postoffice-1.0.x-dev/src/DependencyInjection/Compiler/StackedMailerPass.php

<?php

namespace Drupal\postoffice\DependencyInjection\Compiler;

use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Reference;

/**
 * Provides a compiler pass for stacked mailer.
 *
 * Build a mailer by collecting all services tagged
 * 'postoffice.mailer_middleware' and assembles them into a stack. The
 * middleware with the highest priority ends up as the outermost while the
 * lowest priority middleware wraps the actual mailer defined by the
 * postoffice.mailer.basic service.
 */
class StackedMailerPass implements CompilerPassInterface {

  /**
   * {@inheritdoc}
   */
  public function process(ContainerBuilder $container): void {

    if (!$container->hasDefinition('postoffice.mailer')) {
      return;
    }

    $stacked_mailer = $container->getDefinition('postoffice.mailer');

    $middlewares = [];
    $priorities = [];

    foreach ($container->findTaggedServiceIds('postoffice.mailer_middleware') as $id => $attributes) {
      $priorities[$id] = $attributes[0]['priority'] ?? 0;
      $middlewares[$id] = $container->getDefinition($id);
    }

    array_multisort($priorities, SORT_ASC, $middlewares);

    $decorated_id = 'postoffice.mailer.basic';
    $middlewares_param = [new Reference($decorated_id)];

    foreach ($middlewares as $id => $decorator) {
      // Prepend a reference to the middlewares container parameter.
      array_unshift($middlewares_param, new Reference($id));

      // Prepend the inner body renderer as first constructor argument.
      $arguments = $decorator->getArguments();
      array_unshift($arguments, new Reference($decorated_id));
      $decorator->setArguments($arguments);

      $decorated_id = $id;
    }

    $arguments = [$middlewares_param[0]];
    $stacked_mailer->setArguments($arguments);
  }

}