#! /usr/bin/perl

# this program merges an old and a new MRTG log into a single log 

use strict;

my @HELP = qq(
mergeolddata: invalid option -- @ARGV
usage: mergeolddata [current log file] [old log file]
);
die "@HELP" unless ($ARGV[0]);

my $current_file = $ARGV[0];
my $old_file = $ARGV[1];

# read in log files
open(CURRENTFILE,"$current_file");
my @current = <CURRENTFILE>;
close(CURRENTFILE);
open(OLDFILE,"$old_file");
my @old = <OLDFILE>;
close(OLDFILE);

# make backup 
my $epoch = time();
system("cp $current_file $current_file.backup_$epoch");

my %current_array;
my %old_array;

# make a hash of the old log data
for my $line (@old)
{
        my ($timestamp, $data1, $data2, $data3, $data4) = split (/\s+/, $line);
        $old_array{$timestamp} = ("$data1 $data2 $data3 $data4");
}

# make a hash of the current log data
my @OUTDATA;
for my $line (@current)
{
        my ($timestamp, $data1, $data2, $data3, $data4) = split (/\s+/, $line);
        $current_array{$timestamp} = ("$data1 $data2 $data3 $data4");

        if ($data1 eq "0" && $old_array{$timestamp})
        {
                push (@OUTDATA, "$timestamp $old_array{$timestamp}\n");
        }
        elsif ($data1 eq "0" && ! $old_array{$timestamp})
        {
                push (@OUTDATA, "$timestamp $current_array{$timestamp}\n");
        }
        elsif ($data1 gt "0")
        {
                push (@OUTDATA, "$timestamp $current_array{$timestamp}\n");
        }
}

# write out the new log
open(NEWFILE,">$current_file");
print NEWFILE @OUTDATA;
close(NEWFILE);