# -*- coding: iso-8859-1 -*-
# Copyright (C) 2000-2005  Bastian Kleineidam
#
# 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., 675 Mass Ave, Cambridge, MA 02139, USA.
"""
Robots.txt parser.

The robots.txt Exclusion Protocol is implemented as specified in
http://www.robotstxt.org/wc/norobots-rfc.html
"""

import urlparse
import httplib
import urllib
import urllib2
import socket
import re
import sys
import zlib
import gzip
import cStringIO as StringIO
import linkcheck
import linkcheck.httplib2

__all__ = ["RobotFileParser"]

_debug = False

def _msg (prefix, msg):
    """
    Print given prefix and debug message to stderr if the _debug flag is
    set.

    @return: None
    """
    if _debug:
        print >> sys.stderr, prefix, msg

# methods for debug, warning and error messages
debug = lambda txt: _msg("debug:", txt)
warn = lambda txt: _msg("warning:", txt)
error = lambda txt: _msg("error:", txt)

class PasswordManager (object):
    """
    Simple password manager storing username and password. Suitable
    for use as an AuthHandler instance in urllib2.
    """

    def __init__ (self, user, password):
        """
        Store given username and password.
        """
        self.user = user
        self.password = password

    def add_password (self, realm, uri, user, passwd):
        """
        Does nothing since username and password are already stored.

        @return: None
        """
        pass

    def find_user_password (self, realm, authuri):
        """
        Get stored username and password.

        @return: A tuple (user, password)
        @rtype: tuple
        """
        return self.user, self.password


class RobotFileParser (object):
    """
    This class provides a set of methods to read, parse and answer
    questions about a single robots.txt file.
    """

    def __init__ (self, url='', user=None, password=None):
        """
        Initialize internal entry lists and store given url and
        credentials.
        """
        self.set_url(url)
        self.user = user
        self.password = password
        self._reset()

    def _reset (self):
        """
        Reset internal flags and entry lists.

        @return: None
        """
        self.entries = []
        self.default_entry = None
        self.disallow_all = False
        self.allow_all = False
        self.last_checked = 0

    def mtime (self):
        """
        Returns the time the robots.txt file was last fetched.

        This is useful for long-running web spiders that need to
        check for new robots.txt files periodically.

        @return: last modified in time.time() format
        @rtype: number
        """
        return self.last_checked

    def modified (self):
        """
        Sets the time the robots.txt file was last fetched to the
        current time.

        @return: None
        """
        import time
        self.last_checked = time.time()

    def set_url (self, url):
        """
        Sets the URL referring to a robots.txt file.

        @return: None
        """
        self.url = url
        self.host, self.path = urlparse.urlparse(url)[1:3]

    def get_opener (self):
        """
        Construct an URL opener object. It considers the given credentials
        from the __init__() method and supports proxies.

        @return: URL opener
        @rtype: urllib2.OpenerDirector
        """
        pwd_manager = PasswordManager(self.user, self.password)
        handlers = [
            urllib2.ProxyHandler(urllib.getproxies()),
            urllib2.UnknownHandler,
            HttpWithGzipHandler,
            urllib2.HTTPBasicAuthHandler(pwd_manager),
            urllib2.ProxyBasicAuthHandler(pwd_manager),
            urllib2.HTTPDigestAuthHandler(pwd_manager),
            urllib2.ProxyDigestAuthHandler(pwd_manager),
            urllib2.HTTPDefaultErrorHandler,
            urllib2.HTTPRedirectHandler,
        ]
        if hasattr(linkcheck.httplib2, 'HTTPS'):
            handlers.append(HttpsWithGzipHandler)
        return urllib2.build_opener(*handlers)

    def read (self):
        """
        Reads the robots.txt URL and feeds it to the parser.

        @return: None
        """
        self._reset()
        headers = {
            'User-Agent': 'Python RobotFileParser/2.1',
            'Accept-Encoding' : 'gzip;q=1.0, deflate;q=0.9, identity;q=0.5',
        }
        req = urllib2.Request(self.url, None, headers)
        try:
            f = self.get_opener().open(req)
        except urllib2.HTTPError, x:
            if x.code in (401, 403):
                self.disallow_all = True
                debug("robotst.txt disallow all")
            else:
                self.allow_all = True
                debug("robots.txt allow all")
            return
        except (socket.gaierror, socket.error, urllib2.URLError), x:
            # no network
            self.allow_all = True
            debug("robots.txt allow all")
            return
        except IOError, data:
            if data and data[0] == 'http error' and data[1] == 404:
                self.allow_all = True
                debug("robots.txt allow all")
            else:
                self.allow_all = True
                debug("robots.txt allow all")
            return
        except httplib.HTTPException:
            self.allow_all = True
            debug("robots.txt allow all")
            return
        lines = []
        line = f.readline()
        while line:
            lines.append(line.strip())
            line = f.readline()
        self.parse(lines)

    def _add_entry (self, entry):
        """
        Add a parsed entry to entry list.

        @return: None
        """
        if "*" in entry.useragents:
            # the default entry is considered last
            self.default_entry = entry
        else:
            self.entries.append(entry)

    def parse (self, lines):
        """
        Parse the input lines from a robot.txt file.
        We allow that a user-agent: line is not preceded by
        one or more blank lines.

        @return: None
        """
        debug("robots.txt parse lines")
        state = 0
        linenumber = 0
        entry = Entry()

        for line in lines:
            linenumber += 1
            if not line:
                if state == 1:
                    warn("line %d: you should insert"
                          " allow: or disallow: directives below any"
                          " user-agent: line" % linenumber)
                    entry = Entry()
                    state = 0
                elif state == 2:
                    self._add_entry(entry)
                    entry = Entry()
                    state = 0
            # remove optional comment and strip line
            i = line.find('#')
            if i >= 0:
                line = line[:i]
            line = line.strip()
            if not line:
                continue
            line = line.split(':', 1)
            if len(line) == 2:
                line[0] = line[0].strip().lower()
                line[1] = urllib.unquote(line[1].strip())
                if line[0] == "user-agent":
                    if state == 2:
                        warn("line %d: you should insert a blank"
                             " line before any user-agent"
                             " directive" % linenumber)
                        self._add_entry(entry)
                        entry = Entry()
                    entry.useragents.append(line[1])
                    state = 1
                elif line[0] == "disallow":
                    if state == 0:
                        error("line %d: you must insert a user-agent:"
                              " directive before this line" % linenumber)
                    else:
                        entry.rulelines.append(RuleLine(line[1], 0))
                        state = 2
                elif line[0] == "allow":
                    if state == 0:
                        error("line %d: you must insert a user-agent:"
                               " directive before this line" % linenumber)
                    else:
                        entry.rulelines.append(RuleLine(line[1], 1))
                else:
                    warn("line %d: unknown key %s" % (linenumber, line[0]))
            else:
                error("line %d: malformed line %s" % (linenumber, line))
        if state == 2:
            self.entries.append(entry)
        debug("Parsed rules:\n%s" % str(self))

    def can_fetch (self, useragent, url):
        """
        Using the parsed robots.txt decide if useragent can fetch url.

        @return: True if agent can fetch url, else False
        @rtype: bool
        """
        debug("Checking robot.txt allowance for:\n"\
              "  user agent: %r\n  url: %r" % (useragent, url))
        if not isinstance(useragent, str):
            useragent = useragent.encode("ascii", "ignore")
        if not isinstance(url, str):
            url = url.encode("ascii", "ignore")
        if self.disallow_all:
            return False
        if self.allow_all:
            return True
        # search for given user agent matches
        # the first match counts
        url = urllib.quote(urlparse.urlparse(urllib.unquote(url))[2]) or "/"
        for entry in self.entries:
            if entry.applies_to(useragent):
                return entry.allowance(url)
        # try the default entry last
        if self.default_entry is not None:
            return self.default_entry.allowance(url)
        # agent not found ==> access granted
        return True

    def __str__ (self):
        """
        Constructs string representation, usable as contents of a
        robots.txt file.

        @return: robots.txt format
        @rtype: string
        """
        lines = [str(entry) for entry in self.entries]
        if self.default_entry is not None:
            lines.append(str(self.default_entry))
        return "\n\n".join(lines)


class RuleLine (object):
    """
    A rule line is a single "Allow:" (allowance==1) or "Disallow:"
    (allowance==0) followed by a path.
    """

    def __init__ (self, path, allowance):
        """
        Initialize with given path and allowance info.
        """
        if path == '' and not allowance:
            # an empty value means allow all
            allowance = True
        self.path = urllib.quote(path)
        self.allowance = allowance

    def applies_to (self, path):
        """
        Look if given path applies to this rule.

        @return: True if pathname applies to this rule, else False
        @rtype: bool
        """
        return self.path == "*" or path.startswith(self.path)

    def __str__ (self):
        """
        Construct string representation in robots.txt format.

        @return: robots.txt format
        @rtype: string
        """
        return (self.allowance and "Allow" or "Disallow")+": "+self.path


class Entry (object):
    """
    An entry has one or more user-agents and zero or more rulelines.
    """

    def __init__ (self):
        """
        Initialize user agent and rule list.
        """
        self.useragents = []
        self.rulelines = []

    def __str__ (self):
        """
        string representation in robots.txt format.

        @return: robots.txt format
        @rtype: string
        """
        lines = ["User-agent: %r" % agent for agent in self.useragents]
        lines.extend([str(line) for line in self.rulelines])
        return "\n".join(lines)

    def applies_to (self, useragent):
        """
        Check if this entry applies to the specified agent.

        @return: True if this entry applies to the agent, else False.
        @rtype: bool
        """
        # split the name token and make it lower case
        if not useragent:
            return True
        useragent = useragent.split("/")[0].lower()
        for agent in self.useragents:
            if agent == '*':
                # we have the catch-all agent
                return True
            agent = agent.lower()
            if useragent in agent:
                return True
        return False

    def allowance (self, filename):
        """
        Preconditions:
        - our agent applies to this entry
        - filename is URL decoded

        Check if given filename is allowed to acces this entry.

        @return: True if allowed, else False
        @rtype: bool
        """
        for line in self.rulelines:
            debug("%s %s %s" % (filename, str(line), line.allowance))
            if line.applies_to(filename):
                return line.allowance
        return True

###########################################################################
# urlutils.py - Simplified urllib handling
#
#   Written by Chris Lawrence <lawrencc@debian.org>
#   (C) 1999-2002 Chris Lawrence
#
# This program is freely distributable per the following license:
#
##  Permission to use, copy, modify, and distribute this software and its
##  documentation for any purpose and without fee is hereby granted,
##  provided that the above copyright notice appears in all copies and that
##  both that copyright notice and this permission notice appear in
##  supporting documentation.
##
##  I DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
##  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL I
##  BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
##  DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
##  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
##  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
##  SOFTWARE.
def decode (page):
    """
    Gunzip or deflate a compressed page.
    """
    debug("robots.txt page info %s" % str(page.info()))
    encoding = page.info().get("Content-Encoding")
    if encoding in ('gzip', 'x-gzip', 'deflate'):
        # cannot seek in socket descriptors, so must get content now
        content = page.read()
        try:
            if encoding == 'deflate':
                fp = StringIO.StringIO(zlib.decompress(content))
            else:
                fp = gzip.GzipFile('', 'rb', 9, StringIO.StringIO(content))
        except zlib.error, msg:
            warn("uncompressing had error "\
                 "%s, assuming non-compressed content" % str(msg))
            fp = StringIO.StringIO(content)
        # remove content-encoding header
        headers = {}
        ceheader = re.compile(r"(?i)content-encoding:")
        for h in page.info().keys():
            if not ceheader.match(h):
                headers[h] = page.info()[h]
        newpage = urllib.addinfourl(fp, headers, page.geturl())
        if hasattr(page, "code"):
            # python 2.4 compatibility
            newpage.code = page.code
        if hasattr(page, "msg"):
            # python 2.4 compatibility
            newpage.msg = page.msg
        page = newpage
    return page


class HttpWithGzipHandler (urllib2.HTTPHandler):
    """
    Support gzip encoding.
    """
    def http_open (self, req):
        """
        Send request and decode answer.
        """
        return decode(urllib2.HTTPHandler.http_open(self, req))


if hasattr(linkcheck.httplib2, 'HTTPS'):
    class HttpsWithGzipHandler (urllib2.HTTPSHandler):
        """
        Support gzip encoding.
        """

        def http_open (self, req):
            """
            Send request and decode answer.
            """
            return decode(urllib2.HTTPSHandler.http_open(self, req))

# end of urlutils.py routines
###########################################################################