#!/usr/bin/perl -w
# Copyright (c) 2009-2013 Sullivan Beck.  All rights reserved.
# This program is free software; you can redistribute it and/or modify it
# under the same terms as Perl itself.

###############################################################################
###############################################################################

require 5.010000;
use Date::Manip::Date;
use IO::File;
use strict;
use warnings;

###############################################################################
# HELP
###############################################################################

our($usage);
my $COM = $0;
$COM =~ s/^.*\///;

$usage=
  "usage: $COM OPTIONS
      -h/--help        : Print help.

      Options to tell which date to print (only one of
      the following should be entered... if none are,
      'now' is printed).

      -d/--date=STRING : Print information about that date.
      -f/--file=FILE   : Print out each date (1/line) in FILE
      -r/--reference=FILE
                       : Print out the last modification
                         time of FILE

      Other options

      -R/--rfc-2822    : Print the date in RFC 2822 format
                         (any +FORMAT string is ignored)
                         Mon, 07 Aug 2006 12:34:56 -0600
      -u/--utc/--universal:
                         Converts date(s) to UT time.
";

=pod

=head1 NAME

dm_date - print out the system date and time

=head1 SYNOPSIS

This performs the same operation as the unix 'date' command, but using
the Date::Manip module.

   dm_date [OPTION]... [+FORMAT]

=head1 DESCRIPTION

This displays information about the current system time, or some
other time. Options are:

=over 4

=item -h, --help

Print online help.

=item -d STRING, --date=STRING

Display time described by STRING. STRING can be any string which can
be parsed by Date::Manip.  Please refer to the Date::Manip::Date
documentation for details.

=item -f DATEFILE, --file=DATEFILE

This reads each line in DATEFILE, and extracts a date from it and
prints out the information.

Blank lines and lines starting with a pound (#) are ignored. Lines
not containing a valid date are also ignored.

=item -r FILE, --reference=FILE

Displays the last modification time of FILE.

=item -R, --rfc-2822

Displayc the date and time in RFC 2822 format.

Example: Mon, 07 Aug 2006 12:34:56 -0600

=item -u, --utc, --universal

Converts the date to UT (GMT) and prints out the information.

=back

Only one of -d, -f, or -r should be included. If more than
one is included, the first one from the list (-d, -f, -r)
is used and any other is ignored.

The format string starts with a plus (+) and contains any
of the format directives described in Date::Manip::Date.

=head1 KNOWN BUGS

None known.

=head1 BUGS AND QUESTIONS

Please refer to the Date::Manip::Problems documentation for
information on submitting bug reports or questions to the author.

=head1 SEE ALSO

Date::Manip::Date

=head1 LICENSE

This script is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

=head1 AUTHOR

Sullivan Beck (sbeck@cpan.org)

=cut

###############################################################################
# PARSE ARGUMENTS
###############################################################################

our($date,$file,$ref,$rfc,$ut,$format);

while ($_ = shift) {

   (print $usage),   exit  if ($_ eq "-h"   ||  $_ eq "--help");

   $date = shift,    next  if ($_ eq "-d"   ||  $_ eq "--date");
   $date = $1,       next  if ($_ =~ /^\-\-date=(.*)/);

   $file = shift,    next  if ($_ eq "-f"   ||  $_ eq "--file");
   $file = $1,       next  if ($_ =~ /^\-\-file=(.*)/);

   $ref = shift,     next  if ($_ eq "-r"   ||  $_ eq "--reference");
   $ref = $1,        next  if ($_ =~ /^\-\-reference=(.*)/);

   $rfc = 1,         next  if ($_ eq "-R"   ||  $_ eq "--rfc-2822");
   $ut = 1,          next  if ($_ eq "-u"   ||  $_ eq "--utc"  ||  $_ eq "--universal");

   $format = $_,     last  if ($_ =~ s/^\+//);
   die $usage;
}

if ($rfc) {
   $format ='%a, %d %b %Y %H:%M:%S %z';
}

if (@ARGV  ||  ! $format) {
   die $usage;
}

############################################################################
# MAIN PROGRAM
############################################################################


my $d = new Date::Manip::Date;

if      ($date) {
   my $err = $d->parse($date);
   exit 1  if ($err);
   $d->convert("GMT")  if ($ut);
   print $d->printf($format),"\n";

} elsif ($file) {
   my $in = new IO::File;
   $in->open($file)  ||  die "ERROR: unable to open date file: $file\n\n$usage";
   my @in = <$in>;
   $in->close();
   chomp(@in);

   foreach my $date (@in) {
      $date =~ s/\#.*//;
      $date =~ s/\s*$//;
      next  if (! $date);

      my $err = $d->parse($date);
      next  if ($err);
      $d->convert("GMT")  if ($ut);
      print $d->printf($format),"\n";
   }

} elsif ($ref) {
   if (-e $ref) {
      my $date = ( stat($ref) )[9];
      my $err = $d->parse("epoch $date");
      exit  if ($err);
      $d->convert("GMT")  if ($ut);
      print $d->printf($format),"\n";
   }

} else {
   my $err = $d->parse("now");
   exit 1  if ($err);
   $d->convert("GMT")  if ($ut);
   print $d->printf($format),"\n";
}


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