<?php
/**
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @since         CakePHP(tm) v 3.0.0
 * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
 */
namespace Cake\Model\Behavior;

use Cake\Event\Event;
use Cake\ORM\Behavior;
use Cake\ORM\Entity;
use Cake\ORM\Table;

/**
 * Makes the table to which this is attached to behave like a nested set and
 * provides methods for managing and retrieving information out of the derived
 * hierarchical structure.
 *
 * Tables attaching this behavior are required to have a column referencing the
 * parent row, and two other numeric columns (lft and rght) where the implicit
 * order will be cached.
 *
 * For more information on what is a nested set and a how it works refer to
 * http://www.sitepoint.com/hierarchical-data-database-2/
 */
class TreeBehavior extends Behavior {

/**
 * Table instance
 *
 * @var \Cake\ORM\Table
 */
	protected $_table;

/**
 * Default config
 *
 * These are merged with user-provided configuration when the behavior is used.
 *
 * @var array
 */
	protected $_defaultConfig = [
		'implementedFinders' => [
			'path' => 'findPath',
			'children' => 'findChildren',
			'treeList' => 'findTreeList'
		],
		'implementedMethods' => [
			'childCount' => 'childCount',
			'moveUp' => 'moveUp',
			'moveDown' => 'moveDown',
			'recover' => 'recover',
			'removeFromTree' => 'removeFromTree'
		],
		'parent' => 'parent_id',
		'left' => 'lft',
		'right' => 'rght',
		'scope' => null
	];

/**
 * Constructor
 *
 * @param Table $table The table this behavior is attached to.
 * @param array $config The config for this behavior.
 */
	public function __construct(Table $table, array $config = []) {
		parent::__construct($table, $config);
		$this->_table = $table;
	}

/**
 * Before save listener.
 * Transparently manages setting the lft and rght fields if the parent field is
 * included in the parameters to be saved.
 *
 * @param \Cake\Event\Event the beforeSave event that was fired
 * @param \Cake\ORM\Entity the entity that is going to be saved
 * @return void
 * @throws \RuntimeException if the parent to set for the node is invalid
 */
	public function beforeSave(Event $event, Entity $entity) {
		$isNew = $entity->isNew();
		$config = $this->config();
		$parent = $entity->get($config['parent']);
		$primaryKey = (array)$this->_table->primaryKey();
		$dirty = $entity->dirty($config['parent']);

		if ($isNew && $parent) {
			if ($entity->get($primaryKey[0]) == $parent) {
				throw new \RuntimeException("Cannot set a node's parent as itself");
			}

			$parentNode = $this->_getNode($parent);
			$edge = $parentNode->get($config['right']);
			$entity->set($config['left'], $edge);
			$entity->set($config['right'], $edge + 1);
			$this->_sync(2, '+', ">= {$edge}");
		}

		if ($isNew && !$parent) {
			$edge = $this->_getMax();
			$entity->set($config['left'], $edge + 1);
			$entity->set($config['right'], $edge + 2);
		}

		if (!$isNew && $dirty && $parent) {
			$this->_setParent($entity, $parent);
		}

		if (!$isNew && $dirty && !$parent) {
			$this->_setAsRoot($entity);
		}
	}

/**
 * Also deletes the nodes in the subtree of the entity to be delete
 *
 * @param \Cake\Event\Event the beforeDelete event that was fired
 * @param \Cake\ORM\Entity the entity that is going to be saved
 * @return void
 */
	public function beforeDelete(Event $event, Entity $entity) {
		$config = $this->config();
		$this->_ensureFields($entity);
		$left = $entity->get($config['left']);
		$right = $entity->get($config['right']);
		$diff = $right - $left + 1;

		if ($diff > 2) {
			$this->_table->deleteAll([
				"{$config['left']} >=" => $left + 1,
				"{$config['left']} <=" => $right - 1
			]);
		}

		$this->_sync($diff, '-', "> {$right}");
	}

/**
 * Sets the correct left and right values for the passed entity so it can be
 * updated to a new parent. It also makes the hole in the tree so the node
 * move can be done without corrupting the structure.
 *
 * @param \Cake\ORM\Entity $entity The entity to re-parent
 * @param mixed $parent the id of the parent to set
 * @return void
 * @throws \RuntimeException if the parent to set to the entity is not valid
 */
	protected function _setParent($entity, $parent) {
		$config = $this->config();
		$parentNode = $this->_getNode($parent);
		$this->_ensureFields($entity);
		$parentLeft = $parentNode->get($config['left']);
		$parentRight = $parentNode->get($config['right']);
		$right = $entity->get($config['right']);
		$left = $entity->get($config['left']);

		if ($parentLeft > $left && $parentLeft < $right) {
			throw new \RuntimeException(sprintf(
				'Cannot use node "%s" as parent for entity "%s"',
				$parent,
				$entity->get($this->_table->primaryKey())
			));
		}

		// Values for moving to the left
		$diff = $right - $left + 1;
		$targetLeft = $parentRight;
		$targetRight = $diff + $parentRight - 1;
		$min = $parentRight;
		$max = $left - 1;

		if ($left < $targetLeft) {
			//Moving to the right
			$targetLeft = $parentRight - $diff;
			$targetRight = $parentRight - 1;
			$min = $right + 1;
			$max = $parentRight - 1;
			$diff *= -1;
		}

		if ($right - $left > 1) {
			//Correcting internal subtree
			$internalLeft = $left + 1;
			$internalRight = $right - 1;
			$this->_sync($targetLeft - $left, '+', "BETWEEN {$internalLeft} AND {$internalRight}", true);
		}

		$this->_sync($diff, '+', "BETWEEN {$min} AND {$max}");

		if ($right - $left > 1) {
			$this->_unmarkInternalTree();
		}

		//Allocating new position
		$entity->set($config['left'], $targetLeft);
		$entity->set($config['right'], $targetRight);
	}

/**
 * Updates the left and right column for the passed entity so it can be set as
 * a new root in the tree. It also modifies the ordering in the rest of the tree
 * so the structure remains valid
 *
 * @param \Cake\ORM\Entity $entity The entity to set as a new root
 * @return void
 */
	protected function _setAsRoot($entity) {
		$config = $this->config();
		$edge = $this->_getMax();
		$this->_ensureFields($entity);
		$right = $entity->get($config['right']);
		$left = $entity->get($config['left']);
		$diff = $right - $left;

		if ($right - $left > 1) {
			//Correcting internal subtree
			$internalLeft = $left + 1;
			$internalRight = $right - 1;
			$this->_sync($edge - $diff - $left, '+', "BETWEEN {$internalLeft} AND {$internalRight}", true);
		}

		$this->_sync($diff + 1, '-', "BETWEEN {$right} AND {$edge}");

		if ($right - $left > 1) {
			$this->_unmarkInternalTree();
		}

		$entity->set($config['left'], $edge - $diff);
		$entity->set($config['right'], $edge);
	}

/**
 * Helper method used to invert the sign of the left and right columns that are
 * less than 0. They were set to negative values before so their absolute value
 * wouldn't change while performing other tree transformations.
 *
 * @return void
 */
	protected function _unmarkInternalTree() {
		$config = $this->config();
		$query = $this->_table->query();
		$this->_table->updateAll([
			$query->newExpr()->add("{$config['left']} = {$config['left']} * -1"),
			$query->newExpr()->add("{$config['right']} = {$config['right']} * -1"),
		], [$config['left'] . ' <' => 0]);
	}

/**
 * Custom finder method which can be used to return the list of nodes from the root
 * to a specific node in the tree. This custom finder requires that the key 'for'
 * is passed in the options containing the id of the node to get its path for.
 *
 * @param \Cake\ORM\Query $query The constructed query to modify
 * @param array $options the list of options for the query
 * @return \Cake\ORM\Query
 * @throws \InvalidArgumentException If the 'for' key is missing in options
 */
	public function findPath($query, $options) {
		if (empty($options['for'])) {
			throw new \InvalidArgumentException("The 'for' key is required for find('path')");
		}

		$config = $this->config();
		list($left, $right) = [$config['left'], $config['right']];
		$node = $this->_table->get($options['for'], ['fields' => [$left, $right]]);

		return $this->_scope($query)
			->where([
				"$left <=" => $node->get($left),
				"$right >=" => $node->get($right)
			]);
	}

/**
 * Get the number of children nodes.
 *
 * @param \Cake\ORM\Entity $node The entity to count children for
 * @param boolean $direct whether to count all nodes in the subtree or just
 * direct children
 * @return integer Number of children nodes.
 */
	public function childCount(Entity $node, $direct = false) {
		$config = $this->config();
		list($parent, $left, $right) = [$config['parent'], $config['left'], $config['right']];

		if ($direct) {
			return $this->_scope($this->_table->find())
				->where([$parent => $node->get($this->_table->primaryKey())])
				->count();
		}

		$this->_ensureFields($node);
		return ($node->{$right} - $node->{$left} - 1) / 2;
	}

/**
 * Get the children nodes of the current model
 *
 * Available options are:
 *
 * - for: The id of the record to read.
 * - direct: Boolean, whether to return only the direct (true), or all (false) children,
 *   defaults to false (all children).
 *
 * If the direct option is set to true, only the direct children are returned (based upon the parent_id field)
 *
 * @param \Cake\ORM\Query $query
 * @param array $options Array of options as described above
 * @return \Cake\ORM\Query
 * @throws \InvalidArgumentException When the 'for' key is not passed in $options
 */
	public function findChildren($query, $options) {
		$config = $this->config();
		$options += ['for' => null, 'direct' => false];
		list($parent, $left, $right) = [$config['parent'], $config['left'], $config['right']];
		list($for, $direct) = [$options['for'], $options['direct']];

		if (empty($for)) {
			throw new \InvalidArgumentException("The 'for' key is required for find('children')");
		}

		if ($query->clause('order') === null) {
			$query->order([$left => 'ASC']);
		}

		if ($direct) {
			return $this->_scope($query)->where([$parent => $for]);
		}

		$node = $this->_getNode($for);
		return $this->_scope($query)
			->where([
				"{$right} <" => $node->{$right},
				"{$left} >" => $node->{$left}
			]);
	}

/**
 * Gets a representation of the elements in the tree as a flat list where the keys are
 * the primary key for the table and the values are the display field for the table. 
 * Values are prefixed to visually indicate relative depth in the tree.
 *
 * Avaliable options are:
 *
 * - keyPath: A dot separated path to fetch the field to use for the array key, or a closure to
 *  return the key out of the provided row.
 * - valuePath: A dot separated path to fetch the field to use for the array value, or a closure to
 *  return the value out of the provided row.
 *  - spacer: A string to be used as prefix for denoting the depth in the tree for each item
 *
 * @param \Cake\ORM\Query $query
 * @param array $options Array of options as described above
 * @return \Cake\ORM\Query
 */
	public function findTreeList($query, $options) {
		return $this->_scope($query)
			->find('threaded', ['parentField' => $this->config()['parent']])
			->formatResults(function($results) use ($options) {
				$options += [
					'keyPath' => $this->_table->primaryKey(),
					'valuePath' => $this->_table->displayField(),
					'spacer' => '_'
				];
				return $results
					->listNested()
					->printer($options['valuePath'], $options['keyPath'], $options['spacer']);
			});
	}

/**
 * Removes the current node from the tree, by positioning it as a new root
 * and re-parents all children up one level.
 *
 * Note that the node will not be deleted just moved away from its current position
 * without moving its children with it.
 *
 * @param \Cake\ORM\Entity $node The node to remove from the tree
 * @return \Cake\ORM\Entity|false the node after being removed from the tree or
 * false on error
 */
	public function removeFromTree(Entity $node) {
		return $this->_table->connection()->transactional(function() use ($node) {
			$this->_ensureFields($node);
			return $this->_removeFromTree($node);
		});
	}

/**
 * Helper function containing the actual code for removeFromTree
 *
 * @param \Cake\ORM\Entity $node The node to remove from the tree
 * @return \Cake\ORM\Entity|false the node after being removed from the tree or
 * false on error
 */
	protected function _removeFromTree($node) {
		$config = $this->config();
		$left = $node->get($config['left']);
		$right = $node->get($config['right']);
		$parent = $node->get($config['parent']);

		$node->set($config['parent'], null);

		if ($right - $left == 1) {
			return $this->_table->save($node);
		}

		$primary = $this->_table->primaryKey();
		$this->_table->updateAll(
			[$config['parent'] => $parent],
			[$config['parent'] => $node->get($primary)]
		);
		$this->_sync(1, '-', 'BETWEEN ' . ($left + 1) . ' AND ' . ($right - 1));
		$this->_sync(2, '-', "> {$right}");
		$edge = $this->_getMax();
		$node->set($config['left'], $edge + 1);
		$node->set($config['right'], $edge + 2);
		$fields = [$config['parent'], $config['left'], $config['right']];

		$this->_table->updateAll($node->extract($fields), [$primary => $node->get($primary)]);

		foreach ($fields as $field) {
			$node->dirty($field, false);
		}
		return $node;
	}

/**
 * Reorders the node without changing its parent.
 *
 * If the node is the first child, or is a top level node with no previous node
 * this method will return false
 *
 * @param \Cake\ORM\Entity $node The node to move
 * @param integer|boolean $number How many places to move the node, or true to move to first position
 * @throws \Cake\ORM\Error\RecordNotFoundException When node was not found
 * @return \Cake\ORM\Entity|boolean $node The node after being moved or false on failure
 */
	public function moveUp(Entity $node, $number = 1) {
		return $this->_table->connection()->transactional(function() use ($node, $number) {
			$this->_ensureFields($node);
			return $this->_moveUp($node, $number);
		});
	}

/**
 * Helper function used with the actual code for moveUp
 *
 * @param \Cake\ORM\Entity $node The node to move
 * @param integer|boolean $number How many places to move the node, or true to move to first position
 * @throws \Cake\ORM\Error\RecordNotFoundException When node was not found
 * @return \Cake\ORM\Entity|boolean $node The node after being moved or false on failure
 */
	protected function _moveUp($node, $number) {
		$config = $this->config();
		list($parent, $left, $right) = [$config['parent'], $config['left'], $config['right']];

		if (!$number) {
			return false;
		}

		$parentLeft = 0;
		if ($node->get($parent)) {
			$parentLeft = $this->_getNode($node->get($parent))->get($left);
		}

		$edge = $this->_getMax();
		while ($number-- > 0) {
			list($nodeLeft, $nodeRight) = array_values($node->extract([$left, $right]));

			if ($parentLeft && ($nodeLeft - 1 == $parentLeft)) {
				break;
			}

			$nextNode = $this->_scope($this->_table->find())
				->select([$left, $right])
				->where([$right => ($nodeLeft - 1)])
				->first();

			if (!$nextNode) {
				break;
			}

			$this->_sync($edge - $nextNode->{$left} + 1, '+', "BETWEEN {$nextNode->{$left}} AND {$nextNode->{$right}}");
			$this->_sync($nodeLeft - $nextNode->{$left}, '-', "BETWEEN {$nodeLeft} AND {$nodeRight}");
			$this->_sync($edge - $nextNode->{$left} - ($nodeRight - $nodeLeft), '-', "> {$edge}");

			$newLeft = $nodeLeft;
			if ($nodeLeft >= $nextNode->{$left} || $nodeLeft <= $nextNode->{$right}) {
				$newLeft -= $edge - $nextNode->{$left} + 1;
			}
			$newLeft = $nodeLeft - ($nodeLeft - $nextNode->{$left});

			$node->set($left, $newLeft);
			$node->set($right, $newLeft + ($nodeRight - $nodeLeft));
		}

		$node->dirty($left, false);
		$node->dirty($right, false);
		return $node;
	}

/**
 * Reorders 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 \Cake\ORM\Entity $node The node to move
 * @param integer|boolean $number How many places to move the node or true to move to last position
 * @throws \Cake\ORM\Error\RecordNotFoundException When node was not found
 * @return \Cake\ORM\Entity|boolean the entity after being moved or false on failure
 */
	public function moveDown(Entity $node, $number = 1) {
		return $this->_table->connection()->transactional(function() use ($node, $number) {
			$this->_ensureFields($node);
			return $this->_moveDown($node, $number);
		});
	}

/**
 * Helper function used with the actual code for moveDown
 *
 * @param \Cake\ORM\Entity $node The node to move
 * @param integer|boolean $number How many places to move the node, or true to move to last position
 * @throws \Cake\ORM\Error\RecordNotFoundException When node was not found
 * @return \Cake\ORM\Entity|boolean $node The node after being moved or false on failure
 */
	protected function _moveDown($node, $number) {
		$config = $this->config();
		list($parent, $left, $right) = [$config['parent'], $config['left'], $config['right']];

		if (!$number) {
			return false;
		}

		$parentRight = 0;
		if ($node->get($parent)) {
			$parentRight = $this->_getNode($node->get($parent))->get($right);
		}

		if ($number === true) {
			$number = PHP_INT_MAX;
		}

		$edge = $this->_getMax();
		while ($number-- > 0) {
			list($nodeLeft, $nodeRight) = array_values($node->extract([$left, $right]));

			if ($parentRight && ($nodeRight + 1 == $parentRight)) {
				break;
			}

			$nextNode = $this->_scope($this->_table->find())
				->select([$left, $right])
				->where([$left => $nodeRight + 1])
				->first();

			if (!$nextNode) {
				break;
			}

			$this->_sync($edge - $nodeLeft + 1, '+', "BETWEEN {$nodeLeft} AND {$nodeRight}");
			$this->_sync($nextNode->{$left} - $nodeLeft, '-', "BETWEEN {$nextNode->{$left}} AND {$nextNode->{$right}}");
			$this->_sync($edge - $nodeLeft - ($nextNode->{$right} - $nextNode->{$left}), '-', "> {$edge}");

			$newLeft = $edge + 1;
			if ($newLeft >= $nextNode->{$left} || $newLeft <= $nextNode->{$right}) {
				$newLeft -= $nextNode->{$left} - $nodeLeft;
			}
			$newLeft -= $nextNode->{$right} - $nextNode->{$left} - 1;

			$node->set($left, $newLeft);
			$node->set($right, $newLeft + ($nodeRight - $nodeLeft));
		}

		$node->dirty($left, false);
		$node->dirty($right, false);
		return $node;
	}

/**
 * Returns a single node from the tree from its primary key
 *
 * @param mixed $id
 * @return Cake\ORM\Entity
 * @throws \Cake\ORM\Error\RecordNotFoundException When node was not found
 */
	protected function _getNode($id) {
		$config = $this->config();
		list($parent, $left, $right) = [$config['parent'], $config['left'], $config['right']];
		$primaryKey = $this->_table->primaryKey();

		$node = $this->_scope($this->_table->find())
			->select([$parent, $left, $right])
			->where([$primaryKey => $id])
			->first();

		if (!$node) {
			throw new \Cake\ORM\Error\RecordNotFoundException("Node \"{$id}\" was not found in the tree.");
		}

		return $node;
	}

/**
 * Recovers the lft and right column values out of the hirearchy defined by the
 * parent column.
 *
 * @return void
 */
	public function recover() {
		$this->_table->connection()->transactional(function() {
			$this->_recoverTree();
		});
	}

/**
 * Recursive method used to recover a single level of the tree
 *
 * @param integer $counter The Last left column value that was assigned
 * @param mixed $parentId the parent id of the level to be recovered
 * @return integer Ne next value to use for the left column
 */
	protected function _recoverTree($counter = 0, $parentId = null) {
		$config = $this->config();
		list($parent, $left, $right) = [$config['parent'], $config['left'], $config['right']];
		$pk = (array)$this->_table->primaryKey();

		$query = $this->_scope($this->_table->query())
			->select($pk)
			->where(function($exp) use ($parentId, $parent) {
				return $parentId === null ? $exp->isNull($parent) : $exp->eq($parent, $parentId);
			})
			->order($pk)
			->hydrate(false)
			->bufferResults(false);

		$leftCounter = $counter;
		foreach ($query as $row) {
			$counter++;
			$counter = $this->_recoverTree($counter, $row[$pk[0]]);
		}

		if ($parentId === null) {
			return $counter;
		}

		$this->_table->updateAll(
			[$left => $leftCounter, $right => $counter + 1],
			[$pk[0] => $parentId]
		);

		return $counter + 1;
	}

/**
 * Returns the maximum index value in the table.
 *
 * @return integer
 */
	protected function _getMax() {
		$config = $this->config();
		$field = $config['right'];

		$edge = $this->_scope($this->_table->find())
			->select([$field])
			->order([$field => 'DESC'])
			->first();

		if (empty($edge->{$field})) {
			return 0;
		}

		return $edge->{$field};
	}

/**
 * Auxiliary function used to automatically alter the value of both the left and
 * right columns by a certain amount that match the passed conditions
 *
 * @param integer $shift the value to use for operating the left and right columns
 * @param string $dir The operator to use for shifting the value (+/-)
 * @param string $conditions a SQL snipped to be used for comparing left or right
 * against it.
 * @param boolean $mark whether to mark the updated values so that they can not be
 * modified by future calls to this function.
 * @return void
 */
	protected function _sync($shift, $dir, $conditions, $mark = false) {
		$config = $this->config();

		foreach ([$config['left'], $config['right']] as $field) {
			$query = $this->_scope($this->_table->query());

			$mark = $mark ? '*-1' : '';
			$template = sprintf('%s = (%s %s %s)%s', $field, $field, $dir, $shift, $mark);
			$query->update()->set($query->newExpr()->add($template));
			$query->where("{$field} {$conditions}");

			$query->execute();
		}
	}

/**
 * Alters the passed query so that it only returns scoped records as defined
 * in the tree configuration.
 *
 * @param \Cake\ORM\Query $query the Query to modify
 * @return \Cake\ORM\Query
 */
	protected function _scope($query) {
		$config = $this->config();

		if (is_array($config['scope'])) {
			return $query->where($config['scope']);
		} elseif (is_callable($config['scope'])) {
			return $config['scope']($query);
		}

		return $query;
	}

/**
 * Ensures that the provided entity contains non-empty values for the left and
 * right fields
 *
 * @param \Cake\ORM\Entity $entity The entity to ensure fields for
 * @return void
 */
	protected function _ensureFields($entity) {
		$config = $this->config();
		$fields = [$config['left'], $config['right']];
		$values = array_filter($entity->extract($fields));
		if (count($values) === count($fields)) {
			return;
		}

		$fresh = $this->_table->get($entity->get($this->_table->primaryKey()), $fields);
		$entity->set($fresh->extract($fields), ['guard' => false]);

		foreach ($fields as $field) {
			$entity->dirty($field, false);
		}
	}

}