class State

class State extends CacheCollector implements StateInterface {
  
  /**
   * Information about all deprecated state, keyed by legacy state key.
   *
   * Each entry should be an array that defines the following keys:
   *   - 'replacement': The new name for the state.
   *   - 'message': The deprecation message to use for trigger_error().
   *
   * @var array
   */
  private static array $deprecatedState = [];
  
  /**
   * The key value store to use.
   *
   * @var \Drupal\Core\KeyValueStore\KeyValueStoreInterface
   */
  protected $keyValueStore;
  
  /**
   * Tracks keys that have been modified during the request lifecycle.
   *
   * An associative array keyed by the state key name, where each value
   * is an array with the following keys:
   *   - value: The last value set during the request.
   *   - original: The initial value at the start of the request.
   */
  protected array $keysSetDuringRequest = [];
  
  /**
   * Constructs a State object.
   *
   * @param \Drupal\Core\KeyValueStore\KeyValueFactoryInterface $key_value_factory
   *   The key value store to use.
   * @param \Drupal\Core\Cache\CacheBackendInterface $cache
   *   The cache backend.
   * @param \Drupal\Core\Lock\LockBackendInterface $lock
   *   The lock backend.
   */
  public function __construct(KeyValueFactoryInterface $key_value_factory, CacheBackendInterface $cache, LockBackendInterface $lock) {
    parent::__construct('state', $cache, $lock);
    $this->keyValueStore = $key_value_factory->get('state');
  }
  
  /**
   * {@inheritdoc}
   */
  public function get($key, $default = NULL) {
    // If the caller is asking for the value of a deprecated state, trigger a
    // deprecation message about it.
    if (isset(self::$deprecatedState[$key])) {
      // phpcs:ignore Drupal.Semantics.FunctionTriggerError
      @trigger_error(self::$deprecatedState[$key]['message'], E_USER_DEPRECATED);
      $key = self::$deprecatedState[$key]['replacement'];
    }
    return parent::get($key) ?? $default;
  }
  
  /**
   * {@inheritdoc}
   */
  protected function resolveCacheMiss($key) {
    $value = $this->keyValueStore
      ->get($key);
    $this->storage[$key] = $value;
    $this->persist($key);
    return $value;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getMultiple(array $keys) {
    $values = [];
    foreach ($keys as $key) {
      $values[$key] = $this->get($key);
    }
    return $values;
  }
  
  /**
   * {@inheritdoc}
   */
  public function set($key, $value) {
    if (isset(self::$deprecatedState[$key])) {
      // phpcs:ignore Drupal.Semantics.FunctionTriggerError
      @trigger_error(self::$deprecatedState[$key]['message'], E_USER_DEPRECATED);
      $key = self::$deprecatedState[$key]['replacement'];
    }
    $this->registerKeySetDuringRequest($key, $value, parent::get($key));
    $this->keyValueStore
      ->set($key, $value);
    // If another request had a cache miss before this request, and also hasn't
    // written to cache yet, then it may already have read this value from the
    // database and could write that value to the cache to the end of the
    // request. To avoid this race condition, write to the cache immediately
    // after calling parent::set(). This allows the race condition detection in
    // CacheCollector::set() to work.
    parent::set($key, $value);
    $this->persist($key);
    static::updateCache();
  }
  
  /**
   * {@inheritdoc}
   */
  public function setMultiple(array $data) {
    $this->keyValueStore
      ->setMultiple($data);
    foreach ($data as $key => $value) {
      $this->registerKeySetDuringRequest($key, $value, parent::get($key));
      parent::set($key, $value);
      $this->persist($key);
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function delete($key) {
    $this->keyValueStore
      ->delete($key);
    parent::delete($key);
  }
  
  /**
   * {@inheritdoc}
   */
  public function deleteMultiple(array $keys) {
    $this->keyValueStore
      ->deleteMultiple($keys);
    foreach ($keys as $key) {
      parent::delete($key);
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function resetCache() {
    $this->clear();
  }
  
  /**
   * {@inheritdoc}
   */
  public function getValuesSetDuringRequest(string $key) : ?array {
    return $this->keysSetDuringRequest[$key] ?? NULL;
  }
  
  /**
   * Registers a key that was set during the request.
   *
   * @param string $key
   *   The key that was set.
   * @param mixed $value
   *   The value that was set.
   * @param mixed $previousValue
   *   The previous value that was stored.
   */
  protected function registerKeySetDuringRequest(string $key, mixed $value, mixed $previousValue) : void {
    $this->keysSetDuringRequest[$key]['value'] = $value;
    if (!array_key_exists('original', $this->keysSetDuringRequest[$key])) {
      $this->keysSetDuringRequest[$key]['original'] = $previousValue;
    }
  }

}