package HTTP::Date;

$VERSION = "5.810";

require 5.004;
require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw(time2str str2time);
@EXPORT_OK = qw(parse_date time2iso time2isoz);

use strict;
require Time::Local;

use vars qw(@DoW @MoY %MoY);
@DoW = qw(Sun Mon Tue Wed Thu Fri Sat);
@MoY = qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec);
@MoY{@MoY} = (1..12);

my %GMT_ZONE = (GMT => 1, UTC => 1, UT => 1, Z => 1);


sub time2str (;$)
{
    my $time = shift;
    $time = time unless defined $time;
    my ($sec, $min, $hour, $mday, $mon, $year, $wday) = gmtime($time);
    sprintf("%s, %02d %s %04d %02d:%02d:%02d GMT",
	    $DoW[$wday],
	    $mday, $MoY[$mon], $year+1900,
	    $hour, $min, $sec);
}


sub str2time ($;$)
{
    my $str = shift;
    return undef unless defined $str;

    # fast exit for strictly conforming string
    if ($str =~ /^[SMTWF][a-z][a-z], (\d\d) ([JFMAJSOND][a-z][a-z]) (\d\d\d\d) (\d\d):(\d\d):(\d\d) GMT$/) {
	return eval {
	    my $t = Time::Local::timegm($6, $5, $4, $1, $MoY{$2}-1, $3);
	    $t < 0 ? undef : $t;
	};
    }

    my @d = parse_date($str);
    return undef unless @d;
    $d[1]--;        # month

    my $tz = pop(@d);
    unless (defined $tz) {
	unless (defined($tz = shift)) {
	    return eval { my $frac = $d[-1]; $frac -= ($d[-1] = int($frac));
			  my $t = Time::Local::timelocal(reverse @d) + $frac;
			  $t < 0 ? undef : $t;
		        };
	}
    }

    my $offset = 0;
    if ($GMT_ZONE{uc $tz}) {
	# offset already zero
    }
    elsif ($tz =~ /^([-+])?(\d\d?):?(\d\d)?$/) {
	$offset = 3600 * $2;
	$offset += 60 * $3 if $3;
	$offset *= -1 if $1 && $1 eq '-';
    }
    else {
	eval { require Time::Zone } || return undef;
	$offset = Time::Zone::tz_offset($tz);
	return undef unless defined $offset;
    }

    return eval { my $frac = $d[-1]; $frac -= ($d[-1] = int($frac));
		  my $t = Time::Local::timegm(reverse @d) + $frac;
		  $t < 0 ? undef : $t - $offset;
		};
}


sub parse_date ($)
{
    local($_) = shift;
    return unless defined;

    # More lax parsing below
    s/^\s+//;  # kill leading space
    s/^(?:Sun|Mon|Tue|Wed|Thu|Fri|Sat)[a-z]*,?\s*//i; # Useless weekday

    my($day, $mon, $yr, $hr, $min, $sec, $tz, $ampm);

    # Then we are able to check for most of the formats with this regexp
    (($day,$mon,$yr,$hr,$min,$sec,$tz) =
        /^
	 (\d\d?)               # day
	    (?:\s+|[-\/])
	 (\w+)                 # month
	    (?:\s+|[-\/])