#! /bin/bash
# TODO: Adapt for compatibility with LDAP
# Only the cert renewal change detection may be relevant for LDAP?

# shellcheck source=./helper-functions.sh
. /usr/local/bin/helper-functions.sh

function _log_date
{
  date +"%Y-%m-%d %H:%M:%S"
}

LOG_DATE=$(_log_date)
_notify 'task' "${LOG_DATE} Start check-for-changes script."

# ? --------------------------------------------- Checks

cd /tmp/docker-mailserver || exit 1

# check postfix-accounts.cf exist else break
if [[ ! -f postfix-accounts.cf ]]
then
  _notify 'inf' "${LOG_DATE} postfix-accounts.cf is missing! This should not run! Exit!"
  exit 0
fi

# verify checksum file exists; must be prepared by start-mailserver.sh
if [[ ! -f ${CHKSUM_FILE} ]]
then
  _notify 'err' "${LOG_DATE} ${CHKSUM_FILE} is missing! Start script failed? Exit!"
  exit 0
fi

# ? --------------------------------------------- Actual script begins

# determine postmaster address, duplicated from start-mailserver.sh
# this script previously didn't work when POSTMASTER_ADDRESS was empty
_obtain_hostname_and_domainname

PM_ADDRESS="${POSTMASTER_ADDRESS:=postmaster@${DOMAINNAME}}"
_notify 'inf' "${LOG_DATE} Using postmaster address ${PM_ADDRESS}"

# Change detection delayed during startup to avoid conflicting writes
sleep 10

_notify 'inf' "$(_log_date) check-for-changes is ready"

while true
do
  # get chksum and check it, no need to lock config yet
  _monitored_files_checksums >"${CHKSUM_FILE}.new"
  cmp --silent -- "${CHKSUM_FILE}" "${CHKSUM_FILE}.new"

  # cmp return codes
  # 0 – files are identical
  # 1 – files differ
  # 2 – inaccessible or missing argument
  if [[ ${?} -eq 1 ]]
  then
    _notify 'inf' "$(_log_date) Change detected"
    create_lock # Shared config safety lock
    CHANGED=$(grep -Fxvf "${CHKSUM_FILE}" "${CHKSUM_FILE}.new" | sed 's/^[^ ]\+  //')

    # TODO Perform updates below conditionally too
    # Also note that changes are performed in place and are not atomic
    # We should fix that and write to temporary files, stop, swap and start

    # `acme.json` is only relevant to Traefik, and is where it stores the certificates it manages.
    # When a change is detected it's assumed to be a possible cert renewal that needs to be
    # extracted for `docker-mailserver` services to adjust to.
    if [[ ${CHANGED} =~ /etc/letsencrypt/acme.json ]]
    then
      _notify 'inf' "'/etc/letsencrypt/acme.json' has changed, extracting certs.."

      # This breaks early as we only need the first successful extraction.
      # For more details see the `SSL_TYPE=letsencrypt` case handling in `setup-stack.sh`.
      #
      # NOTE: HOSTNAME is set via `helper-functions.sh`, it is not the original system HOSTNAME ENV anymore.
      # TODO: SSL_DOMAIN is Traefik specific, it no longer seems relevant and should be considered for removal.
      FQDN_LIST=("${SSL_DOMAIN}" "${HOSTNAME}" "${DOMAINNAME}")
      for CERT_DOMAIN in "${FQDN_LIST[@]}"
      do
        _notify 'inf' "Attempting to extract for '${CERT_DOMAIN}'"

        if _extract_certs_from_acme "${CERT_DOMAIN}"
        then
          # Prevent an unnecessary change detection from the newly extracted cert files by updating their hashes in advance:
          CERT_DOMAIN=$(_strip_wildcard_prefix "${CERT_DOMAIN}")
          ACME_CERT_DIR="/etc/letsencrypt/live/${CERT_DOMAIN}"

          sed -i "\|${ACME_CERT_DIR}|d" "${CHKSUM_FILE}.new"
          sha512sum "${ACME_CERT_DIR}"/*.pem >> "${CHKSUM_FILE}.new"

          break
        fi
      done
    fi

    # If monitored certificate files in /etc/letsencrypt/live have changed and no `acme.json` is in use,
    # They presently have no special handling other than to trigger a change that will restart Postfix/Dovecot.
    # TODO: That should be all that's required, unless the cert file paths have also changed (Postfix/Dovecot configs then need to be updated).

    # regenerate postfix accounts
    [[ ${SMTP_ONLY} -ne 1 ]] && _create_accounts

    _rebuild_relayhost

    # regenerate postix aliases
    _create_aliases

    # regenerate /etc/postfix/vhost
    # NOTE: If later adding support for LDAP with change detection and this method is called,
    # be sure to mimic `setup-stack.sh:_setup_ldap` which appends to `/tmp/vhost.tmp`.
    _create_postfix_vhost

    if find /var/mail -maxdepth 3 -a \( \! -user 5000 -o \! -group 5000 \) | read -r
    then
      chown -R 5000:5000 /var/mail
    fi

    _notify 'inf' "Restarting services due to detected changes.."

    supervisorctl restart postfix

    # prevent restart of dovecot when smtp_only=1
    [[ ${SMTP_ONLY} -ne 1 ]] && supervisorctl restart dovecot

    remove_lock
    _notify 'inf' "$(_log_date) Completed handling of detected change"
  fi

  # mark changes as applied
  mv "${CHKSUM_FILE}.new" "${CHKSUM_FILE}"

  sleep 2
done

exit 0