#!/usr/bin/env bash

script_name="$(basename $(realpath $0))"
working_dir="$(dirname $(realpath $0))"

conf_file="${working_dir}/conf/${script_name%%.*}.conf"

LOCK_DIR="/tmp/$(basename $0).$$.LOCK"
log_file="${LOCK_DIR}/${script_name%%.*}.log"

PROBLEM_FOUND=false

LINK_UP=false
RESTART_CHECK_FILE="/tmp/${script_name%%.*}.NEED-RESTART"


# ----------
# Base Function(s)
# ----------

clean_up() {

   # Perform program exit housekeeping
   rm -rf "$LOCK_DIR"
   blank_line
   exit $1
}

usage() {


   [[ -n  "$1" ]] && error "$1"


   [[ $terminal ]] && echo -e "
\033[1mUsage:\033[m

   $(basename $0)

\033[1mDescription\033[m

   Script checks presence of some basic network settings and do some basic connectivity
   tests. If fundamental problems found, then restart machine if this i not the firts time.
   If this i the first time, file \033[1m$RESTART_CHECK_FILE\033[m is created.

\033[1mOptions\033[m

   No Options present

\033[1mFiles\033[m

   $conf_file: Configuration file

\033[1mExample:\033[m

   Chech connectivity of this machine

      $(basename $0)

"

   clean_up 1

}


echononl(){
   if $terminal ; then
      echo X\\c > /tmp/shprompt$$
      if [ `wc -c /tmp/shprompt$$ | awk '{print $1}'` -eq 1 ]; then
         echo -e -n "   $*\\c" 1>&2
      else
         echo -e -n "   $*" 1>&2
      fi
      rm /tmp/shprompt$$
   fi
}

error (){
   echo ""
   if $terminal ; then
      echo -e "   [ \033[31m\033[1mError\033[m ] $*"
   else
      echo "   [ Error ] $*"
   fi
   echo ""
}

warn (){
	echo ""
	if $terminal ; then
		echo -e "   [ \033[33m\033[1mWarn\033[m ]  $*"
	else
		echo "   [ Warn ]  $*"
	fi
	echo ""
}

info (){
	if $terminal ; then
		echo ""
		echo -e "   [ \033[32m\033[1mInfo\033[m ]  $*"
		echo ""
	fi
}

echo_ok() {
   if $terminal ; then
      echo -e "\033[75G[ \033[32mok\033[m ]"
   fi
}
echo_failed(){
   if $terminal ; then
      echo -e "\033[75G[ \033[1;31mfailed\033[m ]"
   fi
}
echo_warn() {
   if $terminal ; then
      echo -e "\033[75G[ \033[33m\033[1mwarn\033[m ]"
   fi
}
echo_skipped() {
   if $terminal ; then
      echo -e "\033[75G[ \033[37m\033[1mskipped\033[m ]"
   fi
}

trim() {
    local var="$*"
    var="${var#"${var%%[![:space:]]*}"}"   # remove leading whitespace characters
    var="${var%"${var##*[![:space:]]}"}"   # remove trailing whitespace characters
    echo -n "$var"
}

blank_line() {
   if $terminal ; then
      echo ""
   fi
}


# Check if at least one interface has physical link is up
#
online() {

   # Call this functionin a subshell to avoid exiting main programm
   #
   # Example: 
   #    $(online) && echo -e '\033[32m\033[1mOnline\033[m' || echo -e '\033[31m\033[1mOFFLINE\033[m'
   #
   find /sys/class/net/ -maxdepth 1 -mindepth 1 \
      ! -name "*lo*" \
      ! -name "*tun*" \
      ! -name "*veth*" \
      -exec sh -c 'cat "$0"/carrier 2>&1' {} \; | grep -q -E '^1$' && exit 0 
      
      # using ethtool also works:
      #
      #-exec sh -c 'ethtool $(basename "$0") 2>&1' {} \; | grep 'ink detected' | grep -i -q 'yes' && exit 0

}

reboot_system() {

   content_type='Content-Type: text/plain;\n charset="utf-8"'
   datum="$(date +"%d.%m.%Y")"
   from_address="root@$(hostname --long)"
   
   echo -e "To:${ADMIN_EMAIL}\n${content_type}\nSubject:[Connectivity Error] $datum - Reboot System\n$*" | /usr/sbin/sendmail -F "Connectivity Check" -f $from_address $ADMIN_EMAIL

   sleep 10
   /sbin/reboot -f

}

# ----------
# - Jobhandling
# ----------

# - Run 'clean_up' for signals SIGHUP SIGINT SIGTERM
# -
trap clean_up SIGHUP SIGINT SIGTERM

# - Create lock directory '$LOCK_DIR"
#
mkdir "$LOCK_DIR"


# ----------
# - Some checks ..
# ----------

# - Running in a terminal?
# -
if [[ -t 1 ]] ; then
   terminal=true
else
   terminal=false
fi

# - Print help?
# -
if [[ "$(trim $*)" = "-h" ]] || [[ "$(trim $*)" = "--help" ]] ; then
    usage
fi


# ==========
# - Begin Main Script
# ==========

# ----------
# - Headline
# ----------

if $terminal ; then
   echo ""
   echo -e "\033[1m----------\033[m"
   echo -e "\033[32m\033[1mRunning script \033[m\033[1m$script_name\033[32m .. \033[m"
   echo -e "\033[1m----------\033[m"
   echo ""
fi

# ----------
#  Read Configurations from $conf_file
# ----------


# - Give your default values here
# -
DEFAULT_IPV6_PRESENT=true
DEFAULT_CHECK_HOSTS="www.oopen.de www.google.de www.heise.de www.debian.org"
DEFAULT_ADMIN_EMAIL="argus@oopen.de"

echononl "Load Configurations from file '$(basename "$conf_file")'."
if [[ -f "$conf_file" ]]; then
   source "$conf_file"
   echo_ok
else
   echo_skipped
   msg="No configuration file found. Script default values where loaded.."
   if $terminal ; then
      echo ""
		echo -e "   [ \033[33m\033[1mWarn\033[m ]  $msg"
      echo ""
   fi
   #if [[ -z "$msg_warn" ]]; then
   #   msg_warn="$msg"
   #else
   #   msg_warn="$msg_warn
   #                $msg"
   #fi
fi

[[ -z "$IPV6_PRESENT" ]] && IPV6_PRESENT="$DEFAULT_IPV6_PRESENT"
[[ -z "$DNS_CHECK_HOSTS" ]] && DNS_CHECK_HOSTS="$DEFAULT_CHECK_HOSTS"
[[ -z "$HTTPS_CHECK_HOSTS" ]] && HTTPS_CHECK_HOSTS="$DEFAULT_CHECK_HOSTS"
[[ -z "$ADMIN_EMAIL" ]] && ADMIN_EMAIL="$DEFAULT_ADMIN_EMAIL"


blank_line


echononl "Check if at least one interface has physical link is up"
if ! $(online) ; then
   echo_failed
   PROBLEM_FOUND=true
else
   echo_ok
   LINK_UP=true
fi

if $LINK_UP ; then
   msg="Machine has at least one interface with physical link is up."
   if [[ -z "$msg_info" ]]; then
      msg_info="$msg"
   else
      msg_info="$msg_info
                   $msg"
   fi
else
   error 'Machine is OFFLINE'
   if [[ -f "$RESTART_CHECK_FILE" ]] ; then

      _file_mod_time=$(date --utc --reference=$RESTART_CHECK_FILE +%s)
      _now=$(date +%s)
      _delta=$(($_now-$_file_mod_time))
      echo "_delta=: $_delta"

      if [[ $_delta -gt 3900 ]] ; then
         touch "$RESTART_CHECK_FILE"
      else
         reboot_system "No interface with physical link is up - Machine is OFFLINE."
      fi
   else
      touch "$RESTART_CHECK_FILE"
   fi
   clean_up 1
fi


# ---
# Routing ok?
# ---

# Determin IPv4 default gateway(s)
#
DEFAULT_GW_4="$(/sbin/ip -4 route | awk '/default/ { print $3 }')"
if [[ -z "$DEFAULT_GW_4" ]] ; then
   DEFAULT_GW_4="$(/sbin/ip -4 route | awk '/nexthop/ { print $3 }')"
fi

declare -a DEFAULT_GW_4_ARR=()
for _ip in $DEFAULT_GW_4 ; do
   DEFAULT_GW_4_ARR+=("$_ip")
done

echononl "Check if IPv4 default route is set.."

if [[ ${#DEFAULT_GW_4_ARR[@]} -gt 0 ]] ; then
   echo_ok
   if [[ ${#DEFAULT_GW_4_ARR[@]} -eq 1 ]] ; then
      msg="Default IPv4 Gateway(s): ${DEFAULT_GW_4_ARR[@]}"
      if [[ -z "$msg_info" ]]; then
         msg_info="$msg"
      else
         msg_info="$msg_info
         
             $msg"
      fi
   else
      msg="Default IPv4 Gateway(s): ${DEFAULT_GW_4_ARR[0]}"
      for index in "${!DEFAULT_GW_4_ARR[@]}"; do 
         [[ $index -eq 0 ]] && continue
         msg="$msg
                                      ${DEFAULT_GW_4_ARR[$index]}"
      done
      if [[ -z "$msg_info" ]]; then
         msg_info="$msg"
      else
         msg_info="$msg_info
         
             $msg"
      fi
   fi
else
   echo_failed
   PROBLEM_FOUND=true

   error "No default route IPV4 is set."

   if [[ -f "$RESTART_CHECK_FILE" ]] ; then

      _file_mod_time=$(date --utc --reference=$RESTART_CHECK_FILE +%s)
      _now=$(date +%s)
      _delta=$(($_now-$_file_mod_time))
      echo "_delta=: $_delta"

      if [[ $_delta -gt 3900 ]] ; then
         touch "$RESTART_CHECK_FILE"
      else
         reboot_system "No default route IPv4 is set."
      fi
   else
      touch "$RESTART_CHECK_FILE"
   fi
   clean_up 1
fi


# Determin IPv6 default gateway(s)
#
if $IPV6_PRESENT ; then
   DEFAULT_GW_6="$(/sbin/ip -6 route | awk '/default/ { print $3 }')"

   declare -a DEFAULT_GW_6_ARR=()
   for _ip in $DEFAULT_GW_6 ; do
      DEFAULT_GW_6_ARR+=("$_ip")
   done

   echononl "Check if IPv6 default route is set.."
   if [[ ${#DEFAULT_GW_6_ARR[@]} -gt 0 ]] ; then
      echo_ok
      if [[ ${#DEFAULT_GW_6_ARR[@]} -eq 1 ]] ; then
         msg="Default IPv6 Gateway(s): ${DEFAULT_GW_6_ARR[@]}"
         if [[ -z "$msg_info" ]]; then
            msg_info="$msg"
         else
            msg_info="$msg_info
            
             $msg"
         fi
      else
         msg="Default IPv6 Gateway(s): ${DEFAULT_GW_6_ARR[0]}"
         for index in "${!DEFAULT_GW_6_ARR[@]}"; do 
            [[ $index -eq 0 ]] && continue
            msg="$msg
                                      ${DEFAULT_GW_6_ARR[$index]}"
         done

         if [[ -z "$msg_info" ]]; then
            msg_info="$msg"
         else
            msg_info="$msg_info
            
             $msg"
         fi

      fi
   else
      echo_warn

      msg="No default route IPv6 is set."
      if [[ -z "$msg_warn" ]]; then
         msg_warn="$msg"
      else
         msg_warn="$msg_warn
            
             $msg"
      fi
   fi

fi


# ---
# Nameservice ok?
# ---

FOUND_NS_PROBLEM=true

# Check if nameserver entry at /etc/resolv.conf ist present
# 
echononl "Check if nameserver entry at /etc/resolv.conf ist present.."
FIRST_NS="$(cat /etc/resolv.conf | awk '/^nameserver/ {print $2}' | awk 'NR == 1 {print; exit}')"
if [[ -n "$FIRST_NS" ]] ; then
   echo_ok
   FOUND_NS_PROBLEM=false
   
   msg="Found nameserver \033[1m$FIRST_NS\033[m at '/etc/resolv.conf'."
   if [[ -z "$msg_info" ]]; then
      msg_info="$msg"
   else
      msg_info="$msg_info
            
             $msg"
   fi

else
   echo_failed
   error "No nameserverentry at '/etc/resolv.conf' found."
fi


# Check if nameservice works..
#
echononl "Check if first nameserver works.."
if ! $FOUND_NS_PROBLEM ; then

   FOUND_NS_PROBLEM=true

   for _hostname in $DNS_CHECK_HOSTS ; do
      if [[ -n "$(dig +short @$FIRST_NS $_hostname)" ]] ; then
         FOUND_NS_PROBLEM=false
         break
      fi
   done

   if $FOUND_NS_PROBLEM ; then
      echo_failed
      PROBLEM_FOUND=true

      error "First nameserver located at /etc/resolv.conf does not work properly."

      if [[ -f "$RESTART_CHECK_FILE" ]] ; then

         _file_mod_time=$(date --utc --reference=$RESTART_CHECK_FILE +%s)
         _now=$(date +%s)
         _delta=$(($_now-$_file_mod_time))
         echo "_delta=: $_delta"

         if [[ $_delta -gt 3900 ]] ; then
            touch "$RESTART_CHECK_FILE"
         else
            reboot_system "First nameserver located at /etc/resolv.conf does not work properly."
         fi
      else
         touch "$RESTART_CHECK_FILE"
      fi
      clean_up 1
   else
      echo_ok

      msg="Nameserver works as expected."
      if [[ -z "$msg_info" ]]; then
         msg_info="$msg"
      else
         msg_info="$msg_info
            
             $msg"
      fi

   fi
else
   echo_skipped
   msg="Resolver test was not triggert because of nameserver problems.."
   if [[ -z "$msg_warn" ]]; then
      msg_warn="$msg"
   else
      msg_warn="$msg_warn
            
             $msg"
   fi
fi


# ---
# Website reachable?
# ---

if ! $FOUND_NS_PROBLEM ; then
   FOUND_CHECK_HOST_PROBLEM=true
else
   FOUND_CHECK_HOST_PROBLEM=false
fi

# Check if some websites reachable..
#
for _host in $HTTPS_CHECK_HOSTS ; do
   echononl "Check if website \033[1m$_host\033[m is reachable.."
   if ! $FOUND_NS_PROBLEM ; then

      case "$(curl -s --max-time 2 -I $_host | sed 's/^[^ ]*  *\([0-9]\).*/\1/; 1q')" in
         [23]) echo_ok
               FOUND_CHECK_HOST_PROBLEM=false
               break
               ;;
         5)    echo_failed
               ;;

         *)    echo_failed
               ;;
      esac
   else
      echo_skipped
      msg="Website accessibility test was not triggert because of nameserver problems.."
      if [[ -z "$msg_warn" ]]; then
         msg_warn="$msg"
      else
         msg_warn="$msg_warn
            
             $msg"
      fi
      break
   fi

done

if $FOUND_CHECK_HOST_PROBLEM ; then

   PROBLEM_FOUND=true

   error "No (configured) website could be reached."

   if [[ -f "$RESTART_CHECK_FILE" ]] ; then

      _file_mod_time=$(date --utc --reference=$RESTART_CHECK_FILE +%s)
      _now=$(date +%s)
      _delta=$(($_now-$_file_mod_time))
      echo "_delta=: $_delta"

      if [[ $_delta -gt 3900 ]] ; then
         touch "$RESTART_CHECK_FILE"
      else
         reboot_system "No website could be reached."
      fi
   else
      touch "$RESTART_CHECK_FILE"
   fi
   clean_up 1
else
   if ! $FOUND_NS_PROBLEM ; then
      msg="Extern Websites are reachable."
      if [[ -z "$msg_info" ]]; then
         msg_info="$msg"
      else
         msg_info="$msg_info
            
             $msg"
      fi
   fi
fi

if [[ -n "$msg_info" ]]; then
   info "$msg_info"
fi

if [[ -n "$msg_warn" ]]; then
   warn "$msg_warn"
fi


! $PROBLEM_FOUND && rm -f "$RESTART_CHECK_FILE"
clean_up 0