# Copyright (C) 2015-2017 by the Free Software Foundation, Inc.
#
# This file is part of GNU Mailman.
#
# GNU Mailman 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 3 of the License, or (at your option)
# any later version.
#
# GNU Mailman 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
# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.

"""Common support between subscription and unsubscription."""

import uuid
import logging

from datetime import timedelta
from email.utils import formataddr
from enum import Enum
from mailman.core.i18n import _
from mailman.email.message import UserNotification
from mailman.interfaces.address import IAddress
from mailman.interfaces.bans import IBanManager
from mailman.interfaces.member import (AlreadySubscribedError, MemberRole,
                                       MembershipIsBannedError)
from mailman.interfaces.pending import IPendable, IPendings
from mailman.interfaces.subscriptions import (
    SubscriptionConfirmationNeededEvent, SubscriptionPendingError, TokenOwner)
from mailman.interfaces.template import ITemplateLoader
from mailman.interfaces.user import IUser
from mailman.interfaces.usermanager import IUserManager
from mailman.interfaces.workflows import (ISubscriptionWorkflow,
                                          IUnsubscriptionWorkflow, IWorkflow)
from mailman.utilities.datetime import now
from mailman.utilities.string import expand, wrap
from mailman.workflows.base import Workflow
from zope.component import getUtility
from zope.event import notify
from zope.interface import implementer
from zope.interface.exceptions import DoesNotImplement


log = logging.getLogger('mailman.subscribe')


class WhichSubscriber(Enum):
    address = 1
    user = 2


@implementer(IPendable)
class PendableSubscription(dict):
    PEND_TYPE = 'subscription'


@implementer(IPendable)
class PendableUnsubscription(dict):
    PEND_TYPE = 'unsubscription'


class SubscriptionWorkflowCommon(Workflow):
    """Common support between subscription and unsubscription."""

    def __init__(self, mlist, subscriber):
        super().__init__()
        self.mlist = mlist
        self.address = None
        self.user = None
        self.which = None
        self.member = None
        self._set_token(TokenOwner.no_one)
        # The subscriber must be either an IUser or IAddress.
        if IAddress.providedBy(subscriber):
            self.address = subscriber
            self.user = self.address.user
            self.which = WhichSubscriber.address
        elif IUser.providedBy(subscriber):
            self.address = subscriber.preferred_address
            self.user = subscriber
            self.which = WhichSubscriber.user
        self.subscriber = subscriber

    @property
    def user_key(self):
        # For save.
        return self.user.user_id.hex

    @user_key.setter
    def user_key(self, hex_key):
        # For restore.
        uid = uuid.UUID(hex_key)
        self.user = getUtility(IUserManager).get_user_by_id(uid)
        if self.user is None:
            self.user = self.address.user

    @property
    def address_key(self):
        # For save.
        return self.address.email

    @address_key.setter
    def address_key(self, email):
        # For restore.
        self.address = getUtility(IUserManager).get_address(email)
        assert self.address is not None

    @property
    def subscriber_key(self):
        return self.which.value

    @subscriber_key.setter
    def subscriber_key(self, key):
        self.which = WhichSubscriber(key)

    @property
    def token_owner_key(self):
        return self.token_owner.value

    @token_owner_key.setter
    def token_owner_key(self, value):
        self.token_owner = TokenOwner(value)

    def _set_token(self, token_owner):
        assert isinstance(token_owner, TokenOwner)
        pendings = getUtility(IPendings)
        # Clear out the previous pending token if there is one.
        if self.token is not None:
            pendings.confirm(self.token)
        # Create a new token to prevent replay attacks.  It seems like this
        # would produce the same token, but it won't because the pending adds a
        # bit of randomization.
        self.token_owner = token_owner
        if token_owner is TokenOwner.no_one:
            self.token = None
            return

        if ISubscriptionWorkflow.implementedBy(self.__class__):
            pendable_class = PendableSubscription
        elif IUnsubscriptionWorkflow.implementedBy(self.__class__):
            pendable_class = PendableUnsubscription
        else:
            raise DoesNotImplement(IWorkflow)

        pendable = pendable_class(
            list_id=self.mlist.list_id,
            email=self.address.email,
            display_name=self.address.display_name,
            when=now().replace(microsecond=0).isoformat(),
            token_owner=token_owner.name,
            )
        self.token = pendings.add(pendable, timedelta(days=3650))


class SubscriptionBase(SubscriptionWorkflowCommon):

    def _step_sanity_checks(self):
        # Ensure that we have both an address and a user, even if the address
        # is not verified.  We can't set the preferred address until it is
        # verified.
        if self.user is None:
            # The address has no linked user so create one, link it, and set
            # the user's preferred address.
            assert self.address is not None, 'No address or user'
            self.user = getUtility(IUserManager).make_user(self.address.email)
        if self.address is None:
            assert self.user.preferred_address is None, (
                "Preferred address exists, but wasn't used in constructor")
            addresses = list(self.user.addresses)
            if len(addresses) == 0:
                raise AssertionError('User has no addresses: {}'.format(
                    self.user))
            # This is rather arbitrary, but we have no choice.
            self.address = addresses[0]
        assert self.user is not None and self.address is not None, (
            'Insane sanity check results')
        # Is this subscriber already a member?
        if (self.which is WhichSubscriber.user and
                self.user.preferred_address is not None):
            subscriber = self.user
        else:
            subscriber = self.address
        if self.mlist.is_subscribed(subscriber):
            # 2017-04-22 BAW: This branch actually *does* get covered, as I've
            # verified by a full coverage run, but diffcov for some reason
            # claims that the test added in the branch that added this code
            # does not cover the change.  That seems like a bug in diffcov.
            raise AlreadySubscribedError(           # pragma: no cover
                self.mlist.fqdn_listname,
                self.address.email,
                MemberRole.member)
        # Is this email address banned?
        if IBanManager(self.mlist).is_banned(self.address.email):
            raise MembershipIsBannedError(self.mlist, self.address.email)
        # Check if there is already a subscription request for this email.
        pendings = getUtility(IPendings).find(
            mlist=self.mlist,
            pend_type='subscription')
        for token, pendable in pendings:
            if pendable['email'] == self.address.email:
                raise SubscriptionPendingError(self.mlist, self.address.email)
        # Start out with the subscriber being the token owner.

    def _step_do_subscription(self):
        # We can immediately subscribe the user to the mailing list.
        self.member = self.mlist.subscribe(self.subscriber)
        assert self.token is None and self.token_owner is TokenOwner.no_one, (
            'Unexpected active token at end of subscription workflow')


class RequestMixin:

    def _step_send_confirmation(self):
        self._set_token(TokenOwner.subscriber)
        self.push('do_confirm_verify')
        self.save()
        # Triggering this event causes the confirmation message to be sent.
        notify(SubscriptionConfirmationNeededEvent(
            self.mlist, self.token, self.address.email))
        # Now we wait for the confirmation.
        raise StopIteration

    def _step_do_confirm_verify(self):
        # Restore a little extra state that can't be stored in the database
        # (because the order of setattr() on restore is indeterminate), then
        # continue with the confirmation/verification step.
        if self.which is WhichSubscriber.address:
            self.subscriber = self.address
        else:
            assert self.which is WhichSubscriber.user
            self.subscriber = self.user
        # Reset the token so it can't be used in a replay attack.
        self._set_token(TokenOwner.no_one)
        # The user has confirmed their subscription request, and also verified
        # their email address if necessary.  This latter needs to be set on the
        # IAddress, but there's nothing more to do about the confirmation step.
        # We just continue along with the workflow.
        if self.address.verified_on is None:
            self.address.verified_on = now()
        self.verified = True
        self.confirmed = True


class VerificationMixin(RequestMixin):

    def __init__(self, pre_verified=False):
        self.verified = pre_verified

    def _step_verification_checks(self):
        # Is the address already verified, or is the pre-verified flag set?
        if self.address.verified_on is None:
            if self.verified:
                self.address.verified_on = now()
            else:
                # The address being subscribed is not yet verified, so we need
                # to send a validation email that will also confirm that the
                # user wants to be subscribed to this mailing list.
                self.push('send_confirmation')
                return


class ConfirmationMixin(RequestMixin):

    def __init__(self, pre_confirmed=False):
        self.confirmed = pre_confirmed

    def _step_confirmation_checks(self):
        # If the subscription has been pre-confirmed, then we can skip the
        # confirmation check can be skipped.
        if self.confirmed:
            return
        # The user must confirm their subscription.
        self.push('send_confirmation')


class ModerationMixin:

    def __init__(self, pre_approved=False):
        self.approved = pre_approved

    def _step_moderation_checks(self):
        # Does the moderator need to approve the subscription request?
        if self.approved:
            return
        # A moderator must confirm the subscription.
        self.push('get_moderator_approval')

    def _step_get_moderator_approval(self):
        # Here's the next step in the workflow, assuming the moderator
        # approves of the subscription.  If they don't, the workflow and
        # subscription request will just be thrown away.
        self._set_token(TokenOwner.moderator)
        self.push('subscribe_from_restored')
        self.save()
        log.info('{}: held subscription request from {}'.format(
            self.mlist.fqdn_listname, self.address.email))
        # Possibly send a notification to the list moderators.
        if self.mlist.admin_immed_notify:
            subject = _(
                'New subscription request to $self.mlist.display_name '
                'from $self.address.email')
            username = formataddr(
                (self.subscriber.display_name, self.address.email))
            template = getUtility(ITemplateLoader).get(
                'list:admin:action:subscribe', self.mlist)
            text = wrap(expand(template, self.mlist, dict(
                member=username,
                )))
            # This message should appear to come from the <list>-owner so as
            # to avoid any useless bounce processing.
            msg = UserNotification(
                self.mlist.owner_address, self.mlist.owner_address,
                subject, text, self.mlist.preferred_language)
            msg.send(self.mlist)
        # The workflow must stop running here.
        raise StopIteration

    def _step_subscribe_from_restored(self):
        # Prevent replay attacks.
        self._set_token(TokenOwner.no_one)
        # Restore a little extra state that can't be stored in the database
        # (because the order of setattr() on restore is indeterminate), then
        # subscribe the user.
        if self.which is WhichSubscriber.address:
            self.subscriber = self.address
        else:
            assert self.which is WhichSubscriber.user
            self.subscriber = self.user