#!/bin/bash
stty -F /dev/ttyUSB0 115200 cs8 -cstopb -parenb -icanon min 1 time 1

# This script depends on the program xdotool to be installed.
# On Debian and probably ubuntu, it can be installed with:
# sudo apt install xdotool

USB_DEV="/dev/ttyUSB0"
JOY_BUTTON=1
JOY_UP=1
JOY_DOWN=1
JOY_LEFT=1
JOY_RIGHT=1

PREV_BUTTON=1
PREV_UP=1
PREV_DOWN=1
PREV_LEFT=1
PREV_RIGHT=1

KEY_BUTTON=q
KEY_UP=w
KEY_DOWN=s
KEY_LEFT=a
KEY_RIGHT=d

# All input in this script is read from $USB_DEV (defined above)
(
while :; do
	read LINE
	# If we have received 5 chars in a line, it is assumed correct
	if [ ${#LINE} = 5 ]; then
		# Split the line up into the different directions and button
		JOY_BUTTON=${LINE:0:1}
		JOY_UP=${LINE:4:1}
		JOY_DOWN=${LINE:3:1}
		JOY_LEFT=${LINE:2:1}
		JOY_RIGHT=${LINE:1:1}

		# Only change keypress if read value is different than last time
		if [ $JOY_BUTTON -ne $PREV_BUTTON ]; then
			PREV_BUTTON=$JOY_BUTTON
			if [ $JOY_BUTTON = 0 ]; then
				xdotool keydown $KEY_BUTTON
			else
				xdotool keyup $KEY_BUTTON
			fi
		fi

		if [ $JOY_UP -ne $PREV_UP ]; then
			PREV_UP=$JOY_UP
			if [ $JOY_UP = 0 ]; then
				xdotool keydown $KEY_UP
			else
				xdotool keyup $KEY_UP
			fi
		fi

		if [ $JOY_DOWN -ne $PREV_DOWN ]; then
			PREV_DOWN=$JOY_DOWN
			if [ $JOY_DOWN = 0 ]; then
				xdotool keydown $KEY_DOWN
			else
				xdotool keyup $KEY_DOWN
			fi
		fi

		if [ $JOY_LEFT -ne $PREV_LEFT ]; then
			PREV_LEFT=$JOY_LEFT
			if [ $JOY_LEFT = 0 ]; then
				xdotool keydown $KEY_LEFT
			else
				xdotool keyup $KEY_LEFT
			fi
		fi

		if [ $JOY_RIGHT -ne $PREV_RIGHT ]; then
			PREV_RIGHT=$JOY_RIGHT
			if [ $JOY_RIGHT = 0 ]; then
				xdotool keydown $KEY_RIGHT
			else
				xdotool keyup $KEY_RIGHT
			fi
		fi
	fi
done
) < $USB_DEV