<?php
/**
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @since         1.2.0
 * @license       http://www.opensource.org/licenses/mit-license.php MIT License
 */
namespace Cake\Cache;

use Cake\Cache\Engine\NullEngine;
use Cake\Core\Error\Exception;
use Cake\Core\StaticConfigTrait;

/**
 * Cache provides a consistent interface to Caching in your application. It allows you
 * to use several different Cache engines, without coupling your application to a specific
 * implementation. It also allows you to change out cache storage or configuration without effecting
 * the rest of your application.
 *
 * ### Configuring Cache engines
 *
 * You can configure Cache engines in your application's `Config/cache.php` file.
 * A sample configuration would be:
 *
 * {{{
 * Cache::config('shared', [
 *    'className' => 'Cake\Cache\Engine\ApcEngine',
 *    'prefix' => 'my_app_'
 * ]);
 * }}}
 *
 * This would configure an APC cache engine to the 'shared' alias. You could then read and write
 * to that cache alias by using it for the `$config` parameter in the various Cache methods.
 *
 * In general all Cache operations are supported by all cache engines.
 * However, Cache::increment() and Cache::decrement() are not supported by File caching.
 *
 * There are 5 built-in caching engines:
 *
 * - `FileEngine` - Uses simple files to store content. Poor performance, but good for
 *    storing large objects, or things that are not IO sensitive.  Well suited to development
 *    as it is an easy cache to inspect and manually flush.
 * - `ApcEngine` - Uses the APC object cache, one of the fastest caching engines.
 * - `MemcacheEngine` - Uses the PECL::Memcache extension and Memcached for storage.
 *   Fast reads/writes, and benefits from memcache being distributed.
 * - `XcacheEngine` - Uses the Xcache extension, an alternative to APC.
 * - `WincacheEngine` - Uses Windows Cache Extension for PHP. Supports wincache 1.1.0 and higher.
 *   This engine is recommended to people deploying on windows with IIS.
 * - `RedisEngine` - Uses redis and php-redis extension to store cache data.
 *
 * See Cache engine documentation for expected configuration keys.
 *
 * @see config/app.php for configuration settings
 * @param string $name Name of the configuration
 * @param array $config Optional associative array of settings passed to the engine
 * @return array [engine, settings] on success, false on failure
 * @throws \Cake\Core\Error\Exception
 */
class Cache {

	use StaticConfigTrait;

/**
 * Flag for tracking whether or not caching is enabled.
 *
 * @var bool
 */
	protected static $_enabled = true;

/**
 * Group to Config mapping
 *
 * @var array
 */
	protected static $_groups = [];

/**
 * Whether to reset the settings with the next call to Cache::set();
 *
 * @var array
 */
	protected static $_reset = false;

/**
 * Cache Registry used for creating and using cache adapters.
 *
 * @var \Cake\Cache\CacheRegistry
 */
	protected static $_registry;

/**
 * Finds and builds the instance of the required engine class.
 *
 * @param string $name Name of the config array that needs an engine instance built
 * @return void
 * @throws \Cake\Core\Error\Exception When a cache engine cannot be created.
 */
	protected static function _buildEngine($name) {
		if (empty(static::$_registry)) {
			static::$_registry = new CacheRegistry();
		}
		if (empty(static::$_config[$name]['className'])) {
			throw new Exception(sprintf('The "%s" cache configuration does not exist.', $name));
		}

		$config = static::$_config[$name];
		static::$_registry->load($name, $config);

		if (!empty($config['groups'])) {
			foreach ($config['groups'] as $group) {
				static::$_groups[$group][] = $name;
				static::$_groups[$group] = array_unique(static::$_groups[$group]);
				sort(static::$_groups[$group]);
			}
		}
	}

/**
 * Fetch the engine attached to a specific configuration name.
 *
 * If the cache engine & configuration are missing an error will be
 * triggered.
 *
 * @param string $config The configuration name you want an engine for.
 * @return \Cake\Cache\CacheEngine When caching is disabled a null engine will be returned.
 */
	public static function engine($config) {
		if (!static::$_enabled) {
			return new NullEngine();
		}

		if (isset(static::$_registry->{$config})) {
			return static::$_registry->{$config};
		}

		static::_buildEngine($config);
		return static::$_registry->{$config};
	}

/**
 * Garbage collection
 *
 * Permanently remove all expired and deleted data
 *
 * @param string $config [optional] The config name you wish to have garbage collected. Defaults to 'default'
 * @param int $expires [optional] An expires timestamp. Defaults to NULL
 * @return void
 */
	public static function gc($config = 'default', $expires = null) {
		$engine = static::engine($config);
		$engine->gc($expires);
	}

/**
 * Write data for key into cache.
 *
 * ### Usage:
 *
 * Writing to the active cache config:
 *
 * `Cache::write('cached_data', $data);`
 *
 * Writing to a specific cache config:
 *
 * `Cache::write('cached_data', $data, 'long_term');`
 *
 * @param string $key Identifier for the data
 * @param mixed $value Data to be cached - anything except a resource
 * @param string $config Optional string configuration name to write to. Defaults to 'default'
 * @return bool True if the data was successfully cached, false on failure
 */
	public static function write($key, $value, $config = 'default') {
		$engine = static::engine($config);
		if (is_resource($value)) {
			return false;
		}

		$success = $engine->write($key, $value);
		if ($success === false && $value !== '') {
			trigger_error(
				sprintf(
					"%s cache was unable to write '%s' to %s cache",
					$config,
					$key,
					get_class($engine)
				),
				E_USER_WARNING
			);
		}
		return $success;
	}

/**
 *  Write data for many keys into cache.
 *
 * ### Usage:
 *
 * Writing to the active cache config:
 *
 * `Cache::writeMany(['cached_data_1' => 'data 1', 'cached_data_2' => 'data 2']);`
 *
 * Writing to a specific cache config:
 *
 * `Cache::writeMany(['cached_data_1' => 'data 1', 'cached_data_2' => 'data 2'], 'long_term');`
 *
 * @param array $data An array of data to be stored in the cache
 * @param string $config Optional string configuration name to write to. Defaults to 'default'
 * @return array of bools for each key provided, indicating true for success or false for fail
 * @throws Cake\Core\Error\Exception
 */
	public static function writeMany($data, $config = 'default') {
		$engine = static::engine($config);
		$return = $engine->writeMany($data);
		foreach ($return as $key => $success) {
			if ($success === false && !empty($data[$key])) {
				throw new Exception(sprintf(
					'%s cache was unable to write \'%s\' to %s cache',
					$config,
					$key,
					get_class($engine)
				));
			}
		}
		return $return;
	}

/**
 * Read a key from the cache.
 *
 * ### Usage:
 *
 * Reading from the active cache configuration.
 *
 * `Cache::read('my_data');`
 *
 * Reading from a specific cache configuration.
 *
 * `Cache::read('my_data', 'long_term');`
 *
 * @param string $key Identifier for the data
 * @param string $config optional name of the configuration to use. Defaults to 'default'
 * @return mixed The cached data, or false if the data doesn't exist, has expired, or if there was an error fetching it
 */
	public static function read($key, $config = 'default') {
		$engine = static::engine($config);
		return $engine->read($key);
	}

/**
 * Read multiple keys from the cache.
 *
 * ### Usage:
 *
 * Reading multiple keys from the active cache configuration.
 *
 * `Cache::readMany(['my_data_1', 'my_data_2]);`
 *
 * Reading from a specific cache configuration.
 *
 * `Cache::readMany(['my_data_1', 'my_data_2], 'long_term');`
 *
 * @param array $keys an array of keys to fetch from the cache
 * @param string $config optional name of the configuration to use. Defaults to 'default'
 * @return array An array containing, for each of the given $keys, the cached data or false if cached data could not be
 * retreived
 */
	public static function readMany($keys, $config = 'default') {
		$engine = static::engine($config);
		return $engine->readMany($keys);
	}

/**
 * Increment a number under the key and return incremented value.
 *
 * @param string $key Identifier for the data
 * @param int $offset How much to add
 * @param string $config Optional string configuration name. Defaults to 'default'
 * @return mixed new value, or false if the data doesn't exist, is not integer,
 *    or if there was an error fetching it.
 */
	public static function increment($key, $offset = 1, $config = 'default') {
		$engine = static::engine($config);
		if (!is_int($offset) || $offset < 0) {
			return false;
		}

		return $engine->increment($key, $offset);
	}

/**
 * Decrement a number under the key and return decremented value.
 *
 * @param string $key Identifier for the data
 * @param int $offset How much to subtract
 * @param string $config Optional string configuration name. Defaults to 'default'
 * @return mixed new value, or false if the data doesn't exist, is not integer,
 *   or if there was an error fetching it
 */
	public static function decrement($key, $offset = 1, $config = 'default') {
		$engine = static::engine($config);
		if (!is_int($offset) || $offset < 0) {
			return false;
		}

		return $engine->decrement($key, $offset);
	}

/**
 * Delete a key from the cache.
 *
 * ### Usage:
 *
 * Deleting from the active cache configuration.
 *
 * `Cache::delete('my_data');`
 *
 * Deleting from a specific cache configuration.
 *
 * `Cache::delete('my_data', 'long_term');`
 *
 * @param string $key Identifier for the data
 * @param string $config name of the configuration to use. Defaults to 'default'
 * @return bool True if the value was successfully deleted, false if it didn't exist or couldn't be removed
 */
	public static function delete($key, $config = 'default') {
		$engine = static::engine($config);
		return $engine->delete($key);
	}

/**
 * Delete many keys from the cache.
 *
 * ### Usage:
 *
 * Deleting multiple keys from the active cache configuration.
 *
 * `Cache::deleteMany(['my_data_1', 'my_data_2']);`
 *
 * Deleting from a specific cache configuration.
 *
 * `Cache::deleteMany(['my_data_1', 'my_data_2], 'long_term');`
 *
 * @param array $keys Array of cache keys to be deleted
 * @param string $config name of the configuration to use. Defaults to 'default'
 * @return array of boolean values that are true if the value was successfully deleted, false if it didn't exist or
 * couldn't be removed
 */
	public static function deleteMany($keys, $config = 'default') {
		$engine = static::engine($config);
		return $engine->deleteMany($keys);
	}

/**
 * Delete all keys from the cache.
 *
 * @param bool $check if true will check expiration, otherwise delete all
 * @param string $config name of the configuration to use. Defaults to 'default'
 * @return bool True if the cache was successfully cleared, false otherwise
 */
	public static function clear($check = false, $config = 'default') {
		$engine = static::engine($config);
		return $engine->clear($check);
	}

/**
 * Delete all keys from the cache belonging to the same group.
 *
 * @param string $group name of the group to be cleared
 * @param string $config name of the configuration to use. Defaults to 'default'
 * @return bool True if the cache group was successfully cleared, false otherwise
 */
	public static function clearGroup($group, $config = 'default') {
		$engine = static::engine($config);
		return $engine->clearGroup($group);
	}

/**
 * Retrieve group names to config mapping.
 *
 * {{{
 * Cache::config('daily', ['duration' => '1 day', 'groups' => ['posts']]);
 * Cache::config('weekly', ['duration' => '1 week', 'groups' => ['posts', 'archive']]);
 * $configs = Cache::groupConfigs('posts');
 * }}}
 *
 * $config will equal to `['posts' => ['daily', 'weekly']]`
 *
 * @param string $group group name or null to retrieve all group mappings
 * @return array map of group and all configuration that has the same group
 * @throws \Cake\Core\Error\Exception
 */
	public static function groupConfigs($group = null) {
		if ($group === null) {
			return static::$_groups;
		}

		if (isset(self::$_groups[$group])) {
			return [$group => self::$_groups[$group]];
		}

		throw new Exception(sprintf('Invalid cache group %s', $group));
	}

/**
 * Re-enable caching.
 *
 * If caching has been disabled with Cache::disable() this method will reverse that effect.
 *
 * @return void
 */
	public static function enable() {
		static::$_enabled = true;
	}

/**
 * Disable caching.
 *
 * When disabled all cache operations will return null.
 *
 * @return void
 */
	public static function disable() {
		static::$_enabled = false;
	}

/**
 * Check whether or not caching is enabled.
 *
 * @return bool
 */
	public static function enabled() {
		return static::$_enabled;
	}

/**
 * Provides the ability to easily do read-through caching.
 *
 * When called if the $key is not set in $config, the $callable function
 * will be invoked. The results will then be stored into the cache config
 * at key.
 *
 * Examples:
 *
 * Using a Closure to provide data, assume `$this` is a Table object:
 *
 * {{{
 * $results = Cache::remember('all_articles', function() {
 *      return $this->find('all');
 * });
 * }}}
 *
 * @param string $key The cache key to read/store data at.
 * @param callable $callable The callable that provides data in the case when
 *   the cache key is empty. Can be any callable type supported by your PHP.
 * @param string $config The cache configuration to use for this operation.
 *   Defaults to default.
 * @return mixed If the key is found: the cached data, false if the data
 *   missing/expired, or an error. If the key is not found: boolean of the
 *   success of the write
 */
	public static function remember($key, $callable, $config = 'default') {
		$existing = self::read($key, $config);
		if ($existing !== false) {
			return $existing;
		}
		$results = call_user_func($callable);
		self::write($key, $results, $config);
		return $results;
	}

}