#!/bin/sh

##
# Wilfredo Sanchez <wsanchez@wsanchez.net>
# Andew Nesbitt <a.j.nesbitt@sms.ed.ac.uk>
#
# Performs backups on a backup server.
##

. "$(dirname "$0")/common.sh";

server_load_config;

# Determine client host name from inbound IP address.
client="$(                                                   \
  host "$(echo "${SSH_CLIENT}" | awk '{print $1}')"          \
  | sed 's|.*.in-addr.arpa domain name pointer \(.*\)\.|\1|' \
)";

# ${client} should be a host name, not empty.
if [ -z "${client}" ]; then
  error "ERROR: No backup client identified.";
  exit 1;
fi;

# Check that the client is registered.
registered="false";
for registered_client in $(list_clients); do
  if [ "${client}" == "${registered_client}" ]; then
    registered="true";
    break;
  fi;
done;

if ! "${registered}"; then
  error "Client is not registered for backup service: ${client}";
  exit 1;
fi;

##
# Start backup
##

    today="$(date +%A)";         # eg. Wednesday
yesterday="$(date -v-1d +%A)";   # eg. Tuesday
     date="$(date "+%Y.%m.%d")"; # eg. 2007.10.10

          lockfile="$(client_backup_lock_file "${client}")";
           pidfile="$(client_backup_pid_file  "${client}")";
client_backup_root="$(client_backup_root      "${client}")";

yesterday_backup_dir="${client_backup_root}/${yesterday}";
    today_backup_dir="${client_backup_root}/${today}";
  weekly_backup_file="${client_backup_root}/Weekly-${date}.tgz";

while lockfile -r 1 -! "${lockfile}" 2>/dev/null; do
  pid="$(cat "${pidfile}" 2>/dev/null)";
  if [ -n "${pid}" ]; then
    if ! kill -0 "${pid}" >/dev/null 2>&1; then
      error "Removing stale lock for PID: ${pid}";
      rm -f "${lockfile}" "${pidfile}";
    else
      error "Backup is already running (PID=$(cat "${pidfile}")) for client ${client}.";
      exit 1;
    fi;
  fi;
done;

echo "$$" > "${pidfile}";

backup_log_file="$(client_backup_log_file "${client}")";

log_start="$(date) - Starting daily back up for ${today}";

echo "${log_start}" >> "${backup_log_file}";

#
# Note: rsync server output goes to the client channel; don't try to
# redirect it to the log file, etc.
#
sudo rsync                              \
  --server                              \
  --archive                             \
    --extended-attributes               \
  --delete                              \
    --delete-excluded                   \
    --delete-after                      \
    --force                             \
    --ignore-errors                     \
  --link-dest="${yesterday_backup_dir}" \
  . "${today_backup_dir}/";

exec >> "${backup_log_file}" 2>&1;

echo "$(date) - Completed daily back up for ${today}";

if [ "${today}" == "Sunday" ]; then
  sudo tar --create --gzip --directory "${today_backup_dir}" --file "${weekly_backup_file}" .;
  echo "$(date) - Weekly back up for ${date}";
fi;

if [ -n "${backup_email_to}" ]; then
  grep -A 1000 "${log_start}" "${backup_log_file}"                   \
    | printf "From: %s\nReply-To: %s\nSubject: %s\n\n%s"             \
        "\"Backup Subsystem on $(hostname)\" <${backup_email_from}>" \
        "${backup_email_reply_to}"                                   \
        "${client} backup report for ${today}"                       \
        "$(cat -)"                                                   \
    | sendmail "${backup_email_to}";
fi;

rm -f "${backup_log_file}" "${pidfile}";