#!/bin/bash

# checkup - check if sites are up.

function debug {
if false
then
  echo "DEBUG: $*"
fi
}

case $# in
  1)  config_file=$1 ;;
  *)  echo "Usage: checkup <config-file>"
      exit 1 ;;
esac

# Syntax of config file:
#
# Blank lines are ignored.
# Lines starting with # are ignored.
# Other lines consist of a command word and optional argumnets:
# mailto addr    - Specify email address that output should be sent to.
# rundir dirname - Specify directory in which runtime state is stored (default /var/run/checkup).
# sanity addr    - Ping this address first as a 'sanity check'.
# ping addr      - An address (hostname or ip) to ping.
# wget url       - A URL to retrieve.
# mail addr      - An SMTP server address to check.

PINGOPTS="-q -c 1 -w 30"


mailto=""
rundir="/var/run/checkup"
sanities=""
pings=""
declare -a wgets
mails=""

if [ ! -f "${config_file}" ]
then
  echo "Error: config file '${config_file}' does not exist / is not a file"
  exit 1;
fi

if [ ! -r "${config_file}" ]
then
  echo "Error: config file '${config_file}' is not readable"
  exit 1;
fi


stripped_config=`mktemp /tmp/checkup.conf.XXXXXX` || exit 1
trap "rm ${stripped_config}" EXIT

cat "${config_file}" | grep -v '^#' | grep -v '^[\t ]*$' > ${stripped_config} 

while read -r cmd args
do

  case ${cmd} in
    mailto) mailto+="${args} " ;;
    rundir) rundir=${args} ;;
    sanity) sanities+="${args} " ;;
    ping)   pings+="${args} " ;;
    wget)   wgets+=("${args}") ;;
    mail)   mails+="${args} " ;;
    *)      echo "Error: syntax error in configuration file: '${cmd}' not understood"
            exit 1 ;;
  esac

done < ${stripped_config}

case ${mailto} in
  "")  echo "Error: no email address specified."
       exit 1 ;;
  *)   ;;
esac


if [ ! -d "${rundir}" ]
then
  echo "Error: rundir '${rundir}' does not exist / is not a directory"
  exit 1
fi

for host in ${sanities}
do
  ping ${PINGOPTS} ${host} > /dev/null 2>&1
  case $? in
    0) ;;
    *) echo "Sanity-check ping $host failed, giving up"
       exit 1 ;;
  esac
done


cd "${rundir}"

report=""


function run_test {
  test_type=$1
  target=$2

  lastarg=`echo "${target}" | sed 's/.* //g'`
  statefile=${test_type}_`echo "${lastarg}" | tr '/' '_' `.state

  if [ -f "${statefile}" ]
  then
    read last_state last_timestamp up_report_interval down_report_interval < "${statefile}"
  else
    last_state="1"
    last_timestamp="0"
    up_report_interval="500"
    down_report_interval="500"
  fi

  timestamp=`date +%s`
  since_last_report=$((${timestamp} - ${last_timestamp}))
  #debug "since_last_report=${since_last_report}"

  if [ ${since_last_report} -lt ${down_report_interval} \
       -a ${since_last_report} -lt ${up_report_interval} ]
  then
    debug "skipping ${target}, neither report interval reached"
    return
  fi

  case ${test_type} in
    ping) debug "pinging ${target}"
          ping ${PINGOPTS} ${target} > /dev/null 2>&1
          case $? in
            0) testok="1" ;;
            *) testok="0" ;;
          esac ;;

    wget) debug "wgetting ${target}"
          wget -q --append-output /dev/null -O /dev/null -T 10 ${target}
          case $? in
            0) testok="1" ;;
            *) testok="0" ;;
          esac ;;

    mail) debug "mailing ${target}"
          echo -n | netcat -w 10 -q 15 "${target}" 25 | grep -q '^220'
          case $? in
            0) testok="1" ;;
            1) testok="0" ;;
            *) echo "Error: grep returned result $? for ${target}"
               exit 1 ;;
          esac ;;
  esac

  case "${testok}" in
    "0") if [ ${since_last_report} -ge ${down_report_interval} ]
         then
           case "${last_state}" in
             "0") report+="${test_type} ${lastarg} still down " ;;
             "1") report+="${test_type} ${lastarg} is DOWN " ;;
           esac
           up_report_interval=300
           down_report_interval="${down_report_interval}0"
           echo "${testok} ${timestamp} ${up_report_interval} ${down_report_interval}" > ${statefile}
         fi ;;

    "1") if [ ${since_last_report} -ge ${up_report_interval} ]
         then
           case "${last_state}" in
             "0") report+="${test_type} ${lastarg} is UP " ;;
             "1") ;;
           esac
           down_report_interval=300
           up_report_interval="${up_report_interval}0"
           echo "${testok} ${timestamp} ${up_report_interval} ${down_report_interval}" > ${statefile}
         fi ;;
  esac
}


for host in ${pings}
do
  run_test ping "${host}"
done

for url in "${wgets[@]}"
do
  run_test wget "${url}"
done

for host in ${mails}
do
  run_test mail "${host}"
done



if [ "${report}" ]
then

  debug "report: ${report}"
  echo "${report}" | mail -s "Checkup report: " ${mailto}

fi