//go:build unix

package ping

import (
	"net"
	"net/netip"
	"os"
	"runtime"
	"syscall"

	"github.com/sagernet/sing/common/control"
	E "github.com/sagernet/sing/common/exceptions"
	M "github.com/sagernet/sing/common/metadata"

	"golang.org/x/sys/unix"
)

func connect(privileged bool, controlFunc control.Func, destination netip.Addr) (net.Conn, error) {
	var (
		network string
		fd      int
		err     error
	)
	if destination.Is4() {
		network = "ip4:icmp"
		if !privileged {
			fd, err = unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_ICMP)
		} else {
			fd, err = unix.Socket(unix.AF_INET, unix.SOCK_RAW, unix.IPPROTO_ICMP)
		}
	} else {
		network = "ip6:icmp"
		if !privileged {
			fd, err = unix.Socket(unix.AF_INET6, unix.SOCK_DGRAM, unix.IPPROTO_ICMPV6)
		} else {
			fd, err = unix.Socket(unix.AF_INET6, unix.SOCK_RAW, unix.IPPROTO_ICMPV6)
		}
	}
	if err != nil {
		return nil, E.Cause(err, "socket()")
	}
	file := os.NewFile(uintptr(fd), "datagram-oriented icmp")
	defer file.Close()
	err = unix.Connect(fd, M.AddrPortToSockaddr(netip.AddrPortFrom(destination, 0)))
	if err != nil {
		return nil, E.Cause(err, "connect()")
	}

	if destination.Is4() && (runtime.GOOS == "linux" || runtime.GOOS == "android") {
		//err = unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_RECVTOS, 1)
		//if err != nil {
		//	return nil, err
		//}
		err = unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_RECVTTL, 1)
		if err != nil {
			return nil, E.Cause(err, "setsockopt()")
		}
	}
	if destination.Is6() {
		err = unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_RECVHOPLIMIT, 1)
		if err != nil {
			return nil, E.Cause(err, "setsockopt()")
		}
		err = unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_RECVTCLASS, 1)
		if err != nil {
			return nil, E.Cause(err, "setsockopt()")
		}
	}

	conn, err := net.FileConn(file)
	if err != nil {
		return nil, err
	}
	if controlFunc != nil {
		var syscallConn syscall.RawConn
		syscallConn, err = conn.(syscall.Conn).SyscallConn()
		if err != nil {
			return nil, err
		}
		err = controlFunc(network, destination.String(), syscallConn)
		if err != nil {
			return nil, err
		}
	}
	return conn, nil
}