#!/usr/bin/env python

"""
$Id$

Copyright (c) 2006-2010 sqlmap developers (http://sqlmap.sourceforge.net/)
See the file 'doc/COPYING' for copying permission
"""

import re

from difflib import SequenceMatcher

from lib.core.common import wasLastRequestError
from lib.core.data import conf
from lib.core.data import kb
from lib.core.data import logger
from lib.core.settings import ETA

def comparison(page, headers=None, getSeqMatcher=False, pageLength=None):
    if page is None and pageLength is None:
        return None

    # In case of an DBMS error page return None
    if wasLastRequestError():
        return None

    regExpResults = None

    if page:
        # String to be excluded before calculating page hash
        if conf.eString and conf.eString in page:
            index              = page.index(conf.eString)
            length             = len(conf.eString)
            pageWithoutString  = page[:index]
            pageWithoutString += page[index+length:]
            page               = pageWithoutString

        # Regular expression matches to be excluded before calculating page hash
        if conf.eRegexp:
            regExpResults = re.findall(conf.eRegexp, page, re.I | re.M)

            if regExpResults:
                for regExpResult in regExpResults:
                    index              = page.index(regExpResult)
                    length             = len(regExpResult)
                    pageWithoutRegExp  = page[:index]
                    pageWithoutRegExp += page[index+length:]
                    page               = pageWithoutRegExp

        # String to match in page when the query is valid
        if conf.string:
            return conf.string in page

        # Regular expression to match in page when the query is valid
        if conf.regexp:
            return re.search(conf.regexp, page, re.I | re.M) is not None

        # Dynamic content lines to be excluded before comparison
        if not kb.nullConnection and not conf.longestCommon:
            for item in kb.dynamicMarkings:
                prefix, postfix = item

                if prefix is None:
                    page = re.sub('(?s)^.+%s' % postfix, postfix, page)
                elif postfix is None:
                    page = re.sub('(?s)%s.+$' % prefix, prefix, page)
                else:
                    page = re.sub('(?s)%s.+%s' % (prefix, postfix), '%s%s' % (prefix, postfix), page)

        if not pageLength:
            pageLength = len(page)

    if kb.locks.seqLock:
        kb.locks.seqLock.acquire()

    if conf.longestCommon:
        (firstPage, secondPage) = (conf.seqMatcher.a, page)
        match = SequenceMatcher(None, firstPage, secondPage).find_longest_match(0, len(firstPage), 0, len(secondPage))
        ratio = round(SequenceMatcher(None, firstPage[match[0]:match[0]+match[2]], secondPage[match[1]:match[1]+match[2]]).ratio(), 3)

    elif not conf.eRegexp and not conf.eString and kb.nullConnection and pageLength:
        ratio = 1. * pageLength / len(conf.seqMatcher.a)

        if ratio > 1.:
            ratio = 1. / ratio
    else:
        conf.seqMatcher.set_seq2(page)
        ratio = round(conf.seqMatcher.ratio(), 3)

    if kb.locks.seqLock:
        kb.locks.seqLock.release()

    # If the url is stable and we did not set yet the match ratio and the
    # current injected value changes the url page content
    if conf.matchRatio is None:
        if conf.thold:
            conf.matchRatio = conf.thold

        elif kb.pageStable and ratio > 0.6 and ratio < 1:
            conf.matchRatio = ratio
            logger.debug("setting match ratio for current parameter to %.3f" % conf.matchRatio)

        elif not kb.pageStable or ( kb.pageStable and ratio < 0.6 ):
            conf.matchRatio = 0.900
            logger.debug("setting match ratio for current parameter to default value 0.900")

    # If it has been requested to return the ratio and not a comparison
    # response
    if getSeqMatcher:
        return ratio

    elif ratio == 1:
        return True

    # If the url is not stable it returns sequence matcher between the
    # first untouched HTTP response page content and this content
    else:
        return (ratio - conf.matchRatio) > ETA