#!/bin/bash
#
# Redeliver any messages that may have accidentally been sent to
# /var/mail/$USER, due to temporary AFS glitches.
#
# This should be called as root on deleuze.
#
# USAGE: redeliver-mail [USER]
#
# If USER is specified, redeliver their mail, regardless of whether
# mail redelivery is stopped for all users.

BLOCKFILE=/tmp/exim4/inhibit-redelivery

# Function to deliver mail for $USER.  If the message still can't be
# written to $USER/Maildir, Exim will place it in /var/mail/$USER
# again.
function deliver_mail() {
    local USER=$1
    local TMPMBOX=$2

    mv /var/mail/$USER $TMPMBOX
    formail -s /etc/exim4/deliver-once $USER < $TMPMBOX
    rm -f $TMPMBOX
}

# Check arguments.
if [ -n "$2" ]; then
    echo "Incorrect number of arguments"
    exit 1
elif [ -n "$1" ]; then
    # Do redelivery for just one person
    USER=$1
    MBOX=/var/mail/$USER
    TMPMBOX=/tmp/exim4/$USER.mbox.tmp

    if test -f $TMPMBOX; then
        echo "The temporary file $TMPMBOX still exists."
        echo "Please wait an hour for it to go away before running this" \
            "script again."
        exit 1
    fi

    if ! test -s $MBOX || ! test -f $MBOX; then
        echo "$MBOX is empty"
        exit 1
    fi

    deliver_mail $USER $TMPMBOX
    echo Done delivering mail for $USER
    exit 0
fi   

# Make sure we didn't get into trouble with an earlier run of this
# script.  A separate daily cron job should run to check for the
# existence of this file.
if test -f $BLOCKFILE; then
    exit 0
fi

# Run redelivery for everyone
for MBOX in /var/mail/*; do

    USER=$(basename $MBOX)
    TMPMBOX=/tmp/exim4/$USER.mbox.tmp

    # Sanity check: file exists and has nonzero size
    if ! test -s $MBOX; then
        continue
    fi

    # Sanity check: If TMPMBOX exists and is 20 minutes old or less,
    # there is some serious trouble, and we should (1) email
    # postmaster about it and (2) block future processing of /var/mail
    # until someone removes BLOCKFILE.
    #
    # If TMPMBOX exists and is older than 20 minutes, it's probably
    # stale, so blow it away.  Note that we will never get to this
    # point if BLOCKFILE exists, so there is no need to refine the
    # metric further.
    if test -f $TMPMBOX; then
        if test $(stat --format=%Y $TMPMBOX) -le \
            $(date --date='-20 min' +%s); then
            # Set block file
            touch $BLOCKFILE
            echo -e "/var/mail/$USER contains too much email." \
                "\nBlocking email redelivery script until this is resolved." \
                "\n\nTo indicate that this is resolved, do the following" \
                "\non deleuze." \
                "\n (1) Wait for $TMPMBOX to go away (should take an hour)" \
                "\n (2) Run '$0 $USER'" \
                "\n (3) Remove $BLOCKFILE" | \
              mail -s "[redeliver-mail] Mail backlog too large on deleuze" \
                -e -a "From: root@deleuze.hcoop.net" \
                postmaster@deleuze.hcoop.net
            exit 0
        else
            rm -fr $TMPMBOX
        fi
    fi

    # Deliver mail.  If the message still can't be written to
    # $USER/Maildir, Exim will place it in /var/mail/$USER again.
    deliver_mail $USER $TMPMBOX
done