tree.php

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<?php
/* SVN FILE: $Id: tree.php 8178 2009-05-26 17:17:57Z mark_story $ */
/**
 * Tree behavior class.
 *
 * Enables a model object to act as a node-based tree.
 *
 * PHP versions 4 and 5
 *
 * CakePHP :  Rapid Development Framework (http://www.cakephp.org)
 * Copyright 2006-2008, Cake Software Foundation, Inc.
 *
 * Licensed under The MIT License
 * Redistributions of files must retain the above copyright notice.
 *
 * @filesource
 * @copyright     Copyright 2006-2008, Cake Software Foundation, Inc.
 * @link          http://www.cakefoundation.org/projects/info/cakephp CakePHP Project
 * @package       cake
 * @subpackage    cake.cake.libs.model.behaviors
 * @since         CakePHP v 1.2.0.4487
 * @version       $Revision: 8178 $
 * @modifiedby    $LastChangedBy: mark_story $
 * @lastmodified  $Date: 2009-05-26 13:17:57 -0400 (Tue, 26 May 2009) $
 * @license       http://www.opensource.org/licenses/mit-license.php The MIT License
 */
/**
 * Tree Behavior.
 *
 * Enables a model object to act as a node-based tree. Using Modified Preorder Tree Traversal
 * 
 * @see http://en.wikipedia.org/wiki/Tree_traversal
 * @package       cake
 * @subpackage    cake.cake.libs.model.behaviors
 */
class TreeBehavior extends ModelBehavior {
/**
 * Errors
 *
 * @var array
 */
    var $errors = array();
/**
 * Defaults
 *
 * @var array
 * @access protected
 */
    var $_defaults = array(
        'parent' => 'parent_id', 'left' => 'lft', 'right' => 'rght',
        'scope' => '1 = 1', 'type' => 'nested', '__parentChange' => false, 'recursive' => -1
    );
/**
 * Initiate Tree behavior
 *
 * @param object $Model instance of model
 * @param array $config array of configuration settings.
 * @return void
 * @access public
 */
    function setup(&$Model, $config = array()) {
        if (!is_array($config)) {
            $config = array('type' => $config);
        }
        $settings = array_merge($this->_defaults, $config);

        if (in_array($settings['scope'], $Model->getAssociated('belongsTo'))) {
            $data = $Model->getAssociated($settings['scope']);
            $parent =& $Model->{$settings['scope']};
            $settings['scope'] = $Model->alias . '.' . $data['foreignKey'] . ' = ' . $parent->alias . '.' . $parent->primaryKey;
            $settings['recursive'] = 0;
        }
        $this->settings[$Model->alias] = $settings;
    }
/**
 * After save method. Called after all saves
 *
 * Overriden to transparently manage setting the lft and rght fields if and only if the parent field is included in the
 * parameters to be saved.
 *
 * @param AppModel $Model Model instance.
 * @param boolean $created indicates whether the node just saved was created or updated
 * @return boolean true on success, false on failure
 * @access public
 */
    function afterSave(&$Model, $created) {
        extract($this->settings[$Model->alias]);
        if ($created) {
            if ((isset($Model->data[$Model->alias][$parent])) && $Model->data[$Model->alias][$parent]) {
                return $this->_setParent($Model, $Model->data[$Model->alias][$parent], $created);
            }
        } elseif ($__parentChange) {
            $this->settings[$Model->alias]['__parentChange'] = false;
            return $this->_setParent($Model, $Model->data[$Model->alias][$parent]);
        }
    }
/**
 * Before delete method. Called before all deletes
 *
 * Will delete the current node and all children using the deleteAll method and sync the table
 *
 * @param AppModel $Model Model instance
 * @return boolean true to continue, false to abort the delete
 * @access public
 */
    function beforeDelete(&$Model) {
        extract($this->settings[$Model->alias]);
        list($name, $data) = array($Model->alias, $Model->read());
        $data = $data[$name];

        if (!$data[$right] || !$data[$left]) {
            return true;
        }
        $diff = $data[$right] - $data[$left] + 1;

        if ($diff > 2) {
            if (is_string($scope)) {
                $scope = array($scope);
            }
            $scope[]["{$Model->alias}.{$left} BETWEEN ? AND ?"] = array($data[$left] + 1, $data[$right] - 1);
            $Model->deleteAll($scope);
        }
        $this->__sync($Model, $diff, '-', '> ' . $data[$right]);
        return true;
    }
/**
 * Before save method. Called before all saves
 *
 * Overriden to transparently manage setting the lft and rght fields if and only if the parent field is included in the
 * parameters to be saved. For newly created nodes with NO parent the left and right field values are set directly by
 * this method bypassing the setParent logic.
 *
 * @since         1.2
 * @param AppModel $Model Model instance
 * @return boolean true to continue, false to abort the save
 * @access public
 */
    function beforeSave(&$Model) {
        extract($this->settings[$Model->alias]);

        if (isset($Model->data[$Model->alias][$Model->primaryKey])) {
            if ($Model->data[$Model->alias][$Model->primaryKey]) {
                if (!$Model->id) {
                    $Model->id = $Model->data[$Model->alias][$Model->primaryKey];
                }
            }
            unset($Model->data[$Model->alias][$Model->primaryKey]);
        }

        $this->_addToWhitelist($Model, array($left, $right));
        if (!$Model->id) {
            if (array_key_exists($parent, $Model->data[$Model->alias]) && $Model->data[$Model->alias][$parent]) {
                $parentNode = $Model->find('first', array(
                    'conditions' => array($scope, $Model->escapeField() => $Model->data[$Model->alias][$parent]),
                    'fields' => array($Model->primaryKey, $right), 'recursive' => $recursive
                ));
                if (!$parentNode) {
                    return false;
                }
                list($parentNode) = array_values($parentNode);
                $Model->data[$Model->alias][$left] = 0; //$parentNode[$right];
                $Model->data[$Model->alias][$right] = 0; //$parentNode[$right] + 1;
            } else {
                $edge = $this->__getMax($Model, $scope, $right, $recursive);
                $Model->data[$Model->alias][$left] = $edge + 1;
                $Model->data[$Model->alias][$right] = $edge + 2;
            }
        } elseif (array_key_exists($parent, $Model->data[$Model->alias])) {
            if ($Model->data[$Model->alias][$parent] != $Model->field($parent)) {
                $this->settings[$Model->alias]['__parentChange'] = true;
            }
            if (!$Model->data[$Model->alias][$parent]) {
                $Model->data[$Model->alias][$parent] = null;
                $this->_addToWhitelist($Model, $parent);
            } else {
                list($node) = array_values($Model->find('first', array(
                    'conditions' => array($scope,$Model->escapeField() => $Model->id),
                    'fields' => array($Model->primaryKey, $parent, $left, $right ), 'recursive' => $recursive)
                ));

                $parentNode = $Model->find('first', array(
                    'conditions' => array($scope, $Model->escapeField() => $Model->data[$Model->alias][$parent]),
                    'fields' => array($Model->primaryKey, $left, $right), 'recursive' => $recursive
                ));
                if (!$parentNode) {
                    return false;
                }
                list($parentNode) = array_values($parentNode);

                if (($node[$left] < $parentNode[$left]) && ($parentNode[$right] < $node[$right])) {
                    return false;
                } elseif ($node[$Model->primaryKey] == $parentNode[$Model->primaryKey]) {
                    return false;
                }
            }
        }
        return true;
    }
/**
 * Get the number of child nodes
 *
 * If the direct parameter is set to true, only the direct children are counted (based upon the parent_id field)
 * If false is passed for the id parameter, all top level nodes are counted, or all nodes are counted.
 *
 * @param AppModel $Model Model instance
 * @param mixed $id The ID of the record to read or false to read all top level nodes
 * @param boolean $direct whether to count direct, or all, children
 * @return integer number of child nodes
 * @access public
 */
    function childcount(&$Model, $id = null, $direct = false) {
        if (is_array($id)) {
            extract (array_merge(array('id' => null), $id));
        }
        if ($id === null && $Model->id) {
            $id = $Model->id;
        } elseif (!$id) {
            $id = null;
        }
        extract($this->settings[$Model->alias]);

        if ($direct) {
            return $Model->find('count', array('conditions' => array($scope, $Model->escapeField($parent) => $id)));
        }

        if ($id === null) {
            return $Model->find('count', array('conditions' => $scope));
        } elseif (isset($Model->data[$Model->alias][$left]) && isset($Model->data[$Model->alias][$right])) {
            $data = $Model->data[$Model->alias];
        } else {
            $data = $Model->find('first', array('conditions' => array($scope, $Model->escapeField() => $id), 'recursive' => $recursive));
            if (!$data) {
                return 0;
            }
            $data = $data[$Model->alias];
        }
        return ($data[$right] - $data[$left] - 1) / 2;
    }
/**
 * Get the child nodes of the current model
 *
 * If the direct parameter is set to true, only the direct children are returned (based upon the parent_id field)
 * If false is passed for the id parameter, top level, or all (depending on direct parameter appropriate) are counted.
 *
 * @param AppModel $Model Model instance
 * @param mixed $id The ID of the record to read
 * @param boolean $direct whether to return only the direct, or all, children
 * @param mixed $fields Either a single string of a field name, or an array of field names
 * @param string $order SQL ORDER BY conditions (e.g. "price DESC" or "name ASC") defaults to the tree order
 * @param integer $limit SQL LIMIT clause, for calculating items per page.
 * @param integer $page Page number, for accessing paged data
 * @param integer $recursive The number of levels deep to fetch associated records
 * @return array Array of child nodes
 * @access public
 */
    function children(&$Model, $id = null, $direct = false, $fields = null, $order = null, $limit = null, $page = 1, $recursive = null) {
        if (is_array($id)) {
            extract (array_merge(array('id' => null), $id));
        }
        $overrideRecursive = $recursive;

        if ($id === null && $Model->id) {
            $id = $Model->id;
        } elseif (!$id) {
            $id = null;
        }
        $name = $Model->alias;
        extract($this->settings[$Model->alias]);

        if (!is_null($overrideRecursive)) {
            $recursive = $overrideRecursive;
        }
        if (!$order) {
            $order = $Model->alias . '.' . $left . ' asc';
        }
        if ($direct) {
            $conditions = array($scope, $Model->escapeField($parent) => $id);
            return $Model->find('all', compact('conditions', 'fields', 'order', 'limit', 'page', 'recursive'));
        }

        if (!$id) {
            $conditions = $scope;
        } else {
            $result = array_values($Model->find('first', array(
                'conditions' => array($scope, $Model->escapeField() => $id),
                'fields' => array($left, $right),
                'recursive' => $recursive
            )));

            if (empty($result) || !isset($result[0])) {
                return array();
            }
            $conditions = array($scope,
                $Model->escapeField($right) . ' <' => $result[0][$right],
                $Model->escapeField($left) . ' >' => $result[0][$left]
            );
        }
        return $Model->find('all', compact('conditions', 'fields', 'order', 'limit', 'page', 'recursive'));
    }
/**
 * A convenience method for returning a hierarchical array used for HTML select boxes
 *
 * @param AppModel $Model Model instance
 * @param mixed $conditions SQL conditions as a string or as an array('field' =>'value',...)
 * @param string $keyPath A string path to the key, i.e. "{n}.Post.id"
 * @param string $valuePath A string path to the value, i.e. "{n}.Post.title"
 * @param string $spacer The character or characters which will be repeated
 * @param integer $recursive The number of levels deep to fetch associated records
 * @return array An associative array of records, where the id is the key, and the display field is the value
 * @access public
 */
    function generatetreelist(&$Model, $conditions = null, $keyPath = null, $valuePath = null, $spacer = '_', $recursive = null) {
        $overrideRecursive = $recursive;
        extract($this->settings[$Model->alias]);
        if (!is_null($overrideRecursive)) {
            $recursive = $overrideRecursive;
        }

        if ($keyPath == null && $valuePath == null && $Model->hasField($Model->displayField)) {
            $fields = array($Model->primaryKey, $Model->displayField, $left, $right);
        } else {
            $fields = null;
        }

        if ($keyPath == null) {
            $keyPath = '{n}.' . $Model->alias . '.' . $Model->primaryKey;
        }

        if ($valuePath == null) {
            $valuePath = array('{0}{1}', '{n}.tree_prefix', '{n}.' . $Model->alias . '.' . $Model->displayField);

        } elseif (is_string($valuePath)) {
            $valuePath = array('{0}{1}', '{n}.tree_prefix', $valuePath);

        } else {
            $valuePath[0] = '{' . (count($valuePath) - 1) . '}' . $valuePath[0];
            $valuePath[] = '{n}.tree_prefix';
        }
        $order = $Model->alias . '.' . $left . ' asc';
        $results = $Model->find('all', compact('conditions', 'fields', 'order', 'recursive'));
        $stack = array();

        foreach ($results as $i => $result) {
            while ($stack && ($stack[count($stack) - 1] < $result[$Model->alias][$right])) {
                array_pop($stack);
            }
            $results[$i]['tree_prefix'] = str_repeat($spacer,count($stack));
            $stack[] = $result[$Model->alias][$right];
        }
        if (empty($results)) {
            return array();
        }
        return Set::combine($results, $keyPath, $valuePath);
    }
/**
 * Get the parent node
 *
 * reads the parent id and returns this node
 *
 * @param AppModel $Model Model instance
 * @param mixed $id The ID of the record to read
 * @param integer $recursive The number of levels deep to fetch associated records
 * @return array Array of data for the parent node
 * @access public
 */
    function getparentnode(&$Model, $id = null, $fields = null, $recursive = null) {
        if (is_array($id)) {
            extract (array_merge(array('id' => null), $id));
        }
        $overrideRecursive = $recursive;
        if (empty ($id)) {
            $id = $Model->id;
        }
        extract($this->settings[$Model->alias]);
        if (!is_null($overrideRecursive)) {
            $recursive = $overrideRecursive;
        }
        $parentId = $Model->read($parent, $id);

        if ($parentId) {
            $parentId = $parentId[$Model->alias][$parent];
            $parent = $Model->find('first', array('conditions' => array($Model->escapeField() => $parentId), 'fields' => $fields, 'recursive' => $recursive));

            return $parent;
        }
        return false;
    }
/**
 * Get the path to the given node
 *
 * @param AppModel $Model Model instance
 * @param mixed $id The ID of the record to read
 * @param mixed $fields Either a single string of a field name, or an array of field names
 * @param integer $recursive The number of levels deep to fetch associated records
 * @return array Array of nodes from top most parent to current node
 * @access public
 */
    function getpath(&$Model, $id = null, $fields = null, $recursive = null) {
        if (is_array($id)) {
            extract (array_merge(array('id' => null), $id));
        }
        $overrideRecursive = $recursive;
        if (empty ($id)) {
            $id = $Model->id;
        }
        extract($this->settings[$Model->alias]);
        if (!is_null($overrideRecursive)) {
            $recursive = $overrideRecursive;
        }
        $result = $Model->find('first', array('conditions' => array($Model->escapeField() => $id), 'fields' => array($left, $right), 'recursive' => $recursive));
        if ($result) {
            $result = array_values($result);
        } else {
            return null;
        }
        $item = $result[0];
        $results = $Model->find('all', array(
            'conditions' => array($scope, $Model->escapeField($left) . ' <=' => $item[$left], $Model->escapeField($right) . ' >=' => $item[$right]),
            'fields' => $fields, 'order' => array($Model->escapeField($left) => 'asc'), 'recursive' => $recursive
        ));
        return $results;
    }
/**
 * Reorder the node without changing the parent.
 *
 * If the node is the last child, or is a top level node with no subsequent node this method will return false
 *
 * @param AppModel $Model Model instance
 * @param mixed $id The ID of the record to move
 * @param mixed $number how many places to move the node or true to move to last position
 * @return boolean true on success, false on failure
 * @access public
 */
    function movedown(&$Model, $id = null, $number = 1) {
        if (is_array($id)) {
            extract (array_merge(array('id' => null), $id));
        }
        if (!$number) {
            return false;
        }
        if (empty ($id)) {
            $id = $Model->id;
        }
        extract($this->settings[$Model->alias]);
        list($node) = array_values($Model->find('first', array(
            'conditions' => array($scope, $Model->escapeField() => $id),
            'fields' => array($Model->primaryKey, $left, $right, $parent), 'recursive' => $recursive
        )));
        if ($node[$parent]) {
            list($parentNode) = array_values($Model->find('first', array(
                'conditions' => array($scope, $Model->escapeField() => $node[$parent]),
                'fields' => array($Model->primaryKey, $left, $right), 'recursive' => $recursive
            )));
            if (($node[$right] + 1) == $parentNode[$right]) {
                return false;
            }
        }
        $nextNode = $Model->find('first', array(
            'conditions' => array($scope, $Model->escapeField($left) => ($node[$right] + 1)),
            'fields' => array($Model->primaryKey, $left, $right), 'recursive' => $recursive)
        );
        if ($nextNode) {
            list($nextNode)= array_values($nextNode);
        } else {
            return false;
        }
        $edge = $this->__getMax($Model, $scope, $right, $recursive);
        $this->__sync($Model, $edge - $node[$left] + 1, '+', 'BETWEEN ' . $node[$left] . ' AND ' . $node[$right]);
        $this->__sync($Model, $nextNode[$left] - $node[$left], '-', 'BETWEEN ' . $nextNode[$left] . ' AND ' . $nextNode[$right]);
        $this->__sync($Model, $edge - $node[$left] - ($nextNode[$right] - $nextNode[$left]), '-', '> ' . $edge);

        if (is_int($number)) {
            $number--;
        }
        if ($number) {
            $this->moveDown($Model, $id, $number);
        }
        return true;
    }
/**
 * Reorder the node without changing the parent.
 *
 * If the node is the first child, or is a top level node with no previous node this method will return false
 *
 * @param AppModel $Model Model instance
 * @param mixed $id The ID of the record to move
 * @param mixed $number how many places to move the node, or true to move to first position
 * @return boolean true on success, false on failure
 * @access public
 */
    function moveup(&$Model, $id = null, $number = 1) {
        if (is_array($id)) {
            extract (array_merge(array('id' => null), $id));
        }
        if (!$number) {
            return false;
        }
        if (empty ($id)) {
            $id = $Model->id;
        }
        extract($this->settings[$Model->alias]);
        list($node) = array_values($Model->find('first', array(
            'conditions' => array($scope, $Model->escapeField() => $id),
            'fields' => array($Model->primaryKey, $left, $right, $parent ), 'recursive' => $recursive
        )));
        if ($node[$parent]) {
            list($parentNode) = array_values($Model->find('first', array(
                'conditions' => array($scope, $Model->escapeField() => $node[$parent]),
                'fields' => array($Model->primaryKey, $left, $right), 'recursive' => $recursive
            )));
            if (($node[$left] - 1) == $parentNode[$left]) {
                return false;
            }
        }
        $previousNode = $Model->find('first', array(
            'conditions' => array($scope, $Model->escapeField($right) => ($node[$left] - 1)),
            'fields' => array($Model->primaryKey, $left, $right),
            'recursive' => $recursive
        ));

        if ($previousNode) {
            list($previousNode) = array_values($previousNode);
        } else {
            return false;
        }
        $edge = $this->__getMax($Model, $scope, $right, $recursive);
        $this->__sync($Model, $edge - $previousNode[$left] +1, '+', 'BETWEEN ' . $previousNode[$left] . ' AND ' . $previousNode[$right]);
        $this->__sync($Model, $node[$left] - $previousNode[$left], '-', 'BETWEEN ' .$node[$left] . ' AND ' . $node[$right]);
        $this->__sync($Model, $edge - $previousNode[$left] - ($node[$right] - $node[$left]), '-', '> ' . $edge);
        if (is_int($number)) {
            $number--;
        }
        if ($number) {
            $this->moveUp($Model, $id, $number);
        }
        return true;
    }
/**
 * Recover a corrupted tree
 *
 * The mode parameter is used to specify the source of info that is valid/correct. The opposite source of data
 * will be populated based upon that source of info. E.g. if the MPTT fields are corrupt or empty, with the $mode
 * 'parent' the values of the parent_id field will be used to populate the left and right fields. The missingParentAction
 * parameter only applies to "parent" mode and determines what to do if the parent field contains an id that is not present.
 *
 * @todo Could be written to be faster, *maybe*. Ideally using a subquery and putting all the logic burden on the DB.
 * @param AppModel $Model Model instance
 * @param string $mode parent or tree
 * @param mixed $missingParentAction 'return' to do nothing and return, 'delete' to
 * delete, or the id of the parent to set as the parent_id
 * @return boolean true on success, false on failure
 * @access public
 */
    function recover(&$Model, $mode = 'parent', $missingParentAction = null) {
        if (is_array($mode)) {
            extract (array_merge(array('mode' => 'parent'), $mode));
        }
        extract($this->settings[$Model->alias]);
        $Model->recursive = $recursive;
        if ($mode == 'parent') {
            $Model->bindModel(array('belongsTo' => array('VerifyParent' => array(
                'className' => $Model->alias,
                'foreignKey' => $parent,
                'fields' => array($Model->primaryKey, $left, $right, $parent),
            ))));
            $missingParents = $Model->find('list', array(
                'recursive' => 0,
                'conditions' => array($scope, array(
                    'NOT' => array($Model->escapeField($parent) => null), $Model->VerifyParent->escapeField() => null
                ))
            ));
            $Model->unbindModel(array('belongsTo' => array('VerifyParent')));
            if ($missingParents) {
                if ($missingParentAction == 'return') {
                    foreach ($missingParents as $id => $display) {
                        $this->errors[] = 'cannot find the parent for ' . $Model->alias . ' with id ' . $id . '(' . $display . ')';

                    }
                    return false;
                } elseif ($missingParentAction == 'delete') {
                    $Model->deleteAll(array($Model->primaryKey => array_flip($missingParents)));
                } else {
                    $Model->updateAll(array($parent => $missingParentAction), array($Model->escapeField($Model->primaryKey) => array_flip($missingParents)));
                }
            }
            $count = 1;
            foreach ($Model->find('all', array('conditions' => $scope, 'fields' => array($Model->primaryKey), 'order' => $left)) as $array) {
                $Model->id = $array[$Model->alias][$Model->primaryKey];
                $lft = $count++;
                $rght = $count++;
                $Model->save(array($left => $lft, $right => $rght), array('callbacks' => false));
            }
            foreach ($Model->find('all', array('conditions' => $scope, 'fields' => array($Model->primaryKey, $parent), 'order' => $left)) as $array) {
                $Model->create();
                $Model->id = $array[$Model->alias][$Model->primaryKey];
                $this->_setParent($Model, $array[$Model->alias][$parent]);
            }
        } else {
            $db =& ConnectionManager::getDataSource($Model->useDbConfig);
            foreach ($Model->find('all', array('conditions' => $scope, 'fields' => array($Model->primaryKey, $parent), 'order' => $left)) as $array) {
                $path = $this->getpath($Model, $array[$Model->alias][$Model->primaryKey]);
                if ($path == null || count($path) < 2) {
                    $parentId = null;
                } else {
                    $parentId = $path[count($path) - 2][$Model->alias][$Model->primaryKey];
                }
                $Model->updateAll(array($parent => $db->value($parentId, $parent)), array($Model->escapeField() => $array[$Model->alias][$Model->primaryKey]));
            }
        }
        return true;
    }
/**
 * Reorder method.
 *
 * Reorders the nodes (and child nodes) of the tree according to the field and direction specified in the parameters.
 * This method does not change the parent of any node.
 *
 * Requires a valid tree, by default it verifies the tree before beginning.
 * 
 * Options:
 * 
 * - 'id' id of record to use as top node for reordering
 * - 'field' Which field to use in reordeing defaults to displayField
 * - 'order' Direction to order either DESC or ASC (defaults to ASC)
 * - 'verify' Whether or not to verify the tree before reorder. defaults to true.
 *
 * @param AppModel $Model Model instance
 * @param array $options array of options to use in reordering.
 * @return boolean true on success, false on failure
 */
    function reorder(&$Model, $options = array()) {
        $options = array_merge(array('id' => null, 'field' => $Model->displayField, 'order' => 'ASC', 'verify' => true), $options);
        extract($options);
        if ($verify && !$this->verify($Model)) {
            return false;
        }
        $verify = false;
        extract($this->settings[$Model->alias]);
        $fields = array($Model->primaryKey, $field, $left, $right);
        $sort = $field . ' ' . $order;
        $nodes = $this->children($Model, $id, true, $fields, $sort, null, null, $recursive);

        if ($nodes) {
            foreach ($nodes as $node) {
                $id = $node[$Model->alias][$Model->primaryKey];
                $this->moveDown($Model, $id, true);
                if ($node[$Model->alias][$left] != $node[$Model->alias][$right] - 1) {
                    $this->reorder($Model, compact('id', 'field', 'order', 'verify'));
                }
            }
        }
        return true;
    }
/**
 * Remove the current node from the tree, and reparent all children up one level.
 *
 * If the parameter delete is false, the node will become a new top level node. Otherwise the node will be deleted
 * after the children are reparented.
 *
 * @param AppModel $Model Model instance
 * @param mixed $id The ID of the record to remove
 * @param boolean $delete whether to delete the node after reparenting children (if any)
 * @return boolean true on success, false on failure
 * @access public
 */
    function removefromtree(&$Model, $id = null, $delete = false) {
        if (is_array($id)) {
            extract (array_merge(array('id' => null), $id));
        }
        extract($this->settings[$Model->alias]);

        list($node) = array_values($Model->find('first', array(
            'conditions' => array($scope, $Model->escapeField() => $id),
            'fields' => array($Model->primaryKey, $left, $right, $parent),
            'recursive' => $recursive
        )));

        if ($node[$right] == $node[$left] + 1) {
            if ($delete) {
                return $Model->delete($id);
            } else {
                $Model->id = $id;
                return $Model->saveField($parent, null);
            }
        } elseif ($node[$parent]) {
            list($parentNode) = array_values($Model->find('first', array(
                'conditions' => array($scope, $Model->escapeField() => $node[$parent]),
                'fields' => array($Model->primaryKey, $left, $right),
                'recursive' => $recursive
            )));
        } else {
            $parentNode[$right] = $node[$right] + 1;
        }

        $db =& ConnectionManager::getDataSource($Model->useDbConfig);
        $Model->updateAll(array($parent => $db->value($node[$parent], $parent)), array($parent => $node[$Model->primaryKey]));
        $this->__sync($Model, 1, '-', 'BETWEEN ' . ($node[$left] + 1) . ' AND ' . ($node[$right] - 1));
        $this->__sync($Model, 2, '-', '> ' . ($node[$right]));
        $Model->id = $id;

        if ($delete) {
            $Model->updateAll(
                array(
                    $Model->escapeField($left) => 0,
                    $Model->escapeField($right) => 0,
                    $Model->escapeField($parent) => null
                ),
                array($Model->escapeField() => $id)
            );
            return $Model->delete($id);
        } else {
            $edge = $this->__getMax($Model, $scope, $right, $recursive);
            if ($node[$right] == $edge) {
                $edge = $edge - 2;
            }
            $Model->id = $id;
            return $Model->save(
                array($left => $edge + 1, $right => $edge + 2, $parent => null),
                array('callbacks' => false)
            );
        }
    }
/**
 * Check if the current tree is valid.
 *
 * Returns true if the tree is valid otherwise an array of (type, incorrect left/right index, message)
 *
 * @param AppModel $Model Model instance
 * @return mixed true if the tree is valid or empty, otherwise an array of (error type [index, node],
 *  [incorrect left/right index,node id], message)
 * @access public
 */
    function verify(&$Model) {
        extract($this->settings[$Model->alias]);
        if (!$Model->find('count', array('conditions' => $scope))) {
            return true;
        }
        $min = $this->__getMin($Model, $scope, $left, $recursive);
        $edge = $this->__getMax($Model, $scope, $right, $recursive);
        $errors =  array();

        for ($i = $min; $i <= $edge; $i++) {
            $count = $Model->find('count', array('conditions' => array(
                $scope, 'OR' => array($Model->escapeField($left) => $i, $Model->escapeField($right) => $i)
            )));
            if ($count != 1) {
                if ($count == 0) {
                    $errors[] = array('index', $i, 'missing');
                } else {
                    $errors[] = array('index', $i, 'duplicate');
                }
            }
        }
        $node = $Model->find('first', array('conditions' => array($scope, $Model->escapeField($right) . '< ' . $Model->escapeField($left)), 'recursive' => 0));
        if ($node) {
            $errors[] = array('node', $node[$Model->alias][$Model->primaryKey], 'left greater than right.');
        }

        $Model->bindModel(array('belongsTo' => array('VerifyParent' => array(
            'className' => $Model->alias,
            'foreignKey' => $parent,
            'fields' => array($Model->primaryKey, $left, $right, $parent)
        ))));

        foreach ($Model->find('all', array('conditions' => $scope, 'recursive' => 0)) as $instance) {
            if (is_null($instance[$Model->alias][$left]) || is_null($instance[$Model->alias][$right])) {
                $errors[] = array('node', $instance[$Model->alias][$Model->primaryKey],
                    'has invalid left or right values');
            } elseif ($instance[$Model->alias][$left] == $instance[$Model->alias][$right]) {
                $errors[] = array('node', $instance[$Model->alias][$Model->primaryKey],
                    'left and right values identical');
            } elseif ($instance[$Model->alias][$parent]) {
                if (!$instance['VerifyParent'][$Model->primaryKey]) {
                    $errors[] = array('node', $instance[$Model->alias][$Model->primaryKey],
                        'The parent node ' . $instance[$Model->alias][$parent] . ' doesn\'t exist');
                } elseif ($instance[$Model->alias][$left] < $instance['VerifyParent'][$left]) {
                    $errors[] = array('node', $instance[$Model->alias][$Model->primaryKey],
                        'left less than parent (node ' . $instance['VerifyParent'][$Model->primaryKey] . ').');
                } elseif ($instance[$Model->alias][$right] > $instance['VerifyParent'][$right]) {
                    $errors[] = array('node', $instance[$Model->alias][$Model->primaryKey],
                        'right greater than parent (node ' . $instance['VerifyParent'][$Model->primaryKey] . ').');
                }
            } elseif ($Model->find('count', array('conditions' => array($scope, $Model->escapeField($left) . ' <' => $instance[$Model->alias][$left], $Model->escapeField($right) . ' >' => $instance[$Model->alias][$right]), 'recursive' => 0))) {
                $errors[] = array('node', $instance[$Model->alias][$Model->primaryKey], 'The parent field is blank, but has a parent');
            }
        }
        if ($errors) {
            return $errors;
        }
        return true;
    }
/**
 * Sets the parent of the given node
 *
 * The force parameter is used to override the "don't change the parent to the current parent" logic in the event
 * of recovering a corrupted table, or creating new nodes. Otherwise it should always be false. In reality this
 * method could be private, since calling save with parent_id set also calls setParent
 *
 * @param AppModel $Model Model instance
 * @param mixed $parentId
 * @return boolean true on success, false on failure
 * @access protected
 */
    function _setParent(&$Model, $parentId = null, $created = false) {
        extract($this->settings[$Model->alias]);
        list($node) = array_values($Model->find('first', array(
            'conditions' => array($scope, $Model->escapeField() => $Model->id),
            'fields' => array($Model->primaryKey, $parent, $left, $right),
            'recursive' => $recursive
        )));
        $edge = $this->__getMax($Model, $scope, $right, $recursive, $created);

        if (empty ($parentId)) {
            $this->__sync($Model, $edge - $node[$left] + 1, '+', 'BETWEEN ' . $node[$left] . ' AND ' . $node[$right], $created);
            $this->__sync($Model, $node[$right] - $node[$left] + 1, '-', '> ' . $node[$left], $created);
        } else {
            $parentNode = array_values($Model->find('first', array(
                'conditions' => array($scope, $Model->escapeField() => $parentId),
                'fields' => array($Model->primaryKey, $left, $right),
                'recursive' => $recursive
            )));

            if (empty($parentNode) || empty($parentNode[0])) {
                return false;
            }
            $parentNode = $parentNode[0];

            if (($Model->id == $parentId)) {
                return false;

            } elseif (($node[$left] < $parentNode[$left]) && ($parentNode[$right] < $node[$right])) {
                return false;
            }
            if (empty ($node[$left]) && empty ($node[$right])) {
                $this->__sync($Model, 2, '+', '>= ' . $parentNode[$right], $created);
                $result = $Model->save(
                    array($left => $parentNode[$right], $right => $parentNode[$right] + 1, $parent => $parentId),
                    array('validate' => false, 'callbacks' => false)
                );
                $Model->data = $result;
            } else {
                $this->__sync($Model, $edge - $node[$left] +1, '+', 'BETWEEN ' . $node[$left] . ' AND ' . $node[$right], $created);
                $diff = $node[$right] - $node[$left] + 1;

                if ($node[$left] > $parentNode[$left]) {
                    if ($node[$right] < $parentNode[$right]) {
                        $this->__sync($Model, $diff, '-', 'BETWEEN ' . $node[$right] . ' AND ' . ($parentNode[$right] - 1), $created);
                        $this->__sync($Model, $edge - $parentNode[$right] + $diff + 1, '-', '> ' . $edge, $created);
                    } else {
                        $this->__sync($Model, $diff, '+', 'BETWEEN ' . $parentNode[$right] . ' AND ' . $node[$right], $created);
                        $this->__sync($Model, $edge - $parentNode[$right] + 1, '-', '> ' . $edge, $created);
                    }
                } else {
                    $this->__sync($Model, $diff, '-', 'BETWEEN ' . $node[$right] . ' AND ' . ($parentNode[$right] - 1), $created);
                    $this->__sync($Model, $edge - $parentNode[$right] + $diff + 1, '-', '> ' . $edge, $created);
                }
            }
        }
        return true;
    }
/**
 * get the maximum index value in the table.
 *
 * @param AppModel $Model
 * @param string $scope
 * @param string $right
 * @return int
 * @access private
 */
    function __getMax($Model, $scope, $right, $recursive = -1, $created = false) {
        $db =& ConnectionManager::getDataSource($Model->useDbConfig);
        if ($created) {
            if (is_string($scope)) {
                $scope .= " AND {$Model->alias}.{$Model->primaryKey} <> ";
                $scope .= $db->value($Model->id, $Model->getColumnType($Model->primaryKey));
            } else {
                $scope['NOT'][$Model->alias . '.' . $Model->primaryKey] = $Model->id;
            }
        }
        $name = $Model->alias . '.' . $right;
        list($edge) = array_values($Model->find('first', array(
            'conditions' => $scope,
            'fields' => $db->calculate($Model, 'max', array($name, $right)),
            'recursive' => $recursive
        )));
        return (empty($edge[$right])) ? 0 : $edge[$right];
    }
/**
 * get the minimum index value in the table.
 *
 * @param AppModel $Model
 * @param string $scope
 * @param string $right
 * @return int
 * @access private
 */
    function __getMin($Model, $scope, $left, $recursive = -1) {
        $db =& ConnectionManager::getDataSource($Model->useDbConfig);
        $name = $Model->alias . '.' . $left;
        list($edge) = array_values($Model->find('first', array(
            'conditions' => $scope,
            'fields' => $db->calculate($Model, 'min', array($name, $left)),
            'recursive' => $recursive
        )));
        return (empty($edge[$left])) ? 0 : $edge[$left];
    }
/**
 * Table sync method.
 *
 * Handles table sync operations, Taking account of the behavior scope.
 *
 * @param AppModel $Model
 * @param integer $shift
 * @param string $direction
 * @param array $conditions
 * @param string $field
 * @access private
 */
    function __sync(&$Model, $shift, $dir = '+', $conditions = array(), $created = false, $field = 'both') {
        $ModelRecursive = $Model->recursive;
        extract($this->settings[$Model->alias]);
        $Model->recursive = $recursive;

        if ($field == 'both') {
            $this->__sync($Model, $shift, $dir, $conditions, $created, $left);
            $field = $right;
        }
        if (is_string($conditions)) {
            $conditions = array("{$Model->alias}.{$field} {$conditions}");
        }
        if (($scope != '1 = 1' && $scope !== true) && $scope) {
            $conditions[] = $scope;
        }
        if ($created) {
            $conditions['NOT'][$Model->alias . '.' . $Model->primaryKey] = $Model->id;
        }
        $Model->updateAll(array($Model->alias . '.' . $field => $Model->escapeField($field) . ' ' . $dir . ' ' . $shift), $conditions);
        $Model->recursive = $ModelRecursive;
    }
}
?>

---