#!/bin/sh

# Default time to wait between temp checks in seconds.
DEFAULT_WAIT_TIME=60

TEMP_FILE="/tmp/gpio/cpu_temperature"
AP_STATUS_DIR="/tmp/temp-monitor/"
AP_ENABLED="ENABLED"
AP_DISABLED="DISABLED"
AP_STATUS_FILE="${AP_STATUS_DIR}ap_status"
AP_STATUS="$AP_ENABLED"
LAN_IFACE="lan0"
WIFI_IFACE="wlan0"
IFUP="ifup"
IFDOWN="ifdown"

LED_OVERTEMP_FILE="/tmp/gpio/ledcontrol/overtemperature"

err_log() {
  echo "$@" >&2
}

disable_iface() {
  local iface="$1"
  case "$iface" in
    "$LAN_IFACE")
      "$IFDOWN" "$LAN_IFACE"
      ;;
    "$WIFI_IFACE")
      if pidof hostapd > /dev/null; then
        stop wifi
      fi
      ;;
    *)
      ;;
  esac
}

enable_iface() {
  local iface="$1"
  case "$iface" in
    "$LAN_IFACE")
      "$IFUP" "$LAN_IFACE"
      ;;
    "$WIFI_IFACE")
      start wifi
      ;;
    *)
      ;;
  esac
}

cleanup() {
  rm -f "$AP_STATUS_FILE"
  exit $?
}

sigterm_handler() {
  err_log "INFO: Caught sigterm.  Exiting. . ."
  cleanup
}

sigint_handler() {
  err_log "INFO: Caught sigint.  Exiting. . ."
  cleanup
}

trap sigterm_handler TERM
trap sigint_handler INT

usage() {
  local progname="$(basename "$0")"
  cat << EOF >&2
Usage: $progname -l LOWER_BOUND -u UPPER_BOUND [ -n SECONDS ] [ -h ]

Temperature monitoring program.  When upper bound is reached, disables wifi
until lower bound is then reached, at which wifi is then reactivated.

Note: Behavior is undefined for non-integer arguments.

Options:

  -h                      Prints this message and exits.
  -l LOWER_BOUND          The lower bound, at which it is safe to reactivate
                          wifi.
  -u UPPER_BOUND          The upper bound, at which it is no longer safe to have
                          wifi active.
  -i SECONDS              The check interval in seconds.
                          Defaults to $DEFAULT_WAIT_TIME.
EOF
exit 1
}

# Prints an error if a command isn't runnable.
runnable_elog() {
  for cmd in "$@"; do
    if ! runnable "$cmd"; then
      err_log "ERROR: Cannot run $cmd. Quitting."
      return 1
    fi
  done
}

init() {
  mkdir -p "$AP_STATUS_DIR"
  touch "$AP_STATUS_FILE"
  runnable_elog "$IFUP" "$IFDOWN"
  return $?
}

check_integer() {
  for num in "$@"; do
    case "$num" in
      ''|*[!0-9]*)
        err_log "ERROR: $num is not an integer."
        return 1
        ;;
      *)
        ;;
    esac
  done
  return 0
}

get_temp() {
  cat "$TEMP_FILE" | {
    IFS="."
    # We only care about the main integer and not the decimal.
    read num decimal
    echo -n "$num"
  }
}

temp_check() {
  if [ ! -f "$TEMP_FILE" ]; then
    err_log "ERROR: $TEMP_FILE not found. Quitting."
    return 1
  fi
  local lower="$1"
  local upper="$2"
  local current_state="$(cat "$AP_STATUS_FILE")"
  local new_state=""
  local status_msg=""
  local temp="$(get_temp)"
  if [ -z "$current_state" ]; then
    current_state="$AP_ENABLED"
  fi

  if [ "$temp" -ge "$upper" ]; then
    new_state="$AP_DISABLED"
    status_msg="WARNING: Temp $temp exceeds upper limit ($upper) Disabling AP"
  elif [ "$temp" -lt "$lower" ]; then
    new_state="$AP_ENABLED"
    status_msg="Temp $temp is back in safe range.  Enabling AP"
  else # $lower <= $temp < $upper
    new_state="$current_state"
  fi

  # Only log when the status has changed.
  #TODO(abf): cwmpd brings up wifi when it starts, even if we're currently
  # overtemp. So we continuously kill wifi during overtemp condition (but only
  # if we explicitly see hostapd running, because we don't have the spare
  # memory to run /bin/wifi once a minute).
  if [ "$new_state" = "$current_state" -a "$new_state" = "$AP_ENABLED" ]; then
    return 0
  fi

  if [ "$new_state" != "$current_state" ]; then
    err_log "$status_msg"
  fi

  case $new_state in
    "$AP_ENABLED")
      enable_iface "$WIFI_IFACE"
      enable_iface "$LAN_IFACE"
      echo -n "$AP_ENABLED" > "$AP_STATUS_FILE"
      rm -f "$LED_OVERTEMP_FILE"
      ;;
    "$AP_DISABLED")
      disable_iface "$WIFI_IFACE"
      disable_iface "$LAN_IFACE"
      echo -n "$AP_DISABLED" > "$AP_STATUS_FILE"
      touch "$LED_OVERTEMP_FILE"
      ;;
    *)
      ;;
  esac
  err_log "temperature: $temp ap_status: $new_state"
  return 0
}

main() {
  local lower
  local upper
  local interval="$DEFAULT_WAIT_TIME"
  while getopts ":l:u:hi:" opt; do
    case "$opt" in
      l)
        lower="$OPTARG"
        ;;
      u)
        upper="$OPTARG"
        ;;
      i)
        interval="$OPTARG"
        ;;
      h|\?|:|*)
        usage
        ;;
    esac
  done
  if [ -z "$lower" ] || [ -z "$upper" ]; then
    err_log "ERROR: Must provide lower and upper bounds."
    usage
  fi
  check_integer "$lower" "$upper" "$interval" || usage
  if [ "$lower" -gt "$upper" ]; then
    err_log "ERROR: Lower bound must be less than or equal to upper bound."
    usage
  fi

  #-------- Main Loop ---------
  (init && err_log "Temp monitor initialized") || exit 1
  while true; do
    temp_check "$lower" "$upper" || exit 1
    sleep "$interval"
  done
}

main "$@"