#
# (c) Jan Gehring <jan.gehring@gmail.com>
# 
# vim: set ts=3 sw=3 tw=0:
# vim: set expandtab:

=head1 NAME

Rex::Commands::Tail - Tail a file

=head1 DESCRIPTION

With this module you can tail a file

=head1 SYNOPSIS

 tail "/var/log/syslog";


=head1 EXPORTED FUNCTIONS

=over 4

=cut


package Rex::Commands::Tail;

use strict;
use warnings;

require Rex::Exporter;
use Data::Dumper;
use Rex::Commands::Fs;
use Rex::Commands::File;

use vars qw(@EXPORT);
use base qw(Rex::Exporter);

@EXPORT = qw(tail);

=item tail($file)

This function will tail the given file.

 task "syslog", "server01", sub {
    tail "/var/log/syslog";
 };

Or, if you want to format the output by yourself, you can define a callback function.

 task "syslog", "server01", sub {
    tail "/var/log/syslog", sub {
      my ($data) = @_;
      
      my $server = Rex->get_current_connection()->{'server'};
      
      print "$server>> $data\n";
    };
 };



=cut

sub tail {
   my $file = shift;
   my $callback = shift;

   if(Rex::is_sudo()) {
      die("Can't use tail within sudo environment.");
   }

   Rex::Logger::debug("Tailing: $file");

   if(my $ssh = Rex::is_ssh()) {
      my %stat = stat $file;
      my $orig_size = $stat{'size'};
      my $new_pos = $stat{'size'} - 1024;
      if($new_pos < 0) { $new_pos = 0; }

      my %new_stat;
      my $old_pos;
      while(1) {
         if(!%new_stat || $new_stat{'size'} > $stat{'size'}) {
            my $fh = file_read $file;
            unless($fh) {
               die("Error opening $file for reading");
            }
            my $data;

            if(!%new_stat) {
               $fh->seek($stat{'size'} - 1024);
               $data = $fh->read(1024);
            }
            else {
               $fh->seek($old_pos);
               $data = $fh->read($new_stat{'size'} - $old_pos);
            }
            

            my @lines = split(/\n/, $data);
            shift @lines unless $old_pos;

            if($callback) {
               for my $line (@lines) {
                  &$callback($line);
               }
            }
            else {
               print join("\n", @lines) . "\n";
            }

            $fh->close;
            $old_pos = $new_stat{'size'};
         }

         select undef, undef, undef, 0.3;
         %stat = %new_stat if %new_stat;
         %new_stat = stat $file;
      }

   } else {
      system("tail -f $file");
   }

}

=back

=cut

1;