package haza

import "encoding/binary"
import "net"

type Dhcp4OptCode = uint8
type Dhcp4MsgType = uint8

const (
	_ Dhcp4MsgType = iota

	DHCP4_MSG_DISCOVER = 1
	DHCP4_MSG_OFFER = 2
	DHCP4_MSG_REQUEST = 3
	DHCP4_MSG_DECLINE = 4
	DHCP4_MSG_ACK = 5
	DHCP4_MSG_NAK = 6
	DHCP4_MSG_RELEASE = 7
	DHCP4_MSG_INFORM = 8

	DHCP4_MSG_FORCE_RENEW = 9

	DHCP4_MSG_LEASE_QUERY = 10
	DHCP4_MSG_LEASE_UNASSIGNED = 11
	DHCP4_MSG_LEASE_UNKNOWN = 12
	DHCP4_MSG_LEASE_ACTIVE = 13

	DHCP4_MSG_BULK_LEASE_QUERY = 14
	DHCP4_MSG_LEASE_QUERY_DONE = 15
	DHCP4_MSG_ACTIVE_LEASE_QUERY = 16
	DHCP4_MSG_LEASE_QUERY_STATUS = 17
	DHCP4_MSG_TLS = 18
)

const (
	DHCP4_OPT_PADDING Dhcp4OptCode = iota // 0
	DHCP4_OPT_SUBNET_MASK = 0x01
	DHCP4_OPT_TIME_OFFSET = 0x02
	DHCP4_OPT_ROUTER = 0x03
	DHCP4_OPT_TIME_SERVER = 0x04
	DHCP4_OPT_NAME_SERVER = 0x05
	DHCP4_OPT_DNS_SERVER = 0x06
	DHCP4_OPT_LOG_SERVER = 0x07
	DHCP4_OPT_QUOTE_SERVER = 0x08
	DHCP4_OPT_LPR_SERVER = 0x09

	DHCP4_OPT_HOST_NAME = 0x0C
	DHCP4_OPT_VENDOR_SPECIFIC = 0x2B
	DHCP4_OPT_REQUESTED_IPADDR = 0x32
	DHCP4_OPT_LEASE_TIME = 0x33
	DHCP4_OPT_OVERLOAD = 0x34
	DHCP4_OPT_MSG_TYPE = 0x35
	DHCP4_OPT_SERVER_ID = 0x36
	DHCP4_OPT_PARAM_REQ_LIST = 0x37
	DHCP4_OPT_ERROR_TEXT = 0x38
	DHCP4_OPT_MAX_MSG_SIZE = 0x39
	DHCP4_OPT_RENEWAL_TIME = 0x3A // T1
	DHCP4_OPT_REBINDING_TIME = 0x3B // T2
	DHCP4_OPT_CLIENT_ID = 0x3D
	DHCP4_OPT_END = 0xFF
)

const (
	DHCP4_OPT_VAL_UINT8 = 0
)

type Dhcp4Opt interface {
	Code() Dhcp4OptCode
	Bytes() []byte
}

type Dhcp4OptBase struct {
	code Dhcp4OptCode
}

type Dhcp4OptIp4Addr struct {
	Dhcp4OptBase
	value net.IP
}

type Dhcp4OptIp4Addrs struct {
	Dhcp4OptBase
	value []net.IP
}

type Dhcp4OptString struct {
	Dhcp4OptBase
	value string
}

type Dhcp4OptBytes struct {
	Dhcp4OptBase
	value []byte
}

type Dhcp4OptUint32 struct {
	Dhcp4OptBase
	value uint32
}

type Dhcp4OptUint16 struct {
	Dhcp4OptBase
	value uint16
}

type Dhcp4OptUint8 struct {
	Dhcp4OptBase
	value uint8
}

func (opt *Dhcp4OptBase) Code() Dhcp4OptCode {
	return opt.code
}

func (opt *Dhcp4OptIp4Addr) Bytes() []byte {
	// net.IP itself is []byte
	var buf []byte
	buf = opt.value.To4()
	if buf == nil { return []byte{} }
	return buf
}

func (opt *Dhcp4OptIp4Addrs) Bytes() []byte {
	var buf []byte
	var v net.IP
	var v4 []byte
	var count int

	count = 0
	for _, ip := range opt.value {
		if ip.To4() != nil { count++ }
	}

	buf = make([]byte, 0, count * net.IPv4len)
	for _, v = range opt.value {
		v4 = v.To4()
		if v4 == nil { continue }
		buf = append(buf, v4...)
	}
	return buf
}

func (opt *Dhcp4OptString) Bytes() []byte {
	return []byte(opt.value)
}

func (opt *Dhcp4OptBytes) Bytes() []byte {
	return opt.value
}

func (opt *Dhcp4OptUint32) Bytes() []byte {
	var buf [4]byte
	binary.BigEndian.PutUint32(buf[:], opt.value)
	return buf[:]
}

func (opt *Dhcp4OptUint16) Bytes() []byte {
	var buf [2]byte
	binary.BigEndian.PutUint16(buf[:], opt.value)
	return buf[:]
}

func (opt *Dhcp4OptUint8) Bytes() []byte {
	return []byte{opt.value}
}

func Dhcp4OptMsgType(v uint8) Dhcp4Opt {
	return &Dhcp4OptUint8{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_MSG_TYPE}, value: v}
}

func Dhcp4OptSubnetMask(v net.IP) Dhcp4Opt {
	return &Dhcp4OptIp4Addr{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_SUBNET_MASK}, value: v}
}

func Dhcp4OptRouter(v net.IP) Dhcp4Opt {
	return &Dhcp4OptIp4Addr{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_ROUTER}, value: v}
}

func Dhcp4OptTimeServers(v []net.IP) Dhcp4Opt {
	return &Dhcp4OptIp4Addrs{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_TIME_SERVER}, value: v}
}

func Dhcp4OptDnsServers(v []net.IP) Dhcp4Opt {
	return &Dhcp4OptIp4Addrs{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_DNS_SERVER}, value: v}
}

func Dhcp4OptHostName(v string) Dhcp4Opt {
	return &Dhcp4OptString{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_DNS_SERVER}, value: v}
}

func Dhcp4OptReqIpaddr(v net.IP) Dhcp4Opt {
	return &Dhcp4OptIp4Addr{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_REQUESTED_IPADDR}, value: v}
}

func Dhcp4OptLeaseTime(v uint32) Dhcp4Opt {
	return &Dhcp4OptUint32{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_LEASE_TIME}, value: v}
}

func Dhcp4OptServerId(v net.IP) Dhcp4Opt {
	return &Dhcp4OptIp4Addr{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_SERVER_ID}, value: v}
}

func Dhcp4OptParamReqList(v []Dhcp4OptCode) Dhcp4Opt {
	return &Dhcp4OptBytes{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_PARAM_REQ_LIST}, value: v}
}

func Dhcp4OptErrorText(v string) Dhcp4Opt {
	return &Dhcp4OptString{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_ERROR_TEXT}, value: v}
}

func Dhcp4OptMaxMsgSize(v uint16) Dhcp4Opt {
	return &Dhcp4OptUint16{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_MAX_MSG_SIZE}, value: v}
}

func Dhcp4OptRenewalTime(v uint32) Dhcp4Opt {
	return &Dhcp4OptUint32{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_RENEWAL_TIME}, value: v}
}

func Dhcp4OptRebindingTime(v uint32) Dhcp4Opt {
	return &Dhcp4OptUint32{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_REBINDING_TIME}, value: v}
}

func Dhcp4OptClientId(v string) Dhcp4Opt {
	return &Dhcp4OptString{Dhcp4OptBase: Dhcp4OptBase{code: DHCP4_OPT_CLIENT_ID}, value: v}
}