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

: << =cut

=head1 NAME

fronius - Plugin to monitor Fronius Solar inverter using the JSON Solar API.

The Solar API reports both an immediate power output reading at
time-of-request, and an incremental sum of daily and yearly produced energy.
This plugin uses the yearly energy sum as a DERIVE value, and calculates the
average power output during the last measurement interval. This will likely be
lower than the immediate reading, but the aggregation in weekly/monthly/yearly
graphs will be more correct.  The immediate power output is output as extra
information.

=head1 CONFIGURATION

	[fronius]
	env.inverter_base_url http://fronius	# this is the default
	env.host_name solar_inverter		# optional, host name to report data as in munin
	env.connect_timeout 1			# optional, amount to wait for requests, in seconds

=head1 CACHING

As the inverter may go to sleep at night, the initial service information is cached
locally, with a twelve-hour lifetime, before hitting the Solar API again. However,
if hitting the API to refresh the cache fails, the stale cache is used anyway,
to have a better chance of getting the config data out nonetheless.

=head1 CAVEAT

Only tested on a Fronius Primo and Fronius Symo.

=head1 AUTHOR

Olivier Mehani

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

=head1 LICENSE

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

=head1 MAGIC MARKERS

 #%# family=manual

=cut

# Example outputs
#
## http://fronius/solar_api/v1/GetInverterInfo.cgi
#GetInverterInfo='
#{
#   "Body" : {
#      "Data" : {
#         "1" : {
#            "CustomName" : "&#80;&#114;&#105;&#109;&#111;&#32;&#53;&#46;&#48;&#45;&#49;&#32;&#40;&#49;&#41;",
#            "DT" : 76,
#            "ErrorCode" : 0,
#            "PVPower" : 5200,
#            "Show" : 1,
#            "StatusCode" : 7,
#            "UniqueID" : "1098861"
#         }
#      }
#   },
#   "Head" : {
#      "RequestArguments" : {},
#      "Status" : {
#         "Code" : 0,
#         "Reason" : "",
#         "UserMessage" : ""
#      },
#      "Timestamp" : "2020-06-11T10:55:23+10:00"
#   }
#}
#'
#
## http://fronius/solar_api/v1/GetPowerFlowRealtimeData.fcgi
#GetPowerFlowRealtimeData='
#{
#   "Body" : {
#      "Data" : {
#         "Inverters" : {
#            "1" : {
#               "DT" : 76,
#               "E_Day" : 1201,
#               "E_Total" : 1201,
#               "E_Year" : 1201.4000244140625,
#               "P" : 2521
#            }
#         },
#         "Site" : {
#            "E_Day" : 1201,
#            "E_Total" : 1201,
#            "E_Year" : 1201.4000244140625,
#            "Meter_Location" : "unknown",
#            "Mode" : "produce-only",
#            "P_Akku" : null,
#            "P_Grid" : null,
#            "P_Load" : null,
#            "P_PV" : 2521,
#            "rel_Autonomy" : null,
#            "rel_SelfConsumption" : null
#         },
#         "Version" : "12"
#      }
#   },
#   "Head" : {
#      "RequestArguments" : {},
#      "Status" : {
#         "Code" : 0,
#         "Reason" : "",
#         "UserMessage" : ""
#      },
#      "Timestamp" : "2020-06-11T10:55:21+10:00"
#   }
#}
#'
#
## http://fronius/solar_api/v1/GetActiveDeviceInfo.cgi?DeviceClass=SensorCard
#GetActiveDeviceInfo='
#{
#   "Body" : {
#      "Data" : {}
#   },
#   "Head" : {
#      "RequestArguments" : {
#         "DeviceClass" : "SensorCard"
#      },
#      "Status" : {
#         "Code" : 0,
#         "Reason" : "",
#         "UserMessage" : ""
#      },
#      "Timestamp" : "2020-06-11T10:55:24+10:00"
#   }
#}
#'
#
## http://fronius/solar_api/v1/GetLoggerConnectionInfo.cgi
#GetLoggerConnectionInfo='
#{
#   "Body" : {
#      "Data" : {
#         "SolarNetConnectionState" : 2,
#         "SolarWebConnectionState" : 2,
#         "WLANConnectionState" : 2
#      }
#   },
#   "Head" : {
#      "RequestArguments" : {},
#      "Status" : {
#         "Code" : 0,
#         "Reason" : "",
#         "UserMessage" : ""
#      },
#      "Timestamp" : "2020-06-11T10:55:25+10:00"
#   }
#}
#'

set -eu

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

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

INVERTER_BASE_URL=${inverter_base_url:-http://fronius}
HOST_NAME=${host_name:-}
CONNECT_TIMEOUT=${connect_timeout:-1}

check_deps() {
	for CMD in curl jq recode; do
		if ! command -v "${CMD}" >/dev/null; then
			echo "no (${CMD} not found)"
			exit 0
		fi
	done
}

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

get_inverter_info() {
	fetch "${INVERTER_BASE_URL}/solar_api/v1/GetInverterInfo.cgi" \
		| recode html..ascii
}

get_power_flow_realtime_data() {
	fetch "${INVERTER_BASE_URL}/solar_api/v1/GetPowerFlowRealtimeData.fcgi"
	#echo "${GetPowerFlowRealtimeData}
}

# Run the command and arguments passed as arguments to this method, and cache
# the response.  The first argument is a timeout (in minutes) after which the
# cache is ignored and a new request is attempted.  If the request fails, the
# cache is used. If the timeout is 0, the request is always attempted, using
# the cache as a backup on failure.
cached() {
	timeout="${1}"
	shift
	fn="${1}"
	shift
	# shellcheck disable=SC2124
	args="${@}"

	# shellcheck disable=SC2039
	api_data=''
	# shellcheck disable=SC2039
	cachefile="${MUNIN_PLUGSTATE}/$(basename "${0}").${fn}.cache.json"
	if [ -n "$(find "${cachefile}" -mmin "-${timeout}" 2>/dev/null)" ]; then
		api_data=$(cat "${cachefile}")
	else
		# shellcheck disable=SC2086
		api_data="$("${fn}" ${args} \
			|| true)"

		if [ -n "${api_data}" ]; then
			echo "${api_data}" > "${cachefile}"
		else
			api_data=$(cat "${cachefile}")
		fi
	fi
	echo "${api_data}"
}

config() {
	if test -n "${HOST_NAME}"; then
		echo "host_name ${HOST_NAME}"
	fi
	# graph_period is not a shell variable
	cat <<'EOF'
graph_title Solar Inverter Output
graph_info Power generated from solar inverters
graph_total Total output
graph_category sensors
graph_vlabel Average output [W]
graph_args -l 0 --base 1000
EOF
cached 720 get_inverter_info | jq -r '.Body.Data
			   | to_entries[]
			   | @text "
inverter\(.key).label \(.value.CustomName)
inverter\(.key).info Power generated by the solar array (total size \(.value.PVPower / 1000) kW) connected to inverter \(.value.CustomName) (ID: \(.value.UniqueID))
inverter\(.key).cdef inverter\(.key),3600,*
inverter\(.key).type DERIVE
inverter\(.key).min 0
inverter\(.key).max \(.value.PVPower)
inverter\(.key).draw AREASTACK
"'
}

get_data() {
cached 0 get_power_flow_realtime_data | jq -r 'def roundit: . + 0.5 | floor;
			   .Body.Data.Inverters
			   | to_entries[]
			   | @text "
inverter\(.key).value \(.value.E_Year | roundit)
inverter\(.key).extinfo Immediate output: \(.value.P) W; Daily total: \(.value.E_Day | roundit) Wh; Yearly total: \(.value.E_Year / 1000 | roundit) kWh
"'
}

main () {
	check_deps

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

main "${1:-}"