/* date - print or set the system date and time
   Copyright (C) 1989-2003 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>
#if HAVE_LANGINFO_CODESET
# include <langinfo.h>
#endif

#include "system.h"
#include "argmatch.h"
#include "error.h"
#include "exitfail.h"
#include "getdate.h"
#include "getline.h"
#include "posixtm.h"
#include "posixver.h"
#include "quote.h"
#include "strftime.h"
#include "timespec.h"

/* The official name of this program (e.g., no `g' prefix).  */
#define PROGRAM_NAME "date"

#define AUTHORS "David MacKenzie"

int putenv ();

static void show_date (const char *format, struct timespec when);

enum Time_spec
{
  /* display only the date: 1999-03-25 */
  TIME_SPEC_DATE=1,
  /* display date and hour: 1999-03-25T03-0500 */
  TIME_SPEC_HOURS,
  /* display date, hours, and minutes: 1999-03-25T03:23-0500 */
  TIME_SPEC_MINUTES,
  /* display date, hours, minutes, and seconds: 1999-03-25T03:23:14-0500 */
  TIME_SPEC_SECONDS
};

static char const *const time_spec_string[] =
{
  "date", "hours", "minutes", "seconds", 0
};

static enum Time_spec const time_spec[] =
{
  TIME_SPEC_DATE, TIME_SPEC_HOURS, TIME_SPEC_MINUTES, TIME_SPEC_SECONDS
};

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

/* If nonzero, display an ISO 8601 format date/time string */
static int iso_8601_format = 0;

/* If non-zero, display time in RFC-(2)822 format for mail or news. */
static int rfc_format = 0;

#define COMMON_SHORT_OPTIONS "Rd:f:r:s:u"

static struct option const long_options[] =
{
  {"date", required_argument, NULL, 'd'},
  {"file", required_argument, NULL, 'f'},
  {"iso-8601", optional_argument, NULL, 'I'},
  {"reference", required_argument, NULL, 'r'},
  {"rfc-822", no_argument, NULL, 'R'},
  {"rfc-2822", no_argument, NULL, 'R'},
  {"set", required_argument, NULL, 's'},
  {"uct", no_argument, NULL, 'u'},
  {"utc", no_argument, NULL, 'u'},
  {"universal", no_argument, NULL, 'u'},
  {GETOPT_HELP_OPTION_DECL},
  {GETOPT_VERSION_OPTION_DECL},
  {NULL, 0, NULL, 0}
};

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

#ifdef _DATE_FMT
# define DATE_FMT_LANGINFO() nl_langinfo (_DATE_FMT)
#else
# define DATE_FMT_LANGINFO() ""
#endif

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 [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]\n\
"),
	      program_name, program_name);
      fputs (_("\
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\
  -ITIMESPEC, --iso-8601[=TIMESPEC]  output date/time in ISO 8601 format.\n\
                            TIMESPEC=`date' for date only,\n\
                            `hours', `minutes', or `seconds' for date and\n\
                            time to the indicated precision.\n\
                            --iso-8601 without TIMESPEC defaults to `date'.\n\
"), stdout);
      fputs (_("\
  -r, --reference=FILE      display the last modification time of FILE\n\
  -R, --rfc-2822            output RFC-2822 compliant date string\n\
  -s, --set=STRING          set time described by STRING\n\
  -u, --utc, --universal    print or set Coordinated Universal Time\n\
"), stdout);
      fputs (HELP_OPTION_DESCRIPTION, stdout);
      fputs (VERSION_OPTION_DESCRIPTION, stdout);
      fputs (_("\
\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\
"), stdout);
      fputs (_("\
  %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\
"), stdout);
      fputs (_("\
  %C   century (year divided by 100 and truncated to an integer) [00-99]\n\
  %d   day of month (01..31)\n\
  %D   date (mm/dd/yy)\n\
  %e   day of month, blank padded ( 1..31)\n\
"), stdout);
      fputs (_("\
  %F   same as %Y-%m-%d\n\
  %g   the 2-digit year corresponding to the %V week number\n\
  %G   the 4-digit year corresponding to the %V week number\n\
"), stdout);
      fputs (_("\
  %h   same as %b\n\
  %H   hour (00..23)\n\
  %I   hour (01..12)\n\
  %j   day of year (001..366)\n\
"), stdout);
      fputs (_("\
  %k   hour ( 0..23)\n\
  %l   hour ( 1..12)\n\
  %m   month (01..12)\n\
  %M   minute (00..59)\n\
"), stdout);
      fputs (_("\
  %n   a newline\n\
  %N   nanoseconds (000000000..999999999)\n\
  %p   locale's upper case AM or PM indicator (blank in many locales)\n\
  %P   locale's lower case am or pm indicator (blank in many locales)\n\
  %r   time, 12-hour (hh:mm:ss [AP]M)\n\
  %R   time, 24-hour (hh:mm)\n\
  %s   seconds since `00:00:00 1970-01-01 UTC' (a GNU extension)\n\
"), stdout);
      fputs (_("\
  %S   second (00..60); the 60 is necessary to accommodate a leap second\n\
  %t   a horizontal tab\n\
  %T   time, 24-hour (hh:mm:ss)\n\
  %u   day of week (1..7);  1 represents Monday\n\
"), stdout);
      fputs (_("\
  %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..53)\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\
"), stdout);
      fputs (_("\
  %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\
"), stdout);
      fputs (_("\
  %z   RFC-2822 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\
"), stdout);
      printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
    }
  exit (status);
}

/* 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;
  struct timespec when;

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

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

      when.tv_sec = get_date (line, NULL);
      when.tv_nsec = 0; /* FIXME: get_date should set this.  */

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

  if (fclose (in_stream) == EOF)
    error (2, errno, "%s", quote (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;
  struct timespec 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;
  char const *short_options = (posix2_version () < 200112
			       ? COMMON_SHORT_OPTIONS "I::"
			       : COMMON_SHORT_OPTIONS "I:");

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

  exit_failure = 2;
  atexit (close_stdout);

  while ((optc = getopt_long (argc, argv, short_options, long_options, NULL))
	 != -1)
    switch (optc)
      {
      case 0:
	break;
      case 'd':
	datestr = optarg;
	break;
      case 'f':
	batch_file = optarg;
	break;
      case 'I':
	iso_8601_format = (optarg
			   ? XARGMATCH ("--iso-8601", optarg,
					time_spec_string, time_spec)
			   : TIME_SPEC_DATE);
	break;
      case 'r':
	reference = optarg;
	break;
      case 'R':
	rfc_format = 1;
	break;
      case 's':
	set_datestr = optarg;
	set_date = 1;
	break;
      case 'u':
	/* POSIX says that `date -u' is equivalent to setting the TZ
	   environment variable, so this option should do nothing other
	   than setting TZ.  */
	if (putenv ("TZ=UTC0") != 0)
	  xalloc_die ();
	TZSET;
	break;
      case_GETOPT_HELP_CHAR;
      case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
      default:
	usage (EXIT_FAILURE);
      }

  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 (EXIT_FAILURE);
    }

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

  if (n_args > 1)
    {
      error (0, 0, _("too many non-option arguments: %s%s"),
	     argv[optind + 1], n_args == 2 ? "" : " ...");
      usage (EXIT_FAILURE);
    }

  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 (EXIT_FAILURE);
    }

  /* Simply ignore --rfc-2822 if specified when setting the date.  */
  if (rfc_format && !set_date && n_args > 0)
    {
      error (0, 0,
	     _("a format string may not be specified when using\
 the --rfc-2822 (-R) option"));
      usage (EXIT_FAILURE);
    }

  if (set_date)
    datestr = set_datestr;

  if (batch_file != NULL)
    {
      status = batch_convert (batch_file,
			      (n_args == 1 ? argv[optind] + 1 : NULL));
    }
  else
    {
      bool valid_date = true;
      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];
	      valid_date = posixtime (&when.tv_sec,
				      datestr,
				      (PDS_TRAILING_YEAR
				       | PDS_CENTURY | PDS_SECONDS));
	      when.tv_nsec = 0; /* FIXME: posixtime should set this.  */
	      format = NULL;
	    }
	  else
	    {
	      /* Prepare to print the current date/time.  */
	      datestr = _("undefined");
	      if (gettime (&when) != 0)
		error (EXIT_FAILURE, errno, _("cannot get time of day"));
	      format = (n_args == 1 ? argv[optind] + 1 : NULL);
	    }
	}
      else
	{
	  /* (option_specified_date || set_date) */
	  if (reference != NULL)
	    {
	      if (stat (reference, &refstats))
		error (EXIT_FAILURE, errno, "%s", reference);
	      when.tv_sec = refstats.st_mtime;
	      when.tv_nsec = TIMESPEC_NS (refstats.st_mtim);
	    }
	  else
	    {
	      when.tv_sec = get_date (datestr, NULL);
	      when.tv_nsec = 0; /* FIXME: get_date should set this.  */
	      valid_date = (when.tv_sec != (time_t) -1);
	    }

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

      if (! valid_date)
	error (EXIT_FAILURE, 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 (settime (&when) != 0)
	    {
	      error (0, errno, _("cannot set date"));
	      status = 1;
	    }
	}

      show_date (format, when);
    }

  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, struct timespec when)
{
  struct tm *tm;
  char *out = NULL;
  size_t out_length = 0;
  /* ISO 8601 formats.  See below regarding %z */
  static char const * const iso_format_string[] =
  {
    "%Y-%m-%d",
    "%Y-%m-%dT%H%z",
    "%Y-%m-%dT%H:%M%z",
    "%Y-%m-%dT%H:%M:%S%z"
  };

  tm = localtime (&when.tv_sec);

  if (format == NULL)
    {
      if (rfc_format)
	format = "%a, %d %b %Y %H:%M:%S %z";
      else if (iso_8601_format)
	format = iso_format_string[iso_8601_format - 1];
      else
	{
	  char *date_fmt = DATE_FMT_LANGINFO ();
	  /* Do not wrap the following literal format string with _(...).
	     For example, suppose LC_ALL is unset, LC_TIME="POSIX",
	     and LANG="ko_KR".	In that case, POSIX says that LC_TIME
	     determines the format and contents of date and time strings
	     written by date, which means "date" must generate output
	     using the POSIX locale; but adding _() would cause "date"
	     to use a Korean translation of the format.  */
	  format = *date_fmt ? date_fmt : "%a %b %e %H:%M:%S %Z %Y";
	}
    }
  else if (*format == '\0')
    {
      printf ("\n");
      return;
    }

  while (1)
    {
      int done;
      out = x2nrealloc (out, &out_length, sizeof *out);

      /* Mark the first byte of the buffer so we can detect the case
	 of nstrftime 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';

      if (rfc_format)
	setlocale (LC_ALL, "C");

      done = (nstrftime (out, out_length, format, tm, 0, when.tv_nsec)
	      || out[0] == '\0');

      if (rfc_format)
	setlocale (LC_ALL, "");

      if (done)
	break;
    }

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