#!/usr/bin/perl -w
# Using XML::LibXML::SAX
# author: Michel Rodriguez <mirod@xmltwig.com>
# with help from Aaron Straup Cope and Wolfgang Loch

use strict;

use XML::LibXML::SAX::Parser;
my $handler= my_handler->new();

my $parser = XML::LibXML::SAX::Parser->new( Handler => $handler);
$parser->parse_uri( 'REC-xml-19980210.xml');

package my_handler;

use base qw(XML::SAX::Base);

sub new { return bless {}; }

sub start_element {
	my ($h, $el) = @_;
	if ($el->{Name} eq 'rhs')     { $h->in_rhs = 1; } 
	elsif ($el->{Name} eq 'lhs')  { $h->in_lhs = 1; }
	elsif ($el->{Name} eq 'prod') { $h->rhs = ''; $h->lhs = ''; }
}

sub end_element {
	my ($h, $el) = @_;
	if ($el->{Name} eq 'rhs') {
		$h->in_rhs = undef;
	} 
	elsif ($el->{Name} eq 'lhs') {
		$h->in_lhs = undef;
	}
	elsif ($el->{Name} eq 'prod') {
		$h->counter++;
		my $prod = "[" . $h->counter. "] " . $h->lhs ." ::= " .$h->rhs ;
                $prod= clean( $prod);
	        print $prod . "\n";
	}
}

sub characters {
	my ($h, $characters) = @_;
	if ($h->in_lhs) {
		$h->lhs .= $characters->{Data};
	}
	elsif ($h->in_rhs) {
		$h->rhs .= $characters->{Data};
	}
}

# accessors, to be completely OO kosher
# works only for perl 5.6.0 and above
sub in_lhs  : lvalue { my $self= shift; $self->{in_lhs} ; }
sub lhs     : lvalue { my $self= shift; $self->{lhs}    ; }
sub in_rhs  : lvalue { my $self= shift; $self->{in_rhs} ; }
sub rhs     : lvalue { my $self= shift; $self->{rhs}    ; }
sub counter : lvalue { my $self= shift; $self->{counter}; }

sub clean { 
        my( $s)= @_;
        $s=~ s/\xc2\xa0/ /sg; 
	$s=~ s/\s+/ /g; $s=~ s{\s$}{};
        return $s;
}