#!/usr/bin/perl

use strict;
use XML::Filter::Hekeln;
use XML::Handler::YAWriter;
use XML::Parser::PerlSAX;
use IO::File;

my $script_file = new IO::File( $ARGV[0] );
    die 'usage: hekeln script <xmlinfile >xmloutfile' unless $script_file;
my $irs = $/;
    undef $/;
my $script = <$script_file>;
    close $script_file;
   $/ = $irs;

my $xml_file = new IO::File( '>-' );
my $in_file = new IO::File( '<-' );

my $handler = new XML::Handler::YAWriter(
	'Output' => $xml_file,
	'Pretty' => {
		'CatchEmptyElement' => 1,
		'AddHiddenAttrTab' => 1,
		'AddHiddenNewLine' => 1,
		'NoProlog' => 1,
		'NoDTD' => 1
		}
	);

my $hekeln = new XML::Filter::Hekeln(
#	'Debug'  => 1,
	'Handler' => $handler,
	'Script' => $script
	);

my $parser = new XML::Parser::PerlSAX( 'Handler' => $hekeln );
   $parser->parse( 'Source' => { 'ByteStream' => $in_file } );

   $in_file->close();
   $xml_file->close();

0;
__END__

=head1 NAME

hekeln - command line interface to the Hekeln SAX stream editor

=head1 SYNOPSIS

  hekeln scriptfile < some.xml > some_processed.xml

=head1 DESCRIPTION

Hekeln is a PerlSAX stream editor. The hekeln script provides
a shell interface for this tool, that could be used for testing
hekeln scripts or to embed them into other languages.

=head1 OPTIONS

  Currently no options ;-( 

I think that the set of options used in YAWriter are a good start,
lets look what we additonal need for processing batches.

=head1 ABUSE

Its possible to "chmod u+x" a Hekeln script, but syntax is a bit
nasty! Lets look at a template :

	#!/usr/bin/perl /usr/bin/hekeln
	#	this comment is IMPORTANT
  <blank-line>
  	start_element:topmost_element
	!       $self->handle('start_document',{});
	<	top_tag	>
  <blank-line>
  	start_element:second_element
	<	second_tag	>
	++	process_it
  <blank-line>
  	start_element:second_element
	--	process_it
	</	second_tag	>
  <blank-line>
  	start_element:topmost_element
	</	top_tag	>
	!       $self->handle('end_document',{});
  <blank-line>
  	character:process_it
		~Data~

This script would search through an xml for the occurance of the
'topmost_element' to open a new xml output document. Any character
data in a 'second_element' will be dumped.

How blank lines and tabs are aranged is for importance! In a Hekeln
script any paragraph that starts with a '#' is ignored, so we need the
blank line, and therefore at least one comment in any script!

Also paragraphs that do not match the '^[^:]+:[^:]+$' template for the
first line and any line in an interpreted paragraph that does have a
valid indicator are silently ignored. Perhaps future version will raise
warnings and errors.

=head1 AUTHOR

  Michael Koehne, Kraehe@Copyleft.De
  (c) 2000 GNU General Public License

=head1 SEE ALSO

L<XML::Parser::PerlSAX> and L<XML::Filter::Hekeln>

=cut