#!/bin/bash

#Zeb H.
#Dell MD1200 DAS fan control - read temps, set fan speed to match.
#Drives the curve off drive temperature, falls back to the enclosure backplane sensors.
#Usage: das_fanctl.sh [loop|once|temps|disks|selftest]   (default: loop)

source /root/fan_speed/functions.sh

PORT=${PORT:-/dev/ttyS1}
LOG=/root/fan_speed/log/das_fan.log
CHECK_INTERVAL=30              # seconds between temperature readings
KEEPALIVE_INTERVAL=5           # re-send _shutup this often, the DAS forgets it otherwise
LOW_FAN_SPEED=10
HIGH_FAN_SPEED=60

# Disks in the enclosure - anything behind the DAS SAS expander. The server's own
# drives hang off pci-...-scsi-* instead, so this glob does not pick them up.
# Drives in THIS shelf. "-sas-exp" alone is not enough to identify an enclosure:
# a server's own backplane is often behind an expander too, and on iz-pve0 the
# internal drives sit on pci-0000:02:00.0 while the shelf is on 04:00.0. Name the
# shelf's HBA explicitly on any host with more than one.
DISK_GLOB=${DISK_GLOB:-/dev/disk/by-path/*-sas-exp*-lun-0}
# The ramp must START ABOVE the drives' normal working range, or every degree of
# ordinary drift crosses it and the fans cycle audibly. The 4x8TB + 1x16TB set in
# this shelf works at 30-41c against a 60c limit, so 44 leaves 3c of clearance.
# The previous 40-50c was sized for an 8x2TB set that idled at 32-39c; the newer
# drives run warmer and sat exactly on the old ramp start, flipping 10<->15%
# every 30 seconds.
DISK_LOW_TEMPERATURE_THRESHOLD=${DISK_LOW_TEMPERATURE_THRESHOLD:-44}
DISK_HIGH_TEMPERATURE_THRESHOLD=${DISK_HIGH_TEMPERATURE_THRESHOLD:-56}

# Backplane air sensors, only used when no disk will answer (all spun down, smartctl gone)
BP_LOW_TEMPERATURE_THRESHOLD=30
BP_HIGH_TEMPERATURE_THRESHOLD=45

# Hold the current speed unless the request moves this far. The curve is ~4%/degC
# even after widening, so without damping a single degree of drive drift moves the
# fan. A re-settle is allowed periodically, downward only - see settle_fan_speed.
FAN_SPEED_DEADBAND=${FAN_SPEED_DEADBAND:-8}
SETTLE_INTERVAL=${SETTLE_INTERVAL:-300}

SPEED=$LOW_FAN_SPEED
SPEED_SET_AT=0

# Only one talker on the serial line (detach screen/attachDAS.sh first). Taken
# only by the subcommands that actually open the port - selftest and disks do
# not, and refusing to run them while the service is up is just unhelpful.
claim_serial_port() {
  exec 9>/run/das_fanctl.lock
  flock -n 9 || { echo "another das_fanctl is running (or $PORT is busy)" >&2; exit 1; }
  stty -F $PORT 38400 raw -echo -echoe -echok -echoctl -echoke
}

# True when the request has moved far enough to act on. Full speed is never held back.
fan_speed_changed_enough() {
  local wanted=$1 applied=$2 delta
  [ "$wanted" -ge "$HIGH_FAN_SPEED" ] && return 0
  delta=$((wanted - applied)); [ "$delta" -lt 0 ] && delta=$((-delta))
  [ "$delta" -ge "$FAN_SPEED_DEADBAND" ]
}

# settle_fan_speed <wanted> <applied> <settle due, 0|1>
# A symmetric deadband catches the fan on the way up and never lets it back down,
# which leaves the shelf permanently louder than it needs to be. So periodically -
# and only downward - let it settle to what is actually wanted. Upward moves always
# require a full deadband crossing.
settle_fan_speed() {
  local wanted=$1 applied=$2 due=$3
  # Declared separately on purpose: in `local a=$1 b=$a` the right-hand sides are
  # expanded before the locals exist, so b would get the OUTER scope's a (empty).
  local target=$applied
  fan_speed_changed_enough "$wanted" "$applied" && target=$wanted
  if [ "$due" = 1 ] && [ "$wanted" -lt "$target" ]; then target=$wanted; fi
  echo "$target"
}

# Fire and forget - the DAS answers with a bare prompt, nothing worth reading
set_fan() { printf '_shutup %s\r' "$1" > $PORT; }

# Send a command, return whatever the DAS says back
das_cmd() {
  local out; out=$(mktemp)
  timeout 3 cat $PORT > "$out" &
  local pid=$!
  sleep 0.2
  printf '%s\r' "$1" > $PORT
  wait $pid
  cat "$out"; rm -f "$out"
}

# Hottest drive-backplane sensor from a _temp_rd readout on stdin.
# ponytail: BP_* only - EXP0 (SAS expander) idles ~59c and would peg the fans,
# SIM0 is the enclosure module. Add them here if drives ever run cool but the DAS cooks.
hottest_bp() {
  awk -F'[=c]' '/BP_[0-9]+\[/ {gsub(/ /,"",$2); if ($2+0 > m) m = $2+0} END {print m+0}'
}

# Hottest drive in the enclosure, 0 if nothing answered.
# -n standby so a sleeping drive is skipped rather than spun up just to be measured.
# SATA reports attribute 194, SAS reports "Current Drive Temperature".
hottest_disk() {
  local link dev temp max=0
  for link in $DISK_GLOB; do
    [ -e "$link" ] || continue
    dev=$(readlink -f "$link")
    temp=$(smartctl -n standby -A "$dev" 2>/dev/null |
           awk '/Temperature_Celsius/ {print $10; exit} /Current Drive Temperature/ {print $4; exit}')
    [ -n "$temp" ] && [ "$temp" -gt "$max" ] 2>/dev/null && max=$temp
  done
  echo $max
}

# Read temps, recalculate SPEED, apply it
one_pass() {
  local disk bp source temp low high
  disk=$(hottest_disk)
  if [ "$disk" -gt 0 ]; then
    source=disk; temp=$disk
    low=$DISK_LOW_TEMPERATURE_THRESHOLD; high=$DISK_HIGH_TEMPERATURE_THRESHOLD
  else
    bp=$(das_cmd _temp_rd | hottest_bp)
    if [ "$bp" -le 0 ] 2>/dev/null; then
      echo "$(date +'%Y-%m-%d %H:%M:%S') || no disk or backplane reading, holding fan at ${SPEED}%" >> $LOG
      return 1
    fi
    source=backplane; temp=$bp
    low=$BP_LOW_TEMPERATURE_THRESHOLD; high=$BP_HIGH_TEMPERATURE_THRESHOLD
  fi

  local want now due=0 prev=$SPEED held=""
  want=$(calculate_interpolated_fan_speed "$temp" $low $high $LOW_FAN_SPEED $HIGH_FAN_SPEED)
  now=$(date +%s)
  [ $((now - SPEED_SET_AT)) -ge "$SETTLE_INTERVAL" ] && due=1
  SPEED=$(settle_fan_speed "$want" "$SPEED" "$due")
  { [ "$SPEED" != "$prev" ] || [ "$due" = 1 ]; } && SPEED_SET_AT=$now
  [ "$SPEED" = "$want" ] || held=" held, want $want"

  set_fan "$SPEED"
  echo "$(date +'%Y-%m-%d %H:%M:%S') || DAS ${source}:${temp}c | Fan Speed:${SPEED}${held}" >> $LOG
  echo "DAS ${source}:${temp}c -> fan ${SPEED}%${held}"
}

selftest() {
  local canned='  BP_1[2] = 30c
  BP_2[3] = 44c
  SIM0[0] = 36c
  EXP0[4] = 59c
  AVG = 39c'
  [ "$(printf '%s' "$canned" | hottest_bp)" = 44 ] || { echo "FAIL: bp parser"; exit 1; }
  [ "$(printf '%s' 'garbage' | hottest_bp)" = 0 ] || { echo "FAIL: bp parser on junk"; exit 1; }
  [ "$(calculate_interpolated_fan_speed 40 40 50 10 60)" = 10 ] || { echo "FAIL: low clamp"; exit 1; }
  [ "$(calculate_interpolated_fan_speed 55 40 50 10 60)" = 60 ] || { echo "FAIL: high clamp"; exit 1; }
  [ "$(calculate_interpolated_fan_speed 45 40 50 10 60)" = 35 ] || { echo "FAIL: midpoint"; exit 1; }
  [ "$(hottest_disk)" -gt 0 ] || { echo "FAIL: no disk temperatures readable"; exit 1; }
  HIGH_FAN_SPEED=60
  [ "$(settle_fan_speed 15 10 0)" = 10 ] || { echo "FAIL: 5% drift should hold"; exit 1; }
  [ "$(settle_fan_speed 18 10 0)" = 18 ] || { echo "FAIL: 8% rise should be adopted"; exit 1; }
  [ "$(settle_fan_speed 60 10 0)" = 60 ] || { echo "FAIL: full speed always adopted"; exit 1; }
  [ "$(settle_fan_speed 26 30 0)" = 30 ] || { echo "FAIL: small fall should hold"; exit 1; }
  [ "$(settle_fan_speed 26 30 1)" = 26 ] || { echo "FAIL: should settle down when due"; exit 1; }
  [ "$(settle_fan_speed 34 30 1)" = 30 ] || { echo "FAIL: must not drift up on a settle"; exit 1; }
  echo "selftest OK"
}

case "${1:-loop}" in
  selftest|disks) ;;          # no serial access
  *) claim_serial_port ;;
esac

case "${1:-loop}" in
  temps)    das_cmd _temp_rd ;;
  disks)    for l in $DISK_GLOB; do
              d=$(readlink -f "$l")
              printf '%-12s %s\n' "$d" "$(smartctl -n standby -A "$d" 2>/dev/null |
                awk '/Temperature_Celsius/ {print $10"c"; exit} /Current Drive Temperature/ {print $4"c"; exit}')"
            done; echo "hottest: $(hottest_disk)c" ;;
  once)     one_pass ;;
  selftest) selftest ;;
  loop)     while true; do
              one_pass
              # keepalive between readings - matches the old 5s timer cadence
              for _ in $(seq $((CHECK_INTERVAL / KEEPALIVE_INTERVAL))); do
                sleep $KEEPALIVE_INTERVAL
                set_fan "$SPEED"
              done
            done ;;
  *)        echo "usage: $0 [loop|once|temps|disks|selftest]" >&2; exit 1 ;;
esac