#!/bin/sh

# Copyright 2018 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# Set the APN to be used when making connections on a cellular service.

PROGRAM="$(basename "$0")"
FLAGS_HELP="Usage:
  ${PROGRAM}
  ${PROGRAM} [-n <network_id>] [-u <username] [-p <password] <apn>
  ${PROGRAM} -c

Set the APN to use when connecting to the network specified by <network-id>.
If <network-id> is not specified, use the network-id of the currently
registered network.

The -c option clears the APN to be used, so that the default APN will be used
instead.
"

FLIMFLAM=org.chromium.flimflam
IMANAGER=${FLIMFLAM}.Manager
ISERVICE=${FLIMFLAM}.Service
APN_PROPERTY=Cellular.APN
LAST_GOOD_APN_PROPERTY=Cellular.LastGoodAPN

SET_APN_HELPER=$(find /usr/lib*/shill/shims/ -name set-apn-helper -type f | \
    head -1)
if [ -z "${SET_APN_HELPER}" ] ; then
  echo "set-apn-helper script was not found!"
  exit 1
fi

usage() {
  echo "$*"
  echo
  echo "${FLAGS_HELP}"
  exit 1
}

dbus() {
  local object="$1"
  local method="$2"
  shift 2

  dbus-send --system --print-reply --fixed --dest="${FLIMFLAM}" \
    "${object}" "${method}" "$@"
}

get_apn_info() {
  local service="$1"
  local property="$2"

  dbus "${service}" "${ISERVICE}.GetProperties" 2>/dev/null \
    | sed -n "/${property}/s/.*\///p"
}

display_apn() {
  local service="$1"
  local apn

  apn="$(get_apn_info "${service}" "${LAST_GOOD_APN_PROPERTY}")"
  if [ -n "${apn}" ]; then
    echo "Last good APN: ${apn}"
    exit 0
  fi

  apn="$(get_apn_info "${service}" "${APN_PROPERTY}")"
  if [ -n "${apn}" ]; then
    echo "User specified APN: ${apn}"
    exit 0
  fi

  echo "No APN."
  exit 0
}

set_apn() {
  local service="$1"
  local apn="$2"
  local network_id="$3"
  local username="$4"
  local password="$5"
  local args="apn,${apn},network_id,${network_id}"

  if [ -n "${username}" ]; then
    args="${args},username,${username}"
  fi

  if [ -n "${password}" ]; then
    args="${args},password,${password}"
  fi

  echo "Setting APN \"${apn}\" for network ID ${network_id} for service ${service}"
  ${SET_APN_HELPER} "${service}" "${APN_PROPERTY}" "${args}"
}

clear_apn() {
  local service="$1"

  echo "Clearing APN for service ${service}"
  dbus "${service}" "${ISERVICE}.ClearProperty" "string:${APN_PROPERTY}"
}

get_services() {
  dbus / "${IMANAGER}.GetProperties" 2>/dev/null \
    | sed -n "/\/Services\//{s/.* //p}"
}

get_service_property() {
  local service="$1"
  local property="$2"

  dbus "${service}" "${ISERVICE}.GetProperties" 2>/dev/null \
    | sed -n "/\/${property}/{s/.* //p}"
}

get_first_cellular_service() {
  local service
  local service_type

  for service in $(get_services); do
    service_type="$(get_service_property "${service}" Type)"
    if [ "${service_type}" = "cellular" ]; then
      echo "${service}"
      break
    fi
  done
}

get_cellular_service_network_id() {
  local service="$1"
  get_service_property "${service}" "Cellular.ServingOperator\/[0-9]\/code"
}

FLAGS_network_id=
FLAGS_username=
FLAGS_password=
FLAGS_clear=0
while getopts ":n:u:p:c" flag; do
  case ${flag} in
    n) # Network ID.
      FLAGS_network_id="${OPTARG}"
      ;;
    u) # Username.
      FLAGS_username="${OPTARG}"
      ;;
    p) # Password.
      FLAGS_password="${OPTARG}"
      ;;
    c)
      FLAGS_clear=1
      ;;
    *)
      echo "${FLAGS_HELP}"
      exit 1
      ;;
  esac
done

service="$(get_first_cellular_service)"
if [ -z "${service}" ]; then
  echo "No cellular service exists."
  exit 1
fi

if [ $# -lt 1 ]; then
  display_apn "${service}"
fi

network_id="${FLAGS_network_id}"
if [ -z "${FLAGS_network_id}" ]; then
  network_id="$(get_cellular_service_network_id "${service}")"
  if [ -z "${network_id}" ]; then
    echo "Cannot determine network ID. Use the -n flag to specify it."
    exit 1
  fi
fi

if [ "${FLAGS_clear}" -ne 0 ]; then
  if [ $# -lt 1 ]; then
    usage "The APN must be specified."
  elif [ $# -gt 1 ]; then
    usage "Too many arguments."
  fi
  set_apn "${service}" "$1" "${network_id}" "${FLAGS_username}" "${FLAGS_password}"
else
  if [ $# -ne 0 ]; then
    usage "Too many arguments."
  fi
  clear_apn "${service}"
fi