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<?php defined("SYSPATH") or die("No direct script access.");
/**
* Gallery - a web based photo album viewer and editor
* Copyright (C) 2000-2008 Bharat Mediratta
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.
*/
/**
* Implement Modified Preorder Tree Traversal on top of ORM.
*
* MPTT is an efficient way to store and retrieve hierarchical data in a single database table.
* For a good description, read http://www.sitepoint.com/article/hierarchical-data-database/3/
*
* This code was heavily influenced by code from:
* - http://code.google.com/p/kohana-mptt/
* - http://code.google.com/p/kohana-mptt/wiki/Documentation
* - http://code.google.com/p/s7ncms/source/browse/trunk/modules/s7ncms/libraries/ORM_MPTT.php
*
* Unfortunately that code was not ready for production and I did not want to absorb their code
* and licensing issues so I've reimplemented just the features that we need.
*/
class ORM_MPTT_Core extends ORM {
private $model_name = null;
private $parent = null;
private $parents = null;
private $children = null;
function __construct($id=null) {
parent::__construct($id);
$this->model_name = inflector::singular($this->table_name);
}
/**
* Add this node as a child of the parent provided.
*
* @chainable
* @param integer $parent_id the id of the parent node
* @return ORM
*/
function add_to_parent($parent_id) {
$this->_lock();
try {
$parent = ORM::factory($this->model_name, $parent_id);
$parent->_grow();
$this->left = $parent->right - 2;
$this->right = $parent->right - 1;
$this->parent_id = $parent->id;
$this->level = $parent->level + 1;
$this->save();
} catch (Exception $e) {
$this->_unlock();
throw $e;
}
$this->_unlock();
return $this;
}
/**
* Return the parent of this node
*
* @return ORM
*/
function parent() {
if (!isset($this->parent)) {
$this->parent =
ORM::factory($this->model_name)->where("id", $this->parent_id)->find();
}
return $this->parent;
}
/**
* Return all the parents of this node, in order from root to this node's immediate parent.
*
* @return array ORM
*/
function parents() {
if (!isset($this->parents)) {
$this->parents = $this
->where("`left` <= {$this->left}")
->where("`right` >= {$this->right}")
->where("id <> {$this->id}")
->orderby("left", "ASC")
->find_all();
}
return $this->parents;
}
/**
* Return all of the children of this node, ordered by id.
*
* @return array ORM
*/
function children() {
if (!isset($this->children)) {
$this->children =
$this->where("parent_id", $this->id)
->orderby("id", "ASC")
->find_all();
}
return $this->children;
}
function reload() {
$this->parent = null;
$this->parents = null;
$this->children = null;
return parent::reload();
}
/**
* Grow this node's space enough to make room for 1 or more new nodes.
*
* @param integer $count the number of new nodes to add
*/
private function _grow($count=1) {
$size = $count * 2;
$this->db->query(
"UPDATE `{$this->table_name}` SET `left` = `left` + $size WHERE `left` >= {$this->right}");
$this->db->query(
"UPDATE `{$this->table_name}` SET `right` = `right` + $size WHERE `right` >= {$this->right}");
$this->right += 2;
}
/**
* Lock the tree to prevent concurrent modification.
*/
private function _lock() {
$result = $this->db->query("SELECT GET_LOCK('{$this->table_name}', 1) AS L")->current();
if (empty($result->L)) {
throw new Exception("@todo UNABLE_TO_LOCK_EXCEPTION");
}
}
/**
* Unlock the tree.
*/
private function _unlock() {
$this->db->query("SELECT RELEASE_LOCK('{$this->table_name}')");
}
}
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