#!/bin/bash
#
# Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@zubax.com>
#

HELP="Register slcan-enabled Serial-to-CAN adapters as network interfaces.
Usage:
    `basename $0` [options] <tty0> [[options] <tty1> ...]
First device will be mapped to the interface slcan0, second will be mapped to
slcan1, and so on. Keep in mind that the effect of this script is not
additive, i.e. all existing slcan interfaces will be removed and replaced with
new ones. The package 'can-utils' has to be installed in order to use slcan.

Options:
  -s<X> (where X is a number in range [1, 8]) Set CAN speed to:
      1 - 20  Kbps
      2 - 50  Kbps
      3 - 100 Kbps
      4 - 125 Kbps (UAVCAN recommended)
      5 - 250 Kbps (UAVCAN recommended)
      6 - 500 Kbps (UAVCAN recommended)
      7 - 800 Kbps
      8 - 1   Mbps (UAVCAN recommended, default)

Example:
    `basename $0` /dev/ttyUSB3 /dev/ttyUSB0 -s4 /dev/ttyACM0
The example above initializes:
    /dev/ttyUSB3 --> slcan0 @ 1Mbps
    /dev/ttyUSB0 --> slcan1 @ 1Mbps
    /dev/ttyACM0 --> slcan2 @ 125kbps"

function die() { echo $@ >&2; exit 1; }

if [ "$1" == '--help' ] || [ "$1" == '-h' ]; then echo "$HELP"; exit; fi

[ -n "$1" ] || die "Invalid usage. Use --help to get help."

[ "$(id -u)" == "0" ] || die "Must be root"

# ---------------------------------------------------------

function deinitialize() {
    echo "Terminating slcand..."
    slcand_kill_retries=10
    while killall slcand &> /dev/null
    do
        (( slcand_kill_retries -= 1 ))
        [[ "$slcand_kill_retries" > 0 ]] || die "Failed to kill slcand"
        sleep 1
    done
}

function handle_tty() {
    tty=$(readlink -f $1)
    tty=${tty/'/dev/'}
    iface="$IFACE_BASENAME$NEXT_IFACE_INDEX"

    stty -F /dev/$tty ispeed 3000000 ospeed 3000000 || return 1
    slcan_attach -f -o -s$SPEED_CODE /dev/$tty  || return 2

    slcand $tty || return 3
    sleep 1 # FIXME
    ifconfig $iface up || return 4

    NEXT_IFACE_INDEX=$((NEXT_IFACE_INDEX + 1))
}

NEXT_IFACE_INDEX=0
IFACE_BASENAME='slcan'
SPEED_CODE=8

deinitialize

while [ -n "$1" ]; do
    case $1 in
    -s[1-8])
        SPEED_CODE=${1:2}
        ;;
    -*)
        die "Invalid option: $1"
        ;;
    *)
        handle_tty $1 || die "Failed to configure the interface $1"
        ;;
    esac
    shift
done