#!/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

[[ $EUID == 0 ]] || exec sudo -E "${BASH_SOURCE[0]}" "$@"

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

## begin arg parsing ##

force=false
conf_only=false
comment='# iank file id: ethusb-dhcp-v1'
off=false
while [[ $1 ]]; do
  case $1 in
    -c)
      conf_only=true
      ;;
    -f)
      force=true
      ;;
    off)
      off=true
      comment='# iank file id: ethusb-static-v1'
      ;;
    *)
      echo "$0: error unexpected argument: $1" >&2
      exit 1
      ;;
  esac
  shift
done

## end arg parsing ##


shopt -s nullglob

# we already configured the interface once, afterwards, comment and
# uncomment to enable/disable. This makes it so we don't depend on /p
# being mounted.

conf=/etc/NetworkManager/system-connections/ethusb-static.nmconnection
if ! $force && [[ -s $conf ]] && grep -qFx "$comment" $conf; then
  # we already ran successfully in the past to set things this way, so
  # do nothing.
  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 [[ $mac != usb ]]; then
      continue
    fi
    if [[ $host == ${HOSTNAME}c ]]; then

      net_info="address1=10.2.0.$ip_suf/16,10.2.0.1
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 ${HOSTNAME}c ip suffix in /p/c/host-info"
    exit 1
  fi
else
  if ! type -p dig &>/dev/null; then
    apt-get install dig
  fi
  ip=$(dig +short @192.168.0.25 $HOSTNAME.office.fsf.org)
  net_info="address1=$ip/24,192.168.0.1
dns=192.168.0.10;192.168.0.25;"
fi

wiredx=

# 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

ethx=$(( wiredx - 1 ))



uuid=$(nmcli con show "Wired connection $wiredx" 2>/dev/null | awk '$1 == "connection.uuid:" {print $2}' ||:)
if [[ ! $uuid ]]; then
  # just a uuid that nm generated for me at some point
  uuid=0da4c614-6a3c-3ad2-8d4b-c6eebe0814c3
fi


# This template is the result of running, for example
# nmcli con mod "Wired connection 1" \
  #       ipv4.addresses "10.2.0.23/24" \
  #       ipv4.gateway "10.2.0.1" \
  #       ipv4.dns "8.8.8.4,8.8.8.8"

# which creates a fille named "Wired connection 1.nmconnection",
# below. 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 2
# 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]

{
  cat <<EOF
[connection]
id=Wired connection $wiredx
uuid=$uuid
type=ethernet
interface-name=eth$ethx

[ipv4]
EOF
  if $off; then
    cat <<'EOF'
method=auto
EOF
  else
    cat <<EOF
$net_info
method=manual
EOF
  fi
} | install -T -m0600 /dev/stdin $conf

if ! $conf_only; then
  state=$(nmcli con show $uuid 2>/dev/null | awk '$1 == "GENERAL.STATE:" {print $2}' ||:)

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

  m nmcli con reload

  if $reup; then
    m nmcli con down $uuid
    m nmcli con up $uuid
  fi
fi

if ! grep -F "$comment" $conf; then
  printf "%s\n" "$comment" >>$conf
fi