#!/usr/bin/perl
#
# code taken from this page:
# http://oreilly.com/openbook/cgi/ch06_04.html
#
# ------------------------------------------------------
$nsamples = 72; # number of x-axis values in my graph
$maxok=75; # Ok values are between 0 and this value
$maxwarn=200; # Warning values are between $maxok and this value

$webmaster = "jose\@nic-nac-project\.de";
$gnuplot  = "/usr/bin/gnuplot";
$ppmtogif = "/usr/bin/ppmtogif";
$real_log = "sqlprau.log";

$process_id = $$;
$output_ppm = join ("", "temp_", $process_id, ".ppm");
$datafile = join ("", "temp_", $process_id, ".txt");
$access_log = join ("", "temp_", $process_id, ".log");

$x = 0.8;
$y = 0.6;
$color = 1; 

$ncrit = 0;
$nwarn = 0;
$nok = 0;
$ymax = 0;

system ("tail -$nsamples $real_log > $access_log 2> /dev/null");
if ( open (FILE, "<" . $access_log) ) {
    for ($loop=0; $loop < $nsamples; $loop++) { $time[$loop] = 0; }

    $i = 0;
    while (<FILE>) {
	if ($i >= $nsamples) { goto breakloop } ;
        if (m|(.*) - (.*) - ([0-9]*)|) {
             $time[$nsamples - $i] = $3;
	     if ($time[$nsamples - $i] > $maxwarn) {
	     	$ncrit++;
	     }
	     else {
		     if ($time[$nsamples - $i] > $maxok) {
			$nwarn++;
		     }
		     else {
		     	$nok++;
		     }
	     }
	     if ($time[$nsamples - $i] > $ymax) {
	     	$ymax = $time[$nsamples - $i];
	     }
	     $i++;
        }
    }
    breakloop: close (FILE);
    &create_output_file();

} else {
    &return_error(500, "Server Log File Error", "Cannot open input data file.");
}
exit(0);


sub create_output_file 
{
    local ($loop);
    if ( (open (FILE, ">" . $datafile)) ) {
        for ($loop=0; $loop < $nsamples; $loop++) {
        print FILE $loop, " ", $time[$loop], "\n";
        }
        close (FILE);
        
        &send_data_to_gnuplot();
    } else {
        &return_error (500, "Server Log File Error", "Cannot write to data file!");
    }
}


sub send_data_to_gnuplot
{
    my $period = 10;
    my $xhours = ($nsamples * 10 / 60);

    open (GNUPLOT, "|$gnuplot");
    print GNUPLOT <<gnuplot_Commands_Done;

    set term pbm color small
    set output "$output_ppm"
    set size $x, $y
    set title "HTTP time response"
    set xlabel "Last measurements: period = $period minutes, $nsamples lines = $xhours hours"
    set ylabel "milliseconds" 
    set xrange [$nsamples:-1]
    set xtic 6
    set noxzeroaxis
    set noyzeroaxis
    set border
    set nogrid
    set nokey
    set style fill   pattern 2 border 1
    set object 1 rect from -1,$maxok to $nsamples,$maxwarn fc lt 3 fillstyle solid 0.70 border -1
    set label 1 "$ncrit values greater than $maxwarn ms" at $nsamples-2,$ymax-50 front
    set label 2 "$nwarn values between $maxok and $maxwarn ms" at $nsamples-2,$ymax-100 front
    set label 3 "$nok values lower than $maxok" at $nsamples-2,$ymax-150 front
    plot "$datafile" w boxes $color
gnuplot_Commands_Done
close (GNUPLOT);

        &print_gif_file_and_cleanup();
}

# --------------------------------------------------------------------
# The print_gif_file_and_cleanup subroutine displays this image,
#    and removes the temporary files.
sub print_gif_file_and_cleanup
{
    $| = 1;
    print "Content-type: image/gif", "\n\n";
    system ("$ppmtogif $output_ppm 2> /dev/null");
    unlink $output_ppm, $datafile, $access_log ;
}