#!/bin/sh
# quiet-fan.sh - quiet the fan on a UniFi Dream Router (UDR)
#
# Gives Ubiquiti's own fan controller (uhwd) a calmer table via
# /etc/ustd/fan.conf. Nothing else on the router is changed.
#
#   sh quiet-fan.sh install   apply the quiet table (backs up any existing one)
#   sh quiet-fan.sh status    show temperature and fan speed, change nothing
#   sh quiet-fan.sh undo      remove the table, back to the factory curve
#
# Tested on one UDR, UniFi OS 5.1.33, October 2026. Use at your own risk.

CONF=/etc/ustd/fan.conf
H=/sys/class/hwmon/hwmon0
CPU=/sys/class/thermal/thermal_zone0/temp

measure() {
    for i in 1 2 3; do
        echo "    cpu=$(( $(cat $CPU) / 1000 ))C   pwm=$(cat $H/pwm1)   rpm=$(cat $H/fan1_input)"
        [ "$i" -lt 3 ] && sleep 5
    done
}

preflight() {
    if [ "$(id -u)" != 0 ]; then
        echo "Please run this as root (log in with: ssh root@<router-ip>)."; exit 1
    fi
    model=$(ubnt-device-info model_short 2>/dev/null)
    if [ "$model" != "UDR" ]; then
        echo "This router reports model '${model:-unknown}', not 'UDR'."
        echo "The fan table is only tested on the UniFi Dream Router. Nothing was changed."
        exit 1
    fi
    if [ ! -d /etc/ustd ] || [ ! -r $H/pwm1 ] || [ ! -r $H/fan1_input ] || [ ! -r $CPU ]; then
        echo "Could not find Ubiquiti's fan controller or the fan sensors. Nothing was changed."
        exit 1
    fi
}

load() {
    # usdbd reads fan.conf and hands it to uhwd; uhwd restarts itself for a second.
    systemctl restart usdbd
    echo "  Waiting 10 seconds for the fan to settle..."
    sleep 10
}

case "${1:-}" in
install)
    preflight
    others=$(systemctl list-units --all --plain --no-legend 2>/dev/null | awk '{print $1}' | grep -i fan)
    if [ -n "$others" ]; then
        echo "Found other fan services that would fight the new table:"
        echo "$others" | sed 's/^/    /'
        echo "Stop them first, e.g.: systemctl disable --now <name>. Nothing was changed."
        exit 1
    fi
    echo "Before:"; measure
    if [ -f $CONF ]; then
        backup=/root/fan.conf.backup-$(date +%Y%m%d-%H%M%S)
        cp $CONF "$backup" && echo "  Saved your existing table to $backup"
    fi
    cat > $CONF.new <<'CONF'
{
  "2":  ["cpu",   -40,  70,  16,  16],
  "3":  ["cpu",    70,  80,  39,  39],
  "4":  ["cpu",    80,  90,  70,  70],
  "5":  ["cpu",    90, 200, 100, 100],
  "12": ["flash", -40,  60,  16,  16],
  "13": ["flash",  60,  65,  39,  39],
  "14": ["flash",  65,  70,  70,  70],
  "15": ["flash",  70, 200, 100, 100],
  "PID": {"cpu": [82, -0.1, -0.1, 0.0, false, 2, 10],
          "flash": [62, -0.1, -0.1, 0.0, false, 2, 10]},
  "targets": {"1": ["all"]},
  "standby": 10,
  "calc_type": "table"
}
CONF
    if ! python3 -m json.tool $CONF.new > /dev/null 2>&1; then
        rm -f $CONF.new; echo "The new table did not validate. Nothing was changed."; exit 1
    fi
    mv $CONF.new $CONF
    load
    echo "After:"; measure
    echo
    echo "Done. Expect pwm=36 and roughly 600-700 rpm at normal temperatures."
    echo "rpm above 0 means the fan is spinning. To undo: sh $0 undo"
    ;;
status)
    if [ -f $CONF ]; then echo "Quiet table: installed ($CONF)"; else echo "Quiet table: not installed (factory curve)"; fi
    measure
    ;;
undo)
    preflight
    if [ ! -f $CONF ]; then echo "No quiet table installed. Nothing to undo."; exit 0; fi
    mv $CONF /root/fan.conf.removed-$(date +%Y%m%d-%H%M%S)
    load
    echo "Back to the factory curve:"; measure
    ;;
*)
    echo "Usage: sh $0 install | status | undo"; exit 1
    ;;
esac