#include <mruby.h>

#ifndef MRB_NO_FLOAT
/*
 * strtod implementation.
 * author: Yasuhiro Matsumoto (@mattn)
 * license: public domain
 */

/*
The original code can be found in https://github.com/mattn/strtod

I modified the routine for mruby:

 * renamed the function `vim_strtod` -> `mrb_float_read`
 * simplified the code

My modifications in this file are also placed in the public domain.

Matz (Yukihiro Matsumoto)
*/

#include <string.h>
#include <math.h>
#include <errno.h>

MRB_API double
mrb_float_read(const char *str, char **end)
{
  double d = 0.0;
  int sign;
  int n = 0;
  const char *p, *a;

  a = p = str;
  while (ISSPACE(*p))
    ++p;

  /* decimal part */
  sign = 1;
  if (*p == '-') {
    sign = -1;
    ++p;
  } else if (*p == '+')
    ++p;
  if (ISDIGIT(*p)) {
    d = (double)(*p++ - '0');
    while (*p && ISDIGIT(*p)) {
      d = d * 10.0 + (double)(*p - '0');
      ++p;
      ++n;
    }
    a = p;
  } else if (*p != '.')
    goto done;
  d *= sign;

  /* fraction part */
  if (*p == '.') {
    double f = 0.0;
    double base = 0.1;
    ++p;

    if (ISDIGIT(*p))
      {
        while (*p && ISDIGIT(*p)) {
          f += base * (*p - '0') ;
          base /= 10.0;
          ++p;
          ++n;
        }
      }
    d += f * sign;
    a = p;
  }

  /* exponential part */
  if ((*p == 'E') || (*p == 'e')) {
    int e = 0;
    ++p;

    sign = 1;
    if (*p == '-') {
      sign = -1;
      ++p;
    } else if (*p == '+')
      ++p;

    if (ISDIGIT(*p)) {
      while (*p == '0')
        ++p;
      if (*p == '\0') --p;
      e = (int)(*p++ - '0');
      for (; *p && ISDIGIT(*p); p++) {
        if (e < 10000)
          e = e * 10 + (*p - '0');
      }
      e *= sign;
    }
    else if (!ISDIGIT(*(a-1))) {
      a = str;
      goto done;
    }
    else if (*p == 0)
      goto done;
    d *= pow(10.0, (double) e);
    a = p;
  }
  else if (p > str && !ISDIGIT(*(p-1))) {
    a = str;
    goto done;
  }

done:
  if (end)
    *end = (char*)a;
  return d;
}
#endif