dhcpsvc

type Config struct {
	// Interfaces stores configurations of DHCP server specific for the network
	// interface identified by its name.
	Interfaces map[string]*InterfaceConfig

	// Logger will be used to log the DHCP events.
	Logger *slog.Logger

	// LocalDomainName is the top-level domain name to use for resolving DHCP
	// clients' hostnames.
	LocalDomainName string

	// ICMPTimeout is the timeout for checking another DHCP server's presence.
	ICMPTimeout time.Duration

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

type DHCPServer struct {
	// contains filtered or unexported fields
}

type Empty struct{}

type IPv4Config struct {
	// GatewayIP is the IPv4 address of the network's gateway.  It is used as
	// the default gateway for DHCP clients and also used in calculating the
	// network-specific broadcast address.
	GatewayIP netip.Addr

	// SubnetMask is the IPv4 subnet mask of the network.  It should be a valid
	// IPv4 CIDR (i.e. all 1s followed by all 0s).
	SubnetMask netip.Addr

	// RangeStart is the first address in the range to assign to DHCP clients.
	RangeStart netip.Addr

	// RangeEnd is the last address in the range to assign to DHCP clients.
	RangeEnd netip.Addr

	// Options is the list of DHCP options to send to DHCP clients.  The options
	// having a zero value within the Length field are treated as deletions of
	// the corresponding options, either implicit or explicit.
	Options layers.DHCPOptions

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

	// Enabled is the state of the DHCPv4 service, whether it is enabled or not
	// on the specific interface.
	Enabled bool
}

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.  The options
	// with zero length are treated as deletions of the corresponding options,
	// either implicit or explicit.
	Options layers.DHCPv6Options

	// 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
}

type Interface interface {
	agh.ServiceWithConfig[*Config]

	// Enabled returns true if DHCP provides information about clients.
	Enabled() (ok bool)

	// HostByIP returns the hostname of the DHCP client with the given IP
	// address.  The address will be netip.Addr{} if there is no such client,
	// due to an assumption that a DHCP client must always have an IP address.
	HostByIP(ip netip.Addr) (host string)

	// MACByIP returns the MAC address for the given IP address leased.  It
	// returns nil if there is no such client, due to an assumption that a DHCP
	// client must always have a MAC address.
	//
	// TODO(e.burkov):  Think of a contract for the returned value.
	MACByIP(ip netip.Addr) (mac net.HardwareAddr)

	// IPByHost returns the IP address of the DHCP client with the given
	// hostname.  The hostname will be an empty string if there is no such
	// client, due to an assumption that a DHCP client must always have a
	// hostname, either set or generated.
	IPByHost(host string) (ip netip.Addr)

	// Leases returns all the active DHCP leases.  The returned slice should be
	// a clone.
	//
	// TODO(e.burkov):  Consider implementing iterating methods with appropriate
	// signatures instead of cloning the whole list.
	Leases() (ls []*Lease)

	// AddLease adds a new DHCP lease.  l must be valid.  It returns an error if
	// l already exists.
	AddLease(ctx context.Context, l *Lease) (err error)

	// UpdateStaticLease replaces an existing static DHCP lease.  l must be
	// valid.  It returns an error if the lease with the given hardware address
	// doesn't exist or if other values match another existing lease.
	UpdateStaticLease(ctx context.Context, l *Lease) (err error)

	// RemoveLease removes an existing DHCP lease.  l must be valid.  It returns
	// an error if there is no lease equal to l.
	RemoveLease(ctx context.Context, l *Lease) (err error)

	// Reset removes all the DHCP leases.
	//
	// TODO(e.burkov):  If it's really needed?
	Reset(ctx context.Context) (err error)
}

type InterfaceConfig struct {
	// IPv4 is the configuration of DHCP protocol for IPv4.
	IPv4 *IPv4Config

	// IPv6 is the configuration of DHCP protocol for IPv6.
	IPv6 *IPv6Config
}

type Lease struct {
	// IP is the IP address leased to the client.
	IP netip.Addr

	// Expiry is the expiration time of the lease.
	Expiry time.Time

	// Hostname of the client.
	Hostname string

	// HWAddr is the physical hardware address (MAC address).
	HWAddr net.HardwareAddr

	// IsStatic defines if the lease is static.
	IsStatic bool
}