# -*- mode: sh; sh-basic-offset: 3; indent-tabs-mode: nil; -*-
# vim: set filetype=sh sw=3 sts=3 expandtab autoindent:

###############################################################
#
#  This handler uses dovecot (version 2 or later) dsync backup
#  to backup mail to a remote server.
#
#  Source and destination directories are typically configured
#  via the dovecot configuration, but can be overridden using
#  the settings here.
#
#  if the configuration is setup to have keepdaily at 3,
#  keepweekly is 2, and keepmonthly is 1, then each user's
#  maildir backup snapshot directory will contain these files:
#    daily.1
#    daily.2
#    daily.3
#    weekly.1
#    weekly.2
#    monthly.1
#
#  The basic algorithm is to dsync each user individually,
#  and to use hard links for retaining historical data.
#
#  For the backup rotation to work, destuser must be able to run
#  arbitrary bash commands on the desthost.
#
#  If 'remove' is set to 'yes' (default), then any mail directory 
#  which is deleted from the source will be moved to a "deleted"
#  directory in the destination. It is up to you to periodically 
#  remove this directory or old maildirs in it.
#
#  Limitations:
#    . because we are not dynamically looking up anything with
#      dovecot's userdb, we expect all data to be under the same 
#      tree on both the source and destination
#    
#    . we are assuming a backup to a backup server, so the 
#      destination host should have its dovecot mail_location 
#      configured to put the mail into
#      $stripped_destdir/$letter/$user/$current_backup
#
##############################################################

getconf rotate yes
getconf remove yes
getconf backup yes

getconf keepdaily 5
getconf keepweekly 3
getconf keepmonthly 1

getconf srcconffile
getconf destconffile
getconf srcdir 
getconf destdir
getconf current_backup current_backup
getconf desthost
getconf destport 22
getconf destuser
getconf destid_file /root/.ssh/id_rsa
getconf sshoptions

failedcount=0

# strip leading mailbox specifier (eg. mdbox:; maildir:, etc)
stripped_destdir=${destdir/*:/}
stripped_srcdir=${srcdir/*:/}

# strip trailing /
destdir=${destdir%/}
srcdir=${srcdir%/}

if [ ! -n $destdir ]; then
   destdir='-o mail_location=$destdir'
fi
if [ ! -n $srcdir ]; then
   srcdir='-o mail_location=$srcdir'
fi

if [ ! -n $srcconffile ]; then
   srcconffile='-c $srcconffile'
fi

if [ ! -n $destconffile ]; then
   destconffile='-c $destconffile'
fi

[ -d $stripped_srcdir ] || fatal "source directory $srcdir doesn't exist"


##################################################################
### FUNCTIONS

function do_user() {
   local user=$1
   local btype=$2
   local letter=${user:0:1} 
   local target="$stripped_destdir/$letter/$user/$current_backup"

   debug "syncing"
   while [ $failedcount -lt 4 ]; do
      debug $DSYNC $testflags -u $user backup $srcconffile $srcdir \
         ssh -i $destid_file $destuser@$desthost $DSYNC $destconffile \
         -u $user $destdir 2>&1
      ret=`$DSYNC $testflags -u $user backup $srcconffile $srcdir \
         ssh -i $destid_file $destuser@$desthost $DSYNC $destconffile \
         -u $user $destdir 2>&1`
      ret=$?
      if [ $ret == 2 ]; then
         # dsync needs to be run again
         let "failedcount = failedcount + 1"
      elif [ $ret == 0 ]; then
         # things worked, so we break out of the loop
         let "failedcount = 4"
         # move the directory to the $btype.1 and make a 'created' file
         ssh -o PasswordAuthentication=no $desthost -l $destuser -i $destid_file $sshoptions "mv $target ../$btype.1"
         ssh -o PasswordAuthentication=no $desthost -l $destuser -i $destid_file $sshoptions "date +%c%n%s > ../$btype.1/created"
      elif [ $ret != 0 ]; then
         # things did not work in a good way, report it and try again
         warning "dsync $user failed"
         warning "  returned: $ret"
         let "failedcount = failedcount + 1"
      fi

      if [ $failedcount -gt 4 ]; then
         fatal "dsync failed 3 times for this user -- something is not working right. bailing out."
      fi
   done
}

# remove any maildirs from backup which might have been deleted
# and add new ones which have just been created.
# (actually, it just moved them to the directory "deleted")

function do_remove() {
   local tmp1=`maketemp dsync-tmp-file`
   local tmp2=`maketemp dsync-tmp-file`

   ssh -p $destport -i $destid_file $sshoptions $destuser@$desthost mkdir -p "${stripped_destdir}/deleted"
      cd "$stripped_srcdir"
      for userdir in `ls -d1 */`; do
         ls -1 "$stripped_srcdir/$userdir" | sort > $tmp1
         ssh -p $destport -i $destid_file $sshoptions $destuser@$desthost ls -1 "$stripped_destdir/$userdir" | sort > $tmp2
      for deluser in `join -v 2 $tmp1 $tmp2`; do
         [ "$deluser" != "" ] || continue
         info "removing $destuser@$desthost:$stripped_destdir/$userdir$deluser/"
         ssh -p $destport -i $destid_file $sshoptions $destuser@$desthost mv "$stripped_destdir/$userdir$deluser/" "$stripped_destdir/deleted"
         ssh -p $destport -i $destid_file $sshoptions $destuser@$desthost "date +%c%n%s > '$stripped_destdir/deleted/$deluser/deleted_on'"
      done
   done
   rm $tmp1
   rm $tmp2
}

function do_rotate() {
   [ "$rotate" == "yes" ] || return;
   local user=$1
   local letter=${user:0:1}
   local backuproot="$stripped_destdir/$letter/$user"
   local target="$stripped_destdir/$letter/$user/$current_backup"
(
   ssh -T -o PasswordAuthentication=no $desthost -l $destuser -i $destid_file $sshoptions <<EOF
##### BEGIN REMOTE SCRIPT #####
   seconds_daily=86400
   seconds_weekly=604800
   seconds_monthly=2628000
   keepdaily=$keepdaily
   keepweekly=$keepweekly
   keepmonthly=$keepmonthly
   now=\`date +%s\`

   if [ ! -d "$backuproot" ]; then
      echo "Debug: skipping rotate of $user. $backuproot doesn't exist."
      exit
   fi
   for rottype in daily weekly monthly; do
      seconds=\$((seconds_\${rottype}))

      dir="$backuproot/\$rottype"
      if [ ! -d \$dir.1 ]; then
         echo "Debug: \$dir.1 does not exist, skipping."
         continue 1
      fi

      if [ -f \$target ]; then
         echo "Warning: \$target exists. Previous backup did not complete properly. Skipping rotation."
         continue 1
      fi

      # Rotate the current list of backups, if we can.
      oldest=\`find $backuproot -maxdepth 1 -type d -name \$rottype'.*' | @SED@ 's/^.*\.//' | sort -n | tail -1\`
      #echo "Debug: oldest \$oldest"
      [ "\$oldest" == "" ] && oldest=0
      for (( i=\$oldest; i > 0; i-- )); do
         if [ -d \$dir.\$i ]; then
            if [ -f \$dir.\$i/created ]; then
               created=\`tail -1 \$dir.\$i/created\`
            else
               created=0
            fi
            cutoff_time=\$(( now - (seconds*(i-1)) ))
            if [ ! \$created -gt \$cutoff_time ]; then
               next=\$(( i + 1 ))
               if [ ! -d \$dir.\$next ]; then
                  echo "Debug: \$rottype.\$i --> \$rottype.\$next"
                  mv \$dir.\$i \$dir.\$next
                  date +%c%n%s > \$dir.\$next/rotated
               else
                  echo "Debug: skipping rotation of \$dir.\$i because \$dir.\$next already exists."
               fi
            else
               echo "Debug: skipping rotation of \$dir.\$i because it was created" \$(( (now-created)/86400)) "days ago ("\$(( (now-cutoff_time)/86400))" needed)."
            fi
         fi
      done
   done

   max=\$((keepdaily+1))
   if [ \( \$keepweekly -gt 0 -a -d $backuproot/daily.\$max \) -a ! -d $backuproot/weekly.1 ]; then
      echo "Debug: daily.\$max --> weekly.1"
      mv $backuproot/daily.\$max $backuproot/weekly.1
      date +%c%n%s > $backuproot/weekly.1/rotated
   fi

   max=\$((keepweekly+1))
   if [ \( \$keepmonthly -gt 0 -a -d $backuproot/weekly.\$max \) -a ! -d $backuproot/monthly.1 ]; then
      echo "Debug: weekly.\$max --> monthly.1"
      mv $backuproot/weekly.\$max $backuproot/monthly.1
      date +%c%n%s > $backuproot/monthly.1/rotated
   fi

   for rottype in daily weekly monthly; do
      max=\$((keep\${rottype}+1))
      dir="$backuproot/\$rottype"
      oldest=\`find $backuproot -maxdepth 1 -type d -name \$rottype'.*' | @SED@ 's/^.*\.//' | sort -n | tail -1\`
      [ "\$oldest" == "" ] && oldest=0
      # if we've rotated the last backup off the stack, remove it.
      for (( i=\$oldest; i >= \$max; i-- )); do
         if [ -d \$dir.\$i ]; then
            if [ -d $backuproot/rotate.tmp ]; then
               echo "Debug: removing rotate.tmp"
               rm -rf $backuproot/rotate.tmp
            fi
            echo "Debug: moving \$rottype.\$i to rotate.tmp"
            mv \$dir.\$i $backuproot/rotate.tmp
         fi
      done
   done
####### END REMOTE SCRIPT #######
EOF
) | (while read a; do passthru $a; done)

}


function setup_remote_dirs() {
   local user=$1
   local backuptype=$2
   local letter=${user:0:1}
   local dir="$stripped_destdir/$letter/$user/$backuptype"
   local tmpdir="$stripped_destdir/$letter/$user/rotate.tmp"
(
   ssh -T -o PasswordAuthentication=no $desthost -l $destuser -i $destid_file $sshoptions <<EOF
      if [ ! -d $stripped_destdir ]; then
         echo "Fatal: Destination directory $stripped_destdir does not exist on host $desthost."
         exit 1
      elif [ -d $dir.1 ]; then
         if [ -f $dir.1/created ]; then
            echo "Warning: $dir.1 already exists. Overwriting contents."
         else
            echo "Warning: we seem to be resuming a partially written $dir.1"
         fi
      else
         if [ -d $tmpdir ]; then
            mv $tmpdir $dir.1
            if [ \$? == 1 ]; then
               echo "Fatal: could mv $stripped_destdir/rotate.tmp $dir.1 on host $desthost"
               exit 1
            fi
         else
            mkdir --parents $dir.1
            if [ \$? == 1 ]; then
               echo "Fatal: could not create directory $dir.1 on host $desthost"
               exit 1
            fi
         fi
         if [ -d $dir.2 ]; then
            echo "Debug: update links $backuptype.2 --> $backuptype.1"
            cp -alf $dir.2/. $dir.1
            #if [ \$? == 1 ]; then
            #   echo "Fatal: could not create hard links to $dir.1 on host $desthost"
            #   exit 1
            #fi
         fi
      fi
      [ -f $dir.1/created ] && rm $dir.1/created
      [ -f $dir.1/rotated ] && rm $dir.1/rotated
      exit 0
EOF
) | (while read a; do passthru $a; done)

   if [ $? == 1 ]; then exit; fi
}

###
##################################################################

# see if we can login
debug "ssh -o PasswordAuthentication=no $desthost -l $destuser -i $destid_file $sshoptions 'echo -n 1'"
if [ ! $test ]; then
   result=`ssh -o PasswordAuthentication=no $desthost -l $destuser -i $destid_file $sshoptions 'echo -n 1' 2>&1`
   if [ "$result" != "1" ]; then
      fatal "Can't connect to $desthost as $destuser using $destid_file."
   fi
fi

## SANITY CHECKS ##
status=`ssh -p $destport -i $destid_file $sshoptions $destuser@$desthost "[ -d \"$stripped_destdir\" ] && echo 'ok'"`
if [ "$status" != "ok" ]; then
   fatal "Destination directory $stripped_destdir doesn't exist!"
   exit
fi

### REMOVE OLD MAILDIRS ###

if [ "$remove" == "yes" ]; then
   do_remove
fi

### MAKE BACKUPS ###

if [ "$backup" == "yes" ]; then
   if [ $keepdaily -gt 0 ]; then btype=daily
   elif [ $keepweekly -gt 0 ]; then btype=weekly
   elif [ $keepmonthly -gt 0 ]; then btype=monthly
   else fatal "keeping no backups"; fi

   if [ "$testuser" != "" ]; then
      cd "$stripped_srcdir/${user:0:1}"
      do_rotate $testuser
      setup_remote_dirs $testuser $btype
      do_user $testuser $btype
   else
      [ -d "$stripped_srcdir" ] || fatal "directory $stripped_srcdir not found."
      for user in `$DOVEADM user \* | cut -d@ -f1`
      do
         debug $user
         [ "$user" != "" ] || continue
         do_rotate $user
         setup_remote_dirs $user $btype
         do_user $user $btype
      done
   fi
fi