1 files changed, 89 insertions, 0 deletions
diff --git a/lib/HttpCachingBridgeAbstract.php b/lib/HttpCachingBridgeAbstract.php
new file mode 100644
index 00000000..15cddc5b
--- /dev/null
+++ b/lib/HttpCachingBridgeAbstract.php
@@ -0,0 +1,89 @@
+<?php
+require_once(__DIR__ . '/BridgeInterface.php');
+/**
+ * Extension of BridgeAbstract allowing caching of files downloaded over http.
+ * TODO allow file cache invalidation by touching files on access, and removing
+ * files/directories which have not been touched since ... a long time
+ */
+abstract class HttpCachingBridgeAbstract extends BridgeAbstract {
+
+    /**
+     * Maintain locally cached versions of pages to download, to avoid multiple downloads.
+     * @param url url to cache
+     * @return content of the file as string
+     */
+    public function get_cached($url){
+        // TODO build this from the variable given to Cache
+        $cacheDir = __DIR__ . '/../cache/pages/';
+        $filepath = $this->buildCacheFilePath($url, $cacheDir);
+
+        if(file_exists($filepath)){
+            $this->debugMessage('loading cached file from ' . $filepath . ' for page at url ' . $url);
+            // TODO touch file and its parent, and try to do neighbour deletion
+            $this->refresh_in_cache($cacheDir, $filepath);
+            $content = file_get_contents($filepath);
+        } else {
+            $this->debugMessage('we have no local copy of ' . $url . ' Downloading to ' . $filepath);
+            $dir = substr($filepath, 0, strrpos($filepath, '/'));
+
+            if(!is_dir($dir)){
+                $this->debugMessage('creating directories for ' . $dir);
+                mkdir($dir, 0777, true);
+            }
+
+            $content = $this->getContents($url);
+            if($content !== false){
+                file_put_contents($filepath, $content);
+            }
+        }
+
+        return str_get_html($content);
+    }
+
+     public function get_cached_time($url){
+        // TODO build this from the variable given to Cache
+        $cacheDir = __DIR__ . '/../cache/pages/';
+        $filepath = $this->buildCacheFilePath($url, $cacheDir);
+
+        if(!file_exists($filepath)){
+            $this->get_cached($url);
+        }
+
+        return filectime($filepath);
+    }
+
+    private function refresh_in_cache($cacheDir, $filepath){
+        $currentPath = $filepath;
+        while(!$cacheDir == $currentPath){
+            touch($currentPath);
+            $currentPath = dirname($currentPath);
+        }
+    }
+
+    private function buildCacheFilePath($url, $cacheDir){
+        $simplified_url = str_replace(
+            ['http://', 'https://', '?', '&', '='],
+            ['', '', '/', '/', '/'],
+            $url);
+
+        if(substr($cacheDir, -1) !== '/'){
+            $cacheDir .= '/';
+        }
+
+        $filepath = $cacheDir . $simplified_url;
+
+        if(substr($filepath, -1) === '/'){
+            $filepath .= 'index.html';
+        }
+
+        return $filepath;
+    }
+
+    public function remove_from_cache($url){
+        // TODO build this from the variable given to Cache
+        $cacheDir = __DIR__ . '/../cache/pages/';
+        $filepath = $this->buildCacheFilePath($url, $cacheDir);
+        $this->debugMessage('removing from cache \'' . $filepath . '\'');
+        unlink($filepath);
+    }
+}