<?php

namespace Drupal\Core\Plugin\Discovery;

use Drupal\Component\Plugin\Discovery\DiscoveryInterface;
use Drupal\Component\Plugin\Discovery\DiscoveryTrait;
use Drupal\Core\Extension\ModuleHandlerInterface;

/**
 * Provides a hook-based plugin discovery class.
 */
class HookDiscovery implements DiscoveryInterface {

  use DiscoveryTrait;

  /**
   * The name of the hook that will be implemented by this discovery instance.
   *
   * @var string
   */
  protected $hook;

  /**
   * The module handler used to find and execute the plugin hook.
   *
   * @var \Drupal\Core\Extension\ModuleHandlerInterface
   */
  protected $moduleHandler;

  /**
   * Constructs a Drupal\Core\Plugin\Discovery\HookDiscovery object.
   *
   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
   *   The module handler.
   * @param string $hook
   *   The Drupal hook that a module can implement in order to interface to
   *   this discovery class.
   */
  public function __construct(ModuleHandlerInterface $module_handler, $hook) {
    $this->moduleHandler = $module_handler;
    $this->hook = $hook;
  }

  /**
   * {@inheritdoc}
   */
  public function getDefinitions() {
    $definitions = [];
    foreach ($this->moduleHandler->getImplementations($this->hook) as $module) {
      $result = $this->moduleHandler->invoke($module, $this->hook);
      foreach ($result as $plugin_id => $definition) {
        $definition['provider'] = $module;
        $definitions[$plugin_id] = $definition;
      }
    }
    return $definitions;
  }

}