/* ISC license. */

#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <sys/stat.h>
#include <errno.h>
#include <time.h>
#include <utmpx.h>

#include <skalibs/uint32.h>
#include <skalibs/types.h>
#include <skalibs/allreadwrite.h>
#include <skalibs/strerr2.h>
#include <skalibs/sgetopt.h>
#include <skalibs/sig.h>
#include <skalibs/tai.h>
#include <skalibs/djbunix.h>
#include <skalibs/djbtime.h>

#include "defaults.h"
#include "initctl.h"
#include "hpr.h"

#ifndef UT_NAMESIZE
#define UT_NAMESIZE 32
#endif

#define USAGE "s6-linux-init-shutdown [ -h [ -H | -P ] | -p | -r | -k ] [ -f | -F ] [ -a ] [ -t sec ] time [ message ]  or  s6-linux-init-shutdown -c [ message ]"
#define dieusage() strerr_dieusage(100, USAGE)

#define AC_FILE "/etc/shutdown.allow"
#define AC_BUFSIZE 4096
#define AC_MAX 64


 /* shutdown 01:23: date/time format parsing */

static inline void add_one_day (struct tm *tm)
{
  tm->tm_isdst = -1 ;
  if (tm->tm_mday++ < 31) return ;
  tm->tm_mday = 1 ;
  if (tm->tm_mon++ < 11) return ;
  tm->tm_mon = 0 ;
  tm->tm_year++ ;
}

static inline void parse_hourmin (tain_t *when, char const *s)
{
  tai_t taithen ;
  struct tm tmthen ;
  unsigned int hour, minute ;
  size_t len = uint_scan(s, &hour) ;
  if (!len || len > 2 || s[len] != ':' || hour > 23)
    strerr_dief1x(100, "invalid time format") ;
  s += len+1 ;
  len = uint0_scan(s, &minute) ;
  if (!len || len != 2 || minute > 59)
    strerr_dief1x(100, "invalid time format") ;
  if (!localtm_from_tai(&tmthen, tain_secp(&STAMP), 1))
    strerr_diefu1sys(111, "break down current time into struct tm") ;
  tmthen.tm_hour = hour ;
  tmthen.tm_min = minute ;
  tmthen.tm_sec = 0 ;
  if (!tai_from_localtm(&taithen, &tmthen))
    strerr_diefu1sys(111, "assemble broken-down time into tain_t") ;
  if (tai_less(&taithen, tain_secp(&STAMP)))
  {
    add_one_day(&tmthen) ;
    if (!tai_from_localtm(&taithen, &tmthen))
      strerr_diefu1sys(111, "assemble broken-down time into tain_t") ;
  }
  when->sec = taithen ;
  when->nano = 0 ;
}

static void parse_mins (tain_t *when, char const *s)
{
  unsigned int mins ;
  if (!uint0_scan(s, &mins)) dieusage() ;
  tain_addsec_g(when, mins * 60) ;
}

static inline void parse_time (tain_t *when, char const *s)
{
  if (!strcmp(s, "now")) tain_copynow(when) ;
  else if (s[0] == '+') parse_mins(when, s+1) ;
  else if (strchr(s, ':')) parse_hourmin(when, s) ;
  else parse_mins(when, s) ;
}


 /* shutdown -a: access control */

static inline unsigned char cclass (unsigned char c)
{
  switch (c)
  {
    case 0 : return 0 ;
    case '\n' : return 1 ;
    case '#' : return 2 ;
    default : return 3 ;
  }
}

static inline unsigned int parse_authorized_users (char *buf, char const **users, unsigned int max)
{
  static unsigned char const table[3][4] =
  {
    { 0x03, 0x00, 0x01, 0x12 },
    { 0x03, 0x00, 0x01, 0x01 },
    { 0x23, 0x20, 0x02, 0x02 }
  } ;
  size_t pos = 0 ;
  size_t mark = 0 ;
  unsigned int n = 0 ;
  unsigned int state = 0 ;
  for (; state < 3 ; pos++)
  {
    unsigned char what = table[state][cclass(buf[pos])] ;
    state = what & 3 ;
    if (what & 0x10) mark = pos ;
    if (what & 0x20)
    {
      if (n >= max)
      {
        char fmt[UINT32_FMT] ;
        fmt[uint32_fmt(fmt, AC_MAX)] = 0 ;
        strerr_warnw4x(AC_FILE, " lists more than ", fmt, " authorized users - ignoring the extra ones") ;
        break ;
      }
      buf[pos] = 0 ;
      users[n++] = buf + mark ;
    }
  }
  return n ;
}

static inline int match_users_with_utmp (char const *const *users, unsigned int n)
{
  setutxent() ;
  for (;;)
  {
    struct utmpx *utx ;
    errno = 0 ;
    utx = getutxent() ;
    if (!utx) break ;
    if (utx->ut_type != USER_PROCESS) continue ;
    for (unsigned int i = 0 ; i < n ; i++)
      if (!strncmp(utx->ut_user, users[i], UT_NAMESIZE)) goto yes ;
  }
  endutxent() ;
  return 0 ;

 yes:
  endutxent() ;
  return 1 ;
}

static inline void access_control (void)
{
  char buf[AC_BUFSIZE] ;
  char const *users[AC_MAX] ;
  unsigned int n ;
  struct stat st ;
  int fd = open_readb(AC_FILE) ;
  if (fd == -1)
  {
    if (errno == ENOENT) return ;
    strerr_diefu2sys(111, "open ", AC_FILE) ;
  }
  if (fstat(fd, &st) == -1)
    strerr_diefu2sys(111, "stat ", AC_FILE) ;
  if (st.st_size >= AC_BUFSIZE)
  {
    char fmt[UINT32_FMT] ;
    fmt[uint32_fmt(fmt, AC_BUFSIZE - 1)] = 0 ;
    strerr_dief4x(1, AC_FILE, " is too big: it needs to be ", fmt, " bytes or less") ;
  }
  if (allread(fd, buf, st.st_size) < st.st_size)
    strerr_diefu2sys(111, "read ", AC_FILE) ;
  fd_close(fd) ;
  buf[st.st_size] = 0 ;
  n = parse_authorized_users(buf, users, AC_MAX) ;
  if (!n || !match_users_with_utmp(users, n))
    strerr_dief1x(1, "no authorized users logged in") ;
}


 /* main */

int main (int argc, char const *const *argv)
{
  unsigned int gracetime = 0 ;
  int what = 0 ;
  int subwhat = 0 ;
  int doactl = 0 ;
  int docancel = 0 ;
  tain_t when ;
  PROG = "s6-linux-init-shutdown" ;

  {
    subgetopt_t l = SUBGETOPT_ZERO ;
    for (;;)
    {
      int opt = subgetopt_r(argc, argv, "HPhprkafFct:", &l) ;
      if (opt == -1) break ;
      switch (opt)
      {
        case 'H' : subwhat = 1 ; break ;
        case 'P' : subwhat = 2 ; break ;
        case 'h' : what = 1 ; break ;
        case 'p' : what = 2 ; break ;
        case 'r' : what = 3 ; break ;
        case 'k' : what = 4 ; break ;
        case 'a' : doactl = 1 ; break ;
        case 'f' : /* talk to the hand */ break ;
        case 'F' : /* no, the other hand */ break ;
        case 'c' : docancel = 1 ; break ;
        case 't' : if (!uint0_scan(l.arg, &gracetime)) dieusage() ; break ;
        default : strerr_dieusage(100, USAGE) ;
      }
    }
    argc -= l.ind ; argv += l.ind ;
  }

  if (subwhat)
  {
    if (what == 1) what = subwhat ;
    else strerr_dieusage(100, USAGE) ;
  }
  if (geteuid())
  {
    errno = EPERM ;
    strerr_diefu1sys(111, "shutdown") ;
  }
  if (doactl) access_control() ;
  if (!tain_now_g()) strerr_warnw1sys("get current time") ;
  if (docancel)
  {
    if (argv[0]) hpr_wall(argv[0]) ;
    if (!hpr_cancel()) goto err ;
    return 0 ;
  }
  if (!argc) dieusage() ;
  parse_time(&when, argv[0]) ;
  tain_sub(&when, &when, &STAMP) ;
  if (argv[1])
  {
    size_t len = strlen(argv[1]) ;
    char msg[sizeof(HPR_WALL_BANNER) + 1 + len] ;
    memcpy(msg, HPR_WALL_BANNER, sizeof(HPR_WALL_BANNER) - 1) ;
    msg[sizeof(HPR_WALL_BANNER) - 1] = '\n' ;
    memcpy(msg + sizeof(HPR_WALL_BANNER), argv[1], len + 1) ;
    hpr_wall(msg) ;
  }
  if (what < 4)
  {
    if (gracetime > 300)
    {
      gracetime = 300 ;
      strerr_warnw1x("delay between SIGTERM and SIGKILL is capped to 300 seconds") ;
    }
    if (!hpr_shutdown(what, &when, gracetime * 1000)) goto err ;
  }
  return 0 ;

 err:
  strerr_diefu2sys(111, "write to ", INITCTL) ;
}