Make caching a plugin system

lib/cache.php

@@ -0,0 +1,113 @@
+<?php
+/**
+ * StatusNet, the distributed open-source microblogging tool
+ *
+ * Cache interface plus default in-memory cache implementation
+ *
+ * PHP version 5
+ *
+ * LICENCE: This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  Cache
+ * @package   StatusNet
+ * @author    Evan Prodromou <evan@status.net>
+ * @copyright 2009 StatusNet, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link      http://status.net/
+ */
+
+/**
+ * Interface for caching
+ *
+ * An abstract interface for caching.
+ *
+ */
+
+class Cache
+{
+    var $_items = array();
+    static $_inst = null;
+
+    static function instance()
+    {
+        if (is_null(self::$_inst)) {
+            self::$_inst = new Cache();
+        }
+
+        return self::$_inst;
+    }
+
+    static function key($extra)
+    {
+        $base_key = common_config('memcached', 'base');
+
+        if (empty($base_key)) {
+            $base_key = common_keyize(common_config('site', 'name'));
+        }
+
+        return 'statusnet:' . $base_key . ':' . $extra;
+    }
+
+    static function keyize($str)
+    {
+        $str = strtolower($str);
+        $str = preg_replace('/\s/', '_', $str);
+        return $str;
+    }
+
+    function get($key)
+    {
+        $value = null;
+
+        if (!Event::handle('StartCacheGet', array(&$key, &$value))) {
+            if (array_key_exists($_items, $key)) {
+                common_log(LOG_INFO, 'Cache HIT for key ' . $key);
+                $value = $_items[$key];
+            } else {
+                common_log(LOG_INFO, 'Cache MISS for key ' . $key);
+            }
+            Event::handle('EndCacheGet', array($key, &$value));
+        }
+
+        return $value;
+    }
+
+    function set($key, $value, $flag=null, $expiry=null)
+    {
+        $success = false;
+
+        if (!Event::handle('StartCacheSet', array(&$key, &$value, &$flag, &$expiry, &$success))) {
+            common_log(LOG_INFO, 'Setting cache value for key ' . $key);
+            $_items[$key] = $value;
+            $success = true;
+            Event::handle('EndCacheSet', array($key, $value, $flag, $expiry));
+        }
+
+        return $success;
+    }
+
+    function delete($key)
+    {
+        $success = false;
+
+        if (!Event::handle('StartCacheDelete', array(&$key, &$success))) {
+            common_log(LOG_INFO, 'Deleting cache value for key ' . $key);
+            unset($_items[$key]);
+            $success = true;
+            Event::handle('EndCacheDelete', array($key));
+        }
+
+        return $success;
+    }
+}

lib/util.php

@@ -1384,42 +1384,17 @@ function common_session_token()
 
 function common_cache_key($extra)
 {
-    $base_key = common_config('memcached', 'base');
-
-    if (empty($base_key)) {
-        $base_key = common_keyize(common_config('site', 'name'));
-    }
-
-    return 'statusnet:' . $base_key . ':' . $extra;
+    return Cache::key($extra);
 }
 
 function common_keyize($str)
 {
-    $str = strtolower($str);
-    $str = preg_replace('/\s/', '_', $str);
-    return $str;
+    return Cache::keyize($str);
 }
 
 function common_memcache()
 {
-    static $cache = null;
-    if (!common_config('memcached', 'enabled')) {
-        return null;
-    } else {
-        if (!$cache) {
-            $cache = new Memcache();
-            $servers = common_config('memcached', 'server');
-            if (is_array($servers)) {
-                foreach($servers as $server) {
-                    $cache->addServer($server);
-                }
-            } else {
-                $cache->addServer($servers);
-            }
-            $cache->setCompressThreshold(20000, 0.2);
-        }
-        return $cache;
-    }
+    return Cache::instance();
 }
 
 function common_license_terms($uri)