3 files changed, 105 insertions, 3 deletions

diff --git a/application/Cache.php b/application/Cache.php
new file mode 100644
index 00000000..5d050165
--- /dev/null
+++ b/application/Cache.php
@@ -0,0 +1,38 @@
+<?php
+/**
+ * Cache utilities
+ */
+
+/**
+ * Purges all cached pages
+ *
+ * @param string $pageCacheDir page cache directory
+ *
+ * @return mixed an error string if the directory is missing
+ */
+function purgeCachedPages($pageCacheDir)
+{
+    if (! is_dir($pageCacheDir)) {
+        $error = 'Cannot purge '.$pageCacheDir.': no directory';
+        error_log($error);
+        return $error;
+    }
+
+    array_map('unlink', glob($pageCacheDir.'/*.cache'));
+}
+
+/**
+ * Invalidates caches when the database is changed or the user logs out.
+ *
+ * @param string $pageCacheDir page cache directory
+ */
+function invalidateCaches($pageCacheDir)
+{
+    // Purge cache attached to session.
+    if (isset($_SESSION['tags'])) {
+        unset($_SESSION['tags']);
+    }
+
+    // Purge page cache shared by sessions.
+    purgeCachedPages($pageCacheDir);
+}
diff --git a/application/CachedPage.php b/application/CachedPage.php
new file mode 100644
index 00000000..50cfa9ac
--- /dev/null
+++ b/application/CachedPage.php
@@ -0,0 +1,63 @@
+<?php
+/**
+ * Simple cache system, mainly for the RSS/ATOM feeds
+ */
+class CachedPage
+{
+    // Directory containing page caches
+    private $cacheDir;
+
+    // Full URL of the page to cache -typically the value returned by pageUrl()
+    private $url;
+
+    // Should this URL be cached (boolean)?
+    private $shouldBeCached;
+
+    // Name of the cache file for this URL
+    private $filename;
+
+    /**
+     * Creates a new CachedPage
+     *
+     * @param string $cacheDir       page cache directory
+     * @param string $url            page URL
+     * @param bool   $shouldBeCached whether this page needs to be cached
+     */
+    public function __construct($cacheDir, $url, $shouldBeCached)
+    {
+        // TODO: check write access to the cache directory
+        $this->cacheDir = $cacheDir;
+        $this->url = $url;
+        $this->filename = $this->cacheDir.'/'.sha1($url).'.cache';
+        $this->shouldBeCached = $shouldBeCached;
+    }
+
+    /**
+     * Returns the cached version of a page, if it exists and should be cached
+     *
+     * @return a cached version of the page if it exists, null otherwise
+     */
+    public function cachedVersion()
+    {
+        if (!$this->shouldBeCached) {
+            return null;
+        }
+        if (is_file($this->filename)) {
+            return file_get_contents($this->filename);
+        }
+        return null;
+    }
+
+    /**
+     * Puts a page in the cache
+     *
+     * @param string $pageContent XML content to cache
+     */
+    public function cache($pageContent)
+    {
+        if (!$this->shouldBeCached) {
+            return;
+        }
+        file_put_contents($this->filename, $pageContent);
+    }
+}
diff --git a/application/LinkDB.php b/application/LinkDB.php
index 1e16fef1..463aa47e 100644
--- a/application/LinkDB.php
+++ b/application/LinkDB.php
@@ -269,8 +269,10 @@ You use the community supported version of the original Shaarli project, by Seba
 
     /**
      * Saves the database from memory to disk
+     *
+     * @param string $pageCacheDir page cache directory
      */
-    public function savedb()
+    public function savedb($pageCacheDir)
     {
         if (!$this->_loggedIn) {
             // TODO: raise an Exception instead
@@ -280,7 +282,7 @@ You use the community supported version of the original Shaarli project, by Seba
             $this->_datastore,
             self::$phpPrefix.base64_encode(gzdeflate(serialize($this->_links))).self::$phpSuffix
         );
-        invalidateCaches();
+        invalidateCaches($pageCacheDir);
     }
 
     /**
@@ -439,4 +441,3 @@ You use the community supported version of the original Shaarli project, by Seba
         return $linkDays;
     }
 }
-?>