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<?php |
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namespace Http\Discovery; |
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use Http\Discovery\Exception\ClassinstantiationFailedException; |
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use Http\Discovery\Exception\DiscoveryFailedException; |
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use Http\Discovery\Exception\StrategyUnavailableException; |
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/** |
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* Registry that based find results on class existence. |
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* |
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* @author David de Boer <[email protected]> |
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* @author Márk Sági-Kazár <[email protected]> |
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* @author Tobias Nyholm <[email protected]> |
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*/ |
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abstract class ClassDiscovery |
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{ |
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/** |
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* A list of strategies to find classes. |
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* |
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* @var array |
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*/ |
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private static $strategies = [ |
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Strategy\PuliBetaStrategy::class, |
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Strategy\CommonClassesStrategy::class, |
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]; |
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/** |
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* Discovery cache to make the second time we use discovery faster. |
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* |
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* @var array |
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*/ |
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private static $cache = []; |
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/** |
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* Finds a class. |
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* |
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* @param string $type |
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* |
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* @return string|\Closure |
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* |
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* @throws DiscoveryFailedException |
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*/ |
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protected static function findOneByType($type) |
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{ |
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// Look in the cache |
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if (null !== ($class = self::getFromCache($type))) { |
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return $class; |
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} |
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$exceptions = []; |
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foreach (self::$strategies as $strategy) { |
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try { |
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$candidates = call_user_func($strategy.'::getCandidates', $type); |
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} catch (StrategyUnavailableException $e) { |
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$exceptions[] = $e; |
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continue; |
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} |
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foreach ($candidates as $candidate) { |
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if (isset($candidate['condition'])) { |
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if (!self::evaluateCondition($candidate['condition'])) { |
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continue; |
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} |
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} |
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// save the result for later use |
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self::storeInCache($type, $candidate); |
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return $candidate['class']; |
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} |
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} |
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throw new DiscoveryFailedException('Could not find resource using any discovery strategy', $exceptions); |
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} |
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/** |
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* Get a value from cache. |
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* |
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* @param string $type |
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* |
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* @return string|null |
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*/ |
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private static function getFromCache($type) |
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{ |
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if (!isset(self::$cache[$type])) { |
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return; |
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} |
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$candidate = self::$cache[$type]; |
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if (isset($candidate['condition'])) { |
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if (!self::evaluateCondition($candidate['condition'])) { |
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return; |
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} |
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} |
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return $candidate['class']; |
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} |
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/** |
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* Store a value in cache. |
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* |
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* @param string $type |
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* @param string $class |
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*/ |
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private static function storeInCache($type, $class) |
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{ |
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self::$cache[$type] = $class; |
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} |
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/** |
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* Set new strategies and clear the cache. |
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* |
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* @param array $strategies string array of fully qualified class name to a DiscoveryStrategy |
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*/ |
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public static function setStrategies(array $strategies) |
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{ |
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self::$strategies = $strategies; |
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self::clearCache(); |
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} |
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/** |
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* Append a strategy at the end of the strategy queue. |
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* |
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* @param string $strategy Fully qualified class name to a DiscoveryStrategy |
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*/ |
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public static function appendStrategy($strategy) |
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{ |
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self::$strategies[] = $strategy; |
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self::clearCache(); |
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} |
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/** |
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* Prepend a strategy at the beginning of the strategy queue. |
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* |
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* @param string $strategy Fully qualified class name to a DiscoveryStrategy |
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*/ |
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public static function prependStrategy($strategy) |
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{ |
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array_unshift(self::$strategies, $strategy); |
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self::clearCache(); |
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} |
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/** |
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* Clear the cache. |
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*/ |
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public static function clearCache() |
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{ |
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self::$cache = []; |
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} |
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/** |
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* Evaulates conditions to boolean. |
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* |
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* @param mixed $condition |
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* |
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* @return bool |
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*/ |
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protected static function evaluateCondition($condition) |
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{ |
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if (is_string($condition)) { |
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// Should be extended for functions, extensions??? |
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return class_exists($condition); |
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} elseif (is_callable($condition)) { |
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return $condition(); |
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} elseif (is_bool($condition)) { |
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return $condition; |
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} elseif (is_array($condition)) { |
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$evaluatedCondition = true; |
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// Immediately stop execution if the condition is false |
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for ($i = 0; $i < count($condition) && false !== $evaluatedCondition; ++$i) { |
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$evaluatedCondition &= static::evaluateCondition($condition[$i]); |
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} |
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return $evaluatedCondition; |
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} |
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return false; |
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} |
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/** |
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* Get an instance of the $class. |
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* |
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* @param string|\Closure $class A FQN of a class or a closure that instantiate the class. |
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* |
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* @return object |
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*/ |
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protected static function instantiateClass($class) |
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{ |
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try { |
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if (is_string($class)) { |
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return new $class(); |
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} |
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if (is_callable($class)) { |
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return $class(); |
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} |
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} catch (\Exception $e) { |
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throw new ClassinstantiationFailedException('Unexcepced exception when instantiating class.', 0, $e); |
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} |
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throw new ClassinstantiationFailedException('Could not instantiate class becuase parameter is neitehr a callable or a string'); |
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} |
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} |
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