package Debug;
use strict;
use Filter::Util::Call ;
use constant TRUE  => 1 ;
use constant FALSE => 0 ;
sub import
{
my ($type) = @_ ;
my (%context) = (
Enabled      => defined $ENV{DEBUG},
InTraceBlock => FALSE,
Filename	  => (caller)[1],
LineNo	  => 0,
LastBegin	  => 0,
) ;
filter_add(bless \%context) ;
}
sub Die
{
my ($self) = shift ;
my ($message) = shift ;
my ($line_no) = shift || $self->{LastBegin} ;
die "$message at $self->{Filename} line $line_no.\n"
}
sub filter
{
my ($self) = @_ ;
my ($status) ;
$status = filter_read() ;
++ $self->{LineNo} ;
# deal with EOF/error first
if ($status <= 0) {
$self->Die("DEBUG_BEGIN has no DEBUG_END")
if $self->{InTraceBlock} ;
return $status ;
}
if ($self->{InTraceBlock}) {
if (/^\s*##\s*DEBUG_BEGIN/ ) {
$self->Die("Nested DEBUG_BEGIN", $self->{LineNo})
}
elsif (/^\s*##\s*DEBUG_END/) {
$self->{InTraceBlock} = FALSE
}
# comment out the debug lines when the filter is disabled
s/^/#/ if ! $self->{Enabled} ;
}
elsif ( /^\s*##\s*DEBUG_BEGIN/ ) {
$self->{InTraceBlock} = TRUE ;
$self->{LastBegin} = $self->{LineNo} ;
}
elsif ( /^\s*##\s*DEBUG_END/ ) {
$self->Die("DEBUG_END has no DEBUG_BEGIN", $self->{LineNo});
}
return $status ;
}
1 ;