#!/usr/bin/env python
# -*- encoding: utf-8 -*-
'''
alias_resolver.py
=================
Classes for resolving postfix aliases.

:authors: Isis Agora Lovecruft
:version: 0.0.1-beta
:license: see included LICENSE file
:copyright: (c) 2013 Isis Agora Lovecruft

TODO:

    o Look into using twisted.protocols.postfix.policies classes for
      controlling concurrent connections and throttling resource consumption.
'''

import os
import uuid

try:
    from twisted.internet  import address, defer, reactor
    from twisted.mail      import maildir, alias
    from twisted.protocols import postfix
except ImportError:
    print "This software requires Twisted. Please see the README file"
    print "for instructions on getting required dependencies."

from leap.mx import couchdb
from leap.mx.util import net, log, config, exceptions


def createUUID(alias):
    """Creates Universal Unique ID by taking the SHA1 HASH of an email alias:

    >>> uuid.uuid5(uuid.NAMESPACE_URL, "isis@leap.se")
    UUID('7194878e-4aea-563f-85a4-4f58519f3c4f')

    TODO: Is there a commonly accepted way to check that an email address
          is valid?

    :param str alias: An email address alias.
    :returns: A :class:`uuid.UUID` containing attributes specifying the UUID.
    """
    return uuid.uuid5(uuid.NAMESPACE_URL, str(alias))


class DatabaseNotConnected(Exception):
    """Raised when not currently connected to a database."""

class StatusCodes(object):
    """
    The Postfix manual states:

        The request completion status is one of OK, RETRY, NOKEY (lookup
        failed because the key was not found), BAD (malformed request) or DENY
        (the table is not approved for proxy read or update access).

    Other SMTP codes: http://www.greenend.org.uk/rjk/tech/smtpreplies.html
    """
    OK    = "OK Others might say 'HELLA AWESOME'...but we're not convinced."
    RETRY = "RETRY Server is busy plotting revolution; requests might take a while."
    BAD   = "BAD bad Leroy Brown, baddest man in the whole...er. Malformed request."
    NOKEY = "NOKEY Couldn't find your keys, sorry. Did you check in the sofa?"
    DEFER = "DEFER_IF_LOCAL xxx fill me in"
    DENY  = "DENY no gurlz aloud in teh tree house."
    FAIL  = "FAIL xxx fill me in"

    fakeSMTPCodes = { '250': OK,
                      '300': RETRY,
                      '500': BAD,
                      '550': NOKEY,
                      '552': DEFER,
                      '553': DENY,
                      '554': FAIL, }

    def __init__(self, status_code=None):
        """xxx fill me in"""
        if status_code:
            self.get(status_code)

    def get(self, status_code=None)
        """xxx fill me in"""
        if status_code:
            if isinstance(status_code, str):
                return status_code, getattr(self, status_code.upper(), None)
            elif isinstance(status_code, int):
                for k, v in self.fake_smtp_codes.items():
                    ## we want to return None if it's 550
                    if k == str(status_code) and k != '550':
                        return status_code, v
                log.debug("%s" % self.NOKEY)
                return None, ''


class AliasResolver(postfix.PostfixTCPMapServer):
    """
    Resolve postfix aliases, similarly to using "$ postmap -q <alias>".

    This class starts a simple LineReceiver server which listens for a string
    specifying an alias to look up, :param:`key`, and which will be used to
    query the local Postfix server. You can test it with:

        $ ./alias_resolver.py &
        $ /usr/bin/postmap -q <key> tcp:localhost:1347

    Resources:
    http://www.postfix.org/proxymap.8.html
    https://www.iana.org/assignments/smtp-enhanced-status-codes/
    """
    def __init__(self, *args, **kwargs):
        """Create a server which listens for Postfix aliases to resolve."""
        super(postfix.PostfixTCPMapServer, self).__init__(*args, **kwargs)
        self.status_codes = StatusCodes()

    def sendCode(self, code, message=None):
        """Send an SMTP-like code with a message."""
        if not message:
            message = self.status_codes.get(code)
        self.sendLine('%3.3d %s' % (code, message or ''))

    def do_get(self, key):
        """Make a query to resolve an alias."""
        if key is None:
            self.sendCode(500)
            log.warn("Command 'get' takes one parameter.")
        else:
            d = defer.maybeDeferred(self.factory.get, key)
            d.addCallbacks(self._cbGot, self._cbNot)
            d.addErrback(log.err)

    @defer.inlineCallbacks
    def do_put(self, keyAndValue):
        """Add a key and value to the database, provided it does not exist."""
        if keyAndValue is None:
            self.sendCode(500)
            log.warn("Command 'put' takes two parameters.")
        else:
            try:
                key, value = keyAndValue.split(None, 1)
            except ValueError:
                self.sendCode(500)
                log.warn("Command 'put' takes two parameters.")
            else:
                alreadyThere = yield self.do_query(key)
                if alreadyThere is None:
                    d = defer.maybeDeferred(self.factory.put, key, value)
                    d.addCallbacks(self._cbPut, self._cbPout)
                    d.addCallbacks(log.err)
                else:
                    self.sendCode(553)

    @defer.inlineCallbacks
    def do_delete(self, key):
        """
        Delete an alias from the mapping database.

        xxx not sure if this is a good idea...
        """
        raise NotImplemented

    def check_recipient_access(self, key):
        """Make a query to resolve an alias."""
        self.do_get(self, key)

    def virtual_alias_map(self, key):
        """
        Get the Universal Unique ID for the alias address. If
        virtual_transport is True, then suffix the UUID with a domain.

        xxx I don't think we actually need couchdb for this, the UUID is an
        identifier, not an authenticator. And the SHA1 should always be the
        same, so unless it's considered to expensive to compute (less than
        querying a database, I would presume), it seems silly to do this.

        Instead, we should query CouchDB with the UUID to get the GPG keyid.
        """
        ## xxx need email address parser
        client_id = createUUID(key)

        if self.virtual_transport:
            return client.get_urn() + '@example.com'
        else: 
            return client.get_urn()

    def _cbGot(self, value):
        """Callback for self.get()"""
        if value is None:
            self.sendCode(550)
        else:
            self.sendCode(250, quote(value))

    def _cbNot(self, fail):
        """Errback for self.get()"""
        self.sendCode(554, fail.getErrorMessage())

    def _cbPut(self, value):
        """xxx fill me in"""
        pass

    def _cbPout(self, fail):
        """xxx fill me in"""
        pass


class AliasResolverFactory(postfix.PostfixTCPMapDeferringDictServerFactory):
    """
    A Factory for creating :class:`AliasResolver` servers, which handles inputs
    and outputs, and keeps an in-memory mapping of Postfix aliases in the form
    of a dictionary.

    xxx fill me in
    """
    protocol = AliasResolver

    def __init__(self, addr='127.0.0.1', port=4242, timeout=120, data=None):
        """
        Create a Factory which returns :class:`AliasResolver` servers.

        @param addr: A string giving the IP address of this server.
            Default: '127.0.0.1'
        @param port: An integer that specifies the port number to listen
            on. Default: 4242
        @param timeout: An integer specifying the number of seconds to wait
            until we should time out. Default: 120
        @param data: A dict to use to initialise or update the alias mapping.
        """
        super(postfix.PostfixTCPMapDeferringDictServerFactory,
              self).__init__(data=data)
        self.timeout = timeout
        self.noisy = True if config.advanced.noisy else False

        try:
            assert isinstance(port, int), "Port number must be an integer"
            assert isinstance(timeout, int), "Timeout must be an integer"
        except AssertionError, ae:
            raise SystemExit(ae.message)

        if net.checkIPaddress(addr):
            self.addr = address._IPAddress('TCP', addr, int(port))
        else:
            log.msg("Using default address: 127.0.0.1:%s" % port)
            self.addr = address._IPAddress('TCP', '127.0.0.1', int(port))

        log.msg("To configure Postfix to query this alias_resolver,")
        log.msg("you should do:")
        log.msg("    $ postconf -e 'check_recipient_access = tcp:%s:%d"
                % (addr, port))

    def buildProtocol(self):
        """
        Create an instance of the :class:`AliasResolver` server.
        """
        proto = self.protocol()
        proto.timeout = self.timeout
        proto.factory = self
        return proto

    def get(self, *args, **kwargs):
        """
        xxx connect me to the couchdb
        """
        pass

    def put(self, *args, **kwargs):
        """
        xxx connect me to the couchdb
        """
        pass


if __name__ == "__main__":

    print "To test alias_resolver.py, please use /test/test_alias_resolver.py"