#!/usr/bin/perl -w
# Got from http://poe.perl.org/?POE_Cookbook/Watching_Logs

use POE qw/Wheel::FollowTail/;
use strict;

$| = 1;

my $filename = $ARGV[0];
my $filesize_after = -s "$filename";

die "Usage: $0 <filename>\n"                     unless $filename;
die "$0: $filename: No such file or directory\n" unless -e $filename;
die "$0: $filename: Permission denied\n"         unless -r $filename;

POE::Session->create
  ( inline_states =>
      { _start => sub { $_[HEAP]->{wheel} =
              POE::Wheel::FollowTail->new(
                Filename   => $_[ARG0],
                InputEvent => 'got_line',
                ErrorEvent => 'got_error',
                PollInterval => 1,
              );
            $_[HEAP]->{first} = 0;
        },
        got_line => sub { print "$_[ARG0]\n" if $_[HEAP]->{first}++ },
        got_error => \&handle_log_error,     
      },
    args => [$filename],
  );

# Handle log errors to shut down the service.
sub handle_log_error {
  my ($heap, $operation, $errno, $error_string, $wheel_id) =
    @_[HEAP, ARG0, ARG1, ARG2, ARG3];
  my $service = $heap->{services}->{$wheel_id};
  print "--- $service log $operation error $errno: $error_string\n";
  print "--- Shutting down $service log watcher.\n";
  delete $heap->{services}->{$wheel_id};
  delete $heap->{watchers}->{$wheel_id};
}

sub print_tail {
  my ($heap, $line) = @_[HEAP, ARG0];
  my $filesize = -s "$heap->{wheel}->[1]";
  
    if ( $filesize >= $filesize_after) {
        print "$line\n" if $_[HEAP]->{first}++;
    } else {
        handle_file_error(); }

    $filesize_after = -s "$heap->{wheel}->[1]";

}

$poe_kernel->run();