#!/bin/bash
# I, Ian Kelling, follow the GNU license recommendations at
# https://www.gnu.org/licenses/license-recommendations.en.html. They
# recommend that small programs, < 300 lines, be licensed under the
# Apache License 2.0. This file contains or is part of one or more small
# programs. If a small program grows beyond 300 lines, I plan to switch
# its license to GPL.

# Copyright 2024 Ian Kelling

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# usage $0 [-c] [off]
# off:   Turn off static ip.
# -c    config only, don't tell networkmanager to change anything
# -f    force interface reup

if ! test "$BASH_VERSION"; then echo "error: shell is not bash" >&2; exit 1; fi
shopt -s inherit_errexit 2>/dev/null ||: # ignore fail in bash < 4.4
set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR

m() { printf "%s\n" "$*";  "$@"; }

## begin arg parsing ##

force=false
off=false
while [[ $1 ]]; do
  case $1 in
    -f)
      force=true
      ;;
    off)
      off=true
      ;;
    *)
      echo "$0: error unexpected argument: $1" >&2
      exit 1
      ;;
  esac
  shift
done

## end arg parsing ##


shopt -s nullglob

wiredx=1

# device that has an eth0, but we aren't using it because it is
# broken. We could just hardcode a mac comparison with `cat
# /sys/class/net/eth0/address` but this is cooler.
if [[ -e  /sys/class/net/eth0 ]]; then
  bus_info=$(ethtool -i eth0 | awk '$1 == "bus-info:" { print $2 }')
  if [[ $bus_info != usb* ]]; then
    wiredx=2
  fi
fi

eth_dev=eth$(( wiredx - 1 ))

nm_con=$(nmcli device show $eth_dev | \
           awk '$1 == "GENERAL.CONNECTION:" {out=$2; for(i=3;i<=NF;i++){out=out" "$i}; print out}' ||:)

if [[ ! $nm_con ]]; then
  nm_con="Wired connection $wiredx"
fi


con_exists=false
if nmcli con | grep -q "^$nm_con " &>/dev/null; then
  con_exists=true
fi

declare -a args
if $off; then

  if ! $con_exists; then
    echo "warning: no existing connection: $nm_con found in output of nmcli con"
    exit 0
  fi


  tmpstr=$(nmcli con show "$nm_con" 2>/dev/null | sort -r | awk '$1 == "ipv4.method:" || $1 == "ipv4.addresses:" || $1 == "ipv4.gateway:" || $1 == "ipv4.dns:" || $1 == "GENERAL.STATE:" {print $2}' )
  {
    read -r ipv4_method
    read -r ipv4_gateway
    read -r ipv4_dns
    read -r ipv4_addresses
    read -r state
  }<<<"$tmpstr"

  reup=false
  if [[ $state == activated ]]; then
    reup=true
  fi

  if [[ $ipv4_method != auto ]]; then
    args+=(ipv4.method auto)
  fi
  if [[ $ipv4_addresses != -- ]]; then
    args+=(-ipv4.addresses "$ipv4_addresses")
  fi
  if [[ $ipv4_dns != -- ]]; then
    args+=(-ipv4.dns "$ipv4_dns")
  fi
  if [[ $ipv4_gateway != -- ]]; then
    # undocumented in t11 man nmcli. guessed randomly
    args+=(ipv4.gateway 0.0.0.0)
  fi
  if (( ${#args[@]} >= 1 )); then
    m nmcli con mod "$nm_con" "${args[@]}"
    if $reup; then
      m nmcli con up "$nm_con"
    fi
  else
    echo "$0: found expected state, nothing to do."
  fi
  exit 0
fi


if [[ $(dig +short @10.2.0.1 -x 10.2.0.2 2>&1 ||:) == kd.b8.nz. ]] \
     && ip n show 10.2.0.1 | grep . &>/dev/null; then
  #  we are at_home=true

  while read -r ip_suf host mac; do
    if [[ ! $ip_suf || $ip_suf == \#* ]]; then
      continue
    fi
    if [[ $mac != usb ]]; then
      continue
    fi
    if [[ $host == ${HOSTNAME}c ]]; then

      ip=10.2.0.$ip_suf/16
      gateway=10.2.0.1
      dns=8.8.8.4,8.8.8.8
      break
    fi
  done </p/c/host-info

  if [[ ! $ip_suf ]]; then
    echo "$0: error: failed to find ${HOSTNAME}c ip suffix in /p/c/host-info"
    exit 1
  fi
else
  if ! type -p dig &>/dev/null; then
    apt-get install dig
  fi
  myip=$(dig +short @192.168.0.25 $HOSTNAME.office.fsf.org)
  if [[ ! $ip ]]; then
    echo "$0: error: didnt detect home network and failed to get office ip"
    exit 1
  fi
  dns=192.168.0.10,192.168.0.25
  gateway=192.168.0.1
  ip=$myip/24
fi

if ! $force && $con_exists; then
  current=$(nmcli con show "$nm_con" 2>/dev/null | sort -r | awk '$1 == "ipv4.method:" || $1 == "ipv4.addresses:" || $1 == "ipv4.gateway:" || $1 == "ipv4.dns:" {print $2}')
  expected="manual
$gateway
$dns
$ip"
  if [[ $current == "$expected" ]]; then
    echo "$0: found expected state, nothing to do."
    exit 0
  fi
fi

m nmcli con mod 'Wired connection 1' ipv4.method manual ipv4.addresses $ip ipv4.gateway $gateway ipv4.dns $dns

state=$(nmcli con show "$nm_con" 2>/dev/null | awk '$1 == "GENERAL.STATE:" {print $2}')
if [[ $state == activated ]]; then
  m nmcli con up "$nm_con"
fi


# example of down cli
#nmcli con mod 'Wired connection 1' ipv4.method auto -ipv4.addresses 10.2.0.9/16 ipv4.gateway 0.0.0.0 -ipv4.dns "8.8.8.4,8.8.8.8"


# FYI: the result of running, for example
# nmcli con mod "Wired connection 1" \
  #         ipv4.method manual \
  #       ipv4.addresses "10.2.0.23/24" \
  #       ipv4.gateway "10.2.0.1" \
  #       ipv4.dns "8.8.8.4,8.8.8.8"

# creates a fille named "/etc/NetworkManager/system-connections/Wired connection 1.nmconnection",
# below.
#
# The nmcli man page says you should just edit files in that dir and
# then run nmcli con reload to reread them all to load your changes, but
# I've found that to be unreliable, the systemd journal would say
# something like "reload happened" then nothing would change in the
# connect that the file clearly modifies, so I switched over to using
# the command line and just ignoring those files.
#
# I see no reason to keep the same file name, or a bunch of
# setting that seem irrelevant, and empty sections don't seem to do
# anything according to the man page.
#

# [connection]
# id=Wired connection 1
# uuid=b0fb7694-dfe6-31a1-81fa-7c17b61515a7
# type=ethernet
# interface-name=eth1
# timestamp=1715728264

# [ethernet]

# [ipv4]
# address1=10.2.0.23/16,10.2.0.1
# dns=8.8.8.4;8.8.8.8;
# method=manual

# [ipv6]
# addr-gen-mode=stable-privacy
# method=auto

# [proxy]