#!/bin/sh

declare -i f=75 s=13 r=2000 t=0 c=1 n=0 l=0
declare -ir w=$(tput cols) h=$(tput lines)
declare -i x=$((w/2)) y=$((h/2))
declare -ar v=( [00]="\x83" [01]="\x8f" [03]="\x93"
        [10]="\x9b" [11]="\x81" [12]="\x93"
        [21]="\x97" [22]="\x83" [23]="\x9b"
        [30]="\x97" [32]="\x8f" [33]="\x81" )

OPTIND=1
while getopts "f:s:r:h" arg; do
case $arg in
    f) ((f=($OPTARG>19 && $OPTARG<101)?$OPTARG:$f));;
    s) ((s=($OPTARG>4 && $OPTARG<16 )?$OPTARG:$s));;
    r) ((r=($OPTARG>0)?$OPTARG:$r));;
    h) echo -e "Usage: pipes [OPTION]..."
        echo -e "Animated pipes terminal screensaver.\n"
        echo -e " -f [20-100]\tframerate (D=75)."
        echo -e " -s [5-15]\tprobability of a straight fitting (D=13)."
        echo -e " -r LIMIT\treset after x characters (D=2000)."
        echo -e " -h\t\thelp (this screen).\n"
        exit 0;;
    esac
done

tput smcup
tput reset
tput civis
while ! read -t0.0$((1000/$f)) -n1; do
    # New position:
    (($l%2)) && ((x+=($l==1)?1:-1))
    ((!($l%2))) && ((y+=($l==2)?1:-1))

    # Loop on edges (change color on loop):
    ((c=($x>$w || $x<0 || $y>$h || $y<0)?($RANDOM%7-1):$c))
    ((x=($x>$w)?0:(($x<0)?$w:$x)))
    ((y=($y>$h)?0:(($y<0)?$h:$y)))

    # New random direction:
    ((n=$RANDOM%$s-1))
    ((n=($n>1||$n==0)?$l:$l+$n))
    ((n=($n<0)?3:$n%4))

    # Print:
    tput cup $y $x
    echo -ne "\033[1;3${c}m\xe2\x94${v[$l$n]}"
    (($t>$r)) && tput reset && tput civis && t=0 || ((t++))
    l=$n
done
tput rmcup