#!/usr/bin/env awk -f


function log10(n) {
    return log(n)/log(10.0)
}


function merge_meas(est_val, est_unc, meas_val, meas_unc) {

    # Kalman filtering compares variances,
    # convert uncertainties to square units
    est_unc = (0.5*est_unc)^2.0
    meas_unc = (0.5*meas_unc)^2.0

    K = (est_unc)/((est_unc) + (meas_unc))
    est_val = est_val + K*(meas_val - est_val)
    est_unc = (est_unc*meas_unc)/(est_unc + meas_unc)

    # convert est_unc back to original units
    est_unc = 2.0*sqrt(est_unc)

    return sprintf(OFMT OFS OFMT ORS, est_val, est_unc)

}


function sigfig(val, unc) {

    ordmag_val = log10(val)
    ordmag_unc = log10(unc)

    ordmag_high = sqrt((ordmag_val)^2.0 + (ordmag_unc)^2.0)
    ordmag_low = ((ordmag_val)^-1.0 + (ordmag_unc)^-1.0)^-1.0
    ordmag_range = ordmag_high - ordmag_low

    sigfig_unc = sprintf("%.f", sqrt((ordmag_range)^2.0 + 3.0^2.0))
    sigfig_val = sprintf("%.f", sqrt((ordmag_range)^2.0 + (sigfig_unc)^2.0 + 3.0^2.0))

    ofmt_val = "%." sigfig_val "g"
    ofmt_unc = "%." sigfig_unc "g"

    return sprintf(ofmt_val OFS ofmt_unc, val, unc)

}


function ck_cptime() {

    t_sys_meas[1] = systime()
    t_sys_meas[2] = 1.0

    "sysctl kern.cp_time" | getline cptime_cmd
    close("sysctl kern.cp_time")

    split(merge_meas(t_sys_meas[1], t_sys_meas[2], systime(), 1.0), t_sys_meas)

    sub("^.*=", "", cptime_cmd)
    gsub(",", OFS, cptime_cmd)
    #split(cptime_cmd, cptime_arr, ",")

    return sprintf(OFMT OFS "%s", t_sys_meas[1], cptime_cmd)

}


function ck_uptime() {

    # check uptime cmd
    "uptime" | getline t_up_cmd
    close("uptime")

    # evaluate measured uptime
    t_up_meas[1] = 0.0
    t_up_meas[2] = systime()

    sub("^.*up ", "", t_up_cmd)
    sub(", load.*$", "", t_up_cmd)
    split(t_up_cmd, t_up_cmd_arr, ",")

    for (i in t_up_cmd_arr) {

        # TODO: add cases for days, months, years, etc.
        if (t_up_cmd_arr[i] ~ /day/) {
            split(t_up_cmd_arr[i], days)
            t_up_meas[1] += 86400.0*(days[1] + 0.0)
            (t_up_meas[2] > 86400.0) ? t_up_meas[2] = 86400.0 : t_up_meas[2] += 0.0
        }

        if (t_up_cmd_arr[i] ~ /hr/) {
            split(t_up_cmd_arr[i], hrs)
            t_up_meas[1] += 3600.0*(hrs[1] + 0.0)
            (t_up_meas[2] > 3600.0) ? t_up_meas[2] = 3600.0 : t_up_meas[2] += 0.0
        }

        if (t_up_cmd_arr[i] ~ /min/) {
            split(t_up_cmd_arr[i], mins)
            t_up_meas[1] += (60.0*(mins[1] + 0.0))
            (t_up_meas[2] > 60.0) ? t_up_meas[2] = 60.0 : t_up_meas[2] += 0.0
        }

        if (t_up_cmd_arr[i] ~ /:/) {
            split(t_up_cmd_arr[i], hrs_min, ":")
            t_up_meas[1] += 3600.0*(hrs_min[1] + 0.0)
            (t_up_meas[2] > 3600.0) ? t_up_meas[2] = 3600.0 : t_up_meas[2] += 0.0
            t_up_meas[1] += 60.0*(hrs_min[2] + 0.0)
            (t_up_meas[2] > 60.0) ? t_up_meas[2] = 60.0 : t_up_meas[2] += 0.0
        }

    }

    return sigfig(t_up_meas[1], t_up_meas[2])

}


BEGIN {

    OFMT="%f"
    pi = 4.0*atan2(1.0, 1.0)
    c0 = 299792458  # m/sec

    #print("_systime_", systime())
    #print("_boottime_", ck_boottime())
    print( ck_cptime() )

}