# This is a Courier maildroprc, hand-rolled by <ben@zygoat.ca> 02 Sep 2003.
#
# The objective here is to provide a reasonably simple way to inject
# spam-filtering into the mail delivery in such a way that it is easily
# changeable on a per-user basis, especially when users are configured
# in a mysql table.
#
# How to specify a delivery instruction that invokes maildrop assuming
# this is installed as /etc/courier/maildroprc:
#
# |maildrop -d user hamdelivery spamdelivery
#
# where 'user' is the actual (physical system) username that corresponds
# with this mail, irrespective of whether it is a virtual mailbox or not.
# (It seems mandatory to specify that, in order to be able to pass other
# arguments on the cmdline.  We determine the "actual" recipient from an
# environment variable.)
#
# The other two args are each a whitespace-delimited list of delivery
# instructions (wholly enclosed in quotes if there are several in the arg):
#  - components beginning with | are piped to the given command;
#  - components containing @ are delivered to the given email address;
#  - otherwise construed as path to a maildir/mailbox.
#
# The message is delivered to the first (hamdelivery) if it is deemed
# non-spam, or else to the second (spamdelivery) if it smells like spam.

# Either may be null, in which case the default delivery instruction
# (typically ./Maildir) is used).


# Import some useful stuff from the environment
import USER
import RECIPIENT

# The following is just for temporary diagnostics
#xfilter "/usr/local/courier/bin/reformail -A'X-Test: user $USER recip $RECIPIENT and log $LOGNAME'"

# Run the message through the spam filter
exception {
	xfilter "/usr/local/bin/spamc -u $USER -t 15"
	}

# Choose list of delivery instructions depending on spammyness
if (/^X-Spam-Status: *Yes/:h)
	{
	# It's spam; was a spam delivery box specified in second arg?
	if ("x$2" eq "x")
		DELIVERLIST = $1	# No, so deliver same as non-spam.
	else
		DELIVERLIST = $2	# Yup, so deliver where specified.
	}
else
	DELIVERLIST = $1	# Not spammy, so deliver as in first arg.

# See if delivery instructions are null in which case deliver to default
if ("x$DELIVERLIST" eq "x")
	to $DEFAULT
# (that will have effect of ending execution, if true)

# Parse out the list of delivery instructions.
A = " $DELIVERLIST"
while ($A =~ /.*![:space:]+!.+$/)
	{
	REST = $MATCH
	D = $MATCH3
	if ($D =~ /^\|!.*/)
		{
		echo "Piping to $MATCH2"
		cc "|$MATCH2"	# pipe to command
		}
	else
	if ($D =~ /@/)
		{
		echo "Forwarding to $D"
		cc "!$D"	# forward to email address
		}
	else
		{
		echo "Delivering into $D"
		cc $D		# write to maildir/box
		}

	A = $REST
	}

# Deliberately exit so as to suppress fall-through to default delivery
exit

# the end.