#!/usr/bin/perl
use strict;
use warnings;
use Tk;
use Tk::ROText;

# set to `0' if you do not want the actual MACs of detected NICs to be used
# if set to `1', will gracefully/silently be ignored if no NICs are detected
my $use_real_macs = 1;

# get NICs available to system
opendir(DIR,'/sys/class/net') or die "can't opendir '/sys/class/net': $!\n";
my @nics = sort grep{!/lo/ && !/^\.\.?$/} readdir(DIR);
closedir(DIR);

# define some NICs (for display purposes) if none are found
unless($#nics>=0){
  @nics = ('eth0','eth1');
  $use_real_macs = 0;
}

my $mw = MainWindow->new(-title => 'MAC Address Tool');

$mw->fontCreate('sans_8',
  -family => 'sans',
  -weight => 'normal',
  -size   => 8,
);

$mw->fontCreate('mono',
  -family => 'mono',
  -weight => 'bold',
  -size   => 12,
);

my $fr1 = $mw->Frame()->pack(-expand => 1, -fill => 'both');
my $lb1 = $fr1->Label(-text => 'Select NIC')->pack(-side=>'left');

# hash to store MAC addresses saved, per NIC
my %macs = ();

# default val of the text variable that represents the currently selected NIC
my $nic = $nics[0];

# NIC drop-down menu
my $nicWidget = $fr1->Optionmenu(
  -font             => '{verdana} 10 {normal}',
  -bg               => 'white',
  -foreground       => 'Gray50',
  -activebackground => 'white',
  -options          => [@nics],
  -anchor           => 'w',
  -relief           => 'sunken',
  -bd               => 2,
  -padx             => 1,
  -takefocus        => 1,
  -textvariable     => \$nic,
)->pack(-side=>'left');

my $fr = $mw->Frame()->pack(-expand => 1, -fill => 'both');
my $lb = $fr->Label(-text => 'Enter MAC Address')->grid(-row=>0,-column=>0);

my $okBtn = $fr->Button(
  -text      => 'Save',
  -font      => 'sans_8',
  -state     => 'disabled',
  -bd        => 1,
  -takefocus => 0,
  -pady      => 5,
);

my %rot;
my $row = 3;
for(@nics){

  $fr->Label(-text=>$_.' MAC Address:')->grid(-row=>$row,-column=>0);
  $row++;

  $rot{$_} = $fr->ROText(
    -relief             => 'solid',
    -height             => 1,
    -width              => 18,
    -bg                 => 'white',
    -font               => 'mono',
    -foreground         => 'black',
    -bd                 => 1,
    -takefocus          => 0,
    -highlightthickness => 0,
    -state              => 'disabled',
  );

}

# widget used to display Entry field errors
my $errW = $fr->Label(-foreground=>'red');

# exit button
my $exitBtn = $fr->Button(
  -text      => 'Exit',
  -command   => sub {exit(0);},
  -font      => 'sans_8',
  -state     => 'normal',
  -bd        => 1,
  -takefocus => 0,
  -pady      => 5,
);

# hash to hold Entry widgets
my %entries;

# loop thru the number of Entry widgets desired
for(1..6){

  # create the Entry widget
  $entries{$_}{'entry'} = $fr->Entry(
    -font         => '{verdana} 12 {normal}',
    -textvariable => \$entries{$_}{'addy'},
    -width        => 3,
    -bg           => 'white',
  );

  # validate using bind
  $entries{$_}{'entry'}->bind('<KeyRelease>',[\&validation,$_,\%entries]);

  # save default widget background
  $entries{$_}{'bg'} = $entries{$_}{'entry'}->cget('-bg');

  # what type of validation will be done in this value
  $entries{$_}{'type'} = 'mac';

  # pack/display the widget
  $entries{$_}{'entry'}->grid(-row=>0,-column=>$_);

}

# see if we should use the actual MAC addresses
if($use_real_macs){

  # look up real MAC addresses
  for(@nics){
    my $file = '/sys/class/net/'.$_.'/address';
    open(FH,'<',$file) or die "can't open '$file': $!\n";
    my $address = readline(*FH);
    close(FH);
    die "Failed to get MAC for $_\n" unless($address);
    chomp($address);
    print "Real MAC address for $_: $address\n";
    my @address = split(/:/,$address);
    for(my $i=0;$i<=$#address;$i++){
      my $oct = $address[$i];
      $macs{$_}{$i+1} = $oct;
    }
  }

}else{

  # create some bogus MAC values (make values invalid to test validation)
  for(sort keys %entries){
    $macs{$nic}{$_} = ($_>1) ? $_.$_ : '';
    $macs{$nic}{$_} .= 'z' if($_ == 3 or $_ == 4);
  }
}
# update MAC input fields at application start-up
&update_mac_fields;

# update MAC input fields whenever a new NIC is selected
$nicWidget->configure(-command => [\&update_mac_fields]);

# the Save button will validate *all* Entries
$okBtn->configure(-command => [ \&validate_all,\%entries ]);

# pack widgets based upon number of Entries
$errW->grid(-row=>1,-column=>1,-columnspan=>scalar keys %entries);
$okBtn->grid(-row=>2,-column=>(scalar keys %entries)-1,-columnspan=>2,-pady=>5);
$row = 3;
for(@nics){
  $rot{$_}->grid(-row=>$row,-column=>1,-columnspan=>scalar keys %entries);
  $row++;
}
$exitBtn->grid(-row=>$row,-column=>(scalar keys %entries)-1,-columnspan=>2,-pady=>5);

# auto-tab thru all Entry widgets to perform validation on pre-populated values
for(1..(scalar keys %entries) + 1){
  $mw->eventGenerate('<Tab>');
  $mw->eventGenerate('<KeyRelease>');
#  $mw->idletasks;
  $mw->after(100);
  $mw->update;
}

MainLoop();

sub update_mac_fields {
  for(sort keys %entries){
    $entries{$_}{'addy'} = $macs{$nic}{$_} ? $macs{$nic}{$_} : '';
    $entries{$_}{'entry'}->configure(-state=>'normal');
    $entries{$_}{'entry'}->configure(-bg=>$entries{$_}{'bg'});
  }
  $errW->configure(-text=>'');
  $okBtn->configure(-state=>'normal');
  $nicWidget->focus();
}

sub validate_all {
  my($ref) = @_;
  my $failed;
  my $empty;
  my $newmac;
  print "\nValidating all entries: \n";
  for(sort keys %$ref){

    # make sure field validates
    unless(&validation(undef,$_,$ref)){
      $failed = 1;
      last;
    }

    # make sure validated field is not empty
    my $octet = $ref->{$_}{'entry'}->get;
    unless($octet){
      $failed = 1;
      $empty = $_;
      last;
    }

    # concatenate the new MAC address
    $newmac .= ($newmac) ? ':'.$octet : $octet;

    # save to hash
    $macs{$nic}{$_} = $octet;
  }

  if($failed){
    if(defined($empty)){
      &validation_failed($empty,$ref,"Field \`$empty' cannot be empty");
    }
  }else{
    $failed = 0;
    $rot{$nic}->configure(-state=>'normal');
    $rot{$nic}->delete('1.0','end');
    $rot{$nic}->insert('end',$newmac);
    $rot{$nic}->configure(-state=>'disabled');
  }
  return $failed;
}

# returns `1' if valid, and `0' if invalid
sub validation {
  my($self,$id,$ref) = @_;
  my $widget = defined($self) ? $self : $ref->{$id}{'entry'};
  my $value = $ref->{$id}{'addy'};
  my $type = $ref->{$id}{'type'};

  # boolean, 1 if validation is successful, 0 if fails
  my $valid;

  # see if any value was entered in the Entry widget field
  if($value){

    # get the index number of the last character in the value
    my $index = -1;
    if($self){$index++ while $value =~ /./g}

    print "Field $id ($type) index $index, val is \`",$value,"', validating...";

    # MAC address octet validation
    if($type eq 'mac'){
      if($index == 0){
        if($value =~ /^[0-9a-f]$/i){
          $valid = 1;
        }else{
          $valid = 0;
        }
      }elsif(($index == 1)||($index == -1)){
        if($value =~ /^[0-9a-f]{2}$/i){
          $valid = 1;
        }else{
          $valid = 0;
        }
      }else{
        $valid = 0;
      }

    # place-holder for other validation data types that are not defined yet
    }else{
      $valid = 1;
    }
    printf("%s\n",($valid) ? "ok" : "FAILED");

  # field must have been cleared or is empty (this is valid), clear out errors
  }else{
    print "Field $id ($type) has no value, resetting field...\n";
    $valid = 1;
  }

  if($valid){

    $widget->configure(-bg=>'white');

    # clear error widget
    &clear_err($id,$ref);

    # re-enable all other widgets
    for(sort keys %$ref){
      next if(/^$id$/);
      $ref->{$_}{'entry'}->configure(-state=>'normal');
    }

    # allow focus to NIC widget
    $nicWidget->configure(-takefocus=>1);

    # enable the Save button
# uncomment commented lines to implement a check for non-empty fields first
#    my $empty;
#    for(sort keys %$ref){
#      unless($ref->{$_}{'entry'}->get){
#        $empty = 1;
#        last;
#      }
#    }
#    unless($empty){
      $okBtn->configure(-state=>'normal');
      $okBtn->configure(-takefocus=>1);
#    }

  }else{
    &validation_failed($id,$ref);
  }
  return $valid;
}

sub validation_failed {
  my($id,$ref,$errmsg) = @_;
  my $widget = $ref->{$id}{'entry'};
  my $value = $ref->{$id}{'addy'};

  $errmsg = "Field $id value \`$value' is invalid" unless($errmsg);

  # turn the background of the problem field to red
  $widget->configure(-bg=>'red');
  $widget->update();

  # update the error widget with text indicating a problem with the value
  $errW->configure(-text=>$errmsg);

  # temporarily disable focus on all other widgets
  for(sort keys %$ref){
    next if(/^$id$/);
    $ref->{$_}{'entry'}->configure(-state=>'disabled');
  }

  # disable the Save button
  $okBtn->configure(-state=>'disabled');
  $okBtn->configure(-takefocus=>0);

  # unfocus the Select NIC widget
  $nicWidget->configure(-takefocus=>0);

  $widget->focus();
}

sub clear_err {
  my($id,$ref) = @_;
  $errW->configure(-text=>'');
  $ref->{$id}{'entry'}->configure(-bg=>$ref->{$id}{'bg'});
}