package dhcpsvc

import (
	"fmt"
	"net/netip"
	"time"

	"github.com/google/gopacket/layers"
)

// IPv6Config is the interface-specific configuration for DHCPv6.
type IPv6Config struct {
	// RangeStart is the first address in the range to assign to DHCP clients.
	RangeStart netip.Addr

	// Options is the list of DHCP options to send to DHCP clients.
	Options layers.DHCPOptions

	// LeaseDuration is the TTL of a DHCP lease.
	LeaseDuration time.Duration

	// RASlaacOnly defines whether the DHCP clients should only use SLAAC for
	// address assignment.
	RASLAACOnly bool

	// RAAllowSlaac defines whether the DHCP clients may use SLAAC for address
	// assignment.
	RAAllowSLAAC bool

	// Enabled is the state of the DHCPv6 service, whether it is enabled or not
	// on the specific interface.
	Enabled bool
}

// validate returns an error in conf if any.
func (conf *IPv6Config) validate() (err error) {
	switch {
	case conf == nil:
		return errNilConfig
	case !conf.Enabled:
		return nil
	case !conf.RangeStart.Is6():
		return fmt.Errorf("range start %s should be a valid ipv6", conf.RangeStart)
	case conf.LeaseDuration <= 0:
		return fmt.Errorf("lease duration %s must be positive", conf.LeaseDuration)
	default:
		return nil
	}
}

// iface6 is a DHCP interface for IPv6 address family.
//
// TODO(e.burkov):  Add options.
type iface6 struct {
	// rangeStart is the first IP address in the range.
	rangeStart netip.Addr

	// name is the name of the interface.
	name string

	// leaseTTL is the time-to-live of dynamic leases on this interface.
	leaseTTL time.Duration

	// raSLAACOnly defines if DHCP should send ICMPv6.RA packets without MO
	// flags.
	raSLAACOnly bool

	// raAllowSLAAC defines if DHCP should send ICMPv6.RA packets with MO flags.
	raAllowSLAAC bool
}

// newIface6 creates a new DHCP interface for IPv6 address family with the given
// configuration.
//
// TODO(e.burkov):  Validate properly.
func newIface6(name string, conf *IPv6Config) (i *iface6) {
	if !conf.Enabled {
		return nil
	}

	return &iface6{
		name:         name,
		rangeStart:   conf.RangeStart,
		leaseTTL:     conf.LeaseDuration,
		raSLAACOnly:  conf.RASLAACOnly,
		raAllowSLAAC: conf.RAAllowSLAAC,
	}
}