#!/bin/bash
#

# this is going to be a rewrite of this:
# https://github.com/defsdoor/letsencrypt-autorenew/blob/master/get_certificates

# example file mycerts:
## EMAIL admin@example.com
## HOSTS www.example.com
## EMAIL admin@mail.example.com
## HOSTS mail.example.com
##  imap.example.com pop3.example.com smtp.example.com

# would like to have this script work with new setups, still using the certonly setup - I don't want the webserver down
# while it's the cert(s) for the domains...
LEDIR=/opt/letsencrypt
CONF_FILE=/etc/letsencrypt/mycerts
LEROOT=/etc/letsencrypt/live
RENEW_DAYS_LEFT=8

function die {
  echo "$*"
  exit 1
}

function generate {
  typeset EMAIL="$1"
  typeset HOSTS="$2"

  CMD=""
  for H in $HOSTS
  do
    CMD="$CMD -d $H"
  done

  ./letsencrypt-auto certonly --renew-by-default --agree-tos --webroot --email $EMAIL $CMD --webroot-path /var/www/content/letsencrypt
}

function check_same_hosts {
  typeset CERT="$1"
  typeset HOSTS="$2"

  CERT_HOSTS="$(get_hosts_from_cert $CERT)"
  SORTED_CERT_HOSTS="$(sort_hosts "$CERT_HOSTS")"
  SORTED_HOSTS="$(sort_hosts "$HOSTS")"

  if [[ "$SORTED_HOSTS" == "$SORTED_CERT_HOSTS" ]]
  then
    return 0
  else
    return 1
  fi
}

function check_expiring_soon {
  typeset CERT="$1"

  EXPIRY_DATE=$(date -d "$(openssl x509 -in $CERTIFICATE -text | sed '/Not After/{s/^.*: //g;p};d')" '+%Y%m%d%H%M%S')
  typeset RENEW_DATE=$(date -d "now +$RENEW_DAYS_LEFT days"  '+%Y%m%d%H%M%S')

  if [[ $EXPIRY_DATE < $RENEW_DATE ]]
  then
    return 1
  else
    return 0
  fi
}

function sort_hosts {
  typeset HOSTS="$1"
  echo "$HOSTS" | sed -r 's/[[:blank:]]+/\n/g' | sort -u
}

function get_hosts_from_cert {
  typeset CERT=$1

 openssl x509 -in $CERT -text  |
 sed -e '/X509v3 Subject Alternative Name/,/DNS/!d;/X509v3 Subject/d;s/DNS:\([^, \n]*\)/\1/g;s/[[:blank:]]//g;s/,/ /g'
}

function check_update_required {
  typeset EMAIL="$1"
  typeset HOSTS="$2"

  typeset -i UPDATE_REQUIRED=0

  set $HOSTS

  MAIN_HOST=$1
  CERTIFICATE=$LEROOT/$MAIN_HOST/cert.pem

  if [[ ! -d $LEROOT/$MAIN_HOST || ! -f $CERTIFICATE ]]
  then
    echo "Update required - certificate missing"
    UPDATE_REQUIRED=1
  else
    check_same_hosts "$CERTIFICATE" "$HOSTS"
    UPDATE_REQUIRED=$?

    if ((UPDATE_REQUIRED==0))
    then
      check_expiring_soon $CERTIFICATE
      UPDATE_REQUIRED=$?
      if ((UPDATE_REQUIRED==1))
      then
        echo "Update required - certificate expiring soon ($EXPIRY_DATE)"
      else
        echo "$MAIN_HOST - up to date"
      fi
    else
      DIFFERENCE=$(diff <(echo "$SORTED_HOSTS") <(echo "$SORTED_CERT_HOSTS") | egrep "^[<>]" )
      echo "Update required - hosts differ $DIFFERENCE"
    fi
  fi

  return $UPDATE_REQUIRED
}

function process {
  typeset EMAIL="$1"
  typeset HOSTS=$2

  if ! check_update_required "$EMAIL" "$HOSTS"
  then
    generate "$EMAIL" "$HOSTS"
  fi
  
}

function read_conf {

  while read LINE
  do
    [[ -z "$LINE" ]] && continue
    [[ "$LINE" = \#* ]] && continue
    set $LINE
    case "$1" in
      "EMAIL") 
        [[ ! -z "$HOSTS" ]] && process "$EMAIL" "$HOSTS"
        HOSTS=""
        EMAIL=$2 ;;
      "HOSTS") 
        [[ ! -z "$HOSTS" ]] && process "$EMAIL" "$HOSTS"
        shift
         HOSTS="$*" ;;
      *) HOSTS="$HOSTS $*" ;;
    esac
  done < $CONF_FILE

  process "$EMAIL" "$HOSTS"
}

echo "Entering $LEDIR"
cd $LEDIR || die "Could not change directory into $DIR" 

echo "Updating from git"
git pull || die "Git pull returned unexpectedly"

read_conf

exit