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system/Cache/CacheFactory.php

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+<?php
+
+/**
+ * This file is part of the CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace CodeIgniter\Cache;
+
+use CodeIgniter\Cache\Exceptions\CacheException;
+use CodeIgniter\Exceptions\CriticalError;
+use Config\Cache;
+
+/**
+ * Class Cache
+ *
+ * A factory for loading the desired
+ */
+class CacheFactory
+{
+	/**
+	 * Attempts to create the desired cache handler, based upon the
+	 *
+	 * @param Cache       $config
+	 * @param string|null $handler
+	 * @param string|null $backup
+	 *
+	 * @return CacheInterface
+	 */
+	public static function getHandler(Cache $config, string $handler = null, string $backup = null)
+	{
+		if (! isset($config->validHandlers) || ! is_array($config->validHandlers))
+		{
+			throw CacheException::forInvalidHandlers();
+		}
+
+		if (! isset($config->handler) || ! isset($config->backupHandler))
+		{
+			throw CacheException::forNoBackup();
+		}
+
+		$handler = ! empty($handler) ? $handler : $config->handler;
+		$backup  = ! empty($backup) ? $backup : $config->backupHandler;
+
+		if (! array_key_exists($handler, $config->validHandlers) || ! array_key_exists($backup, $config->validHandlers))
+		{
+			throw CacheException::forHandlerNotFound();
+		}
+
+		// Get an instance of our handler.
+		$adapter = new $config->validHandlers[$handler]($config);
+
+		if (! $adapter->isSupported())
+		{
+			$adapter = new $config->validHandlers[$backup]($config);
+
+			if (! $adapter->isSupported())
+			{
+				// Log stuff here, don't throw exception. No need to raise a fuss.
+				// Fall back to the dummy adapter.
+				$adapter = new $config->validHandlers['dummy']();
+			}
+		}
+
+		// If $adapter->initialization throws a CriticalError exception, we will attempt to
+		// use the $backup handler, if that also fails, we resort to the dummy handler.
+		try
+		{
+			$adapter->initialize();
+		}
+		catch (CriticalError $e)
+		{
+			// log the fact that an exception occurred as well what handler we are resorting to
+			log_message('critical', $e->getMessage() . ' Resorting to using ' . $backup . ' handler.');
+
+			// get the next best cache handler (or dummy if the $backup also fails)
+			$adapter = self::getHandler($config, $backup, 'dummy');
+		}
+
+		return $adapter;
+	}
+
+	//--------------------------------------------------------------------
+}