NAME
    HTML::Acid - Reformat HTML fragment to strict criteria

VERSION
    This document describes HTML::Acid version 0.0.3

SYNOPSIS
        use HTML::Acid;
        my $acid = HTML::Acid->new;
        return $acid->burn($html)
  
DESCRIPTION
    Fragments of HTML returned by a rich text editor tend to be not entirely
    standards compliant. `img' tags tend not to be closed. Paragraphs breaks
    might be represented by double `br' tags rather than `p' tags. Of course
    we also need to do all the XSS avoidance an HTML clean up routine would,
    such as controlling `href' tags, removing javascript and inline styling.
    Furthermore what one often wants is not simply a standards compliant
    cleaned up version of the input HTML. Sometimes one wants to know that
    the HTML conforms to a much tighter standard, as then it will be easier
    to style.

    So this module, given a fragment of HTML, will rewrite it into a very
    restricted subset of XHTML. The default dialect has the following
    properties.

    * Documents consist entirely of `p' elements and `h3' elements.
    * Every header will have `id' attribute automatically generated from the
    header contents.
    * Every paragraph may consist of text, `a' elements, `img' elements,
    `strong' and `em' elements.
    * Anchors must have an `href' attribute referring to an internal URL.
    They may also have a `title' attribute.
    * Images must have `src', `title', `alt', `height' and `width'
    attributes. The `src' attribute must match the same regular expression
    as `href'. If any of these tags are missing the image is replaced by the
    contents of the `alt' attribute, so long as it consists only of
    alphanumeric characters, spaces, full stops and commas. Otherwise the
    image is removed.
    * All other tags must have no attributes and may only contain text.
    * Double `br' elements in the source will be interpreted as paragraph
    breaks.

INTERFACE
  new
    This constructor takes a number of optional named parameters.

    *url_regex*
        This is a regular expression that controls what `href' and `src'
        tags are permitted. It defaults to an expression that restricts
        access to internal absolute paths with an optional sub-reference.

    *tag_hierarchy*
        This is a hash reference that for each supported tag specifies what
        the containing tag must be. Standards based HTML is not as strict as
        this. This defaults to the value returned by the
        `default_tag_hierarchy' method.

    *img_height_default*
        If set this creates a default height value for all images. If not
        set images without height attributes will be rejected.

    *img_width_default*
        If set this creates a default width value for all images. If not set
        images without width attributes will be rejected.

    *text_manip*
        If set this must be subroutine reference. It takes text (and the
        `alt' attribute from invalid images) and what is returned will be
        used instead.

    *text_container*
        If set this must be subroutine reference. It takes the `alt'
        (modified by *text_manip* if present) and returns what would be used
        in the event of an invalid image.

  burn
    This method takes the input HTML as an input and returns the cleaned up
    HTML.

  default_tag_hierarchy
    This is a class method that returns the default tag hierarchy. So if you
    want to add support for a tag you can use a modified copy of the output
    when setting up the HTML::Acid instance. The default mapping is as
    follows:

        {
            h3 => '',
            p => '',
            a => 'p',
            img => 'p',
            em => 'p',
            strong => 'p',
        }

    Mapping an element onto the empty string implies that the element
    appears at the top-level of an HTML fragment. So for example

        h3 => '',
        p => '',

    implies that <h3> and <p> can be at the top of the document fragment.
    Mapping onto another element implies that the element must always be
    contained within that element. So

        a => 'p',
        img => 'p',
        em => 'p',
        strong => 'p',
    
    implies that <a>, <img>, <em> and <strong> must be within a <p> element.
    It is also possible to specify alternatives:

        img => ['p','a'],

    which implies that <img> can be within a <p> or an <a>. Note that this
    code does not check for loops. So doing something like

        div => 'span',
        span => 'div',

    is unsupported.

CONFIGURATION AND ENVIRONMENT
    HTML::Acid requires no configuration files or environment variables.

DEPENDENCIES
    This module works by subclassing HTML::Parser. Also it assumes that the
    input will be in utf8 format, that is it sets the *utf8_mode* flag on
    the HTML::Parser constructor.

INCOMPATIBILITIES
    None reported.

TO DO
    * I think this module could do with an XS back-end for a speed up.
    * There is one bit of the code that the test scripts are not currently
    covering. I need some time to think of a reasonably plausible
    configuration that will trigger those cases.

BUGS AND LIMITATIONS
    No bugs have been reported.

    Please report any bugs or feature requests to
    `bug-html-acid@rt.cpan.org', or through the web interface at
    http://rt.cpan.org.

SEE ALSO
    There are many other modules that do something similar. Of those I think
    the most complete is HTML::StripScripts::Parser. You can also see
    HTML::Declaw, HTML::Clean, HTML::Defang, HTML::Restrict, HTML::Scrubber,
    HTML::Laundary, HTML::Detoxifier, Marpa::HTML, HTML::Tidy. People also
    often refer to HTML::Santitizer.

AUTHOR
    Nicholas Bamber `<nicholas@periapt.co.uk>'

LICENCE AND COPYRIGHT
    Copyright (c) 2010-2011, Nicholas Bamber `<nicholas@periapt.co.uk>'. All
    rights reserved.

    The unordered list in the test files `(t/*/5*)' is issued under the
    Creative Common Attribution-ShareAlike 3.0 Unported License (wikipedia).

    This module is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself. See perlartistic.

DISCLAIMER OF WARRANTY
    BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
    FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
    OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
    PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
    EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
    ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
    YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
    NECESSARY SERVICING, REPAIR, OR CORRECTION.

    IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
    WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
    REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE
    TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR
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    SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
    RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
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