<?php

/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @package    Zend_Cache
 * @copyright  Copyright (c) 2006 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */


/**
 * @package    Zend_Cache
 * @copyright  Copyright (c) 2006 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */
class Zend_Cache_Core 
{
    
    // ------------------
    // --- Properties ---
    // ------------------
    
    /**
     * Backend Object
     * 
     * @var object
     */
    private $_backend = null;
    
    /**
     * Available options
     * 
     * ====> (boolean) writeControl :  
     * - Enable / disable write control (the cache is read just after writing to detect corrupt entries)
     * - Enable write control will lightly slow the cache writing but not the cache reading
     * Write control can detect some corrupt cache files but maybe it's not a perfect control
     *
     * ====> (boolean) caching :
     * - Enable / disable caching
     * (can be very usefull for the debug of cached scripts)
     * 
     * ====> (boolean) automaticSerialization :
     * - Enable / disable automatic serialization
     * - It can be used to save directly datas which aren't strings (but it's slower)
     * 
     * ====> (int) automaticCleaningFactor :
     * - Disable / Tune the automatic cleaning process
     * - The automatic cleaning process destroy too old (for the given life time)
     *   cache files when a new cache file is written :
     *     0               => no automatic cache cleaning
     *     1               => systematic cache cleaning
     *     x (integer) > 1 => automatic cleaning randomly 1 times on x cache write    
     *
     * ====> (int) lifeTime :
     * - Cache lifetime (in seconds)
     * - If null, the cache is valid forever.
     * 
     * ====> (boolean) logging :
     * - If set to true, logging is activated (but the system is slower)
     * 
     * @var array available options
     */
    protected $_options = array(
        'writeControl' => true, 
        'caching' => true, 
        'automaticSerialization' => false,
        'automaticCleaningFactor' => 0,
        'lifeTime' => 3600,
        'logging' => false
    ); 
    
    /**
     * Array of options which have to be transfered to backend
     */
    protected static $_directivesList = array('lifeTime', 'logging');
    
    /**
     * Not used for the core, just a sort a hint to get a common setOption() method (for the core and for frontends)
     */
    protected $_specificOptions = array();
               
    /**
     * Last used cache id
     * 
     * @var string $_lastId
     */
    private $_lastId = null;

    
    // ----------------------
    // --- Public methods ---
    // ----------------------
     
    /**
     * Constructor
     * 
     * @param array $options associative array of options
     */
    public function __construct($options = array())
    {
        if (!is_array($options)) {
            Zend_Cache::throwException('Options parameter must be an array');
        }  
        while (list($name, $value) = each($options)) {
            $this->_setOption($name, $value);
        }
    }
    
    /**
     * Set the backend 
     * 
     * @param object $backendObject
     */
    public function setBackend($backendObject)
    {
        if (!is_object($backendObject)) {
            Zend_Cache::throwException('Incorrect backend object !');
        }
        $this->_backend= $backendObject;
        // some options (listed in $_directivesList) have to be given
        // to the backend too (even if they are not "backend specific") 
        $directives = array();
        foreach (Zend_Cache_Core::$_directivesList as $directive) {
            $directives[$directive] = $this->_options[$directive];
        }
        $this->_backend->setDirectives($directives);
    }
    
    /**
     * Public frontend to set an option
     * 
     * There is an additional validation (relatively to the protected _setOption method) 
     * 
     * @param string $name name of the option
     * @param mixed $value value of the option
     */
    public function setOption($name, $value)
    {
        if (is_string($name)) {
            if (array_key_exists($name, $this->_options)) {
            	// This is a Core option
                $this->_setOption($name, $value);
                return;
            }
            if (array_key_exists($name, $this->_specificOptions)) { 
        		// This a specic option of this frontend
                $this->_specificOptions[$name] = $value;
                return;
            }
        } 
        Zend_Cache::throwException("Incorrect option name : $name");
    }
    
    /**
     * Set an option
     * 
     * @param string $name name of the option
     * @param mixed $value value of the option
     */
    private function _setOption($name, $value)
    {
        if (!is_string($name) || !array_key_exists($name, $this->_options)) {
            Zend_Cache::throwException("Incorrect option name : $name");
        }
        $this->_options[$name] = $value;
        if ($name=='logging') {
            if ((!class_exists('Zend_Log', false)) && ($value)) {
                Zend_Cache::throwException('logging feature is on but Zend_Log is not "loaded"');    
            }
        }
    }
    
    /**
     * Force a new lifetime
     * 
     * The new value is set for the core/frontend but for the backend too (directive)
     * 
     * @param int $newLifeTime new lifetime (in seconds)
     */
    public function setLifeTime($newLifeTime)
    {
        $this->_options['lifeTime'] = $newLifeTime;
        $this->_backend->setDirectives(array(
            'lifeTime' => $newLifeTime
        ));
    }
    
    /**
     * Test if a cache is available for the given id and (if yes) return it (false else)
     * 
     * @param string $id cache id
     * @param boolean $doNotTestCacheValidity if set to true, the cache validity won't be tested
     * @param boolean $doNotUnserialize do not serialize (even if automaticSerialization is true) => for internal use
     * @return mixed cached datas (or false)
     */
    public function get($id, $doNotTestCacheValidity = false, $doNotUnserialize = false)
    {
        if (!$this->_options['caching']) {
            return false;
        }
        $this->_lastId = $id;        
        self::_validateIdOrTag($id);
        $data = $this->_backend->get($id, $doNotTestCacheValidity);
        if ($data===false) {
            // no cache available
            return false;
        }
        if ((!$doNotUnserialize) && $this->_options['automaticSerialization']) {
            // we need to unserialize before sending the result
            return unserialize($data);
        }
        return $data;
    }
    
    /**
     * Test if a cache is available for the given id 
     *
     * @param string $id cache id
     * @return boolean true is a cache is available, false else
     */
    public function test($id) 
    {
        if (!$this->_options['caching']) {
            return false;
        }
        self::_validateIdOrTag($id);
        $this->_lastId = $id;
        return $this->_backend->test($id);
    }
    
    /**
     * Save some data in a cache 
     * 
     * @param mixed $data data to put in cache (can be another type than string if automaticSerialization is on)
     * @param cache $id cache id (if not set, the last cache id will be used)
     * @param array $tags cache tags
     * @return boolean true if no problem
     */
    public function save($data, $id = null, $tags = array()) 
    {
        if (!$this->_options['caching']) {
            return true;
        }
        if (is_null($id)) {
            $id = $this->_lastId;
        }
        self::_validateIdOrTag($id);  
        self::_validateTagsArray($tags);   
        if ($this->_options['automaticSerialization']) {
            // we need to serialize datas before storing them
            $data = serialize($data);
        } else {
            if (!is_string($data)) {
                Zend_Cache::throwException("Datas must be string or set automaticSerialization = true");
            }
        }
        // automatic cleaning 
        if ($this->_options['automaticCleaningFactor'] > 0) {
            $rand = rand(1, $this->_options['automaticCleaningFactor']);
            if ($rand==1) {
                $this->clean('old');
            }
        }
        $result = $this->_backend->save($data, $id, $tags);
        if (!$result) {
            // maybe the cache is corrupted, so we remove it !
            if ($this->_options['logging']) {
                Zend_Log::log("Zend_Cache_Core::save() : impossible to save cache (id=$id)", Zend_Log::LEVEL_WARNING);
            }
            $this->remove($id);
            return false;
        }
        if ($this->_options['writeControl']) {
            $data2 = $this->_backend->get($id, true);
            if ($data!=$data2) {
                if ($this->_options['logging']) {
                    Zend_Log::log('Zend_Cache_Core::save() / writeControl : written and read data do not match', Zend_Log::LEVEL_WARNING);
                }
                $this->remove($id);
                return false;
            }
        }
        return true;
    }
    
    /**
     * Remove a cache 
     * 
     * @param string $id cache id to remove
     * @return boolean true if ok
     */
    public function remove($id)
    {
        if (!$this->_options['caching']) {
            return true;
        }
        self::_validateIdOrTag($id);
        return $this->_backend->remove($id);
    }
    
    /**
     * Clean cache entries
     * 
     * Available modes are :
     * 'all' (default)  => remove all cache entries ($tags is not used)
     * 'old'            => remove too old cache entries ($tags is not used) 
     * 'matchingTag'    => remove cache entries matching all given tags 
     *                     ($tags can be an array of strings or a single string) 
     * 'notMatchingTag' => remove cache entries not matching one of the given tags
     *                     ($tags can be an array of strings or a single string)                            
     * 
     * @param string $mode
     * @param mixed $parameters  
     * @return boolean true if ok
     */
    public function clean($mode = 'all', $tags = array())
    {
        if (!$this->_options['caching']) {
            return true;
        }
        if (!in_array($mode, array(Zend_Cache::CLEANING_MODE_ALL, Zend_Cache::CLEANING_MODE_OLD, Zend_Cache::CLEANING_MODE_MATCHING_TAG, Zend_Cache::CLEANING_MODE_NOT_MATCHING_TAG))) {
            Zend_Cache::throwException('Invalid cleaning mode');
        }
        self::_validateTagsArray($tags);
        return $this->_backend->clean($mode, $tags);
    }
       
    // ------------------------------------
    // --- Private or protected methods ---
    // ------------------------------------
       
    /**
     * Validate a cache id or a tag (security, reliable filenames, reserved prefixes...)
     * 
     * Throw an exception if a problem is found
     * 
     * @param string $string cache id or tag
     */
    private static function _validateIdOrTag($string)
    {
        if (!is_string($string)) {
            Zend_Cache::throwException('Invalid id or tag : must be a string');
        }
        if (substr($string, 0, 9) == 'internal_') {
            Zend_Cache::throwException('"internal_*" ids or tags are reserved');
        }
        if (!preg_match('~^[\w]+$~', $string)) {
            Zend_Cache::throwException('Invalid id or tag : must use only [a-zA-A0-9_]');
        }
    }
    
    /**
     * Validate a tags array (security, reliable filenames, reserved prefixes...)
     * 
     * Throw an exception if a problem is found
     * 
     * @param array $tags array of tags
     */
    private static function _validateTagsArray($tags)
    {
        if (!is_array($tags)) {
            Zend_Cache::throwException('Invalid tags array : must be an array');
        }
        foreach($tags as $tag) {
            self::_validateIdOrTag($tag);
        }
        reset($tags);
    }
             
}
