#! @PERL@

use warnings;

#  This script is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License version 2 as
#  published by the Free Software Foundation.
#
#  See the COPYING and AUTHORS files for more details.

use strict;
use POSIX qw(strftime);
use Getopt::Long qw(:config gnu_getopt prefix_pattern=(--|-));
use Date::Parse;

my $spec = '%a %b %e %H:%M:%S %Z %Y';
my $now  = time();
my $utc = 0;

sub usage() {
    print "Usage: date [OPTION]... [+FORMAT]
Display the current time in the given FORMAT.

  -d, --date=STRING         display time described by STRING, not `now'
  -f, --file=DATEFILE       like --date once for each line of DATEFILE
  -R, --rfc-822             output RFC-822 compliant date string
  -u, --utc, --universal    print or set Coordinated Universal Time
      --help                display this help and exit
";
    exit 1;
}

sub parse_utc_secs($) {
    my ($now) = @_;

    if ($now =~ / UTC ([0-9]+) seconds$/) {
	# This is an heuristic specifically for quilts mail.in invocation:
	#   date --rfc-822 -d "1970/01/01 UTC nnnnnnnn seconds"
	return $1;
    }
    else {
	return str2time($now);
    }
}

GetOptions('rfc-822|R' => sub() { $spec = '%a, %d %b %Y %H:%M:%S %z' },
	   'utc|universal|u' => \$utc,
	   'date|d=s' => sub() { $now = parse_utc_secs($_[1]) },
	   'reference|r=s' => sub() { my @filestats = stat($_[1]); $now = parse_utc_secs('1970/01/01 UTC ' . $filestats[9] . ' seconds') },
	   'help|h' => sub() { usage })
    or usage;

if (@ARGV == 1 && $ARGV[0] =~ /^\+/) {
    $spec = substr($ARGV[0], 1);
} elsif (@ARGV > 1) {
   usage;
}

my @now = $utc ? gmtime($now) : localtime($now);

print strftime($spec, @now) . "\n";