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, $code) = @_;
82 my ($self, $predicate, $code) = @_;
94 $self->zconfig->producer->html_from_stream($self->to_stream);
99 ref($self)->new($self)->from_html($self->to_html);
103 my $self = shift->_self_or_new;
104 my ($transform) = @_;
107 @{$self->{transforms}||[]},
114 my $self = shift->_self_or_new;
115 my ($selector, $filter) = @_;
116 $self->with_transform(
117 HTML::Zoom::Transform->new({
118 zconfig => $self->zconfig,
119 selector => $selector,
120 filters => [ $filter ]
126 my $self = shift->_self_or_new;
128 return HTML::Zoom::TransformBuilder->new({
129 zconfig => $self->zconfig,
130 selector => $selector,
135 # There's a bug waiting to happen here: if you do something like
137 # $zoom->select('.foo')
138 # ->remove_attribute(class => 'foo')
140 # ->well_anything_really
142 # the second action won't execute because it doesn't match anymore.
143 # Ideally instead we'd merge the match subs but that's more complex to
144 # implement so I'm deferring it for the moment.
148 die "Can't call ->then without a previous transform"
149 unless $self->{transforms};
150 $self->select($self->{transforms}->[-1]->selector);
157 HTML::Zoom - selector based streaming template engine
163 my $template = <<HTML;
166 <title>Hello people</title>
169 <h1 id="greeting">Placeholder</h1>
172 <p>Name: <span class="name">Bob</span></p>
173 <p>Age: <span class="age">23</span></p>
175 <hr class="between" />
181 my $output = HTML::Zoom
182 ->from_html($template)
183 ->select('title, #greeting')->replace_content('Hello world & dog!')
184 ->select('#list')->repeat_content(
187 $_->select('.name')->replace_content('Matt')
188 ->select('.age')->replace_content('26')
191 $_->select('.name')->replace_content('Mark')
192 ->select('.age')->replace_content('0x29')
195 $_->select('.name')->replace_content('Epitaph')
196 ->select('.age')->replace_content('<redacted>')
199 { repeat_between => '.between' }
213 <title>Hello world & dog!</title>
216 <h1 id="greeting">Hello world & dog!</h1>
219 <p>Name: <span class="name">Matt</span></p>
220 <p>Age: <span class="age">26</span></p>
222 <hr class="between" />
224 <p>Name: <span class="name">Mark</span></p>
225 <p>Age: <span class="age">0x29</span></p>
227 <hr class="between" />
229 <p>Name: <span class="name">Epitaph</span></p>
230 <p>Age: <span class="age"><redacted></span></p>
240 is($output, $expect, 'Synopsis code works ok');
244 =head1 DANGER WILL ROBINSON
246 This is a 0.9 release. That means that I'm fairly happy the API isn't going
247 to change in surprising and upsetting ways before 1.0 and a real compatibility
248 freeze. But it also means that if it turns out there's a mistake the size of
249 a politician's ego in the API design that I haven't spotted yet there may be
250 a bit of breakage between here and 1.0. Hopefully not though. Appendages
251 crossed and all that.
253 Worse still, the rest of the distribution isn't documented yet. I'm sorry.
254 I suck. But lots of people have been asking me to ship this, docs or no, so
255 having got this class itself at least somewhat documented I figured now was
256 a good time to cut a first real release.
260 HTML::Zoom is a lazy, stream oriented, streaming capable, mostly functional,
261 CSS selector based semantic templating engine for HTML and HTML-like
264 Which is, on the whole, a bit of a mouthful. So let me step back a moment
265 and explain why you care enough to understand what I mean:
269 HTML::Zoom is the cure for JQuery envy. When your javascript guy pushes a
270 piece of data into a document by doing:
272 $('.username').replaceAll(username);
274 In HTML::Zoom one can write
276 $zoom->select('.username')->replace_content($username);
278 which is, I hope, almost as clear, hampered only by the fact that Zoom can't
279 assume a global document and therefore has nothing quite so simple as the
280 $() function to get the initial selection.
282 L<HTML::Zoom::SelectorParser> implements a subset of the JQuery selector
283 specification, and will continue to track that rather than the W3C standards
284 for the forseeable future on grounds of pragmatism. Also on grounds of their
285 spec is written in EN_US rather than EN_W3C, and I read the former much better.
287 I am happy to admit that it's very, very much a subset at the moment - see the
288 L<HTML::Zoom::SelectorParser> POD for what's currently there, and expect more
289 and more to be supported over time as we need it and patch it in.
291 =head2 CLEAN TEMPLATES
293 HTML::Zoom is the cure for messy templates. How many times have you looked at
296 <form action="/somewhere">
297 [% FOREACH field IN fields %]
298 <label for="[% field.id %]">[% field.label %]</label>
299 <input name="[% field.name %]" type="[% field.type %]" value="[% field.value %]" />
303 and despaired of the fact that neither the HTML structure nor the logic are
304 remotely easy to read? Fortunately, with HTML::Zoom we can separate the two
307 <form class="myform" action="/somewhere">
312 $zoom->select('.myform')->repeat_content([
313 map { my $field = $_; sub {
316 ->add_to_attribute( for => $field->{id} )
318 ->replace_content( $field->{label} )
321 ->add_to_attribute( name => $field->{name} )
323 ->add_to_attribute( type => $field->{type} )
325 ->add_to_attribute( value => $field->{value} )
330 This is, admittedly, very much not shorter. However, it makes it extremely
331 clear what's happening and therefore less hassle to maintain. Especially
332 because it allows the designer to fiddle with the HTML without cutting
333 himself on sharp ELSE clauses, and the developer to add available data to
334 the template without getting angle bracket cuts on sensitive parts.
336 Better still, HTML::Zoom knows that it's inserting content into HTML and
337 can escape it for you - the example template should really have been:
339 <form action="/somewhere">
340 [% FOREACH field IN fields %]
341 <label for="[% field.id | html %]">[% field.label | html %]</label>
342 <input name="[% field.name | html %]" type="[% field.type | html %]" value="[% field.value | html %]" />
346 and frankly I'll take slightly more code any day over *that* crawling horror.
348 (addendum: I pick on L<Template Toolkit|Template> here specifically because
349 it's the template system I hate the least - for text templating, I don't
350 honestly think I'll ever like anything except the next version of Template
351 Toolkit better - but HTML isn't text. Zoom knows that. Do you?)
353 =head2 PUTTING THE FUN INTO FUNCTIONAL
355 The principle of HTML::Zoom is to provide a reusable, functional container
356 object that lets you build up a set of transforms to be applied; every method
357 call you make on a zoom object returns a new object, so it's safe to do so
358 on one somebody else gave you without worrying about altering state (with
359 the notable exception of ->next for stream objects, which I'll come to later).
363 my $z2 = $z1->select('.name')->replace_content($name);
365 my $z3 = $z2->select('.title')->replace_content('Ms.');
367 each time produces a new Zoom object. If you want to package up a set of
368 transforms to re-use, HTML::Zoom provides an 'apply' method:
370 my $add_name = sub { $_->select('.name')->replace_content($name) };
372 my $same_as_z2 = $z1->apply($add_name);
374 =head2 LAZINESS IS A VIRTUE
376 HTML::Zoom does its best to defer doing anything until it's absolutely
377 required. The only point at which it descends into state is when you force
378 it to create a stream, directly by:
380 my $stream = $zoom->to_stream;
382 while (my $evt = $stream->next) {
383 # handle zoom event here
388 my $final_html = $zoom->to_html;
390 my $fh = $zoom->to_fh;
392 while (my $chunk = $fh->getline) {
396 Better still, the $fh returned doesn't create its stream until the first
397 call to getline, which means that until you call that and force it to be
398 stateful you can get back to the original stateless Zoom object via:
400 my $zoom = $fh->to_zoom;
402 which is exceedingly handy for filtering L<Plack> PSGI responses, among other
405 Because HTML::Zoom doesn't try and evaluate everything up front, you can
406 generally put things together in whatever order is most appropriate. This
409 my $start = HTML::Zoom->from_html($html);
411 my $zoom = $start->select('div')->replace_content('THIS IS A DIV!');
415 my $start = HTML::Zoom->select('div')->replace_content('THIS IS A DIV!');
417 my $zoom = $start->from_html($html);
419 will produce equivalent final $zoom objects, thus proving that there can be
420 more than one way to do it without one of them being a
421 L<bait and switch|Switch>.
423 =head2 STOCKTON TO DARLINGTON UNDER STREAM POWER
425 HTML::Zoom's execution always happens in terms of streams under the hood
426 - that is, the basic pattern for doing anything is -
428 my $stream = get_stream_from_somewhere
430 while (my ($evt) = $stream->next) {
431 # do something with the event
434 More importantly, all selectors and filters are also built as stream
435 operations, so a selector and filter pair is effectively:
439 my $next_evt = $self->parent_stream->next;
440 if ($self->selector_matches($next_evt)) {
441 return $self->apply_filter_to($next_evt);
447 Internally, things are marginally more complicated than that, but not enough
448 that you as a user should normally need to care.
450 In fact, an HTML::Zoom object is mostly just a container for the relevant
451 information from which to build the final stream that does the real work. A
452 stream built from a Zoom object is a stream of events from parsing the
453 initial HTML, wrapped in a filter stream per selector/filter pair provided
456 The upshot of this is that the application of filters works just as well on
457 streams as on the original Zoom object - in fact, when you run a
458 L</repeat_content> operation your subroutines are applied to the stream for
459 that element of the repeat, rather than constructing a new zoom per repeat
464 $_->select('div')->replace_content('I AM A DIV!');
466 works on both HTML::Zoom objects themselves and HTML::Zoom stream objects and
467 shares sufficient of the implementation that you can generally forget the
468 difference - barring the fact that a stream already has state attached so
469 things like to_fh are no longer available.
471 =head2 POP! GOES THE WEASEL
473 ... and by Weasel, I mean layout.
475 HTML::Zoom's filehandle object supports an additional event key, 'flush',
476 that is transparent to the rest of the system but indicates to the filehandle
477 object to end a getline operation at that point and return the HTML so far.
479 This means that in an environment where streaming output is available, such
480 as a number of the L<Plack> PSGI handlers, you can add the flush key to an
481 event in order to ensure that the HTML generated so far is flushed through
482 to the browser right now. This can be especially useful if you know you're
483 about to call a web service or a potentially slow database query or similar
484 to ensure that at least the header/layout of your page renders now, improving
485 perceived user responsiveness while your application waits around for the
488 This is currently exposed by the 'flush_before' option to the collect filter,
489 which incidentally also underlies the replace and repeat filters, so to
490 indicate we want this behaviour to happen before a query is executed we can
491 write something like:
493 $zoom->select('.item')->repeat(sub {
494 if (my $row = $db_thing->next) {
495 return sub { $_->select('.item-name')->replace_content($row->name) }
499 }, { flush_before => 1 });
501 which should have the desired effect given a sufficiently lazy $db_thing (for
502 example a L<DBIx::Class::ResultSet> object).
504 =head2 A FISTFUL OF OBJECTS
506 At the core of an HTML::Zoom system lurks an L<HTML::Zoom::ZConfig> object,
507 whose purpose is to hang on to the various bits and pieces that things need
508 so that there's a common way of accessing shared functionality.
510 Were I a computer scientist I would probably call this an "Inversion of
511 Control" object - which you'd be welcome to google to learn more about, or
512 you can just imagine a computer scientist being suspended upside down over
513 a pit. Either way works for me, I'm a pure maths grad.
515 The ZConfig object hangs on to one each of the following for you:
519 =item * An HTML parser, normally L<HTML::Zoom::Parser::BuiltIn>
521 =item * An HTML producer (emitter), normally L<HTML::Zoom::Producer::BuiltIn>
523 =item * An object to build event filters, normally L<HTML::Zoom::FilterBuilder>
525 =item * An object to parse CSS selectors, normally L<HTML::Zoom::SelectorParser>
527 =item * An object to build streams, normally L<HTML::Zoom::StreamUtils>
531 In theory you could replace any of these with anything you like, but in
532 practice you're probably best restricting yourself to subclasses, or at
533 least things that manage to look like the original if you squint a bit.
535 If you do something more clever than that, or find yourself overriding things
536 in your ZConfig a lot, please please tell us about it via one of the means
537 mentioned under L</SUPPORT>.
539 =head2 SEMANTIC DIDACTIC
541 Some will argue that overloading CSS selectors to do data stuff is a terrible
542 idea, and possibly even a step towards the "Concrete Javascript" pattern
543 (which I abhor) or Smalltalk's Morphic (which I ignore, except for the part
544 where it keeps reminding me of the late, great Tony Hart's plasticine friend).
546 To which I say, "eh", "meh", and possibly also "feh". If it really upsets
547 you, either use extra classes for this (and remove them afterwards) or
548 use special fake elements or, well, honestly, just use something different.
549 L<Template::Semantic> provides a similar idea to zoom except using XPath
550 and XML::LibXML transforms rather than a lightweight streaming approach -
551 maybe you'd like that better. Or maybe you really did want
552 L<Template Toolkit|Template> after all. It is still damn good at what it does,
555 So far, however, I've found that for new sites the designers I'm working with
556 generally want to produce nice semantic HTML with classes that represent the
557 nature of the data rather than the structure of the layout, so sharing them
558 as a common interface works really well for us.
560 In the absence of any evidence that overloading CSS selectors has killed
561 children or unexpectedly set fire to grandmothers - and given microformats
562 have been around for a while there's been plenty of opportunity for
563 octagenarian combustion - I'd suggest you give it a try and see if you like it.
565 =head2 GET THEE TO A SUMMARY!
569 HTML::Zoom is a lazy, stream oriented, streaming capable, mostly functional,
570 CSS selector based semantic templating engine for HTML and HTML-like
573 But I said that already. Although hopefully by now you have some idea what I
574 meant when I said it. If you didn't have any idea the first time. I mean, I'm
575 not trying to call you stupid or anything. Just saying that maybe it wasn't
576 totally obvious without the explanation. Or something.
580 Maybe we should just move on to the method docs.
586 my $zoom = HTML::Zoom->new;
588 my $zoom = HTML::Zoom->new({ zconfig => $zconfig });
590 Create a new empty Zoom object. You can optionally pass an
591 L<HTML::Zoom::ZConfig> instance if you're trying to override one or more of
592 the default components.
594 This method isn't often used directly since several other methods can also
595 act as constructors, notable L</select> and L</from_html>
599 my $zconfig = $zoom->zconfig;
601 Retrieve the L<HTML::Zoom::ZConfig> instance used by this Zoom object. You
602 shouldn't usually need to call this yourself.
606 my $zoom = HTML::Zoom->from_html($html);
608 my $z2 = $z1->from_html($html);
610 Parses the HTML using the current zconfig's parser object and returns a new
611 zoom instance with that as the source HTML to be transformed.
615 my $zoom = HTML::Zoom->from_file($file);
617 my $z2 = $z1->from_file($file);
619 Convenience method - slurps the contents of $file and calls from_html with it.
623 my $stream = $zoom->to_stream;
625 while (my ($evt) = $stream->next) {
628 Creates a stream, starting with a stream of the events from the HTML supplied
629 via L</from_html> and then wrapping it in turn with each selector+filter pair
630 that have been applied to the zoom object.
634 my $fh = $zoom->to_fh;
636 call_something_expecting_a_filehandle($fh);
638 Returns an L<HTML::Zoom::ReadFH> instance that will create a stream the first
639 time its getline method is called and then return all HTML up to the next
640 event with 'flush' set.
642 You can pass this filehandle to compliant PSGI handlers (and probably most
649 Runs the zoom object's transforms without doing anything with the results.
651 Normally used to get side effects of a zoom run - for example when using
652 L<HTML::Zoom::FilterBuilder/collect> to slurp events for scraping or layout.
656 my $z2 = $z1->apply(sub {
657 $_->select('div')->replace_content('I AM A DIV!') })
660 Sets $_ to the zoom object and then runs the provided code. Basically syntax
661 sugar, the following is entirely equivalent:
664 shift->select('div')->replace_content('I AM A DIV!') })
667 my $z2 = $sub->($z1);
671 my $html = $zoom->to_html;
673 Runs the zoom processing and returns the resulting HTML.
677 my $z2 = $z1->memoize;
679 Creates a new zoom whose source HTML is the results of the original zoom's
680 processing. Effectively syntax sugar for:
682 my $z2 = HTML::Zoom->from_html($z1->to_html);
684 but preserves your L<HTML::Zoom::ZConfig> object.
688 my $zoom = HTML::Zoom->with_filter(
689 'div', $filter_builder->replace_content('I AM A DIV!')
692 my $z2 = $z1->with_filter(
693 'div', $filter_builder->replace_content('I AM A DIV!')
696 Lower level interface than L</select> to adding filters to your zoom object.
698 In normal usage, you probably don't need to call this yourself.
702 my $zoom = HTML::Zoom->select('div')->replace_content('I AM A DIV!');
704 my $z2 = $z1->select('div')->replace_content('I AM A DIV!');
706 Returns an intermediary object of the class L<HTML::Zoom::TransformBuilder>
707 on which methods of your L<HTML::Zoom::FilterBuilder> object can be called.
709 In normal usage you should generally always put the pair of method calls
710 together; the intermediary object isn't designed or expected to stick around.
714 my $z2 = $z1->select('div')->add_to_attribute(class => 'spoon')
716 ->replace_content('I AM A DIV!');
718 Re-runs the previous select to allow you to chain actions together on the
725 =item * Matt S. Trout
731 This library is free software, you can redistribute it and/or modify
732 it under the same terms as Perl itself.