#!/bin/bash

declare -A graph_chars_up='(
	[0_0]=⠀ [0_1]=⢀ [0_2]=⢠ [0_3]=⢰ [0_4]=⢸ 
	[1_0]=⡀ [1_1]=⣀ [1_2]=⣠ [1_3]=⣰ [1_4]=⣸ 
	[2_0]=⡄ [2_1]=⣄ [2_2]=⣤ [2_3]=⣴ [2_4]=⣼ 
	[3_0]=⡆ [3_1]=⣆ [3_2]=⣦ [3_3]=⣶ [3_4]=⣾ 
	[4_0]=⡇ [4_1]=⣇ [4_2]=⣧ [4_3]=⣷ [4_4]=⣿ 
)'
# declare -A graph_chars_down='(
# 	[0_0]=⠀ [0_1]=⠈ [0_2]=⠘ [0_3]=⠸ [0_4]=⢸ 
# 	[1_0]=⠁ [1_1]=⠉ [1_2]=⠙ [1_3]=⠹ [1_4]=⢹ 
# 	[2_0]=⠃ [2_1]=⠋ [2_2]=⠛ [2_3]=⠻ [2_4]=⢻ 
# 	[3_0]=⠇ [3_1]=⠏ [3_2]=⠟ [3_3]=⠿ [3_4]=⢿ 
# 	[4_0]=⡇ [4_1]=⡏ [4_2]=⡟ [4_3]=⡿ [4_4]=⣿ 
# )'

# cntcpu=0
# CountCPU() {
#     local fld foo
#     while read fld foo;do
# 	[ "$fld" = "processor" ] && ((cntcpu++))
#     done </proc/cpuinfo
# }
# CountCPU

percent() {
    local _percent_p=000$((${1}00000/$2))
    printf ${3+-v} $3 "%.2f%%" \
        ${_percent_p:0:${#_percent_p}-3}.${_percent_p:${#_percent_p}-3}
}

crtstat() {
    local -a pstat
    read -a pstat < /proc/stat
    utcpu="${pstat[*]:1}"
    utcpu=$[${utcpu// /+}]
    idlcpu=${pstat[4]}
}

readGrSizes() {
    { read height
      read width
    } < <(
	tput -S - <<<$'lines\ncols'
    )
    pixels=$[(height-1)*4]
    graphline_even=() graphline_odd=()
    evenodd=0
    printf "\e[H\e[2J"
}

mainloop() {
    while IFS=. read sec micro <<<$EPOCHREALTIME
	  tosleep=$[2000000-10#$micro]
	  ! read -st .${tosleep:1} -n 1 key_pressed;do
	lastut=$utcpu lastidl=$idlcpu
	crtstat
	crtpix=$[pixels-(idlcpu-lastidl)*pixels/(utcpu-lastut)]
	declare -n crtline=graphline_${lnnames[evenodd]}
	for ((i=1;i<height;i++));do
	    lval[i]=${val[i]:-0}
	    if ((crtpix>=i*4)) ;then
		val[i]=4
	    elif ((crtpix<=(i*4-4))) ;then
		val[i]=0
	    else
		val[i]=$[crtpix%4]
	    fi
	    crtline[i]+=${graph_chars_up[${lval[i]}_${val[i]}]}
	    ((${#crtline[i]}>width))&&crtline[i]=${crtline[i]:1}
	    printf "\e[%d;%dH\e[K%s" \
		   $((height-i)) $((width+1-${#crtline[i]})) "${crtline[i]}"
	done
	((evenodd=1-evenodd))
	IFS=. read sec micro <<<$EPOCHREALTIME
	percent $[utcpu+lastidl-idlcpu-lastut] $[utcpu-lastut] prct
	printf "\e[%d;1H%(%T)T.%s %9s  (last sleep: 0.%s sec)\e[K" \
		$height $sec $micro $prct ${tosleep:1}
    done
}

trap readGrSizes WINCH

crtstat
height=24
width=80
lnnames=(even odd)
declare -a graphline_even graphline_odd
readGrSizes
tput civis
mainloop
tput cnorm