<?php

/**
 * @file
 * Definition of Drupal\Core\Config\Context\ExtendedContext.
 */

namespace Drupal\Core\Config\Context;

use Drupal\Core\Config\ContextInterface;

/**
 * Defines a configuration context that extends another context.
 *
 * @see Drupal\user\UserConfigContext
 */
class ExtendedContext extends ConfigContext {

  /**
   * Parent context.
   *
   * @var Drupal\Core\Config\ContextInterface.
   */
  protected $parentContext;

  /**
   * Overrides Drupal\Core\Config\Context\ConfigContext::__construct().
   *
   * @param Drupal\Core\Config\ContextInterface $parent_context
   *   Parent context that will be used as fallback when retrieving values from
   *   this context.
   */
  public function __construct(ContextInterface $parent_context) {
    $this->parentContext = $parent_context;
    parent::__construct($parent_context->getStorage(), $parent_context->getEventDispatcher());
  }

  /**
   * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::get().
   */
  public function get($key) {
    if (array_key_exists($key, $this->data)) {
      return $this->data[$key];
    }
    else {
      return $this->parentContext->getData();
    }
  }

  /**
   * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::getMultiple().
   */
  public function getMultiple(array $keys) {
    return array_intersect_key($this->data, array_flip($keys)) + $this->parentContext->getMultiple($keys);
  }

  /**
   * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::getAll().
   */
  public function getAll() {
    return $this->data + $this->parentContext->getAll();
  }

}