caches: Refactor the API (#1060)

- For consistency, functions should always return null on non-existing data.

- WordPressPluginUpdateBridge appears to have used its own cache instance in the past. Obviously not used anymore.

- Since $key can be anything, the cache implementation must ensure to assign the related data reliably; most commonly by serializing and hashing the key in an appropriate way.

- Even though the default path for storage is perfectly fine, some people may want to use a different location. This is an example how a cache implementation is responsible for its requirements.

actions/DisplayAction.php

@@ -86,9 +86,9 @@ class DisplayAction extends ActionAbstract {
 
 		// Initialize cache
 		$cache = Cache::create(Configuration::getConfig('cache', 'type'));
-		$cache->setPath(PATH_CACHE);
+		$cache->setScope('');
 		$cache->purgeCache(86400); // 24 hours
-		$cache->setParameters($cache_params);
+		$cache->setKey($cache_params);
 
 		$items = array();
 		$infos = array();

bridges/ElloBridge.php

@@ -121,8 +121,8 @@ class ElloBridge extends BridgeAbstract {
 
 	private function getAPIKey() {
 		$cache = Cache::create(Configuration::getConfig('cache', 'type'));
-		$cache->setPath(PATH_CACHE);
-		$cache->setParameters(['key']);
+		$cache->setScope(get_called_class());
+		$cache->setKey(['key']);
 		$key = $cache->loadData();
 
 		if($key == null) {

bridges/WordPressPluginUpdateBridge.php

@@ -71,16 +71,4 @@ class WordPressPluginUpdateBridge extends BridgeAbstract {
 
 		return parent::getName();
 	}
-
-	private function getCachedDate($url){
-		Debug::log('getting pubdate from url ' . $url . '');
-		// Initialize cache
-		$cache = Cache::create(Configuration::getConfig('cache', 'type'));
-		$cache->setPath(PATH_CACHE . 'pages/');
-		$params = [$url];
-		$cache->setParameters($params);
-		// Get cachefile timestamp
-		$time = $cache->getTime();
-		return ($time !== false ? $time : time());
-	}
 }

caches/FileCache.php

@@ -3,20 +3,21 @@
 * Cache with file system
 */
 class FileCache implements CacheInterface {
-
 	protected $path;
-	protected $param;
+	protected $key;
 
 	public function loadData(){
 		if(file_exists($this->getCacheFile())) {
 			return unserialize(file_get_contents($this->getCacheFile()));
 		}
+
+		return null;
 	}
 
-	public function saveData($datas){
+	public function saveData($data){
 		// Notice: We use plain serialize() here to reduce memory footprint on
 		// large input data.
-		$writeStream = file_put_contents($this->getCacheFile(), serialize($datas));
+		$writeStream = file_put_contents($this->getCacheFile(), serialize($data));
 
 		if($writeStream === false) {
 			throw new \Exception('Cannot write the cache... Do you have the right permissions ?');
@@ -29,13 +30,14 @@ class FileCache implements CacheInterface {
 		$cacheFile = $this->getCacheFile();
 		clearstatcache(false, $cacheFile);
 		if(file_exists($cacheFile)) {
-			return filemtime($cacheFile);
+			$time = filemtime($cacheFile);
+			return ($time !== false) ? $time : null;
 		}
 
-		return false;
+		return null;
 	}
 
-	public function purgeCache($duration){
+	public function purgeCache($seconds){
 		$cachePath = $this->getPath();
 		if(file_exists($cachePath)) {
 			$cacheIterator = new RecursiveIteratorIterator(
@@ -47,7 +49,7 @@ class FileCache implements CacheInterface {
 				if(in_array($cacheFile->getBasename(), array('.', '..', '.gitkeep')))
 					continue;
 				elseif($cacheFile->isFile()) {
-					if(filemtime($cacheFile->getPathname()) < time() - $duration)
+					if(filemtime($cacheFile->getPathname()) < time() - $seconds)
 						unlink($cacheFile->getPathname());
 				}
 			}
@@ -55,34 +57,34 @@ class FileCache implements CacheInterface {
 	}
 
 	/**
-	* Set cache path
+	* Set scope
 	* @return self
 	*/
-	public function setPath($path){
-		if(is_null($path) || !is_string($path)) {
-			throw new \Exception('The given path is invalid!');
+	public function setScope($scope){
+		if(is_null($scope) || !is_string($scope)) {
+			throw new \Exception('The given scope is invalid!');
 		}
 
-		$this->path = $path;
-
-		// Make sure path ends with '/' or '\'
-		$lastchar = substr($this->path, -1, 1);
-		if($lastchar !== '/' && $lastchar !== '\\')
-			$this->path .= '/';
-
-		if(!is_dir($this->path))
-			mkdir($this->path, 0755, true);
+		$this->path = PATH_CACHE . trim($scope, " \t\n\r\0\x0B\\\/") . '/';
 
 		return $this;
 	}
 
 	/**
-	* Set HTTP GET parameters
+	* Set key
 	* @return self
 	*/
-	public function setParameters(array $param){
-		$this->param = array_map('strtolower', $param);
+	public function setKey($key){
+		if (!empty($key) && is_array($key)) {
+			$key = array_map('strtolower', $key);
+		}
+		$key = json_encode($key);
 
+		if (!is_string($key)) {
+			throw new \Exception('The given key is invalid!');
+		}
+
+		$this->key = $key;
 		return $this;
 	}
 
@@ -90,9 +92,15 @@ class FileCache implements CacheInterface {
 	* Return cache path (and create if not exist)
 	* @return string Cache path
 	*/
-	protected function getPath(){
+	private function getPath(){
 		if(is_null($this->path)) {
-			throw new \Exception('Call "setPath" first!');
+			throw new \Exception('Call "setScope" first!');
+		}
+
+		if(!is_dir($this->path)) {
+			if (mkdir($this->path, 0755, true) !== true) {
+				throw new \Exception('Unable to create ' . $this->path);
+			}
 		}
 
 		return $this->path;
@@ -102,7 +110,7 @@ class FileCache implements CacheInterface {
 	* Get the file name use for cache store
 	* @return string Path to the file cache
 	*/
-	protected function getCacheFile(){
+	private function getCacheFile(){
 		return $this->getPath() . $this->getCacheName();
 	}
 
@@ -110,13 +118,11 @@ class FileCache implements CacheInterface {
 	* Determines file name for store the cache
 	* return string
 	*/
-	protected function getCacheName(){
-		if(is_null($this->param)) {
-			throw new \Exception('Call "setParameters" first!');
+	private function getCacheName(){
+		if(is_null($this->key)) {
+			throw new \Exception('Call "setKey" first!');
 		}
 
-		// Change character when making incompatible changes to prevent loading
-		// errors due to incompatible file contents         \|/
-		return hash('md5', http_build_query($this->param) . 'A') . '.cache';
+		return hash('md5', $this->key) . '.cache';
 	}
 }

caches/SQLiteCache.php

@@ -3,16 +3,25 @@
  * Cache based on SQLite 3 <https://www.sqlite.org>
  */
 class SQLiteCache implements CacheInterface {
-	protected $path;
-	protected $param;
+	protected $scope;
+	protected $key;
 
 	private $db = null;
 
 	public function __construct() {
-		if (!extension_loaded('sqlite3'))
+		if (!extension_loaded('sqlite3')) {
 			die('"sqlite3" extension not loaded. Please check "php.ini"');
+		}
 
-		$file = PATH_CACHE . 'cache.sqlite';
+		$file = Configuration::getConfig(get_called_class(), 'file');
+		if (empty($file)) {
+			die('Configuration for ' . get_called_class() . ' missing. Please check your config.ini.php');
+		}
+		if (dirname($file) == '.') {
+			$file = PATH_CACHE . $file;
+		} elseif (!is_dir(dirname($file))) {
+			die('Invalid configuration for ' . get_called_class() . '. Please check your config.ini.php');
+		}
 
 		if (!is_file($file)) {
 			$this->db = new SQLite3($file);
@@ -39,10 +48,10 @@ class SQLiteCache implements CacheInterface {
 		return null;
 	}
 
-	public function saveData($datas){
+	public function saveData($data){
 		$Qupdate = $this->db->prepare('INSERT OR REPLACE INTO storage (key, value, updated) VALUES (:key, :value, :updated)');
 		$Qupdate->bindValue(':key', $this->getCacheKey());
-		$Qupdate->bindValue(':value', serialize($datas));
+		$Qupdate->bindValue(':value', serialize($data));
 		$Qupdate->bindValue(':updated', time());
 		$Qupdate->execute();
 
@@ -60,40 +69,53 @@ class SQLiteCache implements CacheInterface {
 			}
 		}
 
-		return false;
+		return null;
 	}
 
-	public function purgeCache($duration){
+	public function purgeCache($seconds){
 		$Qdelete = $this->db->prepare('DELETE FROM storage WHERE updated < :expired');
-		$Qdelete->bindValue(':expired', time() - $duration);
+		$Qdelete->bindValue(':expired', time() - $seconds);
 		$Qdelete->execute();
 	}
 
 	/**
-	* Set cache path
+	* Set scope
 	* @return self
 	*/
-	public function setPath($path){
-		$this->path = $path;
+	public function setScope($scope){
+		if(is_null($scope) || !is_string($scope)) {
+			throw new \Exception('The given scope is invalid!');
+		}
+
+		$this->scope = $scope;
 		return $this;
 	}
 
 	/**
-	* Set HTTP GET parameters
+	* Set key
 	* @return self
 	*/
-	public function setParameters(array $param){
-		$this->param = array_map('strtolower', $param);
+	public function setKey($key){
+		if (!empty($key) && is_array($key)) {
+			$key = array_map('strtolower', $key);
+		}
+		$key = json_encode($key);
+
+		if (!is_string($key)) {
+			throw new \Exception('The given key is invalid!');
+		}
+
+		$this->key = $key;
 		return $this;
 	}
 
 	////////////////////////////////////////////////////////////////////////////
 
-	protected function getCacheKey(){
-		if(is_null($this->param)) {
-			throw new \Exception('Call "setParameters" first!');
+	private function getCacheKey(){
+		if(is_null($this->key)) {
+			throw new \Exception('Call "setKey" first!');
 		}
 
-		return hash('sha1', $this->path . http_build_query($this->param), true);
+		return hash('sha1', $this->scope . $this->key, true);
 	}
 }

config.default.ini.php

@@ -52,3 +52,8 @@ username = ""
 ; The password for authentication. Insert this password when prompted for login.
 ; Use a strong password to prevent others from guessing your login!
 password = ""
+
+; --- Cache specific configuration ---------------------------------------------
+
+[SQLiteCache]
+file = "cache.sqlite"

lib/CacheInterface.php

@@ -13,38 +13,54 @@
 
 /**
  * The cache interface
- *
- * @todo Add missing function to the interface
- * @todo Explain parameters and return values in more detail
- * @todo Return self more often (to allow call chaining)
  */
 interface CacheInterface {
+	/**
+	 * Set scope of the current cache
+	 *
+	 * If $scope is an empty string, the cache is set to a global context.
+	 *
+	 * @param string $scope The scope the data is related to
+	 */
+	public function setScope($scope);
+
+	/**
+	 * Set key to assign the current data
+	 *
+	 * Since $key can be anything, the cache implementation must ensure to
+	 * assign the related data reliably; most commonly by serializing and
+	 * hashing the key in an appropriate way.
+	 *
+	 * @param array $key The key the data is related to
+	 */
+	public function setKey($key);
+
 	/**
 	 * Loads data from cache
 	 *
-	 * @return mixed The cache data
+	 * @return mixed The cached data or null
 	 */
 	public function loadData();
 
 	/**
 	 * Stores data to the cache
 	 *
-	 * @param mixed $datas The data to store
+	 * @param mixed $data The data to store
 	 * @return self The cache object
 	 */
-	public function saveData($datas);
+	public function saveData($data);
 
 	/**
-	 * Returns the timestamp for the curent cache file
+	 * Returns the timestamp for the curent cache data
 	 *
-	 * @return int Timestamp
+	 * @return int Timestamp or null
 	 */
 	public function getTime();
 
 	/**
-	 * Removes any data that is older than the specified duration from cache
+	 * Removes any data that is older than the specified age from cache
 	 *
-	 * @param int $duration The cache duration in seconds
+	 * @param int $seconds The cache age in seconds
 	 */
-	public function purgeCache($duration);
+	public function purgeCache($seconds);
 }

lib/contents.php

@@ -46,11 +46,11 @@ function getContents($url, $header = array(), $opts = array()){
 
 	// Initialize cache
 	$cache = Cache::create(Configuration::getConfig('cache', 'type'));
-	$cache->setPath(PATH_CACHE . 'server/');
+	$cache->setScope('server');
 	$cache->purgeCache(86400); // 24 hours (forced)
 
 	$params = [$url];
-	$cache->setParameters($params);
+	$cache->setKey($params);
 
 	// Use file_get_contents if in CLI mode with no root certificates defined
 	if(php_sapi_name() === 'cli' && empty(ini_get('curl.cainfo'))) {
@@ -271,11 +271,11 @@ function getSimpleHTMLDOMCached($url,
 
 	// Initialize cache
 	$cache = Cache::create(Configuration::getConfig('cache', 'type'));
-	$cache->setPath(PATH_CACHE . 'pages/');
+	$cache->setScope('pages');
 	$cache->purgeCache(86400); // 24 hours (forced)
 
 	$params = [$url];
-	$cache->setParameters($params);
+	$cache->setKey($params);
 
 	// Determine if cached file is within duration
 	$time = $cache->getTime();