#!/bin/bash
# colorPing.sh - run ping, then dynamically change background's terminal color
# (C) 2025 Felix Hauri - felix@f-hauri.ch
# Accept ping's arguments like: [-i delay] [-I iface] [-a] [...] <host|address>
#        ( Note: script use `-O` in code. )
# User interaction:
# Once run, you could
#  - ask for current statistics by hitting any of
# 		`S`, `question mark`, `space` or `enter` key.
#  - end ping and quit programm by hitting one of
# 		`Q` or `escape` key.

# This use XTerm CtlSeqs "Change VT100 text background color": 'OSC Ps ; Pt ST',
# zcat /usr/share/doc/xterm/ctlseqs.ms.gz|soelim|eqn|tbl|pic|groff -ms -T utf8
# shellcheck disable=SC2059 disable=SC1003 ##	where Ps=11: 
getSetVT100Bg='\e]11;%s\e\\'

initGetBgSetTheme() {
    local colorVals bgColArray
    exec {TERM}>&1
    # Get current terminal background color
    printf -v initialBgColor "$getSetVT100Bg" '?' >&$TERM
    IFS= read -d \\ -srp "$initialBgColor" initialBgColor

    # Find highest color value 
    IFS='/' read -ra colorVals <<< "${initialBgColor#*:}"	# split values
    printf -v bgColArray '[16#%s]= ' "${colorVals[@]%??}"	# create indexes
    local -a "colorVals=($bgColArray)"
    colorVals=("${!colorVals[@]}")		# create array from indexes
    # Define ok/bad  colors regarding current theme (dark or light) used 
    if (( colorVals[-1] < 128 )); then
	bgOk=DarkGreen bgBad=DarkRed
    else
	bgOk=PaleGreen bgBad=LightPink
    fi
}
runBgPing() {
    exec {pingFD}< <(LANG=C exec ping -O "${@:-8.8.8.8}")
    pingPid=$!
}
leave() {
    printf "%s\\" "$initialBgColor" >&$TERM
    [[ -d /proc/$pingPid ]] && kill $pingPid
    exit
}
getUserKey() {
    local char IFS=
    if read -d '' -rsn 1 -t .03 char; then
	case ${char,} in
	    s|$'\n'|\ |\? )	kill -QUIT $pingPid ;;
	    q|$'\e' )		kill -INT $pingPid ;;
	esac
    fi
}
getPingOut() {
    local line
    if read -ru $pingFD -t 0 _; then
	read -ru $pingFD line || [[ -d /proc/$pingPid ]] || return 1
	case $line in		# Set terminal background color
	    *[0-9]\ bytes\ from*)	printf "$getSetVT100Bg" "$bgOk" ;;
	    no\ answer*)		printf "$getSetVT100Bg" "$bgBad" ;;
	esac  >&$TERM
	echo "$line"
    fi
    return 0
}

initGetBgSetTheme
runBgPing "$@"
trap 'kill -INT $pingPid' 2
trap 'leave' 0 1 3 6 15
while :; do
    getUserKey
    getPingOut || break
done