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<?php
namespace Http\Discovery;
use Http\Discovery\Exception\ClassInstantiationFailedException;
use Http\Discovery\Exception\DiscoveryFailedException;
use Http\Discovery\Exception\StrategyUnavailableException;
/**
* Registry that based find results on class existence.
*
* @author David de Boer <david@ddeboer.nl>
* @author Márk Sági-Kazár <mark.sagikazar@gmail.com>
* @author Tobias Nyholm <tobias.nyholm@gmail.com>
*/
abstract class ClassDiscovery
{
/**
* A list of strategies to find classes.
*
* @var array
*/
private static $strategies = [
Strategy\PuliBetaStrategy::class,
Strategy\CommonClassesStrategy::class,
];
/**
* Discovery cache to make the second time we use discovery faster.
*
* @var array
*/
private static $cache = [];
/**
* Finds a class.
*
* @param string $type
*
* @return string|\Closure
*
* @throws DiscoveryFailedException
*/
protected static function findOneByType($type)
{
// Look in the cache
if (null !== ($class = self::getFromCache($type))) {
return $class;
}
$exceptions = [];
foreach (self::$strategies as $strategy) {
try {
$candidates = call_user_func($strategy.'::getCandidates', $type);
} catch (StrategyUnavailableException $e) {
$exceptions[] = $e;
continue;
}
foreach ($candidates as $candidate) {
if (isset($candidate['condition'])) {
if (!self::evaluateCondition($candidate['condition'])) {
continue;
}
}
// save the result for later use
self::storeInCache($type, $candidate);
return $candidate['class'];
}
}
throw DiscoveryFailedException::create($exceptions);
}
/**
* Get a value from cache.
*
* @param string $type
*
* @return string|null
*/
private static function getFromCache($type)
{
if (!isset(self::$cache[$type])) {
return;
}
$candidate = self::$cache[$type];
if (isset($candidate['condition'])) {
if (!self::evaluateCondition($candidate['condition'])) {
return;
}
}
return $candidate['class'];
}
/**
* Store a value in cache.
*
* @param string $type
* @param string $class
*/
private static function storeInCache($type, $class)
{
self::$cache[$type] = $class;
}
/**
* Set new strategies and clear the cache.
*
* @param array $strategies string array of fully qualified class name to a DiscoveryStrategy
*/
public static function setStrategies(array $strategies)
{
self::$strategies = $strategies;
self::clearCache();
}
/**
* Append a strategy at the end of the strategy queue.
*
* @param string $strategy Fully qualified class name to a DiscoveryStrategy
*/
public static function appendStrategy($strategy)
{
self::$strategies[] = $strategy;
self::clearCache();
}
/**
* Prepend a strategy at the beginning of the strategy queue.
*
* @param string $strategy Fully qualified class name to a DiscoveryStrategy
*/
public static function prependStrategy($strategy)
{
array_unshift(self::$strategies, $strategy);
self::clearCache();
}
/**
* Clear the cache.
*/
public static function clearCache()
{
self::$cache = [];
}
/**
* Evaluates conditions to boolean.
*
* @param mixed $condition
*
* @return bool
*/
protected static function evaluateCondition($condition)
{
if (is_string($condition)) {
// Should be extended for functions, extensions???
return class_exists($condition);
} elseif (is_callable($condition)) {
return $condition();
} elseif (is_bool($condition)) {
return $condition;
} elseif (is_array($condition)) {
$evaluatedCondition = true;
// Immediately stop execution if the condition is false
for ($i = 0; $i < count($condition) && false !== $evaluatedCondition; ++$i) {
$evaluatedCondition &= static::evaluateCondition($condition[$i]);
}
return $evaluatedCondition;
}
return false;
}
/**
* Get an instance of the $class.
*
* @param string|\Closure $class A FQCN of a class or a closure that instantiate the class.
*
* @return object
*
* @throws ClassInstantiationFailedException
*/
protected static function instantiateClass($class)
{
try {
if (is_string($class)) {
return new $class();
}
if (is_callable($class)) {
return $class();
}
} catch (\Exception $e) {
throw new ClassInstantiationFailedException('Unexpected exception when instantiating class.', 0, $e);
}
throw new ClassInstantiationFailedException('Could not instantiate class because parameter is neither a callable nor a string');
}
}
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