from typing import Any, DefaultDict, Dict, List, Set, Tuple, TypeVar, Text, \
    Union, Optional, Sequence, AbstractSet, Pattern, AnyStr, Callable, Iterable
from typing.re import Match
from zerver.lib.str_utils import NonBinaryStr

from django.db import models
from django.db.models.query import QuerySet, F
from django.db.models import Manager, CASCADE, Sum
from django.db.models.functions import Length
from django.conf import settings
from django.contrib.auth.models import AbstractBaseUser, UserManager, \
    PermissionsMixin
import django.contrib.auth
from django.core.exceptions import ValidationError
from django.core.validators import URLValidator, MinLengthValidator, \
    RegexValidator
from django.dispatch import receiver
from zerver.lib.cache import cache_with_key, flush_user_profile, flush_realm, \
    user_profile_by_api_key_cache_key, \
    user_profile_by_id_cache_key, user_profile_by_email_cache_key, \
    user_profile_cache_key, generic_bulk_cached_fetch, cache_set, flush_stream, \
    display_recipient_cache_key, cache_delete, active_user_ids_cache_key, \
    get_stream_cache_key, realm_user_dicts_cache_key, \
    bot_dicts_in_realm_cache_key, realm_user_dict_fields, \
    bot_dict_fields, flush_message, bot_profile_cache_key
from zerver.lib.utils import make_safe_digest, generate_random_token
from django.db import transaction
from django.utils.timezone import now as timezone_now
from django.contrib.sessions.models import Session
from zerver.lib.timestamp import datetime_to_timestamp
from django.db.models.signals import pre_save, post_save, post_delete
from django.utils.translation import ugettext_lazy as _
from zerver.lib import cache
from zerver.lib.validator import check_int, check_float, check_string, \
    check_short_string
from zerver.lib.name_restrictions import is_disposable_domain
from zerver.lib.types import Validator

from django.utils.encoding import force_text

from bitfield import BitField
from bitfield.types import BitHandler
from collections import defaultdict, OrderedDict
from datetime import timedelta
import pylibmc
import re
import logging
import sre_constants
import time
import datetime
import sys

MAX_SUBJECT_LENGTH = 60
MAX_MESSAGE_LENGTH = 10000
MAX_LANGUAGE_ID_LENGTH = 50  # type: int

STREAM_NAMES = TypeVar('STREAM_NAMES', Sequence[Text], AbstractSet[Text])

def query_for_ids(query: QuerySet, user_ids: List[int], field: str) -> QuerySet:
    '''
    This function optimizes searches of the form
    `user_profile_id in (1, 2, 3, 4)` by quickly
    building the where clauses.  Profiling shows significant
    speedups over the normal Django-based approach.

    Use this very carefully!  Also, the caller should
    guard against empty lists of user_ids.
    '''
    assert(user_ids)
    value_list = ', '.join(str(int(user_id)) for user_id in user_ids)
    clause = '%s in (%s)' % (field, value_list)
    query = query.extra(
        where=[clause]
    )
    return query

# Doing 1000 remote cache requests to get_display_recipient is quite slow,
# so add a local cache as well as the remote cache cache.
per_request_display_recipient_cache = {}  # type: Dict[int, Union[Text, List[Dict[str, Any]]]]
def get_display_recipient_by_id(recipient_id: int, recipient_type: int,
                                recipient_type_id: Optional[int]) -> Union[Text, List[Dict[str, Any]]]:
    """
    returns: an object describing the recipient (using a cache).
    If the type is a stream, the type_id must be an int; a string is returned.
    Otherwise, type_id may be None; an array of recipient dicts is returned.
    """
    if recipient_id not in per_request_display_recipient_cache:
        result = get_display_recipient_remote_cache(recipient_id, recipient_type, recipient_type_id)
        per_request_display_recipient_cache[recipient_id] = result
    return per_request_display_recipient_cache[recipient_id]

def get_display_recipient(recipient: 'Recipient') -> Union[Text, List[Dict[str, Any]]]:
    return get_display_recipient_by_id(
        recipient.id,
        recipient.type,
        recipient.type_id
    )

def flush_per_request_caches() -> None:
    global per_request_display_recipient_cache
    per_request_display_recipient_cache = {}
    global per_request_realm_filters_cache
    per_request_realm_filters_cache = {}

DisplayRecipientCacheT = Union[Text, List[Dict[str, Any]]]
@cache_with_key(lambda *args: display_recipient_cache_key(args[0]),
                timeout=3600*24*7)
def get_display_recipient_remote_cache(recipient_id: int, recipient_type: int,
                                       recipient_type_id: Optional[int]) -> DisplayRecipientCacheT:
    """
    returns: an appropriate object describing the recipient.  For a
    stream this will be the stream name as a string.  For a huddle or
    personal, it will be an array of dicts about each recipient.
    """
    if recipient_type == Recipient.STREAM:
        assert recipient_type_id is not None
        stream = Stream.objects.get(id=recipient_type_id)
        return stream.name

    # The main priority for ordering here is being deterministic.
    # Right now, we order by ID, which matches the ordering of user
    # names in the left sidebar.
    user_profile_list = (UserProfile.objects.filter(subscription__recipient_id=recipient_id)
                                            .select_related()
                                            .order_by('id'))
    return [{'email': user_profile.email,
             'full_name': user_profile.full_name,
             'short_name': user_profile.short_name,
             'id': user_profile.id,
             'is_mirror_dummy': user_profile.is_mirror_dummy} for user_profile in user_profile_list]

def get_realm_emoji_cache_key(realm: 'Realm') -> Text:
    return u'realm_emoji:%s' % (realm.id,)

def get_active_realm_emoji_cache_key(realm: 'Realm') -> str:
    return u'active_realm_emoji:%s' % (realm.id,)

class Realm(models.Model):
    MAX_REALM_NAME_LENGTH = 40
    MAX_REALM_SUBDOMAIN_LENGTH = 40
    AUTHENTICATION_FLAGS = [u'Google', u'Email', u'GitHub', u'LDAP', u'Dev', u'RemoteUser']
    SUBDOMAIN_FOR_ROOT_DOMAIN = ''

    name = models.CharField(max_length=MAX_REALM_NAME_LENGTH, null=True)  # type: Optional[Text]
    string_id = models.CharField(max_length=MAX_REALM_SUBDOMAIN_LENGTH, unique=True)  # type: Text
    restricted_to_domain = models.BooleanField(default=False)  # type: bool
    invite_required = models.BooleanField(default=True)  # type: bool
    invite_by_admins_only = models.BooleanField(default=False)  # type: bool
    inline_image_preview = models.BooleanField(default=True)  # type: bool
    inline_url_embed_preview = models.BooleanField(default=True)  # type: bool
    create_stream_by_admins_only = models.BooleanField(default=False)  # type: bool
    add_emoji_by_admins_only = models.BooleanField(default=False)  # type: bool
    mandatory_topics = models.BooleanField(default=False)  # type: bool
    show_digest_email = models.BooleanField(default=True)  # type: bool
    name_changes_disabled = models.BooleanField(default=False)  # type: bool
    email_changes_disabled = models.BooleanField(default=False)  # type: bool
    disallow_disposable_email_addresses = models.BooleanField(default=True)  # type: bool
    description = models.TextField(null=True)  # type: Optional[Text]
    send_welcome_emails = models.BooleanField(default=True)  # type: bool

    allow_message_deleting = models.BooleanField(default=False)  # type: bool
    allow_message_editing = models.BooleanField(default=True)  # type: bool
    DEFAULT_MESSAGE_CONTENT_EDIT_LIMIT_SECONDS = 600  # if changed, also change in admin.js
    message_content_edit_limit_seconds = models.IntegerField(default=DEFAULT_MESSAGE_CONTENT_EDIT_LIMIT_SECONDS)  # type: int
    message_retention_days = models.IntegerField(null=True)  # type: Optional[int]
    allow_edit_history = models.BooleanField(default=True)  # type: bool
    DEFAULT_COMMUNITY_TOPIC_EDITING_LIMIT_SECONDS = 86400
    allow_community_topic_editing = models.BooleanField(default=False)  # type: bool

    # Valid org_types are {CORPORATE, COMMUNITY}
    CORPORATE = 1
    COMMUNITY = 2
    org_type = models.PositiveSmallIntegerField(default=CORPORATE)  # type: int

    # This value is also being used in static/js/settings_bots.bot_creation_policy_values.
    # On updating it here, update it there as well.
    BOT_CREATION_EVERYONE = 1
    BOT_CREATION_LIMIT_GENERIC_BOTS = 2
    BOT_CREATION_ADMINS_ONLY = 3
    bot_creation_policy = models.PositiveSmallIntegerField(default=BOT_CREATION_EVERYONE)  # type: int

    date_created = models.DateTimeField(default=timezone_now)  # type: datetime.datetime
    notifications_stream = models.ForeignKey('Stream', related_name='+', null=True, blank=True, on_delete=CASCADE)  # type: Optional[Stream]
    signup_notifications_stream = models.ForeignKey('Stream', related_name='+', null=True, blank=True, on_delete=CASCADE)  # type: Optional[Stream]
    deactivated = models.BooleanField(default=False)  # type: bool
    default_language = models.CharField(default=u'en', max_length=MAX_LANGUAGE_ID_LENGTH)  # type: Text
    authentication_methods = BitField(flags=AUTHENTICATION_FLAGS,
                                      default=2**31 - 1)  # type: BitHandler
    waiting_period_threshold = models.PositiveIntegerField(default=0)  # type: int
    _max_invites = models.IntegerField(null=True, db_column='max_invites')  # type: Optional[int]
    message_visibility_limit = models.IntegerField(null=True)  # type: Optional[int]
    # See upload_quota_bytes; don't interpret upload_quota_gb directly.
    upload_quota_gb = models.IntegerField(null=True)  # type: Optional[int]

    # Define the types of the various automatically managed properties
    property_types = dict(
        add_emoji_by_admins_only=bool,
        allow_edit_history=bool,
        allow_message_deleting=bool,
        bot_creation_policy=int,
        create_stream_by_admins_only=bool,
        default_language=Text,
        description=Text,
        disallow_disposable_email_addresses=bool,
        email_changes_disabled=bool,
        invite_required=bool,
        invite_by_admins_only=bool,
        inline_image_preview=bool,
        inline_url_embed_preview=bool,
        mandatory_topics=bool,
        message_retention_days=(int, type(None)),
        name=Text,
        name_changes_disabled=bool,
        restricted_to_domain=bool,
        send_welcome_emails=bool,
        waiting_period_threshold=int,
    )  # type: Dict[str, Union[type, Tuple[type, ...]]]

    ICON_FROM_GRAVATAR = u'G'
    ICON_UPLOADED = u'U'
    ICON_SOURCES = (
        (ICON_FROM_GRAVATAR, 'Hosted by Gravatar'),
        (ICON_UPLOADED, 'Uploaded by administrator'),
    )
    icon_source = models.CharField(default=ICON_FROM_GRAVATAR, choices=ICON_SOURCES,
                                   max_length=1)  # type: Text
    icon_version = models.PositiveSmallIntegerField(default=1)  # type: int

    DEFAULT_NOTIFICATION_STREAM_NAME = u'announce'
    INITIAL_PRIVATE_STREAM_NAME = u'core team'

    BOT_CREATION_POLICY_TYPES = [
        BOT_CREATION_EVERYONE,
        BOT_CREATION_LIMIT_GENERIC_BOTS,
        BOT_CREATION_ADMINS_ONLY,
    ]

    def authentication_methods_dict(self) -> Dict[Text, bool]:
        """Returns the a mapping from authentication flags to their status,
        showing only those authentication flags that are supported on
        the current server (i.e. if EmailAuthBackend is not configured
        on the server, this will not return an entry for "Email")."""
        # This mapping needs to be imported from here due to the cyclic
        # dependency.
        from zproject.backends import AUTH_BACKEND_NAME_MAP

        ret = {}  # type: Dict[Text, bool]
        supported_backends = {backend.__class__ for backend in django.contrib.auth.get_backends()}
        for k, v in self.authentication_methods.iteritems():
            backend = AUTH_BACKEND_NAME_MAP[k]
            if backend in supported_backends:
                ret[k] = v
        return ret

    def __str__(self) -> Text:
        return "<Realm: %s %s>" % (self.string_id, self.id)

    @cache_with_key(get_realm_emoji_cache_key, timeout=3600*24*7)
    def get_emoji(self) -> Dict[Text, Dict[str, Iterable[Text]]]:
        return get_realm_emoji_uncached(self)

    @cache_with_key(get_active_realm_emoji_cache_key, timeout=3600*24*7)
    def get_active_emoji(self) -> Dict[str, Dict[str, Iterable[str]]]:
        return get_active_realm_emoji_uncached(self)

    def get_admin_users(self) -> Sequence['UserProfile']:
        # TODO: Change return type to QuerySet[UserProfile]
        return UserProfile.objects.filter(realm=self, is_realm_admin=True,
                                          is_active=True)

    def get_active_users(self) -> Sequence['UserProfile']:
        # TODO: Change return type to QuerySet[UserProfile]
        return UserProfile.objects.filter(realm=self, is_active=True).select_related()

    def get_bot_domain(self) -> str:
        # Remove the port. Mainly needed for development environment.
        return self.host.split(':')[0]

    def get_notifications_stream(self) -> Optional['Stream']:
        if self.notifications_stream is not None and not self.notifications_stream.deactivated:
            return self.notifications_stream
        return None

    def get_signup_notifications_stream(self) -> Optional['Stream']:
        if self.signup_notifications_stream is not None and not self.signup_notifications_stream.deactivated:
            return self.signup_notifications_stream
        return None

    @property
    def max_invites(self) -> int:
        if self._max_invites is None:
            return settings.INVITES_DEFAULT_REALM_DAILY_MAX
        return self._max_invites

    @max_invites.setter
    def max_invites(self, value: int) -> None:
        self._max_invites = value

    def upload_quota_bytes(self) -> Optional[int]:
        if self.upload_quota_gb is None:
            return None
        # We describe the quota to users in "GB" or "gigabytes", but actually apply
        # it as gibibytes (GiB) to be a bit more generous in case of confusion.
        return self.upload_quota_gb << 30

    @property
    def subdomain(self) -> Text:
        return self.string_id

    @property
    def display_subdomain(self) -> Text:
        """Likely to be temporary function to avoid signup messages being sent
        to an empty topic"""
        if self.string_id == "":
            return "."
        return self.string_id

    @property
    def uri(self) -> str:
        return settings.EXTERNAL_URI_SCHEME + self.host

    @property
    def host(self) -> str:
        return self.host_for_subdomain(self.subdomain)

    @staticmethod
    def host_for_subdomain(subdomain: str) -> str:
        if subdomain == Realm.SUBDOMAIN_FOR_ROOT_DOMAIN:
            return settings.EXTERNAL_HOST
        default_host = "%s.%s" % (subdomain, settings.EXTERNAL_HOST)
        return settings.REALM_HOSTS.get(subdomain, default_host)

    @property
    def is_zephyr_mirror_realm(self) -> bool:
        return self.string_id == "zephyr"

    @property
    def webathena_enabled(self) -> bool:
        return self.is_zephyr_mirror_realm

    @property
    def presence_disabled(self) -> bool:
        return self.is_zephyr_mirror_realm

    class Meta:
        permissions = (
            ('administer', "Administer a realm"),
            ('api_super_user', "Can send messages as other users for mirroring"),
        )

post_save.connect(flush_realm, sender=Realm)

def get_realm(string_id: Text) -> Realm:
    return Realm.objects.filter(string_id=string_id).first()

def name_changes_disabled(realm: Optional[Realm]) -> bool:
    if realm is None:
        return settings.NAME_CHANGES_DISABLED
    return settings.NAME_CHANGES_DISABLED or realm.name_changes_disabled

class RealmDomain(models.Model):
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm
    # should always be stored lowercase
    domain = models.CharField(max_length=80, db_index=True)  # type: Text
    allow_subdomains = models.BooleanField(default=False)

    class Meta:
        unique_together = ("realm", "domain")

# These functions should only be used on email addresses that have
# been validated via django.core.validators.validate_email
#
# Note that we need to use some care, since can you have multiple @-signs; e.g.
# "tabbott@test"@zulip.com
# is valid email address
def email_to_username(email: Text) -> Text:
    return "@".join(email.split("@")[:-1]).lower()

# Returns the raw domain portion of the desired email address
def email_to_domain(email: Text) -> Text:
    return email.split("@")[-1].lower()

class DomainNotAllowedForRealmError(Exception):
    pass

class DisposableEmailError(Exception):
    pass

# Is a user with the given email address allowed to be in the given realm?
# (This function does not check whether the user has been invited to the realm.
# So for invite-only realms, this is the test for whether a user can be invited,
# not whether the user can sign up currently.)
def email_allowed_for_realm(email: Text, realm: Realm) -> None:
    if not realm.restricted_to_domain:
        if realm.disallow_disposable_email_addresses and \
                is_disposable_domain(email_to_domain(email)):
            raise DisposableEmailError
        return

    domain = email_to_domain(email)
    query = RealmDomain.objects.filter(realm=realm)
    if query.filter(domain=domain).exists():
        return
    else:
        query = query.filter(allow_subdomains=True)
        while len(domain) > 0:
            subdomain, sep, domain = domain.partition('.')
            if query.filter(domain=domain).exists():
                return
    raise DomainNotAllowedForRealmError

def get_realm_domains(realm: Realm) -> List[Dict[str, Text]]:
    return list(realm.realmdomain_set.values('domain', 'allow_subdomains'))

class RealmEmoji(models.Model):
    author = models.ForeignKey('UserProfile', blank=True, null=True, on_delete=CASCADE)
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm
    # Second part of the regex (negative lookbehind) disallows names ending with
    # one of the punctuation characters
    name = models.TextField(validators=[MinLengthValidator(1),
                                        RegexValidator(regex=r'^[0-9a-z.\-_]+(?<![.\-_])$',
                                                       message=_("Invalid characters in emoji name"))])  # type: Text
    file_name = models.TextField(db_index=True, null=True, blank=True)  # type: Optional[Text]
    deactivated = models.BooleanField(default=False)  # type: bool

    PATH_ID_TEMPLATE = "{realm_id}/emoji/images/{emoji_file_name}"

    def __str__(self) -> Text:
        return "<RealmEmoji(%s): %s %s %s %s>" % (self.realm.string_id,
                                                  self.id,
                                                  self.name,
                                                  self.deactivated,
                                                  self.file_name)

def get_realm_emoji_dicts(realm: Realm,
                          only_active_emojis: bool=False) -> Dict[str, Dict[str, Any]]:
    query = RealmEmoji.objects.filter(realm=realm).select_related('author')
    if only_active_emojis:
        query = query.filter(deactivated=False)
    d = {}
    from zerver.lib.emoji import get_emoji_url

    for realm_emoji in query.all():
        author = None
        if realm_emoji.author:
            author = {
                'id': realm_emoji.author.id,
                'email': realm_emoji.author.email,
                'full_name': realm_emoji.author.full_name}
        emoji_url = get_emoji_url(realm_emoji.file_name, realm_emoji.realm_id)
        d[str(realm_emoji.id)] = dict(id=str(realm_emoji.id),
                                      name=realm_emoji.name,
                                      source_url=emoji_url,
                                      deactivated=realm_emoji.deactivated,
                                      author=author)
    return d

def get_realm_emoji_uncached(realm: Realm) -> Dict[str, Dict[str, Any]]:
    return get_realm_emoji_dicts(realm)

def get_active_realm_emoji_uncached(realm: Realm) -> Dict[str, Dict[str, Any]]:
    realm_emojis = get_realm_emoji_dicts(realm, only_active_emojis=True)
    d = {}
    for emoji_id, emoji_dict in realm_emojis.items():
        d[emoji_dict['name']] = emoji_dict
    return d

def flush_realm_emoji(sender: Any, **kwargs: Any) -> None:
    realm = kwargs['instance'].realm
    cache_set(get_realm_emoji_cache_key(realm),
              get_realm_emoji_uncached(realm),
              timeout=3600*24*7)
    cache_set(get_active_realm_emoji_cache_key(realm),
              get_active_realm_emoji_uncached(realm),
              timeout=3600*24*7)

post_save.connect(flush_realm_emoji, sender=RealmEmoji)
post_delete.connect(flush_realm_emoji, sender=RealmEmoji)

def filter_pattern_validator(value: Text) -> None:
    regex = re.compile(r'(?:[\w\-#]*)(\(\?P<\w+>.+\))')
    error_msg = 'Invalid filter pattern, you must use the following format OPTIONAL_PREFIX(?P<id>.+)'

    if not regex.match(str(value)):
        raise ValidationError(error_msg)

    try:
        re.compile(value)
    except sre_constants.error:
        # Regex is invalid
        raise ValidationError(error_msg)

def filter_format_validator(value: str) -> None:
    regex = re.compile(r'^[\.\/:a-zA-Z0-9_?=-]+%\(([a-zA-Z0-9_-]+)\)s[a-zA-Z0-9_-]*$')

    if not regex.match(value):
        raise ValidationError('URL format string must be in the following format: '
                              '`https://example.com/%(\w+)s`')

class RealmFilter(models.Model):
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm
    pattern = models.TextField(validators=[filter_pattern_validator])  # type: Text
    url_format_string = models.TextField(validators=[URLValidator(), filter_format_validator])  # type: Text

    class Meta:
        unique_together = ("realm", "pattern")

    def __str__(self) -> Text:
        return "<RealmFilter(%s): %s %s>" % (self.realm.string_id, self.pattern, self.url_format_string)

def get_realm_filters_cache_key(realm_id: int) -> Text:
    return u'%s:all_realm_filters:%s' % (cache.KEY_PREFIX, realm_id,)

# We have a per-process cache to avoid doing 1000 remote cache queries during page load
per_request_realm_filters_cache = {}  # type: Dict[int, List[Tuple[Text, Text, int]]]

def realm_in_local_realm_filters_cache(realm_id: int) -> bool:
    return realm_id in per_request_realm_filters_cache

def realm_filters_for_realm(realm_id: int) -> List[Tuple[Text, Text, int]]:
    if not realm_in_local_realm_filters_cache(realm_id):
        per_request_realm_filters_cache[realm_id] = realm_filters_for_realm_remote_cache(realm_id)
    return per_request_realm_filters_cache[realm_id]

@cache_with_key(get_realm_filters_cache_key, timeout=3600*24*7)
def realm_filters_for_realm_remote_cache(realm_id: int) -> List[Tuple[Text, Text, int]]:
    filters = []
    for realm_filter in RealmFilter.objects.filter(realm_id=realm_id):
        filters.append((realm_filter.pattern, realm_filter.url_format_string, realm_filter.id))

    return filters

def all_realm_filters() -> Dict[int, List[Tuple[Text, Text, int]]]:
    filters = defaultdict(list)  # type: DefaultDict[int, List[Tuple[Text, Text, int]]]
    for realm_filter in RealmFilter.objects.all():
        filters[realm_filter.realm_id].append((realm_filter.pattern,
                                               realm_filter.url_format_string,
                                               realm_filter.id))

    return filters

def flush_realm_filter(sender: Any, **kwargs: Any) -> None:
    realm_id = kwargs['instance'].realm_id
    cache_delete(get_realm_filters_cache_key(realm_id))
    try:
        per_request_realm_filters_cache.pop(realm_id)
    except KeyError:
        pass

post_save.connect(flush_realm_filter, sender=RealmFilter)
post_delete.connect(flush_realm_filter, sender=RealmFilter)

class UserProfile(AbstractBaseUser, PermissionsMixin):
    DEFAULT_BOT = 1
    """
    Incoming webhook bots are limited to only sending messages via webhooks.
    Thus, it is less of a security risk to expose their API keys to third-party services,
    since they can't be used to read messages.
    """
    INCOMING_WEBHOOK_BOT = 2
    # This value is also being used in static/js/settings_bots.js.
    # On updating it here, update it there as well.
    OUTGOING_WEBHOOK_BOT = 3
    """
    Embedded bots run within the Zulip server itself; events are added to the
    embedded_bots queue and then handled by a QueueProcessingWorker.
    """
    EMBEDDED_BOT = 4

    BOT_TYPES = {
        DEFAULT_BOT: 'Generic bot',
        INCOMING_WEBHOOK_BOT: 'Incoming webhook',
        OUTGOING_WEBHOOK_BOT: 'Outgoing webhook',
        EMBEDDED_BOT: 'Embedded bot',
    }

    SERVICE_BOT_TYPES = [
        OUTGOING_WEBHOOK_BOT,
        EMBEDDED_BOT,
    ]

    # Fields from models.AbstractUser minus last_name and first_name,
    # which we don't use; email is modified to make it indexed and unique.
    email = models.EmailField(blank=False, db_index=True)  # type: Text
    is_staff = models.BooleanField(default=False)  # type: bool
    is_active = models.BooleanField(default=True, db_index=True)  # type: bool
    is_realm_admin = models.BooleanField(default=False, db_index=True)  # type: bool
    is_bot = models.BooleanField(default=False, db_index=True)  # type: bool
    bot_type = models.PositiveSmallIntegerField(null=True, db_index=True)  # type: Optional[int]
    is_api_super_user = models.BooleanField(default=False, db_index=True)  # type: bool
    date_joined = models.DateTimeField(default=timezone_now)  # type: datetime.datetime
    is_mirror_dummy = models.BooleanField(default=False)  # type: bool
    bot_owner = models.ForeignKey('self', null=True, on_delete=models.SET_NULL)  # type: Optional[UserProfile]
    long_term_idle = models.BooleanField(default=False, db_index=True)  # type: bool

    USERNAME_FIELD = 'email'
    MAX_NAME_LENGTH = 100
    MIN_NAME_LENGTH = 2
    API_KEY_LENGTH = 32
    NAME_INVALID_CHARS = ['*', '`', '>', '"', '@']

    # Our custom site-specific fields
    full_name = models.CharField(max_length=MAX_NAME_LENGTH)  # type: Text
    short_name = models.CharField(max_length=MAX_NAME_LENGTH)  # type: Text
    # pointer points to Message.id, NOT UserMessage.id.
    pointer = models.IntegerField()  # type: int
    last_pointer_updater = models.CharField(max_length=64)  # type: Text
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm
    api_key = models.CharField(max_length=API_KEY_LENGTH)  # type: Text
    tos_version = models.CharField(null=True, max_length=10)  # type: Optional[Text]
    last_active_message_id = models.IntegerField(null=True)  # type: Optional[int]

    ### Notifications settings. ###

    # Stream notifications.
    enable_stream_desktop_notifications = models.BooleanField(default=False)  # type: bool
    enable_stream_email_notifications = models.BooleanField(default=False)  # type: bool
    enable_stream_push_notifications = models.BooleanField(default=False)  # type: bool
    enable_stream_sounds = models.BooleanField(default=False)  # type: bool

    # PM + @-mention notifications.
    enable_desktop_notifications = models.BooleanField(default=True)  # type: bool
    pm_content_in_desktop_notifications = models.BooleanField(default=True)  # type: bool
    enable_sounds = models.BooleanField(default=True)  # type: bool
    enable_offline_email_notifications = models.BooleanField(default=True)  # type: bool
    message_content_in_email_notifications = models.BooleanField(default=True)  # type: bool
    enable_offline_push_notifications = models.BooleanField(default=True)  # type: bool
    enable_online_push_notifications = models.BooleanField(default=False)  # type: bool

    enable_digest_emails = models.BooleanField(default=True)  # type: bool
    realm_name_in_notifications = models.BooleanField(default=False)  # type: bool

    # Old notification field superseded by existence of stream notification
    # settings.
    default_desktop_notifications = models.BooleanField(default=True)  # type: bool

    ###

    last_reminder = models.DateTimeField(default=timezone_now, null=True)  # type: Optional[datetime.datetime]
    rate_limits = models.CharField(default=u"", max_length=100)  # type: Text # comma-separated list of range:max pairs

    # Default streams
    default_sending_stream = models.ForeignKey('zerver.Stream', null=True, related_name='+', on_delete=CASCADE)  # type: Optional[Stream]
    default_events_register_stream = models.ForeignKey('zerver.Stream', null=True, related_name='+', on_delete=CASCADE)  # type: Optional[Stream]
    default_all_public_streams = models.BooleanField(default=False)  # type: bool

    # UI vars
    enter_sends = models.NullBooleanField(default=False)  # type: Optional[bool]
    left_side_userlist = models.BooleanField(default=False)  # type: bool

    # display settings
    twenty_four_hour_time = models.BooleanField(default=False)  # type: bool
    default_language = models.CharField(default=u'en', max_length=MAX_LANGUAGE_ID_LENGTH)  # type: Text
    high_contrast_mode = models.BooleanField(default=False)  # type: bool
    night_mode = models.BooleanField(default=False)  # type: bool
    translate_emoticons = models.BooleanField(default=False)  # type: bool

    # Hours to wait before sending another email to a user
    EMAIL_REMINDER_WAITPERIOD = 24
    # Minutes to wait before warning a bot owner that their bot sent a message
    # to a nonexistent stream
    BOT_OWNER_STREAM_ALERT_WAITPERIOD = 1

    AVATAR_FROM_GRAVATAR = u'G'
    AVATAR_FROM_USER = u'U'
    AVATAR_SOURCES = (
        (AVATAR_FROM_GRAVATAR, 'Hosted by Gravatar'),
        (AVATAR_FROM_USER, 'Uploaded by user'),
    )
    avatar_source = models.CharField(default=AVATAR_FROM_GRAVATAR, choices=AVATAR_SOURCES, max_length=1)  # type: Text
    avatar_version = models.PositiveSmallIntegerField(default=1)  # type: int

    TUTORIAL_WAITING  = u'W'
    TUTORIAL_STARTED  = u'S'
    TUTORIAL_FINISHED = u'F'
    TUTORIAL_STATES   = ((TUTORIAL_WAITING, "Waiting"),
                         (TUTORIAL_STARTED, "Started"),
                         (TUTORIAL_FINISHED, "Finished"))

    tutorial_status = models.CharField(default=TUTORIAL_WAITING, choices=TUTORIAL_STATES, max_length=1)  # type: Text
    # Contains serialized JSON of the form:
    #    [("step 1", true), ("step 2", false)]
    # where the second element of each tuple is if the step has been
    # completed.
    onboarding_steps = models.TextField(default=u'[]')  # type: Text

    alert_words = models.TextField(default=u'[]')  # type: Text # json-serialized list of strings

    objects = UserManager()  # type: UserManager
    # The maximum length of a timezone in pytz.all_timezones is 32.
    # Setting max_length=40 is a safe choice.
    # In Django, the convention is to use empty string instead of Null
    # for text based fields. For more information, see
    # https://docs.djangoproject.com/en/1.10/ref/models/fields/#django.db.models.Field.null.
    timezone = models.CharField(max_length=40, default=u'')  # type: Text

    # Emojisets
    APPLE_EMOJISET      = u'apple'
    EMOJIONE_EMOJISET   = u'emojione'
    GOOGLE_EMOJISET     = u'google'
    TWITTER_EMOJISET    = u'twitter'
    TEXT_EMOJISET       = u'text'
    EMOJISET_CHOICES    = ((GOOGLE_EMOJISET, "Google"),
                           (APPLE_EMOJISET, "Apple"),
                           (TWITTER_EMOJISET, "Twitter"),
                           (EMOJIONE_EMOJISET, "EmojiOne"),
                           (TEXT_EMOJISET, "Plain text"))
    emojiset = models.CharField(default=GOOGLE_EMOJISET, choices=EMOJISET_CHOICES, max_length=20)  # type: Text

    # Define the types of the various automatically managed properties
    property_types = dict(
        default_language=Text,
        emojiset=Text,
        left_side_userlist=bool,
        timezone=Text,
        twenty_four_hour_time=bool,
        high_contrast_mode=bool,
        night_mode=bool,
        translate_emoticons=bool,
    )

    notification_setting_types = dict(
        enable_desktop_notifications=bool,
        enable_digest_emails=bool,
        enable_offline_email_notifications=bool,
        enable_offline_push_notifications=bool,
        enable_online_push_notifications=bool,
        enable_sounds=bool,
        enable_stream_desktop_notifications=bool,
        enable_stream_email_notifications=bool,
        enable_stream_push_notifications=bool,
        enable_stream_sounds=bool,
        message_content_in_email_notifications=bool,
        pm_content_in_desktop_notifications=bool,
        realm_name_in_notifications=bool,
    )

    class Meta:
        unique_together = (('realm', 'email'),)

    @property
    def profile_data(self) -> List[Dict[str, Union[int, float, Text]]]:
        values = CustomProfileFieldValue.objects.filter(user_profile=self)
        user_data = {v.field_id: v.value for v in values}
        data = []  # type: List[Dict[str, Union[int, float, Text]]]
        for field in custom_profile_fields_for_realm(self.realm_id):
            value = user_data.get(field.id, None)
            field_type = field.field_type
            if value is not None:
                converter = field.FIELD_CONVERTERS[field_type]
                value = converter(value)

            field_data = {}  # type: Dict[str, Union[int, float, Text]]
            for k, v in field.as_dict().items():
                field_data[k] = v
            field_data['value'] = value
            data.append(field_data)

        return data

    def can_admin_user(self, target_user: 'UserProfile') -> bool:
        """Returns whether this user has permission to modify target_user"""
        if target_user.bot_owner == self:
            return True
        elif self.is_realm_admin and self.realm == target_user.realm:
            return True
        else:
            return False

    def __str__(self) -> Text:
        return "<UserProfile: %s %s>" % (self.email, self.realm)

    @property
    def is_incoming_webhook(self) -> bool:
        return self.bot_type == UserProfile.INCOMING_WEBHOOK_BOT

    @property
    def allowed_bot_types(self) -> List[int]:
        allowed_bot_types = []
        if self.is_realm_admin or \
                not self.realm.bot_creation_policy == Realm.BOT_CREATION_LIMIT_GENERIC_BOTS:
            allowed_bot_types.append(UserProfile.DEFAULT_BOT)
        allowed_bot_types += [
            UserProfile.INCOMING_WEBHOOK_BOT,
            UserProfile.OUTGOING_WEBHOOK_BOT,
        ]
        if settings.EMBEDDED_BOTS_ENABLED:
            allowed_bot_types.append(UserProfile.EMBEDDED_BOT)
        return allowed_bot_types

    @staticmethod
    def emojiset_choices() -> Dict[Text, Text]:
        return OrderedDict((emojiset[0], emojiset[1]) for emojiset in UserProfile.EMOJISET_CHOICES)

    @staticmethod
    def emails_from_ids(user_ids: Sequence[int]) -> Dict[int, Text]:
        rows = UserProfile.objects.filter(id__in=user_ids).values('id', 'email')
        return {row['id']: row['email'] for row in rows}

    def can_create_streams(self) -> bool:
        diff = (timezone_now() - self.date_joined).days
        if self.is_realm_admin:
            return True
        elif self.realm.create_stream_by_admins_only:
            return False
        if diff >= self.realm.waiting_period_threshold:
            return True
        return False

    def major_tos_version(self) -> int:
        if self.tos_version is not None:
            return int(self.tos_version.split('.')[0])
        else:
            return -1

class UserGroup(models.Model):
    name = models.CharField(max_length=100)
    members = models.ManyToManyField(UserProfile, through='UserGroupMembership')
    realm = models.ForeignKey(Realm, on_delete=CASCADE)
    description = models.TextField(default=u'')  # type: Text

    class Meta:
        unique_together = (('realm', 'name'),)

class UserGroupMembership(models.Model):
    user_group = models.ForeignKey(UserGroup, on_delete=CASCADE)
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)

    class Meta:
        unique_together = (('user_group', 'user_profile'),)

def receives_offline_push_notifications(user_profile: UserProfile) -> bool:
    return (user_profile.enable_offline_push_notifications and
            not user_profile.is_bot)

def receives_offline_email_notifications(user_profile: UserProfile) -> bool:
    return (user_profile.enable_offline_email_notifications and
            not user_profile.is_bot)

def receives_online_notifications(user_profile: UserProfile) -> bool:
    return (user_profile.enable_online_push_notifications and
            not user_profile.is_bot)

def receives_stream_notifications(user_profile: UserProfile) -> bool:
    return (user_profile.enable_stream_push_notifications and
            not user_profile.is_bot)

def remote_user_to_email(remote_user: Text) -> Text:
    if settings.SSO_APPEND_DOMAIN is not None:
        remote_user += "@" + settings.SSO_APPEND_DOMAIN
    return remote_user

# Make sure we flush the UserProfile object from our remote cache
# whenever we save it.
post_save.connect(flush_user_profile, sender=UserProfile)

class PreregistrationUser(models.Model):
    email = models.EmailField()  # type: Text
    referred_by = models.ForeignKey(UserProfile, null=True, on_delete=CASCADE)  # Optional[UserProfile]
    streams = models.ManyToManyField('Stream')  # type: Manager
    invited_at = models.DateTimeField(auto_now=True)  # type: datetime.datetime
    realm_creation = models.BooleanField(default=False)
    # Indicates whether the user needs a password.  Users who were
    # created via SSO style auth (e.g. GitHub/Google) generally do not.
    password_required = models.BooleanField(default=True)

    # status: whether an object has been confirmed.
    #   if confirmed, set to confirmation.settings.STATUS_ACTIVE
    status = models.IntegerField(default=0)  # type: int

    realm = models.ForeignKey(Realm, null=True, on_delete=CASCADE)  # type: Optional[Realm]

    invited_as_admin = models.BooleanField(default=False)  # type: Optional[bool]

class MultiuseInvite(models.Model):
    referred_by = models.ForeignKey(UserProfile, on_delete=CASCADE)  # Optional[UserProfile]
    streams = models.ManyToManyField('Stream')  # type: Manager
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm

class EmailChangeStatus(models.Model):
    new_email = models.EmailField()  # type: Text
    old_email = models.EmailField()  # type: Text
    updated_at = models.DateTimeField(auto_now=True)  # type: datetime.datetime
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile

    # status: whether an object has been confirmed.
    #   if confirmed, set to confirmation.settings.STATUS_ACTIVE
    status = models.IntegerField(default=0)  # type: int

    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm

class AbstractPushDeviceToken(models.Model):
    APNS = 1
    GCM = 2

    KINDS = (
        (APNS, 'apns'),
        (GCM, 'gcm'),
    )

    kind = models.PositiveSmallIntegerField(choices=KINDS)  # type: int

    # The token is a unique device-specific token that is
    # sent to us from each device:
    #   - APNS token if kind == APNS
    #   - GCM registration id if kind == GCM
    last_updated = models.DateTimeField(auto_now=True)  # type: datetime.datetime

    # [optional] Contains the app id of the device if it is an iOS device
    ios_app_id = models.TextField(null=True)  # type: Optional[Text]

    class Meta:
        abstract = True

class PushDeviceToken(AbstractPushDeviceToken):
    # The user who's device this is
    user = models.ForeignKey(UserProfile, db_index=True, on_delete=CASCADE)  # type: UserProfile
    token = models.CharField(max_length=4096, unique=True)  # type: bytes

def generate_email_token_for_stream() -> str:
    return generate_random_token(32)

class Stream(models.Model):
    MAX_NAME_LENGTH = 60
    name = models.CharField(max_length=MAX_NAME_LENGTH, db_index=True)  # type: Text
    realm = models.ForeignKey(Realm, db_index=True, on_delete=CASCADE)  # type: Realm
    invite_only = models.NullBooleanField(default=False)  # type: Optional[bool]

    # The unique thing about Zephyr public streams is that we never list their
    # users.  We may try to generalize this concept later, but for now
    # we just use a concrete field.  (Zephyr public streams aren't exactly like
    # invite-only streams--while both are private in terms of listing users,
    # for Zephyr we don't even list users to stream members, yet membership
    # is more public in the sense that you don't need a Zulip invite to join.
    # This field is populated directly from UserProfile.is_zephyr_mirror_realm,
    # and the reason for denormalizing field is performance.
    is_in_zephyr_realm = models.BooleanField(default=False)  # type: bool

    # Used by the e-mail forwarder. The e-mail RFC specifies a maximum
    # e-mail length of 254, and our max stream length is 30, so we
    # have plenty of room for the token.
    email_token = models.CharField(
        max_length=32, default=generate_email_token_for_stream)  # type: str
    description = models.CharField(max_length=1024, default=u'')  # type: Text

    date_created = models.DateTimeField(default=timezone_now)  # type: datetime.datetime
    deactivated = models.BooleanField(default=False)  # type: bool

    def __str__(self) -> Text:
        return "<Stream: %s>" % (self.name,)

    def is_public(self) -> bool:
        # All streams are private in Zephyr mirroring realms.
        return not self.invite_only and not self.is_in_zephyr_realm

    class Meta:
        unique_together = ("name", "realm")

    # This is stream information that is sent to clients
    def to_dict(self) -> Dict[str, Any]:
        return dict(name=self.name,
                    stream_id=self.id,
                    description=self.description,
                    invite_only=self.invite_only)

post_save.connect(flush_stream, sender=Stream)
post_delete.connect(flush_stream, sender=Stream)

# The Recipient table is used to map Messages to the set of users who
# received the message.  It is implemented as a set of triples (id,
# type_id, type). We have 3 types of recipients: Huddles (for group
# private messages), UserProfiles (for 1:1 private messages), and
# Streams. The recipient table maps a globally unique recipient id
# (used by the Message table) to the type-specific unique id (the
# stream id, user_profile id, or huddle id).
class Recipient(models.Model):
    type_id = models.IntegerField(db_index=True)  # type: int
    type = models.PositiveSmallIntegerField(db_index=True)  # type: int
    # Valid types are {personal, stream, huddle}
    PERSONAL = 1
    STREAM = 2
    HUDDLE = 3

    class Meta:
        unique_together = ("type", "type_id")

    # N.B. If we used Django's choice=... we would get this for free (kinda)
    _type_names = {
        PERSONAL: 'personal',
        STREAM: 'stream',
        HUDDLE: 'huddle'}

    def type_name(self) -> str:
        # Raises KeyError if invalid
        return self._type_names[self.type]

    def __str__(self) -> Text:
        display_recipient = get_display_recipient(self)
        return "<Recipient: %s (%d, %s)>" % (display_recipient, self.type_id, self.type)

class MutedTopic(models.Model):
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)
    stream = models.ForeignKey(Stream, on_delete=CASCADE)
    recipient = models.ForeignKey(Recipient, on_delete=CASCADE)
    topic_name = models.CharField(max_length=MAX_SUBJECT_LENGTH)

    class Meta:
        unique_together = ('user_profile', 'stream', 'topic_name')

    def __str__(self) -> Text:
        return "<MutedTopic: (%s, %s, %s)>" % (self.user_profile.email, self.stream.name, self.topic_name)

class Client(models.Model):
    name = models.CharField(max_length=30, db_index=True, unique=True)  # type: Text

    def __str__(self) -> Text:
        return "<Client: %s>" % (self.name,)

get_client_cache = {}  # type: Dict[Text, Client]
def get_client(name: Text) -> Client:
    # Accessing KEY_PREFIX through the module is necessary
    # because we need the updated value of the variable.
    cache_name = cache.KEY_PREFIX + name
    if cache_name not in get_client_cache:
        result = get_client_remote_cache(name)
        get_client_cache[cache_name] = result
    return get_client_cache[cache_name]

def get_client_cache_key(name: Text) -> Text:
    return u'get_client:%s' % (make_safe_digest(name),)

@cache_with_key(get_client_cache_key, timeout=3600*24*7)
def get_client_remote_cache(name: Text) -> Client:
    (client, _) = Client.objects.get_or_create(name=name)
    return client

@cache_with_key(get_stream_cache_key, timeout=3600*24*7)
def get_realm_stream(stream_name: Text, realm_id: int) -> Stream:
    return Stream.objects.select_related("realm").get(
        name__iexact=stream_name.strip(), realm_id=realm_id)

def stream_name_in_use(stream_name: Text, realm_id: int) -> bool:
    return Stream.objects.filter(
        name__iexact=stream_name.strip(),
        realm_id=realm_id
    ).exists()

def get_active_streams(realm: Optional[Realm]) -> QuerySet:
    # TODO: Change return type to QuerySet[Stream]
    # NOTE: Return value is used as a QuerySet, so cannot currently be Sequence[QuerySet]
    """
    Return all streams (including invite-only streams) that have not been deactivated.
    """
    return Stream.objects.filter(realm=realm, deactivated=False)

def get_stream(stream_name: Text, realm: Realm) -> Stream:
    '''
    Callers that don't have a Realm object already available should use
    get_realm_stream directly, to avoid unnecessarily fetching the
    Realm object.
    '''
    return get_realm_stream(stream_name, realm.id)

def bulk_get_streams(realm: Realm, stream_names: STREAM_NAMES) -> Dict[Text, Any]:

    def fetch_streams_by_name(stream_names: List[Text]) -> Sequence[Stream]:
        #
        # This should be just
        #
        # Stream.objects.select_related("realm").filter(name__iexact__in=stream_names,
        #                                               realm_id=realm_id)
        #
        # But chaining __in and __iexact doesn't work with Django's
        # ORM, so we have the following hack to construct the relevant where clause
        if len(stream_names) == 0:
            return []
        upper_list = ", ".join(["UPPER(%s)"] * len(stream_names))
        where_clause = "UPPER(zerver_stream.name::text) IN (%s)" % (upper_list,)
        return get_active_streams(realm.id).select_related("realm").extra(
            where=[where_clause],
            params=stream_names)

    return generic_bulk_cached_fetch(lambda stream_name: get_stream_cache_key(stream_name, realm.id),
                                     fetch_streams_by_name,
                                     [stream_name.lower() for stream_name in stream_names],
                                     id_fetcher=lambda stream: stream.name.lower())

def get_recipient_cache_key(type: int, type_id: int) -> Text:
    return u"%s:get_recipient:%s:%s" % (cache.KEY_PREFIX, type, type_id,)

@cache_with_key(get_recipient_cache_key, timeout=3600*24*7)
def get_recipient(type: int, type_id: int) -> Recipient:
    return Recipient.objects.get(type_id=type_id, type=type)

def get_stream_recipient(stream_id: int) -> Recipient:
    return get_recipient(Recipient.STREAM, stream_id)

def get_personal_recipient(user_profile_id: int) -> Recipient:
    return get_recipient(Recipient.PERSONAL, user_profile_id)

def get_huddle_recipient(user_profile_ids: Set[int]) -> Recipient:

    # The caller should ensure that user_profile_ids includes
    # the sender.  Note that get_huddle hits the cache, and then
    # we hit another cache to get the recipient.  We may want to
    # unify our caching strategy here.
    huddle = get_huddle(list(user_profile_ids))
    return get_recipient(Recipient.HUDDLE, huddle.id)

def get_huddle_user_ids(recipient: Recipient) -> List[int]:
    assert(recipient.type == Recipient.HUDDLE)

    return Subscription.objects.filter(
        recipient=recipient,
        active=True,
    ).order_by('user_profile_id').values_list('user_profile_id', flat=True)

def bulk_get_recipients(type: int, type_ids: List[int]) -> Dict[int, Any]:
    def cache_key_function(type_id: int) -> Text:
        return get_recipient_cache_key(type, type_id)

    def query_function(type_ids: List[int]) -> Sequence[Recipient]:
        # TODO: Change return type to QuerySet[Recipient]
        return Recipient.objects.filter(type=type, type_id__in=type_ids)

    return generic_bulk_cached_fetch(cache_key_function, query_function, type_ids,
                                     id_fetcher=lambda recipient: recipient.type_id)

def get_stream_recipients(stream_ids: List[int]) -> List[Recipient]:

    '''
    We could call bulk_get_recipients(...).values() here, but it actually
    leads to an extra query in test mode.
    '''
    return Recipient.objects.filter(
        type=Recipient.STREAM,
        type_id__in=stream_ids,
    )

class AbstractMessage(models.Model):
    sender = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    recipient = models.ForeignKey(Recipient, on_delete=CASCADE)  # type: Recipient
    subject = models.CharField(max_length=MAX_SUBJECT_LENGTH, db_index=True)  # type: Text
    content = models.TextField()  # type: Text
    rendered_content = models.TextField(null=True)  # type: Optional[Text]
    rendered_content_version = models.IntegerField(null=True)  # type: Optional[int]
    pub_date = models.DateTimeField('date published', db_index=True)  # type: datetime.datetime
    sending_client = models.ForeignKey(Client, on_delete=CASCADE)  # type: Client
    last_edit_time = models.DateTimeField(null=True)  # type: Optional[datetime.datetime]
    edit_history = models.TextField(null=True)  # type: Optional[Text]
    has_attachment = models.BooleanField(default=False, db_index=True)  # type: bool
    has_image = models.BooleanField(default=False, db_index=True)  # type: bool
    has_link = models.BooleanField(default=False, db_index=True)  # type: bool

    class Meta:
        abstract = True

    def __str__(self) -> Text:
        display_recipient = get_display_recipient(self.recipient)
        return "<%s: %s / %s / %s>" % (self.__class__.__name__, display_recipient,
                                       self.subject, self.sender)


class ArchivedMessage(AbstractMessage):
    archive_timestamp = models.DateTimeField(default=timezone_now, db_index=True)  # type: datetime.datetime


class Message(AbstractMessage):

    def topic_name(self) -> Text:
        """
        Please start using this helper to facilitate an
        eventual switch over to a separate topic table.
        """
        return self.subject

    def is_stream_message(self) -> bool:
        '''
        Find out whether a message is a stream message by
        looking up its recipient.type.  TODO: Make this
        an easier operation by denormalizing the message
        type onto Message, either explicity (message.type)
        or implicitly (message.stream_id is not None).
        '''
        return self.recipient.type == Recipient.STREAM

    def get_realm(self) -> Realm:
        return self.sender.realm

    def save_rendered_content(self) -> None:
        self.save(update_fields=["rendered_content", "rendered_content_version"])

    @staticmethod
    def need_to_render_content(rendered_content: Optional[Text],
                               rendered_content_version: Optional[int],
                               bugdown_version: int) -> bool:
        return (rendered_content is None or
                rendered_content_version is None or
                rendered_content_version < bugdown_version)

    def to_log_dict(self) -> Dict[str, Any]:
        return dict(
            id                = self.id,
            sender_id         = self.sender.id,
            sender_email      = self.sender.email,
            sender_realm_str  = self.sender.realm.string_id,
            sender_full_name  = self.sender.full_name,
            sender_short_name = self.sender.short_name,
            sending_client    = self.sending_client.name,
            type              = self.recipient.type_name(),
            recipient         = get_display_recipient(self.recipient),
            subject           = self.topic_name(),
            content           = self.content,
            timestamp         = datetime_to_timestamp(self.pub_date))

    def sent_by_human(self) -> bool:
        sending_client = self.sending_client.name.lower()

        return (sending_client in ('zulipandroid', 'zulipios', 'zulipdesktop',
                                   'zulipmobile', 'zulipelectron', 'snipe',
                                   'website', 'ios', 'android')) or (
                                       'desktop app' in sending_client)

    @staticmethod
    def content_has_attachment(content: Text) -> Match:
        return re.search(r'[/\-]user[\-_]uploads[/\.-]', content)

    @staticmethod
    def content_has_image(content: Text) -> bool:
        return bool(re.search(r'[/\-]user[\-_]uploads[/\.-]\S+\.(bmp|gif|jpg|jpeg|png|webp)',
                              content, re.IGNORECASE))

    @staticmethod
    def content_has_link(content: Text) -> bool:
        return ('http://' in content or
                'https://' in content or
                '/user_uploads' in content or
                (settings.ENABLE_FILE_LINKS and 'file:///' in content) or
                'bitcoin:' in content)

    @staticmethod
    def is_status_message(content: Text, rendered_content: Text) -> bool:
        """
        Returns True if content and rendered_content are from 'me_message'
        """
        if content.startswith('/me ') and '\n' not in content:
            if rendered_content.startswith('<p>') and rendered_content.endswith('</p>'):
                return True
        return False

    def update_calculated_fields(self) -> None:
        # TODO: rendered_content could also be considered a calculated field
        content = self.content
        self.has_attachment = bool(Message.content_has_attachment(content))
        self.has_image = bool(Message.content_has_image(content))
        self.has_link = bool(Message.content_has_link(content))

@receiver(pre_save, sender=Message)
def pre_save_message(sender: Any, **kwargs: Any) -> None:
    if kwargs['update_fields'] is None or "content" in kwargs['update_fields']:
        message = kwargs['instance']
        message.update_calculated_fields()

def get_context_for_message(message: Message) -> Sequence[Message]:
    # TODO: Change return type to QuerySet[Message]
    return Message.objects.filter(
        recipient_id=message.recipient_id,
        subject=message.subject,
        id__lt=message.id,
        pub_date__gt=message.pub_date - timedelta(minutes=15),
    ).order_by('-id')[:10]

post_save.connect(flush_message, sender=Message)

class Reaction(models.Model):
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    message = models.ForeignKey(Message, on_delete=CASCADE)  # type: Message
    emoji_name = models.TextField()  # type: Text
    emoji_code = models.TextField()  # type: Text

    UNICODE_EMOJI       = u'unicode_emoji'
    REALM_EMOJI         = u'realm_emoji'
    ZULIP_EXTRA_EMOJI   = u'zulip_extra_emoji'
    REACTION_TYPES      = ((UNICODE_EMOJI, _("Unicode emoji")),
                           (REALM_EMOJI, _("Custom emoji")),
                           (ZULIP_EXTRA_EMOJI, _("Zulip extra emoji")))

    reaction_type = models.CharField(default=UNICODE_EMOJI, choices=REACTION_TYPES, max_length=30)  # type: Text

    class Meta:
        unique_together = ("user_profile", "message", "emoji_name")

    @staticmethod
    def get_raw_db_rows(needed_ids: List[int]) -> List[Dict[str, Any]]:
        fields = ['message_id', 'emoji_name', 'emoji_code', 'reaction_type',
                  'user_profile__email', 'user_profile__id', 'user_profile__full_name']
        return Reaction.objects.filter(message_id__in=needed_ids).values(*fields)

# Whenever a message is sent, for each user subscribed to the
# corresponding Recipient object, we add a row to the UserMessage
# table indicating that that user received that message.  This table
# allows us to quickly query any user's last 1000 messages to generate
# the home view.
#
# Additionally, the flags field stores metadata like whether the user
# has read the message, starred or collapsed the message, was
# mentioned in the message, etc.
#
# UserMessage is the largest table in a Zulip installation, even
# though each row is only 4 integers.
class AbstractUserMessage(models.Model):
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    # WARNING: We removed the previously-final flag,
    # is_me_message, without clearing any values it might have had in
    # the database.  So when we next add a flag, you need to do a
    # migration to set it to 0 first
    ALL_FLAGS = ['read', 'starred', 'collapsed', 'mentioned', 'wildcard_mentioned',
                 'summarize_in_home', 'summarize_in_stream', 'force_expand', 'force_collapse',
                 'has_alert_word', "historical"]
    flags = BitField(flags=ALL_FLAGS, default=0)  # type: BitHandler

    class Meta:
        abstract = True
        unique_together = ("user_profile", "message")

    @staticmethod
    def where_unread() -> str:
        # Use this for Django ORM queries where we are getting lots
        # of rows.  This custom SQL plays nice with our partial indexes.
        # Grep the code for example usage.
        return 'flags & 1 = 0'

    def flags_list(self) -> List[str]:
        flags = int(self.flags)
        return self.flags_list_for_flags(flags)

    @staticmethod
    def flags_list_for_flags(val: int) -> List[str]:
        '''
        This function is highly optimized, because it actually slows down
        sending messages in a naive implementation.
        '''
        flags = []
        mask = 1
        for flag in UserMessage.ALL_FLAGS:
            if val & mask:
                flags.append(flag)
            mask <<= 1
        return flags

    def __str__(self) -> Text:
        display_recipient = get_display_recipient(self.message.recipient)
        return "<%s: %s / %s (%s)>" % (self.__class__.__name__, display_recipient,
                                       self.user_profile.email, self.flags_list())


class ArchivedUserMessage(AbstractUserMessage):
    message = models.ForeignKey(ArchivedMessage, on_delete=CASCADE)  # type: Message
    archive_timestamp = models.DateTimeField(default=timezone_now, db_index=True)  # type: datetime.datetime


class UserMessage(AbstractUserMessage):
    message = models.ForeignKey(Message, on_delete=CASCADE)  # type: Message


class AbstractAttachment(models.Model):
    file_name = models.TextField(db_index=True)  # type: Text
    # path_id is a storage location agnostic representation of the path of the file.
    # If the path of a file is http://localhost:9991/user_uploads/a/b/abc/temp_file.py
    # then its path_id will be a/b/abc/temp_file.py.
    path_id = models.TextField(db_index=True, unique=True)  # type: Text
    owner = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    realm = models.ForeignKey(Realm, blank=True, null=True, on_delete=CASCADE)  # type: Optional[Realm]
    is_realm_public = models.BooleanField(default=False)  # type: bool
    create_time = models.DateTimeField(default=timezone_now,
                                       db_index=True)  # type: datetime.datetime
    size = models.IntegerField(null=True)  # type: Optional[int]

    class Meta:
        abstract = True

    def __str__(self) -> Text:
        return "<%s: %s>" % (self.__class__.__name__, self.file_name,)


class ArchivedAttachment(AbstractAttachment):
    archive_timestamp = models.DateTimeField(default=timezone_now, db_index=True)  # type: datetime.datetime
    messages = models.ManyToManyField(ArchivedMessage)  # type: Manager


class Attachment(AbstractAttachment):
    messages = models.ManyToManyField(Message)  # type: Manager

    def is_claimed(self) -> bool:
        return self.messages.count() > 0

    def to_dict(self) -> Dict[str, Any]:
        return {
            'id': self.id,
            'name': self.file_name,
            'path_id': self.path_id,
            'size': self.size,
            # convert to JavaScript-style UNIX timestamp so we can take
            # advantage of client timezones.
            'create_time': time.mktime(self.create_time.timetuple()) * 1000,
            'messages': [{
                'id': m.id,
                'name': time.mktime(m.pub_date.timetuple()) * 1000
            } for m in self.messages.all()]
        }

def validate_attachment_request(user_profile: UserProfile, path_id: Text) -> Optional[bool]:
    try:
        attachment = Attachment.objects.get(path_id=path_id)
        messages = attachment.messages.all()

        if user_profile == attachment.owner:
            # If you own the file, you can access it.
            return True
        elif attachment.is_realm_public and attachment.realm == user_profile.realm:
            # Any user in the realm can access realm-public files
            return True
        elif UserMessage.objects.filter(user_profile=user_profile, message__in=messages).exists():
            # If it was sent in a private message or private stream
            # message, then anyone who received that message can access it.
            return True
        else:
            return False
    except Attachment.DoesNotExist:
        return None

def get_old_unclaimed_attachments(weeks_ago: int) -> Sequence[Attachment]:
    # TODO: Change return type to QuerySet[Attachment]
    delta_weeks_ago = timezone_now() - datetime.timedelta(weeks=weeks_ago)
    old_attachments = Attachment.objects.filter(messages=None, create_time__lt=delta_weeks_ago)
    return old_attachments

class Subscription(models.Model):
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    recipient = models.ForeignKey(Recipient, on_delete=CASCADE)  # type: Recipient
    active = models.BooleanField(default=True)  # type: bool
    in_home_view = models.NullBooleanField(default=True)  # type: Optional[bool]

    DEFAULT_STREAM_COLOR = u"#c2c2c2"
    color = models.CharField(max_length=10, default=DEFAULT_STREAM_COLOR)  # type: Text
    pin_to_top = models.BooleanField(default=False)  # type: bool

    desktop_notifications = models.BooleanField(default=True)  # type: bool
    audible_notifications = models.BooleanField(default=True)  # type: bool
    push_notifications = models.BooleanField(default=False)  # type: bool
    email_notifications = models.BooleanField(default=False)  # type: bool

    # Combination desktop + audible notifications superseded by the
    # above.
    notifications = models.BooleanField(default=False)  # type: bool

    class Meta:
        unique_together = ("user_profile", "recipient")

    def __str__(self) -> Text:
        return "<Subscription: %s -> %s>" % (self.user_profile, self.recipient)

@cache_with_key(user_profile_by_id_cache_key, timeout=3600*24*7)
def get_user_profile_by_id(uid: int) -> UserProfile:
    return UserProfile.objects.select_related().get(id=uid)

@cache_with_key(user_profile_by_email_cache_key, timeout=3600*24*7)
def get_user_profile_by_email(email: Text) -> UserProfile:
    return UserProfile.objects.select_related().get(email__iexact=email.strip())

@cache_with_key(user_profile_by_api_key_cache_key, timeout=3600*24*7)
def get_user_profile_by_api_key(api_key: Text) -> UserProfile:
    return UserProfile.objects.select_related().get(api_key=api_key)

@cache_with_key(user_profile_cache_key, timeout=3600*24*7)
def get_user(email: Text, realm: Realm) -> UserProfile:
    return UserProfile.objects.select_related().get(email__iexact=email.strip(), realm=realm)

def get_user_including_cross_realm(email: Text, realm: Optional[Realm]=None) -> UserProfile:
    if is_cross_realm_bot_email(email):
        return get_system_bot(email)
    assert realm is not None
    return get_user(email, realm)

@cache_with_key(bot_profile_cache_key, timeout=3600*24*7)
def get_system_bot(email: Text) -> UserProfile:
    return UserProfile.objects.select_related().get(email__iexact=email.strip())

@cache_with_key(realm_user_dicts_cache_key, timeout=3600*24*7)
def get_realm_user_dicts(realm_id: int) -> List[Dict[str, Any]]:
    return UserProfile.objects.filter(
        realm_id=realm_id,
    ).values(*realm_user_dict_fields)

@cache_with_key(active_user_ids_cache_key, timeout=3600*24*7)
def active_user_ids(realm_id: int) -> List[int]:
    query = UserProfile.objects.filter(
        realm_id=realm_id,
        is_active=True
    ).values_list('id', flat=True)
    return list(query)

@cache_with_key(bot_dicts_in_realm_cache_key, timeout=3600*24*7)
def get_bot_dicts_in_realm(realm: Realm) -> List[Dict[str, Any]]:
    return UserProfile.objects.filter(realm=realm, is_bot=True).values(*bot_dict_fields)

def is_cross_realm_bot_email(email: Text) -> bool:
    return email.lower() in settings.CROSS_REALM_BOT_EMAILS

# The Huddle class represents a group of individuals who have had a
# Group Private Message conversation together.  The actual membership
# of the Huddle is stored in the Subscription table just like with
# Streams, and a hash of that list is stored in the huddle_hash field
# below, to support efficiently mapping from a set of users to the
# corresponding Huddle object.
class Huddle(models.Model):
    # TODO: We should consider whether using
    # CommaSeparatedIntegerField would be better.
    huddle_hash = models.CharField(max_length=40, db_index=True, unique=True)  # type: Text

def get_huddle_hash(id_list: List[int]) -> Text:
    id_list = sorted(set(id_list))
    hash_key = ",".join(str(x) for x in id_list)
    return make_safe_digest(hash_key)

def huddle_hash_cache_key(huddle_hash: Text) -> Text:
    return u"huddle_by_hash:%s" % (huddle_hash,)

def get_huddle(id_list: List[int]) -> Huddle:
    huddle_hash = get_huddle_hash(id_list)
    return get_huddle_backend(huddle_hash, id_list)

@cache_with_key(lambda huddle_hash, id_list: huddle_hash_cache_key(huddle_hash), timeout=3600*24*7)
def get_huddle_backend(huddle_hash: Text, id_list: List[int]) -> Huddle:
    with transaction.atomic():
        (huddle, created) = Huddle.objects.get_or_create(huddle_hash=huddle_hash)
        if created:
            recipient = Recipient.objects.create(type_id=huddle.id,
                                                 type=Recipient.HUDDLE)
            subs_to_create = [Subscription(recipient=recipient,
                                           user_profile_id=user_profile_id)
                              for user_profile_id in id_list]
            Subscription.objects.bulk_create(subs_to_create)
        return huddle

def clear_database() -> None:  # nocoverage # Only used in populate_db
    pylibmc.Client(['127.0.0.1']).flush_all()
    model = None  # type: Any
    for model in [Message, Stream, UserProfile, Recipient,
                  Realm, Subscription, Huddle, UserMessage, Client,
                  DefaultStream]:
        model.objects.all().delete()
    Session.objects.all().delete()

class UserActivity(models.Model):
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    client = models.ForeignKey(Client, on_delete=CASCADE)  # type: Client
    query = models.CharField(max_length=50, db_index=True)  # type: Text

    count = models.IntegerField()  # type: int
    last_visit = models.DateTimeField('last visit')  # type: datetime.datetime

    class Meta:
        unique_together = ("user_profile", "client", "query")

class UserActivityInterval(models.Model):
    MIN_INTERVAL_LENGTH = datetime.timedelta(minutes=15)

    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    start = models.DateTimeField('start time', db_index=True)  # type: datetime.datetime
    end = models.DateTimeField('end time', db_index=True)  # type: datetime.datetime


class UserPresence(models.Model):
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    client = models.ForeignKey(Client, on_delete=CASCADE)  # type: Client

    # Valid statuses
    ACTIVE = 1
    IDLE = 2

    timestamp = models.DateTimeField('presence changed')  # type: datetime.datetime
    status = models.PositiveSmallIntegerField(default=ACTIVE)  # type: int

    @staticmethod
    def status_to_string(status: int) -> str:
        if status == UserPresence.ACTIVE:
            return 'active'
        elif status == UserPresence.IDLE:
            return 'idle'
        else:  # nocoverage # TODO: Add a presence test to cover this.
            raise ValueError('Unknown status: %s' % (status,))

    @staticmethod
    def get_status_dict_by_user(user_profile: UserProfile) -> Dict[str, Dict[str, Any]]:
        query = UserPresence.objects.filter(user_profile=user_profile).values(
            'client__name',
            'status',
            'timestamp',
            'user_profile__email',
            'user_profile__id',
            'user_profile__enable_offline_push_notifications',
        )
        presence_rows = list(query)

        mobile_user_ids = set()  # type: Set[int]
        if PushDeviceToken.objects.filter(user=user_profile).exists():  # nocoverage
            # TODO: Add a test, though this is low priority, since we don't use mobile_user_ids yet.
            mobile_user_ids.add(user_profile.id)

        return UserPresence.get_status_dicts_for_rows(presence_rows, mobile_user_ids)

    @staticmethod
    def get_status_dict_by_realm(realm_id: int) -> Dict[str, Dict[str, Any]]:
        user_profile_ids = UserProfile.objects.filter(
            realm_id=realm_id,
            is_active=True,
            is_bot=False
        ).order_by('id').values_list('id', flat=True)

        user_profile_ids = list(user_profile_ids)
        if not user_profile_ids:  # nocoverage
            # This conditional is necessary because query_for_ids
            # throws an exception if passed an empty list.
            #
            # It's not clear this condition is actually possible,
            # though, because it shouldn't be possible to end up with
            # a realm with 0 active users.
            return {}

        two_weeks_ago = timezone_now() - datetime.timedelta(weeks=2)
        query = UserPresence.objects.filter(
            timestamp__gte=two_weeks_ago
        ).values(
            'client__name',
            'status',
            'timestamp',
            'user_profile__email',
            'user_profile__id',
            'user_profile__enable_offline_push_notifications',
        )

        query = query_for_ids(
            query=query,
            user_ids=user_profile_ids,
            field='user_profile_id'
        )
        presence_rows = list(query)

        mobile_query = PushDeviceToken.objects.distinct(
            'user_id'
        ).values_list(
            'user_id',
            flat=True
        )

        mobile_query = query_for_ids(
            query=mobile_query,
            user_ids=user_profile_ids,
            field='user_id'
        )
        mobile_user_ids = set(mobile_query)

        return UserPresence.get_status_dicts_for_rows(presence_rows, mobile_user_ids)

    @staticmethod
    def get_status_dicts_for_rows(presence_rows: List[Dict[str, Any]],
                                  mobile_user_ids: Set[int]) -> Dict[str, Dict[str, Any]]:

        info_row_dct = defaultdict(list)  # type: DefaultDict[str, List[Dict[str, Any]]]
        for row in presence_rows:
            email = row['user_profile__email']
            client_name = row['client__name']
            status = UserPresence.status_to_string(row['status'])
            dt = row['timestamp']
            timestamp = datetime_to_timestamp(dt)
            push_enabled = row['user_profile__enable_offline_push_notifications']
            has_push_devices = row['user_profile__id'] in mobile_user_ids
            pushable = (push_enabled and has_push_devices)

            info = dict(
                client=client_name,
                status=status,
                dt=dt,
                timestamp=timestamp,
                pushable=pushable,
            )

            info_row_dct[email].append(info)

        user_statuses = dict()  # type: Dict[str, Dict[str, Any]]

        for email, info_rows in info_row_dct.items():
            # Note that datetime values have sub-second granularity, which is
            # mostly important for avoiding test flakes, but it's also technically
            # more precise for real users.
            by_time = lambda row: row['dt']
            most_recent_info = max(info_rows, key=by_time)

            # We don't send datetime values to the client.
            for r in info_rows:
                del r['dt']

            client_dict = {info['client']: info for info in info_rows}
            user_statuses[email] = client_dict

            # The word "aggegrated" here is possibly misleading.
            # It's really just the most recent client's info.
            user_statuses[email]['aggregated'] = dict(
                client=most_recent_info['client'],
                status=most_recent_info['status'],
                timestamp=most_recent_info['timestamp'],
            )

        return user_statuses

    @staticmethod
    def to_presence_dict(client_name: Text, status: int, dt: datetime.datetime, push_enabled: bool=False,
                         has_push_devices: bool=False) -> Dict[str, Any]:
        presence_val = UserPresence.status_to_string(status)

        timestamp = datetime_to_timestamp(dt)
        return dict(
            client=client_name,
            status=presence_val,
            timestamp=timestamp,
            pushable=(push_enabled and has_push_devices),
        )

    def to_dict(self) -> Dict[str, Any]:
        return UserPresence.to_presence_dict(
            self.client.name,
            self.status,
            self.timestamp
        )

    @staticmethod
    def status_from_string(status: NonBinaryStr) -> Optional[int]:
        if status == 'active':
            status_val = UserPresence.ACTIVE  # type: Optional[int] # See https://github.com/python/mypy/issues/2611
        elif status == 'idle':
            status_val = UserPresence.IDLE
        else:
            status_val = None

        return status_val

    class Meta:
        unique_together = ("user_profile", "client")

class DefaultStream(models.Model):
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm
    stream = models.ForeignKey(Stream, on_delete=CASCADE)  # type: Stream

    class Meta:
        unique_together = ("realm", "stream")

class DefaultStreamGroup(models.Model):
    MAX_NAME_LENGTH = 60
    name = models.CharField(max_length=MAX_NAME_LENGTH, db_index=True)  # type: Text
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm
    streams = models.ManyToManyField('Stream')  # type: Manager
    description = models.CharField(max_length=1024, default=u'')  # type: Text

    class Meta:
        unique_together = ("realm", "name")

    def to_dict(self) -> Dict[str, Any]:
        return dict(name=self.name,
                    id=self.id,
                    description=self.description,
                    streams=[stream.to_dict() for stream in self.streams.all()])

def get_default_stream_groups(realm: Realm) -> List[DefaultStreamGroup]:
    return DefaultStreamGroup.objects.filter(realm=realm)

class AbstractScheduledJob(models.Model):
    scheduled_timestamp = models.DateTimeField(db_index=True)  # type: datetime.datetime
    # JSON representation of arguments to consumer
    data = models.TextField()  # type: Text
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm

    class Meta:
        abstract = True

class ScheduledEmail(AbstractScheduledJob):
    # Exactly one of user or address should be set. These are used to
    # filter the set of ScheduledEmails.
    user = models.ForeignKey(UserProfile, null=True, on_delete=CASCADE)  # type: Optional[UserProfile]
    # Just the address part of a full "name <address>" email address
    address = models.EmailField(null=True, db_index=True)  # type: Optional[Text]

    # Valid types are below
    WELCOME = 1
    DIGEST = 2
    INVITATION_REMINDER = 3
    type = models.PositiveSmallIntegerField()  # type: int

    def __str__(self) -> Text:
        return "<ScheduledEmail: %s %s %s>" % (self.type, self.user or self.address,
                                               self.scheduled_timestamp)

class ScheduledMessage(models.Model):
    sender = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    recipient = models.ForeignKey(Recipient, on_delete=CASCADE)  # type: Recipient
    subject = models.CharField(max_length=MAX_SUBJECT_LENGTH)  # type: Text
    content = models.TextField()  # type: Text
    sending_client = models.ForeignKey(Client, on_delete=CASCADE)  # type: Client
    stream = models.ForeignKey(Stream, null=True, on_delete=CASCADE)  # type: Optional[Stream]
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm
    scheduled_timestamp = models.DateTimeField(db_index=True)  # type: datetime.datetime
    delivered = models.BooleanField(default=False)  # type: bool

    SEND_LATER = 1
    REMIND = 2

    DELIVERY_TYPES = (
        (SEND_LATER, 'send_later'),
        (REMIND, 'remind'),
    )

    delivery_type = models.PositiveSmallIntegerField(choices=DELIVERY_TYPES,
                                                     default=SEND_LATER)  # type: int

    def __str__(self) -> Text:
        display_recipient = get_display_recipient(self.recipient)
        return "<ScheduledMessage: %s %s %s %s>" % (display_recipient,
                                                    self.subject, self.sender,
                                                    self.scheduled_timestamp)

EMAIL_TYPES = {
    'followup_day1': ScheduledEmail.WELCOME,
    'followup_day2': ScheduledEmail.WELCOME,
    'digest': ScheduledEmail.DIGEST,
    'invitation_reminder': ScheduledEmail.INVITATION_REMINDER,
}

class RealmAuditLog(models.Model):
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm
    acting_user = models.ForeignKey(UserProfile, null=True, related_name='+', on_delete=CASCADE)  # type: Optional[UserProfile]
    modified_user = models.ForeignKey(UserProfile, null=True, related_name='+', on_delete=CASCADE)  # type: Optional[UserProfile]
    modified_stream = models.ForeignKey(Stream, null=True, on_delete=CASCADE)  # type: Optional[Stream]
    event_last_message_id = models.IntegerField(null=True)  # type: Optional[int]
    event_type = models.CharField(max_length=40)  # type: Text
    event_time = models.DateTimeField(db_index=True)  # type: datetime.datetime
    # If True, event_time is an overestimate of the true time. Can be used
    # by migrations when introducing a new event_type.
    backfilled = models.BooleanField(default=False)  # type: bool
    extra_data = models.TextField(null=True)  # type: Optional[Text]

    def __str__(self) -> str:
        if self.modified_user is not None:
            return "<RealmAuditLog: %s %s %s>" % (self.modified_user, self.event_type, self.event_time)
        if self.modified_stream is not None:
            return "<RealmAuditLog: %s %s %s>" % (self.modified_stream, self.event_type, self.event_time)
        return "<RealmAuditLog: %s %s %s>" % (self.realm, self.event_type, self.event_time)

class UserHotspot(models.Model):
    user = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    hotspot = models.CharField(max_length=30)  # type: Text
    timestamp = models.DateTimeField(default=timezone_now)  # type: datetime.datetime

    class Meta:
        unique_together = ("user", "hotspot")

class CustomProfileField(models.Model):
    realm = models.ForeignKey(Realm, on_delete=CASCADE)  # type: Realm
    name = models.CharField(max_length=100)  # type: Text

    INTEGER = 1
    FLOAT = 2
    SHORT_TEXT = 3
    LONG_TEXT = 4

    FIELD_TYPE_DATA = [
        # Type, Name, Validator, Converter
        (INTEGER, u'Integer', check_int, int),
        (FLOAT, u'Float', check_float, float),
        (SHORT_TEXT, u'Short Text', check_short_string, str),
        (LONG_TEXT, u'Long Text', check_string, str),
    ]  # type: List[Tuple[int, Text, Validator, Callable[[Any], Any]]]

    FIELD_VALIDATORS = {item[0]: item[2] for item in FIELD_TYPE_DATA}  # type: Dict[int, Validator]
    FIELD_CONVERTERS = {item[0]: item[3] for item in FIELD_TYPE_DATA}  # type: Dict[int, Callable[[Any], Any]]
    FIELD_TYPE_CHOICES = [(item[0], item[1]) for item in FIELD_TYPE_DATA]  # type: List[Tuple[int, Text]]

    field_type = models.PositiveSmallIntegerField(choices=FIELD_TYPE_CHOICES,
                                                  default=SHORT_TEXT)  # type: int

    class Meta:
        unique_together = ('realm', 'name')

    def as_dict(self) -> Dict[str, Union[int, Text]]:
        return {
            'id': self.id,
            'name': self.name,
            'type': self.field_type,
        }

    def __str__(self) -> str:
        return "<CustomProfileField: %s %s %s>" % (self.realm, self.name, self.field_type)

def custom_profile_fields_for_realm(realm_id: int) -> List[CustomProfileField]:
    return CustomProfileField.objects.filter(realm=realm_id).order_by('name')

class CustomProfileFieldValue(models.Model):
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    field = models.ForeignKey(CustomProfileField, on_delete=CASCADE)  # type: CustomProfileField
    value = models.TextField()  # type: Text

    class Meta:
        unique_together = ('user_profile', 'field')

    def __str__(self) -> str:
        return "<CustomProfileFieldValue: %s %s %s>" % (self.user_profile, self.field, self.value)

# Interfaces for services
# They provide additional functionality like parsing message to obtain query url, data to be sent to url,
# and parsing the response.
GENERIC_INTERFACE = u'GenericService'
SLACK_INTERFACE = u'SlackOutgoingWebhookService'

# A Service corresponds to either an outgoing webhook bot or an embedded bot.
# The type of Service is determined by the bot_type field of the referenced
# UserProfile.
#
# If the Service is an outgoing webhook bot:
# - name is any human-readable identifier for the Service
# - base_url is the address of the third-party site
# - token is used for authentication with the third-party site
#
# If the Service is an embedded bot:
# - name is the canonical name for the type of bot (e.g. 'xkcd' for an instance
#   of the xkcd bot); multiple embedded bots can have the same name, but all
#   embedded bots with the same name will run the same code
# - base_url and token are currently unused
class Service(models.Model):
    name = models.CharField(max_length=UserProfile.MAX_NAME_LENGTH)  # type: Text
    # Bot user corresponding to the Service.  The bot_type of this user
    # deterines the type of service.  If non-bot services are added later,
    # user_profile can also represent the owner of the Service.
    user_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    base_url = models.TextField()  # type: Text
    token = models.TextField()  # type: Text
    # Interface / API version of the service.
    interface = models.PositiveSmallIntegerField(default=1)  # type: int

    # Valid interfaces are {generic, zulip_bot_service, slack}
    GENERIC = 1
    SLACK = 2

    ALLOWED_INTERFACE_TYPES = [
        GENERIC,
        SLACK,
    ]
    # N.B. If we used Django's choice=... we would get this for free (kinda)
    _interfaces = {
        GENERIC: GENERIC_INTERFACE,
        SLACK: SLACK_INTERFACE,
    }  # type: Dict[int, Text]

    def interface_name(self) -> Text:
        # Raises KeyError if invalid
        return self._interfaces[self.interface]


def get_bot_services(user_profile_id: str) -> List[Service]:
    return list(Service.objects.filter(user_profile__id=user_profile_id))

def get_service_profile(user_profile_id: str, service_name: str) -> Service:
    return Service.objects.get(user_profile__id=user_profile_id, name=service_name)


class BotStorageData(models.Model):
    bot_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    key = models.TextField(db_index=True)  # type: Text
    value = models.TextField()  # type: Text

    class Meta:
        unique_together = ("bot_profile", "key")

class BotConfigData(models.Model):
    bot_profile = models.ForeignKey(UserProfile, on_delete=CASCADE)  # type: UserProfile
    key = models.TextField(db_index=True)  # type: Text
    value = models.TextField()  # type: Text

    class Meta(object):
        unique_together = ("bot_profile", "key")