4 use warnings FATAL => 'all';
6 use HTML::Zoom::ZConfig;
7 use HTML::Zoom::ReadFH;
8 use HTML::Zoom::Transform;
9 use HTML::Zoom::TransformBuilder;
11 our $VERSION = '0.009001';
13 $VERSION = eval $VERSION;
16 my ($class, $args) = @_;
18 $new->{zconfig} = HTML::Zoom::ZConfig->new($args->{zconfig}||{});
22 sub zconfig { shift->_self_or_new->{zconfig} }
25 ref($_[0]) ? $_[0] : $_[0]->new
29 bless({ %{$_[0]}, %{$_[1]} }, ref($_[0]));
33 my $self = shift->_self_or_new;
35 initial_events => shift,
40 my $self = shift->_self_or_new;
41 $self->from_events($self->zconfig->parser->html_to_events($_[0]))
45 my $self = shift->_self_or_new;
47 $self->from_html(do { local (@ARGV, $/) = ($filename); <> });
52 die "No events to build from - forgot to call from_html?"
53 unless $self->{initial_events};
54 my $sutils = $self->zconfig->stream_utils;
55 my $stream = $sutils->stream_from_array(@{$self->{initial_events}});
56 $stream = $_->apply_to_stream($stream) for @{$self->{transforms}||[]};
61 HTML::Zoom::ReadFH->from_zoom(shift);
66 [ $self->zconfig->stream_utils->stream_to_array($self->to_stream) ];
76 my ($self, $code) = @_;
83 $self->zconfig->producer->html_from_stream($self->to_stream);
88 ref($self)->new($self)->from_html($self->to_html);
92 my $self = shift->_self_or_new;
96 @{$self->{transforms}||[]},
103 my $self = shift->_self_or_new;
104 my ($selector, $filter) = @_;
105 $self->with_transform(
106 HTML::Zoom::Transform->new({
107 zconfig => $self->zconfig,
108 selector => $selector,
109 filters => [ $filter ]
115 my $self = shift->_self_or_new;
117 return HTML::Zoom::TransformBuilder->new({
118 zconfig => $self->zconfig,
119 selector => $selector,
124 # There's a bug waiting to happen here: if you do something like
126 # $zoom->select('.foo')
127 # ->remove_attribute(class => 'foo')
129 # ->well_anything_really
131 # the second action won't execute because it doesn't match anymore.
132 # Ideally instead we'd merge the match subs but that's more complex to
133 # implement so I'm deferring it for the moment.
137 die "Can't call ->then without a previous transform"
138 unless $self->{transforms};
139 $self->select($self->{transforms}->[-1]->selector);
146 HTML::Zoom - selector based streaming template engine
152 my $template = <<HTML;
155 <title>Hello people</title>
158 <h1 id="greeting">Placeholder</h1>
161 <p>Name: <span class="name">Bob</span></p>
162 <p>Age: <span class="age">23</span></p>
164 <hr class="between" />
170 my $output = HTML::Zoom
171 ->from_html($template)
172 ->select('title, #greeting')->replace_content('Hello world & dog!')
173 ->select('#list')->repeat_content(
176 $_->select('.name')->replace_content('Matt')
177 ->select('.age')->replace_content('26')
180 $_->select('.name')->replace_content('Mark')
181 ->select('.age')->replace_content('0x29')
184 $_->select('.name')->replace_content('Epitaph')
185 ->select('.age')->replace_content('<redacted>')
188 { repeat_between => '.between' }
202 <title>Hello world & dog!</title>
205 <h1 id="greeting">Hello world & dog!</h1>
208 <p>Name: <span class="name">Matt</span></p>
209 <p>Age: <span class="age">26</span></p>
211 <hr class="between" />
213 <p>Name: <span class="name">Mark</span></p>
214 <p>Age: <span class="age">0x29</span></p>
216 <hr class="between" />
218 <p>Name: <span class="name">Epitaph</span></p>
219 <p>Age: <span class="age"><redacted></span></p>
229 is($output, $expect, 'Synopsis code works ok');
233 =head1 DANGER WILL ROBINSON
235 This is a 0.9 release. That means that I'm fairly happy the API isn't going
236 to change in surprising and upsetting ways before 1.0 and a real compatibility
237 freeze. But it also means that if it turns out there's a mistake the size of
238 a politician's ego in the API design that I haven't spotted yet there may be
239 a bit of breakage between here and 1.0. Hopefully not though. Appendages
240 crossed and all that.
242 Worse still, the rest of the distribution isn't documented yet. I'm sorry.
243 I suck. But lots of people have been asking me to ship this, docs or no, so
244 having got this class itself at least somewhat documented I figured now was
245 a good time to cut a first real release.
249 HTML::Zoom is a lazy, stream oriented, streaming capable, mostly functional,
250 CSS selector based semantic templating engine for HTML and HTML-like
253 Which is, on the whole, a bit of a mouthful. So let me step back a moment
254 and explain why you care enough to understand what I mean:
258 HTML::Zoom is the cure for JQuery envy. When your javascript guy pushes a
259 piece of data into a document by doing:
261 $('.username').replaceAll(username);
263 In HTML::Zoom one can write
265 $zoom->select('.username')->replace_content($username);
267 which is, I hope, almost as clear, hampered only by the fact that Zoom can't
268 assume a global document and therefore has nothing quite so simple as the
269 $() function to get the initial selection.
271 L<HTML::Zoom::SelectorParser> implements a subset of the JQuery selector
272 specification, and will continue to track that rather than the W3C standards
273 for the forseeable future on grounds of pragmatism. Also on grounds of their
274 spec is written in EN_US rather than EN_W3C, and I read the former much better.
276 I am happy to admit that it's very, very much a subset at the moment - see the
277 L<HTML::Zoom::SelectorParser> POD for what's currently there, and expect more
278 and more to be supported over time as we need it and patch it in.
280 =head2 CLEAN TEMPLATES
282 HTML::Zoom is the cure for messy templates. How many times have you looked at
285 <form action="/somewhere">
286 [% FOREACH field IN fields %]
287 <label for="[% field.id %]">[% field.label %]</label>
288 <input name="[% field.name %]" type="[% field.type %]" value="[% field.value %]" />
292 and despaired of the fact that neither the HTML structure nor the logic are
293 remotely easy to read? Fortunately, with HTML::Zoom we can separate the two
296 <form class="myform" action="/somewhere">
301 $zoom->select('.myform')->repeat_content([
302 map { my $field = $_; sub {
305 ->add_to_attribute( for => $field->{id} )
307 ->replace_content( $field->{label} )
310 ->add_to_attribute( name => $field->{name} )
312 ->add_to_attribute( type => $field->{type} )
314 ->add_to_attribute( value => $field->{value} )
319 This is, admittedly, very much not shorter. However, it makes it extremely
320 clear what's happening and therefore less hassle to maintain. Especially
321 because it allows the designer to fiddle with the HTML without cutting
322 himself on sharp ELSE clauses, and the developer to add available data to
323 the template without getting angle bracket cuts on sensitive parts.
325 Better still, HTML::Zoom knows that it's inserting content into HTML and
326 can escape it for you - the example template should really have been:
328 <form action="/somewhere">
329 [% FOREACH field IN fields %]
330 <label for="[% field.id | html %]">[% field.label | html %]</label>
331 <input name="[% field.name | html %]" type="[% field.type | html %]" value="[% field.value | html %]" />
335 and frankly I'll take slightly more code any day over *that* crawling horror.
337 (addendum: I pick on L<Template Toolkit|Template> here specifically because
338 it's the template system I hate the least - for text templating, I don't
339 honestly think I'll ever like anything except the next version of Template
340 Toolkit better - but HTML isn't text. Zoom knows that. Do you?)
342 =head2 PUTTING THE FUN INTO FUNCTIONAL
344 The principle of HTML::Zoom is to provide a reusable, functional container
345 object that lets you build up a set of transforms to be applied; every method
346 call you make on a zoom object returns a new object, so it's safe to do so
347 on one somebody else gave you without worrying about altering state (with
348 the notable exception of ->next for stream objects, which I'll come to later).
352 my $z2 = $z1->select('.name')->replace_content($name);
354 my $z3 = $z2->select('.title')->replace_content('Ms.');
356 each time produces a new Zoom object. If you want to package up a set of
357 transforms to re-use, HTML::Zoom provides an 'apply' method:
359 my $add_name = sub { $_->select('.name')->replace_content($name) };
361 my $same_as_z2 = $z1->apply($add_name);
363 =head2 LAZINESS IS A VIRTUE
365 HTML::Zoom does its best to defer doing anything until it's absolutely
366 required. The only point at which it descends into state is when you force
367 it to create a stream, directly by:
369 my $stream = $zoom->to_stream;
371 while (my $evt = $stream->next) {
372 # handle zoom event here
377 my $final_html = $zoom->to_html;
379 my $fh = $zoom->to_fh;
381 while (my $chunk = $fh->getline) {
385 Better still, the $fh returned doesn't create its stream until the first
386 call to getline, which means that until you call that and force it to be
387 stateful you can get back to the original stateless Zoom object via:
389 my $zoom = $fh->to_zoom;
391 which is exceedingly handy for filtering L<Plack> PSGI responses, among other
394 Because HTML::Zoom doesn't try and evaluate everything up front, you can
395 generally put things together in whatever order is most appropriate. This
398 my $start = HTML::Zoom->from_html($html);
400 my $zoom = $start->select('div')->replace_content('THIS IS A DIV!');
404 my $start = HTML::Zoom->select('div')->replace_content('THIS IS A DIV!');
406 my $zoom = $start->from_html($html);
408 will produce equivalent final $zoom objects, thus proving that there can be
409 more than one way to do it without one of them being a
410 L<bait and switch|Switch>.
412 =head2 STOCKTON TO DARLINGTON UNDER STREAM POWER
414 HTML::Zoom's execution always happens in terms of streams under the hood
415 - that is, the basic pattern for doing anything is -
417 my $stream = get_stream_from_somewhere
419 while (my ($evt) = $stream->next) {
420 # do something with the event
423 More importantly, all selectors and filters are also built as stream
424 operations, so a selector and filter pair is effectively:
428 my $next_evt = $self->parent_stream->next;
429 if ($self->selector_matches($next_evt)) {
430 return $self->apply_filter_to($next_evt);
436 Internally, things are marginally more complicated than that, but not enough
437 that you as a user should normally need to care.
439 In fact, an HTML::Zoom object is mostly just a container for the relevant
440 information from which to build the final stream that does the real work. A
441 stream built from a Zoom object is a stream of events from parsing the
442 initial HTML, wrapped in a filter stream per selector/filter pair provided
445 The upshot of this is that the application of filters works just as well on
446 streams as on the original Zoom object - in fact, when you run a
447 L</repeat_content> operation your subroutines are applied to the stream for
448 that element of the repeat, rather than constructing a new zoom per repeat
453 $_->select('div')->replace_content('I AM A DIV!');
455 works on both HTML::Zoom objects themselves and HTML::Zoom stream objects and
456 shares sufficient of the implementation that you can generally forget the
457 difference - barring the fact that a stream already has state attached so
458 things like to_fh are no longer available.
460 =head2 POP! GOES THE WEASEL
462 ... and by Weasel, I mean layout.
464 HTML::Zoom's filehandle object supports an additional event key, 'flush',
465 that is transparent to the rest of the system but indicates to the filehandle
466 object to end a getline operation at that point and return the HTML so far.
468 This means that in an environment where streaming output is available, such
469 as a number of the L<Plack> PSGI handlers, you can add the flush key to an
470 event in order to ensure that the HTML generated so far is flushed through
471 to the browser right now. This can be especially useful if you know you're
472 about to call a web service or a potentially slow database query or similar
473 to ensure that at least the header/layout of your page renders now, improving
474 perceived user responsiveness while your application waits around for the
477 This is currently exposed by the 'flush_before' option to the collect filter,
478 which incidentally also underlies the replace and repeat filters, so to
479 indicate we want this behaviour to happen before a query is executed we can
480 write something like:
482 $zoom->select('.item')->repeat(sub {
483 if (my $row = $db_thing->next) {
484 return sub { $_->select('.item-name')->replace_content($row->name) }
488 }, { flush_before => 1 });
490 which should have the desired effect given a sufficiently lazy $db_thing (for
491 example a L<DBIx::Class::ResultSet> object).
493 =head2 A FISTFUL OF OBJECTS
495 At the core of an HTML::Zoom system lurks an L<HTML::Zoom::ZConfig> object,
496 whose purpose is to hang on to the various bits and pieces that things need
497 so that there's a common way of accessing shared functionality.
499 Were I a computer scientist I would probably call this an "Inversion of
500 Control" object - which you'd be welcome to google to learn more about, or
501 you can just imagine a computer scientist being suspended upside down over
502 a pit. Either way works for me, I'm a pure maths grad.
504 The ZConfig object hangs on to one each of the following for you:
508 =item * An HTML parser, normally L<HTML::Zoom::Parser::BuiltIn>
510 =item * An HTML producer (emitter), normally L<HTML::Zoom::Producer::BuiltIn>
512 =item * An object to build event filters, normally L<HTML::Zoom::FilterBuilder>
514 =item * An object to parse CSS selectors, normally L<HTML::Zoom::SelectorParser>
516 =item * An object to build streams, normally L<HTML::Zoom::StreamUtils>
520 In theory you could replace any of these with anything you like, but in
521 practice you're probably best restricting yourself to subclasses, or at
522 least things that manage to look like the original if you squint a bit.
524 If you do something more clever than that, or find yourself overriding things
525 in your ZConfig a lot, please please tell us about it via one of the means
526 mentioned under L</SUPPORT>.
528 =head2 SEMANTIC DIDACTIC
530 Some will argue that overloading CSS selectors to do data stuff is a terrible
531 idea, and possibly even a step towards the "Concrete Javascript" pattern
532 (which I abhor) or Smalltalk's Morphic (which I ignore, except for the part
533 where it keeps reminding me of the late, great Tony Hart's plasticine friend).
535 To which I say, "eh", "meh", and possibly also "feh". If it really upsets
536 you, either use extra classes for this (and remove them afterwards) or
537 use special fake elements or, well, honestly, just use something different.
538 L<Template::Semantic> provides a similar idea to zoom except using XPath
539 and XML::LibXML transforms rather than a lightweight streaming approach -
540 maybe you'd like that better. Or maybe you really did want
541 L<Template Toolkit|Template> after all. It is still damn good at what it does,
544 So far, however, I've found that for new sites the designers I'm working with
545 generally want to produce nice semantic HTML with classes that represent the
546 nature of the data rather than the structure of the layout, so sharing them
547 as a common interface works really well for us.
549 In the absence of any evidence that overloading CSS selectors has killed
550 children or unexpectedly set fire to grandmothers - and given microformats
551 have been around for a while there's been plenty of opportunity for
552 octagenarian combustion - I'd suggest you give it a try and see if you like it.
554 =head2 GET THEE TO A SUMMARY!
558 HTML::Zoom is a lazy, stream oriented, streaming capable, mostly functional,
559 CSS selector based semantic templating engine for HTML and HTML-like
562 But I said that already. Although hopefully by now you have some idea what I
563 meant when I said it. If you didn't have any idea the first time. I mean, I'm
564 not trying to call you stupid or anything. Just saying that maybe it wasn't
565 totally obvious without the explanation. Or something.
569 Maybe we should just move on to the method docs.
575 my $zoom = HTML::Zoom->new;
577 my $zoom = HTML::Zoom->new({ zconfig => $zconfig });
579 Create a new empty Zoom object. You can optionally pass an
580 L<HTML::Zoom::ZConfig> instance if you're trying to override one or more of
581 the default components.
583 This method isn't often used directly since several other methods can also
584 act as constructors, notable L</select> and L</from_html>
588 my $zconfig = $zoom->zconfig;
590 Retrieve the L<HTML::Zoom::ZConfig> instance used by this Zoom object. You
591 shouldn't usually need to call this yourself.
595 my $zoom = HTML::Zoom->from_html($html);
597 my $z2 = $z1->from_html($html);
599 Parses the HTML using the current zconfig's parser object and returns a new
600 zoom instance with that as the source HTML to be transformed.
604 my $zoom = HTML::Zoom->from_file($file);
606 my $z2 = $z1->from_file($file);
608 Convenience method - slurps the contents of $file and calls from_html with it.
612 my $stream = $zoom->to_stream;
614 while (my ($evt) = $stream->next) {
617 Creates a stream, starting with a stream of the events from the HTML supplied
618 via L</from_html> and then wrapping it in turn with each selector+filter pair
619 that have been applied to the zoom object.
623 my $fh = $zoom->to_fh;
625 call_something_expecting_a_filehandle($fh);
627 Returns an L<HTML::Zoom::ReadFH> instance that will create a stream the first
628 time its getline method is called and then return all HTML up to the next
629 event with 'flush' set.
631 You can pass this filehandle to compliant PSGI handlers (and probably most
638 Runs the zoom object's transforms without doing anything with the results.
640 Normally used to get side effects of a zoom run - for example when using
641 L<HTML::Zoom::FilterBuilder/collect> to slurp events for scraping or layout.
645 my $z2 = $z1->apply(sub {
646 $_->select('div')->replace_content('I AM A DIV!') })
649 Sets $_ to the zoom object and then runs the provided code. Basically syntax
650 sugar, the following is entirely equivalent:
653 shift->select('div')->replace_content('I AM A DIV!') })
656 my $z2 = $sub->($z1);
660 my $html = $zoom->to_html;
662 Runs the zoom processing and returns the resulting HTML.
666 my $z2 = $z1->memoize;
668 Creates a new zoom whose source HTML is the results of the original zoom's
669 processing. Effectively syntax sugar for:
671 my $z2 = HTML::Zoom->from_html($z1->to_html);
673 but preserves your L<HTML::Zoom::ZConfig> object.
677 my $zoom = HTML::Zoom->with_filter(
678 'div', $filter_builder->replace_content('I AM A DIV!')
681 my $z2 = $z1->with_filter(
682 'div', $filter_builder->replace_content('I AM A DIV!')
685 Lower level interface than L</select> to adding filters to your zoom object.
687 In normal usage, you probably don't need to call this yourself.
691 my $zoom = HTML::Zoom->select('div')->replace_content('I AM A DIV!');
693 my $z2 = $z1->select('div')->replace_content('I AM A DIV!');
695 Returns an intermediary object of the class L<HTML::Zoom::TransformBuilder>
696 on which methods of your L<HTML::Zoom::FilterBuilder> object can be called.
698 In normal usage you should generally always put the pair of method calls
699 together; the intermediary object isn't designed or expected to stick around.
703 my $z2 = $z1->select('div')->add_to_attribute(class => 'spoon')
705 ->replace_content('I AM A DIV!');
707 Re-runs the previous select to allow you to chain actions together on the
714 =item * Matt S. Trout
720 This library is free software, you can redistribute it and/or modify
721 it under the same terms as Perl itself.