#include "dietfeatures.h"
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <netinet/in.h>
#include <time.h>

/* #include <stdio.h> */

char* tzname[2]={"GMT","GMT"};

#ifdef WANT_TZFILE_PARSER
static char *tzfile=0;
static int tzlen=-1;

void __maplocaltime(void);
void __maplocaltime(void) {
  int fd;
  unsigned int len;
  if (tzlen>=0) return;
  tzlen=0;
  if ((fd=open("/etc/localtime",O_RDONLY))<0) return;
  len=lseek(fd,0,SEEK_END);
  if ((tzfile=mmap(0,len,PROT_READ,MAP_PRIVATE,fd,0))==MAP_FAILED) return;
  close(fd);
  if (ntohl(*(int*)tzfile) != 0x545a6966) return;
  tzlen=len;
}

static unsigned long __myntohl(const unsigned char* c) {
  return (((unsigned long)c[0])<<24) +
         (((unsigned long)c[1])<<16) +
         (((unsigned long)c[2])<<8) +
         ((unsigned long)c[3]);
}

time_t __tzfile_map(time_t t, int *isdst);
time_t __tzfile_map(time_t t, int *isdst) {
  /* "TZif" plus 16 reserved bytes. */
  char *tmp;
  int i;
  int tzh_ttisgmtcnt, tzh_ttisstdcnt, tzh_leapcnt, tzh_timecnt, tzh_typecnt, tzh_charcnt;
  *isdst=0;
  if (!tzfile) return t;
  tzh_ttisgmtcnt=ntohl(*(int*)(tzfile+20));
  tzh_ttisstdcnt=ntohl(*(int*)(tzfile+24));
  tzh_leapcnt=ntohl(*(int*)(tzfile+28));
  tzh_timecnt=ntohl(*(int*)(tzfile+32));
  tzh_typecnt=ntohl(*(int*)(tzfile+36));
  tzh_charcnt=ntohl(*(int*)(tzfile+40));

#if 0
  tmp=tzfile+20+6*4;
  printf("ttisgmtcnt %d ttisstdcnt %d leapcnt %d timecnt %d typecnt %d charcnt %d\n",tzh_ttisgmtcnt,tzh_ttisstdcnt, tzh_leapcnt, tzh_timecnt, tzh_typecnt, tzh_charcnt);
  printf("transition times: ");
  for (i=0; i<tzh_timecnt; ++i) {
    printf("%s%lu",i?", ":"",ntohl(*(int*)tmp)); tmp+=4;
  }
  printf("\n");
  printf("indices: ");
  for (i=0; i<tzh_timecnt; ++i) {
    printf("%s%d",i?", ":"",*tmp); ++tmp;
  }
  printf("\n");
  printf("transition times: ");
  for (i=0; i<tzh_typecnt; ++i) {
    printf("%s(%lu,%d,%d)",i?", ":"",ntohl(*(int*)tmp),tmp[4],tmp[5]); tmp+=6;
  }
  printf("\n");
  for (i=0; i<tzh_charcnt; ++i) {
    printf("%s\"%s\"",i?", ":"",tmp);
    tmp+=strlen(tmp);
  }
  printf("\n");
#endif

  tmp=tzfile+20+6*4;
  daylight=(tzh_timecnt>0);
  for (i=0; i<tzh_timecnt; ++i) {
    if ((time_t)__myntohl(tmp+i*4) >= t) {
      char* tz=tmp;
/*      printf("match at %d\n",i); */
      tmp+=tzh_timecnt*4;
      i=tmp[i-1];
/*      printf("using index %d\n",i); */
      tmp+=tzh_timecnt;
      tz+=tzh_timecnt*5+tzh_leapcnt*4+tzh_typecnt*6;
      tmp+=i*6;
/*      printf("(%lu,%d,%d)\n",ntohl(*(int*)tmp),tmp[4],tmp[5]); */
      *isdst=tmp[4];
      tzname[0]=tz+tmp[5];
      timezone=-(__myntohl(tmp));
      return t-timezone;
    }
  }
  return t;
}

void tzset(void) {
  int isdst;
  __maplocaltime();
  __tzfile_map(time(0),&isdst);
}

#else
void tzset(void)	__attribute__((weak,alias("__nop")));
#endif