/**
* Check wether the current move is possible and if not, rais an exception.
*
* @return void
*/
protected function guardAgainstImpossibleMove()
{
if (!$this->node->exists) {
throw new MoveNotPossibleException('A new node cannot be moved.');
}
if (array_search($this->position, array('child', 'left', 'right', 'root')) === FALSE) {
throw new MoveNotPossibleException("Position should be one of ['child', 'left', 'right'] but is {$this->position}.");
}
if (!$this->promotingToRoot()) {
if (is_null($this->target)) {
if ($this->position === 'left' || $this->position === 'right') {
throw new MoveNotPossibleException("Could not resolve target node. This node cannot move any further to the {$this->position}.");
} else {
throw new MoveNotPossibleException('Could not resolve target node.');
}
}
if ($this->node->equals($this->target)) {
throw new MoveNotPossibleException('A node cannot be moved to itself.');
}
if ($this->target->insideSubtree($this->node)) {
throw new MoveNotPossibleException('A node cannot be moved to a descendant of itself (inside moved tree).');
}
if (!$this->node->inSameScope($this->target)) {
throw new MoveNotPossibleException('A node cannot be moved to a different scope.');
}
}
}