lithium\core\Adaptable

class

The Adaptable static class is the base class from which all adapter implementations extend.

Adaptable provides the logic necessary for generic configuration of named adapter configurations (such as the ones used in Cache) as well as a unified method of locating and obtaining an instance to a specified adapter.

All immediate subclasses to Adaptable must define the protected attributes $_configurations and $_adapters. The former is where all local adapter named configurations will be stored (as an array of named configuration settings), and the latter must contain the Libraries::locate()-compatible path string (or array of strings) specifying how adapter classes should be located.

This static class should never be called explicitly.

Subclasses

Source

class Adaptable extends \lithium\core\StaticObject {

	/**
	 * Must always be re-defined in sub-classes. Can provide initial
	 * configurations, i.e. `'development'` or `'default'` along with
	 * default options for each.
	 *
	 * Example:
	 * ```
	 * array(
	 *  'production' => array(),
	 *  'development' => array(),
	 *  'test' => array()
	 * )
	 * ```
	 *
	 * @var array Array of configurations, indexed by name.
	 */
	protected static $_configurations = array();

	/**
	 * Must only be re-defined in sub-classes if the class is using strategies.
	 * Holds the `Libraries::locate()` compatible path string where the strategy
	 * in question may be found i.e. `'strategy.storage.cache'`.
	 *
	 * @var string Path string.
	 */
	protected static $_strategies = null;

	/**
	 * Must always be re-defined in sub-classes. Holds the
	 * `Libraries::locate()` compatible path string where the adapter in
	 * question may be found i.e. `'adapter.storage.cache'`.
	 *
	 * @var string Path string.
	 */
	protected static $_adapters = null;

	/**
	 * Sets configurations for a particular adaptable implementation, or returns the current
	 * configuration settings.
	 *
	 * @param array|string $config An array of configurations, indexed by name to set
	 *        configurations in one go or a name for which to return the configuration.
	 * @return array|void Configuration or void if setting configurations.
	 */
	public static function config($config = null) {
		if ($config && is_array($config)) {
			static::$_configurations = $config;
			return;
		}
		if ($config) {
			return static::_config($config);
		}
		$result = array();
		static::$_configurations = array_filter(static::$_configurations);

		foreach (array_keys(static::$_configurations) as $key) {
			$result[$key] = static::_config($key);
		}
		return $result;
	}

	/**
	 * Clears all configurations.
	 *
	 * @return void
	 */
	public static function reset() {
		static::$_configurations = array();
	}

	/**
	 * Returns adapter class name for given `$name` configuration, using
	 * the `$_adapter` path defined in Adaptable subclasses.
	 *
	 * @param string|null $name Class name of adapter to load.
	 * @return object Adapter object.
	 */
	public static function adapter($name = null) {
		$config = static::_config($name);

		if ($config === null) {
			throw new ConfigException("Configuration `{$name}` has not been defined.");
		}

		if (isset($config['object'])) {
			return $config['object'];
		}
		$class = static::_class($config, static::$_adapters);
		$settings = static::$_configurations[$name];
		$settings[0]['object'] = static::_initAdapter($class, $config);
		static::$_configurations[$name] = $settings;
		return static::$_configurations[$name][0]['object'];
	}

	/**
	 * Obtain an `SplDoublyLinkedList` of the strategies for the given `$name` configuration, using
	 * the `$_strategies` path defined in `Adaptable` subclasses.
	 *
	 * @param string $name Class name of adapter to load.
	 * @return object `SplDoublyLinkedList` of strategies, or `null` if none are defined.
	 */
	public static function strategies($name) {
		$config = static::_config($name);

		if ($config === null) {
			throw new ConfigException("Configuration `{$name}` has not been defined.");
		}
		if (!isset($config['strategies'])) {
			return null;
		}
		$stack = new SplDoublyLinkedList();

		foreach ($config['strategies'] as $key => $strategy) {
			if (!is_array($strategy)) {
				$name = $strategy;
				$class = static::_strategy($name, static::$_strategies);
				$stack->push(new $class());
				continue;
			}
			$class = static::_strategy($key, static::$_strategies);
			$index = (isset($config['strategies'][$key])) ? $key : $class;
			$stack->push(new $class($config['strategies'][$index]));
		}
		return $stack;
	}

	/**
	 * Applies strategies configured in `$name` for `$method` on `$data`.
	 *
	 * @param string $method The strategy method to be applied.
	 * @param string $name The named configuration
	 * @param mixed $data The data to which the strategies will be applied.
	 * @param array $options If `mode` is set to 'LIFO', the strategies are applied in reverse.
	 *        order of their definition.
	 * @return mixed Result of application of strategies to data. If no strategies
	 *         have been configured, this method will simply return the original data.
	 */
	public static function applyStrategies($method, $name, $data, array $options = array()) {
		$options += array('mode' => null);

		if (!$strategies = static::strategies($name)) {
			return $data;
		}
		if (!count($strategies)) {
			return $data;
		}

		if (isset($options['mode']) && ($options['mode'] === 'LIFO')) {
			$strategies->setIteratorMode(SplDoublyLinkedList::IT_MODE_LIFO);
			unset($options['mode']);
		}

		foreach ($strategies as $strategy) {
			if (method_exists($strategy, $method)) {
				$data = $strategy->{$method}($data, $options);
			}
		}
		return $data;
	}

	/**
	 * Determines if the adapter specified in the named configuration is enabled.
	 *
	 * `Enabled` can mean various things, e.g. having a PECL memcached extension compiled
	 * & loaded, as well as having the memcache server up & available.
	 *
	 * @param string $name The named configuration whose adapter will be checked.
	 * @return boolean  True if adapter is enabled, false if not. This method will
	 *         return null if no configuration under the given $name exists.
	 */
	public static function enabled($name) {
		$class = static::_class(static::_config($name), static::$_adapters);
		return $class::enabled();
	}

	/**
	 * Provides an extension point for modifying how adapters are instantiated.
	 *
	 * @see lithium\core\Object::__construct()
	 * @param string $class The fully-namespaced class name of the adapter to instantiate.
	 * @param array $config The configuration array to be passed to the adapter instance. See the
	 *              `$config` parameter of `Object::__construct()`.
	 * @return object The adapter's class.
	 * @filter
	 */
	protected static function _initAdapter($class, array $config) {
		return static::_filter(__FUNCTION__, compact('class', 'config'), function($self, $params) {
			return new $params['class']($params['config']);
		});
	}

	/**
	 * Looks up an adapter by class by name.
	 *
	 * @see lithium\core\libraries::locate()
	 * @param array $config Configuration array of class to be found.
	 * @param array $paths Optional array of search paths that will be checked.
	 * @return string Returns a fully-namespaced class reference to the adapter class.
	 */
	protected static function _class($config, $paths = array()) {
		if (!$name = $config['adapter']) {
			$self = get_called_class();
			throw new ConfigException("No adapter set for configuration in class `{$self}`.");
		}
		if (!$class = static::_locate($paths, $name)) {
			$self = get_called_class();
			throw new ConfigException("Could not find adapter `{$name}` in class `{$self}`.");
		}
		return $class;
	}

	/**
	 * Looks up a strategy by class by name.
	 *
	 * @see lithium\core\libraries::locate()
	 * @param string $name The strategy to locate.
	 * @param array $paths Optional array of search paths that will be checked.
	 * @return string Returns a fully-namespaced class reference to the adapter class.
	 */
	protected static function _strategy($name, $paths = array()) {
		if (!$name) {
			$self = get_called_class();
			throw new ConfigException("No strategy set for configuration in class `{$self}`.");
		}
		if (!$class = static::_locate($paths, $name)) {
			$self = get_called_class();
			throw new ConfigException("Could not find strategy `{$name}` in class `{$self}`.");
		}
		return $class;
	}

	/**
	 * Perform library location for an array of paths or a single string-based path.
	 *
	 * @param string|array $paths Paths that Libraries::locate() will utilize.
	 * @param string $name The name of the class to be located.
	 * @return string Fully-namespaced path to the class, or null if not found.
	 */
	protected static function _locate($paths, $name) {
		foreach ((array) $paths as $path) {
			if ($class = Libraries::locate($path, $name)) {
				return $class;
			}
		}
		return null;
	}

	/**
	 * Gets an array of settings for the given named configuration in the current
	 * environment.
	 *
	 * The default types of settings for all adapters will contain keys for:
	 * `adapter` - The class name of the adapter
	 * `filters` - An array of filters to be applied to the adapter methods
	 *
	 * @see lithium\core\Environment
	 * @param string $name Named configuration.
	 * @return array|null Settings for the named configuration.
	 */
	protected static function _config($name) {
		if (!isset(static::$_configurations[$name])) {
			return null;
		}
		$settings = static::$_configurations[$name];

		if (isset($settings[0])) {
			return $settings[0];
		}
		$env = Environment::get();
		$config = isset($settings[$env]) ? $settings[$env] : $settings;

		if (isset($settings[$env]) && isset($settings[true])) {
			$config += $settings[true];
		}
		static::$_configurations[$name] += array(static::_initConfig($name, $config));
		return static::$_configurations[$name][0];
	}

	/**
	 * A stub method called by `_config()` which allows `Adaptable` subclasses to automatically
	 * assign or auto-generate additional configuration data, once a configuration is first
	 * accessed. This allows configuration data to be lazy-loaded from adapters or other data
	 * sources.
	 *
	 * @param string $name The name of the configuration which is being accessed. This is the key
	 *               name containing the specific set of configuration passed into `config()`.
	 * @param array $config Contains the configuration assigned to `$name`. If this configuration is
	 *              segregated by environment, then this will contain the configuration for the
	 *              current environment.
	 * @return array Returns the final array of settings for the given named configuration.
	 */
	protected static function _initConfig($name, $config) {
		$defaults = array('adapter' => null, 'filters' => array());
		return (array) $config + $defaults;
	}
}