diff --git a/README.txt b/README.txt
index 840b6e8..f6ff53d 100644
--- a/README.txt
+++ b/README.txt
@@ -5,6 +5,9 @@ the following interfaces in order for the h5p libraries to work:
 
  - TODO: Fill in here
 
-In addition frameworks need to implement:
+In addition frameworks need to do the following:
 
- - TODO: Fill in here
\ No newline at end of file
+ - Provide a form for uploading h5p packages.
+ - Place the uploaded h5p packages in a temporary directory
+
+See existing implementations for details. For instance the Drupal h5p module located on drupal.org/project/h5p
\ No newline at end of file
diff --git a/h5p.classes.php b/h5p.classes.php
index b50a5c6..ecf9a42 100644
--- a/h5p.classes.php
+++ b/h5p.classes.php
@@ -1,14 +1,184 @@
 <?php
 interface h5pFramework {
-  function setErrorMessage($message);
-  function setInfoMessage($message);
-  function translate($message, $replacements);
+  public function setErrorMessage($message);
+  public function setInfoMessage($message);
+  public function t($message, $replacements);
+  public function getUploadedH5pDir();
+  public function getTempPath();
+  public function getUploadedH5pPath();
 }
 
 class h5p {
-  public $h5pFramework;
+  public $h5pF;
+
   public function __construct($h5pFramework) {
-    $this->h5pFramework = $h5pFramework;
+    $this->h5pF = $h5pFramework;
+  }
+
+  public function validatePackage() {
+    // Requires PEAR
+    require_once 'Archive/Tar.php';
+
+    // Create a temporary dir to extract package in.
+    $tmp_dir = $this->h5pFramework->getTempDir();
+    $tmp_path = $this->h5pFramework->getTempPath();
+
+    // Extract and then remove the package file.
+    $tar = new Archive_Tar($tmp_path, 'bz2');
+    if (!$tar->extract($tmp_dir)) {
+      $this->setErrorMessage($this->t('The file you uploaded is not a valid HTML5 Pack.'));
+      $this->rRmdir($tmp_dir);
+      return;
+    }
+    unlink($tmp_path);
+
+    // Process content and libraries
+    $contents = array();
+    $tars = scandir($tmp_dir);
+    for ($i = 2, $s = count($tars); $i < $s; $i++) {
+      if (substr($tars[$i], -4) == '.tar') {
+        $tar_file = $tmp_dir . DIRECTORY_SEPARATOR . $tars[$i];
+        $tar_name = substr($tars[$i], 0, -4);
+        $tar_id = md5_file($tar_file);
+        $tar_time = filemtime($tar_file);
+
+        $content_path = $files_path . DIRECTORY_SEPARATOR . $tar_id;
+
+        // Extract content to our files dir.
+        if (is_dir($content_path)) {
+          continue; // We already have this content/library.
+        }
+
+        mkdir($content_path);
+        $tar = new Archive_Tar($tar_file);
+        if (!$tar->extract($content_path)) {
+          continue; // Wasn't a valid tar file.
+        }
+
+        if (preg_match('/[^a-z0-9\-]/', $tar_name)) {
+          $this->setErrorMessage($this->t('Invalid name: %name', array('%name' => $tar_name)));
+          $this->rRmdir($content_path);
+          continue;
+        }
+
+        // Go to extracted stuff and check it.
+        $json = file_get_contents($content_path . DIRECTORY_SEPARATOR . 'index.js');
+        if (!$json) {
+          $this->setErrorMessage($this->t('Could not find index.js file: %name', array('%name' => $tar_name)));
+          $this->rRmdir($content_path);
+          continue;
+        }
+
+        $content = json_decode($json);
+        if (!$content) {
+          $this->setErrorMessage($this->t('Invalid index.js file format: %name', array('%name' => $tar_name)));
+          $this->rRmdir($content_path);
+          continue;
+        }
+
+        if ($content->type != H5P_CONTENT && $content->type != H5P_LIBRARY) {
+          $this->setErrorMessage($this->t('Invalid content type: %name', array('%name' => $tar_name)));
+          $this->rRmdir($content_path);
+          continue;
+        }
+
+        if ($content->type == H5P_CONTENT) {
+          if (!isset($content->options)) {
+            $this->setErrorMessage($this->t('Missing start options: %name', array('%name' => $tar_name)));
+            $this->rRmdir($content_path);
+            continue;
+          }
+          if (!isset($content->class)) {
+            $this->setErrorMessage($this->t('Missing start class: %name', array('%name' => $tar_name)));
+            $this->rRmdir($content_path);
+            continue;
+          }
+          if (preg_match('/^[A-Z][A-Za-z0-9]*$/', $content->class)) {
+            $this->setErrorMessage($this->t('Invalid class name: %name', array('%name' => $content->class)));
+            $this->rRmdir($content_path);
+            continue;
+          }
+          $content->options = json_encode($content->options);
+        }
+        else {
+          if (!isset($content->js) || !empty($content->js)) {
+            $this->setErrorMessage($this->t('Library without any JS files: %name', array('%name' => $tar_name)));
+            $this->rRmdir($content_path);
+            continue;
+          }
+
+          // Check if JS files exist.
+          for ($j = 0, $l = count($content->js); $j < $l; $j++) {
+            $content->js[$j] = str_replace(array('/', '\\'), DIRECTORY_SEPARATOR, $content->js[$j]);
+            if (!file_exists($content_path . DIRECTORY_SEPARATOR . $content->js[$j])) {
+              $this->setErrorMessage($this->t('The JS file %file is missing from library: %name', array('%file' => $content->js[$j], '%name' => $tar_name)));
+              $this->rRmdir($content_path);
+              continue;
+            }
+          }
+
+          // Check if CSS files exist.
+          for ($j = 0, $l = count($content->css); $j < $l; $j++) {
+            $content->css[$j] = str_replace(array('/', '\\'), DIRECTORY_SEPARATOR, $content->css[$j]);
+            if (!file_exists($content_path . DIRECTORY_SEPARATOR . $content->css[$j])) {
+              $this->setErrorMessage($this->t('The CSS file %file is missing from library: %name', array('%file' => $content->css[$j], '%name' => $tar_name)));
+              $this->rRmdir($content_path);
+              continue;
+            }
+          }
+        }
+
+        $content->id = $tar_id;
+        $content->name = $tar_name;
+        $content->time = $tar_time;
+
+        $contents[$content->id] = $content;
+      }
+    }
+    
+
+    $this->rRmdir($tmp_dir);
+
+    foreach ($contents as &$content) {
+      if ($content->type == H5P_CONTENT) {
+        // Check dependencies for content
+        $name = strtolower(preg_replace('/.+([A-Z])/', '-$0', $content->class));
+        $missing_dependencies = h5p_find_missing_dependencies($contents, $name);
+        if ($missing_dependencies) {
+          $this->setErrorMessage($this->t('%name is missing the following dependencies: %dependencies', array('%name' => $content->name, '%dependencies' => implode(',', $missing_dependencies))));
+        }
+        else {
+          // TODO: Insert stuff?
+          // TODO: Insert into database
+          // TODO: Insert all files into files table.
+        }
+      }
+    }
+
+    // TODO: rmdir for libraries that doesn't have db records.
+  }
+
+  /**
+   * Recursive function for removing directories.
+   *
+   * @param string $dir Directory.
+   * @return boolean Indicates if the directory existed.
+   */
+  private function rRmdir($dir) {
+     if (is_dir($dir)) {
+       $files = scandir($dir);
+       for ($i = 2, $s = count($files); $i < $s; $i++) {
+         $file = $dir . DIRECTORY_SEPARATOR . $files[$i];
+         if (!$this->rRmdir($file)) {
+           unlink($file);
+         }
+       }
+       rmdir($dir);
+       return TRUE;
+     }
+     else {
+       return FALSE;
+     }
   }
 }
 ?>