#!/bin/bash
#
# Autosets system's timezone depending on the public IP.


LINK_IP="https://api.ipify.org/"
LINK_TZ="https://worldtimeapi.org/api/ip/"
USER_AGENTS=("Mozilla/5.0" "curl/7.67.0" "Wget/1.20.3")
SIZE=${#USER_AGENTS[@]}
REGEX_IP="[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}"
TZ_DEFAULT="UTC"
SOUND="/usr/share/sounds/Oxygen-Sys-Warning.ogg"
VERBOSE=0
PAUSE=3
TIMEOUT=10
LOGFILE=""


#######################################
# Prints out the usage message on invalid or -h/--help flags,
# Outputs:
#   Echoes usage message to STDOUT.
#######################################
print_usage() {
  echo "IP-to-Timezone switcher: autosets system's timezone on IP change."
  echo "Usage:"
  echo "  [--fallback=] -- sets timezone to fallback to  (default: \"$TZ_DEFAULT\");"
  echo "  [-p=, --pause=] -- sets pause in seconds between IP checks  (default: $PAUSE);"
  echo "  [-t=, --timeout=] -- sets timeout in seconds for cURL queries  (default: $TIMEOUT);"
  echo "  [--logfile=] -- toggles log dumping in a file;"
  echo "  [-v, --verbose] -- toggles verbosity;"
  echo "  [-h, --help] -- prints out this message."
}


#######################################
# Prints out logs in "[YYYY-MM-DD HH:MM:SS]  MESSAGE" format on -v/--verbose flag.
# Outputs logs in a file, located in :LOGFILE: (if it's not empty).
# Arguments:
#   MESSAGE to log.
# Globals:
#   VERBOSE
#   LOGFILE
# Outputs:
#   Logs out the MESSAGE to STDOUT.
#######################################
log() {
  log_string="[$(date -u '+%F %T')]  $*"
  [ $VERBOSE -eq 1 ] && printf "%s\n" "$log_string";
  [ -n "$LOGFILE" ] && echo "$log_string" >> "$LOGFILE"
}


#######################################
# Requests the current IP address from :LINK_IP: using randomized user-agent from :USER_AGENTS: list.
# Globals:
#   LINK_IP
#   USER_AGENTS
#   SIZE
# Returns:
#   Response of a cURL request to :LINK_IP:.
#######################################
get_ip() {
  index=$((RANDOM % SIZE))
  ua=${USER_AGENTS[$index]}
  myip=$(curl $LINK_IP --user-agent "$ua" --max-time $TIMEOUT -s)

  echo "$myip"
}


#######################################
# Requests a JSON response from :LINK_TZ: using randomized user-agent from :USER_AGENTS: list,
# gets (and cleans) the value of the "timezone" key,
# sets system's timezone to that value and
# sends a system notification with :SOUND: alarm.
# Globals:
#   LINK_TZ
#   USER_AGENTS
#   SIZE
#   SOUND
# Outputs:
#   Prints out status messages to STDOUT.
#######################################
set_timezone() {
  index=$((RANDOM % SIZE))
  ua=${USER_AGENTS[$index]}

  log "Requesting timezone data with user-agent \"$ua\"."
  TZ=$(curl $LINK_TZ --user-agent "$ua" --max-time $TIMEOUT -s | jq '.timezone')

  TZ=$(echo "${TZ:=$TZ_DEFAULT}" | cut -d'"' -f 2) &&
  printf "\nGot timezone \"%s\". Setting...\n" "$TZ" &&
  timedatectl set-timezone "$TZ" &&
  notify-send "Successfully changed your timezone to \"$TZ\"." &&
  paplay $SOUND &&
  printf "Successfully set the timezone to \"%s\".\n\n" "$TZ" &&
  log "Successfully got and set system's timezone to \"$TZ\"."
}


for i in "$@"; do
  case $i in
    --fallback=*)
      TZ_DEFAULT="${i#*=}" ;;
    -p=*| --pause=*)
      PAUSE="${i#*=}" ;;
    -t=*| --timeout=*)
      TIMEOUT="${i#*=}" ;;
    --logfile=*)
      LOGFILE="${i#*=}" ;;
    -v | --verbose)
      VERBOSE=1 ;;
    -h | --help | *)
      print_usage
      exit 0
      ;;
  esac
done

log "Running in verbose mode."
log "Will fallback to \"$TZ_DEFAULT\"."
log "CURL will timeout in $TIMEOUT seconds."
log "Will sleep for $PAUSE seconds."
[ -n "$LOGFILE" ] && log "Will log everything to $LOGFILE."

log "Trying to get the initial IP..."
myip_start=$(get_ip)
while [[ ! "$myip_start" =~ $REGEX_IP ]]; do
  log "Got invalid IP format: \"$myip_start\". Will continue."
  myip_start=$(get_ip)
done

log "Got the initial IP: \"$myip_start\"."
set_timezone

while true; do
  log "Updating IP..."
  myip=$(get_ip)
  if [[ ! "$myip" =~ $REGEX_IP ]]; then
    log "Got invalid IP format: \"$myip\". Will continue."
    continue
  fi
  log "Got IP: \"$myip\"."
  [ "$myip" != "$myip_start" ] && set_timezone && myip_start=$myip && log "Successfully updated IP."

  sleep "$PAUSE"
done