diff --git a/src/controller/DiagramController.php b/src/controller/DiagramController.php
index ac466e8..f068dcd 100644
--- a/src/controller/DiagramController.php
+++ b/src/controller/DiagramController.php
@@ -1,509 +1,546 @@
 <?php
 final class DiagramController extends PhabricatorController {
   /**
    * Processes incoming HTTP requests from Diagram application
    */
   public function handleRequest(AphrontRequest $request) {
 
     $this->setRequest($request);
 
     // detetermine if GET or POST HTTP call
     if ($request->isHTTPPost()) {
       // process POST calls (like save action)
       return $this->handleHttpPostCall($request);
     }
 
     // determine type of URL by means of DiagramApplication route parameters
     $diagramphid = $request->getURIData('diagramphid');
     $diagramid = $request->getURIData('diagramid');
     $versioneddiagramid = $request->getURIData('versioneddiagramid');
     $version = $request->getURIData('version');
     $route = $request->getURIData('route');
     $versioninfoDiagramID = $request->getURIData('versioninfodiagram');
     $versioninfoPage = $request->getURIData('versioninfopage');
 
     if (isset($diagramphid) && !empty(trim($diagramphid))) {
       // return PNG image data
       $diagram = id(new DiagramVersion())->loadByDiagramPHID($diagramphid);
       if ($diagram !== null) {
         $response = new AphrontFileResponse();
         $response->setMimeType('image/png');
         $response->setContent($diagram->getData());
         return $response;
       }
     }
 
     if (isset($versioninfoDiagramID) && !empty(trim($versioninfoDiagramID))) {
       // return diagram version info
       if (!isset($versioninfoPage) || empty(trim($versioninfoPage))) {
         // versioninfoPage was dismissed -> initialize to 1
         $versioninfoPage = "1";
       }
 
       $diagramVersions = id(new DiagramVersion())->loadByDiagramID($versioninfoDiagramID);
       if ($diagramVersions !== null) {
         $result = [];
         $viewer = $request->getViewer();
 
         // determine total count of versions
         $totalcount = count($diagramVersions);
 
         // filter out some of the versions we want to show
         $pageSize = 10;
-        $diagramVersions = array_slice($diagramVersions, 
+        $diagramVersions = array_slice($diagramVersions,
                                        ($versioninfoPage - 1) * $pageSize,
                                        $pageSize
                                       );
 
         // calculate number of pages
         $totalpages = ceil($totalcount / $pageSize);
 
         // create menu-items
         foreach ($diagramVersions as $diagramVersion) {
           $author = $diagramVersion->getAuthorPHID();
 
           $user = id(new PhabricatorPeopleQuery())
             ->setViewer($viewer)
             ->withPHIDs(array(
               $author
             ))
             ->executeOne();
 
           $dateModified = $diagramVersion->getDateModified();
 
           $result[] = array(
             "id" => $diagramVersion->getVersion(),
             "datetime" => phabricator_datetime($dateModified, $viewer),
             "author" => $user->getUsername()
           );
         }
 
         // reply back
         $response = id(new AphrontJSONResponse())->setAddJSONShield(false)
           ->setContent(array(
             "data" => $result,
             "pagecount" => $totalpages,
             "nopager" => $totalcount <= $pageSize
           ));
         return $response;
       } else {
         // version info requested for inexistant diagram
         $response = id(new AphrontJSONResponse())->setAddJSONShield(false)
           ->setContent(array(
             "data" => array(),
             "pagecount" => 0
           ));
         return $response;
       }
     }
 
     $root = '';
     $file = rtrim($request->getPath(), '/');
     $root = dirname(phutil_get_library_root('diagram'));
 
     // determine from which application area the file should be loaded:
     //    1) Phorge extension source
     // or 2) drawio source
     if ($route == 'iframe') {
       // load from drawio source
       if ($file == '/diagram/iframe')
         $file .= '/index.html';
       if ($versioneddiagramid != null && $version != null) {
         $file = preg_replace("/^\/diagram\/" . $versioneddiagramid . "\/" . $version ."iframe\//",
           "data/drawio/src/main/webapp/",
           $file);
       } else {
         $file = preg_replace("/^\/diagram\/(" . $diagramid . "\/?)?iframe\//",
           "data/drawio/src/main/webapp/",
           $file);
       }
     } else {
       // load from extension source
       if (rtrim($file, '/') == '/diagram') {
         return $this->showApplication($request);
       }
 
       if ($versioneddiagramid !== null && $version !== null) {
-        $file = preg_replace('/^\/diagram\/' . $versioneddiagramid . '\/'. $version . '\/?/', 
-          'data/', 
+        $file = preg_replace('/^\/diagram\/' . $versioneddiagramid . '\/'. $version . '\/?/',
+          'data/',
           $file
         );
         $file = rtrim($file, '/') . '/' . $versioneddiagramid;
       } else {
-        $file = preg_replace('/^\/diagram\/(' . $diagramid . '\/)?/', 
-          'data/', 
+        $file = preg_replace('/^\/diagram\/(' . $diagramid . '\/)?/',
+          'data/',
           $file
         );
       }
     }
 
     // determine full path
     $path = $root . '/' . $file;
 
     if (file_exists($path) == false || is_readable($path) == false) {
       if (preg_match('/^data\/DIAG(\d+)$/', $file, $matches)) {
         $diagram_id = (int) $matches[1];
         if ($version === null) {
           $diagram = id(new DiagramVersion())->loadLatestByDiagramID($diagram_id);
         } else {
           $diagram = id(new DiagramVersion())->loadByVersionedDiagramID($diagram_id, $version);
         }
         if ($diagram) {
           $data = $diagram->getData();
           $base64_data = base64_encode($data);
 
           return $this->showApplication(
             $request,
             'DIAG' . $diagram_id,
-            $version ?? "", 
+            $version ?? "",
             $base64_data
           );
         }
       }
 
       // Invalid URL
       $response = id(new Aphront404Response());
       return $response;
     } else {
       // process Iframe content
       switch (pathinfo($file, PATHINFO_EXTENSION)) {
         case 'html':
           $response = id(new PlainHtmlWebpageResponse())
             ->setFrameable(true)
             ->setContent(file_get_contents($path));
           break;
         case 'js':
           $response = new AphrontFileResponse();
           $response->setMimeType('application/javascript');
           break;
         case 'css':
           $response = new AphrontFileResponse();
           $response->setMimeType('text/css');
           break;
         case 'txt':
           $response = new AphrontFileResponse();
           $response->setMimeType('text/plain');
           break;
         case 'png':
           $response = new AphrontFileResponse();
           $response->setMimeType('image/png');
           break;
         case 'gif':
           $response = new AphrontFileResponse();
           $response->setMimeType('image/gif');
           break;
         case 'jpg':
         case 'jpeg':
           $response = new AphrontFileResponse();
           $response->setMimeType('image/jpeg');
           break;
         default:
           $response = new AphrontFileResponse();
           $response->setMimeType('application/octet-stream');
           break;
       }
       try {
         $response->setContent(file_get_contents($path));
       } catch (Exception $e) {
         $response->setContent($route);
       }
       return $response;
     }
   }
 
   /**
    * Compares the draw.io tEXt metadata from 2 PNG base64 strings.
    * The content looks like this:
    * <mxfile host="..." modified="..." agent="..." etag="..." version="..."...>
    *  <diagram id="O253AQcHVgjdl_wygdBA" name="Page-1">
    *    <mxGraphModel ...>
    *     <root>
    *      ...
    *     </mxCell>
    *    </root>
    *   </mxGraphModel>
    *  </diagram>
    * </mxfile>
-   * 
+   *
    * The modified and etag attributes of mxfile will always be different.
    * They are cut out before the 2 strings are compared.
    */
-  private function equalPngMetaData($base64_1, $base64_2) {
+  public static function equalPngMetaData($base64_1, $base64_2) {
     $base64 = array($base64_1, $base64_2);
     $textData = array();
     for ($i = 0; $i < 2; $i++) {
       $data = base64_decode($base64[$i]);
       $fp = fopen('data://text/plain;base64,' . base64_encode($data), 'rb');
       $sig = fread($fp, 8);
       if ($sig != "\x89PNG\x0d\x0a\x1a\x0a") {
         fclose($fp);
         return false;
       }
       $textData[$i] = array();
       while (!feof($fp)) {
-        $chunk = unpack('Nlength/a4type', fread($fp, 8));
+        try {
+          $chunk = unpack('Nlength/a4type', fread($fp, 8));
+        } catch (Exception $e) {
+          // invalid base64 data
+          return false;
+        }
         if ($chunk['type'] == 'IEND') break;
         if ($chunk['type'] == 'tEXt') {
           list($key, $val) = explode("\0", fread($fp, $chunk['length']));
           if ($key == 'mxfile') {
             // Decode the URL-encoded XML data
             $decodedVal = urldecode($val);
             // Load the XML and remove the modified and etag attributes
             $xml = simplexml_load_string($decodedVal);
             unset($xml->attributes()->modified);
             unset($xml->attributes()->etag);
             // Save the modified XML as the value
             $val = $xml->asXML();
           }
           $textData[$i][$key] = $val;
           fseek($fp, 4, SEEK_CUR);
         } else {
           fseek($fp, $chunk['length'] + 4, SEEK_CUR);
         }
       }
       fclose($fp);
     }
 
     if (isset($textData[0]['mxfile']) && isset($textData[1]['mxfile'])) {
       // Both arrays contain the mxfile key, compare their values
       return $textData[0]['mxfile'] == $textData[1]['mxfile'];
     } else {
       // At least one of the arrays does not contain the mxfile key, return false
       return false;
     }
   }
 
   /**
    * Processes HTTP POST calls from Diagram application, like 'Save' action
    */
   private function handleHttpPostCall(AphrontRequest $request) {
     $base64_data = $request->getStr("data");
     $diagram_id = $request->getStr("diagramID");
 
     // cut off "data:image/png;base64,"
     $base64_data = substr($base64_data, strpos($base64_data, ',') + 1);
 
     if ($diagram_id != "") {
       // check if we are trying to save the same data as the current data
       $diagram = id(new DiagramVersion())->loadLatestByDiagramID($diagram_id);
       if ($diagram !== null) {
         $data = $diagram->getData();
-        $old_base64_data = base64_encode($data);
+        $old_data = base64_encode($data);
 
-        if ($this->equalPngMetaData($base64_data, $old_base64_data)) {
+        if (DiagramController::equalPngMetaData($base64_data, $old_data)) {
           // data hasn't been modified
           // => do not create new version
           $response = id(new AphrontJSONResponse())->setAddJSONShield(false)
             ->setContent(array(
               "Status" => "OK",
               "DiagramID" => $diagram->getDiagramID(),
               "Version" => $diagram->getVersion()
             ));
           return $response;
         }
       }
     }
-    
+
     // Set the options for the new file
     $options = array(
       'name' => 'diagram.png',
       'viewPolicy' => PhabricatorPolicies::POLICY_USER,
       'mime-type' => 'image/png',
       'actor' => $this->getViewer(),
       'diagramID' => $diagram_id
     );
 
     try {
       // Create the new file object
       $diagram = DiagramVersion::newFromFileData($base64_data, $options);
 
       $response = id(new AphrontJSONResponse())->setAddJSONShield(false)
         ->setContent(array(
           "Status" => "OK",
           "DiagramID" => $diagram->getDiagramID(),
           "Version" => $diagram->getVersion()
         ));
       return $response;
     } catch (Exception $e) {
       $response = id(new AphrontJSONResponse())->setAddJSONShield(false)
         ->setContent(array(
           "Status" => "ERROR",
           "Error" => $e->getMessage(),
         ));
       return $response;
     }
   }
 
+  /**
+   * Verifies if the given base64 data is draw.io compatible
+   */
+  public static function isDrawioPngBase64($base64) {
+    $data = base64_decode($base64);
+    $fp = fopen('data://text/plain;base64,' . base64_encode($data), 'rb');
+    $sig = fread($fp, 8);
+    if ($sig != "\x89PNG\x0d\x0a\x1a\x0a") {
+      fclose($fp);
+      return false;
+    }
+    while (!feof($fp)) {
+      try {
+        $chunk = unpack('Nlength/a4type', fread($fp, 8));
+      } catch (Exception $e) {
+        // invalid base64 data
+        return false;
+      }
+      if ($chunk['type'] == 'IEND') break;
+      if ($chunk['type'] == 'tEXt') {
+        list($key, $val) = explode("\0", fread($fp, $chunk['length']));
+        if ($key == 'mxfile') {
+          fclose($fp);
+          return true;
+        }
+        fseek($fp, 4, SEEK_CUR);
+      } else {
+        fseek($fp, $chunk['length'] + 4, SEEK_CUR);
+      }
+    }
+    fclose($fp);
+    return false;
+  }
+
   /**
    * Shows the draw.io application integrated in Phorge's layout
    */
   private function showApplication(
     AphrontRequest $request,
     string $diagramName = null,
     string $diagramVersion = null,
     string $diagramBase64 = null
   ) {
     $content = phutil_tag(
       'div',
       array(),
       array(
         phutil_tag(
           'div',
           array(
             'id' => 'mainScreen',
           )),
         phutil_tag('div',
           array(),
           array(
             phutil_tag(
               'img',
               array(
                 'class' => 'drawio',
               )),
             phutil_tag('div',
               array(
                 'id' => 'loadingtext',
                 'class' => 'geBlock',
                 'style' => 'margin-top:80px;'
                 . 'text-align:center;'
                 . 'min-width:50%;'
                 . 'height:100vh;',
               ),
               array(
                 phutil_tag('h1',
                   array(),
                   'Flowchart Maker and Online Diagram Software'
                 ),
                 phutil_tag('p',
                   array(
                     'style' => 'width: 800px;'
                     . 'position: sticky;'
                     . 'left: calc(50% - 400px);',
                   ),
                   'draw.io is free online diagram software. '
                   . 'You can use it as a flowchart maker, network diagram '
                   . 'software, to create UML online, as an ER diagram tool, '
                   . 'to design database schema, to build BPMN online, as a '
                   . 'circuit diagram maker, and more. draw.io can import '
                   . '.vsdx, Gliffy™ and Lucidchart™ files . '
                 ),
                 phutil_tag(
                   'h2',
                   array(
                     'id' => 'geStatus',
                   ),
                   'Loading...'
                 ),
                 phutil_tag(
                   'div',
                   array(
                     'id' => 'spinnerLoading',
                   )),
                 phutil_tag(
                   'script',
                   array(),
                   'var spinnerOpts = {'
                   . 'hwaccel: false,'
                   . 'length: 24,'
                   . 'radius: 12,'
                   . 'shadow: false,'
                   . 'speed: 1.5,'
                   . 'trail: 60,'
                   . 'width: 8};'
                 )
               ))
           )),
         phutil_tag(
           'script',
           array(
             'src' => 'phorge_extension.js'
           ),
           ''
         ),
         phutil_tag(
           'script',
           array(),
           phutil_safe_html('loadJsExtension("'
             . $diagramName
             . '", "'
             . $diagramVersion
             . '", "'
             . $diagramBase64
             . '");')
         ),
         phutil_tag(
           'div',
           array(
             'class' => 'crumbs',
             'style' => 'top:48px;'
             . 'margin-left: 4px;'
             . 'position: fixed;'
             . 'font-weight: bold;'
           ),
           array(
             phutil_tag(
               'a',
               array(
                 'href' => '.'
               ),
               array(
                 phutil_tag(
                   'span',
                   array(
                     'class' => 'phui-font-fa fa-sitemap',
                     'style' => 'padding-right:5px;'
                   ))
               )),
             phutil_tag(
               'a',
               array(
                 'href' => '.'
               ),
               'Diagram'
             ),
             phutil_tag(
               'span',
               array(
                 'class' => 'diagramName',
                 'style' => 'display:none'
               ),
               array(
                 phutil_tag(
                   'span',
                   array(
                     'style' => 'margin: 5px;'
                     . 'opacity: .5;'
                   ),
                   '>'
                 ),
                 phutil_tag(
                   'a',
                   array(),
                   ''
                 ),
                 phutil_tag(
                   'span',
                   array(
                     'class' => 'version',
                     'style' => 'margin-left: 8px;'
-                    . 'color: #999;'
-                  ),
-                  '',
-                ),
+                    . 'color: #999;'),
+                  ''),
               ))
           ))
       ));
 
     $view = id(new PhabricatorStandardPageView())
       ->setRequest($request)
       ->setController($this)
       ->setDeviceReady(true)
       ->setTitle("Diagrams")
       ->appendChild($content);
 
     $response = id(new AphrontWebpageResponse())
       ->setContent($view->render());
 
     return $response;
   }
-}
\ No newline at end of file
+}
diff --git a/src/query/PhabricatorDiagramQuery.php b/src/query/PhabricatorDiagramQuery.php
index 8302219..c3627c3 100644
--- a/src/query/PhabricatorDiagramQuery.php
+++ b/src/query/PhabricatorDiagramQuery.php
@@ -1,73 +1,108 @@
 <?php
 
 final class PhabricatorDiagramQuery
   extends PhabricatorCursorPagedPolicyAwareQuery {
 
   protected $diagramIDs;
+  protected $modifiedAfter;
+  protected $modifiedBefore;
 
   public function withDiagramIDs(array $diagram_ids) {
     $this->diagramIDs = $diagram_ids;
     return $this;
   }
 
+  public function withIDs(array $diagram_ids) {
+    return $this->withDiagramIDs($diagram_ids);
+  }
+
+  public function withModifiedAfter($datetime) {
+    $this->modifiedAfter = $datetime;
+    return $this;
+  }
+
+  public function withModifiedBefore($datetime) {
+    $this->modifiedBefore = $datetime;
+    return $this;
+  }
+
   protected function loadPage() {
     $table = new DiagramVersion();
     $conn_r = $table->establishConnection('r');
 
     // we return a DiagramVersion object which has a different id
     // than the one we mention in the Remarkup code.
     // E.g. {DIAG1} may point to the 2nd version of the object.
     // Diagram's id is 1, but DiagramVersion's id is 2.
     // Because of this we abuse the id in the resultset a little bit
     $data = queryfx_all(
       $conn_r,
-      "SELECT result.diagramID AS id, /* abuse */
-              result.diagramID,
-              result.version,
-              result.phid,
-              result.authorPHID,
-              result.dateCreated,
-              result.dateModified,
-              result.byteSize,
-              result.data,
-              result.viewPolicy,
-              result.editPolicy
+      'SELECT *
        FROM (
-          SELECT data.*
-          FROM %T data
-          INNER JOIN (
-              SELECT MAX(id) AS id,
-                    diagramid
-              FROM %T
-              GROUP BY diagramid HAVING MAX(id)
-            ) filter
-            ON data.id = filter.id
-       ) result %Q %Q %Q",
+        SELECT result.diagramID AS id, /* abuse */
+                result.diagramID,
+                result.version,
+                result.phid,
+                result.authorPHID,
+                result.dateCreated,
+                result.dateModified,
+                result.byteSize,
+                result.data,
+                result.viewPolicy,
+                result.editPolicy
+        FROM (
+            SELECT data.*
+            FROM %T data
+            INNER JOIN (
+                SELECT MAX(id) AS id,
+                      diagramid
+                FROM %T
+                GROUP BY diagramid HAVING MAX(id)
+              ) filter
+              ON data.id = filter.id
+        ) result
+      ) r %Q %Q %Q',
       $table->getTableName(),
       $table->getTableName(),
       $this->buildWhereClause($conn_r),
       $this->buildOrderClause($conn_r),
       $this->buildLimitClause($conn_r));
 
     return $table->loadAllFromArray($data);
   }
 
   protected function buildWhereClause(AphrontDatabaseConnection $conn_r) {
     $where = array();
 
+    $where[] = $this->buildPagingClause($conn_r);
+
     if ($this->diagramIDs !== null) {
       $where[] = qsprintf(
         $conn_r,
         'diagramID IN (%Ld)',
         $this->diagramIDs);
     }
 
+    if ($this->modifiedAfter !== null) {
+      $where[] = qsprintf(
+        $conn_r,
+        'dateModified >= %d',
+        $this->modifiedAfter);
+    }
+
+    if ($this->modifiedBefore !== null) {
+      $where[] = qsprintf(
+        $conn_r,
+        'dateModified <= %d',
+        $this->modifiedBefore);
+    }
+
     return $this->formatWhereClause($conn_r, $where);
   }
   
   public function getQueryApplicationClass() {
     return DiagramApplication::class;
   }
 
 }
 
diff --git a/src/storage/DiagramVersion.php b/src/storage/DiagramVersion.php
index be98448..e896141 100644
--- a/src/storage/DiagramVersion.php
+++ b/src/storage/DiagramVersion.php
@@ -1,342 +1,371 @@
 <?php
 
 final class DiagramVersion extends DiagramDAO implements
   PhabricatorDestructibleInterface,
   PhabricatorPolicyInterface {
 
   /**
    * List of properties mapped to database table columns
    */
   protected $phid;
   protected $diagramID;
   protected $version;
   protected $authorPHID;
   protected $byteSize;
   protected $data;
   protected $viewPolicy;
   protected $editPolicy;
 
+  /**
+   * returns base64 of $data
+   */
+  public function getBase64Data() {
+    if ($this->data === null) {
+      return null;
+    }
+    return base64_encode($this->data);
+  }
+
+  /**
+   * returns the URL which links to the diagram PNG data
+   */
+  public function getDataURI() {
+    return PhabricatorEnv::getCDNURI(
+      '/diagram/data/'
+      .$this->getPHID());
+  }
+
   /**
    * Return an array of capabilities that this object type supports.
    * See PhabricatorPolicyCapability for a list of available capabilities.
-   * 
+   *
    * Interface: PhabricatorPolicyInterface
    */
   public function getCapabilities() {
     return array(
       PhabricatorPolicyCapability::CAN_VIEW,
       PhabricatorPolicyCapability::CAN_EDIT,
     );
   }
 
   /**
    * Return the policy for the given capability.
-   * 
+   *
    * Interface: PhabricatorPolicyInterface
    */
   public function getPolicy($capability) {
     switch ($capability) {
       case PhabricatorPolicyCapability::CAN_VIEW:
         return $this->viewPolicy;
       case PhabricatorPolicyCapability::CAN_EDIT:
         return $this->editPolicy;
       default:
         return PhabricatorPolicies::POLICY_NOONE;
     }
   }
 
   /**
    * Return the URL which links to the diagram PNG image
    */
   public function getViewURI() {
     if (!$this->getPHID()) {
       throw new Exception(
         pht('You must save a diagram before you can generate a view URI.')
       );
     }
 
     $uri = '/diagram/data/'
-      . $this->getPHID();
+      .$this->getPHID();
 
 
     return $uri;
   }
 
   /**
    * Configures application-wide storage settings.
    * This creates a mapping of the corresponding database table.
    */
   public function getConfiguration() {
     return array(
       self::CONFIG_AUX_PHID => true,
       self::CONFIG_COLUMN_SCHEMA => array(
         'diagramID' => 'uint32',
         'version' => 'uint32',
         'authorPHID' => 'phid',
         'byteSize' => 'uint64',
         'data' => 'bytes',
         'viewPolicy' => 'policy',
         'editPolicy' => 'policy',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'key_phid' => null,
         'key_diagramID_version' => array(
           'columns' => array('diagramID', 'version'),
           'unique' => true,
         ),
         'key_authorPHID' => array(
           'columns' => array('authorPHID'),
         ),
       ),
     ) +
       array(
         self::CONFIG_IDS => self::IDS_AUTOINCREMENT,
         self::CONFIG_TIMESTAMPS => true,
       );
   }
 
   /**
    * Return the name of the database table that is represented by this class
    */
   public function getTableName() {
     return 'diagram_version';
   }
 
   /**
    * Return a string that uniquely identifies the PHID type for this object
    * type. This is used by the PHID system to generate and manage PHIDs for
    * this object type.
    */
   public function getPHIDType() {
     return 'DGVN';
   }
 
   /**
    * Return true if the given user has the given capability automatically,
    * without needing to check the object's policy. For example, you might
    * return true here if the user is an administrator or if they own the
    * object.
-   * 
+   *
    * Interface: PhabricatorPolicyInterface
    */
   public function hasAutomaticCapability(
     $capability,
-    PhabricatorUser $viewer
-  ) {
+    PhabricatorUser $viewer) {
     return false;
   }
 
+  /**
+   * Creates and initializes a new DiagramVersion object
+   */
   public static function initializeNewDiagram(PhabricatorUser $actor) {
-    return id(new DiagramVersion())
+    return id(new self())
       ->setViewPolicy(PhabricatorPolicies::getMostOpenPolicy())
       ->setEditPolicy($actor->getPHID())
       ->setAuthorPHID($actor->getPHID())
       ->setVersion(1)
       ->setDateCreated(time())
       ->setDateModified(time());
   }
 
+  /**
+   * Creates a new DiagramVersion object and loads the given base64 data in it
+   */
   public static function newFromFileData(
     $base64_data,
-    array $params = array()
-  ) {
+    array $params = array()) {
     $actor = idx($params, 'actor');
     if (!$actor) {
       throw new Exception(pht('Missing required actor for new file data.'));
     }
 
     $diagramID = idx($params, 'diagramID');
     if (!is_numeric($diagramID)) {
       $diagramID = null;
     }
 
     $data = base64_decode($base64_data);
 
     $diagram = self::initializeNewDiagram($actor);
     $diagram->setByteSize(strlen($data));
     $diagram->setData($data);
     $diagram->setDiagramID($diagramID);
     $diagram->save();
 
     return $diagram;
   }
 
-  public function attachProjectPHIDs(array $phids) {
-    // Attach an array of project PHIDs to this object. This is used by the
-    // project system to manage project membership and visibility for this
-    // object.
-  }
-
+  /**
+   * Permanently destroy this object. This is used by the destructible
+   * interface to allow administrators to permanently delete objects from
+   * the system.
+   */
   public function destroyObjectPermanently(
-    PhabricatorDestructionEngine $engine
-  ) {
-    // Permanently destroy this object. This is used by the destructible
-    // interface to allow administrators to permanently delete objects from
-    // the system.
+    PhabricatorDestructionEngine $engine) {
     $this->openTransaction();
     $this->delete();
     $this->saveTransaction();
   }
 
+  /**
+   * Returns an ID which can be used for a newly created Diagram object
+   */
   public function generateDiagramID() {
     $conn_r = $this->establishConnection('r');
     $table_name = $this->getTableName();
     $max_diagram_id = queryfx_one(
       $conn_r,
       'SELECT MAX(diagramID) max_diagram_id FROM %T',
-      $table_name
-    )['max_diagram_id'];
-    return (int) $max_diagram_id + 1;
+      $table_name)['max_diagram_id'];
+    return (int)$max_diagram_id + 1;
   }
 
+  /**
+   * Returns all DiagramVersion objects for a given diagram
+   */
   public function loadByDiagramID($diagramID) {
     if (is_object($diagramID)) {
-      $diagramID = (string) $diagramID;
+      $diagramID = (string)$diagramID;
     }
 
     if (!$diagramID || (!is_int($diagramID) && !ctype_digit($diagramID))) {
       return null;
     }
 
     return $this->loadAllWhere(
       'diagramID = %d  ORDER BY version DESC',
-      $diagramID
-    );
+      $diagramID);
   }
 
+  /**
+   * Returns the latest version of the given diagram
+   */
   public function loadLatestByDiagramID($diagramID) {
     if (is_object($diagramID)) {
-      $diagramID = (string) $diagramID;
+      $diagramID = (string)$diagramID;
     }
 
     if (!$diagramID || (!is_int($diagramID) && !ctype_digit($diagramID))) {
       return null;
     }
 
     return $this->loadOneWhere(
       'diagramID = %d  ORDER BY version DESC LIMIT 1',
-      $diagramID
-    );
+      $diagramID);
   }
 
-  public function loadByDiagramPHID($diagramPHID) {
-    if (is_object($diagramPHID)) {
-      $diagramPHID = (string) $diagramPHID;
+  /**
+   * Returns a specific DiagramVersion object
+   */
+  public function loadByDiagramPHID($diagramVersionPHID) {
+    if (is_object($diagramVersionPHID)) {
+      $diagramVersionPHID = (string)$diagramVersionPHID;
     }
 
     return $this->loadOneWhere(
       'phid = %s  ORDER BY version DESC LIMIT 1',
-      $diagramPHID
-    );
+      $diagramVersionPHID);
   }
 
+  /**
+   * Returns a specific DiagramVersion object for a given diagram and
+   * version number
+   */
   public function loadByVersionedDiagramID($diagramID, $version) {
     if (is_object($diagramID)) {
-      $diagramID = (string) $diagramID;
+      $diagramID = (string)$diagramID;
     }
     if (is_object($version)) {
-      $version = (string) $version;
+      $version = (string)$version;
     }
 
     if (!$diagramID || (!is_int($diagramID) && !ctype_digit($diagramID))) {
       return null;
     }
 
     if (!$version || (!is_int($version) && !ctype_digit($version))) {
       return null;
     }
 
     return $this->loadOneWhere(
       'diagramID = %d  AND version = %d',
       $diagramID,
-      $version
-    );
+      $version);
   }
 
+  /**
+   * Stores a new diagram (version)
+   */
   public function save() {
     // Load the last record with the same PHID.
     $last_record = null;
     if ($this->getDiagramID() !== null) {
       $last_record = id(new PhabricatorDiagramQuery())
         ->setViewer(PhabricatorUser::getOmnipotentUser())
         ->withDiagramIDs(array($this->getDiagramID()))
         ->setLimit(1)
         ->executeOne();
     }
 
     if ($last_record === null) {
       // If there is no last record, this is a new diagram object.
       $this->setVersion(1);
       $newDiagram = new Diagram();
       $newDiagram->createNewDiagram();
       $this->setDiagramID($newDiagram->getID());
     } else {
       // If there is a last record, this is a new version of an existing
       // diagram object.
       $this->setVersion($last_record->getVersion() + 1);
       $this->setDateCreated($last_record->getDateCreated());
     }
 
     // Check if a row with the same PHID and version already exists
     $existing_record = null;
     if ($this->getPHID() !== null && $this->getVersion() !== null) {
       $existing_record = id(new PhabricatorDiagramQuery())
         ->setViewer(PhabricatorUser::getOmnipotentUser())
         ->withPHIDs(array($this->getPHID()))
         ->withWhere(
           array(
             array('version', '=', $this->getVersion()),
-          )
-        )
+          ))
         ->setLimit(1)
         ->executeOne();
     }
 
     if ($existing_record === null) {
       // If there is no existing record, create a new row in the table.
       $conn_w = $this->establishConnection('w');
       $table_name = $this->getTableName();
       $this->phid = $this->generatePHID();
       if ($this->diagramID === null) {
         $this->diagramID = $this->generateDiagramID();
       }
 
       $record = array(
         'phid' => $this->getPHID(),
         'diagramID' => $this->getDiagramID(),
         'version' => $this->getVersion(),
         'authorPHID' => $this->getAuthorPHID(),
         'dateCreated' => $this->getDateCreated(),
         'dateModified' => $this->getDateModified(),
         'byteSize' => $this->getByteSize(),
         'viewPolicy' => $this->getViewPolicy(),
         'editPolicy' => $this->getEditPolicy(),
         'data' => $this->getData(),
       );
       if ($this->getID() !== null) {
         // If the ID property is set, include it in the data to insert.
         $record['id'] = $this->getID();
       }
       queryfx(
         $conn_w,
         'INSERT INTO %T (%Q) VALUES (%Ls, %B)',
         $table_name,
         implode(', ', array_keys($record)),
         array_values(array_slice($record, 0, -1)),
-        end($record)
-      );
+        end($record));
 
       $this->id = $conn_w->getInsertID();
     } else {
       // If there is an existing record, throw an exception.
       throw new Exception(
         pht('A diagram with PHID "%s" and version "%s" already exists.',
           $this->getPHID(),
-          $this->getVersion()
-        )
+          $this->getVersion())
       );
     }
 
     return $this;
   }
-}
\ No newline at end of file
+}