#!/bin/bash
# Animated pipes.sh terminal screensaver at an angle.
# Copyright (C) 2013 by Yu-Jie Lin
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
# Blog: http://blog.yjl.im/2013/07/pipesxsh-animated-pipessh-terminal.html
# Gist: https://gist.github.com/livibetter/5974905
# Screenshot: https://lh3.googleusercontent.com/-UaCta_DtgrQ/Ud6dqIgcfmI/AAAAAAAAE_8/VXPac0OpULU/s800/pipesX.sh.gif
# Screenshot: https://lh6.googleusercontent.com/-yBety-A8J_c/Ud6dk10sjBI/AAAAAAAAE_0/S98aRRV8t0s/s800/pipesX.sh%25202013-07-11--19%253A51%253A05.png
# Screencast: http://youtu.be/dITTlFPYVPA
 
W=$(tput cols) H=$(tput lines)
# maximal random value + 1
M=32768
 
SETS=('╱╲' '/\' '⎰⎱' '∕∖' 'ᓱᓴ' '⋰⋱')
COLORS=(31 32 33 34 35 36 37)
 
# default values
N=1
T=0
I=0.05
P=25
R=$((W * H / 4))
 
HELP="Usage: $(basename $0) [OPTIONS]
Animated pipes.sh terminal screensaver at an angle.
 
Options:
 
-n [1-] number of pipes. (Default: $N)
-t [0-$((${#SETS[@]} - 1))] type of pipes. (Default: $T)
-i [float] piping interval or maze generation interval. (Default: $I)
-P [0-100] probability of a turning pipe or of \\ in maze generation. (Default: $P)
-r [LIMIT] reset after x characters, 0 if no limit. (Default: $R)
-R random starting point.
-C no color.
-X maze generation.
-h this help message.
"
 
while getopts "n:t:i:P:r:RCXh" arg; do
	case $arg in
		n)
			((N = OPTARG > 0 ? OPTARG : N))
			;;
		t)
			((T = (OPTARG >= 0 && OPTARG < ${#SETS[@]}) ? OPTARG : T))
			;;
		i)
			I=$OPTARG
			;;
		P)
			((P = (OPTARG >= 0 && OPTARG <= 100) ? OPTARG : P))
			;;
		r)
			((R = OPTARG >= 0 ? OPTARG : R))
			;;
		R)
			RNDSTART=1
			;;
		C)
			NOCOLOR=1
			;;
		X)
			MAZE=1
			;;
		h)
			echo -e "$HELP"
			exit 0
			;;
	esac
done
 
do_exit() {
	# Show cursor and echo stdin
	echo -ne "\e[?25h"
	stty echo
	clear
	exit 0
}
trap do_exit INT TERM
 
# No echo stdin and hide the cursor
stty -echo
echo -ne "\e[?25l"
 
# maze geneartion
while [[ $MAZE ]] && clear; do
	[[ $NOCOLOR ]] || echo -ne "\e[1;${COLORS[${#COLORS[@]} * RANDOM / M]}m"
	for ((i = 0; i < W * H; i++ )); do
		echo -ne ${SETS[T]:100 * RANDOM / M < P:1}
	done
	read -t $I -n 1 && [[ $REPLY =~ q|Q ]] && do_exit
done
 
# initialze values
for ((n = 0; n < N; n++)); do
	((X[n] = RNDSTART ? (W + 2) * RANDOM / M : W / 2))
	((Y[n] = RNDSTART ? (H + 2) * RANDOM / M : H / 2))
	D[n]=$((4 * RANDOM / M))
	C[n]=${COLORS[${#COLORS[@]} * RANDOM / M]}
done
 
clear
while :; do
	for ((n = 0; n < N; n++, CC = 0)); do
		x=${X[n]} y=${Y[n]}
		d=${D[n]} c=${C[n]}
		 
		# calculate new direction `d`
		# 1 0
		# \/ 4 directions 0 to 3
		# /\
			# 2 3
		# valid directions: d: dd', d' is the new direction
		# d
		# 0: / 00 \ 01 03
		# / / /\
			# 1: / 10 \ 11 12
		# \ \ /\
			# 2: \/ 21 / 22 / 23
		# / \
			# 3: \/ 30 \ 32 \ 33
		# / \
			((d = (100 * RANDOM / M) < P ? ((d + 1) + 2 * (RANDOM % 2)) % 4 : d))
		((e = (d + 1) % 4))
		 
		# calculate new position
		# d' x' y'
		# 0: x+1 y-1
		# 1: x-1 y-1
		# 2: x-1 y+1
		# 3: x+1 y+1
		((xn = e < 2 ? x + 1 : x - 1))
		((yn = d < 2 ? y - 1 : y + 1))
		# adjust position and change color?
		((d < 2 && y == 0)) && ((yn--, CC=1))
		((e > 1 && x == 0)) && ((xn--, CC=1))
		((d > 1 && y == H)) && ((yn++, CC=1))
		((e < 2 && x == W)) && ((xn++, CC=1))
		((CC)) && c=${COLORS[${#COLORS[@]} * RANDOM / M]}
		 
		# warp pipe
		((xn = (xn + W + 1) % (W + 1)))
		((yn = (yn + H + 1) % (H + 1)))
		 
		# calculate position in terminal
		# d' xt yt
		# 0: x' y'+1
		# 1: x'+1 y'+1
		# 2: x'+1 y'
		# 3: x' y'
		((xt = e < 2 ? xn : xn + 1))
		((yt = d < 2 ? yn + 1 : yn))
		 
		echo -ne "\e[${yt};${xt}H"
		[[ $NOCOLOR ]] || echo -ne "\e[1;${c}m"
		echo -n "${SETS[T]:d%2:1}"
		 
		X[n]=$xn Y[n]=$yn
		D[n]=$d C[n]=$c
	done
	read -t $I -n 1 && [[ $REPLY =~ q|Q ]] && do_exit
	((R)) && ((r += N, r >= R)) && r=0 && clear
done
 
do_exit