# Copyright (C) 2002 by James Henstridge <james@daa.com.au>
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software 
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, US

"""Perform spam detection with SpamAssassin.

Messages are passed to a spamd (SpamAssassin) daemon for spam checking.
Depending on the score returned, messages may be rejected or held for
moderation.
"""

import string
import re
import socket
import HandlerAPI
from Mailman import mm_cfg
from Mailman import Utils
from Mailman.Logging.Syslog import syslog
from Hold import hold_for_approval

SPAMD_PORT = 0
try:
    SPAMD_HOST = mm_cfg.SPAMASSASSIN_HOST
    i = string.find(SPAMD_HOST, ':')
    if i >= 0:
        SPAMD_HOST, SPAMD_PORT = SPAMD_HOST[:i], host[i+1:]
        try: SPAMD_PORT = int(SPAMD_PORT)
        except: SPAMD_PORT = None
except:
    SPAMD_HOST = 'localhost'
if not SPAMD_PORT: SPAMD_PORT = 783

try:    DISCARD_SCORE = mm_cfg.SPAMASSASSIN_DISCARD_SCORE
except: DISCARD_SCORE = 10
try:    HOLD_SCORE = mm_cfg.SPAMASSASSIN_HOLD_SCORE
except: HOLD_SCORE = 5

try:    MEMBER_BONUS = mm_cfg.SPAMASSASSIN_MEMBER_BONUS
except: MEMBER_BONUS = 2

# spamc protocol version
PROTOCOL_VERSION = "SPAMC/1.2"

class SpamAssassinDiscard(HandlerAPI.DiscardMessage):
    "The message was matched as spam."

class SpamAssassinHold(HandlerAPI.MessageHeld):
    "SpamAssassin thinks there may be spam in this message."

    def __init__(self, score=-1, symbols=''):
        HandlerAPI.MessageHeld.__init__(self)
        self.score = score
        self.symbols = string.replace(symbols, ',', ', ')
        
    def rejection_notice(self, mlist):
        return 'Message was held for approval because SpamAssassin gave ' \
               'the message a score of %g for the following reasons:\n\n%s' % \
                    (self.score, self.symbols)

response_pat = re.compile(r'^SPAMD/([\d.]+)\s+(-?\d+)\s+(.*)')
check_pat = re.compile(r'^Spam:\s*(True|False)\s*;\s*(-?[\d.]+)\s*/\s*(-?[\d.]+)')

def check_message(message):
    score = -1
    symbols = ''
    try:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.connect((SPAMD_HOST, SPAMD_PORT))

        header = 'SYMBOLS %s\r\nUser: mailman\r\nContent-length: %s\r\n\r\n' % \
                 (PROTOCOL_VERSION, len(message))
        
        sock.send(header)
        sock.send(message)
        sock.shutdown(1)

        fd = sock.makefile('r')

        line = fd.readline()
        match = response_pat.match(line)
        if not match: return -1, ''
        if match.group(2) != '0':
            syslog('error', 'non zero error code from spamd: %s'
                   % match.group(3))
            return -1, ''

        line = fd.readline()
	while line and line != '\r\n':
            match = check_pat.match(line)
            if match: score = float(match.group(2))
            line = fd.readline()

        # read in the spam report
        symbols = fd.read()
        symbols = string.replace(symbols, '\r\n', '\n')

    except socket.error:
        pass
    except IOError:
        pass
    return score, symbols

def process(mlist, msg, msgdata):
    if msgdata.get('approved'):
        return
    
    score, symbols = check_message(str(msg))

    # optionally give list members a bonus to reduce their chance of
    # getting held/discarded
    if MEMBER_BONUS != 0:
        sender = msg.GetSender()
        posters = Utils.List2Dict(map(string.lower, mlist.posters))
        if mlist.IsMember(sender) or \
           Utils.FindMatchingAddresses(sender, posters):
            score = score - MEMBER_BONUS

    if score > DISCARD_SCORE:
        listname = mlist.real_name
        sender = msg.GetSender()
        syslog('vette', '%s post from %s discarded: '
                        'SpamAssassin score was %s (discard threshold is %s)'
                          % (listname, sender, score, DISCARD_SCORE))
        raise SpamAssassinDiscard
    elif score > HOLD_SCORE:
        hold_for_approval(mlist, msg, msgdata, SpamAssassinHold(score,symbols))