::cerr << "I got " << std::hexfloat << result_value
                  << " but I was expecting " << v << std::endl;
        return false;
      } else if (result_value != str_answer) {
        std::cerr << "no match ? " << buffer << std::endl;
        std::cerr << "v " << std::hexfloat << v << std::endl;
        std::cerr << "v2 " << std::hexfloat << v2 << std::endl;
        std::cerr << "midv " << std::hexfloat << midv << std::endl;
        std::cerr << "expected_midv " << std::hexfloat << expected_midv
                  << std::endl;
        std::cout << "started with " << std::hexfloat << midv << std::endl;
        std::cout << "round down to " << std::hexfloat << str_answer
                  << std::endl;
        std::cout << "got back " << std::hexfloat << result_value << std::endl;
        std::cout << std::dec;
        return false;
      }
    }
  }
  std::cout << std::endl;
  return true;
}

inline void Assert(bool Assertion) {
#if defined(__CYGWIN__) || defined(__MINGW32__) || defined(__MINGW64__) ||     \
    defined(sun) || defined(__sun)
  if (!Assertion) {
    std::cerr << "Omitting hard failure on msys/cygwin/sun systems.";
  }
#else
  if (!Assertion) {
    throw std::runtime_error("bug");
  }
#endif
}

int main() {
#if defined(__CYGWIN__) || defined(__MINGW32__) || defined(__MINGW64__) ||     \
    defined(sun) || defined(__sun)
  std::cout << "Warning: msys/cygwin or solaris detected. This particular test "
               "is likely to generate false failures due to our reliance on "
               "the underlying runtime library as a gold standard."
            << std::endl;
#endif
  Assert(allvalues());
  std::cout << std::endl;
  std::cout << "all ok" << std::endl;
  return EXIT_SUCCESS;
}