package host

import (
	"lux/proto"
	"net"
	"net/netip"
	"strconv"
	"strings"
)

// Option containing all network interfaces of host (excluding loopbacks)

// IPv6 GUA
// IPv6 ULA
// IPv6 LL
// IPv4

type LuxNetAddrType int

const (
	LuxNetAddrType4    = 0
	LuxNetAddrType6LL  = 1
	LuxNetAddrType6ULA = 2
	LuxNetAddrType6GUA = 3
)

func (addrType LuxNetAddrType) String() string {
	switch addrType {
	case LuxNetAddrType4:
		return "ip4"
	case LuxNetAddrType6LL:
		return "ip6ll"
	case LuxNetAddrType6ULA:
		return "ip6ula"
	case LuxNetAddrType6GUA:
		return "ip6gua"
	default:
		return strconv.Itoa(int(addrType))
	}
}

type LuxNetAddr struct {
	Type LuxNetAddrType
	Addr netip.Addr
}

func (addr *LuxNetAddr) Read(rd *proto.LuxBuffer) error {
	addrType, err := rd.ReadUint16()
	if err != nil {
		return err
	}
	addr.Type = LuxNetAddrType(addrType)

	ipAddr, err := rd.ReadIP()
	if err != nil {
		return err
	}
	addr.Addr = ipAddr

	return nil
}

func (addr *LuxNetAddr) Write(wd *proto.LuxBuffer) {
	wd.WriteUint16(uint16(addr.Type))
	wd.WriteIP(addr.Addr)
}

type LuxNetInterface struct {
	Name  string
	Index int
	Addrs []LuxNetAddr
}

func NewLuxNetInterface() LuxNetInterface {
	return LuxNetInterface{
		Addrs: make([]LuxNetAddr, 0),
	}
}

func parseNetlinkIp(addr string) string {
	if strings.ContainsRune(addr, '/') {
		return strings.Split(addr, "/")[0]
	}

	return addr
}

func (luxNet *LuxNetInterface) FromNetlink(netif *net.Interface) error {
	luxNet.Name = netif.Name
	luxNet.Index = netif.Index

	// enumerate interface ips
	addrs, err := netif.Addrs()
	if err != nil {
		return err
	}

	for _, addr := range addrs {
		ip := net.ParseIP(parseNetlinkIp(addr.String()))
		if ip == nil {
			return err
		}

		luxAddr := LuxNetAddr{}
		if ip.IsLoopback() {
			continue // loopbacks are useless to LUX
		} else if ip.To4() == nil {
			// got IPv6
			if ip.IsLinkLocalUnicast() {
				luxAddr.Type = LuxNetAddrType6LL
			} else if ip[0] == 0xFD || ip[0] == 0xFC {
				// ULA - fc00::/7 with L = 1 -> fd00::/8,
				// tho fc L 0 is not defined we still gonna assume its ULA
				luxAddr.Type = LuxNetAddrType6ULA
			} else {
				// anything else is global unicast
				luxAddr.Type = LuxNetAddrType6GUA
			}
		} else {
			// got IPv4
			luxAddr.Type = LuxNetAddrType4
		}

		luxAddr.Addr = proto.LuxProtoIPToAddr(ip)

		luxNet.Addrs = append(luxNet.Addrs, luxAddr)
	}

	return nil
}

func (netif *LuxNetInterface) Read(rd *proto.LuxBuffer) error {
	name, err := rd.ReadString()
	if err != nil {
		return err
	}
	netif.Name = name

	idx, err := rd.ReadUint16()
	if err != nil {
		return err
	}
	netif.Index = int(idx)

	addrNum, err := rd.ReadUint16()
	if err != nil {
		return err
	}

	for i := 0; i < int(addrNum); i++ {
		addr := LuxNetAddr{}
		if addr.Read(rd) != nil {
			return err
		}

		netif.Addrs = append(netif.Addrs, addr)
	}

	return nil
}

func (netif *LuxNetInterface) Write(wd *proto.LuxBuffer) {
	wd.WriteString(netif.Name)
	wd.WriteUint16(uint16(netif.Index))

	wd.WriteUint16(uint16(len(netif.Addrs)))
	for _, addr := range netif.Addrs {
		addr.Write(wd)
	}
}

type LuxOptionNetIf struct {
	Interfaces map[string]*LuxNetInterface
}

func NewLuxOptionNetIf() LuxOptionNetIf {
	return LuxOptionNetIf{
		Interfaces: make(map[string]*LuxNetInterface),
	}
}

func (opt *LuxOptionNetIf) EnumerateNetlink() error {
	ifaces, err := net.Interfaces()
	if err != nil {
		return err
	}

	for _, iface := range ifaces {
		netif := NewLuxNetInterface()
		if err := netif.FromNetlink(&iface); err != nil {
			return nil
		}

		if len(netif.Addrs) > 0 {
			// only add if we got atleast 1 ip, since we might want to skip
			// netif loopback that has no IP because we skip one in FromNetlink
			opt.Interfaces[netif.Name] = &netif
		}
	}

	return nil
}

func (opt *LuxOptionNetIf) Read(rd *proto.LuxBuffer) error {
	ifNum, err := rd.ReadUint16()
	if err != nil {
		return err
	}

	for i := 0; i < int(ifNum); i++ {
		netif := NewLuxNetInterface()
		if err := netif.Read(rd); err != nil {
			return err
		}

		opt.Interfaces[netif.Name] = &netif
	}

	return nil
}

func (opt *LuxOptionNetIf) Write(wd *proto.LuxBuffer) {
	wd.WriteUint16(uint16(len(opt.Interfaces)))
	for _, netif := range opt.Interfaces {
		netif.Write(wd)
	}
}

func (*LuxOptionNetIf) Type() LuxOptionType {
	return LuxOptionTypeNetIf
}