<?php

require_once("Question.class.php");

class QuestionsFile
{
  private $filename;
  private $treeXML;
  private $root_node;

  public function __construct($filename)
  {
    $this->filename = $filename;
    $this->reload();
  }

  /**
   * Load or reload the questions file.
   * Unsave changes will be erased.
   */
  private function reload()
  {
    $this->treeXML = new DOMDocument('1.0', 'UTF-8');
    $this->treeXML->formatOutput   = true;

    if (@$this->treeXML->load($this->filename))
    {
      $root_nodes = $this->treeXML->getElementsByTagName("questions");
      if ($root_nodes->length > 0)
        $this->root_node = $root_nodes->item(0);
      else
        throw Exception("Not a valid nemubot QuestionsFile.");
    }
    else
    {
      $this->root_node = $this->treeXML->createElement("questions");
      $this->treeXML->appendChild($this->root_node);
    }
  }

  /**
   * Add a new question into the file
   * @param $question The question object
   */
  public function add_question($question)
  {
    $this->root_node->appendChild($question->to_xml($this->treeXML));
  }

  /**
   * Get a question from its unique identifiant
   */
  public function get_question($id)
  {
    return new Question($this->root_node->getElementById($id));
  }

  /**
   * Write changes into the real file
   */
  public function save($newfilename = null)
  {
    if (!empty($newfilename))
      $this->filename = $newfilename;

    $this->treeXML->save($this->filename);
  }
}

?>