#! /bin/sh

proc_stat_parse() {
    proc_stat="$1"
    n='[0-9]\+'
    echo "$proc_stat" \
    | grep "^cpu$n $n $n $n $n $n $n $n $n $n $n$" \
    | awk '
        {
            cpu  = $1;
            user = $2;
            sys  = $4;
            idle = $5;

            total = user + sys + idle;
            busy  = user + sys;

            if (NR > 1) {printf " "};

            out = sprintf("%s %d %d", cpu, total, busy);
            #print out >> "cpu_usage_debug.txt";
            printf "%s", out;
        }
        END {
            #print "" >> "cpu_usage_debug.txt";
            print "";
        }
        '
}

calc_delta() {
    for proc_stat in "$1" "$2"; do
        proc_stat_parse "$proc_stat"
    done \
    | awk '
        {
            t = NR;
            for (i = 1; i <= (NF - 2); i += 3) {
                cpu_count[t]++;
                cpu_id = $i;  # For occasional debugging
                total  = $(i + 1);
                busy   = $(i + 2);
                cpu[cpu_count[t], "total", t] = total;
                cpu[cpu_count[t], "busy" , t] = busy;
            }
        }

        END {
            for (c=1; c<=cpu_count[2]; c++) {
                total_1 = cpu[c, "total", 1];
                total_2 = cpu[c, "total", 2];
                busy_1  = cpu[c, "busy" , 1];
                busy_2  = cpu[c, "busy" , 2];
                total_d = total_2 - total_1;
                busy_d  = busy_2  - busy_1;
                percent_busy = (busy_d / total_d) * 100;

                #printf(\
                #    "c: %d, total_1: %f total_2: %f, total_d: %f\n",
                #     c,     total_1,    total_2,     total_d \
                #) >> "cpu_usage_debug.txt";
                #printf(\
                #    "c: %d, busy_1: %f busy_2: %f, busy_d: %f\n",
                #     c,     busy_1,    busy_2,     busy_d \
                #) >> "cpu_usage_debug.txt";
                #printf(\
                #    "c: %d, percent_busy: %f\n",
                #     c, percent_busy \
                #) >> "cpu_usage_debug.txt";

                if (c > 1) {printf " "};
                out = sprintf("%3.0f%%", percent_busy)
                #printf "c: %d, out: %s\n", c, out >> "cpu_usage_debug.txt";
                printf "%s", out;
            }
            #print "" >> "cpu_usage_debug.txt";
            print "";
        }
        '
}

main() {
    last_proc_stat="$HOME/var/run/cpu_usage_from_proc_since_last_check/last_proc_stat"

    if [ ! -f "$last_proc_stat" ]
    then
        mkdir -p `dirname "$last_proc_stat"`
        cat /proc/stat > "$last_proc_stat"
        sleep 0.1
    fi

    previous=`cat $last_proc_stat`;
    cat /proc/stat > "$last_proc_stat"
    current=`cat $last_proc_stat`;

    calc_delta "$previous" "$current"
}

main $@