XML::SemanticCompare - compare 2 XML trees semantically

	use XML::SemanticCompare;
	my $x = XML::SemanticCompare->new;

	# compare 2 different files
	my $isSame = $x->compare($control_xml, $test_xml);
	# are they the same
	print "XML matches!\n"
	  if $isSame;
	print "XML files are semantically different!\n"
	  unless $isSame;

	# get the diffs and print them out
    my $diffs_arrayref = $x->diff( $control_xml, $test_xml );
    print "Diff: $_\n" foreach (@$diffs_arrayref);

	# test xpath statement against XML
	my $success = $x->test_xpath($xpath, $test_xml);
	print "xpath success!\n" if $success;

#-----------------------------------------------------------------
# XML::SemanticCompare
# Author: Edward Kawas <edward.kawas+xml-semantic-compare@gmail.com>,
# For copyright and disclaimer see below.
#
# $Id: SemanticCompare.pm,v 1.1 2009-12-01 21:12:28 ubuntu Exp $
#-----------------------------------------------------------------
package XML::SemanticCompare;
use strict;
use Carp;
use vars qw /$VERSION/;
$VERSION = sprintf "%d.%02d", q$Revision: 1.1 $ =~ /: (\d+)\.(\d+)/;
use vars qw($AUTOLOAD);

#-----------------------------------------------------------------
# load all modules needed
#-----------------------------------------------------------------
use XML::Simple;
use XML::LibXML;
use XML::SemanticCompare::SAX;

use Data::Dumper;

#-----------------------------------------------------------------
# AUTOLOAD
#-----------------------------------------------------------------
sub AUTOLOAD {
	my $self = shift;
	my $type = ref($self)
	  or croak("$self is not an object");
	my $name = $AUTOLOAD;
	$name =~ s/.*://;    # strip fully-qualified portion
	unless ( exists $self->{_permitted}->{$name} ) {
		croak("Can't access '$name' field in class $type");
	}
	my $is_func = $self->{_permitted}->{$name}[1] =~ m/subroutine/i;
	unless ($is_func) {
		if (@_) {
			my $val = shift;
			$val = $val || "";
			return $self->{$name} = $val
			  if $self->{_permitted}->{$name}[1] =~ m/write/i;
			croak("Can't write to '$name' field in class $type");
		} else {
			return $self->{$name}
			  if $self->{_permitted}->{$name}[1] =~ m/read/i;
			croak("Can't read '$name' field in class $type");
		}
	}

	# call a function
	if ($is_func) {
		if (@_) {

			# parameterized call
			my $x = $self->{_permitted}->{$name}[0];
			return $self->$x(@_);
		} else {

			# un-parameterized call
			my $x = $self->{_permitted}->{$name}[0];
			return $self->$x();
		}
	}
}

#-----------------------------------------------------------------
# new
#-----------------------------------------------------------------
sub new {
	my ( $class, %options ) = @_;

	# permitted fields
	my %fields = (

		# attribute	        => [default, accessibility],
		trim       => [ 1,                       'read/write' ],
		use_attr   => [ 1,                       'read/write' ],
		compare    => [ "_test_xml",             'subroutine' ],
		diff       => [ "_get_xml_differences",  'subroutine' ],
		test_xpath => [ "_test_xpath_statement", 'subroutine' ],
	);

	# create an object
	my $self = { _permitted => \%fields };

	# set user values if they exist
	$self->{trim}     = $options{trim}     || '1';
	$self->{use_attr} = $options{use_attr} || '1';
	bless $self, $class;
	return $self;
}

#-----------------------------------------------------------------
# _test_xml: semantically compare $control_xml to $xml
#-----------------------------------------------------------------
sub _test_xml {
	my ( $self, $control_xml, $xml ) = @_;
	return undef unless $control_xml;
	return undef unless $xml;
	return undef if $control_xml =~ m//g;
	return undef if $xml         =~ m//g;

	# check the root element name first
	# this isnt very efficient, but until someone gives a better way ...
	my $parser   = XML::LibXML->new();
	my $cont_ele = undef;
	my $test_ele = undef;

	# try parsing a string or a file
	eval { $cont_ele = $parser->parse_string($control_xml); };
	eval { $cont_ele = $parser->parse_file($control_xml); } if $@;
	return undef if $@;
	eval { $test_ele = $parser->parse_string($xml); };
	eval { $test_ele = $parser->parse_file($xml); } if $@;
	return undef if $@;
	$cont_ele = $cont_ele->getDocumentElement;
	$test_ele = $test_ele->getDocumentElement;
	return undef
	  unless $cont_ele->localname eq $test_ele->localname
		  and $cont_ele->namespaceURI() eq $test_ele->namespaceURI();

	# free memory
	$parser   = undef;
	$cont_ele = undef;
	$test_ele = undef;

	# done checking the root element
	# create object with attributes
	my $xml_simple = new XML::Simple(
		ForceArray   => 1,
		ForceContent => 1,

		#		SuppressEmpty => 1,
		keyattr => [],
	) if $self->use_attr;

	# or create it without attributes
	$xml_simple = new XML::Simple(
		ForceArray   => 1,
		ForceContent => 1,

		#		SuppressEmpty => 1,
		NoAttr  => 1,
		keyattr => [],
	) unless $self->use_attr;

	# read both XML files into a HASH
	my $control = undef;
	my $test    = undef;

	# parse the control doc
	eval { $control = $xml_simple->XMLin($control_xml); };

	# check for invalid XML
	return undef if $@;

	# parse the test doc
	eval { $test = $xml_simple->XMLin($xml); };

	# check for invalid XML
	return undef if $@;
	return $self->_compare_current_level( $control, $test, (), () );
}

#-----------------------------------------------------------------
# _compare_current_level:
#    compares current level of data structures that represent XML
#      documents.
#    If the current level and all child levels match, a true value
#      is returned. Otherwise, undef is returned.
#-----------------------------------------------------------------
sub _compare_current_level {

	# $control is current level in hash
	# x_ns are the prefixes that we use
	my ( $self, $control, $test, $control_ns, $test_ns ) = @_;

	# if either hash is missing they arent equal
	return undef unless $control;
	return undef unless $test;

	# get the namespace prefix and uris at the  current level
	# for each doc and remove from current level of hash
	for my $key ( keys %$control ) {
		next unless $key =~ m/^xmlns[:]?/;

		#next unless $key =~ m|^{http://www\.w3\.org/2000/xmlns/}[\w]*$|;
		$control_ns->{''} = $control->{$key} if $key eq 'xmlns';
		$control_ns->{$1} = $control->{$key} if $key =~ m/xmlns\:(.*)$/g;
		delete $control->{$key} if ref( $control->{$key} ) ne 'ARRAY';
	}
	for my $key ( keys %$test ) {
		next unless $key =~ m/^xmlns[:]?/;

		#next unless $key =~ m|^{http://www\.w3\.org/2000/xmlns/}[\w]*$|;
		$test_ns->{''} = $test->{$key} if $key eq 'xmlns';
		$test_ns->{$1} = $test->{$key} if $key =~ m/xmlns\:(.*)$/g;
		delete $test->{$key} if ref( $test->{$key} ) ne 'ARRAY';
	}

	# compare current level number of keys
	return undef unless ( keys %$control ) == ( keys %$test );

	# number of keys are equal, so start comparing!
	my $matching_nodes = 0;
	for my $key ( keys %$control ) {
		my $success = 1;
		for my $test_key ( keys %$test ) {

		   # does the key exist?
		   # 'content' is a special case ... because its text content for a node
			if (
				 ( $key eq $test_key and $key eq 'content' )
				 or ( $self->_get_prefixed_key( $test_key, $test_ns ) eq
					      $self->_get_prefixed_key( $key, $control_ns )
					  and $self->_get_prefixed_key( $key, $control_ns ) )
			  )
			{

				# are we dealing with scalar values now or more nesting?
				if ( ref( $control->{$key} ) eq 'ARRAY' ) {

					# both items should be an array
					next unless ref( $test->{$test_key} ) eq 'ARRAY';

					# array sizes should match here ...
					next
					  unless @{ $control->{$key} } == @{ $test->{$test_key} };

					# more nesting try matching child nodes
					my $child_matches = 0;
					foreach my $child ( @{ $control->{$key} } ) {
						my $matched = undef;
						foreach my $test_child ( @{ $test->{$test_key} } ) {
							$matched =
							  $self->_compare_current_level( $child,
										   $test_child, $control_ns, $test_ns );
							$child_matches++ if $matched;
							last if $matched;
						}    # end inner foreach
						$matching_nodes++
						  if @{ $control->{$key} } == $child_matches;
					}
				} else {

					# compare scalar values now
					# we dont care about whitespace, so we need to trim the text
					my $c_text = $self->_clear_whitespace( $control->{$key} );
					my $t_text = $self->_clear_whitespace( $test->{$test_key} );
					$matching_nodes++ if $c_text eq $t_text;
					last if $c_text eq $t_text;
				}
			}
		}    #end inner for
	}

	# no differences found!
	return undef unless $matching_nodes == ( keys %$control );
	return 1;
}

#-----------------------------------------------------------------
# _clear_whitespace: a whitespace trim function
#-----------------------------------------------------------------
sub _clear_whitespace {
	my ( $self, $text ) = @_;
	return $text unless $self->trim;
	$text =~ s/^\s+//;
	$text =~ s/\s+$//;
	return $text;
}

#-----------------------------------------------------------------
# _get_prefixed_key:
#    goes through and tries to determine what the namespace URI
#     is for a prefix.
#    Once a URI is found, the prefix is swapped with URI and
#     returned.
#-----------------------------------------------------------------
sub _get_prefixed_key {
	my ( $self, $key, $ns_hash ) = @_;
	my $prefixed_key = $key;
	my $prefix = $1 if $key =~ m/^([\w]+)\:.*/;
	$prefixed_key =~ s/$prefix/$ns_hash->{$prefix}/
	  if $prefix and $ns_hash->{$prefix};

	# check for default xmlns
	$prefix = $prefix || '';
	$prefixed_key = $ns_hash->{$prefix} . ":" . $key
	  if not $prefix and defined $ns_hash->{$prefix};
	return $prefixed_key;
}

#-----------------------------------------------------------------
# _test_xpath_statement: apply $xpath to $xml
#-----------------------------------------------------------------
sub _test_xpath_statement {
	my ( $self, $xpath, $xml ) = @_;

	# no xpath expression, nothing to test
	return undef if $xpath =~ m//g;

	# empty xml, nothing to test
	return undef if $xml =~ m//g;

	#instantiate a parser
	my $parser = XML::LibXML->new();
	my $tree   = undef;

	# try parsing a string or a file
	eval { $tree = $parser->parse_string($xml); };
	eval { $tree = $parser->parse_file($xml); } if $@;
	return undef if $@;
	my $root = $tree->getDocumentElement;

	# evaluate the xpath statement
	my $results = undef;
	eval { $results = $root->find($xpath); };
	return undef if $@;

	# no results?
	return undef unless $results;

	# got some hits!
	return 1;
}

#-----------------------------------------------------------------
# _get_xml_differences:
#    get the differences between $xml and expected xml
#      and return them
#-----------------------------------------------------------------
sub _get_xml_differences {
	my ( $self, $control_xml, $test_xml ) = @_;
	my @diffs;

	# create a parser
    my $parser = new XML::SemanticCompare::SAX();
    
    # parse a file $xml is an array of strings representing the XML tree
    my $xml = undef;
    eval {$xml = $parser->parse ( method => 'string', data => $control_xml );};
    eval {$xml = $parser->parse ( method => 'file', data => $control_xml );} unless $xml;
	#my %control = map {($_, 1)} @$xml;
	my $xml2 = undef;
    eval {$xml2 = $parser->parse ( method => 'string', data => $test_xml );};
    eval {$xml2 = $parser->parse ( method => 'file', data => $test_xml );} unless $xml2;
	
	foreach my $i ( 0 .. scalar(@$xml)-1) {
		next unless $xml->[$i];
		foreach my $j (0 .. scalar(@$xml2)-1) {
			next unless $xml2->[$i];
	        if ($xml->[$i] eq $xml2->[$j]) {
	        	delete $xml->[$i];
	        	delete $xml2->[$j];
	        	last;
	        }
		}
	}
	push @diffs, grep {defined $_} (@$xml, @$xml2);
	# items left over ...
	# grep {$control{$_} > 0} keys %control;
	return \@diffs;
}

sub DESTROY { }
1;
__END__

=cut