=pod

=encoding utf8

=head1 NAME

XML::Loy - Extensible XML Reader and Writer


=head1 SYNOPSIS

  use XML::Loy;

  # Create new document with root node
  my $xml = XML::Loy->new('env');

  # Add elements to the document
  my $header = $xml->add('header');

  # Nest elements
  $header->add('greetings')->add(title => 'Hello!');

  # Append elements with attributes and textual data
  $xml->add(body => { date => 'today' })->add(p => "That's all!");

  # Use CSS3 selectors for element traversal
  $xml->at('title')->attr(style => 'color: red');

  # Attach comments
  $xml->at('greetings')->comment('My Greeting');

  # Print with pretty indentation
  print $xml->to_pretty_xml;

  # <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  # <env>
  #   <header>
  #
  #       <!-- My Greeting -->
  #       <greetings>
  #         <title style="color: red">Hello!</title>
  #       </greetings>
  #     </header>
  #     <body date="today">
  #       <p>That&#39;s all!</p>
  #     </body>
  #   </env>


=head1 DESCRIPTION

L<XML::Loy> allows for the simple creation
of small serialized XML documents with
various namespaces.
It focuses on simplicity and extensibility,
while giving you the full power of L<Mojo::DOM>.


=head1 METHODS

L<XML::Loy> inherits all explicit methods from
L<Mojo::DOM> and implements the following new ones.


=head2 new

  my $xml = XML::Loy->new(<<'EOF');
  <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  <entry>
    <fun>Yeah!</fun>
  <entry>
  EOF

  $xml = XML::Loy->new('Document');
  $xml = XML::Loy->new(Document => { foo => 'bar' });
  my $xml_new = $xml->new(Document => {id => 'new'} => 'My Content');

Constructs a new L<XML::Loy> document.
Accepts either all parameters supported by L<Mojo::DOM> or
all parameters supported by L<add|/add>.


=head2 add

  my $xml = XML::Loy->new('Document');

  # Add an empty element
  $xml->add('Element');

  # Add elements with attributes
  my $elem = $xml->add(Element => { type => 'text/plain' });

  # Add nested elements with textual content
  $elem->add(Child => "I'm a child element");

  # Add elements with attributes, textual content, and a comment
  $xml->add(p => { id => 'id_4' }, 'Hello!', 'My Comment!');

  # Add elements with rules for pretty printing
  $xml->add(Data => { -type => 'armour' }, 'PdGzjvj..');

  # Add XML::Loy objects
  $elem = $xml->new(Element => 'Hello World!');
  $xml->add($elem);

Adds a new element to a L<XML::Loy> document, either
as another L<XML::Loy> object or newly defined.
Returns the root node of the added L<XML::Loy>
document.

Parameters to define elements are a tag name,
followed by an optional hash reference
including all attributes of the XML element,
an optional textual content,
and an optional comment on the element
(if the comment should be introduced to an empty element,
text content has to be C<undef>).

For giving directives for rendering element content
with L<pretty printing|/to_pretty_xml>,
a special C<-type> attribute can be defined:

=over 2

=item

C<escape>

XML escape the content of the node.

  my $xml = XML::Loy->new('feed');
  my $html = $xml->add(html => { -type => 'escape' });
  $html->add(h1 => { style => 'color: red' } => 'I start blogging!');
  $html->add(p => 'What a great idea!')->comment('First post');

  print $xml->to_pretty_xml;

  # <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  # <feed>
  #   <html>
  #     &lt;h1 style=&quot;color: red&quot;&gt;I start blogging!&lt;/h1&gt;
  #
  #     &lt;!-- First post --&gt;
  #     &lt;p&gt;What a great idea!&lt;/p&gt;
  #   </html>
  # </feed>

=item

C<raw>

Treat children as raw data (no pretty printing).

  my $plain = XML::Loy->new(<<'PLAIN');
  <entry>There is <b>no</b> pretty printing</entry>
  PLAIN

  my $xml = XML::Loy->new('entry');
  my $text = $xml->add(text => { -type => 'raw' });
  $text->add($plain);

  print $xml->to_pretty_xml;

  # <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  # <entry>
  #   <text><entry>There is <b>no</b> pretty printing</entry>
  # </text>
  # </entry>


=item

C<armour:n>

Indent the content and automatically
introduce linebreaks after every
C<n>th character.
Intended for base64 encoded data.
Defaults to 60 characters line-width after indentation.

  my $xml = XML::Loy->new('entry');

  my $b64_data = <<'B64';
    VGhpcyBpcyBqdXN0IGEgdGVzdCBzdHJpbmcgZm
    9yIHRoZSBhcm1vdXIgdHlwZS4gSXQncyBwcmV0
    dHkgbG9uZyBmb3IgZXhhbXBsZSBpc3N1ZXMu
  B64

  my $data = $xml->add(
    data => { -type => 'armour:30' } => $b64_data
  );

  $data->comment('This is base64 data!');

  print $xml->to_pretty_xml;

  # <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  # <entry>
  #
  #   <!-- This is base64 data! -->
  #   <data>
  #     VGhpcyBpcyBqdXN0IGEgdGVzdCBzdH
  #     JpbmcgZm9yIHRoZSBhcm1vdXIgdHlw
  #     ZS4gSXQncyBwcmV0dHkgbG9uZyBmb3
  #     IgZXhhbXBsZSBpc3N1ZXMu
  #   </data>
  # </entry>

=back


=head2 set

  my $xml = XML::Loy->new('Document');
  $xml->set(Element => { id => 5 });

  # Overwrite
  $xml->set(Element => { id => 6 });

Adds a new element as a child to the node only once.
Accepts all parameters as defined in L<add|/add>.

If one or more elements with the same tag name are
already children of the requesting node,
the old elements will be deleted and
comments will be merged if possible.


=head2 comment

  $node = $node->comment('Resource Descriptor');

Prepends a comment to the current node.
If a node already has a comment, comments will be merged.


=head2 extension

  # Add extensions
  my $xml = $xml->extension('Fun', 'XML::Loy::Atom', -HostMeta);

  # Further additions
  $xml->extension(-Atom::Threading);

  my @extensions = $xml->extension;

Adds or returns an array of extensions.
When adding, returns the document.
When getting, returns the array of associated extensions.

The extensions are associated to the document, they are not associated
to the object. That means, you can't add extensions to documents
without a root node.

With this package the following extensions are bundled:
L<Atom|XML::Loy::Atom>,
L<Atom-Threading|XML::Loy::Atom::Threading>,
L<ActivityStreams|XML::Loy::ActivityStreams>,
L<GeoRSS|XML::Loy::GeoRSS>,
L<OStatus|XML::Loy::OStatus>,
L<XRD|XML::Loy::XRD>,
and L<HostMeta|XML::Loy::HostMeta>.
If an extension has a leading minus symbol, it is assumed
to be located in the C<XML::Loy> namespace, making C<XML::Loy::Atom>
and C<-Atom> equivalent.

See L<Extensions|/EXTENSIONS> for further information.

B<Note:> The return value of the extension method is experimental
and may change without warnings.


=head2 as

  my $xml = XML::Loy->new('<XRD><Subject>akron</Subject></XRD>');
  my $xrd = $xml->as(-XRD, -HostMeta);

  $xrd->alias('acct:akron@sojolicious.example');

  print $xrd->to_pretty_xml;

  # <XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0"
  #      xmlns:hm="http://host-meta.net/xrd/1.0"
  #      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  #   <Subject>akron</Subject>
  #   <Alias>acct:akron@sojolicious.example</Alias>
  # </XRD>

Convert an L<XML::Loy> based object to another object.
Accepts the base class and optionally a list of extensions.
This only changes the namespace of the base class - extensions
will stay intact.

See L<Extensions|/EXTENSIONS> for further information.

B<Note:> This method is experimental and may change without warnings!


=head2 mime

  print $xml->mime;

The mime type associated with the object class.
See L<Extensions|/EXTENSIONS> for further information.


=head2 namespace

  my $xml = XML::Loy->new('doc');
  $xml->namespace('http://sojolicious.example/ns/global');
  $xml->namespace(fun => 'http://sojolicious.example/ns/fun');
  $xml->add('fun:test' => { foo => 'bar' }, 'Works!');
  print $xml->namespace;

  print $xml->to_pretty_xml;

  # <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  # <doc xmlns="http://sojolicious.example/global"
  #      xmlns:fun="http://sojolicious.example/fun">
  #   <fun:test foo="bar">Works!</fun:test>
  # </doc>

Returns the namespace of the node or
adds namespace information to the node's root.
When adding, the first parameter gives the prefix, the second one
the namespace. The prefix parameter is optional.
Namespaces are always added to the document's root,
that means,
they have to be unique in the scope of the whole document.


=head2 to_pretty_xml

  print $xml->to_pretty_xml;
  print $xml->to_pretty_xml(2);

Returns a stringified, pretty printed XML document.
Optionally accepts a numerical parameter,
defining the start of indentation (defaults to C<0>).


=head1 EXTENSIONS

  package Fun;
  use XML::Loy with => (
    prefix    => 'fun',
    namespace => 'http://sojolicious.example/ns/fun',
    mime      => 'application/fun+xml'
  );

  # Add new methods to the object
  sub add_happy {
    my $self = shift;
    my $word = shift;

    my $cool = $self->add('-Cool');
    my $cry  = uc($word) . '!!! \o/ ';
    $cool->add(Happy => {foo => 'bar'}, $cry);
  };

L<XML::Loy> allows for inheritance
and thus provides two ways of extending the functionality:
By using a derived class as a base class or by extending a
base class with the L<extension|extension> method.

With this package the following extensions are bundled:
L<Atom|XML::Loy::Atom>,
L<Atom-Threading|XML::Loy::Atom::Threading>,
L<ActivityStreams|XML::Loy::ActivityStreams>,
L<GeoRSS|XML::Loy::GeoRSS>,
L<OStatus|XML::Loy::OStatus>,
L<XRD|XML::Loy::XRD>,
and L<HostMeta|XML::Loy::HostMeta>.

For the purpose of extension, three attributes can be set when
L<XML::Loy> is used (introduced with the keyword C<with>).

=over 2

=item

C<namespace> - Namespace of the extension.

=item

C<prefix> - Preferred prefix to associate with the namespace.

=item

C<mime> - Mime type of the base document.

=back

You can use derived objects in your application as you
would do with any other object class.

  package main;
  use Fun;
  my $obj = Fun->new('Fun');
  $obj->add_happy('Yeah!');
  print $obj->to_pretty_xml;

  # <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  # <Fun xmlns="http://sojolicious.example/ns/fun">
  #   <Cool>
  #     <Happy foo="bar">YEAH!!!! \o/ </Happy>
  #   </Cool>
  # </Fun>

The defined namespace is introduced as the document's
namespace. The prefix is not in use for derived classes.

Without any changes to the class, you can use this module as an
extension to another L<XML::Loy> based document as well.

  use XML::Loy;

  my $obj = XML::Loy->new('object');

  # Use XML::Loy based class 'Fun'
  $obj->extension('Fun');

  # Use methods provided by the base class or any extension
  $obj->add_happy('Yeah!');

  # Print with pretty indentation
  print $obj->to_pretty_xml;

  # <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  # <object xmlns:fun="http://sojolicious.example/ns/fun">
  #   <Cool>
  #     <fun:Happy foo="bar">YEAH!!!! \o/ </fun:Happy>
  #   </Cool>
  # </object>

The defined namespace of C<Fun> is introduced with the
prefix C<fun>. The prefix is prepended to all elements
added by the L<add|/add> and L<set|/set> methods in the extension class.
To prevent this prefixing, prepend the element name with
a C<-> (like with C<E<lt>-Cool /E<gt>> in the example
above).

Derived classes are always C<strict> and C<utf8>, use C<warnings>
and import all C<features> of Perl 5.10.


=head1 DEPENDENCIES

L<Mojolicious>, L<Test::Warn> (for testing).


=head1 CAVEATS

L<XML::Loy> focuses on the comfortable handling of small documents of
serialized data and the ease of extensibility.
It is - as well as the underlying parser - written in pure perl and
not intended to be the fastest thing out there
(although I believe there's plenty of space for optimization).
That said - it may not suit all your needs, but there are loads of excellent
XML libraries out there, you can give a try then.
Just to name a few:
For fast parsing of huge documents, try L<XML::Twig>.
For validation and the availability of lots of tools from the XML world,
try L<XML::LibXML>.
For simple deserialization,
try L<XML::Bare> and L<XML::Fast>.
For similar scope, but without dependencies aside the core,
try L<XML::MyXML>.


=head1 CONTRIBUTORS

L<Renée Bäcker|https://github.com/reneeb>


=head1 AVAILABILITY

  https://github.com/Akron/XML-Loy


=head1 COPYRIGHT AND LICENSE

Copyright (C) 2011-2021, L<Nils Diewald|https://www.nils-diewald.de/>.

This program is free software, you can redistribute it
and/or modify it under the same terms as Perl.

=cut
