#!/usr/bin/perl -w
# filechangeserver - watches a file and reports howmany lines or bytes have been added
# released under GPL by Paul Mansfield November 2011.
# no warranty provided, no tin will be supplied labelled with a promise 
# to do anything, no animals should be harmed in the use of this script,
# your mileage may vary, and your karma may increase.

use strict;
use Fcntl;

use IO::Select;
use IO::Socket;


#############################################################################
# constants
my $pidFile = '/var/run/filechangeserver.pid';


#############################################################################
# command line options
# error checking? we don't need no stinkeeng error checking

my $dbgLevel = 0;
my $listenPort;
my $tailfile;

while (($#ARGV >= 0) && ($ARGV[0] eq '-d'))
{
    ++$dbgLevel;
    shift;
}

if ( $#ARGV < 1 )
{
    print STDERR "Usage:\nfilechangeserver [-d] port file\n\n";
    exit
}

$listenPort = $ARGV[0];
$tailfile = $ARGV[1];


#############################################################################
sub deletePidFile
{
    if (!unlink "$pidFile")
    {
        print STDERR "Error, failed to delete $pidFile\n";
    }
}


#############################################################################
sub writePidFile
{
    open(PIDFILE, ">$pidFile") or die "Error, failed to open $pidFile for writing";

    print PIDFILE $$;

    close PIDFILE;
}

#############################################################################
sub openTailFile
{
    # use sysopen for the tail file to get nonblocking read
    return sysopen(TF, "$tailfile", O_RDONLY|O_NONBLOCK);

}

#############################################################################
#############################################################################
# main program

#$SIG{HUP} = 'catchSignalHup';	# could fail in modules
$SIG{HUP} = \&catchSignalHup;  # best strategy 
$SIG{INT} = \&catchSignalInt;  # best strategy 


openTailFile() || die "Error, failed to open $tailfile for reading";

# use sysopen for the tail file to get nonblocking read
sysopen(TF, "$tailfile", O_RDONLY|O_NONBLOCK) or die "Error, failed to open $tailfile for reading";

# create a listening socket on the user specified port
my $sock = new IO::Socket::INET (
			LocalPort => $listenPort
			, Proto => 'tcp'
			, Listen => 1
			, Reuse => 1
		       );
die "could not create socket: $!\n" unless $sock;


# get the current file stat
my ($tf_cur_dev,$tf_cur_ino,$tf_cur_mode,$tf_cur_nlink,$tf_cur_uid,$tf_cur_gid,$tf_cur_rdev,$tf_cur_size, $tf_cur_atime,$tf_cur_mtime,$tf_cur_ctime,$tf_cur_blksize,$tf_cur_blocks) = stat(TF);


seek(TF, 0, 2);			    # seek to end of file
my $oldTime = time();

my $read_set = new IO::Select();    # create handle set for reading
$read_set->add($sock);		    # add the main socket to the set

#############################################################################
# program loop

writePidFile();

my $requestType = '';
my $newSock;                # needs to be global so can close it on SIGINT

my $httpHost = 'ERROR';

while (1) # forever
{
    print STDERR "beginning of program infinite loop\n" if ($dbgLevel > 1);
    if (! ($newSock = $sock->accept()) ) 	# ignore a HUP
    {
	next();
    }
    print STDERR "accepted socket connection\n" if ($dbgLevel > 1);
    my $newTime = time();	    # take the sample immediately
    # don't buffer, flush immediately on writing
    $newSock->autoflush();
    # don't block when reading from socket
    my $sockFlags = fcntl($newSock, F_GETFL, 0);
    fcntl(TF, F_SETFL, $sockFlags | O_NONBLOCK);

    # read the request, ignore all except the GET line which we want for the URI
    while(<$newSock>) # && !$blankLineFlag)
    {
	chomp;
	chop if (substr($_, length($_) - 1, 1) eq "\r");
	print STDERR ">>$_<<\n" if ($dbgLevel > 0);

	# extract the host
	if ($_ =~ /^Host: (.*)/)
	{
		$httpHost = $1;
	}
	# extract the URI
	elsif ($_ =~ /^GET (.*) HTTP.*/)
	{
		#print STDERR ">>$_<<\n" if ($dbgLevel > 1);
	    if ($1 eq "/bytes")
	    {
		$requestType = "bytes";
	    }
	    elsif ($1 eq "/ajaxpage")
	    {
		$requestType = "ajaxpage";
	    }
	    elsif ($1 eq "/lines")
	    {
		$requestType = "lines";
	    }
	    elsif ($1 eq "/linespersec")
	    {
		$requestType = "linespersec";
	    }
	}

	elsif ($_ eq "")    # request terminates with a blank line
	{
	    #print STDERR "<< exit >>\n" if ($dbgLevel > 1);
	    last;
	}
    }

    # print response headers (mostly fake) - they don't actually matter
    print $newSock "HTTP/1.0 200 OK\r\n";
    print $newSock "Date: Tue, 08 Jun 2010 13:46:38 GMT\r\n";
    print $newSock "Expires: Tue, 08 Jun 2010 13:46:38 GMT\r\n";
    print $newSock "Last-Modified: Tue, 08 Jun 2010 13:46:38 GMT\r\n";
    print $newSock "Cache-Control: private, must-revalidate, max-age=0\r\n";

    if ($requestType eq 'ajaxpage')
    {
	print $newSock "Content-type: text/html\r\n\r\n";
    }
    else
    {
	print $newSock "Content-type: text/plain\r\n\r\n";
    }

    # get files's current state from the file handle
    my ($tf_new_dev,$tf_new_ino,$tf_new_mode,$tf_new_nlink,$tf_new_uid,$tf_new_gid,$tf_new_rdev,$tf_new_size, $tf_new_atime,$tf_new_mtime,$tf_new_ctime,$tf_new_blksize,$tf_new_blocks) = stat(TF);
    
    # check if file has grown
    my $countNewLines = 0;
    # scan for new lines to effectively seek to end of file
    if ($tf_new_size - $tf_cur_size > 0)
    {
	while (<TF>)
	{  
	    ++$countNewLines;
	    #print $newSock $_;
	    #print STDERR "Growth $countNewLines: $_" if ($dbgLevel > 1);
	}
    }

    if ($requestType eq 'lines')
    {
	print $newSock $countNewLines . "\r\n";
    }
    elsif ($requestType eq 'linespersec')
    {
	my $deltaTime = ($newTime - $oldTime);
	$deltaTime = 1 if ($deltaTime == 0);
	print $newSock ( (int (10 * $countNewLines / $deltaTime) / 10.0) ) . "\r\n";
    }
    elsif ($requestType eq 'bytes')
    {
	print $newSock ($tf_new_size - $tf_cur_size) . "\r\n";
    }
    elsif ($requestType eq 'ajaxpage')
    {
	writeAjaxPage();
    }
    else
    {
	print $newSock "file has grown by " . ($tf_new_size - $tf_cur_size) . " bytes and $countNewLines lines\r\n";
    }
    close($newSock);

    ($tf_cur_dev,$tf_cur_ino,$tf_cur_mode,$tf_cur_nlink,$tf_cur_uid,$tf_cur_gid,$tf_cur_rdev,$tf_cur_size, $tf_cur_atime,$tf_cur_mtime,$tf_cur_ctime,$tf_cur_blksize,$tf_cur_blocks) = ($tf_new_dev,$tf_new_ino,$tf_new_mode,$tf_new_nlink,$tf_new_uid,$tf_new_gid,$tf_new_rdev,$tf_new_size, $tf_new_atime,$tf_new_mtime,$tf_new_ctime,$tf_new_blksize,$tf_new_blocks);
    $oldTime = $newTime;
}


##############################################################################
sub catchSignalInt
{
    my $sigName = shift;

    $SIG{INT} = \&catchSignalInt;  # refresh signal handler

    #close($newSock);           # would need to check it was open
    close($sock);
    close(TF);
    deletePidFile();

    die("filechangeserver killed by sigint");
}

#############################################################################
sub catchSignalHup
{
    my $sigName = shift;
    print STDERR "\nHUP\n";

    close(TF);
    openTailFile() || die "Error, failed to open $tailfile for reading";

    # jump to the end of the current version of the file
    my ($tf_new_dev,$tf_new_ino,$tf_new_mode,$tf_new_nlink,$tf_new_uid,$tf_new_gid,$tf_new_rdev,$tf_new_size, $tf_new_atime,$tf_new_mtime,$tf_new_ctime,$tf_new_blksize,$tf_new_blocks) = stat(TF);
    ($tf_cur_dev,$tf_cur_ino,$tf_cur_mode,$tf_cur_nlink,$tf_cur_uid,$tf_cur_gid,$tf_cur_rdev,$tf_cur_size, $tf_cur_atime,$tf_cur_mtime,$tf_cur_ctime,$tf_cur_blksize,$tf_cur_blocks) = ($tf_new_dev,$tf_new_ino,$tf_new_mode,$tf_new_nlink,$tf_new_uid,$tf_new_gid,$tf_new_rdev,$tf_new_size, $tf_new_atime,$tf_new_mtime,$tf_new_ctime,$tf_new_blksize,$tf_new_blocks);
    my $newTime = time();
    $oldTime = $newTime;

    #$SIG{HUP} = 'catchSignalHup';  # could fail in modules
    $SIG{HUP} = \&catchSignalHup;  # best strategy 
}


##############################################################################
sub writeAjaxPage
{
    print $newSock <<EOF
<html>
		<head><title>Log Rate</title></head>
		<body style="background-color: #fff; " >
			<div id="boxGasGauge" style="border: 1px solid #888; width: 300px; height: 50px;">
				<div id="gasGauge" style="width: 50px; background-color: #a33; height: 50px;" ></div>
			</div>
	    <div id="boxGasNumber"  style="border: 0px solid #888; width: 100px; height: 50px;">
			<div id="gasNumber" width: 300px; height: 50px;" >value goes here</div>
	    </div>

<script type="text/javascript">
var looptime = 3000; // loop time in ms

function doupdate() {

	var url = "http://$httpHost/linespersec";
	var width = 300; // the width of the gasGauge
	var maxVal = 50; // the max number returned as lps

	var handleSuccess = function( linesPerSec ){
		if ( linesPerSec !== undefined ){
			try {
				if ( linesPerSec > -1 ) {
					var nWid = width * ( linesPerSec / maxVal );
					var el = document.getElementById( "gasGauge" );
					el.style.width = nWid + "px";
					el = document.getElementById( "gasNumber" );
					el.firstChild.data = linesPerSec;
				}
			}
			catch (e) {	
				// NaN
			}
			
		}
		setTimeout( doupdate, looptime );
	}
		
	var request = new XMLHttpRequest();
	request.onreadystatechange = function() {
		if ( request.readyState == 4 ) {
			if ( request.status == 200 ) {
				handleSuccess( request.responseText );
			}
		}
	}
	request.open( "GET", url, true );
	request.send( null );
}

setTimeout( doupdate, looptime ); // kick off the loop first time
</script>
		</body>
</html>

EOF
}

# end of filechangeserver.pl