#include <magic.h>
#include <libowfat/errmsg.h>
#include <libowfat/byte.h>
#include <libowfat/str.h>

#include "pipeshare.h"

#define MAX(a,b) (a>b?a:b)

#define failmagic(...) do {                                \
    carp(__VA_ARGS__,": ",magic_error(magic));             \
    return 0;                                              \
  } while(0)

int extension(int64 fd,char result[16])
{
  magic_t magic=magic_open(MAGIC_EXTENSION);
  if(!magic) failmagic("initialize libmagic");
  if(magic_load(magic,NULL)<0) failmagic("load magic database");
  const char *extensions=magic_descriptor(magic,fd);
  if(!extensions) failmagic("get magic data");

  size_t l=MAX(str_chr(extensions,'/'),16);
  byte_copy(result,l,extensions);
  result[l]=0;
  magic_close(magic);
  if(str_equal(result,"???"))
    str_copy(result,"txt");
  return 1;
}

#undef failmagic