#!/bin/bash

#
# Copyright (c) 2018 leopold@shdx.org
# Author: Der_Leopold
#
# This script tries to read sensor values from a 1wire bus and writes the results
# and a timestamp to a file. It is intended to be executed periodically, for
# example via crontab.
#

# Retry up to n times if the reading fails
RETRY=3

# Number of seconds to wait between retries
DELAY=2

# Specify the temperature range where you expect the sensors will be operating
# This is simply used as a safeguard to detect implausible sensor readings
MINTEMP=-30
MAXTEMP=40

# Interface that is connected to the 1wire bus
USETTY=/dev/ttyUSB0

# Location of the digittemp config file with data about the sensors
DIGITEMPCONF="/etc/digitemp.conf"

# Command to use for reading the sensors
CMD="sudo /usr/bin/digitemp_DS9097"
CMDOPTS=" -q -s $USETTY  -c $DIGITEMPCONF"

# Define sensors that should be queried
# Format: [<Label>]=<Id>
declare -A SENSORS=( [0]=LuftTemp [1]=WasserTemp [2]=BodenTemp )

# Location where the readings should be stored
OUTFILE="output"
RESULT=""

#
# no configuration/changes should be necessary below this line
#

cd "$(dirname "$0")";
touch "$OUTFILE" 2> /dev/null

if [ ! -w $OUTFILE ]; then
    echo "Error: output file '$OUTFILE' not writeable"
    exit 1
fi

function read_sensor () {
    OUTPUT=`$CMD $CMDOPTS -t $SENSORID`
    VALUE=`echo "$OUTPUT" | awk -F "C: " '{print $2}' | awk -F " F:" '{print $1}'`
    CNT=$(($CNT+1))
}

function check_output () {
    if [[ $OUTPUT =~ fail ]] || [[ $OUTPUT =~ owAcquire ]] || [ ${VALUE%.*} -lt $MINTEMP ] || [ ${VALUE%.*} -gt $MAXTEMP ]; then
        if [ $CNT -le $RETRY ]; then
            sleep $DELAY
            read_sensor
            check_output
        else
            RESULT="$RESULT${SENSORS[$SENSORID]}=Error\n"
        fi
    fi
}

function store_result () {
    RESULT="$RESULT${SENSORS[$SENSORID]}=${VALUE}\n"
}

function write_to_file () {
    echo "Timestamp="`date +%s` > "$OUTFILE"

    echo -e "$RESULT" >> "$OUTFILE"
}

for SENSORID in  "${!SENSORS[@]}"
do
    CNT=0
    read_sensor
    check_output
    store_result
    sleep $DELAY
done
write_to_file