//go:build darwin

package internal

import (
	"context"
	"errors"
	"net"
	"os"
	"syscall"
	"unsafe"
)

//go:linkname internetSocket net.internetSocket
func internetSocket(ctx context.Context, net string, laddr, raddr any, sotype, proto int, mode string, ctrlCtxFn func(context.Context, string, string, syscall.RawConn) error) (fd unsafe.Pointer, err error)

//go:linkname newIPConn net.newIPConn
func newIPConn(fd unsafe.Pointer) *net.IPConn

var (
	errUnknownNetwork = errors.New("unknown network type")
	errUnknownIface   = errors.New("unknown network interface")

	networkMap = map[string]string{
		"ip4:icmp": "udp4",
		"ip4:1":    "udp4",
		"ip6:icmp": "udp6",
		"ip6:58":   "udp6",
	}
)

func ListenICMP(network string, laddr string) (net.PacketConn, error) {
	if os.Getuid() == 0 { // root
		return net.ListenPacket(network, laddr)
	} else {
		if nw, ok := networkMap[network]; ok {
			proto := syscall.IPPROTO_ICMP
			if nw == "udp6" {
				proto = syscall.IPPROTO_ICMPV6
			}

			var ifIndex = -1
			if laddr != "" {
				la := net.ParseIP(laddr)
				if ifaces, err := net.Interfaces(); err == nil {
					for _, iface := range ifaces {
						addrs, err := iface.Addrs()
						if err != nil {
							continue
						}
						for _, addr := range addrs {
							if ipnet, ok := addr.(*net.IPNet); ok {
								if ipnet.IP.Equal(la) {
									ifIndex = iface.Index
									break
								}
							}
						}
					}
					if ifIndex == -1 {
						return nil, errUnknownIface
					}
				} else {
					return nil, err
				}
			}

			isock, err := internetSocket(context.Background(), nw, nil, nil, syscall.SOCK_DGRAM, proto, "listen",
				func(ctx context.Context, network, address string, c syscall.RawConn) error {
					if ifIndex != -1 {
						if proto == syscall.IPPROTO_ICMP {
							return c.Control(func(fd uintptr) {
								err := syscall.SetsockoptInt(int(fd), syscall.IPPROTO_IP, syscall.IP_BOUND_IF, ifIndex)
								if err != nil {
									return
								}
							})
						} else {
							return c.Control(func(fd uintptr) {
								err := syscall.SetsockoptInt(int(fd), syscall.IPPROTO_IPV6, syscall.IPV6_BOUND_IF, ifIndex)
								if err != nil {
									return
								}
							})
						}
					}
					return nil
				})
			if err != nil {
				panic(err)
			}
			return newIPConn(isock), nil
		} else {
			return nil, errUnknownNetwork
		}
	}
}