#!/bin/bash -u
#   $0 [ type [ word [ time ] ] ]
# type is 'solid' or 'clearing'
# Draw a circle on the terminal screen using cursor control.
# Put out the word or a "*" if no word.
# time is time allowed to draw one complete sine
# (we draw one forward and then one backward)
# -Ian! D. Allen - idallen@idallen.ca - www.idallen.com

PATH=/bin:/usr/bin ; export PATH
LC_ALL=C ; export LC_ALL   # no internationalization in this script
LANG=C ; export LANG
umask 022

type=${1-'clearing'}
word=${2-'*'}
time=${3-'2'}

ColourSwitch () {
    # this fails if terminal doesn't do colours; let it pass
    tput setaf ${colours[$colour]} # || exit $?
    colour=$(( ( colour + 1 ) % ${#colours[*]} ))
}

case "$type" in
clearing )
    el=$( tput el ) || exit $?
    el1=$( tput el1 ) || exit $?
    ;;
solid )
    el=
    el1=
    ;;
* ) echo 1>&2 "$0: unknown type '$type' must be solid or clearing"
    exit 1
    ;;
esac

ss=( $(stty size) ) || exit $?
rows=${ss[0]}
cols=${ss[1]}
# divide the time by the number of columns to find colsleep
colsleep=$( dc -e "2 k $time $cols / p" )
width=$cols
margin=$(( width - ${#word} ))
or=$(( rows / 2 ))
oc=$(( cols / 2 ))
colours=( $( seq 1 6 | sort -R ) )
colour=0
r=$rows
# echo "colours ${colours[*]}"
piby4=$( echo 'scale=10 ; a(1)' | bc -l )
shrink=0.945
for (( i=0; i <= cols; i++ )) ; do
    y=$( echo "scale=10; x = $or + $shrink * $or * s(8*$i/$cols*$piby4); scale=0; x / 1" | bc -l )
    tput cup $y $i  || exit $?
    if [ $i -ge $margin ] ; then
	echo -n "$el*"
    else
	echo -n "$el$word"
    fi
    ColourSwitch
    sleep $colsleep
done
for (( i=cols; i >= 0; i-- )) ; do
    y=$( echo "scale=10; x = $or - $shrink * $or * s(8*$i/$cols*$piby4); scale=0; x / 1" | bc -l )
    tput cup $y $i || exit $?
    if [ $i -ge $margin ] ; then
	echo -n "*"
    else
	echo -n "$word"
    fi
    ColourSwitch
    sleep $colsleep
done
tput sgr0 || exit $?
tput cup 0 0 || exit $?