#!/bin/bash
#
# Copyright (C) 2017 Genymobile
#
# 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.

set -e # fail on error

ADB=adb
JAVA=java

syntax() {
    echo "Syntax: $0 (install|uninstall|rt|start|stop|relay) ..." >&2
    echo
    echo "  $0 install [serial]"
    echo "      Install the client on the Android device and exit."
    echo "      If several devices are connected via adb, then serial must be"
    echo "      specified."
    echo
    echo "  $0 uninstall [serial]"
    echo "      Uninstall the client from the Android device and exit."
    echo "      If several devices are connected via adb, then serial must be"
    echo "      specified."
    echo
    echo "  $0 rt [serial] [-d DNS[,DNS2,...]]"
    echo "      Enable reverse tethering for exactly one device:"
    echo "        - install the client if necessary;"
    echo "        - start the client;"
    echo "        - start the relay server;"
    echo "        - on Ctrl+C, stop both the relay server and the client."
    echo
    echo "  $0 start [serial] [-d DNS[,DNS2,...]]"
    echo "      Start a client on the Android device and exit."
    echo "      If several devices are connected via adb, then serial must be"
    echo "      specified."
    echo "      If -d is given, then make the Android device use the specified"
    echo "      DNS server(s). Otherwise, use 8.8.8.8 (Google public DNS)."
    echo "      If the client is already started, then do nothing, and ignore"
    echo "      DNS servers parameter."
    echo "      To use the host 'localhost' as DNS, use 10.0.2.2."
    echo
    echo "  $0 stop [serial]"
    echo "      Stop the client on the Android device and exit."
    echo "      If several devices are connected via adb, then serial must be"
    echo "      specified."
    echo
    echo "  $0 relay"
    echo "      Start the relay server in the current terminal."
    exit 1
}

adbs() {
    local serial="$1"
    cmd="'$ADB'"
    [[ "$serial" ]] && cmd+=" -s '$serial'"
    echo "$cmd"
}

evalv() {
    echo "$@"
    eval "$@"
}

locate_file() {
    for file in "$@"
    do
        if [[ -r "$file" ]]
        then
            echo "$file"
            return
        fi
    done
    # not found, use the name having the highest priority
    echo "$1"
}

get_relay_path() {
    locate_file relay.jar \
                relay/build/libs/relay.jar
}

get_apk_path() {
    locate_file gnirehtet.apk \
                app/build/outputs/apk/gnirehtet-release.apk \
                app/build/outputs/apk/gnirehtet-debug.apk
}

apk_install() {
    echo 'Installing gnirehtet...'
    local serial="$1"
    evalv $(adbs "$serial") install -r "$(get_apk_path)"
}

apk_require_installed() {
    if [[ ! "$(eval $(adbs "$serial") shell pm list packages com.genymobile.gnirehtet)" ]]
    then
        apk_install
        # wait a bit after the app is installed so that intent actions are correctly registered
        sleep 0.5
    fi
}

apk_uninstall() {
    echo 'Uninstalling gnirehtet...'
    local serial="$1"
    evalv $(adbs "$serial") uninstall com.genymobile.gnirehtet
}

start() {
    echo 'Starting gnirehtet...'
    local dns=
    eval set -- $(getopt d: "$@")
    while true;
    do
        case "$1" in
            -d) dns="$2"; shift 2;;
            --) shift; break;;
            *)  break;;
        esac
    done
    local serial="$1"
    evalv $(adbs "$serial") reverse tcp:31416 tcp:31416
    [[ $? = 0 ]] || return
    local dparam=
    [[ "$dns" ]] && dparam=" --esa dnsServers $dns"
    evalv $(adbs "$serial") shell am startservice -a com.genymobile.gnirehtet.START$dparam
}

stop() {
    echo 'Stopping gnirehtet...'
    local serial="$1"
    evalv $(adbs "$serial") shell am startservice -a com.genymobile.gnirehtet.STOP
}

relay() {
    evalv "'$JAVA'" -jar "$(get_relay_path)"
}

case "$1" in
install)
    shift
    apk_install "$@";;
uninstall)
    shift
    apk_uninstall "$@";;
start)
    shift
    start "$@";;
stop)
    shift
    stop "$@";;
relay)
    shift
    relay "$@";;
rt)
    shift
    apk_require_installed
    trap stop INT
    start "$@"
    relay;;
*)
    syntax;;
esac