spambayes 1.1b1-1 / usr / lib / python2.7 / dist-packages / spambayes / tokenizer.py

#! /usr/bin/env python
"""Module to tokenize email messages for spam filtering."""

from __future__ import generators

import email
import email.Message
import email.Header
import email.Utils
import email.Errors
import re
import math
import os
import binascii
import urlparse
import urllib

from spambayes import classifier
from spambayes.Options import options

from spambayes.mboxutils import get_message

try:
    from spambayes import dnscache
    cache = dnscache.cache(cachefile=options["Tokenizer", "lookup_ip_cache"])
    cache.printStatsAtEnd = False
except (IOError, ImportError):
    class cache:
        @staticmethod
        def lookup(*args):
            return []
else:
    import atexit
    atexit.register(cache.close)

 
# Patch encodings.aliases to recognize 'ansi_x3_4_1968'
from encodings.aliases import aliases # The aliases dictionary
if not aliases.has_key('ansi_x3_4_1968'):
    aliases['ansi_x3_4_1968'] = 'ascii'
del aliases # Not needed any more

##############################################################################
# To fold case or not to fold case?  I didn't want to fold case, because
# it hides information in English, and I have no idea what .lower() does
# to other languages; and, indeed, 'FREE' (all caps) turned out to be one
# of the strongest spam indicators in my content-only tests (== one with
# prob 0.99 *and* made it into spamprob's nbest list very often).
#
# Against preservering case, it makes the database size larger, and requires
# more training data to get enough "representative" mixed-case examples.
#
# Running my c.l.py tests didn't support my intuition that case was
# valuable, so it's getting folded away now.  Folding or not made no
# significant difference to the false positive rate, and folding made a
# small (but statistically significant all the same) reduction in the
# false negative rate.  There is one obvious difference:  after folding
# case, conference announcements no longer got high spam scores.  Their
# content was usually fine, but they were highly penalized for VISIT OUR
# WEBSITE FOR MORE INFORMATION! kinds of repeated SCREAMING.  That is
# indeed the language of advertising, and I halfway regret that folding
# away case no longer picks on them.
#
# Since the f-p rate didn't change, but conference announcements escaped
# that category, something else took their place.  It seems to be highly
# off-topic messages, like debates about Microsoft's place in the world.
# Talk about "money" and "lucrative" is indistinguishable now from talk
# about "MONEY" and "LUCRATIVE", and spam mentions MONEY a lot.


##############################################################################
# Character n-grams or words?
#
# With careful multiple-corpora c.l.py tests sticking to case-folded decoded
# text-only portions, and ignoring headers, and with identical special
# parsing & tagging of embedded URLs:
#
# Character 3-grams gave 5x as many false positives as split-on-whitespace
# (s-o-w).  The f-n rate was also significantly worse, but within a factor
# of 2.  So character 3-grams lost across the board.
#
# Character 5-grams gave 32% more f-ps than split-on-whitespace, but the
# s-o-w fp rate across 20,000 presumed-hams was 0.1%, and this is the
# difference between 23 and 34 f-ps.  There aren't enough there to say that's
# significnatly more with killer-high confidence.  There were plenty of f-ns,
# though, and the f-n rate with character 5-grams was substantially *worse*
# than with character 3-grams (which in turn was substantially worse than
# with s-o-w).
#
# Training on character 5-grams creates many more unique tokens than s-o-w:
# a typical run bloated to 150MB process size.  It also ran a lot slower than
# s-o-w, partly related to heavy indexing of a huge out-of-cache wordinfo
# dict.  I rarely noticed disk activity when running s-o-w, so rarely bothered
# to look at process size; it was under 30MB last time I looked.
#
# Figuring out *why* a msg scored as it did proved much more mysterious when
# working with character n-grams:  they often had no obvious "meaning".  In
# contrast, it was always easy to figure out what s-o-w was picking up on.
# 5-grams flagged a msg from Christian Tismer as spam, where he was discussing
# the speed of tasklets under his new implementation of stackless:
#
#     prob = 0.99999998959
#     prob('ed sw') = 0.01
#     prob('http0:pgp') = 0.01
#     prob('http0:python') = 0.01
#     prob('hlon ') = 0.99
#     prob('http0:wwwkeys') = 0.01
#     prob('http0:starship') = 0.01
#     prob('http0:stackless') = 0.01
#     prob('n xp ') = 0.99
#     prob('on xp') = 0.99
#     prob('p 150') = 0.99
#     prob('lon x') = 0.99
#     prob(' amd ') = 0.99
#     prob(' xp 1') = 0.99
#     prob(' athl') = 0.99
#     prob('1500+') = 0.99
#     prob('xp 15') = 0.99
#
# The spam decision was baffling until I realized that *all* the high-
# probablity spam 5-grams there came out of a single phrase:
#
#     AMD Athlon XP 1500+
#
# So Christian was punished for using a machine lots of spam tries to sell
# <wink>.  In a classic Bayesian classifier, this probably wouldn't have
# mattered, but Graham's throws away almost all the 5-grams from a msg,
# saving only the about-a-dozen farthest from a neutral 0.5.  So one bad
# phrase can kill you!  This appears to happen very rarely, but happened
# more than once.
#
# The conclusion is that character n-grams have almost nothing to recommend
# them under Graham's scheme:  harder to work with, slower, much larger
# database, worse results, and prone to rare mysterious disasters.
#
# There's one area they won hands-down:  detecting spam in what I assume are
# Asian languages.  The s-o-w scheme sometimes finds only line-ends to split
# on then, and then a "hey, this 'word' is way too big!  let's ignore it"
# gimmick kicks in, and produces no tokens at all.
#
# [Later:  we produce character 5-grams then under the s-o-w scheme, instead
# ignoring the blob, but only if there are high-bit characters in the blob;
# e.g., there's no point 5-gramming uuencoded lines, and doing so would
# bloat the database size.]
#
# Interesting:  despite that odd example above, the *kinds* of f-p mistakes
# 5-grams made were very much like s-o-w made -- I recognized almost all of
# the 5-gram f-p messages from previous s-o-w runs.  For example, both
# schemes have a particular hatred for conference announcements, although
# s-o-w stopped hating them after folding case.  But 5-grams still hate them.
# Both schemes also hate msgs discussing HTML with examples, with about equal
# passion.   Both schemes hate brief "please subscribe [unsubscribe] me"
# msgs, although 5-grams seems to hate them more.


##############################################################################
# How to tokenize?
#
# I started with string.split() merely for speed.  Over time I realized it
# was making interesting context distinctions qualitatively akin to n-gram
# schemes; e.g., "free!!" is a much stronger spam indicator than "free".  But
# unlike n-grams (whether word- or character- based) under Graham's scoring
# scheme, this mild context dependence never seems to go over the edge in
# giving "too much" credence to an unlucky phrase.
#
# OTOH, compared to "searching for words", it increases the size of the
# database substantially, less than but close to a factor of 2.  This is very
# much less than a word bigram scheme bloats it, but as always an increase
# isn't justified unless the results are better.
#
# Following are stats comparing
#
#    for token in text.split():  # left column
#
# to
#
#    for token in re.findall(r"[\w$\-\x80-\xff]+", text):  # right column
#
# text is case-normalized (text.lower()) in both cases, and the runs were
# identical in all other respects.  The results clearly favor the split()
# gimmick, although they vaguely suggest that some sort of compromise
# may do as well with less database burden; e.g., *perhaps* folding runs of
# "punctuation" characters into a canonical representative could do that.
# But the database size is reasonable without that, and plain split() avoids
# having to worry about how to "fold punctuation" in languages other than
# English.
#
#    false positive percentages
#        0.000  0.000  tied
#        0.000  0.050  lost
#        0.050  0.150  lost
#        0.000  0.025  lost
#        0.025  0.050  lost
#        0.025  0.075  lost
#        0.050  0.150  lost
#        0.025  0.000  won
#        0.025  0.075  lost
#        0.000  0.025  lost
#        0.075  0.150  lost
#        0.050  0.050  tied
#        0.025  0.050  lost
#        0.000  0.025  lost
#        0.050  0.025  won
#        0.025  0.000  won
#        0.025  0.025  tied
#        0.000  0.025  lost
#        0.025  0.075  lost
#        0.050  0.175  lost
#
#    won   3 times
#    tied  3 times
#    lost 14 times
#
#    total unique fp went from 8 to 20
#
#    false negative percentages
#        0.945  1.200  lost
#        0.836  1.018  lost
#        1.200  1.200  tied
#        1.418  1.636  lost
#        1.455  1.418  won
#        1.091  1.309  lost
#        1.091  1.272  lost
#        1.236  1.563  lost
#        1.564  1.855  lost
#        1.236  1.491  lost
#        1.563  1.599  lost
#        1.563  1.781  lost
#        1.236  1.709  lost
#        0.836  0.982  lost
#        0.873  1.382  lost
#        1.236  1.527  lost
#        1.273  1.418  lost
#        1.018  1.273  lost
#        1.091  1.091  tied
#        1.490  1.454  won
#
#    won   2 times
#    tied  2 times
#    lost 16 times
#
#    total unique fn went from 292 to 302
#
# Later:  Here's another tokenization scheme with more promise.
#
#     fold case, ignore punctuation, strip a trailing 's' from words (to
#     stop Guido griping about "hotel" and "hotels" getting scored as
#     distinct clues <wink>) and save both word bigrams and word unigrams
#
# This was the code:
#
#     # Tokenize everything in the body.
#     lastw = ''
#     for w in word_re.findall(text):
#         n = len(w)
#         # Make sure this range matches in tokenize_word().
#         if 3 <= n <= 12:
#             if w[-1] == 's':
#                 w = w[:-1]
#             yield w
#             if lastw:
#                 yield lastw + w
#             lastw = w + ' '
#
#         elif n >= 3:
#             lastw = ''
#             for t in tokenize_word(w):
#                 yield t
#
# where
#
#     word_re = re.compile(r"[\w$\-\x80-\xff]+")
#
# This at least doubled the process size.  It helped the f-n rate
# significantly, but probably hurt the f-p rate (the f-p rate is too low
# with only 4000 hams per run to be confident about changes of such small
# *absolute* magnitude -- 0.025% is a single message in the f-p table):
#
# false positive percentages
#     0.000  0.000  tied
#     0.000  0.075  lost  +(was 0)
#     0.050  0.125  lost  +150.00%
#     0.025  0.000  won   -100.00%
#     0.075  0.025  won    -66.67%
#     0.000  0.050  lost  +(was 0)
#     0.100  0.175  lost   +75.00%
#     0.050  0.050  tied
#     0.025  0.050  lost  +100.00%
#     0.025  0.000  won   -100.00%
#     0.050  0.125  lost  +150.00%
#     0.050  0.025  won    -50.00%
#     0.050  0.050  tied
#     0.000  0.025  lost  +(was 0)
#     0.000  0.025  lost  +(was 0)
#     0.075  0.050  won    -33.33%
#     0.025  0.050  lost  +100.00%
#     0.000  0.000  tied
#     0.025  0.100  lost  +300.00%
#     0.050  0.150  lost  +200.00%
#
# won   5 times
# tied  4 times
# lost 11 times
#
# total unique fp went from 13 to 21
#
# false negative percentages
#     0.327  0.218  won    -33.33%
#     0.400  0.218  won    -45.50%
#     0.327  0.218  won    -33.33%
#     0.691  0.691  tied
#     0.545  0.327  won    -40.00%
#     0.291  0.218  won    -25.09%
#     0.218  0.291  lost   +33.49%
#     0.654  0.473  won    -27.68%
#     0.364  0.327  won    -10.16%
#     0.291  0.182  won    -37.46%
#     0.327  0.254  won    -22.32%
#     0.691  0.509  won    -26.34%
#     0.582  0.473  won    -18.73%
#     0.291  0.255  won    -12.37%
#     0.364  0.218  won    -40.11%
#     0.436  0.327  won    -25.00%
#     0.436  0.473  lost    +8.49%
#     0.218  0.218  tied
#     0.291  0.255  won    -12.37%
#     0.254  0.364  lost   +43.31%
#
# won  15 times
# tied  2 times
# lost  3 times
#
# total unique fn went from 106 to 94

##############################################################################
# What about HTML?
#
# Computer geeks seem to view use of HTML in mailing lists and newsgroups as
# a mortal sin.  Normal people don't, but so it goes:  in a technical list/
# group, every HTML decoration has spamprob 0.99, there are lots of unique
# HTML decorations, and lots of them appear at the very start of the message
# so that Graham's scoring scheme latches on to them tight.  As a result,
# any plain text message just containing an HTML example is likely to be
# judged spam (every HTML decoration is an extreme).
#
# So if a message is multipart/alternative with both text/plain and text/html
# branches, we ignore the latter, else newbies would never get a message
# through.  If a message is just HTML, it has virtually no chance of getting
# through.
#
# In an effort to let normal people use mailing lists too <wink>, and to
# alleviate the woes of messages merely *discussing* HTML practice, I
# added a gimmick to strip HTML tags after case-normalization and after
# special tagging of embedded URLs.  This consisted of a regexp sub pattern,
# where instances got replaced by single blanks:
#
#    html_re = re.compile(r"""
#        <
#        [^\s<>]     # e.g., don't match 'a < b' or '<<<' or 'i << 5' or 'a<>b'
#        [^>]{0,128} # search for the end '>', but don't chew up the world
#        >
#    """, re.VERBOSE)
#
# and then
#
#    text = html_re.sub(' ', text)
#
# Alas, little good came of this:
#
#    false positive percentages
#        0.000  0.000  tied
#        0.000  0.000  tied
#        0.050  0.075  lost
#        0.000  0.000  tied
#        0.025  0.025  tied
#        0.025  0.025  tied
#        0.050  0.050  tied
#        0.025  0.025  tied
#        0.025  0.025  tied
#        0.000  0.050  lost
#        0.075  0.100  lost
#        0.050  0.050  tied
#        0.025  0.025  tied
#        0.000  0.025  lost
#        0.050  0.050  tied
#        0.025  0.025  tied
#        0.025  0.025  tied
#        0.000  0.000  tied
#        0.025  0.050  lost
#        0.050  0.050  tied
#
#    won   0 times
#    tied 15 times
#    lost  5 times
#
#    total unique fp went from 8 to 12
#
#    false negative percentages
#        0.945  1.164  lost
#        0.836  1.418  lost
#        1.200  1.272  lost
#        1.418  1.272  won
#        1.455  1.273  won
#        1.091  1.382  lost
#        1.091  1.309  lost
#        1.236  1.381  lost
#        1.564  1.745  lost
#        1.236  1.564  lost
#        1.563  1.781  lost
#        1.563  1.745  lost
#        1.236  1.455  lost
#        0.836  0.982  lost
#        0.873  1.309  lost
#        1.236  1.381  lost
#        1.273  1.273  tied
#        1.018  1.273  lost
#        1.091  1.200  lost
#        1.490  1.599  lost
#
#    won   2 times
#    tied  1 times
#    lost 17 times
#
#    total unique fn went from 292 to 327
#
# The messages merely discussing HTML were no longer fps, so it did what it
# intended there.  But the f-n rate nearly doubled on at least one run -- so
# strong a set of spam indicators is the mere presence of HTML.  The increase
# in the number of fps despite that the HTML-discussing msgs left that
# category remains mysterious to me, but it wasn't a significant increase
# so I let it drop.
#
# Later:  If I simply give up on making mailing lists friendly to my sisters
# (they're not nerds, and create wonderfully attractive HTML msgs), a
# compromise is to strip HTML tags from only text/plain msgs.  That's
# principled enough so far as it goes, and eliminates the HTML-discussing
# false positives.  It remains disturbing that the f-n rate on pure HTML
# msgs increases significantly when stripping tags, so the code here doesn't
# do that part.  However, even after stripping tags, the rates above show that
# at least 98% of spams are still correctly identified as spam.
#
# So, if another way is found to slash the f-n rate, the decision here not
# to strip HTML from HTML-only msgs should be revisited.
#
# Later, after the f-n rate got slashed via other means:
#
# false positive percentages
#     0.000  0.000  tied
#     0.000  0.000  tied
#     0.050  0.075  lost   +50.00%
#     0.025  0.025  tied
#     0.075  0.025  won    -66.67%
#     0.000  0.000  tied
#     0.100  0.100  tied
#     0.050  0.075  lost   +50.00%
#     0.025  0.025  tied
#     0.025  0.000  won   -100.00%
#     0.050  0.075  lost   +50.00%
#     0.050  0.050  tied
#     0.050  0.025  won    -50.00%
#     0.000  0.000  tied
#     0.000  0.000  tied
#     0.075  0.075  tied
#     0.025  0.025  tied
#     0.000  0.000  tied
#     0.025  0.025  tied
#     0.050  0.050  tied
#
# won   3 times
# tied 14 times
# lost  3 times
#
# total unique fp went from 13 to 11
#
# false negative percentages
#     0.327  0.400  lost   +22.32%
#     0.400  0.400  tied
#     0.327  0.473  lost   +44.65%
#     0.691  0.654  won     -5.35%
#     0.545  0.473  won    -13.21%
#     0.291  0.364  lost   +25.09%
#     0.218  0.291  lost   +33.49%
#     0.654  0.654  tied
#     0.364  0.473  lost   +29.95%
#     0.291  0.327  lost   +12.37%
#     0.327  0.291  won    -11.01%
#     0.691  0.654  won     -5.35%
#     0.582  0.655  lost   +12.54%
#     0.291  0.400  lost   +37.46%
#     0.364  0.436  lost   +19.78%
#     0.436  0.582  lost   +33.49%
#     0.436  0.364  won    -16.51%
#     0.218  0.291  lost   +33.49%
#     0.291  0.400  lost   +37.46%
#     0.254  0.327  lost   +28.74%
#
# won   5 times
# tied  2 times
# lost 13 times
#
# total unique fn went from 106 to 122
#
# So HTML decorations are still a significant clue when the ham is composed
# of c.l.py traffic.  Again, this should be revisited if the f-n rate is
# slashed again.
#
# Later:  As the amount of training data increased, the effect of retaining
# HTML tags decreased to insignificance.  options.retain_pure_html_tags
# was introduced to control this, and it defaulted to False.  Later, as the
# algorithm improved, retain_pure_html_tags was removed.
#
# Later:  The decision to ignore "redundant" HTML is also dubious, since
# the text/plain and text/html alternatives may have entirely different
# content.  options.ignore_redundant_html was introduced to control this,
# and it defaults to False.  Later:  ignore_redundant_html was also removed.

##############################################################################
# How big should "a word" be?
#
# As I write this, words less than 3 chars are ignored completely, and words
# with more than 12 are special-cased, replaced with a summary "I skipped
# about so-and-so many chars starting with such-and-such a letter" token.
# This makes sense for English if most of the info is in "regular size"
# words.
#
# A test run boosting to 13 had no effect on f-p rate, and did a little
# better or worse than 12 across runs -- overall, no significant difference.
# The database size is smaller at 12, so there's nothing in favor of 13.
# A test at 11 showed a slight but consistent bad effect on the f-n rate
# (lost 12 times, won once, tied 7 times).
#
# A test with no lower bound showed a significant increase in the f-n rate.
# Curious, but not worth digging into.  Boosting the lower bound to 4 is a
# worse idea:  f-p and f-n rates both suffered significantly then.  I didn't
# try testing with lower bound 2.
#
# Anthony Baxter found that boosting the option skip_max_word_size to 20
# from its default of 12 produced a quite dramatic decrease in the number
# of 'unsure' messages.  However, this was coupled with a large increase
# in the FN rate, and it remains unclear whether simply shifting cutoffs
# would have given the same tradeoff (not enough data was posted to tell).
#
# On Tim's c.l.py test, 10-fold CV, ham_cutoff=0.20 and spam_cutoff=0.80:
#
# -> <stat> tested 2000 hams & 1400 spams against 18000 hams & 12600 spams
# [ditto]
#
# filename:    max12   max20
# ham:spam:  20000:14000
#                    20000:14000
# fp total:        2       2       the same
# fp %:         0.01    0.01
# fn total:        0       0       the same
# fn %:         0.00    0.00
# unsure t:      103     100       slight decrease
# unsure %:     0.30    0.29
# real cost:  $40.60  $40.00       slight improvement with these cutoffs
# best cost:  $27.00  $27.40       best possible got slightly worse
# h mean:       0.28    0.27
# h sdev:       2.99    2.92
# s mean:      99.94   99.93
# s sdev:       1.41    1.47
# mean diff:   99.66   99.66
# k:           22.65   22.70
#
# "Best possible" in max20 would have been to boost ham_cutoff to 0.50(!),
# and drop spam_cutoff a little to 0.78.  This would have traded away most
# of the unsures in return for letting 3 spam through:
#
# -> smallest ham & spam cutoffs 0.5 & 0.78
# ->     fp 2; fn 3; unsure ham 11; unsure spam 11
# ->     fp rate 0.01%; fn rate 0.0214%; unsure rate 0.0647%
#
# Best possible in max12 was much the same:
#
# -> largest ham & spam cutoffs 0.5 & 0.78
# ->     fp 2; fn 3; unsure ham 12; unsure spam 8
# ->     fp rate 0.01%; fn rate 0.0214%; unsure rate 0.0588%
#
# The classifier pickle size increased by about 1.5 MB (~8.4% bigger).
#
# Rob Hooft's results were worse:
#
# -> <stat> tested 1600 hams & 580 spams against 14400 hams & 5220 spams
# [...]
# -> <stat> tested 1600 hams & 580 spams against 14400 hams & 5220 spams
# filename:   skip12  skip20
# ham:spam:  16000:5800
#                     16000:5800
# fp total:       12      13
# fp %:         0.07    0.08
# fn total:        7       7
# fn %:         0.12    0.12
# unsure t:      178     184
# unsure %:     0.82    0.84
# real cost: $162.60 $173.80
# best cost: $106.20 $109.60
# h mean:       0.51    0.52
# h sdev:       4.87    4.92
# s mean:      99.42   99.39
# s sdev:       5.22    5.34
# mean diff:   98.91   98.87
# k:            9.80    9.64


# textparts(msg) returns a set containing all the text components of msg.
# There's no point decoding binary blobs (like images).  If a text/plain
# and text/html part happen to have redundant content, it doesn't matter
# to results, since training and scoring are done on the set of all
# words in the msg, without regard to how many times a given word appears.
def textparts(msg):
    """Return a set of all msg parts with content maintype 'text'."""
    return set(filter(lambda part: part.get_content_maintype() == 'text',
                      msg.walk()))

def octetparts(msg):
    """Return a set of all msg parts with type 'application/octet-stream'."""
    return set(filter(lambda part:
                      part.get_content_type() == 'application/octet-stream',
                      msg.walk()))

def imageparts(msg):
    """Return a list of all msg parts with type 'image/*'."""
    # Don't want a set here because we want to be able to process them in
    # order.
    return filter(lambda part:
                  part.get_content_type().startswith('image/'),
                  msg.walk())

has_highbit_char = re.compile(r"[\x80-\xff]").search

# Cheap-ass gimmick to probabilistically find HTML/XML tags.
# Note that <style and HTML comments are handled by crack_html_style()
# and crack_html_comment() instead -- they can be very long, and long
# minimal matches have a nasty habit of blowing the C stack.
html_re = re.compile(r"""
    <
    (?![\s<>])  # e.g., don't match 'a < b' or '<<<' or 'i<<5' or 'a<>b'
    # guessing that other tags are usually "short"
    [^>]{0,256} # search for the end '>', but don't run wild
    >
""", re.VERBOSE | re.DOTALL)

# Trailing letter serves to reject "hostnames" which are really ip
# addresses.  Some spammers forge their apparent ip addresses, so you get
# Received: headers which look like:
#   Received: from 199.249.165.175 ([218.5.93.116])
#       by manatee.mojam.com (8.12.1-20030917/8.12.1) with SMTP id
#       hBIERsqI018090
#       for <itinerary@musi-cal.com>; Thu, 18 Dec 2003 08:28:11 -0600
# "199.249.165.175" is who the spamhaus said it was.  That's really the
# ip address of the receiving host (manatee.mojam.com), which correctly
# identified the sender's ip address as 218.5.93.116.
#
# Similarly, the more complex character set instead of just \S serves to
# reject Received: headers where the message bounces from one user to
# another on the local machine:
#   Received: (from itin@localhost)
#       by manatee.mojam.com (8.12.1-20030917/8.12.1/Submit) id hBIEQFxF018044
#       for skip@manatee.mojam.com; Thu, 18 Dec 2003 08:26:15 -0600
received_host_re = re.compile(r'from ([a-z0-9._-]+[a-z])[)\s]')
# 99% of the time, the receiving host places the sender's ip address in
# square brackets as it should, but every once in awhile it turns up in
# parens.  Yahoo seems to be guilty of this minor infraction:
#   Received: from unknown (66.218.66.218)
#       by m19.grp.scd.yahoo.com with QMQP; 19 Dec 2003 04:06:53 -0000
received_ip_re = re.compile(r'[[(]((\d{1,3}\.?){4})[])]')

received_nntp_ip_re = re.compile(r'((\d{1,3}\.?){4})')

message_id_re = re.compile(r'\s*<[^@]+@([^>]+)>\s*')

# I'm usually just splitting on whitespace, but for subject lines I want to
# break things like "Python/Perl comparison?" up.  OTOH, I don't want to
# break up the unitized numbers in spammish subject phrases like "Increase
# size 79%" or "Now only $29.95!".  Then again, I do want to break up
# "Python-Dev".  Runs of punctuation are also interesting in subject lines.
subject_word_re = re.compile(r"[\w\x80-\xff$.%]+")
punctuation_run_re = re.compile(r'\W+')

fname_sep_re = re.compile(r'[/\\:]')

def crack_filename(fname):
    yield "fname:" + fname
    components = fname_sep_re.split(fname)
    morethan1 = len(components) > 1
    for component in components:
        if morethan1:
            yield "fname comp:" + component
        pieces = urlsep_re.split(component)
        if len(pieces) > 1:
            for piece in pieces:
                yield "fname piece:" + piece

def tokenize_word(word, _len=len, maxword=options["Tokenizer",
                                                  "skip_max_word_size"]):
    n = _len(word)
    # Make sure this range matches in tokenize().
    if 3 <= n <= maxword:
        yield word

    elif n >= 3:
        # A long word.

        # Don't want to skip embedded email addresses.
        # An earlier scheme also split up the y in x@y on '.'.  Not splitting
        # improved the f-n rate; the f-p rate didn't care either way.
        if n < 40 and '.' in word and word.count('@') == 1:
            p1, p2 = word.split('@')
            yield 'email name:' + p1
            yield 'email addr:' + p2

        else:
            # There's value in generating a token indicating roughly how
            # many chars were skipped.  This has real benefit for the f-n
            # rate, but is neutral for the f-p rate.  I don't know why!
            # XXX Figure out why, and/or see if some other way of summarizing
            # XXX this info has greater benefit.
            if options["Tokenizer", "generate_long_skips"]:
                yield "skip:%c %d" % (word[0], n // 10 * 10)
            if has_highbit_char(word):
                hicount = 0
                for i in map(ord, word):
                    if i >= 128:
                        hicount += 1
                yield "8bit%%:%d" % round(hicount * 100.0 / len(word))

# Generate tokens for:
#    Content-Type
#        and its type= param
#    Content-Dispostion
#        and its filename= param
#    all the charsets
#
# This has huge benefit for the f-n rate, and virtually no effect on the f-p
# rate, although it does reduce the variance of the f-p rate across different
# training sets (really marginal msgs, like a brief HTML msg saying just
# "unsubscribe me", are almost always tagged as spam now; before they were
# right on the edge, and now the multipart/alternative pushes them over it
# more consistently).
#
# XXX I put all of this in as one chunk.  I don't know which parts are
# XXX most effective; it could be that some parts don't help at all.  But
# XXX given the nature of the c.l.py tests, it's not surprising that the
# XXX     'content-type:text/html'
# XXX token is now the single most powerful spam indicator (== makes it
# XXX into the nbest list most often).  What *is* a little surprising is
# XXX that this doesn't push more mixed-type msgs into the f-p camp --
# XXX unlike looking at *all* HTML tags, this is just one spam indicator
# XXX instead of dozens, so relevant msg content can cancel it out.
#
# A bug in this code prevented Content-Transfer-Encoding from getting
# picked up.  Fixing that bug showed that it didn't help, so the corrected
# code is disabled now (left column without Content-Transfer-Encoding,
# right column with it);
#
# false positive percentages
#    0.000  0.000  tied
#    0.000  0.000  tied
#    0.100  0.100  tied
#    0.000  0.000  tied
#    0.025  0.025  tied
#    0.025  0.025  tied
#    0.100  0.100  tied
#    0.025  0.025  tied
#    0.025  0.025  tied
#    0.050  0.050  tied
#    0.100  0.100  tied
#    0.025  0.025  tied
#    0.025  0.025  tied
#    0.025  0.025  tied
#    0.025  0.025  tied
#    0.025  0.025  tied
#    0.025  0.025  tied
#    0.000  0.025  lost  +(was 0)
#    0.025  0.025  tied
#    0.100  0.100  tied
#
# won   0 times
# tied 19 times
# lost  1 times
#
# total unique fp went from 9 to 10
#
# false negative percentages
#    0.364  0.400  lost    +9.89%
#    0.400  0.364  won     -9.00%
#    0.400  0.436  lost    +9.00%
#    0.909  0.872  won     -4.07%
#    0.836  0.836  tied
#    0.618  0.618  tied
#    0.291  0.291  tied
#    1.018  0.981  won     -3.63%
#    0.982  0.982  tied
#    0.727  0.727  tied
#    0.800  0.800  tied
#    1.163  1.127  won     -3.10%
#    0.764  0.836  lost    +9.42%
#    0.473  0.473  tied
#    0.473  0.618  lost   +30.66%
#    0.727  0.763  lost    +4.95%
#    0.655  0.618  won     -5.65%
#    0.509  0.473  won     -7.07%
#    0.545  0.582  lost    +6.79%
#    0.509  0.509  tied
#
# won   6 times
# tied  8 times
# lost  6 times
#
# total unique fn went from 168 to 169

# For support of the replace_nonascii_chars option, build a string.translate
# table that maps all high-bit chars and control chars to a '?' character.

non_ascii_translate_tab = ['?'] * 256
# leave blank up to (but not including) DEL alone
for i in range(32, 127):
    non_ascii_translate_tab[i] = chr(i)
# leave "normal" whitespace alone
for ch in ' \t\r\n':
    non_ascii_translate_tab[ord(ch)] = ch
del i, ch

non_ascii_translate_tab = ''.join(non_ascii_translate_tab)


def crack_content_xyz(msg):
    yield 'content-type:' + msg.get_content_type()

    x = msg.get_param('type')
    if x is not None:
        yield 'content-type/type:' + x.lower()

    try:
        for x in msg.get_charsets(None):
            if x is not None:
                yield 'charset:' + x.lower()
    except UnicodeEncodeError:
        # Bad messages can cause an exception here.
        # See [ 1175439 ] UnicodeEncodeError raised for bogus Content-Type
        #                 header
        yield 'charset:invalid_unicode'

    x = msg.get('content-disposition')
    if x is not None:
        yield 'content-disposition:' + x.lower()

    try:
        fname = msg.get_filename()
        if fname is not None:
            for x in crack_filename(fname):
                yield 'filename:' + x
    except TypeError:
        # bug in email pkg?  see the thread beginning at
        # http://mail.python.org/pipermail/spambayes/2003-September/008006.html
        # and
        # http://mail.python.org/pipermail/spambayes-dev/2003-September/001177.html
        yield "filename:<bogus>"

    if 0:   # disabled; see comment before function
        x = msg.get('content-transfer-encoding')
        if x is not None:
            yield 'content-transfer-encoding:' + x.lower()

# The base64 decoder is actually very forgiving, but flubs one case:
# if no padding is required (no trailing '='), it continues to read
# following lines as if they were still part of the base64 part.  We're
# actually stricter here.  The *point* is that some mailers tack plain
# text on to the end of base64-encoded text sections.

# Match a line of base64, up to & including the trailing newline.
# We allow for optional leading and trailing whitespace, and don't care
# about line length, but other than that are strict.  Group 1 is non-empty
# after a match iff the last significant char on the line is '='; in that
# case, it must be the last line of the base64 section.
base64_re = re.compile(r"""
    [ \t]*
    [a-zA-Z0-9+/]*
    (=*)
    [ \t]*
    \r?
    \n
""", re.VERBOSE)

def try_to_repair_damaged_base64(text):
    i = 0
    while True:
        # text[:i] looks like base64.  Does the line starting at i also?
        m = base64_re.match(text, i)
        if not m:
            break
        i = m.end()
        if m.group(1):
            # This line has a trailing '=' -- the base64 part is done.
            break
    base64text = ''
    if i:
        base64 = text[:i]
        try:
            base64text = binascii.a2b_base64(base64)
        except:
            # There's no point in tokenizing raw base64 gibberish.
            pass
    return base64text + text[i:]

def breakdown_host(host):
    parts = host.split('.')
    for i in range(1, len(parts) + 1):
        yield '.'.join(parts[-i:])

def breakdown_ipaddr(ipaddr):
    parts = ipaddr.split('.')
    for i in range(1, 5):
        yield '.'.join(parts[:i])

def log2(n, log=math.log, c=math.log(2)):
    return log(n)/c


class Stripper(object):

    # The retained portions are catenated together with self.separator.
    # CAUTION:  This used to be blank.  But then I noticed spam putting
    # HTML comments embedded in words, like
    #     FR<!--slkdflskjf-->EE!
    # Breaking this into "FR" and "EE!" wasn't a real help <wink>.
    separator = ''  # a subclass can override if this isn't appropriate

    def __init__(self, find_start, find_end):
        # find_start and find_end have signature
        #     string, int -> match_object
        # where the search starts at string[int:int].  If a match isn't found,
        # they must return None.  The match_object for find_start, if not
        # None, is passed to self.tokenize, which returns a (possibly empty)
        # list of tokens to generate.  Subclasses may override tokenize().
        # Text between find_start and find_end is thrown away, except for
        # whatever tokenize() produces.  A match_object must support method
        #     span() -> int, int    # the slice bounds of what was matched
        self.find_start = find_start
        self.find_end = find_end

    # Efficiency note:  This is cheaper than it looks if there aren't any
    # special sections.  Under the covers, string[0:] is optimized to
    # return string (no new object is built), and likewise ' '.join([string])
    # is optimized to return string.  It would actually slow this code down
    # to special-case these "do nothing" special cases at the Python level!

    def analyze(self, text):
        i = 0
        retained = []
        pushretained = retained.append
        tokens = []
        while True:
            m = self.find_start(text, i)
            if not m:
                pushretained(text[i:])
                break
            start, end = m.span()
            pushretained(text[i : start])
            tokens.extend(self.tokenize(m))
            m = self.find_end(text, end)
            if not m:
                # No matching end - act as if the open
                # tag did not exist.
                pushretained(text[start:])
                break
            dummy, i = m.span()
        return self.separator.join(retained), tokens

    def tokenize(self, match_object):
        # Override this if you want to suck info out of the start pattern.
        return []

# Strip out uuencoded sections and produce tokens.  The return value
# is (new_text, sequence_of_tokens), where new_text no longer contains
# uuencoded stuff.  Note that we're not bothering to decode it!  Maybe
# we should.  One of my persistent false negatives is a spam containing
# nothing but a uuencoded money.txt; OTOH, uuencode seems to be on
# its way out (that's an old spam).

uuencode_begin_re = re.compile(r"""
    ^begin \s+
    (\S+) \s+   # capture mode
    (\S+) \s*   # capture filename
    $
""", re.VERBOSE | re.MULTILINE)

uuencode_end_re = re.compile(r"^end\s*\n", re.MULTILINE)

class UUencodeStripper(Stripper):
    def __init__(self):
        Stripper.__init__(self, uuencode_begin_re.search,
                                uuencode_end_re.search)

    def tokenize(self, m):
        mode, fname = m.groups()
        return (['uuencode mode:%s' % mode] +
                ['uuencode:%s' % x for x in crack_filename(fname)])

crack_uuencode = UUencodeStripper().analyze


# Strip and specially tokenize embedded URLish thingies.

url_fancy_re = re.compile(r""" 
    \b                      # the preceeding character must not be alphanumeric
    (?: 
        (?:
            (https? | ftp)  # capture the protocol
            ://             # skip the boilerplate
        )|
        (?= ftp\.[^\.\s<>"'\x7f-\xff] )|  # allow the protocol to be missing, but only if
        (?= www\.[^\.\s<>"'\x7f-\xff] )   # the rest of the url starts "www.x" or "ftp.x" 
    )
    # Do a reasonable attempt at detecting the end.  It may or may not
    # be in HTML, may or may not be in quotes, etc.  If it's full of %
    # escapes, cool -- that's a clue too.
    ([^\s<>"'\x7f-\xff]+)  # capture the guts
""", re.VERBOSE)                        # '

url_re = re.compile(r"""
    (https? | ftp)  # capture the protocol
    ://             # skip the boilerplate
    # Do a reasonable attempt at detecting the end.  It may or may not
    # be in HTML, may or may not be in quotes, etc.  If it's full of %
    # escapes, cool -- that's a clue too.
    ([^\s<>"'\x7f-\xff]+)  # capture the guts
""", re.VERBOSE)                        # '


urlsep_re = re.compile(r"[;?:@&=+,$.]")

class URLStripper(Stripper):
    def __init__(self):
        # The empty regexp matches anything at once.
        if options["Tokenizer", "x-fancy_url_recognition"]:
            search = url_fancy_re.search
        else:
            search = url_re.search
        Stripper.__init__(self, search, re.compile("").search)

    def tokenize(self, m):
        proto, guts = m.groups()
        assert guts
        if proto is None:
            if guts.lower().startswith("www"):
                proto = "http"
            elif guts.lower().startswith("ftp"):
                proto = "ftp"
            else:
                proto = "unknown"
        tokens = ["proto:" + proto]
        pushclue = tokens.append

        if options["Tokenizer", "x-pick_apart_urls"]:
            url = proto + "://" + guts

            escapes = re.findall(r'%..', guts)
            # roughly how many %nn escapes are there?
            if escapes:
                pushclue("url:%%%d" % int(log2(len(escapes))))
            # %nn escapes are usually intentional obfuscation.  Generate a
            # lot of correlated tokens if the URL contains a lot of them.
            # The classifier will learn which specific ones are and aren't
            # spammy.
            tokens.extend(["url:" + escape for escape in escapes])

            # now remove any obfuscation and probe around a bit
            url = urllib.unquote(url)
            scheme, netloc, path, params, query, frag = urlparse.urlparse(url)

            if options["Tokenizer", "x-lookup_ip"]:
                ips = cache.lookup(netloc)
                if not ips:
                    pushclue("url-ip:lookup error")
                else:
                    for clue in gen_dotted_quad_clues("url-ip", ips):
                        pushclue(clue)

            # one common technique in bogus "please (re-)authorize yourself"
            # scams is to make it appear as if you're visiting a valid
            # payment-oriented site like PayPal, CitiBank or eBay, when you
            # actually aren't.  The company's web server appears as the
            # beginning of an often long username element in the URL such as
            # http://www.paypal.com%65%43%99%35@10.0.1.1/iwantyourccinfo
            # generally with an innocuous-looking fragment of text or a
            # valid URL as the highlighted link.  Usernames should rarely
            # appear in URLs (perhaps in a local bookmark you established),
            # and never in a URL you receive from an unsolicited email or
            # another website.
            user_pwd, host_port = urllib.splituser(netloc)
            if user_pwd is not None:
                pushclue("url:has user")

            host, port = urllib.splitport(host_port)
            # web servers listening on non-standard ports are suspicious ...
            if port is not None:
                if (scheme == "http" and port != '80' or
                    scheme == "https" and port != '443'):
                    pushclue("url:non-standard %s port" % scheme)

            # ... as are web servers associated with raw ip addresses
            if re.match("(\d+\.?){4,4}$", host) is not None:
                pushclue("url:ip addr")

            # make sure we later tokenize the unobfuscated url bits
            proto, guts = url.split("://", 1)

        # Lose the trailing punctuation for casual embedding, like:
        #     The code is at http://mystuff.org/here?  Didn't resolve.
        # or
        #     I found it at http://mystuff.org/there/.  Thanks!
        while guts and guts[-1] in '.:?!/':
            guts = guts[:-1]
        for piece in guts.split('/'):
            for chunk in urlsep_re.split(piece):
                pushclue("url:" + chunk)
        return tokens

received_complaints_re = re.compile(r'\([a-z]+(?:\s+[a-z]+)+\)')

class SlurpingURLStripper(URLStripper):
    def __init__(self):
        URLStripper.__init__(self)

    def analyze(self, text):
        # If there are no URLS, then we need to clear the
        # wordstream, or whatever was there from the last message
        # will be used.
        classifier.slurp_wordstream = None
        # Continue as normal.
        return URLStripper.analyze(self, text)

    def tokenize(self, m):
        # XXX Note that the 'slurped' tokens are *always* trained
        # XXX on; it would be simple to change/parameterize this.
        tokens = URLStripper.tokenize(self, m)
        if not options["URLRetriever", "x-slurp_urls"]:
            return tokens

        proto, guts = m.groups()
        if proto != "http":
            return tokens

        assert guts
        while guts and guts[-1] in '.:;?!/)':
            guts = guts[:-1]

        classifier.slurp_wordstream = (proto, guts)
        return tokens

if options["URLRetriever", "x-slurp_urls"]:
    crack_urls = SlurpingURLStripper().analyze
else:
    crack_urls = URLStripper().analyze

# Nuke HTML <style gimmicks.
html_style_start_re = re.compile(r"""
    < \s* style\b [^>]* >
""", re.VERBOSE)

class StyleStripper(Stripper):
    def __init__(self):
        Stripper.__init__(self, html_style_start_re.search,
                                re.compile(r"</style>").search)

crack_html_style = StyleStripper().analyze

# Nuke HTML comments.

class CommentStripper(Stripper):
    def __init__(self):
        Stripper.__init__(self,
                          re.compile(r"<!--|<\s*comment\s*[^>]*>").search,
                          re.compile(r"-->|</comment>").search)

crack_html_comment = CommentStripper().analyze

# Nuke stuff between <noframes> </noframes> tags.
class NoframesStripper(Stripper):
    def __init__(self):
        Stripper.__init__(self,
                          re.compile(r"<\s*noframes\s*>").search,
                          re.compile(r"</noframes\s*>").search)

crack_noframes = NoframesStripper().analyze

# Scan HTML for constructs often seen in viruses and worms.
# <script  </script
# <iframe  </iframe
# src=cid:
# height=0  width=0

virus_re = re.compile(r"""
    < /? \s* (?: script | iframe) \b
|   \b src= ['"]? cid:
|   \b (?: height | width) = ['"]? 0
""", re.VERBOSE)                        # '

def find_html_virus_clues(text):
    for bingo in virus_re.findall(text):
        yield bingo



numeric_entity_re = re.compile(r'&#(\d+);')
def numeric_entity_replacer(m):
    try:
        return chr(int(m.group(1)))
    except:
        return '?'


breaking_entity_re = re.compile(r"""
    &nbsp;
|   < (?: p
      |   br
      )
    >
""", re.VERBOSE)

class Tokenizer:

    date_hms_re = re.compile(r' (?P<hour>[0-9][0-9])'
                             r':(?P<minute>[0-9][0-9])'
                             r'(?::[0-9][0-9])? ')

    date_formats = ("%a, %d %b %Y %H:%M:%S (%Z)",
                    "%a, %d %b %Y %H:%M:%S %Z",
                    "%d %b %Y %H:%M:%S (%Z)",
                    "%d %b %Y %H:%M:%S %Z",
                    "%a, %d %b %Y %H:%M (%Z)",
                    "%a, %d %b %Y %H:%M %Z",
                    "%d %b %Y %H:%M (%Z)",
                    "%d %b %Y %H:%M %Z")

    def __init__(self):
        self.setup()

    def setup(self):
        """Get the tokenizer ready to use; this should be called after
        all options have been set."""
        # We put this here, rather than in __init__, so that this can be
        # done after we set options at runtime (since the tokenizer
        # instance is generally created when this module is imported).
        if options["Tokenizer", "basic_header_tokenize"]:
            self.basic_skip = [re.compile(s)
                               for s in options["Tokenizer",
                                                "basic_header_skip"]]

    def get_message(self, obj):
        return get_message(obj)

    def tokenize(self, obj):
        msg = self.get_message(obj)

        for tok in self.tokenize_headers(msg):
            yield tok
        for tok in self.tokenize_body(msg):
            yield tok

    def tokenize_headers(self, msg):
        # Special tagging of header lines and MIME metadata.

        # Content-{Type, Disposition} and their params, and charsets.
        # This is done for all MIME sections.
        for x in msg.walk():
            for w in crack_content_xyz(x):
                yield w

        # The rest is solely tokenization of header lines.
        # XXX The headers in my (Tim's) spam and ham corpora are so different
        # XXX (they came from different sources) that including several kinds
        # XXX of header analysis renders the classifier's job trivial.  So
        # XXX lots of this is crippled now, controlled by an ever-growing
        # XXX collection of funky options.

        # Basic header tokenization
        # Tokenize the contents of each header field in the way Subject lines
        # are tokenized later.
        # XXX Different kinds of tokenization have gotten better results on
        # XXX different header lines.  No experiments have been run on
        # XXX whether the best choice is being made for each of the header
        # XXX lines tokenized by this section.
        # The name of the header is used as a tag.  Tokens look like
        # "header:word".  The basic approach is simple and effective, but
        # also very sensitive to biases in the ham and spam collections.
        # For example, if the ham and spam were collected at different
        # times, several headers with date/time information will become
        # the best discriminators.
        # (Not just Date, but Received and X-From_.)
        if options["Tokenizer", "basic_header_tokenize"]:
            for k, v in msg.items():
                k = k.lower()
                for rx in self.basic_skip:
                    if rx.match(k):
                        break   # do nothing -- we're supposed to skip this
                else:
                    # Never found a match -- don't skip this.
                    for w in subject_word_re.findall(v):
                        for t in tokenize_word(w):
                            yield "%s:%s" % (k, t)
            if options["Tokenizer", "basic_header_tokenize_only"]:
                return

        # Habeas Headers - see http://www.habeas.com
        if options["Tokenizer", "x-search_for_habeas_headers"]:
            habeas_headers = [
("X-Habeas-SWE-1", "winter into spring"),
("X-Habeas-SWE-2", "brightly anticipated"),
("X-Habeas-SWE-3", "like Habeas SWE (tm)"),
("X-Habeas-SWE-4", "Copyright 2002 Habeas (tm)"),
("X-Habeas-SWE-5", "Sender Warranted Email (SWE) (tm). The sender of this"),
("X-Habeas-SWE-6", "email in exchange for a license for this Habeas"),
("X-Habeas-SWE-7", "warrant mark warrants that this is a Habeas Compliant"),
("X-Habeas-SWE-8", "Message (HCM) and not spam. Please report use of this"),
("X-Habeas-SWE-9", "mark in spam to <http://www.habeas.com/report/>.")
            ]
            valid_habeas = 0
            invalid_habeas = False
            for opt, val in habeas_headers:
                habeas = msg.get(opt)
                if habeas is not None:
                    if options["Tokenizer", "x-reduce_habeas_headers"]:
                        if habeas == val:
                            valid_habeas += 1
                        else:
                            invalid_habeas = True
                    else:
                        if habeas == val:
                            yield opt.lower() + ":valid"
                        else:
                            yield opt.lower() + ":invalid"
            if options["Tokenizer", "x-reduce_habeas_headers"]:
                # If there was any invalid line, we record as invalid.
                # If all nine lines were correct, we record as valid.
                # Otherwise we ignore.
                if invalid_habeas == True:
                    yield "x-habeas-swe:invalid"
                elif valid_habeas == 9:
                    yield "x-habeas-swe:valid"

        # Subject:
        # Don't ignore case in Subject lines; e.g., 'free' versus 'FREE' is
        # especially significant in this context.  Experiment showed a small
        # but real benefit to keeping case intact in this specific context.
        x = msg.get('subject', '')
        try:
            subjcharsetlist = email.Header.decode_header(x)
        except (binascii.Error, email.Errors.HeaderParseError, ValueError):
            subjcharsetlist = [(x, 'invalid')]
        for x, subjcharset in subjcharsetlist:
            if subjcharset is not None:
                yield 'subjectcharset:' + subjcharset
            # this is a workaround for a bug in the csv module in Python
            # <= 2.3.4 and 2.4.0 (fixed in 2.5)
            x = x.replace('\r', ' ')
            for w in subject_word_re.findall(x):
                for t in tokenize_word(w):
                    yield 'subject:' + t
            for w in punctuation_run_re.findall(x):
                yield 'subject:' + w

        # Dang -- I can't use Sender:.  If I do,
        #     'sender:email name:python-list-admin'
        # becomes the most powerful indicator in the whole database.
        #
        # From:         # this helps both rates
        # Reply-To:     # my error rates are too low now to tell about this
        #               # one (smalls wins & losses across runs, overall
        #               # not significant), so leaving it out
        # To:, Cc:      # These can help, if your ham and spam are sourced
        #               # from the same location. If not, they'll be horrible.
        for field in options["Tokenizer", "address_headers"]:
            addrlist = msg.get_all(field, [])
            if not addrlist:
                yield field + ":none"
                continue

            noname_count = 0
            for name, addr in email.Utils.getaddresses(addrlist):
                if name:
                    try:
                        subjcharsetlist = email.Header.decode_header(name)
                    except (binascii.Error, email.Errors.HeaderParseError,
                            ValueError):
                        subjcharsetlist = [(name, 'invalid')]
                    for name, charset in subjcharsetlist:
                        yield "%s:name:%s" % (field, name.lower())
                        if charset is not None:
                            yield "%s:charset:%s" % (field, charset)
                else:
                    noname_count += 1
                if addr:
                    for w in addr.lower().split('@'):
                        yield "%s:addr:%s" % (field, w)
                else:
                    yield field + ":addr:none"

            if noname_count:
                yield "%s:no real name:2**%d" % (field,
                                                 round(log2(noname_count)))

        # Spammers sometimes send out mail alphabetically to fairly large
        # numbers of addresses.  This results in headers like:
        #   To: <itinerart@videotron.ca>
        #   Cc: <itinerant@skyful.com>, <itinerant@netillusions.net>,
        #       <itineraries@musi-cal.com>, <itinerario@rullet.leidenuniv.nl>,
        #       <itinerance@sorengo.com>
        #
        # This token attempts to exploit that property.  The above would
        # give a common prefix of "itinera" for 6 addresses, yielding a
        # gross score of 42.  We group scores into buckets by dividing by 10
        # to yield a final token value of "pfxlen:04".  The length test
        # eliminates the bad case where the message was sent to a single
        # individual.
        if options["Tokenizer", "summarize_email_prefixes"]:
            all_addrs = []
            addresses = msg.get_all('to', []) + msg.get_all('cc', [])
            for name, addr in email.Utils.getaddresses(addresses):
                all_addrs.append(addr.lower())

            if len(all_addrs) > 1:
                # don't be fooled by "os.path." - commonprefix
                # operates char-by-char!
                pfx = os.path.commonprefix(all_addrs)
                if pfx:
                    score = (len(pfx) * len(all_addrs)) // 10
                    # After staring at pfxlen:* values generated from a large
                    # number of ham & spam I saw that any scores greater
                    # than 3 were always associated with spam.  Collapsing
                    # all such scores into a single token avoids a bunch of
                    # hapaxes like "pfxlen:28".
                    if score > 3:
                        yield "pfxlen:big"
                    else:
                        yield "pfxlen:%d" % score

        # same idea as above, but works for addresses in the same domain
        # like
        #   To: "skip" <bugs@mojam.com>, <chris@mojam.com>,
        #       <concertmaster@mojam.com>, <concerts@mojam.com>,
        #       <design@mojam.com>, <rob@mojam.com>, <skip@mojam.com>
        if options["Tokenizer", "summarize_email_suffixes"]:
            all_addrs = []
            addresses = msg.get_all('to', []) + msg.get_all('cc', [])
            for name, addr in email.Utils.getaddresses(addresses):
                # flip address code so following logic is the same as
                # that for prefixes
                addr = list(addr)
                addr.reverse()
                addr = "".join(addr)
                all_addrs.append(addr.lower())

            if len(all_addrs) > 1:
                # don't be fooled by "os.path." - commonprefix
                # operates char-by-char!
                sfx = os.path.commonprefix(all_addrs)
                if sfx:
                    score = (len(sfx) * len(all_addrs)) // 10
                    # Similar analysis as above regarding suffix length
                    # I suspect the best cutoff is probably dependent on
                    # how long the recipient domain is (e.g. "mojam.com" vs.
                    # "montanaro.dyndns.org")
                    if score > 5:
                        yield "sfxlen:big"
                    else:
                        yield "sfxlen:%d" % score

        # To:
        # Cc:
        # Count the number of addresses in each of the recipient headers.
        for field in ('to', 'cc'):
            count = 0
            for addrs in msg.get_all(field, []):
                count += len(addrs.split(','))
            if count > 0:
                yield '%s:2**%d' % (field, round(log2(count)))

        # These headers seem to work best if they're not tokenized:  just
        # normalize case and whitespace.
        # X-Mailer:  This is a pure and significant win for the f-n rate; f-p
        #            rate isn't affected.
        for field in ('x-mailer',):
            prefix = field + ':'
            x = msg.get(field, 'none').lower()
            yield prefix + ' '.join(x.split())

        # Received:
        # Neil Schemenauer reports good results from this.
        if options["Tokenizer", "mine_received_headers"]:
            for header in msg.get_all("received", ()):
                # everything here should be case insensitive and not be
                # split across continuation lines, so normalize whitespace
                # and letter case just once per header
                header = ' '.join(header.split()).lower()

                for clue in received_complaints_re.findall(header):
                    yield 'received:' + clue

                for pat, breakdown in [(received_host_re, breakdown_host),
                                       (received_ip_re, breakdown_ipaddr)]:
                    m = pat.search(header)
                    if m:
                        for tok in breakdown(m.group(1)):
                            yield 'received:' + tok

        # Lots of spam gets posted on Usenet.  If it is then gatewayed to a
        # mailing list perhaps the NNTP-Posting-Host info will yield some
        # useful clues.
        if options["Tokenizer", "x-mine_nntp_headers"]:
            for clue in mine_nntp(msg):
                yield clue

        # Message-Id:  This seems to be a small win and should not
        # adversely affect a mixed source corpus so it's always enabled.
        msgid = msg.get("message-id", "")
        m = message_id_re.match(msgid)
        if m:
            # looks okay, return the hostname
            yield 'message-id:@%s' % m.group(1)
        else:
            # might be weird instead of invalid but who cares?
            yield 'message-id:invalid'

        # As suggested by Anthony Baxter, merely counting the number of
        # header lines, and in a case-sensitive way, has real value.
        # For example, all-caps SUBJECT is a strong spam clue, while
        # X-Complaints-To a strong ham clue.
        x2n = {}
        if options["Tokenizer", "count_all_header_lines"]:
            for x in msg.keys():
                x2n[x] = x2n.get(x, 0) + 1
        else:
            # Do a "safe" approximation to that.  When spam and ham are
            # collected from different sources, the count of some header
            # lines can be a too strong a discriminator for accidental
            # reasons.
            safe_headers = options["Tokenizer", "safe_headers"]
            for x in msg.keys():
                if x.lower() in safe_headers:
                    x2n[x] = x2n.get(x, 0) + 1
        for x in x2n.items():
            yield "header:%s:%d" % x
        if options["Tokenizer", "record_header_absence"]:
            for k in x2n:
                if not k.lower() in options["Tokenizer", "safe_headers"]:
                    yield "noheader:" + k

    def tokenize_text(self, text, maxword=options["Tokenizer",
                                                  "skip_max_word_size"]):
        """Tokenize everything in the chunk of text we were handed."""
        short_runs = set()
        short_count = 0
        for w in text.split():
            n = len(w)
            if n < 3:
                # count how many short words we see in a row - meant to
                # latch onto crap like this:
                # X j A m N j A d X h
                # M k E z R d I p D u I m A c
                # C o I d A t L j I v S j
                short_count += 1
            else:
                if short_count:
                    short_runs.add(short_count)
                    short_count = 0
                # Make sure this range matches in tokenize_word().
                if 3 <= n <= maxword:
                    yield w

                elif n >= 3:
                    for t in tokenize_word(w):
                        yield t
        if short_runs and options["Tokenizer", "x-short_runs"]:
            yield "short:%d" % int(log2(max(short_runs)))

    def tokenize_body(self, msg):
        """Generate a stream of tokens from an email Message.

        If options['Tokenizer', 'check_octets'] is True, the first few
        undecoded characters of application/octet-stream parts of the
        message body become tokens.
        """

        if options["Tokenizer", "check_octets"]:
            # Find, decode application/octet-stream parts of the body,
            # tokenizing the first few characters of each chunk.
            for part in octetparts(msg):
                try:
                    text = part.get_payload(decode=True)
                except:
                    yield "control: couldn't decode octet"
                    text = part.get_payload(decode=False)

                if text is None:
                    yield "control: octet payload is None"
                    continue

                yield "octet:%s" % text[:options["Tokenizer",
                                                 "octet_prefix_size"]]

        parts = imageparts(msg)
        if options["Tokenizer", "image_size"]:
            # Find image/* parts of the body, calculating the log(size) of
            # each image.

            total_len = 0
            for part in parts:
                try:
                    text = part.get_payload(decode=True)
                except:
                    yield "control: couldn't decode image"
                    text = part.get_payload(decode=False)

                total_len += len(text or "")
                if text is None:
                    yield "control: image payload is None"

            if total_len:
                yield "image-size:2**%d" % round(log2(total_len))

        if options["Tokenizer", "crack_images"]:
            engine_name = options["Tokenizer", 'ocr_engine']
            from spambayes.ImageStripper import crack_images
            text, tokens = crack_images(engine_name, parts)
            for t in tokens:
                yield t
            for t in self.tokenize_text(text):
                yield t

        # Find, decode (base64, qp), and tokenize textual parts of the body.
        for part in textparts(msg):
            # Decode, or take it as-is if decoding fails.
            try:
                text = part.get_payload(decode=True)
            except:
                yield "control: couldn't decode"
                text = part.get_payload(decode=False)
                if text is not None:
                    text = try_to_repair_damaged_base64(text)

            if text is None:
                yield 'control: payload is None'
                continue

            # Replace numeric character entities (like &#97; for the letter
            # 'a').
            text = numeric_entity_re.sub(numeric_entity_replacer, text)

            # Normalize case.
            text = text.lower()

            if options["Tokenizer", "replace_nonascii_chars"]:
                # Replace high-bit chars and control chars with '?'.
                text = text.translate(non_ascii_translate_tab)

            for t in find_html_virus_clues(text):
                yield "virus:%s" % t

            # Get rid of uuencoded sections, embedded URLs, <style gimmicks,
            # and HTML comments.
            for cracker in (crack_uuencode,
                            crack_urls,
                            crack_html_style,
                            crack_html_comment,
                            crack_noframes):
                text, tokens = cracker(text)
                for t in tokens:
                    yield t

            # Remove HTML/XML tags.  Also &nbsp;.  <br> and <p> tags should
            # create a space too.
            text = breaking_entity_re.sub(' ', text)
            # It's important to eliminate HTML tags rather than, e.g.,
            # replace them with a blank (as this code used to do), else
            # simple tricks like
            #    Wr<!$FS|i|R3$s80sA >inkle Reduc<!$FS|i|R3$s80sA >tion
            # can be used to disguise words.  <br> and <p> were special-
            # cased just above (because browsers break text on those,
            # they can't be used to hide words effectively).
            text = html_re.sub('', text)

            for t in self.tokenize_text(text):
                yield t

# Mine NNTP-Posting-Host headers.  This is part of an effort to put some
# SpamBayes smarts into the Mailman gate_news program.  On mail.python.org
# messages arriving via Usenet bypass all the barriers the Python
# postmasters have erected against mail-borne spam, including not running
# them through SpamBayes.

# Anecdotal evidence on comp.lang.python suggests that certain posting hosts
# (I won't name any names, but the one mentioned heavily starts with a
# 'g'and has two 'o's in the middle) are more prone to let spam leak into
# Usenet.  My initial testing (also hardly more than anecdotal) suggests
# there are useful clues awaiting extractiotn from this header.
def mine_nntp(msg):
    nntp_headers = msg.get_all("nntp-posting-host", ())
    for address in nntp_headers:
        if received_nntp_ip_re.match(address):
            for clue in gen_dotted_quad_clues("nntp-host", [address]):
                yield clue
            names = cache.lookup(address)
            if names:
                yield 'nntp-host-ip:has-reverse'
                yield 'nntp-host-name:%s' % names[0]
                yield ('nntp-host-domain:%s' %
                       '.'.join(names[0].split('.')[-2:]))
        else:
            # assume it's a hostname
            name = address
            yield 'nntp-host-name:%s' % name
            yield ('nntp-host-domain:%s' %
                   '.'.join(name.split('.')[-2:]))
            addresses = cache.lookup(name)
            if addresses:
                for clue in gen_dotted_quad_clues("nntp-host-ip", addresses):
                    yield clue
                if cache.lookup(addresses[0], qType="PTR") == name:
                    yield 'nntp-host-ip:has-reverse'

def gen_dotted_quad_clues(pfx, ips):
    for ip in ips:
        yield "%s:%s/32" % (pfx, ip)
        dottedQuadList = ip.split(".")
        yield "%s:%s/8" % (pfx, dottedQuadList[0])
        yield "%s:%s.%s/16" % (pfx, dottedQuadList[0],
                               dottedQuadList[1])
        yield "%s:%s.%s.%s/24" % (pfx, dottedQuadList[0],
                                  dottedQuadList[1],
                                  dottedQuadList[2])

global_tokenizer = Tokenizer()
tokenize = global_tokenizer.tokenize