// newUnitNumber returns the unit number to use for attaching a new device to the given controller.
func (l VirtualDeviceList) newUnitNumber(c types.BaseVirtualController) int32 {
	units := make([]bool, 30)

	switch sc := c.(type) {
	case types.BaseVirtualSCSIController:
		//  The SCSI controller sits on its own bus
		units[sc.GetVirtualSCSIController().ScsiCtlrUnitNumber] = true
	}

	key := c.GetVirtualController().Key

	for _, device := range l {
		d := device.GetVirtualDevice()

		if d.ControllerKey == key && d.UnitNumber != nil {
			units[int(*d.UnitNumber)] = true
		}
	}

	for unit, used := range units {
		if !used {
			return int32(unit)
		}
	}

	return -1
}

// AssignController assigns a device to a controller.
func (l VirtualDeviceList) AssignController(device types.BaseVirtualDevice, c types.BaseVirtualController) {
	d := device.GetVirtualDevice()
	d.ControllerKey = c.GetVirtualController().Key
	d.UnitNumber = new(int32)
	*d.UnitNumber = l.newUnitNumber(c)
	if d.Key == 0 {
		d.Key = -1
	}
}

// NewVirtualDisk returns a new disk attached to the controller
func NewVirtualDisk(controller types.BaseVirtualController) *types.VirtualDisk {

	defer trace.End(trace.Begin(""))

	return &types.VirtualDisk{
		VirtualDevice: types.VirtualDevice{
			ControllerKey: controller.GetVirtualController().Key,
			UnitNumber:    new(int32),
		},
	}
}

// AssignController assigns a device to a controller.
func (l VirtualDeviceList) AssignController(device types.BaseVirtualDevice, c types.BaseVirtualController) {
	d := device.GetVirtualDevice()
	d.ControllerKey = c.GetVirtualController().Key
	d.UnitNumber = l.newUnitNumber(c)
	if d.UnitNumber == 0 {
		d.UnitNumber = -1 // TODO: this field is annotated as omitempty
	}
	if d.Key == 0 {
		d.Key = -1
	}
}

// newUnitNumber returns the unit number to use for attaching a new device to the given controller.
func (l VirtualDeviceList) newUnitNumber(c types.BaseVirtualController) int32 {
	key := c.GetVirtualController().Key
	var max int32 = -1

	for _, device := range l {
		d := device.GetVirtualDevice()

		if d.ControllerKey == key {
			if d.UnitNumber != nil && *d.UnitNumber > max {
				max = *d.UnitNumber
			}
		}
	}

	return max + 1
}

func getNextUnitNumber(devices object.VirtualDeviceList, c types.BaseVirtualController) (int32, error) {
	// get next available SCSI controller unit number
	var takenUnitNumbers [SCSIDeviceSlots]bool
	takenUnitNumbers[SCSIReservedSlot] = true
	key := c.GetVirtualController().Key

	for _, device := range devices {
		d := device.GetVirtualDevice()
		if d.ControllerKey == key {
			if d.UnitNumber != nil {
				takenUnitNumbers[*d.UnitNumber] = true
			}
		}
	}
	for unitNumber, takenUnitNumber := range takenUnitNumbers {
		if !takenUnitNumber {
			return int32(unitNumber), nil
		}
	}
	return -1, fmt.Errorf("SCSI Controller with key=%d does not have any available slots (LUN).", key)
}