#!/bin/bash
# Current weather for xmobar, e.g. "<icon> 7°C": NOAA's decoded METAR (the source of xmobar's Weather plugin)
# Icon from the weather, else the sky conditions; clear/partly/mostly cloudy get moon icons when the sun is down.
# Temperature colors match the plugin's -L 0 -H 30: low up to 0, high above 30.
# With "notify": show the description (e.g. "Light drizzle, mist") and temperature in a notification instead.

STATION=LZIB LAT=48.2 LON=17.2

declare -A ICON=(
    [thermometer]=$'\xef\x8b\x89' [day_sunny]=$'\xee\x8c\x8d' [night_clear]=$'\xee\x8c\xab'
    [day_cloudy]=$'\xee\x8c\x82' [night_partly_cloudy]=$'\xee\x8d\xb9' [day_sunny_overcast]=$'\xee\x8c\x8c'
    [night_cloudy]=$'\xee\x8d\xbe' [cloudy]=$'\xee\x8c\x92' [cloud]=$'\xee\x8c\xbd'
    [thunderstorm]=$'\xee\x8c\x9d' [rain_mix]=$'\xee\x8c\x96' [snow]=$'\xee\x8c\x9a' [showers]=$'\xee\x8c\x99'
    [rain]=$'\xee\x8c\x98' [sprinkle]=$'\xee\x8c\x9b' [fog]=$'\xee\x8c\x93' [smoke]=$'\xee\x8d\x9c'
    [dust]=$'\xee\x8d\x9d'
)

report=$(curl -sf --max-time 20 https://tgftp.nws.noaa.gov/data/observations/metar/decoded/"$STATION".TXT)
temp=$(sed -n 's/^Temperature: .*(\([-0-9.]*\) C).*/\1/p' <<< "$report")
if [[ -z $temp ]]; then
    if [[ $1 == notify ]]; then notify-send "Weather" "No report from $STATION"; else echo "${ICON[thermometer]} N/A"; fi
    exit 0
fi

# Phenomena "in the vicinity" aren't at the station; the rest are e.g. "light drizzle; mist"
wx=$(sed -n 's/^Weather: //p' <<< "$report" | tr ';' '\n' | sed 's/^ *//' | grep -v vicinity)
wx=${wx,,}
sky=$(sed -n 's/^Sky conditions: //p' <<< "$report")
# CAVOK/NSC (no cloud below 5000 ft) have no sky line in the decoded report
[[ -z $sky ]] && grep -qE '^ob: .* (CAVOK|NSC) ' <<< "$report" && sky=clear
sky=${sky,,}

# Sun above the horizon (elevation > -0.833°, as for sunrise/sunset) right now, from the low-precision solar position
sun_up() {
    awk -v t="$(date +%s)" -v lat="$LAT" -v lon="$LON" 'BEGIN {
        r = atan2(0, -1) / 180; d = t / 86400 - 10957.5
        g = (357.529 + 0.98560028 * d) * r
        l = (280.459 + 0.98564736 * d + 1.915 * sin(g) + 0.020 * sin(2 * g)) * r
        e = (23.439 - 0.00000036 * d) * r
        ra = atan2(cos(e) * sin(l), cos(l)); s = sin(e) * sin(l); dec = atan2(s, sqrt(1 - s * s))
        h = (280.46061837 + 360.98564736629 * d + lon) * r - ra
        exit !(sin(lat * r) * sin(dec) + cos(lat * r) * cos(dec) * cos(h) > sin(-0.833 * r))
    }'
}

case $wx in
    *thunder*) icon=thunderstorm ;;
    *freezing*|*sleet*|*ice\ pellets*|*hail*) icon=rain_mix ;;
    *snow*rain*|*rain*snow*|*snow*drizzle*|*drizzle*snow*) icon=rain_mix ;;
    *snow*) icon=snow ;;
    *showers*) icon=showers ;;
    *rain*) icon=rain ;;
    *drizzle*) icon=sprinkle ;;
    *fog*|*mist*) icon=fog ;;
    *haze*|*smoke*) icon=smoke ;;
    *dust*|*sand*) icon=dust ;;
    *)
        case $sky in
            clear*) if sun_up; then icon=day_sunny; else icon=night_clear; fi ;;
            "mostly clear"*|"partly cloudy"*) if sun_up; then icon=day_cloudy; else icon=night_partly_cloudy; fi ;;
            "mostly cloudy"*) if sun_up; then icon=day_sunny_overcast; else icon=night_cloudy; fi ;;
            overcast*|obscured*) icon=cloudy ;;
            *) icon=cloud ;;
        esac
        ;;
esac

if awk -v t="$temp" 'BEGIN { exit !(t > 30) }'; then color="#ffb86c"
elif awk -v t="$temp" 'BEGIN { exit !(t > 0) }'; then color="#50fa7b"
else color="#8be9fd"
fi

if [[ $1 == notify ]]; then
    if [[ -n $wx ]]; then desc=$(paste -sd, <<< "$wx" | sed 's/,/, /g')
    elif [[ $icon == day_sunny ]]; then desc=sunny
    else desc=${sky:-unknown}
    fi
    notify-send "${ICON[$icon]}  Weather" "${desc^}, $temp°C"
    exit 0
fi
echo "${ICON[$icon]} <fc=$color>$temp</fc>°C"