pocketmine\entity\Minecart::getDirectionToMove PHP Method

    private function getDirectionToMove($railType, $candidateDirection)
    {
        switch ($railType) {
            case Rail::STRAIGHT_NORTH_SOUTH:
            case Rail::SLOPED_ASCENDING_NORTH:
            case Rail::SLOPED_ASCENDING_SOUTH:
                switch ($candidateDirection) {
                    case Entity::NORTH:
                    case Entity::SOUTH:
                        return $candidateDirection;
                }
                break;
            case Rail::STRAIGHT_EAST_WEST:
            case Rail::SLOPED_ASCENDING_EAST:
            case Rail::SLOPED_ASCENDING_WEST:
                switch ($candidateDirection) {
                    case Entity::WEST:
                    case Entity::EAST:
                        return $candidateDirection;
                }
                break;
            case Rail::CURVED_SOUTH_EAST:
                switch ($candidateDirection) {
                    case Entity::SOUTH:
                    case Entity::EAST:
                        return $candidateDirection;
                    case Entity::NORTH:
                        return $this->checkForTurn($candidateDirection, Entity::EAST);
                    case Entity::WEST:
                        return $this->checkForTurn($candidateDirection, Entity::SOUTH);
                }
                break;
            case Rail::CURVED_SOUTH_WEST:
                switch ($candidateDirection) {
                    case Entity::SOUTH:
                    case Entity::WEST:
                        return $candidateDirection;
                    case Entity::NORTH:
                        return $this->checkForTurn($candidateDirection, Entity::WEST);
                    case Entity::EAST:
                        return $this->checkForTurn($candidateDirection, Entity::SOUTH);
                }
                break;
            case Rail::CURVED_NORTH_WEST:
                switch ($candidateDirection) {
                    case Entity::NORTH:
                    case Entity::WEST:
                        return $candidateDirection;
                    case Entity::SOUTH:
                        return $this->checkForTurn($candidateDirection, Entity::WEST);
                    case Entity::EAST:
                        return $this->checkForTurn($candidateDirection, Entity::NORTH);
                }
                break;
            case Rail::CURVED_NORTH_EAST:
                switch ($candidateDirection) {
                    case Entity::NORTH:
                    case Entity::EAST:
                        return $candidateDirection;
                    case Entity::SOUTH:
                        return $this->checkForTurn($candidateDirection, Entity::EAST);
                    case Entity::WEST:
                        return $this->checkForTurn($candidateDirection, Entity::NORTH);
                }
                break;
        }
        return -1;
    }