Indexer: Added page and meta value rename functions

With these functions that search index can be updated after page moves
or mass metadata updates without the need to reindex the whole
page/wiki. These functions will be used by the new pagemove plugin.

inc/indexer.php

@@ -338,6 +338,106 @@ class Doku_Indexer {
         return true;
     }
 
+    /**
+     * Rename a page in the search index without changing the indexed content
+     *
+     * @param string $oldpage The old page name
+     * @param string $newpage The new page name
+     * @return string|bool If the page was successfully renamed, can be a message in the case of an error
+     */
+    public function renamePage($oldpage, $newpage) {
+        if (!$this->lock()) return 'locked';
+
+        $pages = $this->getPages();
+
+        $id = array_search($oldpage, $pages);
+        if ($id === false) {
+            $this->unlock();
+            return 'page is not in index';
+        }
+
+        $new_id = array_search($newpage, $pages);
+        if ($new_id !== false) {
+            $this->unlock();
+            // make sure the page is not in the index anymore
+            $this->deletePage($newpage);
+            if (!$this->lock()) return 'locked';
+
+            $pages[$new_id] = 'deleted:'.time().rand(0, 9999);
+        }
+
+        $pages[$id] = $newpage;
+
+        // update index
+        if (!$this->saveIndex('page', '', $pages)) {
+            $this->unlock();
+            return false;
+        }
+
+        // reset the pid cache
+        $this->pidCache = array();
+
+        $this->unlock();
+        return true;
+    }
+
+    /**
+     * Renames a meta value in the index. This doesn't change the meta value in the pages, it assumes that all pages
+     * will be updated.
+     *
+     * @param string $key       The metadata key of which a value shall be changed
+     * @param string $oldvalue  The old value that shall be renamed
+     * @param string $newvalue  The new value to which the old value shall be renamed, can exist (then values will be merged)
+     * @return bool|string      If renaming the value has been successful, false or error message on error.
+     */
+    public function renameMetaValue($key, $oldvalue, $newvalue) {
+        if (!$this->lock()) return 'locked';
+
+        // change the relation references index
+        $metavalues = $this->getIndex($key, '_w');
+        $oldid = array_search($oldvalue, $metavalues);
+        if ($oldid !== false) {
+            $newid = array_search($newvalue, $metavalues);
+            if ($newid !== false) {
+                // free memory
+                unset ($metavalues);
+
+                // okay, now we have two entries for the same value. we need to merge them.
+                $indexline = $this->getIndexKey($key, '_i', $oldid);
+                if ($indexline != '') {
+                    $newindexline = $this->getIndexKey($key, '_i', $newid);
+                    $pagekeys     = $this->getIndex($key, '_p');
+                    $parts = explode(':', $indexline);
+                    foreach ($parts as $part) {
+                        list($id, $count) = explode('*', $part);
+                        $newindexline =  $this->updateTuple($newindexline, $id, $count);
+
+                        $keyline = explode(':', $pagekeys[$id]);
+                        // remove old meta value
+                        $keyline = array_diff($keyline, array($oldid));
+                        // add new meta value when not already present
+                        if (!in_array($newid, $keyline)) {
+                            array_push($keyline, $newid);
+                        }
+                        $pagekeys[$id] = implode(':', $keyline);
+                    }
+                    $this->saveIndex($key, '_p', $pagekeys);
+                    unset($pagekeys);
+                    $this->saveIndexKey($key, '_i', $oldid, '');
+                    $this->saveIndexKey($key, '_i', $newid, $newindexline);
+                }
+            } else {
+                $metavalues[$oldid] = $newvalue;
+                if (!$this->saveIndex($key, '_w', $metavalues)) {
+                    $this->unlock();
+                    return false;
+                }
+            }
+        }
+
+        $this->unlock();
+        return true;
+    }
     /**
      * Remove a page from the index
      *