#!/bin/sh
# -*- sh -*-

: << =cut

=head1 NAME

wunderground - Plugin to monitor weather stations through Weather Underground

The precipitation rate is recalculated from the daily cumulative sum
precipTotal, as a DERIVE value, rather than using the immediate precipRate as a
GAUGE. This allows to have more correct aggregates for the
weekly/monstly/yearly graphs, particularly in case of missing values.

However, to work around the limitation that DERIVE only supports integers, the
decimal point is also shifted two places right (*100) from the reported value,
so even small values can be represented. The value is then rescaled to cancel
this shift (/100), and expressed per hour rather than second (*3600), as it is
the usual unit for precipitation.

=head1 CONFIGURATION

	[wunderground]
	env.api_key e1f10a1e78da46f5b10a1e78da96f525 # this is the default; it seems to be what the website uses
	env.station_id KCASANFR1708
	env.units metric		# optional, this is the default
	env.base_url			# optional, default to https://api.weather.com/v2/pws/observations/current
	env.connect_timeout 1		# optional, amount to wait for requests, in seconds
	env.alerts yes			# optional, controls whether to report alerts, enabled by default

Alternatively, the station_id can be encoded in the name of the symlink as
wunderground_STATIONID (e.g., wundergound_KCASANFR1708). This allows to monitor
multiple stations at once. The configuration can then omit the station_id (it
will be ignored if present), and only one section can be used for all instances
of the plugin.

	[wunderground_*]
	env.api_key e1f10a1e78da46f5b10a1e78da96f525 # this is the default; it seems to be what the website uses
	env.units metric		# optional, this is the default
	env.base_url			# optional, default to https://api.weather.com/v2/pws/observations/current
	env.connect_timeout 1		# optional, amount to wait for requests, in seconds

=head1 AUTHOR

Olivier Mehani

Copyright (C) 2020--2021 Olivier Mehani <shtrom+munin@ssji.net>

=head1 LICENSE

SPDX-License-Identifier: GPL-3.0-or-later

=head1 MAGIC MARKERS

 #%# family=manual

=cut

# Example output
#
# curl 'https://api.weather.com/v2/pws/observations/current?apiKey=e1f10a1e78da46f5b10a1e78da96f525&stationId=KCASANFR1708&numericPrecision=decimal&format=json&units=m'
#{"observations":[{"stationID":"KCASANFR1708","obsTimeUtc":"2020-06-15T06:30:54Z","obsTimeLocal":"2020-06-14 23:30:54","neighborhood":"Van Ness - Civic Center","softwareType":"Weather logger V3.0.8","country":"US","solarRadiation":null,"lon":-122.423,"realtimeFrequency":null,"epoch":1592202654,"lat":37.788,"uv":null,"winddir":null,"humidity":90.0,"qcStatus":1,"imperial":{"temp":58.6,"heatIndex":58.6,"dewpt":55.8,"windChill":null,"windSpeed":null,"windGust":null,"pressure":29.85,"precipRate":null,"precipTotal":null,"elev":187.0}}]}

set -eu

# shellcheck disable=SC1090
. "${MUNIN_LIBDIR}/plugins/plugin.sh"

if [ "${MUNIN_DEBUG:-0}" = 1 ]; then
    set -x
fi

PLUGIN_NAME="$(basename "${0}")"
STATION_ID="$(echo "${PLUGIN_NAME}" | sed 's/.*_//')"
# Use the station ID from the config only if the plugin doesn't specify one
STATION_ID=${STATION_ID:-${station_id:-KCASANFR1708}}

API_KEY=${api_key:-e1f10a1e78da46f5b10a1e78da96f525}
UNITS=${units:-metric}
BASE_URL=${base_url:-https://api.weather.com/v2/pws/observations/current}
CONNECT_TIMEOUT=${connect_timeout:-1}
if [ "${alerts:-yes}" = yes ]; then
	USE_ALERTS=yes
fi

UNITS_ARG='&units=m'
DISTANCE_UNIT='m'
PRESSURE_UNIT='hPa'
PRECIPITATION_UNIT='mm'
SPEED_UNIT='km/h'
TEMP_UNIT='°C'
# https://en.wikipedia.org/wiki/Wind_chill#/media/File:Windchill_effect_en.svg
WIND_CHILL_CAUTION=-35:
WIND_CHILL_DANGER=-60:
# https://en.wikipedia.org/wiki/Heat_index#Table_of_values
HEAT_INDEX_CAUTION=27
HEAT_INDEX_EXTREME_CAUTION=33
HEAT_INDEX_DANGER=41
HEAT_INDEX_EXTREME_DANGER=54
if [ "${UNITS}" = "imperial" ]; then
	UNITS_ARG='&units=e'
	DISTANCE_UNIT='ft'
	PRESSURE_UNIT='in'
	PRECIPITATION_UNIT='in'
	SPEED_UNIT='mph'
	TEMP_UNIT='°F'
	WIND_CHILL_CAUTION=-31:
	WIND_CHILL_DANGER=-76:w
	HEAT_INDEX_CAUTION=80
	HEAT_INDEX_EXTREME_CAUTION=91
	HEAT_INDEX_DANGER=105
	HEAT_INDEX_EXTREME_DANGER=130
fi
API_URL="${BASE_URL}?apiKey=${API_KEY}&stationId=${STATION_ID}&numericPrecision=decimal&format=json${UNITS_ARG}"

check_deps() {
	for CMD in curl jq; do
		if ! command -v "${CMD}" >/dev/null; then
			echo "no (${CMD} not found)"
		fi
	done
}

CURL_ARGS="-s --connect-timeout ${CONNECT_TIMEOUT}"
fetch() {
	# shellcheck disable=SC2086
	curl -f ${CURL_ARGS} "$@" \
		|| { echo "error fetching ${*}" >&2; false; }
}

config() {
	local STATION_INFO="in \(.neighborhood), \(.country) reported by station \(.stationID) (\(.lon), \(.lat), \(.${UNITS}.elev) m) at \(.obsTimeLocal) (\(.obsTimeUtc))"
	fetch "${API_URL}" | jq -r ".observations[0]
				| @text \"
multigraph wunderground_${STATION_ID}
graph_title Weather in \(.neighborhood)
graph_info Weather ${STATION_INFO}
graph_category weather
graph_vlabel Temperature / UV Index / Precipitation
graph_order temp=temperature.temp windChill=temperature.windChill heatIndex=temperature.heatIndex uv=uv_index.uv precipRate=precipitation.precipRate
temp.label Temperature [${TEMP_UNIT}]
windChill.label Wind chill [${TEMP_UNIT}]
heatIndex.label Heat index [${TEMP_UNIT}]
uv.label UV index
precipRate.draw AREA
precipRate.label Precipitation rate [${PRECIPITATION_UNIT} per hour]

multigraph wunderground_${STATION_ID}.air_humidity
graph_title Humidity in \(.neighborhood)
graph_info Humidity ${STATION_INFO}
graph_category weather
graph_args -l 0 --upper-limit 100
graph_vlabel Humidity [%]
humidity.label Humidity
humidity.min 0
humidity.max 100

multigraph wunderground_${STATION_ID}.location
graph_title Location of \(.stationID)
graph_info Track geographic coordinates of station \(.stationID); last: \(.lon), \(.lat), \(.${UNITS}.elev) ${DISTANCE_UNIT} at \(.obsTimeLocal) (\(.obsTimeUtc))
graph_category weather
graph_scale no
graph_vlabel lon/lat [°] / elevation [${DISTANCE_UNIT}]
lon.label Longitude [°]
lat.label Latitude [°]
elev.label Elevation [${DISTANCE_UNIT}]

multigraph wunderground_${STATION_ID}.precipitation
graph_title Precipitation in \(.neighborhood)
graph_info Precipitation ${STATION_INFO}
graph_category weather
graph_args -l 0 --base 1000
graph_vlabel Precipitation [${PRECIPITATION_UNIT} per hour]
precipRate.label Precipitation rate
avgRate.label Average precipitation rate
avgRate.type DERIVE
avgRate.draw AREA
avgRate.min 0
avgRate.cdef avgRate,36,*

multigraph wunderground_${STATION_ID}.air_pressure
graph_title Pressure in \(.neighborhood)
graph_info Pressure ${STATION_INFO}
graph_category weather
graph_scale no
graph_vlabel Pressure [${PRESSURE_UNIT}]
pressure.label Pressure

multigraph wunderground_${STATION_ID}.solar_radiation
graph_title Solar radiation in \(.neighborhood)
graph_info Solar radiation ${STATION_INFO}
graph_category weather
graph_args -l 0 --base 1000
graph_vlabel Solar radiation [W/m^2]
solarRadiation.label Solar radiation

multigraph wunderground_${STATION_ID}.temperature
temp.label Temperature
graph_title Temperature in \(.neighborhood)
graph_info Temperature ${STATION_INFO}
graph_category weather
graph_vlabel Temperature [${TEMP_UNIT}]
temp.label Temperature

dewpt.label Dew point
dewpt.info Temperature to which air must be cooled to become saturated with water vapor. When cooled further, the airborne water vapor will condense to form liquid water (dew). When air cools to its dew point through contact with a surface that is colder than the air, water will condense on the surface. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed rather than dew.

windChill.label Wind chill
windChill.info Represent the lowering of body temperature due to the passing-flow of lower-temperature air.  Wind chill numbers are always lower than the air temperature for values where the formula is valid. When the apparent temperature is higher than the air temperature, the heat index is used instead.
${USE_ALERTS:+
windChill.warning ${WIND_CHILL_CAUTION}
windChill.critical ${WIND_CHILL_DANGER}
}
windChillCaution.label Wind chill Caution
windChillCaution.info Danger of frostbite
windChillCaution.colour 5358f6
windChillCaution.line ${WIND_CHILL_CAUTION}
windChillDanger.label Wind chill Danger
windChillDanger.info Great danger of frostbite
windChillDanger.colour 5c1ff5
windChillDanger.line ${WIND_CHILL_DANGER}

heatIndex.label Heat index
heatIndex.info Index that combines air temperature and relative humidity, in shaded areas, to posit a human-perceived equivalent temperature, as how hot it would feel if the humidity were some other value in the shade.
${USE_ALERTS:+
heatIndex.warning ${HEAT_INDEX_EXTREME_CAUTION}
heatIndex.critical ${HEAT_INDEX_DANGER}
}
heatIndexCaution.label Heat index Caution
heatIndexCaution.info Fatigue is possible with prolonged exposure and activity. Continuing activity could result in heat cramps.
heatIndexCaution.colour ffff66
heatIndexCaution.line ${HEAT_INDEX_CAUTION}
heatIndexECaution.label Heat index Extreme Caution
heatIndexECaution.info Heat cramps and heat exhaustion are possible. Continuing activity could result in heat stroke.
heatIndexECaution.colour ffd700
heatIndexECaution.line ${HEAT_INDEX_EXTREME_CAUTION}
heatIndexDanger.label Heat index Danger
heatIndexDanger.info Heat cramps and heat exhaustion are likely; heat stroke is probable with continued activity.
heatIndexDanger.colour ff8c00
heatIndexDanger.line ${HEAT_INDEX_DANGER}
heatIndexEDanger.label Heat index Extreme Danger
heatIndexEDanger.info Heat stroke is imminent.
heatIndexEDanger.colour ff0000
heatIndexEDanger.line ${HEAT_INDEX_EXTREME_DANGER}

multigraph wunderground_${STATION_ID}.uv_index
graph_title UV Index in \(.neighborhood)
graph_info UV index ${STATION_INFO}
graph_category weather
graph_args -l 0
graph_vlabel UV index
uv.label UV index
uv.min 0
${USE_ALERTS:+
uv.warning 5
uv.critical 7
}
moderate.label Moderate
moderate.info Stay in shade near midday when the Sun is strongest. If outdoors, wear Sun protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 30+ sunscreen every 1.5 hours, even on cloudy days, and after swimming or sweating. Bright surfaces, such as sand, water, and snow, will increase UV exposure.
moderate.colour fff300
moderate.line 3
high.label High
high.info Reduce time in the Sun between 10 a.m. and 4 p.m. If outdoors, seek shade and wear Sun protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 30+ sunscreen every 1.5 hours, even on cloudy days, and after swimming or sweating. Bright surfaces, such as sand, water, and snow, will increase UV exposure.
high.colour f18b00
high.line 6
veryhigh.label Very high
veryhigh.info Minimize Sun exposure between 10 a.m. and 4 p.m. If outdoors, seek shade and wear Sun protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 30+ sunscreen every 1.5 hours, even on cloudy days, and after swimming or sweating. Bright surfaces, such as sand, water, and snow, will increase UV exposure.
veryhigh.colour e53210
veryhigh.line 8
extreme.label Extreme
extreme.info Try to avoid Sun exposure between 10 a.m. and 4 p.m. If outdoors, seek shade and wear Sun protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 30+ sunscreen every 1.5 hours, even on cloudy days, and after swimming or sweating. Bright surfaces, such as sand, water, and snow, will increase UV exposure.
extreme.colour b567a4
extreme.line 11

multigraph wunderground_${STATION_ID}.wind
graph_title Wind Speed in \(.neighborhood)
graph_info Wind speed and gusts ${STATION_INFO}
graph_category weather
graph_args -l 0 --base 1000
graph_vlabel Wind speed [${SPEED_UNIT}]
windSpeed.label Wind speed
windGust.label Wind gusts

multigraph wunderground_${STATION_ID}.wind_direction
graph_title Wind Direction in \(.neighborhood)
graph_info Wind direction ${STATION_INFO}
graph_category weather
graph_args --base 1000 -l 0 --upper-limit 360
graph_vlabel Wind [°]
winddir.label Wind origin
winddir.min 0
winddir.max 360
winddir.line 0
north.label North
north.colour COLOUR0
north.line 360
east.label East
east.colour COLOUR1
east.line 90
south.label South
south.colour COLOUR2
south.line 180
west.label West
west.colour COLOUR9
west.line 270
\""
}

get_data() {
	fetch "${API_URL}" | jq -r ".observations[0]
				| @text \"
multigraph wunderground_${STATION_ID}

multigraph wunderground_${STATION_ID}.air_humidity
humidity.value \(.humidity)

multigraph wunderground_${STATION_ID}.location
lon.value \(.lon)
lat.value \(.lat)
elev.value \(.${UNITS}.elev)

multigraph wunderground_${STATION_ID}.precipitation
precipRate.value \(.${UNITS}.precipRate)
avgRate.value \(.${UNITS}.precipTotal*100 | round)
avgRate.extinfo Immediate precipitation: \(.${UNITS}.precipRate) ${PRECIPITATION_UNIT}/h; Daily total: \(.${UNITS}.precipTotal) ${PRECIPITATION_UNIT}

multigraph wunderground_${STATION_ID}.air_pressure
pressure.value \(.${UNITS}.pressure)

multigraph wunderground_${STATION_ID}.solar_radiation
solarRadiation.value \(.solarRadiation)

multigraph wunderground_${STATION_ID}.temperature
temp.value \(.${UNITS}.temp)
dewpt.value \(.${UNITS}.dewpt)
windChill.value \(.${UNITS}.windChill)
heatIndex.value \(.${UNITS}.heatIndex)

multigraph wunderground_${STATION_ID}.uv_index
uv.value \(.uv)

multigraph wunderground_${STATION_ID}.wind
windSpeed.value \(.${UNITS}.windSpeed)
windGust.value \(.${UNITS}.windGust)

multigraph wunderground_${STATION_ID}.wind_direction
winddir.value \(.winddir)
\"" | sed 's/ null$/U/'
}

main () {
	check_deps

	case ${1:-} in
		config)
			config
			if [ "${MUNIN_CAP_DIRTYCONFIG:-0}" = "1" ]; then
				get_data
			fi
			;;
		*)
			get_data
			;;
	esac
}

main "${1:-}"