gas_price_de_

#!/bin/sh

# -*- sh -*-                                                                                                                                  
# vim: ft=sh                                                                                                                                  
                                                                                                                                              
: <<=cut                                                                                                                                      
                                                                                                                                              
=head1 NAME

gas_price_de_ 

=head1 DESCRIPTION

Graph prices of certain fuel types at gas stations within an area (defined by center 
and radius) in germany using with munin. This uses the http://tanken.t-online.de API.

=head1 PREREQUISITES

This plugin uses the "xmllint" program provided by 
libxml2 (http://www.xmlsoft.org) and the "wget" utility
(http://www.gnu.org/software/wget/)

=head1 CONFIGURATION

 The filename must be in this format: gas_price_de_ID with
 ID beeing a freely choosable string to allow creating 
 multiple graphs and to set the title of the graph. ID may be empty.

The following environment variables are used by this plugin
 
 latitude            - center latitude of area to query   [52.527567]
 longitude           - center longitude of area to query  [13.416131]
 radius              - size of area (in kilometer)        [1]
 fuel_type           - The type of fuel                   [super]
                       Supported values are:
                          diesel
                          super
                          super%20e10
                          superplus
                          autogas
                          biodiesel
                          lkw-diesel
                          dieselplus

=head2 CONFIGURATION EXAMPLES

 [gas_price_de_*]
  env.latitude 52.527567
  env.longitude 13.416131
  env.radius 5
  env.fuel_type autogas

=head1 AUTHOR

Copyright (C) 2013 D.Hiepler

=head1 LICENSE

GPLv2

=head1 MAGICK MARKERS

 #%# family=manual

=cut

. $MUNIN_LIBDIR/plugins/plugin.sh


# API url
URL="http://tanken.t-online.de/api/v1/search.xml"

# maximum age of returned price (be sure to set this large enough
# to avoid empty queries) Currently the API will return a single
# most recent price per gas station/fuel type within this range
PRICE_AGE="48"



# parse ID
id=${0##*gas_price_de_}

# default values
latitude=${latitude:-52.527567}
longitude=${longitude:-13.416131}
radius=${radius:-5}
fuel_type=${fuel_type:-super}

# build query
QUERY="${URL}?lat=${latitude}&lng=${longitude}&radius=${radius}&price_age=${PRICE_AGE}&fuels=${fuel_type}"

# array of gas station IDs
GAS_STATIONS=()

# temporary XML file
XML=$(tempfile -p gas)


# install trap
trap cleanup EXIT

# clean up handler
function cleanup()
{
	if [ -e ${XML} ] ; then rm "${XML}" ; fi
}

# fatal error handler
function die()
{
	echo "$1"
	exit -1
}

# fetch XML from API
function query()
{
	# fetch file to tempfile
	wget --quiet "${QUERY}" -O "${XML}" || die "wget \"${QUERY}\" failed"
}

# build array of GAS_STATION IDs from XML
function parseGasStations()
{
	# query
	query || die "query failed"

	# parse IDs from XML
	for ident in $(xmllint --xpath "/search/gasStations/*/@ident" ${XML}) ; do
		sid=${ident##*ident=\"}
		sid=${sid%%\"*}
		GAS_STATIONS[${#GAS_STATIONS[@]}]=${sid}
	done

	if [ ${#GAS_STATIONS[@]} -eq 0 ] ; then die "no gas stations found in query" ; fi
}

# output configuration
function config()
{
	# build array of gas station IDs in ${GAS_STATIONS}
	parseGasStations || die "parsing gas stations failed"

cat <<EOS
graph_title ${id:-"Fuel prices"}
graph_category fuelprices
graph_vlabel Euro/Liter
graph_info Prices for ${fuel_type}, ${radius}km around ${latitude},${longitude}
EOS

	# process every gas station found
	for sid in ${GAS_STATIONS[@]} ; do 
		# get name
		name=$(xmllint --xpath "string(/search/gasStations/gasStation[@ident=\"${sid}\"]/@name)" ${XML})
		# get address
		street=$(xmllint --xpath "string(/search/gasStations/gasStation[@ident=\"${sid}\"]/@street)" ${XML})
		zip=$(xmllint --xpath "string(/search/gasStations/gasStation[@ident=\"${sid}\"]/@zip)" ${XML})
		city=$(xmllint --xpath "string(/search/gasStations/gasStation[@ident=\"${sid}\"]/@city)" ${XML})

		# handle errors
		if [ -z "${name}" ] ; then die "gas station has empty name" ; fi

		echo "${sid}.label ${name}"
		echo "${sid}.info ${street} - ${zip} ${city}"
	done
}


# output the last known price
function output()
{
	# build array of gas station IDs in ${GAS_STATIONS}
	parseGasStations || die "parsing gas stations failed"

	# process every gas station found
	for sid in ${GAS_STATIONS[@]} ; do 
		# get current price
		price=$(xmllint --xpath "string(/search/gasStations/gasStation[@ident=\"${sid}\"]/fuels/fuel/@price)" ${XML})

		# handle errors
		if [ -z "${price}" ] ; then die "no price found" ; fi

		echo "${sid}.value ${price}"
	done
}





# ----------------------------------------------------------------------------

case $1 in
	"config")
		config
		exit
		;;
	*)
		output
		exit
		;;
esac