#!/system/xbin/bash
#
# Copyright (C) 2017 Jeremy Rand <jeremy@veclabs.net>
# Partially based on code by Wolfgang Wiedmeyer <wolfgit@wiedmeyer.de> and Filippo Fil Bergamo
#
# This file is part of "SlightlyBetterAirplaneMode", a set of shell scripts to shut off
# the Samsung phone modem without trusting the non-free modem firmware.
#
# SlightlyBetterAirplaneMode is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# SlightlyBetterAirplaneMode is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

set -euf -o pipefail

usage()
{
	echo "Usage: modem.sh [on|off]"
	echo "Examples:"
	echo "modem.sh off"
	echo "|-> disable the modem"
	echo "    and reboot"
	echo "modem.sh on"
	echo "|-> enable the modem"
	echo "    and reboot"
	exit 1
}

check_permissions()
{
	modem_command="$1"
	root_access="$(getprop persist.sys.root_access)"
	uid="$(id -u)"

	# 0: Root access: Disabled, 2: Root access: ADB only
	#    For both the terminal application and ADB we have something
	#    like that:
	#        shell@i9100:/ $ su
	#        255|shell@i9100:/ $
	# 1: Root access: Apps only
	#    From ADB:
	#        shell@i9100:/ $ su
	#        Permission denied
	#        1|shell@i9100:/ $
	#    From the terminal application
	#        u0_a51@i9100:/ $ su
	#        root@i9100:/ #
	if [ "${uid}" != "0" ] ; then
	    echo ""
	    echo "This script requires root."
	    echo "To give it root:"
	    case "${root_access}" in
		"0"|"1"|"2")
		    echo "- Go in Settings"
		    echo "- Go in Developer options"
		    echo "- Select Root access"
		    echo "- Set it to \"Apps and ADB\""
		    ;;
	    esac
	    echo "- Run these 2 commands:"
	    echo "  su"
	    echo "  modem.sh ${modem_command}"
	    exit 1
	fi
}

modem()
{
	command="$1"

	check_permissions "${command}"

	echo "Remounting system partition as writable..."
	mount -o rw,remount /system

	if [ "${command}" = "on" ] ; then
		echo "Enabling RIL..."
		mv /system/lib/libsamsung-ril.so.disabled \
		   /system/lib/libsamsung-ril.so || \
		   echo 'RIL was already enabled.'
	elif [ "${command}" = "off" ] ; then
		echo "Disabling RIL..."
		mv /system/lib/libsamsung-ril.so \
		   /system/lib/libsamsung-ril.so.disabled || \
		   echo 'RIL was already disabled.'
	fi

	echo "Syncing filesystem..."
	sync
	sync

	echo "Remounting system partition as read-only..."
	mount -o ro,remount /system

	echo "Syncing filesystem..."
	sync
	sync

	am force-stop org.smssecure.smssecure
	# https://android.stackexchange.com/a/139139
	echo "Modem will be disabled after we reboot now..."
	am start -a android.intent.action.REBOOT
}

if [ $# -ne 1 ] ; then
	usage
fi

if [ "$1" = "on" -o "$1" = "off" ] ;then
	modem "$1"
else
	usage
fi