#! /usr/bin/perl

use Tk;

my $sysWIDTH = 400;
my $sysFATNESS = 1;
my $sysHEIGHT = 200;
my $sysM = $sysWIDTH / 2;
my $sysWARN = 0.4 * $sysHEIGHT;
my $sysXHEIGHT = $sysHEIGHT / 4;

my $sysi = 0;
my @sysB = ();
my @sysR = ();
my ($sysj, $sysk, $sysx, $sysy, $sysy_);
my $sysCOLOR = '#00ff00';

my $sysd;
my ($sysmw, $sysb, $sysc);

sub
do_sysload
{
   my $sysmw = $_[0];
   $sysmw->configure(-title => "Sysload: System Load Graph");
   $sysc = $sysmw->Canvas(
     -width => $sysWIDTH,
     -height => $sysHEIGHT,
     -background => 'black',
     -relief => 'sunken',
     -borderwidth => '1',
   )->pack(-fill => 'both', -expand => '1');

   for ($sysj = 0; $sysj < $sysM; $sysj++) {
     $sysB[$sysj] = 0;
   }
   $sysb = $sysmw->Button(
     -command => sub { update_status(); },
     -text => "Load Average",
   )->pack;
}

sub
update_status
{
  open(F,"</proc/loadavg");
  ($_, undef) = split(' ', <F>);
  close(F);
  $sysB[$sysi] = $_;
  for ($sysj = 0; $sysj < $sysM; $sysj++) {
    $sysk = ($sysj + $sysi) % $sysM;
    $sysc->delete($sysR[$sysk]);
    $sysx = $sysj * $sysFATNESS;
    $sysy = $sysXHEIGHT * $sysB[$sysk];
    $sysy_ = $sysXHEIGHT * $sysB[($sysk - 1) % $sysM];
    if ($sysy > $sysWARN) {
      $sysCOLOR = '#ff5050';
    } else {
      $sysCOLOR = '#00ff00';
    }
    $sysR[$sysk] = $sysc->create(
      'polygon',
      $sysx, $sysHEIGHT, $sysx + $sysFATNESS, $sysHEIGHT,
      $sysx + $sysFATNESS, $sysHEIGHT - $sysy, $sysx, $sysHEIGHT - $sysy_,
        -fill => $sysCOLOR,
        -smooth => '1',
        -outline => undef,
    );
  }
  $sysi = ($sysi + 1) % $sysM;
  after(750, [\&update_status]);
}

my $mw = new MainWindow;
do_sysload($mw);
MainLoop;
1;
__END__