docker-adsb-ultrafeeder/rootfs/usr/local/bin/autogain1090

#!/usr/bin/with-contenv bash
# shellcheck shell=bash

low="${READSB_AUTOGAIN_LOW_PCT:-2.5}"
high="${READSB_AUTOGAIN_HIGH_PCT:-6.0}"
ga=(0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6 -10)
tmp=/var/globe_history/autogain
mkdir -p $tmp
mkdir -p /var/globe_history/autogain

#work around stupid locale stuff
export LC_ALL=C

APP=dump1090-fa
if [[ -f /run/dump1090-fa/stats.json ]]; then
    APP=dump1090-fa
elif [[ -f /run/readsb/stats.json ]]; then
    APP=readsb
fi

stats=/run/$APP/stats.json

if [[ "$1" == "reset" ]]; then
    echo "Reset AutoGain - restarting with initial values and initialization process"
    rm -f /var/globe_history/autogain/* >/dev/null 2>&1
    pkill -f "s6-supervise autogain"
    exit 0
fi

if ! [[ -f $stats ]]; then echo "stats.json not found, is the decoder running?"; exit 1; fi

oldstrong=$(cat $tmp/strong 2>/dev/null)
oldtotal=$(cat $tmp/total 2>/dev/null)
if [[ -z $oldstrong ]] || [[ -z $oldtotal ]]; then
	oldstrong=0
	oldtotal=0
fi

if ! grep -qs total $stats | grep -qs -e strong_signals $stats; then
    echo "the decoder doesn't seem to be using an rtl-sdr device, can't help with that."
    exit 1
fi

# start=$(jq '.total.start' < $stats)
# end=$(jq '.total.end' < $stats)

strong=$(jq '.total.local.strong_signals' < $stats | tee $tmp/strong)
total=$(jq '.total.local.accepted | add' < $stats | tee $tmp/total)

if [[ -z $strong ]] || [[ -z $total ]]; then
    echo "unrecognized format: $stats"
    exit 1
fi

if ! awk "BEGIN{ exit  ($total < 1000) }"; then
    echo "The decoder hasn't been running long enough, wait a bit!"
    exit 0
fi


if (( oldtotal > total )) || (( oldstrong > strong )) || (( oldtotal == total )); then
	oldstrong=0
	oldtotal=0
fi

strong=$((strong - oldstrong))
total=$((total - oldtotal))

if [[ $total == 0 ]]; then
    percent=0
else
    percent=$(awk "BEGIN {printf \"%.3f\", $strong * 100 / $total}")
fi

strong=$percent

if [[ $strong == "nan" ]]; then echo "Error, can't automatically adjust gain!"; exit 1; fi


# Get the gain -- updated for docker-tar1090 use by kx1t
if [[ ! -f /var/globe_history/autogain/gain ]]; then
    oldgain="49.6"
    echo "Initial run. Starting point for adjusting gain is $oldgain"
else
    read -r oldgain < /var/globe_history/autogain/gain
    oldgain="${oldgain:-49.6}"    # needed for stupidity reasons
fi

gain_index=28
for i in "${!ga[@]}"; do
    if ! awk "BEGIN{ exit  (${oldgain} <= ${ga[$i]}) }"; then
        gain_index="${i}"
        break
    fi
done

if ! awk "BEGIN{ exit  (${oldgain} > 49.6) }"; then
    gain_index=28
fi

if [[ "$oldgain" == "-10" ]]; then
    gain_index=28
fi


if ! awk "BEGIN{ exit ($strong > $low) }" && ! awk "BEGIN{ exit ($strong < $high) }"; then
	echo "No gain change needed, ${strong}% percentage of messages >-3dB is in nominal range. (${low}% < ${strong}% < ${high}%)"
	exit 0

fi

if ! awk "BEGIN{ exit ($strong < $low) }" && [[ $gain_index == 28 ]]; then
    echo "Could have used some more gain, but gain is already at maximum! Strong (>-3dB) messages ${strong}% < ${low}%"
    exit 0
fi

if ! awk "BEGIN{ exit ($strong < $low) }"; then
    gain_index=$((gain_index+1))
    action=Increasing
fi

if ! awk "BEGIN{ exit ($strong > $high) }" && [[ $gain_index == 0 ]]; then
    echo "Could have used some lower gain, but gain already at minimum! Strong (>-3dB) messages ${strong}% > ${high}%"
    exit 0
fi

if ! awk "BEGIN{ exit ($strong > $high) }"; then
    gain_index=$((gain_index-1))
    action=Decreasing
fi

gain="${ga[$gain_index]}"

if [[ $gain == "" ]] || [[ $gain == "-10" ]]; then
    echo "Could have used some more gain, but gain is already at maximum! Strong (>-3dB) messages ${strong}% < ${low}%"
    exit 0
fi

# Set the gain -- updated for docker-tar1090 use by kx1t
echo "$gain" > /var/globe_history/autogain/gain
pkill readsb

#reset numbers
echo 0 > $tmp/strong
echo 0 > $tmp/total

if [[ "$action" == "Increasing" ]]; then
    echo "Increasing gain to $gain (${strong}% messages >-3dB exceed lower boundary of ${low}%)"
elif [[ "$action" == "Decreasing" ]]; then
    echo "Decreasing gain to $gain (${strong}% messages >-3dB exceed upper boundary of ${high}%)"
fi