3 files changed, 1000 insertions, 0 deletions
diff --git a/phpBB/phpbb/tree/nestedset.php b/phpBB/phpbb/tree/nestedset.php
new file mode 100644
index 0000000000..13184cf41c
--- /dev/null
+++ b/phpBB/phpbb/tree/nestedset.php
@@ -0,0 +1,844 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+namespace phpbb\tree;
+
+abstract class nestedset implements \phpbb\tree\tree_interface
+{
+	/** @var \phpbb\db\driver\driver */
+	protected $db;
+
+	/** @var \phpbb\lock\db */
+	protected $lock;
+
+	/** @var string */
+	protected $table_name;
+
+	/**
+	* Prefix for the language keys returned by exceptions
+	* @var string
+	*/
+	protected $message_prefix = '';
+
+	/**
+	* Column names in the table
+	* @var string
+	*/
+	protected $column_item_id = 'item_id';
+	protected $column_left_id = 'left_id';
+	protected $column_right_id = 'right_id';
+	protected $column_parent_id = 'parent_id';
+	protected $column_item_parents = 'item_parents';
+
+	/**
+	* Additional SQL restrictions
+	* Allows to have multiple nested sets in one table
+	* @var string
+	*/
+	protected $sql_where = '';
+
+	/**
+	* List of item properties to be cached in the item_parents column
+	* @var array
+	*/
+	protected $item_basic_data = array('*');
+
+	/**
+	* Construct
+	*
+	* @param \phpbb\db\driver\driver	$db		Database connection
+	* @param \phpbb\lock\db		$lock	Lock class used to lock the table when moving forums around
+	* @param string			$table_name			Table name
+	* @param string			$message_prefix		Prefix for the messages thrown by exceptions
+	* @param string			$sql_where			Additional SQL restrictions for the queries
+	* @param array			$item_basic_data	Array with basic item data that is stored in item_parents
+	* @param array			$columns			Array with column names to overwrite
+	*/
+	public function __construct(\phpbb\db\driver\driver $db, \phpbb\lock\db $lock, $table_name, $message_prefix = '', $sql_where = '', $item_basic_data = array(), $columns = array())
+	{
+		$this->db = $db;
+		$this->lock = $lock;
+
+		$this->table_name = $table_name;
+		$this->message_prefix = $message_prefix;
+		$this->sql_where = $sql_where;
+		$this->item_basic_data = (!empty($item_basic_data)) ? $item_basic_data : array('*');
+
+		if (!empty($columns))
+		{
+			foreach ($columns as $column => $name)
+			{
+				$column_name = 'column_' . $column;
+				$this->$column_name = $name;
+			}
+		}
+	}
+
+	/**
+	* Returns additional sql where restrictions
+	*
+	* @param string		$operator		SQL operator that needs to be prepended to sql_where,
+	*									if it is not empty.
+	* @param string		$column_prefix	Prefix that needs to be prepended to column names
+	* @return string		Returns additional where statements to narrow down the tree,
+	*						prefixed with operator and prepended column_prefix to column names
+	*/
+	public function get_sql_where($operator = 'AND', $column_prefix = '')
+	{
+		return (!$this->sql_where) ? '' : $operator . ' ' . sprintf($this->sql_where, $column_prefix);
+	}
+
+	/**
+	* Acquires a lock on the item table
+	*
+	* @return bool	True if the lock was acquired, false if it has been acquired previously
+	*
+	* @throws RuntimeException If the lock could not be acquired
+	*/
+	protected function acquire_lock()
+	{
+		if ($this->lock->owns_lock())
+		{
+			return false;
+		}
+
+		if (!$this->lock->acquire())
+		{
+			throw new \RuntimeException($this->message_prefix . 'LOCK_FAILED_ACQUIRE');
+		}
+
+		return true;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function insert(array $additional_data)
+	{
+		$item_data = $this->reset_nestedset_values($additional_data);
+
+		$sql = 'INSERT INTO ' . $this->table_name . ' ' . $this->db->sql_build_array('INSERT', $item_data);
+		$this->db->sql_query($sql);
+
+		$item_data[$this->column_item_id] = (int) $this->db->sql_nextid();
+
+		return array_merge($item_data, $this->add_item_to_nestedset($item_data[$this->column_item_id]));
+	}
+
+	/**
+	* Add an item which already has a database row at the end of the tree
+	*
+	* @param int	$item_id	The item to be added
+	* @return array		Array with updated data, if the item was added successfully
+	*					Empty array otherwise
+	*/
+	protected function add_item_to_nestedset($item_id)
+	{
+		$sql = 'SELECT MAX(' . $this->column_right_id . ') AS ' . $this->column_right_id . '
+			FROM ' . $this->table_name . '
+			' . $this->get_sql_where('WHERE');
+		$result = $this->db->sql_query($sql);
+		$current_max_right_id = (int) $this->db->sql_fetchfield($this->column_right_id);
+		$this->db->sql_freeresult($result);
+
+		$update_item_data = array(
+			$this->column_parent_id		=> 0,
+			$this->column_left_id		=> $current_max_right_id + 1,
+			$this->column_right_id		=> $current_max_right_id + 2,
+			$this->column_item_parents	=> '',
+		);
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->db->sql_build_array('UPDATE', $update_item_data) . '
+			WHERE ' . $this->column_item_id . ' = ' . (int) $item_id . '
+				AND ' . $this->column_parent_id . ' = 0
+				AND ' . $this->column_left_id . ' = 0
+				AND ' . $this->column_right_id . ' = 0';
+		$this->db->sql_query($sql);
+
+		return ($this->db->sql_affectedrows() == 1) ? $update_item_data : array();
+	}
+
+	/**
+	* Remove an item from the tree without deleting it from the database
+	*
+	* Also removes all subitems from the tree without deleting them from the database either
+	*
+	* @param int	$item_id	The item to be deleted
+	* @return array		Item ids that have been removed
+	*/
+	protected function remove_item_from_nestedset($item_id)
+	{
+		$item_id = (int) $item_id;
+		if (!$item_id)
+		{
+			throw new \OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$items = $this->get_subtree_data($item_id);
+		$item_ids = array_keys($items);
+
+		if (empty($items) || !isset($items[$item_id]))
+		{
+			throw new \OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$this->remove_subset($item_ids, $items[$item_id]);
+
+		return $item_ids;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function delete($item_id)
+	{
+		$removed_items = $this->remove_item_from_nestedset($item_id);
+
+		$sql = 'DELETE FROM ' . $this->table_name . '
+			WHERE ' . $this->db->sql_in_set($this->column_item_id, $removed_items) . '
+			' . $this->get_sql_where('AND');
+		$this->db->sql_query($sql);
+
+		return $removed_items;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function move($item_id, $delta)
+	{
+		if ($delta == 0)
+		{
+			return false;
+		}
+
+		$this->acquire_lock();
+
+		$action = ($delta > 0) ? 'move_up' : 'move_down';
+		$delta = abs($delta);
+
+		// Keep $this->get_sql_where() here, to ensure we are in the right tree.
+		$sql = 'SELECT *
+			FROM ' . $this->table_name . '
+			WHERE ' . $this->column_item_id . ' = ' . (int) $item_id . '
+				' . $this->get_sql_where();
+		$result = $this->db->sql_query_limit($sql, $delta);
+		$item = $this->db->sql_fetchrow($result);
+		$this->db->sql_freeresult($result);
+
+		if (!$item)
+		{
+			$this->lock->release();
+			throw new \OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		/**
+		* Fetch all the siblings between the item's current spot
+		* and where we want to move it to. If there are less than $delta
+		* siblings between the current spot and the target then the
+		* item will move as far as possible
+		*/
+		$sql = "SELECT {$this->column_item_id}, {$this->column_parent_id}, {$this->column_left_id}, {$this->column_right_id}, {$this->column_item_parents}
+			FROM " . $this->table_name . '
+			WHERE ' . $this->column_parent_id . ' = ' . (int) $item[$this->column_parent_id] . '
+				' . $this->get_sql_where() . '
+				AND ';
+
+		if ($action == 'move_up')
+		{
+			$sql .= $this->column_right_id . ' < ' . (int) $item[$this->column_right_id] . ' ORDER BY ' . $this->column_right_id . ' DESC';
+		}
+		else
+		{
+			$sql .= $this->column_left_id . ' > ' . (int) $item[$this->column_left_id] . ' ORDER BY ' . $this->column_left_id . ' ASC';
+		}
+
+		$result = $this->db->sql_query_limit($sql, $delta);
+
+		$target = false;
+		while ($row = $this->db->sql_fetchrow($result))
+		{
+			$target = $row;
+		}
+		$this->db->sql_freeresult($result);
+
+		if (!$target)
+		{
+			$this->lock->release();
+			// The item is already on top or bottom
+			return false;
+		}
+
+		/**
+		* $left_id and $right_id define the scope of the items that are affected by the move.
+		* $diff_up and $diff_down are the values to substract or add to each item's left_id
+		* and right_id in order to move them up or down.
+		* $move_up_left and $move_up_right define the scope of the items that are moving
+		* up. Other items in the scope of ($left_id, $right_id) are considered to move down.
+		*/
+		if ($action == 'move_up')
+		{
+			$left_id = (int) $target[$this->column_left_id];
+			$right_id = (int) $item[$this->column_right_id];
+
+			$diff_up = (int) $item[$this->column_left_id] - (int) $target[$this->column_left_id];
+			$diff_down = (int) $item[$this->column_right_id] + 1 - (int) $item[$this->column_left_id];
+
+			$move_up_left = (int) $item[$this->column_left_id];
+			$move_up_right = (int) $item[$this->column_right_id];
+		}
+		else
+		{
+			$left_id = (int) $item[$this->column_left_id];
+			$right_id = (int) $target[$this->column_right_id];
+
+			$diff_up = (int) $item[$this->column_right_id] + 1 - (int) $item[$this->column_left_id];
+			$diff_down = (int) $target[$this->column_right_id] - (int) $item[$this->column_right_id];
+
+			$move_up_left = (int) $item[$this->column_right_id] + 1;
+			$move_up_right = (int) $target[$this->column_right_id];
+		}
+
+		// Now do the dirty job
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->column_left_id . ' = ' . $this->column_left_id . ' + CASE
+				WHEN ' . $this->column_left_id . " BETWEEN {$move_up_left} AND {$move_up_right} THEN -{$diff_up}
+				ELSE {$diff_down}
+			END,
+			" . $this->column_right_id . ' = ' . $this->column_right_id . ' + CASE
+				WHEN ' . $this->column_right_id . " BETWEEN {$move_up_left} AND {$move_up_right} THEN -{$diff_up}
+				ELSE {$diff_down}
+			END
+			WHERE
+				" . $this->column_left_id . " BETWEEN {$left_id} AND {$right_id}
+				AND " . $this->column_right_id . " BETWEEN {$left_id} AND {$right_id}
+				" . $this->get_sql_where();
+		$this->db->sql_query($sql);
+
+		$this->lock->release();
+
+		return true;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function move_down($item_id)
+	{
+		return $this->move($item_id, -1);
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function move_up($item_id)
+	{
+		return $this->move($item_id, 1);
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function move_children($current_parent_id, $new_parent_id)
+	{
+		$current_parent_id = (int) $current_parent_id;
+		$new_parent_id = (int) $new_parent_id;
+
+		if ($current_parent_id == $new_parent_id)
+		{
+			return false;
+		}
+
+		if (!$current_parent_id)
+		{
+			throw new \OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$this->acquire_lock();
+
+		$item_data = $this->get_subtree_data($current_parent_id);
+		if (!isset($item_data[$current_parent_id]))
+		{
+			$this->lock->release();
+			throw new \OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$current_parent = $item_data[$current_parent_id];
+		unset($item_data[$current_parent_id]);
+		$move_items = array_keys($item_data);
+
+		if (($current_parent[$this->column_right_id] - $current_parent[$this->column_left_id]) <= 1)
+		{
+			$this->lock->release();
+			return false;
+		}
+
+		if (in_array($new_parent_id, $move_items))
+		{
+			$this->lock->release();
+			throw new \OutOfBoundsException($this->message_prefix . 'INVALID_PARENT');
+		}
+
+		$diff = sizeof($move_items) * 2;
+		$sql_exclude_moved_items = $this->db->sql_in_set($this->column_item_id, $move_items, true);
+
+		$this->db->sql_transaction('begin');
+
+		$this->remove_subset($move_items, $current_parent, false, true);
+
+		if ($new_parent_id)
+		{
+			// Retrieve new-parent again, it may have been changed...
+			$sql = 'SELECT *
+				FROM ' . $this->table_name . '
+				WHERE ' . $this->column_item_id . ' = ' . $new_parent_id;
+			$result = $this->db->sql_query($sql);
+			$new_parent = $this->db->sql_fetchrow($result);
+			$this->db->sql_freeresult($result);
+
+			if (!$new_parent)
+			{
+				$this->db->sql_transaction('rollback');
+				$this->lock->release();
+				throw new \OutOfBoundsException($this->message_prefix . 'INVALID_PARENT');
+			}
+
+			$new_right_id = $this->prepare_adding_subset($move_items, $new_parent, true);
+
+			if ($new_right_id > $current_parent[$this->column_right_id])
+			{
+				$diff = ' + ' . ($new_right_id - $current_parent[$this->column_right_id]);
+			}
+			else
+			{
+				$diff = ' - ' . abs($new_right_id - $current_parent[$this->column_right_id]);
+			}
+		}
+		else
+		{
+			$sql = 'SELECT MAX(' . $this->column_right_id . ') AS ' . $this->column_right_id . '
+				FROM ' . $this->table_name . '
+				WHERE ' . $sql_exclude_moved_items . '
+					' . $this->get_sql_where('AND');
+			$result = $this->db->sql_query($sql);
+			$row = $this->db->sql_fetchrow($result);
+			$this->db->sql_freeresult($result);
+
+			$diff = ' + ' . ($row[$this->column_right_id] - $current_parent[$this->column_left_id]);
+		}
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->column_left_id . ' = ' . $this->column_left_id . $diff . ',
+				' . $this->column_right_id . ' = ' . $this->column_right_id . $diff . ',
+				' . $this->column_parent_id . ' = ' . $this->db->sql_case($this->column_parent_id . ' = ' . $current_parent_id, $new_parent_id, $this->column_parent_id) . ',
+				' . $this->column_item_parents . " = ''
+			WHERE " . $this->db->sql_in_set($this->column_item_id, $move_items) . '
+				' . $this->get_sql_where('AND');
+		$this->db->sql_query($sql);
+
+		$this->db->sql_transaction('commit');
+		$this->lock->release();
+
+		return true;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function change_parent($item_id, $new_parent_id)
+	{
+		$item_id = (int) $item_id;
+		$new_parent_id = (int) $new_parent_id;
+
+		if ($item_id == $new_parent_id)
+		{
+			return false;
+		}
+
+		if (!$item_id)
+		{
+			throw new \OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$this->acquire_lock();
+
+		$item_data = $this->get_subtree_data($item_id);
+		if (!isset($item_data[$item_id]))
+		{
+			$this->lock->release();
+			throw new \OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$item = $item_data[$item_id];
+		$move_items = array_keys($item_data);
+
+		if (in_array($new_parent_id, $move_items))
+		{
+			$this->lock->release();
+			throw new \OutOfBoundsException($this->message_prefix . 'INVALID_PARENT');
+		}
+
+		$diff = sizeof($move_items) * 2;
+		$sql_exclude_moved_items = $this->db->sql_in_set($this->column_item_id, $move_items, true);
+
+		$this->db->sql_transaction('begin');
+
+		$this->remove_subset($move_items, $item, false, true);
+
+		if ($new_parent_id)
+		{
+			// Retrieve new-parent again, it may have been changed...
+			$sql = 'SELECT *
+				FROM ' . $this->table_name . '
+				WHERE ' . $this->column_item_id . ' = ' . $new_parent_id;
+			$result = $this->db->sql_query($sql);
+			$new_parent = $this->db->sql_fetchrow($result);
+			$this->db->sql_freeresult($result);
+
+			if (!$new_parent)
+			{
+				$this->db->sql_transaction('rollback');
+				$this->lock->release();
+				throw new \OutOfBoundsException($this->message_prefix . 'INVALID_PARENT');
+			}
+
+			$new_right_id = $this->prepare_adding_subset($move_items, $new_parent, true);
+
+			if ($new_right_id > (int) $item[$this->column_right_id])
+			{
+				$diff = ' + ' . ($new_right_id - (int) $item[$this->column_right_id] - 1);
+			}
+			else
+			{
+				$diff = ' - ' . abs($new_right_id - (int) $item[$this->column_right_id] - 1);
+			}
+		}
+		else
+		{
+			$sql = 'SELECT MAX(' . $this->column_right_id . ') AS ' . $this->column_right_id . '
+				FROM ' . $this->table_name . '
+				WHERE ' . $sql_exclude_moved_items . '
+					' . $this->get_sql_where('AND');
+			$result = $this->db->sql_query($sql);
+			$row = $this->db->sql_fetchrow($result);
+			$this->db->sql_freeresult($result);
+
+			$diff = ' + ' . ($row[$this->column_right_id] - (int) $item[$this->column_left_id] + 1);
+		}
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->column_left_id . ' = ' . $this->column_left_id . $diff . ',
+				' . $this->column_right_id . ' = ' . $this->column_right_id . $diff . ',
+				' . $this->column_parent_id . ' = ' . $this->db->sql_case($this->column_item_id . ' = ' . $item_id, $new_parent_id, $this->column_parent_id) . ',
+				' . $this->column_item_parents . " = ''
+			WHERE " . $this->db->sql_in_set($this->column_item_id, $move_items) . '
+				' . $this->get_sql_where('AND');
+		$this->db->sql_query($sql);
+
+		$this->db->sql_transaction('commit');
+		$this->lock->release();
+
+		return true;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function get_path_and_subtree_data($item_id, $order_asc = true, $include_item = true)
+	{
+		$condition = 'i2.' . $this->column_left_id . ' BETWEEN i1.' . $this->column_left_id . ' AND i1.' . $this->column_right_id . '
+			OR i1.' . $this->column_left_id . ' BETWEEN i2.' . $this->column_left_id . ' AND i2.' . $this->column_right_id;
+
+		return $this->get_set_of_nodes_data($item_id, $condition, $order_asc, $include_item);
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function get_path_data($item_id, $order_asc = true, $include_item = true)
+	{
+		$condition = 'i1.' . $this->column_left_id . ' BETWEEN i2.' . $this->column_left_id . ' AND i2.' . $this->column_right_id . '';
+
+		return $this->get_set_of_nodes_data($item_id, $condition, $order_asc, $include_item);
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function get_subtree_data($item_id, $order_asc = true, $include_item = true)
+	{
+		$condition = 'i2.' . $this->column_left_id . ' BETWEEN i1.' . $this->column_left_id . ' AND i1.' . $this->column_right_id . '';
+
+		return $this->get_set_of_nodes_data($item_id, $condition, $order_asc, $include_item);
+	}
+
+	/**
+	* Get items that are related to the given item by the condition
+	*
+	* @param int		$item_id		Id of the item to retrieve the node set from
+	* @param string		$condition		Query string restricting the item list
+	* @param bool		$order_asc		Order the items ascending by their left_id
+	* @param bool		$include_item	Should the item matching the given item id be included in the list as well
+	* @return array			Array of items (containing all columns from the item table)
+	*							ID => Item data
+	*/
+	protected function get_set_of_nodes_data($item_id, $condition, $order_asc = true, $include_item = true)
+	{
+		$rows = array();
+
+		$sql = 'SELECT i2.*
+			FROM ' . $this->table_name . ' i1
+			LEFT JOIN ' . $this->table_name . " i2
+				ON (($condition) " . $this->get_sql_where('AND', 'i2.') . ')
+			WHERE i1.' . $this->column_item_id . ' = ' . (int) $item_id . '
+				' . $this->get_sql_where('AND', 'i1.') . '
+			ORDER BY i2.' . $this->column_left_id . ' ' . ($order_asc ? 'ASC' : 'DESC');
+		$result = $this->db->sql_query($sql);
+
+		while ($row = $this->db->sql_fetchrow($result))
+		{
+			if (!$include_item && $item_id == $row[$this->column_item_id])
+			{
+				continue;
+			}
+
+			$rows[(int) $row[$this->column_item_id]] = $row;
+		}
+		$this->db->sql_freeresult($result);
+
+		return $rows;
+	}
+
+	/**
+	* Get basic data of all parent items
+	*
+	* Basic data is defined in the $item_basic_data property.
+	* Data is cached in the item_parents column in the item table
+	*
+	* @param array	$item		The item to get the path from
+	* @return array			Array of items (containing basic columns from the item table)
+	*							ID => Item data
+	*/
+	public function get_path_basic_data(array $item)
+	{
+		$parents = array();
+		if ($item[$this->column_parent_id])
+		{
+			if (!$item[$this->column_item_parents])
+			{
+				$sql = 'SELECT ' . implode(', ', $this->item_basic_data) . '
+					FROM ' . $this->table_name . '
+					WHERE ' . $this->column_left_id . ' < ' . (int) $item[$this->column_left_id] . '
+						AND ' . $this->column_right_id . ' > ' . (int) $item[$this->column_right_id] . '
+						' . $this->get_sql_where('AND') . '
+					ORDER BY ' . $this->column_left_id . ' ASC';
+				$result = $this->db->sql_query($sql);
+
+				while ($row = $this->db->sql_fetchrow($result))
+				{
+					$parents[$row[$this->column_item_id]] = $row;
+				}
+				$this->db->sql_freeresult($result);
+
+				$item_parents = serialize($parents);
+
+				$sql = 'UPDATE ' . $this->table_name . '
+					SET ' . $this->column_item_parents . " = '" . $this->db->sql_escape($item_parents) . "'
+					WHERE " . $this->column_parent_id . ' = ' . (int) $item[$this->column_parent_id];
+				$this->db->sql_query($sql);
+			}
+			else
+			{
+				$parents = unserialize($item[$this->column_item_parents]);
+			}
+		}
+
+		return $parents;
+	}
+
+	/**
+	* Remove a subset from the nested set
+	*
+	* @param array	$subset_items		Subset of items to remove
+	* @param array	$bounding_item		Item containing the right bound of the subset
+	* @param bool	$set_subset_zero	Should the parent, left and right id of the items be set to 0, or kept unchanged?
+	*									In case of removing an item from the tree, we should the values to 0
+	*									In case of moving an item, we shouldkeep the original values, in order to allow "+ diff" later
+	* @return	null
+	*/
+	protected function remove_subset(array $subset_items, array $bounding_item, $set_subset_zero = true)
+	{
+		$acquired_new_lock = $this->acquire_lock();
+
+		$diff = sizeof($subset_items) * 2;
+		$sql_subset_items = $this->db->sql_in_set($this->column_item_id, $subset_items);
+		$sql_not_subset_items = $this->db->sql_in_set($this->column_item_id, $subset_items, true);
+
+		$sql_is_parent = $this->column_left_id . ' <= ' . (int) $bounding_item[$this->column_right_id] . '
+			AND ' . $this->column_right_id . ' >= ' . (int) $bounding_item[$this->column_right_id];
+
+		$sql_is_right = $this->column_left_id . ' > ' . (int) $bounding_item[$this->column_right_id];
+
+		$set_left_id = $this->db->sql_case($sql_is_right, $this->column_left_id . ' - ' . $diff, $this->column_left_id);
+		$set_right_id = $this->db->sql_case($sql_is_parent . ' OR ' . $sql_is_right, $this->column_right_id . ' - ' . $diff, $this->column_right_id);
+
+		if ($set_subset_zero)
+		{
+			$set_left_id = $this->db->sql_case($sql_subset_items, 0, $set_left_id);
+			$set_right_id = $this->db->sql_case($sql_subset_items, 0, $set_right_id);
+		}
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . (($set_subset_zero) ? $this->column_parent_id . ' = ' . $this->db->sql_case($sql_subset_items, 0, $this->column_parent_id) . ',' : '') . '
+				' . $this->column_left_id . ' = ' . $set_left_id . ',
+				' . $this->column_right_id . ' = ' . $set_right_id . '
+			' . ((!$set_subset_zero) ? ' WHERE ' . $sql_not_subset_items . ' ' . $this->get_sql_where('AND') : $this->get_sql_where('WHERE'));
+		$this->db->sql_query($sql);
+
+		if ($acquired_new_lock)
+		{
+			$this->lock->release();
+		}
+	}
+
+	/**
+	* Prepare adding a subset to the nested set
+	*
+	* @param array	$subset_items		Subset of items to add
+	* @param array	$new_parent	Item containing the right bound of the new parent
+	* @return	int		New right id of the parent item
+	*/
+	protected function prepare_adding_subset(array $subset_items, array $new_parent)
+	{
+		$diff = sizeof($subset_items) * 2;
+		$sql_not_subset_items = $this->db->sql_in_set($this->column_item_id, $subset_items, true);
+
+		$set_left_id = $this->db->sql_case($this->column_left_id . ' > ' . (int) $new_parent[$this->column_right_id], $this->column_left_id . ' + ' . $diff, $this->column_left_id);
+		$set_right_id = $this->db->sql_case($this->column_right_id . ' >= ' . (int) $new_parent[$this->column_right_id], $this->column_right_id . ' + ' . $diff, $this->column_right_id);
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->column_left_id . ' = ' . $set_left_id . ',
+				' . $this->column_right_id . ' = ' . $set_right_id . '
+			WHERE ' . $sql_not_subset_items . '
+				' . $this->get_sql_where('AND');
+		$this->db->sql_query($sql);
+
+		return $new_parent[$this->column_right_id] + $diff;
+	}
+
+	/**
+	* Resets values required for the nested set system
+	*
+	* @param array	$item		Original item data
+	* @return	array		Original item data + nested set defaults
+	*/
+	protected function reset_nestedset_values(array $item)
+	{
+		$item_data = array_merge($item, array(
+			$this->column_parent_id		=> 0,
+			$this->column_left_id		=> 0,
+			$this->column_right_id		=> 0,
+			$this->column_item_parents	=> '',
+		));
+
+		unset($item_data[$this->column_item_id]);
+
+		return $item_data;
+	}
+
+	/**
+	* Regenerate left/right ids from parent/child relationship
+	*
+	* This method regenerates the left/right ids for the tree based on
+	* the parent/child relations. This function executes three queries per
+	* item, so it should only be called, when the set has one of the following
+	* problems:
+	*	- The set has a duplicated value inside the left/right id chain
+	*	- The set has a missing value inside the left/right id chain
+	*	- The set has items that do not have a left/right id set
+	*
+	* When regenerating the items, the items are sorted by parent id and their
+	* current left id, so the current child/parent relationships are kept
+	* and running the function on a working set will not change the order.
+	*
+	* @param int	$new_id		First left_id to be used (should start with 1)
+	* @param int	$parent_id	parent_id of the current set (default = 0)
+	* @param bool	$reset_ids	Should we reset all left_id/right_id on the first call?
+	* @return	int		$new_id		The next left_id/right_id that should be used
+	*/
+	public function regenerate_left_right_ids($new_id, $parent_id = 0, $reset_ids = false)
+	{
+		if ($acquired_new_lock = $this->acquire_lock())
+		{
+			$this->db->sql_transaction('begin');
+
+			if (!$reset_ids)
+			{
+				$sql = 'UPDATE ' . $this->table_name . '
+					SET ' . $this->column_item_parents . " = ''
+					" . $this->get_sql_where('WHERE');
+				$this->db->sql_query($sql);
+			}
+		}
+
+		if ($reset_ids)
+		{
+			$sql = 'UPDATE ' . $this->table_name . '
+				SET ' . $this->db->sql_build_array('UPDATE', array(
+					$this->column_left_id		=> 0,
+					$this->column_right_id		=> 0,
+					$this->column_item_parents	=> '',
+				)) . '
+				' . $this->get_sql_where('WHERE');
+			$this->db->sql_query($sql);
+		}
+
+		$sql = 'SELECT *
+			FROM ' . $this->table_name . '
+			WHERE ' . $this->column_parent_id . ' = ' . (int) $parent_id . '
+				' . $this->get_sql_where('AND') . '
+			ORDER BY ' . $this->column_left_id . ', ' . $this->column_item_id . ' ASC';
+		$result = $this->db->sql_query($sql);
+		while ($row = $this->db->sql_fetchrow($result))
+		{
+			// First we update the left_id for this module
+			if ($row[$this->column_left_id] != $new_id)
+			{
+				$sql = 'UPDATE ' . $this->table_name . '
+					SET ' . $this->db->sql_build_array('UPDATE', array($this->column_left_id => $new_id)) . '
+					WHERE ' . $this->column_item_id . ' = ' . (int) $row[$this->column_item_id];
+				$this->db->sql_query($sql);
+			}
+			$new_id++;
+
+			// Then we go through any children and update their left/right id's
+			$new_id = $this->regenerate_left_right_ids($new_id, $row[$this->column_item_id]);
+
+			// Then we come back and update the right_id for this module
+			if ($row[$this->column_right_id] != $new_id)
+			{
+				$sql = 'UPDATE ' . $this->table_name . '
+					SET ' . $this->db->sql_build_array('UPDATE', array($this->column_right_id => $new_id)) . '
+					WHERE ' . $this->column_item_id . ' = ' . (int) $row[$this->column_item_id];
+				$this->db->sql_query($sql);
+			}
+			$new_id++;
+		}
+		$this->db->sql_freeresult($result);
+
+		if ($acquired_new_lock)
+		{
+			$this->db->sql_transaction('commit');
+			$this->lock->release();
+		}
+
+		return $new_id;
+	}
+}
diff --git a/phpBB/phpbb/tree/nestedset_forum.php b/phpBB/phpbb/tree/nestedset_forum.php
new file mode 100644
index 0000000000..ef6023546b
--- /dev/null
+++ b/phpBB/phpbb/tree/nestedset_forum.php
@@ -0,0 +1,40 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+namespace phpbb\tree;
+
+class nestedset_forum extends \phpbb\tree\nestedset
+{
+	/**
+	* Construct
+	*
+	* @param \phpbb\db\driver\driver	$db		Database connection
+	* @param \phpbb\lock\db		$lock	Lock class used to lock the table when moving forums around
+	* @param string				$table_name		Table name
+	*/
+	public function __construct(\phpbb\db\driver\driver $db, \phpbb\lock\db $lock, $table_name)
+	{
+		parent::__construct(
+			$db,
+			$lock,
+			$table_name,
+			'FORUM_NESTEDSET_',
+			'',
+			array(
+				'forum_id',
+				'forum_name',
+				'forum_type',
+			),
+			array(
+				'item_id'		=> 'forum_id',
+				'item_parents'	=> 'forum_parents',
+			)
+		);
+	}
+}
diff --git a/phpBB/phpbb/tree/tree_interface.php b/phpBB/phpbb/tree/tree_interface.php
new file mode 100644
index 0000000000..90ec27e024
--- /dev/null
+++ b/phpBB/phpbb/tree/tree_interface.php
@@ -0,0 +1,116 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+namespace phpbb\tree;
+
+interface tree_interface
+{
+	/**
+	* Inserts an item into the database table and into the tree.
+	*
+	* @param array	$item	The item to be added
+	* @return array Array with item data as set in the database
+	*/
+	public function insert(array $additional_data);
+
+	/**
+	* Delete an item from the tree and from the database table
+	*
+	* Also deletes the subtree from the tree and from the database table
+	*
+	* @param int	$item_id	The item to be deleted
+	* @return array		Item ids that have been deleted
+	*/
+	public function delete($item_id);
+
+	/**
+	* Move an item by a given delta
+	*
+	* An item is only moved up/down within the same parent. If the delta is
+	* larger then the number of children, the item is moved to the top/bottom
+	* of the list of children within this parent.
+	*
+	* @param int	$item_id	The item to be moved
+	* @param int	$delta		Number of steps to move this item, < 0 => down, > 0 => up
+	* @return bool True if the item was moved
+	*/
+	public function move($item_id, $delta);
+
+	/**
+	* Move an item down by 1
+	*
+	* @param int	$item_id	The item to be moved
+	* @return bool True if the item was moved
+	*/
+	public function move_down($item_id);
+
+	/**
+	* Move an item up by 1
+	*
+	* @param int	$item_id	The item to be moved
+	* @return bool True if the item was moved
+	*/
+	public function move_up($item_id);
+
+	/**
+	* Moves all children of one item to another item
+	*
+	* If the new parent already has children, the new children are appended
+	* to the list.
+	*
+	* @param int	$current_parent_id	The current parent item
+	* @param int	$new_parent_id		The new parent item
+	* @return bool True if any items where moved
+	*/
+	public function move_children($current_parent_id, $new_parent_id);
+
+	/**
+	* Change parent item
+	*
+	* Moves the item to the bottom of the new \parent's list of children
+	*
+	* @param int	$item_id			The item to be moved
+	* @param int	$new_parent_id		The new parent item
+	* @return bool True if the parent was set successfully
+	*/
+	public function change_parent($item_id, $new_parent_id);
+
+	/**
+	* Get all items that are either ancestors or descendants of the item
+	*
+	* @param int		$item_id		Id of the item to retrieve the ancestors/descendants from
+	* @param bool		$order_asc		Order the items ascendingly (most outer ancestor first)
+	* @param bool		$include_item	Should the item matching the given item id be included in the list as well
+	* @return array			Array of items (containing all columns from the item table)
+	*							ID => Item data
+	*/
+	public function get_path_and_subtree_data($item_id, $order_asc, $include_item);
+
+	/**
+	* Get all of the item's ancestors
+	*
+	* @param int		$item_id		Id of the item to retrieve the ancestors from
+	* @param bool		$order_asc		Order the items ascendingly (most outer ancestor first)
+	* @param bool		$include_item	Should the item matching the given item id be included in the list as well
+	* @return array			Array of items (containing all columns from the item table)
+	*							ID => Item data
+	*/
+	public function get_path_data($item_id, $order_asc, $include_item);
+
+	/**
+	* Get all of the item's descendants
+	*
+	* @param int		$item_id		Id of the item to retrieve the descendants from
+	* @param bool		$order_asc		Order the items ascendingly
+	* @param bool		$include_item	Should the item matching the given item id be included in the list as well
+	* @return array			Array of items (containing all columns from the item table)
+	*							ID => Item data
+	*/
+	public function get_subtree_data($item_id, $order_asc, $include_item);
+}