<?php
/**
 * @package     Joomla.Platform
 * @subpackage  Application
 *
 * @copyright   Copyright (C) 2005 - 2012 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE
 */

defined('JPATH_PLATFORM') or die;

jimport('joomla.application.component.model');

/**
 * Model class for handling lists of items.
 *
 * @package     Joomla.Platform
 * @subpackage  Application
 * @since       11.1
 */
class JModelList extends JModel
{
	/**
	 * Internal memory based cache array of data.
	 *
	 * @var    array
	 * @since  11.1
	 */
	protected $cache = array();

	/**
	 * Context string for the model type.  This is used to handle uniqueness
	 * when dealing with the getStoreId() method and caching data structures.
	 *
	 * @var    string
	 * @since  11.1
	 */
	protected $context = null;

	/**
	 * Valid filter fields or ordering.
	 *
	 * @var    array
	 * @since  11.1
	 */
	protected $filter_fields = array();

	/**
	 * An internal cache for the last query used.
	 *
	 * @var    JDatabaseQuery
	 * @since  11.1
	 */
	protected $query = array();

	/**
	 * Constructor.
	 *
	 * @param   array  $config  An optional associative array of configuration settings.
	 *
	 * @see     JController
	 * @since   11.1
	 */
	public function __construct($config = array())
	{
		parent::__construct($config);

		// Add the ordering filtering fields white list.
		if (isset($config['filter_fields']))
		{
			$this->filter_fields = $config['filter_fields'];
		}

		// Guess the context as Option.ModelName.
		if (empty($this->context))
		{
			$this->context = strtolower($this->option . '.' . $this->getName());
		}
	}

	/**
	 * Method to cache the last query constructed.
	 *
	 * This method ensures that the query is constructed only once for a given state of the model.
	 *
	 * @return  JDatabaseQuery  A JDatabaseQuery object
	 *
	 * @since   11.1
	 */
	protected function _getListQuery()
	{
		// Capture the last store id used.
		static $lastStoreId;

		// Compute the current store id.
		$currentStoreId = $this->getStoreId();

		// If the last store id is different from the current, refresh the query.
		if ($lastStoreId != $currentStoreId || empty($this->query))
		{
			$lastStoreId = $currentStoreId;
			$this->query = $this->getListQuery();
		}

		return $this->query;
	}

	/**
	 * Method to get an array of data items.
	 *
	 * @return  mixed  An array of data items on success, false on failure.
	 *
	 * @since   11.1
	 */
	public function getItems()
	{
		// Get a storage key.
		$store = $this->getStoreId();

		// Try to load the data from internal storage.
		if (isset($this->cache[$store]))
		{
			return $this->cache[$store];
		}

		// Load the list items.
		$query = $this->_getListQuery();
		$items = $this->_getList($query, $this->getStart(), $this->getState('list.limit'));

		// Check for a database error.
		if ($this->_db->getErrorNum())
		{
			$this->setError($this->_db->getErrorMsg());
			return false;
		}

		// Add the items to the internal cache.
		$this->cache[$store] = $items;

		return $this->cache[$store];
	}

	/**
	 * Method to get a JDatabaseQuery object for retrieving the data set from a database.
	 *
	 * @return  JDatabaseQuery   A JDatabaseQuery object to retrieve the data set.
	 *
	 * @since   11.1
	 */
	protected function getListQuery()
	{
		$db = $this->getDbo();
		$query = $db->getQuery(true);

		return $query;
	}

	/**
	 * Method to get a JPagination object for the data set.
	 *
	 * @return  JPagination  A JPagination object for the data set.
	 *
	 * @since   11.1
	 */
	public function getPagination()
	{
		// Get a storage key.
		$store = $this->getStoreId('getPagination');

		// Try to load the data from internal storage.
		if (isset($this->cache[$store]))
		{
			return $this->cache[$store];
		}

		// Create the pagination object.
		jimport('joomla.html.pagination');
		$limit = (int) $this->getState('list.limit') - (int) $this->getState('list.links');
		$page = new JPagination($this->getTotal(), $this->getStart(), $limit);

		// Add the object to the internal cache.
		$this->cache[$store] = $page;

		return $this->cache[$store];
	}

	/**
	 * Method to get a store id based on the model configuration state.
	 *
	 * This is necessary because the model is used by the component and
	 * different modules that might need different sets of data or different
	 * ordering requirements.
	 *
	 * @param   string  $id  An identifier string to generate the store id.
	 *
	 * @return  string  A store id.
	 *
	 * @since   11.1
	 */
	protected function getStoreId($id = '')
	{
		// Add the list state to the store id.
		$id .= ':' . $this->getState('list.start');
		$id .= ':' . $this->getState('list.limit');
		$id .= ':' . $this->getState('list.ordering');
		$id .= ':' . $this->getState('list.direction');

		return md5($this->context . ':' . $id);
	}

	/**
	 * Method to get the total number of items for the data set.
	 *
	 * @return  integer  The total number of items available in the data set.
	 *
	 * @since   11.1
	 */
	public function getTotal()
	{
		// Get a storage key.
		$store = $this->getStoreId('getTotal');

		// Try to load the data from internal storage.
		if (isset($this->cache[$store]))
		{
			return $this->cache[$store];
		}

		// Load the total.
		$query = $this->_getListQuery();
		$total = (int) $this->_getListCount($query);

		// Check for a database error.
		if ($this->_db->getErrorNum())
		{
			$this->setError($this->_db->getErrorMsg());
			return false;
		}

		// Add the total to the internal cache.
		$this->cache[$store] = $total;

		return $this->cache[$store];
	}

	/**
	 * Method to get the starting number of items for the data set.
	 *
	 * @return  integer  The starting number of items available in the data set.
	 *
	 * @since   11.1
	 */
	public function getStart()
	{
		$store = $this->getStoreId('getstart');

		// Try to load the data from internal storage.
		if (isset($this->cache[$store]))
		{
			return $this->cache[$store];
		}

		$start = $this->getState('list.start');
		$limit = $this->getState('list.limit');
		$total = $this->getTotal();
		if ($start > $total - $limit)
		{
			$start = max(0, (int) (ceil($total / $limit) - 1) * $limit);
		}

		// Add the total to the internal cache.
		$this->cache[$store] = $start;

		return $this->cache[$store];
	}

	/**
	 * Method to auto-populate the model state.
	 *
	 * This method should only be called once per instantiation and is designed
	 * to be called on the first call to the getState() method unless the model
	 * configuration flag to ignore the request is set.
	 *
	 * Note. Calling getState in this method will result in recursion.
	 *
	 * @param   string  $ordering   An optional ordering field.
	 * @param   string  $direction  An optional direction (asc|desc).
	 *
	 * @return  void
	 *
	 * @since   11.1
	 */
	protected function populateState($ordering = null, $direction = null)
	{
		// If the context is set, assume that stateful lists are used.
		if ($this->context)
		{
			$app = JFactory::getApplication();

			$value = $app->getUserStateFromRequest('global.list.limit', 'limit', $app->getCfg('list_limit'), 'uint');
			$limit = $value;
			$this->setState('list.limit', $limit);

			$value = $app->getUserStateFromRequest($this->context . '.limitstart', 'limitstart', 0);
			$limitstart = ($limit != 0 ? (floor($value / $limit) * $limit) : 0);
			$this->setState('list.start', $limitstart);

			// Check if the ordering field is in the white list, otherwise use the incoming value.
			$value = $app->getUserStateFromRequest($this->context . '.ordercol', 'filter_order', $ordering);
			if (!in_array($value, $this->filter_fields))
			{
				$value = $ordering;
				$app->setUserState($this->context . '.ordercol', $value);
			}
			$this->setState('list.ordering', $value);

			// Check if the ordering direction is valid, otherwise use the incoming value.
			$value = $app->getUserStateFromRequest($this->context . '.orderdirn', 'filter_order_Dir', $direction);
			if (!in_array(strtoupper($value), array('ASC', 'DESC', '')))
			{
				$value = $direction;
				$app->setUserState($this->context . '.orderdirn', $value);
			}
			$this->setState('list.direction', $value);
		}
		else
		{
			$this->setState('list.start', 0);
			$this->state->set('list.limit', 0);
		}
	}

	/**
	 * Gets the value of a user state variable and sets it in the session
	 *
	 * This is the same as the method in JApplication except that this also can optionally
	 * force you back to the first page when a filter has changed
	 *
	 * @param   string   $key        The key of the user state variable.
	 * @param   string   $request    The name of the variable passed in a request.
	 * @param   string   $default    The default value for the variable if not found. Optional.
	 * @param   string   $type       Filter for the variable, for valid values see {@link JFilterInput::clean()}. Optional.
	 * @param   boolean  $resetPage  If true, the limitstart in request is set to zero
	 *
	 * @return  The request user state.
	 *
	 * @since   11.1
	 */
	public function getUserStateFromRequest($key, $request, $default = null, $type = 'none', $resetPage = true)
	{
		$app = JFactory::getApplication();
		$old_state = $app->getUserState($key);
		$cur_state = (!is_null($old_state)) ? $old_state : $default;
		$new_state = JRequest::getVar($request, null, 'default', $type);

		if (($cur_state != $new_state) && ($resetPage))
		{
			JRequest::setVar('limitstart', 0);
		}

		// Save the new value only if it is set in this request.
		if ($new_state !== null)
		{
			$app->setUserState($key, $new_state);
		}
		else
		{
			$new_state = $cur_state;
		}

		return $new_state;
	}
}
