from nativesockets import getAddrString
from net import IpAddress, parseIpAddress, `$`
from posix import SockAddr, AF_INET, AF_INET6

type
  NetworkInterface* = object
    ipAddress*: IpAddress
    netMask*: IpAddress
    name*: string
    index*: cint
    flags*: cuint

  NetworkInterfaceError* = object of CatchableError

  Ifaddrs {.importc: "struct ifaddrs", pure, final,
            header: "<ifaddrs.h>".} = object
    ifa_next: ptr Ifaddrs     # Next item in list
    ifa_name: cstring         # Name of interface
    ifa_flags: cuint          # Flags from SIOCGIFFLAGS
    ifa_addr: ptr SockAddr    # Address of interface
    ifa_netmask: ptr SockAddr # Netmask of interface
    ifa_ifu: ptr SockAddr     # Broadcast / point-to-point address (we don't care about the union)
    ifa_data: pointer         # Address-specific data

proc getifaddrs(ifap: ptr ptr Ifaddrs): int {.header: "<ifaddrs.h>", importc: "getifaddrs".}
proc freeifaddrs(ifap: ptr Ifaddrs): void {.header: "<ifaddrs.h>", importc: "freeifaddrs".}
proc if_nametoindex(ifname: cstring): cuint {.header: "<net/if.h>", importc: "if_nametoindex".}

proc getNetworkInterface*(address: IpAddress): NetworkInterface =
  var interfaces: ptr Ifaddrs
  if getifaddrs(addr interfaces) != 0:
    raise newException(NetworkInterfaceError, "getifaddrs failed")
  var it = interfaces
  while it != nil:
    if it.ifa_addr != nil and
       (it.ifa_addr.sa_family.cint == AF_INET  or
        it.ifa_addr.sa_family.cint == AF_INET6) and
       $address == it.ifa_addr.getAddrString():
      result.ipAddress = address
      result.netMask = parseIpAddress(it.ifa_netmask.getAddrString())
      result.name = $it.ifa_name
      result.index = if_nametoindex(result.name).cint
      result.flags = it.ifa_flags
      break
    it = it.ifa_next
  freeifaddrs(interfaces)
  if result.name == "":
    raise newException(NetworkInterfaceError, "interface for given IP address not found")
  if result.index <= 0:
    raise newException(NetworkInterfaceError, "cannot get interface index")