mqtt-publish

#!/bin/sh
#
# Publish tfrec datagram as MQTT message
#
# Arguments: tfrec datagram, e.g.
#   id   temp  hum seq lowbat rssi flags time
#   5158 +23.8 59  10  0      79   0     1496588364
#
set -eu

MQTT_TOPIC="${MQTT_TOPIC:-tfrec}"
MQTT_TOPIC_APPEND_ID="${MQTT_TOPIC_APPEND_ID:-true}"
MQTT_TOPIC_APPEND_FORMAT="${MQTT_TOPIC_APPEND_FORMAT:-true}"

FORMAT_RAW="${FORMAT_RAW:-false}"
FORMAT_RAW_SEPARATOR="${FORMAT_RAW_SEPARATOR:- }"
FORMAT_JSON="${FORMAT_JSON:-true}"
FORMAT_JSON_LOWBAT_AS_BOOLEAN="${FORMAT_JSON_LOWBAT_AS_BOOLEAN:-false}"

CLIENT_MOSQUITTO="${CLIENT_MOSQUITTO:-true}"
# LOG_FILE (optional)
LOG_FORMAT="${LOG_FORMAT:-%s %s\n}"

cancel() {
  # local set is required because in global has no effect, at least in busybox ash
  set -eu
  echo >&2 "Error: ${@}"
  return 1
}

publish() {
  format="${1}"
  id="${2}"
  message="${3}"

  topic="${MQTT_TOPIC}"
  [ ! "${MQTT_TOPIC_APPEND_ID}"     = 'true' ] || topic="${topic}/${id}"
  [ ! "${MQTT_TOPIC_APPEND_FORMAT}" = 'true' ] || topic="${topic}/${format}"
  if [ "${CLIENT_MOSQUITTO}" = 'true' ]; then
    printf "%s " '-t' "${topic}" '-m' "'${message}'" "${MQTT_OPTIONS-}" | xargs mosquitto_pub
  fi
  if [ "${LOG_FILE-}" ]; then
    printf -- "${LOG_FORMAT}" "${topic}" "${message}" >>"${LOG_FILE}"
  fi
}

build_raw_message() {
  printf "%s${FORMAT_RAW_SEPARATOR}" "${@}"
}

build_json_message() {
  [ ! "${#}" -lt "8" ] || cancel "too few arguments: '${@}'"
  echo "${@}" | while read sensor_id temperature humidity seq lowbat rssi flags timestamp; do
    # remove the leading '+' to get a valid JSON number
    temperature="${temperature#+}"
    if [ "${FORMAT_JSON_LOWBAT_AS_BOOLEAN}" = 'true' ]; then
      if [ "${lowbat}" -eq 1 ]; then lowbat='true'; else lowbat='false'; fi
    fi
    printf '{ "sensor_id":"%s", "temperature":%.9g, "humidity":%.9g, "seq":%i, "lowbat":%s, "rssi":%i, "flags":%i, "timestamp":%i }' \
            "${sensor_id}"    "${temperature}"    "${humidity}"    "${seq}"  "${lowbat}"  "${rssi}"  "${flags}"  "${timestamp}"
  done
}

main() {
  [ -n "${1-}" ] || cancel "No arguments"
  if [ "${FORMAT_RAW}"  = 'true' ]; then
    publish 'raw' "${1}" "$(build_raw_message "${@}")"
  fi
  if [ "${FORMAT_JSON}" = 'true' ]; then
    publish 'json' "${1}" "$(build_json_message "${@}")"
  fi
}

main "${@}"