#!/usr/bin/perl

use strict;
use warnings;

my $head = {data => 0, prev => undef, next => undef};
my $previous = $head;

open FILE, "<datastored.txt" or die $!;

while (<FILE>){
    chomp;
    $previous->{next} = {
                "data" => $_ , 
                "next" => undef,
                "prev" => $previous,
            };
    $previous = $previous->{next};
    
}

### Inserting element at the beginning of the list after the head node
my $curr = $head;
$curr->{next}= {
                 "data" => 30, 
                "next" => $curr->{next},
                "prev" => $curr,    
};


### Inserting element at the end of the list before the tail node
$curr = $previous;
$curr->{prev}= {
                 "data" => 40, 
                "next" => $curr,
                "prev" => $curr->{prev},    
};


## Printing from head
print "printing from head \n";

 $curr = $head;
while (1) {
    last unless defined $curr->{next};
    print "Current: ", $curr->{data}, 
          "\tPrevious: ", $curr->{prev}{data} // "", 
          "\tNext: ", $curr->{next}{data} // "", "\n";
    $curr = $curr->{next};
}


## printing from tail


print "Printing From tail \n";

while (1) {
    last unless defined $curr->{prev};
    print "Current: ", $curr->{data}, 
          "\tPrevious: ", $curr->{prev}{data} // "", 
          "\tNext: ", $curr->{next}{data} // "", "\n";
    $curr = $curr->{prev};
}