/* date - print or set the system date and time
   Copyright (C) 89, 90, 91, 92, 93, 94, 95, 96, 1997
   Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   David MacKenzie <djm@gnu.ai.mit.edu> */

#include <config.h>
#include <stdio.h>
#include <getopt.h>
#include <sys/types.h>

#include "system.h"
#include "getline.h"
#include "error.h"
#include "getdate.h"
#include "posixtm.h"

#ifndef STDC_HEADERS
size_t strftime ();
time_t time ();
#endif

int putenv ();
int stime ();

char *xstrdup ();

static void show_date PARAMS ((const char *format, time_t when));
static void usage PARAMS ((int status));

/* The name this program was run with, for error messages. */
char *program_name;

/* If nonzero, display usage information and exit.  */
static int show_help;

/* If nonzero, print the version on standard output and exit.  */
static int show_version;

/* If non-zero, display time in RFC-822 format for mail or news. */
static int rfc_format = 0;

/* If nonzero, print or set Coordinated Universal Time.  */
static int universal_time = 0;

static struct option const long_options[] =
{
  {"date", required_argument, NULL, 'd'},
  {"file", required_argument, NULL, 'f'},
  {"help", no_argument, &show_help, 1},
  {"reference", required_argument, NULL, 'r'},
  {"rfc-822", no_argument, NULL, 'R'},
  {"set", required_argument, NULL, 's'},
  {"uct", no_argument, NULL, 'u'},
  {"utc", no_argument, NULL, 'u'},
  {"universal", no_argument, NULL, 'u'},
  {"version", no_argument, &show_version, 1},
  {NULL, 0, NULL, 0}
};

#define TZ_UTC0 "TZ=UTC0"

#if LOCALTIME_CACHE
# define TZSET tzset ()
#else
# define TZSET /* empty */
#endif

#define MAYBE_SET_TZ_UTC0 \
  do { if (universal_time) set_tz (TZ_UTC0); } while (0)

/* Set the TZ environment variable.  */

static void
set_tz (const char *tz_eq_zone)
{
  if (putenv (tz_eq_zone) != 0)
    error (1, 0, "memory exhausted");
  TZSET;
}

/* Parse each line in INPUT_FILENAME as with --date and display each
   resulting time and date.  If the file cannot be opened, tell why
   then exit.  Issue a diagnostic for any lines that cannot be parsed.
   If any line cannot be parsed, return nonzero;  otherwise return zero.  */

static int
batch_convert (const char *input_filename, const char *format)
{
  int status;
  FILE *in_stream;
  char *line;
  int line_length;
  size_t buflen;
  time_t when;
  char *initial_TZ;

#ifdef lint
  /* Suppress `may be used before initialized' warning.  */
  initial_TZ = NULL;
#endif

  if (strcmp (input_filename, "-") == 0)
    {
      input_filename = _("standard input");
      in_stream = stdin;
    }
  else
    {
      in_stream = fopen (input_filename, "r");
      if (in_stream == NULL)
	{
	  error (1, errno, "`%s'", input_filename);
	}
    }

  line = NULL;
  buflen = 0;

  if (universal_time)
    {
      initial_TZ = getenv ("TZ");
      if (initial_TZ == NULL)
	{
	  initial_TZ = xstrdup ("TZ=");
	}
      else
	{
	  size_t tz_len = strlen (initial_TZ);
	  char *buf = xmalloc (3 + tz_len + 1);
	  memcpy (mempcpy (buf, "TZ=", 3), initial_TZ, tz_len + 1);
	  initial_TZ = buf;
	}
    }

  status = 0;
  while (1)
    {
      line_length = getline (&line, &buflen, in_stream);
      if (line_length < 0)
	{
	  /* FIXME: detect/handle error here.  */
	  break;
	}

      if (universal_time)
	{
	  /* When given a universal time option, restore the initial
	     value of TZ before parsing each string.  */
	  set_tz (initial_TZ);
	}

      when = get_date (line, NULL);

      if (when == -1)
	{
	  if (line[line_length - 1] == '\n')
	    line[line_length - 1] = '\0';
	  error (0, 0, _("invalid date `%s'"), line);
	  status = 1;
	}
      else
	{
	  MAYBE_SET_TZ_UTC0;
	  show_date (format, when);
	}
    }

  free (initial_TZ);

  if (fclose (in_stream) == EOF)
    error (2, errno, input_filename);

  if (line != NULL)
    free (line);

  return status;
}

int
main (int argc, char **argv)
{
  int optc;
  const char *datestr = NULL;
  const char *set_datestr = NULL;
  time_t when;
  int set_date = 0;
  char *format;
  char *batch_file = NULL;
  char *reference = NULL;
  struct stat refstats;
  int n_args;
  int status;
  int option_specified_date;

  program_name = argv[0];
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

  while ((optc = getopt_long (argc, argv, "d:f:r:Rs:u", long_options, NULL))
	 != -1)
    switch (optc)
      {
      case 0:
	break;
      case 'd':
	datestr = optarg;
	break;
      case 'f':
	batch_file = optarg;
	break;
      case 'r':
	reference = optarg;
	break;
      case 'R':
	rfc_format = 1;
	break;
      case 's':
	set_datestr = optarg;
	set_date = 1;
	break;
      case 'u':
 	universal_time = 1;
	break;
      default:
	usage (1);
      }

  if (show_version)
    {
      printf ("date (%s) %s\n", GNU_PACKAGE, VERSION);
      exit (0);
    }

  if (show_help)
    usage (0);

  n_args = argc - optind;

  option_specified_date = ((datestr ? 1 : 0)
			   + (batch_file ? 1 : 0)
			   + (reference ? 1 : 0));

  if (option_specified_date > 1)
    {
      error (0, 0,
	_("the options to specify dates for printing are mutually exclusive"));
      usage (1);
    }

  if (set_date && option_specified_date)
    {
      error (0, 0,
	  _("the options to print and set the time may not be used together"));
      usage (1);
    }

  if (n_args > 1)
    {
      error (0, 0, _("too many non-option arguments"));
      usage (1);
    }

  if ((set_date || option_specified_date)
      && n_args == 1 && argv[optind][0] != '+')
    {
      error (0, 0, _("\
the argument `%s' lacks a leading `+';\n\
When using an option to specify date(s), any non-option\n\
argument must be a format string beginning with `+'."),
	     argv[optind]);
      usage (1);
    }

  if (set_date)
    datestr = set_datestr;

  if (batch_file != NULL)
    {
      status = batch_convert (batch_file,
			      (n_args == 1 ? argv[optind] + 1 : NULL));
    }
  else
    {
      status = 0;

      if (!option_specified_date && !set_date)
	{
	  if (n_args == 1 && argv[optind][0] != '+')
	    {
	      /* Prepare to set system clock to the specified date/time
		 given in the POSIX-format.  */
	      set_date = 1;
	      datestr = argv[optind];
	      when = posixtime (datestr,
				PDS_TRAILING_YEAR | PDS_CENTURY | PDS_SECONDS);
	      format = NULL;
	    }
	  else
	    {
	      /* Prepare to print the current date/time.  */
	      datestr = _("undefined");
	      time (&when);
	      format = (n_args == 1 ? argv[optind] + 1 : NULL);
	    }
	}
      else
	{
	  /* (option_specified_date || set_date) */
	  if (reference != NULL)
	    {
	      if (stat (reference, &refstats))
		error (1, errno, "%s", reference);
	      when = refstats.st_mtime;
	    }
	  else
	    {
	      when = get_date (datestr, NULL);
	    }

	  format = (n_args == 1 ? argv[optind] + 1 : NULL);
	}

      if (when == -1)
	error (1, 0, _("invalid date `%s'"), datestr);

      if (set_date)
	{
	  /* Set the system clock to the specified date, then regardless of
	     the success of that operation, format and print that date.  */
	  if (stime (&when) == -1)
	    error (0, errno, _("cannot set date"));
	}

      /* When given a universal time option, set TZ to UTC0 after
	 parsing the specified date, but before printing it.  */
      MAYBE_SET_TZ_UTC0;

      show_date (format, when);
    }

  if (fclose (stdout) == EOF)
    error (2, errno, _("write error"));

  exit (status);
}

/* Display the date and/or time in WHEN according to the format specified
   in FORMAT, followed by a newline.  If FORMAT is NULL, use the
   standard output format (ctime style but with a timezone inserted). */

static void
show_date (const char *format, time_t when)
{
  struct tm *tm;
  char *out = NULL;
  size_t out_length = 0;

  tm = localtime (&when);

  if (format == NULL)
    {
      /* Print the date in the default format.  Vanilla ANSI C strftime
         doesn't support %e, but POSIX requires it.  If you don't use
         a GNU strftime, make sure yours supports %e.
	 If you are not using GNU strftime, you want to change %z
	 in the RFC format to %Z; this gives, however, an invalid
	 RFC time format outside the continental United States and GMT. */

      format = (rfc_format
		? (universal_time
		   ? "%a, %_d %b %Y %H:%M:%S GMT"
		   : "%a, %_d %b %Y %H:%M:%S %z")
		: "%a %b %e %H:%M:%S %Z %Y");
    }
  else if (*format == '\0')
    {
      printf ("\n");
      return;
    }

  do
    {
      out_length += 200;
      out = (char *) xrealloc (out, out_length);

      /* Mark the first byte of the buffer so we can detect the case
	 of strftime producing an empty string.  Otherwise, this loop
	 would not terminate when date was invoked like this
	 `LANG=de date +%p' on a system with good language support.  */
      out[0] = '\1';
    }
  while (strftime (out, out_length, format, tm) == 0 && out[0] != '\0');

  printf ("%s\n", out);
  free (out);
}

static void
usage (int status)
{
  if (status != 0)
    fprintf (stderr, _("Try `%s --help' for more information.\n"),
	     program_name);
  else
    {
      printf (_("\
Usage: %s [OPTION]... [+FORMAT]\n\
  or:  %s [OPTION] [MMDDhhmm[[CC]YY][.ss]]\n\
"),
	      program_name, program_name);
      printf (_("\
Display the current time in the given FORMAT, or set the system date.\n\
\n\
  -d, --date=STRING        display time described by STRING, not `now'\n\
  -f, --file=DATEFILE      like --date once for each line of DATEFILE\n\
  -r, --reference=FILE     display the last modification time of FILE\n\
  -R, --rfc-822            output RFC-822 compliant date string\n\
  -s, --set=STRING         set time described by STRING\n\
  -u, --utc, --universal   print or set Coordinated Universal Time\n\
      --help               display this help and exit\n\
      --version            output version information and exit\n\
"));
      printf (_("\
\n\
FORMAT controls the output.  The only valid option for the second form\n\
specifies Coordinated Universal Time.  Interpreted sequences are:\n\
\n\
  %%%%   a literal %%\n\
  %%a   locale's abbreviated weekday name (Sun..Sat)\n\
  %%A   locale's full weekday name, variable length (Sunday..Saturday)\n\
  %%b   locale's abbreviated month name (Jan..Dec)\n\
  %%B   locale's full month name, variable length (January..December)\n\
  %%c   locale's date and time (Sat Nov 04 12:02:33 EST 1989)\n\
  %%d   day of month (01..31)\n\
  %%D   date (mm/dd/yy)\n\
  %%e   day of month, blank padded ( 1..31)\n\
  %%h   same as %%b\n\
  %%H   hour (00..23)\n\
  %%I   hour (01..12)\n\
  %%j   day of year (001..366)\n\
  %%k   hour ( 0..23)\n\
  %%l   hour ( 1..12)\n\
  %%m   month (01..12)\n\
  %%M   minute (00..59)\n\
  %%n   a newline\n\
  %%p   locale's AM or PM\n\
  %%r   time, 12-hour (hh:mm:ss [AP]M)\n\
  %%s   seconds since 00:00:00, Jan 1, 1970 (a GNU extension)\n\
  %%S   second (00..61)\n\
  %%t   a horizontal tab\n\
  %%T   time, 24-hour (hh:mm:ss)\n\
  %%U   week number of year with Sunday as first day of week (00..53)\n\
  %%V   week number of year with Monday as first day of week (01..52)\n\
  %%w   day of week (0..6);  0 represents Sunday\n\
  %%W   week number of year with Monday as first day of week (00..53)\n\
  %%x   locale's date representation (mm/dd/yy)\n\
  %%X   locale's time representation (%%H:%%M:%%S)\n\
  %%y   last two digits of year (00..99)\n\
  %%Y   year (1970...)\n\
  %%z   RFC-822 style numeric timezone (-0500) (a nonstandard extension)\n\
  %%Z   time zone (e.g., EDT), or nothing if no time zone is determinable\n\
\n\
By default, date pads numeric fields with zeroes.  GNU date recognizes\n\
the following modifiers between `%%' and a numeric directive.\n\
\n\
  `-' (hyphen) do not pad the field\n\
  `_' (underscore) pad the field with spaces\n\
"));
      puts (_("\nReport bugs to <bug-sh-utils@gnu.org>."));
    }
  exit (status);
}