# XML Actions on every node

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## Synopsis
```
use Test;
use XML::Actions;

my Str $file = "a.xml";
$file.IO.spurt(Q:q:to/EOXML/);
  <scxml xmlns="http://www.w3.org/2005/07/scxml"
         version="1.0"
         initial="hello">

    <final id="hello">
      <onentry>
        <log expr="'hello world'" />
      </onentry>
    </final>
  </scxml>
  EOXML


class A is XML::Actions::Work {
  method final ( Array $parent-path, :$id ) {
    is $id, 'hello', "final called: id = $id";
    is $parent-path[*-1].name, 'final', 'this node is final';
    is $parent-path[*-2].name, 'scxml', 'parent node is scxml';

  method log ( Array $parent-path, :$expr ) {
    is $expr, "'hello world'", "log called: expr = $expr";
    is-deeply @$parent-path.map(*.name), <scxml final onentry log>,
              "<scxml final onentry log> found in parent array";
  }
}

my XML::Actions $a .= new(:$file);
isa-ok $a, XML::Actions, 'type ok';
$a.process(:actions(A.new()));

```
Result would be like
```
ok 1 - type ok
ok 2 - final called: id = hello
ok 3 - this node is final
ok 4 - parent node is scxml
ok 5 - log called: expr = 'hello world'
ok 6 - <scxml final onentry log> found in parent array
```

## Documentation

Users who wish to process XML::Elements must provide an instantiated class which inherits from XML::Actions::Work. In that class, methods named after the elements can be defined. The `$parent-path` is an array holding the XML::Elements of the parent elements with the root on the first position and the current element on the last. The attributes are found on the XML element.
```
class A is XML::Actions::Work {

  method someElement ( Array $parent-path, :$someAttribute ... ) {...}
  method someOtherElement ( Array $parent-path, :$someAttribute ... ) {...}
}
```

### Note: clash with existing methods inherited from other classes.
There is an issue (#1) where an element triggered a call to a method from class **Any** and crashed. To prevent this, a method must be added explicitly overriding the method from the inherited class. In the meantime this call will be deprecated in favor of calling a method with `:start` attached to the element name as is done for processing the end tag. This is called an extended identifier where the documentation [can be found here](https://docs.perl6.org/syntax/identifiers#Extended_identifiers). The above example would become;
```
class A is XML::Actions::Work {

  method someElement:start ( Array $parent-path, :$someAttribute ... ) {...}
  method someOtherElement:start ( Array $parent-path, :$someAttribute ... ) {...}
}
```

There are also text-, comment-, cdata- and pi-nodes. They can be defined as
```
  method PROCESS-TEXT ( Array $parent-path, Str $text ) {...}
  method PROCESS-COMMENT ( Array $parent-path, Str $comment ) {...}
  method PROCESS-CDATA ( Array $parent-path, Str $cdata ) {...}
  method PROCESS-PI ( Array $parent-path, Str $pi-target, Str $pi-content ) {...}
```
For uniformity these will also be renamed into `xml:text()`, `xml:comment()`, `xml:cdata()` and `xml:pi()` resp.

If you want to process an element after all children are processed, you can use the same element method with `-END` attached. It has the same number arguments.
  ```
  method someElement-END ( Array $parent-path, :$someAttribute ... ) {...}
  ```
And this one will also be changed into `someElement:end()`.
So after version 0.5.0 the following methods can be called;

* `xml:pi ( Str $target, Str $program )`. For `<?target program?>`.
* `xml:comment ( Str $comment-text )`. For `<!-- comment text -->`.
* `xml:cdata ( Str $data )`. For `<[CDATA[ data ]]>`.
* `xml:text ( Str $text )`. All text as content of an element.

* `someElement:start ( Array $parent-path, *%element-attributes )`
* `someElement:end ( Array $parent-path, *%element-attributes )`

The other methods will get a deprecation message until version 0.5.0.

## Large files
When you have to process a large file (e.g. an XML file holding POI data of Turkey from osm planet is about 6.2 Gb), one cannot use the `XML::Actions` module because the DOM tree is build in memory. Since version 0.4.0 the package is extended with module `XML::Actions::Stream` which eats the file in chunks of 128 Kb and chops it up into parsable parts. There will be no check on proper XML because it will slow it down too much. You can use other tools for that. There are a few more methods possible to be defined by the user. The arguments to the methods are the same but the first argument, which is an array, has other type of elements.

### User definable  methods
The user can define the methods in a class which inherits from XML::Actions::Stream::Work. The methods which the user may define are;

* `xml:prolog ( *%prolog-attributes )`. Found only at start of document. It might have attributes version, encoding and/or standalone.
* `xml:doctype ( *%doctype-attributes )`. Found only at start of document. It might have an internal or external DTD. The arguments can be: `Str :$dtd`, `Str :$url`, `Bool :$empty`, `Bool: $public`, `Bool: $system`, `Str :$fpi`. \$empty is True when there is no DTD, SYSTEM or PUBLIC defined. \$fpi (Formal Public Identifier) should be defined when \$public is True. \$url should be defined when \$system is True but doesn't have to be defined if \$public is True.

* `xml:pi ( Str $target, Str $program )`. For `<?target program?>`.
* `xml:comment ( Str $comment-text )`. For `<!-- comment text -->`.
* `xml:cdata ( Str $data )`. For `<[CDATA[ data ]]>`.
* `xml:text ( Str $text )`. All text as content of an element.

* `someElement:start ( Array $parent-path, Bool :$startend, *%element-attributes )`. The alternative `someElement:startend()` is removed to speedup the process. Instead a named argument is added. When True there is no content in this element.

* `someElement:end ( Array $parent-path, *%element-attributes )`

The array is a list of pairs. The key of each pair is the element name and the value is a hash of its attributes. Entry \$parent-path[\*-1] is the currently called element, so its parent is at \*-2. The root element is at 0 and is always available.

### Changes
One can find the changes document [in ./doc/CHANGES.md][release]

## Installing
Use zef to install the package: `zef install XML::Actions`

## Versions of PERL, MOARVM
This project is tested against the newest perl6 version with Rakudo built on MoarVM implementing Perl v6.

## AUTHORS
Current maintainer **Marcel Timmerman** (MARTIMM on github)

## License
**Artistic-2.0**

<!---- [refs] ----------------------------------------------------------------->
[release]: https://github.com/MARTIMM/XmlActions/blob/master/doc/CHANGES.md
