package Error;

use HTML::Template;
use strict;

sub new {
	my ($class,$file) = @_;
	my $self  = {
		ERRORS => undef,   # this key is a list of hashes
		file   => $file,
	};
	bless $self, $class;
	return $self;
}

sub add_error {

	my ($self,$field,$reason) = @_;
	push @{$self->{ERRORS}}, { 
		FIELD  => $field,
		REASON => $reason,
	};
}

sub generate_errors {
	
	my ($self,$file) = @_;
	return unless &not_empty;
	
	my $template = HTML::Template->new(filename => $self->{file});
	$template->param(
		IS_SINGULAR => (scalar @{$self->{ERRORS}} == 1),
		ERRORS      => $self->{ERRORS},
	);

	@{$self->{ERRORS}} = ();
	return $template->output;
}

sub not_empty {
	my $self = shift;
	return ($self->{ERRORS}) ? (scalar @{$self->{ERRORS}} > 0) : 0;
}

1;

##</code><code>##

use Errors;
my $ERROR = Error->new('error.tmpl');

# etc. . . .
 
sub validate_offer_name {

	my $offer_name = strip_spaces($CGI->param('offer_name'));

	unless ($offer_name =~ m/^[A-Za-z]\w*$/) {
		# ERROR - user entered invalid offer name
		$ERROR->add_error('Create New Offer', 'Invalid characters were found');
		go_home();
		return;
	}

	if (&check_existing($DBH,$offer_name)) {
		# ERROR - name already exists
		$ERROR->add_error('Create New Offer', 'That name exists, try again');
		go_home();
		return;
	}

	# success - valid name that does not exist
	print_create_offer_form($offer_name);
}

sub go_home {

	# if there are no errors, $errors will be undefined
	my $errors = $ERROR->generate_errors;

	my $template = HTML::Template->new(filename => 'home.tmpl');
	$template->param(
		EXISTING_OFFERS     => fetch_all_offers($DBH),
		EXISTING_TRANSPORTS => fetch_all_transports($DBH),
		ERRORS              => $errors,
	);

	print $CGI->header;
	print $template->output;
}

##</code><code>##

The following
<TMPL_IF NAME="IS_SINGULAR">
	error was
<TMPL_ELSE>
	errors were
<TMPL_IF>
found:
<TABLE WIDTH="95%">
<TMPL_LOOP NAME=ERRORS>
<TR>
  <TD CLASS=body WIDTH="20%" ALIGN=right>
    <FONT COLOR=red><TMPL_VAR NAME=FIELD></FONT>:
</TD>
  <TD CLASS=body ALIGN=left>
    <TMPL_VAR NAME=REASON>
  </TD>
</TR>
</TMPL_LOOP>
</TABLE>
Please try again