monitorbackend

#!/bin/bash
#https://pasteboard.co/IdOsZrs.png
inside(){
	grep -q $2 <<<"${!1}" && return 0 || return 1
}
jsonify_rows(){
	echo -ne "["
	cat - | sed 's/\"/\\"/g' |  sed "s/'/\\'/g" | sed "s/^/\"/;s/$/\"/" | tr "\n" ","
	echo -ne "]"
}

j_dictkey(){
	echo -ne "\"${1}\":"
	cat -
	echo -ne ","
}
j_sep(){
	cat -
	echo -ne ','
}

j_dict(){
	{
		echo -ne "{"
		cat - 
		echo -ne "}"
	} | sed "s/,]/]/g;s/,}/}/g"
}

j_list(){
	{
		echo -ne "["
		cat - 
		echo -ne "]"
	} | sed "s/,]/]/g;s/,}/}/g"
}

j_dict_namerows(){
	local rmnames=(${*})
	local i=0
	local m="[^0-9]"
	while read line; do
		((i=0))
		for x in ${line} ; do
			[[ $x  =~ $m ]] && x="\"${x}\"" 
			echo -ne "${x}" | j_dictkey ${rmnames[${i}]}
			((i++))
		done | j_dict | j_sep
	done | j_list
}

function clean {
	rm $PIPE $CPUUS
	kill $CPUWATCHPID
}

trap clean EXIT

cpuload(){
	while read cpu usage ; do
		echo $usage | j_dictkey $cpu
	done <$CPUUS | j_dict
}


rsp(){
	local len=$(wc -c <<<${!1})
	local headers=(
		"Access-Control-Allow-Origin: *"
		"Content-Encoding: identity"
		"Connection: keep-alive"
		"Content-type: ${2}; charset=utf-8"
		"Content-Length: ${len}"
	)

	echo -en "HTTP/1.1 200 OK\r\n"
	printf '%s\n' "${headers[@]}"
	echo -en "\n"
	cat <<<"${!1}"
}

PIPE=$(mktemp -u)
CPUUS=$(mktemp)
mkfifo ${PIPE}


while true ; do
	CPUSTATB=(${CPUSTAT[@]})
	CPUSTAT=($(
		grep cpu < /proc/stat | while read cpu user nice system idle iowait irq softirq steal guest ; do 
			cpu_active=$((user+system+nice+softirq+steal))
			cpu_total=$((cpu_active+idle+iowait))
			echo "${cpu}|${cpu_active}|${cpu_total}"
		done 
	))
	l=${#CPUSTAT[@]}
	for (( i=0; i < l ; i++ )) do
		IFS="|" read cpuN activeN totalN <<<"${CPUSTAT[${i}]}"
		IFS="|" read cpuB activeB totalB <<<"${CPUSTATB[${i}]}"
		[[ $((totalN - totalB)) == 0 ]] ||
			echo $cpuN $(( 100 * (activeN-activeB)/(totalN - totalB) ))
	done > $CPUUS
	
	sleep 1

done & CPUWATCHPID=$!


while nc -l 8080 <$PIPE | {
	header=$( head -n 1 | awk "{print \$2}" | tr "/" "\n" )
	echo $header >&2
	if [ -z "$header" ] ; then
		read -r -d '' indexhtml <./index.html
		rsp indexhtml text/html
	else
		RSP=$({
			inside header ps && {
				psb=$(ps -eo pid,pcpu,pmem,cmd) 
				sed "1d;s/[ \t]\+/ /g;s/^ //" <<<"${psb}" | jsonify_rows | j_dictkey ps;
			}

			inside header stat &&
				cat /proc/stat | jsonify_rows | j_dictkey stat;

			inside header mem &&
				free -m | sed "1d;s/[ \t]\+/ /g;s/^ //;s/.*://" | \
					j_dict_namerows all used free shared cache avaiable | j_dictkey mem;

			inside header cpuload &&
				cpuload | j_dictkey cpuload

			inside header fs && 
					df -m | grep "^/dev" | j_dict_namerows fs 1mbl used ava usedpr mp | j_dictkey fs
		} | j_dict)
		[ -z "${RSP}" ] && RSP="Invalid header"
		rsp RSP application/json
	fi
} > $PIPE || true; do
  echo "================================================"
done