package Embed::Persistent;

use strict;
use vars '%Cache';

#use Devel::Symdump ();

sub valid_package_name {
    my($string) = @_;
    $string =~ s/([^A-Za-z0-9\/])/sprintf("_%2x",unpack("C",$1))/eg;
    # second pass only for words starting with a digit
    $string =~ s|/(\d)|sprintf("/_%2x",unpack("C",$1))|eg;

    # Dress it up as a real package name
    $string =~ s|/|::|g;
    return "Embed" . $string;
}

#borrowed from Safe.pm
sub delete_package {
    my $pkg = shift;
    my ($stem, $leaf);

    no strict 'refs';
    $pkg = "main::$pkg\::";	# expand to full symbol table name
    ($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;

    my $stem_symtab = *{$stem}{HASH};

    delete $stem_symtab->{$leaf};
}

sub eval_file {
    my($filename, $delete) = @_;
    my $package = valid_package_name($filename);
    my $mtime = -M $filename;
    if(defined $Cache{$package}{mtime}
       &&
       $Cache{$package}{mtime} <= $mtime) 
    {
	# we have compiled this subroutine already, 
	# it has not been updated on disk, nothing left to do
  	print STDERR "already compiled $package->handler\n";
    }
    else {
	local *FH;
	open FH, $filename or die "open '$filename' $!";
	local($/) = undef;
	my $sub = <FH>;
	close FH;

	#wrap the code into a subroutine inside our unique package
	my $eval = qq{package $package; sub handler { $sub; }};
	{
	    # hide our variables within this block
	    my($filename,$mtime,$package,$sub);
	    eval $eval;
	}
	die $@ if $@;

	#cache it unless we're cleaning out each time
	$Cache{$package}{mtime} = $mtime unless $delete;
    }

    eval {$package->handler;};
    die $@ if $@;

    delete_package($package) if $delete;

    #take a look if you want
    #print Devel::Symdump->rnew($package)->as_string, $/;
}

1;

__END__