#! /bin/bash
# vim: set tabstop=4 shiftwidth=4 expandtab filetype=sh:

ttyUSB=

pkill -f "sleep 86399"

if [[ $(grep -e '-scanttyUSB' <<< "$*") ]]; then
    # called with -scantty isntead of device name?
    # echo "-scantty mode"

    # if upper USB port
    if [[ -c /dev/ttyUSBupper ]]; then
        ttyUSB=ttyUSBupper

    # if hub in upper port, use highest numbered port on hub
    elif [[ $(ls -1 /dev/ttyUSBupper_hub* 2> /dev/null | wc -l) -gt 0 ]]; then
        ttyUSB=$(ls -1 /dev/ttyUSBupper_hub* 2> /dev/null | tail -1 | cut -c 6-)

    # if hub in lower port with multiple adapters, use highest numbered port on hub
    elif [[ $(ls -1 /dev/ttyUSBlower_hub* 2> /dev/null | wc -l) -gt 1 ]]; then
        ttyUSB=$(ls -1 /dev/ttyUSBlower_hub* 2> /dev/null | tail -1 | cut -c 6-)

    # no port found eligible for getty
    else
        # echo "scantty no devices eligible: sleeping"
        sleep 86399
    fi

    # echo "result:$ttyUSB"
elif [[ $(grep -o 'ttyUSB[^ ]*' <<< "$*") ]]; then
    # echo "device specified"
    # if specified USB device name is found
    ttyUSB=$(grep -o 'ttyUSB[^ ]*' <<< "$*")
else
    # echo "specified device failed: sleeping"
    sleep 86399
fi

if [[ -c /dev/$ttyUSB && ! $(ps aux | grep "[g]etty.*$ttyUSB") ]]; then
    # if adapter seems to exist and doesn't already have a getty,
    #   kill all USB gettys and start the getty, otherwise do nothing
    pkill -f "/sbin/getty.*ttyUSB"
    exec /sbin/getty $(sed "s/-scanttyUSB/$ttyUSB/" <<< "$@");
else
    # echo "getty already running or doesn't exist: sleeping"
    sleep 86399
fi