<?php // $Id: database.lib.php 15361 2008-05-22 18:25:31Z yannoo $
/* See license terms in /dokeos_license.txt */
/**
==============================================================================
*	This is the main database library for Dokeos.
*	Include/require it in your code to use its functionality.
*   Because this library contains all the basic database calls, it could be
*   replaced by another library for say, PostgreSQL, to actually use Dokeos
*   with another database (this is not ready yet because a lot of code still
*   uses the MySQL database functions extensively).
*
*	@package dokeos.library
* 	@todo the table constants have all to start with TABLE_
* 		  This is because of the analogy with the tool constants TOOL_
==============================================================================
*/
/*
==============================================================================
		CONSTANTS
==============================================================================
*/
//main database tables
define('TABLE_MAIN_COURSE', 'course');
define('TABLE_MAIN_USER', 'user');
define('TABLE_MAIN_CLASS', 'class');
define('TABLE_MAIN_ADMIN', 'admin');
define('TABLE_MAIN_COURSE_CLASS', 'course_rel_class');
define('TABLE_MAIN_COURSE_USER', 'course_rel_user');
define('TABLE_MAIN_CLASS_USER', 'class_user');
define('TABLE_MAIN_CATEGORY', 'course_category');
define('TABLE_MAIN_COURSE_MODULE', 'course_module');
define('TABLE_MAIN_SYSTEM_ANNOUNCEMENTS', 'sys_announcement');
define('TABLE_MAIN_LANGUAGE', 'language');
define('TABLE_MAIN_SETTINGS_OPTIONS', 'settings_options');
define('TABLE_MAIN_SETTINGS_CURRENT', 'settings_current');
define('TABLE_MAIN_SESSION', 'session');
define('TABLE_MAIN_SESSION_COURSE', 'session_rel_course');
define('TABLE_MAIN_SESSION_USER', 'session_rel_user');
define('TABLE_MAIN_SESSION_CLASS', 'session_rel_class');
define('TABLE_MAIN_SESSION_COURSE_USER', 'session_rel_course_rel_user');
define('TABLE_MAIN_SHARED_SURVEY', 'shared_survey');
define('TABLE_MAIN_SHARED_SURVEY_QUESTION', 'shared_survey_question');
define('TABLE_MAIN_SHARED_SURVEY_QUESTION_OPTION', 'shared_survey_question_option');
define('TABLE_MAIN_TEMPLATES', 'templates');
define('TABLE_MAIN_OPENID_ASSOCIATION','openid_association');
define('TABLE_MAIN_GRADEBOOK_CATEGORY', 	'gradebook_category');
define('TABLE_MAIN_GRADEBOOK_EVALUATION', 	'gradebook_evaluation');
define('TABLE_MAIN_GRADEBOOK_RESULT', 		'gradebook_result');
define('TABLE_MAIN_GRADEBOOK_LINK', 		'gradebook_link');
define('TABLE_MAIN_GRADEBOOK_SCORE_DISPLAY','gradebook_score_display');
define('TABLE_MAIN_USER_FIELD',			'user_field');
define('TABLE_MAIN_USER_FIELD_OPTIONS',	'user_field_options');
define('TABLE_MAIN_USER_FIELD_VALUES',	'user_field_values');
define('TABLE_MAIN_ACCESS_URL', 'access_url');

//statistic database tables
define('TABLE_STATISTIC_TRACK_E_LASTACCESS', 'track_e_lastaccess');
define('TABLE_STATISTIC_TRACK_E_ACCESS', 'track_e_access');
define('TABLE_STATISTIC_TRACK_E_LOGIN', 'track_e_login');
define('TABLE_STATISTIC_TRACK_E_DOWNLOADS', 'track_e_downloads');
define('TABLE_STATISTIC_TRACK_E_LINKS', 'track_e_links');
define('TABLE_STATISTIC_TRACK_E_ONLINE', 'track_e_online');
define('TABLE_STATISTIC_TRACK_E_HOTPOTATOES', 'track_e_hotpotatoes');
define('TABLE_STATISTIC_TRACK_E_COURSE_ACCESS', 'track_e_course_access');
define('TABLE_STATISTIC_TRACK_E_EXERCICES', 'track_e_exercices');
define('TABLE_STATISTIC_TRACK_E_ATTEMPT', 'track_e_attempt');
define('TABLE_STATISTIC_TRACK_E_DEFAULT', 'track_e_default');
define('TABLE_STATISTIC_TRACK_E_UPLOADS','track_e_uploads');
define('TABLE_STATISTIC_TRACK_E_HOTSPOT','track_e_hotspot');

//scorm database tables
define('TABLE_SCORM_MAIN', 'scorm_main');
define('TABLE_SCORM_SCO_DATA', 'scorm_sco_data');

//course tables
define('TABLE_AGENDA', 'calendar_event');
define('TABLE_AGENDA_REPEAT', 'calendar_event_repeat');
define('TABLE_AGENDA_REPEAT_NOT', 'calendar_event_repeat_not');
define('TABLE_ANNOUNCEMENT', 'announcement');
define('TABLE_CHAT_CONNECTED', 'chat_connected'); // @todo: probably no longer in use !!!
define('TABLE_COURSE_DESCRIPTION', 'course_description');
define('TABLE_DOCUMENT', 'document');
define('TABLE_ITEM_PROPERTY', 'item_property');
define('TABLE_LINK', 'link');
define('TABLE_LINK_CATEGORY', 'link_category');
define('TABLE_TOOL_LIST', 'tool');
define('TABLE_TOOL_INTRO', 'tool_intro');
define('TABLE_SCORMDOC', 'scormdocument');
define('TABLE_STUDENT_PUBLICATION', 'student_publication');
define('CHAT_CONNECTED_TABLE', 'chat_connected');

//course forum tables
define('TABLE_FORUM_CATEGORY','forum_category');
define('TABLE_FORUM','forum_forum');
define('TABLE_FORUM_THREAD','forum_thread');
define('TABLE_FORUM_POST','forum_post');
define('TABLE_FORUM_ATTACHMENT','forum_attachment');
//course group tables
define('TABLE_GROUP', 'group_info');
define('TABLE_GROUP_USER', 'group_rel_user');
define('TABLE_GROUP_TUTOR', 'group_rel_tutor');
define('TABLE_GROUP_CATEGORY', 'group_category');
//course dropbox tables
define('TABLE_DROPBOX_CATEGORY','dropbox_category');
define('TABLE_DROPBOX_FEEDBACK','dropbox_feedback');
define('TABLE_DROPBOX_POST','dropbox_post');
define('TABLE_DROPBOX_FILE','dropbox_file');
define('TABLE_DROPBOX_PERSON','dropbox_person');
//course quiz tables
define('TABLE_QUIZ_QUESTION', 'quiz_question');
define('TABLE_QUIZ_TEST', 'quiz');
define('TABLE_QUIZ_ANSWER', 'quiz_answer');
define('TABLE_QUIZ_TEST_QUESTION', 'quiz_rel_question');
//linked resource table
define('TABLE_LINKED_RESOURCES', 'resource');
//learnpath tables
define('TABLE_LEARNPATH_MAIN', 'learnpath_main');
define('TABLE_LEARNPATH_CHAPTER', 'learnpath_chapter');
define('TABLE_LEARNPATH_ITEM', 'learnpath_item');
define('TABLE_LEARNPATH_USER', 'learnpath_user');
//new scorm tables
define('TABLE_LP_MAIN', 'lp');
define('TABLE_LP_ITEM', 'lp_item');
define('TABLE_LP_VIEW', 'lp_view');
define('TABLE_LP_ITEM_VIEW', 'lp_item_view');
define('TABLE_LP_IV_INTERACTION', 'lp_iv_interaction'); // IV = Item View
// Smartblogs (Kevin Van Den Haute::kevin@develop-it.be)
// permission tables
define('TABLE_PERMISSION_USER', 'permission_user');
define('TABLE_PERMISSION_TASK', 'permission_task');
define('TABLE_PERMISSION_GROUP', 'permission_group');
// roles tables
define('TABLE_ROLE', 'role');
define('TABLE_ROLE_PERMISSION', 'role_permissions');
define('TABLE_ROLE_USER', 'role_user');
define('TABLE_ROLE_GROUP', 'role_group');
// blogs tables
define('TABLE_BLOGS', 'blog');
define('TABLE_BLOGS_POSTS', 'blog_post');
define('TABLE_BLOGS_COMMENTS', 'blog_comment');
define('TABLE_BLOGS_REL_USER', 'blog_rel_user');
define('TABLE_BLOGS_TASKS', 'blog_task');
define('TABLE_BLOGS_TASKS_REL_USER', 'blog_task_rel_user');
define('TABLE_BLOGS_RATING', 'blog_rating');
define('TABLE_BLOGS_ATTACHMENT', 'blog_attachment');
define('TABLE_BLOGS_TASKS_PERMISSIONS', 'permission_task');
//end of Smartblogs
// user information tables
define('TABLE_USER_INFO', 'userinfo_def');
define('TABLE_USER_INFO_CONTENT', 'userinfo_content');
// course settings table
define('TABLE_COURSE_SETTING', 'course_setting');
// course online tables
define('TABLE_ONLINE_LINK', 'online_link');
define('TABLE_ONLINE_CONNECTED', 'online_connected');
// dokeos_user database
define('TABLE_PERSONAL_AGENDA', 'personal_agenda');
define('TABLE_PERSONAL_AGENDA_REPEAT', 'personal_agenda_repeat');
define('TABLE_PERSONAL_AGENDA_REPEAT_NOT', 'personal_agenda_repeat_not');
define('TABLE_USER_COURSE_CATEGORY', 'user_course_category');
//Survey
// @todo: are these MAIN tables or course tables ?
define('TABLE_MAIN_SURVEY', 'survey');
define('TABLE_MAIN_GROUP', 'survey_group');
define('TABLE_MAIN_SURVEYQUESTION', 'questions');
// SURVEY
define('TABLE_SURVEY', 'survey');
define('TABLE_SURVEY_QUESTION', 'survey_question');
define('TABLE_SURVEY_QUESTION_OPTION', 'survey_question_option');
define('TABLE_SURVEY_INVITATION', 'survey_invitation');
define('TABLE_SURVEY_ANSWER', 'survey_answer');


/*
==============================================================================
		DATABASE CLASS
		the class and its functions
==============================================================================
*/
/**
 *	@package dokeos.library
 */
class Database
{
	/*
	-----------------------------------------------------------------------------
		Accessor Functions
		Usually, you won't need these directly but instead
		rely on of the get_xxx_table functions.
	-----------------------------------------------------------------------------
	*/
	/**
	 *	Returns the name of the main Dokeos database.
	 */
	function get_main_database()
	{
		global $_configuration;
		return $_configuration['main_database'];
	}
	/**
	*	Returns the name of the Dokeos statistics database.
	*/
	function get_statistic_database()
	{
		global $_configuration;
		return $_configuration['statistics_database'];
	}
	/**
	*	Returns the name of the Dokeos SCORM database.
	*/
	function get_scorm_database()
	{
		global $_configuration;
		return $_configuration['scorm_database'];
	}
	/**
	*	Returns the name of the database where all the personal stuff of the user is stored
	*/
	function get_user_personal_database()
	{
		global $_configuration;
		return $_configuration['user_personal_database'];
	}
	/**
	*	Returns the name of the main Dokeos database.
	*/
	function get_current_course_database()
	{
		$course_info = api_get_course_info();
		return $course_info["dbName"];
	}
	/**
	*	Returns the glued name of the current course database.
	*/
	function get_current_course_glued_database()
	{
		$course_info = api_get_course_info();
		return $course_info["dbNameGlu"];
	}
	/**
	*	The glue is the string needed between database and table.
	*	The trick is: in multiple databases, this is a period (with backticks)
	*	In single database, this can be e.g. an underscore so we just fake
	*	there are multiple databases and the code can be written independent
	*	of the single / multiple database setting.
	*/
	function get_database_glue()
	{
		global $_configuration;
		return $_configuration['db_glue'];
	}
	/**
	*	Returns the database prefix.
	*	All created COURSE databases are prefixed with this string.
	*
	*	TIP: this can be convenient e.g. if you have multiple Dokeos installations
	*	on the same physical server.
	*/
	function get_database_name_prefix()
	{
		global $_configuration;
		return $_configuration['db_prefix'];
	}
	/**
	*	Returns the course table prefix for single database.
	*	Not certain exactly when this is used.
	*	Do research.
	*	It's used in local.inc.php.
	*/
	function get_course_table_prefix()
	{
		global $_configuration;
		return $_configuration['table_prefix'];
	}
	/*
	-----------------------------------------------------------------------------
		Table Name functions
		use these functions to get a table name for queries,
		instead of constructing them yourself.

		Backticks automatically surround the result,
		e.g. `COURSE_NAME`.`link`
		so the queries can look cleaner.

		Example:
		$table = Database::get_course_table(TABLE_DOCUMENT);
		$sql_query = "SELECT * FROM $table WHERE $condition";
		$sql_result = api_sql_query($sql_query,__FILE__,__LINE__);
		$result = mysql_fetch_array($sql_result);
	-----------------------------------------------------------------------------
	*/
	/**
	 * A more generic function than the other get_main_xxx_table functions,
	 * this one can return the correct complete name of any table of the main database of which you pass
	 * the short name as a parameter.
	 * Please define table names as constants in this library and use them
	 * instead of directly using magic words in your tool code.
	 *
	 * @param string $short_table_name, the name of the table
	 */
	function get_main_table($short_table_name)
	{
		$database = Database::get_main_database();
		return Database::format_table_name($database, $short_table_name);
	}
	/**
	 * A more generic function than the older get_course_xxx_table functions,
	 * this one can return the correct complete name of any course table of which you pass
	 * the short name as a parameter.
	 * Please define table names as constants in this library and use them
	 * instead of directly using magic words in your tool code.
	 *
	 * @param string $short_table_name, the name of the table
	 * @param string $database_name, optional, name of the course database
	 * - if you don't specify this, you work on the current course.
	 */
	function get_course_table($short_table_name, $database_name = '')
	{
		$database_name_with_glue = Database::fix_database_parameter($database_name);
		return Database::format_glued_course_table_name($database_name_with_glue, $short_table_name);
	}
	/**
	 * This generic function returns the correct and complete name of any statistic table
	 * of which you pass the short name as a parameter.
	 * Please define table names as constants in this library and use them
	 * instead of directly using magic words in your tool code.
	 *
	 * @param string $short_table_name, the name of the table
	 */
	function get_statistic_table($short_table_name)
	{
		$database = Database::get_statistic_database();
		return Database::format_table_name($database, $short_table_name);
	}
	/**
	 * This generic function returns the correct and complete name of any scorm
	 * table of which you pass the short name as a parameter. Please define
	 * table names as constants in this library and use them instead of directly
	 * using magic words in your tool code.
	 *
	 * @param string $short_table_name, the name of the table
	 */
	function get_scorm_table($short_table_name)
	{
		$database = Database::get_scorm_database();
		return Database::format_table_name($database, $short_table_name);
	}
	/**
	 * This generic function returns the correct and complete name of any scorm
	 * table of which you pass the short name as a parameter. Please define
	 * table names as constants in this library and use them instead of directly
	 * using magic words in your tool code.
	 *
	 * @param string $short_table_name, the name of the table
	 */
	function get_user_personal_table($short_table_name)
	{
		$database = Database::get_user_personal_database();
		return Database::format_table_name($database, $short_table_name);
	}
	/**
	*	Returns the isocode corresponding to the language directory given.
	*/
	function get_language_isocode($lang_folder)
	{
		$table = Database::get_main_table(TABLE_MAIN_LANGUAGE);
		$sql_query = "SELECT isocode FROM $table WHERE dokeos_folder = '$lang_folder'";
		$sql_result = api_sql_query($sql_query, __FILE__, __LINE__);
		$result = mysql_fetch_array($sql_result);
		$result = $result['isocode'];
		return $result;
	}

	/*
	-----------------------------------------------------------------------------
		Query Functions
		these execute a query and return the result(s).
	-----------------------------------------------------------------------------
	*/

	/**
	*	@return a list (array) of all courses.
	* 	@todo shouldn't this be in the course.lib.php script?
	*/
	function get_course_list()
	{
		$table = Database::get_main_table(TABLE_MAIN_COURSE);
		$sql_query = "SELECT * FROM $table";
		$sql_result = api_sql_query($sql_query, __FILE__, __LINE__);
		$result = api_store_result($sql_result);
		return $result;
	}

	/**
	*	Returns an array with all database fields for the specified course.
	*
	*	@param the real (system) code of the course (ID from inside the main course table)
	* 	@todo shouldn't this be in the course.lib.php script?
	*/
	function get_course_info($course_code)
	{
		$table = Database::get_main_table(TABLE_MAIN_COURSE);
		$sql_query = "SELECT * FROM $table WHERE `code` = '$course_code'";
		$sql_result = api_sql_query($sql_query, __FILE__, __LINE__);
		$result = mysql_fetch_array($sql_result);
		$result = Database::generate_abstract_course_field_names($result);
		return $result;
	}
	/**
	*	@param $user_id (integer): the id of the user
	*	@return $user_info (array): user_id, lastname, firstname, username, email, ...
	*	@author Patrick Cool <patrick.cool@UGent.be>, expanded to get info for any user
	*	@author Roan Embrechts, first version + converted to Database API
	*	@version 30 September 2004
	*	@desc find all the information about a specified user. Without parameter this is the current user.
	* 	@todo shouldn't this be in the user.lib.php script?
	*/
	function get_user_info_from_id($user_id = '')
	{
		$table = Database::get_main_table(TABLE_MAIN_USER);
		if ($user_id == '')
		{
			return $GLOBALS["_user"];
		}
		else
		{
			$sql_query = "SELECT * FROM $table WHERE `user_id` = '$user_id'";
			$result = api_sql_query($sql_query, __FILE__, __LINE__);
			$result_array = mysql_fetch_array($result);
			$result_array = Database::generate_abstract_user_field_names($result_array);
			return $result_array;
		}
	}
	/**
	*	This creates an abstraction layer between database field names
	*	and field names expected in code.
	*
	*	This helps when changing database names.
	*	It's also useful now to get rid of the 'franglais'.
	*
	*	@todo	add more array entries to abstract course info from field names
	*	@author	Roan Embrechts
	*
	* 	@todo what's the use of this function. I think this is better removed.
	* 		  There should be consistency in the variable names and the use throughout the scripts
	* 		  for the database name we should consistently use or db_name or database (db_name probably being the better one)
	*/
	function generate_abstract_course_field_names($result_array)
	{
		$result_array["official_code"] = $result_array["visual_code"];
		$result_array["visual_code"] = $result_array["visual_code"];
		$result_array["real_code"] = $result_array["code"];
		$result_array["system_code"] = $result_array["code"];
		$result_array["title"] = $result_array['title'];
		$result_array["database"] = $result_array["db_name"];
		$result_array["faculty"] = $result_array["category_code"];
		//$result_array["directory"] = $result_array["directory"];
		/*
		still to do: (info taken from local.inc.php)

		$_course['id'          ]         = $cData['cours_id'         ]; //auto-assigned integer
		$_course['name'        ]         = $cData['title'            ];
		$_course['official_code']        = $cData['visual_code'        ]; // use in echo
		$_course['sysCode'     ]         = $cData['code'             ]; // use as key in db
		$_course['path'        ]         = $cData['directory'        ]; // use as key in path
		$_course['dbName'      ]         = $cData['db_name'           ]; // use as key in db list
		$_course['dbNameGlu'   ]         = $_configuration['table_prefix'] . $cData['dbName'] . $_configuration['db_glue']; // use in all queries
		$_course['titular'     ]         = $cData['tutor_name'       ];
		$_course['language'    ]         = $cData['course_language'   ];
		$_course['extLink'     ]['url' ] = $cData['department_url'    ];
		$_course['extLink'     ]['name'] = $cData['department_name'];
		$_course['categoryCode']         = $cData['faCode'           ];
		$_course['categoryName']         = $cData['faName'           ];

		$_course['visibility'  ]         = (bool) ($cData['visibility'] == 2 || $cData['visibility'] == 3);
		$_course['registrationAllowed']  = (bool) ($cData['visibility'] == 1 || $cData['visibility'] == 2);
		*/
		return $result_array;
	}
	/**
	*	This creates an abstraction layer between database field names
	*	and field names expected in code.
	*
	*	This helps when changing database names.
	*	It's also useful now to get rid of the 'franglais'.
	*
	*	@todo add more array entries to abstract user info from field names
	*	@author Roan Embrechts
	*	@author Patrick Cool
	*
	* 	@todo what's the use of this function. I think this is better removed.
	* 		  There should be consistency in the variable names and the use throughout the scripts
	*/
	function generate_abstract_user_field_names($result_array)
	{
		$result_array['firstName'] 		= $result_array['firstname'];
		$result_array['lastName'] 		= $result_array['lastname'];
		$result_array['mail'] 			= $result_array['email'];
		#$result_array['picture_uri'] 	= $result_array['picture_uri'];
		#$result_array ['user_id'  ] 	= $result_array['user_id'   ];
		return $result_array;
	}


	/*
	-----------------------------------------------------------------------------
		Private Functions
		You should not access these from outside the class
		No effort is made to keep the names / results the same.
	-----------------------------------------------------------------------------
	*/
	/**
	*	Glues a course database.
	*	glue format from local.inc.php.
	*/
	function glue_course_database_name($database_name)
	{
		$prefix = Database::get_course_table_prefix();
		$glue = Database::get_database_glue();
		$database_name_with_glue = $prefix.$database_name.$glue;
		return $database_name_with_glue;
	}
	/**
	*	@param string $database_name, can be empty to use current course db
	*
	*	@return the glued parameter if it is not empty,
	*	or the current course database (glued) if the parameter is empty.
	*/
	function fix_database_parameter($database_name)
	{
		if ($database_name == '')
		{
			$course_info = api_get_course_info();
			$database_name_with_glue = $course_info["dbNameGlu"];
		}
		else
		{
			$database_name_with_glue = Database::glue_course_database_name($database_name);
		}
		return $database_name_with_glue;
	}
	/**
	*	Structures a course database and table name to ready them
	*	for querying. The course database parameter is considered glued:
	*	e.g. COURSE001`.`
	*/
	function format_glued_course_table_name($database_name_with_glue, $table)
	{
		//$course_info = api_get_course_info();
		return "`".$database_name_with_glue.$table."`";
	}
	/**
	*	Structures a database and table name to ready them
	*	for querying. The database parameter is considered not glued,
	*	just plain e.g. COURSE001
	*/
	function format_table_name($database, $table)
	{
		return "`".$database."`.`".$table."`";
	}
	/**
	 * Count the number of rows in a table
	 * @param string $table The table of which the rows should be counted
	 * @return int The number of rows in the given table.
	 */
	function count_rows($table)
	{
		$sql = "SELECT COUNT(*) AS n FROM $table";
		$res = api_sql_query($sql, __FILE__, __LINE__);
		$obj = mysql_fetch_object($res);
		return $obj->n;
	}
	/**
	 * Gets the ID of the last item inserted into the database
	 *
	 * @author Yannick Warnier <yannick.warnier@dokeos.com>
	 * @return integer The last ID as returned by the DB function
	 * @comment This should be updated to use ADODB at some point
	 */
	function get_last_insert_id()
	{
		return mysql_insert_id();
	}
	/**
	 * Escapes a string to insert into the database as text
	 * @param	string	The string to escape
	 * @return	string	The escaped string
	 * @author	Yannick Warnier <yannick.warnier@dokeos.com>
	 * @author  Patrick Cool <patrick.cool@UGent.be>, Ghent University
	 */
	function escape_string($string)
	{
		if (get_magic_quotes_gpc())
		{
			$string = stripslashes($string);
		}
		return mysql_real_escape_string($string);
	}
	/**
	 * Gets the array from a SQL result (as returned by api_sql_query) - help achieving database independence
	 * @param     resource    The result from a call to sql_query (e.g. api_sql_query)
	 * @param     string      Optional: "ASSOC","NUM" or "BOTH", as the constant used in mysql_fetch_array.
	 * @return    array       Array of results as returned by php
	 * @author    Yannick Warnier <yannick.warnier@dokeos.com>
	 */
	function fetch_array($res, $option = 'BOTH')
	{
		if ($option != 'BOTH')
		{
			if ($option == 'ASSOC')
			{
				return mysql_fetch_array($res, MYSQL_ASSOC);
			}
			elseif ($option == 'NUM')
			{
				return mysql_fetch_array($res, MYSQL_NUM);
			}
		}
		else
		{
			return mysql_fetch_array($res);
		}
	}
	/**
	 * Gets the next row of the result of the SQL query (as returned by api_sql_query) in an object form
	 * @param	resource	The result from a call to sql_query (e.g. api_sql_query)
	 * @param	string		Optional class name to instanciate
	 * @param	array		Optional array of parameters
	 * @return	object		Object of class StdClass or the required class, containing the query result row
	 * @author	Yannick Warnier <yannick.warnier@dokeos.com>
	 */
	function fetch_object($res,$class=null,$params=null)
	{
		if(!empty($class))
		{
			if(is_array($params))
			{
				return mysql_fetch_object($res,$class,$params);
			}
			return mysql_fetch_object($res,$class);
		}
		return mysql_fetch_object($res);
	}
	/**
	 * Gets the array from a SQL result (as returned by api_sql_query) - help achieving database independence
	 * @param     resource    The result from a call to sql_query (e.g. api_sql_query)
	 * @return    array       Array of results as returned by php (mysql_fetch_row)
	 * @author    Yannick Warnier <yannick.warnier@dokeos.com>
	 */
	function fetch_row($res)
	{
		return mysql_fetch_row($res);
	}
	/**
	 * Gets the number of rows from the last query result - help achieving database independence
	 * @param   resource    The result
	 * @return  integer     The number of rows contained in this result
	 * @author  Yannick Warnier <yannick.warnier@dokeos.com>
	 **/
	function num_rows($res)
	{
		return mysql_num_rows($res);
	}

	function get_course_chat_connected_table($database_name = '')
	{
		$database_name_with_glue = Database::fix_database_parameter($database_name);
		return Database::format_glued_course_table_name($database_name_with_glue, CHAT_CONNECTED_TABLE);
	}
	/**
	 * Acts as the relative *_result() function of most DB drivers and fetches a
	 * specific line and a field
	 * @param	resource	The database resource to get data from
	 * @param	integer		The row number
	 * @param	string		Optional field name or number
	 * @result	mixed		One cell of the result, or FALSE on error
	 */
	function result($resource,$row,$field='')
	{
		if(!empty($field))
		{
			return mysql_result($resource,$row,$field);
		}
		else
		{
			return mysql_result($resource,$row);
		}
	}
	/**
	 * Recovers the last ID of any insert query executed over this SQL connection
	 * @return	integer	Unique ID of the latest inserted row
	 */
	function insert_id()
	{
		return mysql_insert_id();
	}
	/**
	 * Returns the number of affected rows
	 * @param	resource	Optional database resource
	 */
	function affected_rows($r=null)
	{
		if(isset($r))
		{
			return mysql_affected_rows($r);
		}
		else
		{
			return mysql_affected_rows();
		}
	}
	function query($sql,$file='',$line=0)
	{
		return 	api_sql_query($sql,$file,$line);
	}
    function error()
    {
    	return mysql_error();
    }
}
//end class Database
?>