#!/usr/bin/perl -w
#
# Gets the room stats for bc07 and extracts a random subset of available hosts.
#
use strict;
use HTTP::Request::Common;
use HTTP::Response;
use LWP::UserAgent;

my $pctype = "linux"; # Which pcs to display

my $sample_size = "10";

# First, get the sample size and whether to get linux pcs or windows pcs
if( $#ARGV == 1 ) {
    if( $ARGV[0] eq "linux" ) {
	$pctype = "linux";
    } elsif ( $ARGV[0] eq "windows" ) {
	$pctype = "windows";
    } else {
	usage();
	die "You have to choose to display either windows or linux pcs\n";
    }

    $sample_size = 0 + $ARGV[1];
    if( $sample_size <= 0 ) {
	usage();
	die "You have to specify a positive sample size\n";
    }
}

# Now get the webpage
my $ua = LWP::UserAgent->new;

my $icbc_url = "http://ic-it.epfl.ch/it/sallesinfo/bc0708/bc0708_users.html";

my $response = $ua->request(GET $icbc_url);

if ( $response->is_success ) {
    my $current_pc;
    my @windows_pcs = ();
    my @linux_pcs = ();

    for my $line (split("\n",$response->content)) {
	if( $line =~ m!<font color="black"><B>([^<]*)</B></font>! ) {
	    $current_pc = $1;
	}
	if( $line =~ /Windows/ ) {
	    push @windows_pcs,$current_pc;
	}
	if( $line =~ /Linux/ ) {
	    push @linux_pcs,$current_pc;
	}
    }

    my @sample = ();
    if( $pctype eq "linux" ) {
	@sample = get_sample($sample_size,@linux_pcs);
    } else {
	@sample = get_sample($sample_size,@windows_pcs);
    }
    print join("\n",@sample);
    print "\n";
} else {
    die "Failed to download computer listing";
}

sub get_sample {
    my $size = shift;
    my @elems = @_;
    if( $#elems < $size ) {
	$size = $#elems + 1; # We can't deliver as many elements as we want.
    }

    my @ret = ();
    # Now permute the first $size elements
    for( my $i = 0; $i < $size; $i++ ) {
	my $rpos = int(rand($#elems - $size));
	push @ret,$elems[$rpos + $i];
	$elems[$rpos + $i] = $elems[$i]; # The unused element at the old position
    }

    return @ret;
}

sub usage {
    print "usage: ./stats.pl windows|linux 10\n";
}