#!/bin/sh
#
#  Read Mail Archiver
#
#  This utility is used to move, by means of ProcMail, "read mail" from user's
# inbox to his/her Mail folder (and subfolders).
#
#  Usually this is achieved directly via ProcMail but, as we want to keep some
# mail into inbox itself, we need a bit of additional scripting (also to avoid
# mail loss while handling the "read" one).
#
#  We use a "procmailrc" file put into the user's home (but made root-readable
# only, to avoid ProcMail complains): there one can put his filters to archive
# all the mail he wants, making the read of inbox much more speedy.
#
###
#
# The procedure:
#
#  1) we'll move the user's inbox into a temporary file, suddenly recreating the
# inbox to make sure new mail is not lost while we handle the archiving one.
#
#  2) then we launch ProcMail which filters the (stable/temp) inbox applying the
# user-defined filter set (~/procmailrc) and creates two files:
# $username.new: the unread mail to keep into inbox
# $username.other: the read "unmatched" mail to keep into inbox also
#
#  Other "mached" mails will be stored into user's Mail folder(s), depending to
# the rules written into his ~/procmailrc file.
#
#  3) after filtering we re-create the inbox appending:
#   a) the current inbox (usually /var/mail/$username)
#   b) the "new" (unread) file
#   c) the "other" (read but unmatched) file
#
#  4) last but not least we make a bit of housecleaning, removing all temporary
# files and setting the right permissions to the permanent ones.
#
# 20090307=LC

# to log results using syslog.
#LOGRESULTS="no"
LOGRESULTS="yes"

# if you want visual debug message fill the following var with something (like "true")
DEBUG=""

#-------------------------------------------------------------------------------
# a couple of useful debugging functions
#
debugmsg() {
    if [ "$DEBUG" != "" ]; then
        echo "DBG> $1"
    fi
}

debugenter() {
    if [ "$DEBUG" != "" ]; then
	echo -e "DBG> [enter] "
	read
    fi
}
#-------------------------------------------------------------------------------

# Check for input parameter: userid of the user which the inbox will be archived
if [ "$1" == "" ]; then
    echo "Usage: ${0##*/} <username>"
    exit 1
else
    USER=$1
    PROCMAILRC="/home/$USER/procmailrc"
    INBOX="/var/mail/$USER"
fi

# Check for utilities are present in the system
if [ ! -f $PROCMAILRC ]; then
    echo "Error: filter(s) file ($PROCMAILRC) not found!"
    exit 2
fi

if [ ! -f $INBOX ]; then
    echo "Error: INBOX file ($INBOX) not found!"
    exit 2
fi

if [ "$(type -p formail)" == "" ]; then
    echo "Error: 'formail' utility not found."
    exit 3
fi

if [ "$(type -p procmail)" == "" ]; then
    echo "Error: 'procmail' utility not found."
    exit 3
fi

# Check for optional utilities and get the mailcount before archiving (only if we want to log the results)
if [ "$LOGRESULTS" == "yes" ]; then
    if [ "$(type -p logger)" == "" ]; then
	echo "Warning: 'logger' utility not found: continuing without logging results"
	LOGRESULTS="no"
    fi
    if [ "$(type -p from)" == "" ]; then
	echo "Warning: 'from' utility not found: continuing without logging results"
	LOGRESULTS="no"
    fi
    if [ "$(type -p wc)" == "" ]; then
	echo "Warning: 'wc' utility not found: continuing without logging results"
	LOGRESULTS="no"
    fi
    if [ "$LOGRESULTS" == "yes" ]; then
	MAILPRE=$(from $1 | wc -l)
    fi
fi

#  1) Move the user's inbox into a temporary file, suddenly recreating the
# inbox to make sure new mail is not lost while we handle the archiving one.
debugmsg "1.1 move the user's inbox into a temporary file"
mv $INBOX $INBOX.tmp

debugmsg "1.2 re-create it empty"
touch $INBOX
debugmsg "1.3 make sure owner and perms are correct"
chown --reference=$INBOX.tmp $INBOX
chmod --reference=$INBOX.tmp $INBOX
debugenter

debugmsg "2.1 offline process the inbox file..."
formail -s procmail -m $PROCMAILRC < $INBOX.tmp

debugmsg "3.1 move any new mail (arrived while we was archiving) into $username.new2"
mv $INBOX $INBOX.new2

debugmsg "3.2 re-build INBOX file appending .new2, .new and .other files"
if [ -f $INBOX.new ]; then
    cat $INBOX.new > $INBOX
else
    touch $INBOX
fi
cat $INBOX.new2 >> $INBOX
if [ -f $INBOX.other ]; then
    cat $INBOX.other >> $INBOX
else
    debugmsg "Warning: no '.other' file ($INBOX.other) created (that may be strange), check!"
fi
debugenter

debugmsg "4.1 remove .new, .new2 and .other temporary files"
rm $INBOX.new*
if [ -f $INBOX.other ]; then
    rm $INBOX.other
fi
debugmsg "4.2 make sure owner and perms are correct"
chown --reference=$INBOX.tmp $INBOX
chmod --reference=$INBOX.tmp $INBOX

debugmsg "4.3 remove the (temporary) 'offline' inbox file (temporary disabled: check and do it by hand!)"

if [ "$DEBUG" == "" ]; then
    rm $INBOX.tmp
fi

# Get the mailcount after archiving (only if we want to log the results)
if [ "$LOGRESULTS" == "yes" ]; then
    MAILAFT=$(from $1 | wc -l)
    MAILARC=$(($MAILPRE - $MAILAFT))
    logger -t ${0##*/} "archiving process results: $MAILPRE initial, $MAILAFT current, $MAILARC archived"
fi