Context

Context is package that aims to collect "context" to pass to templates based on a query object.

Best paired with a template engine. And maybe with Hierarchy.

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Quick start

Let's assume a couple of classed designed to provide context for the homepage and the singular view, respectively:

use Brain\Context;

class HomepageContext implements Context\ProviderFactory
{
    public function create(\WP_Query $query, LoggerInterface $logger): ?Provider
    {
        return Context\Provider\ArrayMerge::new(fn() => $query->is_front_page())
            ->addProvider(new MyHeroProvider())
            ->addProvider(new Context\Provider\Posts(['posts_per_page' => 5], 'latest_posts'));
    }
}

class SingularContext implements Context\ProviderFactory
{
    public function create(\WP_Query $query, LoggerInterface $logger): ?Provider
    {
        return Context\Provider\ArrayMerge::new(fn() => $query->is_singular())
            ->addProvider(new Context\Provider\ByCallback(fn() => ['post' => $query->post]))
            ->addProvider(new Context\Provider\Comments(['post_id' => $query->post->ID]));
    }
}

Now we can make use of the Context class to generate the context for our templates:

namespace MyTheme;

use Brain\Context;

add_action('template_redirect', function () {
    
    $context = Context\Context::new()
        ->withProviderFactory(new HomepageContext())
        ->withProviderFactory(new SingularContext())
        ->provide();
        
    // pass context to templates here ...
});

Context class emit the action `"brain.context.providers" that can be used to add providers from different places:

namespace MyTheme;

use Brain\Context;

add_action('brain.context.providers', function (Context\Context $context) {
    $context
        ->withProviderFactory(new HomepageContext())
        ->withProviderFactory(new SingularContext());
});

add_action('template_redirect', function () {
    $context = Context\Context::new()->provide();
    // pass context to templates here ...
});

Examples using Hierarchy

Here's an example of using context in combination with Brain Hierarchy to render mustache templates passing them context.

namespace My\Theme;

use Brain\Hierarchy\{Finder, Loader, QueryTemplate};
use Brain\Context;

class MustacheTemplateLoader implements Loader\Loader
{
   private $engine;

   public function __construct(\Mustache_Engine $engine)
   {
      $this->engine = $engine;
   }

   public function load(string $templatePath): string
   {
        // It will be possible to hook 'brain.context.providers' to add context providers
        $data = Context\Context::new()
            ->convertEntitiesToPlainObjects()
            ->forwardGlobals()
            ->provide();

        return $this->engine->render(file_get_contents($templatePath), $data);
   }
}

add_action('template_redirect', function() {
    if (!QueryTemplate::mainQueryTemplateAllowed()) {
        return;
    }

    $queryTemplate = new QueryTemplate(
        new Finder\BySubfolder('templates', 'mustache'),
        new MustacheTemplateLoader(new \Mustache_Engine())
    );

    $content = $queryTemplate->loadTemplate(null, true, $found);
    $found and die($content);
});

Above is all the necessary code to render *.mustache templates from a /templates subfolder in current theme (or parent theme, if any), according to WP template hierarchy, passing to templates context data that can be extended via ad-hoc "view context" classes which will implement Context\ProviderFactory interface.

Providers

Composite providers

The "Quick start" section above uses Context\Provider\ArrayMerge class to "merge" several providers.

Besides that class, there's also a Context\Provider\ArrayMergeRecursive "composite" provider.

Atomic providers

The "composite" providers merge multiple "atomic" providers that can be either custom (anything implementing Context\Provider) or one of the shipped provider classes:

• ByArray - which provides a given array as-is
• ByCallback - which provides an array returned by a given callback
• Comments - which provides an array of comments using given comment query arguments
• Posts - which provides an array of posts using given post query arguments
• Subquery - which provides a WP_Query instance using given query arguments
• Terms - which provides an array of comments using given taxonomy terms query arguments
• Users - which provides an array of comments using given user query arguments

Custom providers

The Context\Provider interface has a single method:

public function provide(\WP_Query $query, LoggerInterface $logger): ?array;

Which can be implemented to build custom providers. In the case the provider should not be used based on conditions, it can return null.

The given PSR-3 logger interface can be used to log errors and distinguish a provider that returns null due to errors form another that returns null because, for example, not targeting the current query.

Logger

All providers support a PSR-3 logger. Context class implements PSR-3 LoggerAwareInterface, so it is possible to call setLogger when instantiating it.

There's also a "brain.context.logger" action that passes a callback that can be used to set the logger:

add_action('brain.context.logger', function (callable $setter) {
    $setter(new MyPsr3Logger());
});

Requirements

Context requires PHP 7.1+ and Composer to be installed.

Installation

Best served by Composer, available on Packagist with name brain/context.

License

Context is released under MIT.