#!/usr/bin/env bash

# Taken from: https://github.com/elitak/nixos-infect
set -e -o pipefail

makeNetworkingConf() {
    # XXX It'd be better if we used procfs for all this...
    local IFS=$'\n'
    eth0_name=$(ip address show | grep '^2:' | awk -F': ' '{print $2}')
    eth0_ip4s=$(ip address show dev "$eth0_name" | grep 'inet ' | sed -r 's|.*inet ([0-9.]+)/([0-9]+).*|{ address="\1"; prefixLength=\2; }|')
    eth0_ip6s=$(ip address show dev "$eth0_name" | grep 'inet6 ' | sed -r 's|.*inet6 ([0-9a-f:]+)/([0-9]+).*|{ address="\1"; prefixLength=\2; }|' || true)
    gateway=$(ip route show dev "$eth0_name" | grep default | sed -r 's|default via ([0-9.]+).*|\1|')
    gateway6=$(ip -6 route show dev "$eth0_name" | grep default | sed -r 's|default via ([0-9a-f:]+).*|\1|' || true)
    ether0=$(ip address show dev "$eth0_name" | grep link/ether | sed -r 's|.*link/ether ([0-9a-f:]+) .*|\1|')

    eth1_name=$(ip address show | grep '^3:' | awk -F': ' '{print $2}') || true
    if [ -n "$eth1_name" ]; then
        eth1_ip4s=$(ip address show dev "$eth1_name" | grep 'inet ' | sed -r 's|.*inet ([0-9.]+)/([0-9]+).*|{ address="\1"; prefixLength=\2; }|')
        eth1_ip6s=$(ip address show dev "$eth1_name" | grep 'inet6 ' | sed -r 's|.*inet6 ([0-9a-f:]+)/([0-9]+).*|{ address="\1"; prefixLength=\2; }|' || true)
        ether1=$(ip address show dev "$eth1_name" | grep link/ether | sed -r 's|.*link/ether ([0-9a-f:]+) .*|\1|')
        interfaces1=$(
            cat <<EOF
      $eth1_name = {
        ipv4.addresses = [$(for a in "${eth1_ip4s[@]}"; do echo -n "
          $a"; done)
        ];
        ipv6.addresses = [$(for a in "${eth1_ip6s[@]}"; do echo -n "
          $a"; done)
        ];
        };
EOF
        )
        extraRules1="ATTR{address}==\"${ether1}\", NAME=\"${eth1_name}\""
    else
        interfaces1=""
        extraRules1=""
    fi

    readarray nameservers < <(grep ^nameserver /etc/resolv.conf | sed -r \
        -e 's/^nameserver[[:space:]]+([0-9.a-fA-F:]+).*/"\1"/' \
        -e 's/127[0-9.]+/8.8.8.8/' \
        -e 's/::1/8.8.8.8/')

    if [[ $eth0_name == eth* ]]; then
        predictable_inames="usePredictableInterfaceNames = lib.mkForce false;"
    else
        predictable_inames="usePredictableInterfaceNames = lib.mkForce true;"
    fi
    cat <<EOF
{ lib, ... }: {
  # This file was populated at runtime with the networking
  # details gathered from the active system.
  networking = {
    nameservers = [ ${nameservers[@]} ];
    defaultGateway = "${gateway}";
    defaultGateway6 = {
      address = "${gateway6}";
      interface = "${eth0_name}";
    };
    dhcpcd.enable = false;
    $predictable_inames
    interfaces = {
      $eth0_name = {
        ipv4.addresses = [$(for a in "${eth0_ip4s[@]}"; do echo -n "
          $a"; done)
        ];
        ipv6.addresses = [$(for a in "${eth0_ip6s[@]}"; do echo -n "
          $a"; done)
        ];
        ipv4.routes = [ { address = "${gateway}"; prefixLength = 32; } ];
        ipv6.routes = [ { address = "${gateway6}"; prefixLength = 128; } ];
      };
      $interfaces1
    };
  };
  services.udev.extraRules = ''
    ATTR{address}=="${ether0}", NAME="${eth0_name}"
    $extraRules1
  '';
}
EOF
}

makeNetworkingConf

# vim: ft=sh