#!/usr/bin/env python

# (c) 2004 -- Benjamin Mako Hill <mako@bork.hampshire.edu>

# TODO:
# * check for an attachment overrides line as an alternative type of option

__copyright__ = "Copyright (c) 2004 Benjamin Mako Hill"
__author__ = "Benjamin Mako Hill <mako@debian.org>" 

import re

### Configuration Options
###########################################

# location of the sendmail binary
sendmail = "/usr/sbin/sendmail"

# list of mimetype which are, for the sake of this program, not
# attachments
ignored_types = ( "applica/pgp-signat", "application/pgp-signature" )

# list of regular expressions which we will view as being indicative
# of an attachment
attachment_regexes = [ r'\battach(ed|ment)?\b(?im)' ]


### No Need To Edit Below This Line
###########################################

import sys
import os
import email

## SUB: send message
def send_message(): 
    mailpipe = os.popen("%s -t" % sendmail, 'w')
    mailpipe.write( message_string )
    sys.exit( mailpipe.close() )

## SUB: print error message
def print_error():
    print >>sys.stderr, \
"""(Your message mentions attachments but does not include any.

Either:

 (1) Add an attachment or add \"CONFIRM\" (in ALLCAPS to beginning of
     the subject of the message and resend.  \"CONFIRM\" will be
     stripped from your message subject befor the message is sent.


 (2) Add a \"X-AttachCheck-Override: Yes\" header the message.

Read the documentation for AttachCheck for more details."""
    
# get the mail from stdin
message_string = sys.stdin.read()
message = email.message_from_string( message_string )

attachment_expected = False
attachment_seen = False
text_seen = False

for part in message.walk():

    # check to see if this part is a plain text entry
    if part.get_content_type() == "text/plain":

        # if this is the second text block, we should interrate
        # through things
        if text_seen:
            attachment_seen = True
        # otherwise, mark that we've now seen one text field
        else:
            text_seen = True

        # search for the word "attach" or "attached" or "attachment"
        # in the body of the message
        for regex in attachment_regexes:

            if re.search( regex, part.get_payload() ):
                attachment_expected = True

    # check to see if this mime-type is something we can ignore
    elif ( re.match( r'message/(?m)', part.get_content_type() ) or
           re.match( r'multipart/(?m)', part.get_content_type() ) or
           part.get_content_type() in ignored_types ):
        continue

    # if it's not text and it's an ignored type, it's a seen attachment
    else:
        attachment_seen = True

# now check to see if we are expecting an attachment
if attachment_expected:

    # if we are expecting an attachment and we've seen one, we should
    # send the file and be done with things
    if attachment_seen:
        send_message()

    # if we are expected have not seen it, we need to check to see if
    # the mail has been confirmed

    else:
        # check for the confirmation

        if re.search( r'Subject: CONFIRM', message_string ):
            message_string = re.sub( r'(Subject: )(CONFIRM )(.*?)\n',
                                     r'\1\3\n', message_string )
            send_message()

        elif message.get( 'X-AttachCheck-Override' ) == "Yes":
            send_message()
            
        else:
            print_error()
            sys.exit( 1 )


# if we are not expecting anything more, we should send the message
else:
    send_message()