#!/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 CONSTANT_RATIO
from lib.core.settings import DIFF_TOLERANCE

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 = CONSTANT_RATIO
            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

    elif conf.matchRatio is None:
        return None

    else:
        if conf.matchRatio == CONSTANT_RATIO or conf.thold:
            return ratio > conf.matchRatio
        else:
            return (ratio - conf.matchRatio) > DIFF_TOLERANCE