#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper qw(Dumper);
use constant ARGUMENTS => scalar 2;

$| = 1;

my @timestamp_first;
my @timestamp_second;
my $write = 'output.txt';

sub first {
    
    open (FIRST, "<" , $ARGV[0])
	or die ("Could not open: ".$ARGV[0]." - $!\n");

    while ( my @first_read = <FIRST> ) {

	chomp @first_read;	

	foreach $_ (@first_read) {
	    my @result_first = split (':', $_);

	    if (/^\s*$/) { # /^\s*$/ check for "blank" lines may contain spaces or tabs
		next;
	    }

	    push (@timestamp_first, $result_first[3]);

	}
    }

    close (FIRST)
	or die ("Could not close: ".$ARGV[0]." - $!\n");
    
    return @timestamp_first;
}

sub second {
    
    open (SECOND, "<" , $ARGV[1])
	or die ("Could not open: ".$ARGV[1]." - $!\n");

    while ( my @second_read = <SECOND> ) {

	chomp @second_read;

	foreach $_ (@second_read) {
	    my @result_second = split (':', $_);

	    if (/^\s*$/) { # /^\s*$/ check for "blank" lines may contain spaces or tabs
		next;
	    }

	    push (@timestamp_second, $result_second[3]);

	}
    }

    close (SECOND)
	or die ("Could not close: ".$ARGV[1]." - $!\n");
    
    return @timestamp_second;
}

sub write {

    open (WRITE , ">>" , $write )
	or die ("Could not open: ".$write." - $!\n");
    
    foreach $_ (@_) {
	print WRITE $_ . "\n";
    }

    close (WRITE)
	or die ("Could not close: ".$write." - $!\n");

    my $text = "Successfully writen on ".$write.".\n";
    
    return ($text);
}

sub check {
    
    if (@ARGV < ARGUMENTS || @ARGV > ARGUMENTS) {
	die "Please enter ".ARGUMENTS." files to read!\n";
    }

}

&check(@ARGV);
my @first_values = &first($ARGV[0]);
my @second_values = &second($ARGV[1]);

my @final;
my $num = @first_values;

for($_ = 0; $_ < $num; $_++) {
    push (@final , $first_values[$_] . ' ' . $second_values[$_]);
}

print Dumper (\@final);

my $date = time();

my $output = &write(@final);

print "\nResult: ".$output."";