#! /usr/bin/awk -f

BEGIN {
     FS = msg_fs ? msg_fs : "|"
    OFS = msg_fs ? msg_fs : "|"
    Kfs = key_fs ? key_fs : ":"

    # TODO: Read spec from a file
    bat_alert_spec[100] = "low|Energy_Bellow_Full|Must have perfection!"
    bat_alert_spec[50] = "low|Energy_Bellow_Half|Where is the charger?"
    bat_alert_spec[20] = "med|Energy_Low|Get the charger."
    bat_alert_spec[15] = "med|Energy_Low|Get the charger!"
    bat_alert_spec[10] = "hi|Energy_Low|Plug it in, ASAP!"
    bat_alert_spec[5]  = "hi|Energy_CRITICALLY_Low|CHARGE NOW!!! GO GO GO!!!"
}

$1 == "OK" && \
$2 == "khatus_sensor_energy" && \
$3 == "line_power" {
    line_power_prev = line_power_curr
    line_power_curr = $4
    if (line_power_curr == "no" && line_power_prev != "no") {
        alert("low", "PowerUnplugged", "")
    }
}

$1 == "OK" && \
$2 == "khatus_sensor_energy" && \
$3 == "battery_state" {
    battery_state_prev = battery_state_curr
    battery_state_curr = $4
}

$1 == "OK" && \
$2 == "khatus_sensor_energy" && \
$3 == "battery_percentage" {
    # TODO: Re-think the spec - can't rely on order of keys
    battery_percentage = ensure_numeric($4)
    if (battery_state_curr == "discharging") {
        for (threshold in bat_alert_spec) {
            threshold = ensure_numeric(threshold)
            if (battery_percentage <= threshold && !alerted[threshold]) {
                split(bat_alert_spec[threshold], msg, "|")
                priority = msg[1]
                subject = msg[2]
                body = sprintf("%d%% %s", battery_percentage, msg[3])
                alert(priority, subject, body)
                alerted[threshold]++
            }
        }
    } else {
        delete alerted
    }
}

function alert(priority, subject, body) {
    # priority : "low" | "med" | "hi"
    # subject  : no spaces
    # body     : anything
    print("OK", "khatus_monitor_energy", "alert", priority, subject, body)
}

function ensure_numeric(n) {
    return n + 0
}

#-------------------------------
# Why do we need ensure_numeric?
#-------------------------------
# awk appears to be guessing the type of an inputted scalar based on usage, so
# if we read-in a number, but did not use it in any numeric operations, but did
# use as a string (even in just a format string!) - it will be treated as a
# string and can lead to REALLY SURPRISING behavior in conditional statements,
# where smaller number may compare as greater than the bigger ones, such as.
#
# Demo:
#
# $ awk 'BEGIN {x = "75"; y = "100"; sprintf("x: %d, y: %d\n", x, y); if (x > y) {print "75 > 100"} else if (x < y) {print "75 < 100"}}'
# 75 < 100
# $ awk 'BEGIN {x = "75"; y = "100"; sprintf("x: %s, y: %d\n", x, y); if (x > y) {print "75 > 100"} else if (x < y) {print "75 < 100"}}'
# 75 > 100

# However, once used as a number, seems to stay that way even after being
# used as string:
#
# $ awk 'BEGIN {x = "75"; y = "100"; x + y; sprintf("x: %s, y: %d\n", x, y); if (x > y) {print "75 > 100"} else if (x < y) {print "75 < 100"}}'
# 75 < 100
# 
# $ awk 'BEGIN {x = "75"; y = "100"; x + y; sprintf("x: %s, y: %d\n", x, y); z = x y; if (x > y) {print "75 > 100"} else if (x < y) {print "75 < 100"}}'
# 75 < 100
# 
# $ awk 'BEGIN {x = "75"; y = "100"; x + y; z = x y; if (x > y) {print "75 > 100"} else if (x < y) {print "75 < 100"}}'
# 75 < 100
# $ awk 'BEGIN {x = "75"; y = "100"; z = x y; if (x > y) {print "75 > 100"} else if (x < y) {print "75 < 100"}}'
# 75 > 100