# Copyright (C) 2007-2014 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/>.

"""Implementations of the IPendable and IPending interfaces."""

from __future__ import absolute_import, print_function, unicode_literals

__metaclass__ = type
__all__ = [
    'Pended',
    'Pendings',
    ]


import time
import random
import hashlib

from lazr.config import as_timedelta
from storm.locals import DateTime, Int, RawStr, ReferenceSet, Unicode
from zope.interface import implementer
from zope.interface.verify import verifyObject

from mailman.config import config
from mailman.database.model import Model
from mailman.database.transaction import dbconnection
from mailman.interfaces.pending import (
    IPendable, IPended, IPendedKeyValue, IPendings)
from mailman.utilities.datetime import now
from mailman.utilities.modules import call_name



@implementer(IPendedKeyValue)
class PendedKeyValue(Model):
    """A pended key/value pair, tied to a token."""

    def __init__(self, key, value):
        self.key = key
        self.value = value

    id = Int(primary=True)
    key = Unicode()
    value = Unicode()
    pended_id = Int()



@implementer(IPended)
class Pended(Model):
    """A pended event, tied to a token."""

    def __init__(self, token, expiration_date):
        super(Pended, self).__init__()
        self.token = token
        self.expiration_date = expiration_date

    id = Int(primary=True)
    token = RawStr()
    expiration_date = DateTime()
    key_values = ReferenceSet(id, PendedKeyValue.pended_id)



@implementer(IPendable)
class UnpendedPendable(dict):
    pass



@implementer(IPendings)
class Pendings:
    """Implementation of the IPending interface."""

    @dbconnection
    def add(self, store, pendable, lifetime=None):
        verifyObject(IPendable, pendable)
        # Calculate the token and the lifetime.
        if lifetime is None:
            lifetime = as_timedelta(config.mailman.pending_request_life)
        # Calculate a unique token.  Algorithm vetted by the Timbot.  time()
        # has high resolution on Linux, clock() on Windows.  random gives us
        # about 45 bits in Python 2.2, 53 bits on Python 2.3.  The time and
        # clock values basically help obscure the random number generator, as
        # does the hash calculation.  The integral parts of the time values
        # are discarded because they're the most predictable bits.
        for attempts in range(3):
            right_now = time.time()
            x = random.random() + right_now % 1.0 + time.clock() % 1.0
            # Use sha1 because it produces shorter strings.
            token = hashlib.sha1(repr(x)).hexdigest()
            # In practice, we'll never get a duplicate, but we'll be anal
            # about checking anyway.
            if store.find(Pended, token=token).count() == 0:
                break
        else:
            raise AssertionError('Could not find a valid pendings token')
        # Create the record, and then the individual key/value pairs.
        pending = Pended(
            token=token,
            expiration_date=now() + lifetime)
        for key, value in pendable.items():
            if isinstance(key, str):
                key = unicode(key, 'utf-8')
            if isinstance(value, str):
                value = unicode(value, 'utf-8')
            elif type(value) is int:
                value = '__builtin__.int\1%s' % value
            elif type(value) is float:
                value = '__builtin__.float\1%s' % value
            elif type(value) is bool:
                value = '__builtin__.bool\1%s' % value
            elif type(value) is list:
                # We expect this to be a list of strings.
                value = ('mailman.model.pending.unpack_list\1' +
                         '\2'.join(value))
            keyval = PendedKeyValue(key=key, value=value)
            pending.key_values.add(keyval)
        store.add(pending)
        return token

    @dbconnection
    def confirm(self, store, token, expunge=True):
        # Token can come in as a unicode, but it's stored in the database as
        # bytes.  They must be ascii.
        pendings = store.find(Pended, token=str(token))
        if pendings.count() == 0:
            return None
        assert pendings.count() == 1, (
            'Unexpected token count: {0}'.format(pendings.count()))
        pending = pendings[0]
        pendable = UnpendedPendable()
        # Find all PendedKeyValue entries that are associated with the pending
        # object's ID.  Watch out for type conversions.
        for keyvalue in store.find(PendedKeyValue,
                                   PendedKeyValue.pended_id == pending.id):
            if keyvalue.value is not None and '\1' in keyvalue.value:
                type_name, value = keyvalue.value.split('\1', 1)
                pendable[keyvalue.key] = call_name(type_name, value)
            else:
                pendable[keyvalue.key] = keyvalue.value
            if expunge:
                store.remove(keyvalue)
        if expunge:
            store.remove(pending)
        return pendable

    @dbconnection
    def evict(self, store):
        right_now = now()
        for pending in store.find(Pended):
            if pending.expiration_date < right_now:
                # Find all PendedKeyValue entries that are associated with the
                # pending object's ID.
                q = store.find(PendedKeyValue,
                               PendedKeyValue.pended_id == pending.id)
                for keyvalue in q:
                    store.remove(keyvalue)
                store.remove(pending)



def unpack_list(value):
    return value.split('\2')
