#!/bin/bash

function usage() {
    echo "SYNOPSYS
    $0 [OPTIONS]
DESCRIPTION
    Spawn TCP tunnels between your computer and a remote SSH server. If the
    connection fail for some reason, the script will try to re-create the
    tunnels automatically every TIMEOUT seconds.
OPTIONS
    -S,--server=HOST
        Set the tunnel host. HOST can be either the IP or hostname of the
        server to tunnel to, as seen from the ssh host.

    -t, --tunnel=TUNNELPORT
        Specify the ports to tunnel.

    -i, --interface=IF
        Specify the interface to listen on.

    -H,--host=SSHHOST
        Set the ssh host. SSHHOST can be either the full hostname as you would
        specify it on the ssh command-line (e.g. user@example.com or hostname
        if it is set up in your ssh config).

    -p, --port=SSHPORT
        Set the ssh remote port if different from the default.

    -f
        Fork the script to the background.

    -h,--help
        Print this help and exit.
"
}

# Help argument
if [[ " $@" = *" -h"* || " $@" = *" --help"* ]]; then
    usage
    exit 0
fi

#if [[ -z "$@" || " $@" != *" --ok"* ]]; then
#    echo 'This script will only do something if `--ok` is provided'
#    echo ''
#    usage
#    echo ''
#    echo 'Nothing has been done. Exiting.'
#    exit 1
#fi

# Logfile location
# comment to use stdout/stderr
LOGFILE=proxy.log
LOGFILE_ERR=proxy.log

# Local bind address
#   - Use 127.0.0.1 for local computer only;
#   - Use 0.0.0.0 to give access to other computers (but be careful who can
#   reach your computer in that case, if you do not have a firewall, your LAN
#   (at least) normally has access to all your ports (most routers, through
#   NAT, provide basic firewall functionality))
#LOCAL_BIND_ADDR=0.0.0.0
LOCAL_BIND_ADDR=127.0.0.1

# License host and ports
REMOTE_LICENSE_HOST=licence.inl90.ec-lyon.fr
DASHBOARD_PORT=8095
FLEX_PORT=27011
LUMERICAL_VENDOR_PORT=42128

# ssh host
HOST=sshgate

# set default log to stdout/stderr
LOGFILE=${LOGFILE:-/dev/stdout}
LOGFILE_ERR=${LOGFILE_ERR:-/dev/stderr}

function start_and_monitor_tunnels() {
    # This function takes port numbers as arguments and creates as many TCP
    # tunnels like so:
    #   LOCAL_BIND_ADDR:$port <--> HOST <--> REMOTE_LICENSE_HOST:$port
    # If the tunnel fails or ssh exits, we either:
    #   - try again after a timeout if exit code is not 0
    #   - exit if exit code is 0
    # NOTE: for now we just **always** try again after timeout
    local ports=$@
    local timeout_sec=10

    declare -a ssh_tunnel_opt
    for port in ${ports}; do
        ssh_tunnel_opt+=("-L")
        ssh_tunnel_opt+=("${LOCAL_BIND_ADDR}:${port}:${REMOTE_LICENSE_HOST}:${port}")
    done

    while true; do
        # Try establishing the tunnel
        echo "Starting tunnel for ports ${ports[@]}"
        ssh -N \
            ${ssh_tunnel_opt[@]} \
            -o "ServerAliveInterval 10" \
            -o "ServerAliveCountMax 3" \
            -o "ExitOnForwardFailure yes" \
            ${HOST} &
        local pid="$!"
        # make sure to kill ssh when killed/parent exits
        trap "kill '$pid'" EXIT
        wait

        local exit_code="$?"
        echo "ssh exited with exit code ${exit_code}"
        #if [[ ${exit_code} != 0 ]]; then
        if true; then
            # If ssh exited with non-zero code, wait a bit and retry
            echo "restarting in ${timeout_sec}s..."
            sleep ${timeout_sec}
        else
            echo "exiting."
            return 0
        fi
    done
}

# Start the tunnels and redirect outputs
echo "Setting up tunnels.
Logs will be redirected to:
    stdout --> ${LOGFILE}
    stderr --> ${LOGFILE_ERR}
"

# In the following block, the following redirections are set up:
#   - 777 goes to stdout of current script (and not global /dev/stdout)
#   - 1 goes to $LOGFILE
#   - 2 goes to $LOGFILE_ERR
{
    # Enable trace
    set -x

    # Set up CTRL-C callback (write to stdout of script, not log)
    trap_ctrl_c_callback="
        echo 'Interrupt signal received, exiting...' 1>&777
        exit 130
    "
    trap "${trap_ctrl_c_callback}" SIGINT

    ports=(${DASHBOARD_PORT} ${FLEX_PORT} ${LUMERICAL_VENDOR_PORT})
    start_and_monitor_tunnels ${ports[@]}

} 777>&1 1>>${LOGFILE} 2>>${LOGFILE_ERR}