#!/bin/zsh


_STTY=$(stty -g)    # Save current terminal setup
printf   "\e[2J"    # clear screen, set cursos at beginning
stty -echo -icanon  # Turn off line buffering
printf '\e[?25h'		# Turn on the cursor 

# VARIABLES
typeset -A IMAGE
X=0 
Y=24
height=0
width=0
snake='═'

vertical=false
forward=true
upward=true
pen_down=true

function get_size() {
    # Get terminal size ('stty' is POSIX and always available).
    read -r LINES COLUMNS < <(stty size)
		height=$((LINES-1))
		width=$((COLUMNS-1))
}

function start_the_snake() {
	rm thesnake
	for i in {0..$height}
	do
		for j in {0..$width}
		do
			IMAGE["${i};${j}"]=' ' ; printf ${IMAGE["${i};${j}"]}
		done
	done
	printf '\e[2J\e[H' ; printf '\e[0;24H'
}

function save_the_snake() {
	for i in {0..$height}
	do
		for j in {0..$width}
		do
			printf ${IMAGE["${i};${j}"]}
		done
	done >> thesnake
	#sed -e "s/.\{$((width-1))\}/&\n/g" < thesnake > snake80
}

function show_the_snake() {
	printf '\e[2J\e[H'
	for i in {0..$height}
	do
		for j in {0..$width}
		do
			printf ${IMAGE["${i};${j}"]}
		done
	done
	printf '\e[%s;%sH' "$((Y+1))" "$((X+1))"
}
function at_exit() {
	printf "\e[?9l"          # Turn off mouse reading
	printf "\e[?12l\e[?25h"  # Turn on cursor
	stty "$_STTY"            # reinitialize terminal settings
	clear
	exit
}

#═ ║╒ ╓ ╔ ╕ ╖ ╗ ╘ ╙ ╚ ╛ ╜ ╝ ╞ ╟  
#╠ ╡ ╢ ╣ ╤ ╥ ╦ ╧ ╨ ╩ ╪ ╫ ╬ 

function move_snake_up() {
	if [ "$vertical" = false ] ; then
		if [ "$forward" = true ] ; then
			snake='╝'
		else
			snake='╚'
		fi
	else
		snake='║'
	fi
	#draw nothing it the pen is not down
	if [ "$pen_down" = false ] ; then
		snake=' '
	fi
	IMAGE["${Y};${X}"]=$snake ; Y=$((Y-1)) ; vertical=true ; upward=true
}

function move_snake_down() {
	if [ "$vertical" = false ] ; then
		if [ "$forward" = true ] ; then
			snake='╗'
		else
			snake='╔'
		fi
	else
		snake='║'
	fi
	#draw nothing it the pen is not down
	if [ "$pen_down" = false ] ; then
		snake=' '
	fi
	IMAGE["${Y};${X}"]=$snake ; Y=$((Y+1)) ; vertical=true ; upward=false
}

function move_snake_forward() {
	if [ "$vertical" = true ] ; then
		if [ "$upward" = true ] ; then
			snake='╔'
		else
			snake='╚'
		fi
	else
		snake='═'
	fi
	#draw nothing it the pen is not down
	if [ "$pen_down" = false ] ; then
		snake=' '
	fi
	IMAGE["${Y};${X}"]=$snake ; X=$((X+1)) ; vertical=false ; forward=true
}

function move_snake_backward() {
	if [ "$vertical" = true ] ; then
		if [ "$upward" = true ] ; then
			snake='╗'
		else
			snake='╝'
		fi
	else
		snake='═'
	fi
	#draw nothing it the pen is not down
	if [ "$pen_down" = false ] ; then
		snake=' '
	fi
	IMAGE["${Y};${X}"]=$snake ; X=$((X-1)) ; vertical=false ; forward=false
}

# Main #
get_size
start_the_snake
echo 
while read -s -k 1 cr;
do
	case "$cr" in
		w)	move_snake_up ; show_the_snake ;;
		s)	move_snake_down ; show_the_snake ;;
		a)	move_snake_backward ; show_the_snake ;;
		d)	move_snake_forward ; show_the_snake ;;
		t)  pen_down=true ;;
		y)  pen_down=false ;;
		q)	save_the_snake && at_exit ;;
	esac
done