#!/bin/bash
# Wrapper around /opt/bin/mirror to keep a log of the mirroring session, and email it.

# Configuration.
COMMAND="/opt/bin/mirror"
LOGSDIR="/var/log/duplication/mirroring/$(printf "%(%Y/%m)T")"
LOGFILE="$(printf "%(%Y%m%d-%H%M%S)T")-$$"
MIN_LOGFILE_SIZE="550"		# Used to prevent unnecessary emails - only messages over this size are sent.
# Where from/to to send emails.  Comment for no emailing.
EMAIL_FROM="\"Server: ${HOSTNAME%%.*}\" <noreply@slackware.uk.net>"
EMAIL_TO=("Systems' Administrator <sysadmin@slackware.uk>")

# Functions
notify() {
  [[ -n "$EMAIL_FROM" ]] && (( "${#EMAIL_TO[@]}" != 0 )) && {
    printf "%s: %s\\n%s: %s\\n%s:\\n%s\\n" "Exit code" "$ERR" "Logfile" "$LOGSDIR/$LOGFILE.xz" "Output" "$(<"$LOGSDIR/$LOGFILE")" | mail -r "$EMAIL_FROM" -s "Mirroring $1" "${EMAIL_TO[@]}" >/dev/null 2>&1 || {
      printf "%s: %s\\n" "${0##*/}" "mail command failed" >&2
      return 1
    }
  }

  return 0
}

# Only allow one copy of the script to run at any time.
# shellcheck disable=SC2154
if [[ "$FLOCK" != "$0" ]]; then
  # shellcheck disable=SC2093
  exec env FLOCK="$0" flock -E 10 -e -n "$0" "$0" "$@"
  ERR="$?"
  if (( ERR == 10 )); then
    # File is locked, exit now.
    exit 0
  elif (( ERR > 0 )); then
    printf "%s: %s\\n" "${0##*/}" "flock execution error" >&2
    exit 1
  fi
fi

# Logs are only for root.
umask 027

# Make sure the logs directory exists.
# shellcheck disable=SC2174
mkdir -p -m 750 "$LOGSDIR" 2>/dev/null || {
  printf "%s: %s\\n" "${0##*/}" "Failed to create logs directory '$LOGSDIR'" >&2
  exit 1
}

# Make sure the command to do the work is runnable.
[[ ! -x "$COMMAND" ]] && {
  printf "%s: %s\\n" "${0##*/}" "'$COMMAND' is not executable" >&2
  exit 1
}

# Do the mirroring work.
"$COMMAND" "$@" >"$LOGSDIR/$LOGFILE" 2>&1
ERR="$?"

# Tell the sysadmin what went on.
if (( "$ERR" == 0 )); then
  # Only email a mirroring report if it's not the hourly Slackware tree only run.
  # The size of the log file determines if it gets emailed.
  (( $(stat --printf="%s" "$LOGSDIR/$LOGFILE") > MIN_LOGFILE_SIZE )) && notify "report"
  ERR="$?"
else
  # Mirroring failed, tell the admin.
  notify "failure" || [[ -x /opt/bin/pushover-client ]] && /opt/bin/pushover-client "mirroring" -p -1 -s "Mirroring failure" -m "Check log in email"
  ERR="1"
fi

# Compress the log to save some space.
xz -9 "$LOGSDIR/$LOGFILE" 2>/dev/null || printf "%s: %s\\n" "${0##*/}" "failed to compress '$LOGSDIR/$LOGFILE'" >&2

exit "$ERR"