abstract class CacheProvider

abstract class CacheProvider implements Cache {
  const DOCTRINE_NAMESPACE_CACHEKEY = 'DoctrineNamespaceCacheKey[%s]';

  /**
   * @var string The namespace to prefix all cache ids with
   */
  private $namespace = '';

  /**
   * @var string The namespace version
   */
  private $namespaceVersion;

  /**
   * Set the namespace to prefix all cache ids with.
   *
   * @param string $namespace
   * @return void
   */
  public function setNamespace($namespace) {
    $this->namespace = (string) $namespace;
  }

  /**
   * Retrieve the namespace that prefixes all cache ids.
   *
   * @return string
   */
  public function getNamespace() {
    return $this->namespace;
  }

  /**
   * {@inheritdoc}
   */
  public function fetch($id) {
    return $this
      ->doFetch($this
      ->getNamespacedId($id));
  }

  /**
   * {@inheritdoc}
   */
  public function contains($id) {
    return $this
      ->doContains($this
      ->getNamespacedId($id));
  }

  /**
   * {@inheritdoc}
   */
  public function save($id, $data, $lifeTime = 0) {
    return $this
      ->doSave($this
      ->getNamespacedId($id), $data, $lifeTime);
  }

  /**
   * {@inheritdoc}
   */
  public function delete($id) {
    return $this
      ->doDelete($this
      ->getNamespacedId($id));
  }

  /**
   * {@inheritdoc}
   */
  public function getStats() {
    return $this
      ->doGetStats();
  }

  /**
   * Deletes all cache entries.
   *
   * @return boolean TRUE if the cache entries were successfully flushed, FALSE otherwise.
   */
  public function flushAll() {
    return $this
      ->doFlush();
  }

  /**
   * Delete all cache entries.
   *
   * @return boolean TRUE if the cache entries were successfully deleted, FALSE otherwise.
   */
  public function deleteAll() {
    $namespaceCacheKey = $this
      ->getNamespaceCacheKey();
    $namespaceVersion = $this
      ->getNamespaceVersion() + 1;
    $this->namespaceVersion = $namespaceVersion;
    return $this
      ->doSave($namespaceCacheKey, $namespaceVersion);
  }

  /**
   * Prefix the passed id with the configured namespace value
   *
   * @param string $id  The id to namespace
   * @return string $id The namespaced id
   */
  private function getNamespacedId($id) {
    $namespaceVersion = $this
      ->getNamespaceVersion();
    return sprintf('%s[%s][%s]', $this->namespace, $id, $namespaceVersion);
  }

  /**
   * Namespace cache key
   *
   * @return string $namespaceCacheKey
   */
  private function getNamespaceCacheKey() {
    return sprintf(self::DOCTRINE_NAMESPACE_CACHEKEY, $this->namespace);
  }

  /**
   * Namespace version
   *
   * @return string $namespaceVersion
   */
  private function getNamespaceVersion() {
    if (null !== $this->namespaceVersion) {
      return $this->namespaceVersion;
    }
    $namespaceCacheKey = $this
      ->getNamespaceCacheKey();
    $namespaceVersion = $this
      ->doFetch($namespaceCacheKey);
    if (false === $namespaceVersion) {
      $namespaceVersion = 1;
      $this
        ->doSave($namespaceCacheKey, $namespaceVersion);
    }
    $this->namespaceVersion = $namespaceVersion;
    return $this->namespaceVersion;
  }

  /**
   * Fetches an entry from the cache.
   *
   * @param string $id cache id The id of the cache entry to fetch.
   * @return string The cached data or FALSE, if no cache entry exists for the given id.
   */
  protected abstract function doFetch($id);

  /**
   * Test if an entry exists in the cache.
   *
   * @param string $id cache id The cache id of the entry to check for.
   * @return boolean TRUE if a cache entry exists for the given cache id, FALSE otherwise.
   */
  protected abstract function doContains($id);

  /**
   * Puts data into the cache.
   *
   * @param string $id The cache id.
   * @param string $data The cache entry/data.
   * @param bool|int $lifeTime The lifetime. If != false, sets a specific lifetime for this
   *                           cache entry (null => infinite lifeTime).
   *
   * @return boolean TRUE if the entry was successfully stored in the cache, FALSE otherwise.
   */
  protected abstract function doSave($id, $data, $lifeTime = false);

  /**
   * Deletes a cache entry.
   *
   * @param string $id cache id
   * @return boolean TRUE if the cache entry was successfully deleted, FALSE otherwise.
   */
  protected abstract function doDelete($id);

  /**
   * Deletes all cache entries.
   *
   * @return boolean TRUE if the cache entry was successfully deleted, FALSE otherwise.
   */
  protected abstract function doFlush();

  /**
   * Retrieves cached information from data store
   *
   * @since   2.2
   * @return  array An associative array with server's statistics if available, NULL otherwise.
   */
  protected abstract function doGetStats();

}