#!/usr/bin/perl

use XML::DOM;
use strict;

# get the first element under a node of the given tag
# @param node: node under which to look for elements
# @param tag: the tage to look for
# @return: first element under node with the given tag
sub subvalue($$)
{
    my ($class, $tag) = @_;
    return value($class->getElementsByTagName($tag)->item(0));
}

# get the node value of the first child of a given node
# @param node: whose child to use
# @return: node value of given node's first child
sub value($)
{
    my ($class) = @_;
    if (undef == $class) { return undef; }

    my $child = $class->getFirstChild();

    if (undef == $child) {
        return undef;
    }

    return $child->getNodeValue();
}

print <<END_OF_FILE;
BEGIN:VCALENDAR
VERSION:2.0
X-WR-CALNAME:University of Waterloo Computer Science Club
PRODID:-//Apple Computer\, Inc//iCal 2.0//EN
X-WR-RELCALID:3359A191-B19E-4B53-BADC-DFC084FC51C9
X-WR-TIMEZONE:Canada/Eastern
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VTIMEZONE
TZID:Canada/Eastern
LAST-MODIFIED:20060912T200739Z
BEGIN:DAYLIGHT
DTSTART:20060301T070000
TZOFFSETTO:-0400
TZOFFSETFROM:+0000
TZNAME:EDT
END:DAYLIGHT
BEGIN:STANDARD
DTSTART:20061029T020000
TZOFFSETTO:-0500
TZOFFSETFROM:-0400
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:20070311T010000
TZOFFSETTO:-0400
TZOFFSETFROM:-0500
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE
END_OF_FILE

my $parser = XML::DOM::Parser->new();
my $doc = $parser->parsefile($ARGV[0]);
my @events = $doc->getElementsByTagName("eventitem");

foreach my $event (@events) {
    my $date = $event->getAttribute("date");
    my $time = $event->getAttribute("time");
    my $talk_title = $event->getAttribute("title");
    $talk_title =~ s/[:;,]//g;

    my $room = $event->getAttribute("room");

    my $short = subvalue($event, "short");
    $short =~ s/[:;,]//g;
    my $abstract = $event->getElementsByTagName("abstract")->item(0)->toString();

    my $ical_date = `date -d"$date" +%Y%m%d`;
    chomp $ical_date;

    my ($ical_start, $ical_end);

    if ($time =~ /(.*)-(.*)/) {
        $ical_start = ical_time($1);
        $ical_end = ical_time($2);
    } else {
        $ical_start = ical_time($time);
        $ical_end = ical_time("$time + 1 hour");
    }

    $abstract =~ s/<abstract>//;
    $abstract =~ s/<\/abstract>//;
    $abstract =~ s/\n/ /sg;

    my $ical_abstract = "\"$abstract\"";

sub ical_time {
    my ($ds) = @_;
    my $d = `date -d"$ds" +\%H\%M\%S`;
    chomp $d;
    return $d;
} 

print <<END_OF_EVENT;

BEGIN:VEVENT
LOCATION:University of Waterloo - $room
DTSTAMP:20060912T200708Z
UID:${ical_date}T${ical_start}\@csclub.uwaterloo.ca
SEQUENCE:11
DTSTART;TZID=Canada/Eastern:${ical_date}T${ical_start}
DTEND;TZID=Canada/Eastern:${ical_date}T${ical_end}
SUMMARY:<a href=http://www.csclub.uwaterloo.ca>$talk_title</a> -- $short
DESCRIPTION:$ical_abstract 
END:VEVENT
END_OF_EVENT
}

print "END:VCALENDAR\n";