# See http://zulip.readthedocs.io/en/latest/events-system.html for
# high-level documentation on how this system works.

import copy
import ujson

from django.utils.translation import ugettext as _
from django.conf import settings
from importlib import import_module
from six.moves import filter, map
from typing import (
    cast, Any, Callable, Dict, Iterable, List, Optional, Sequence, Set, Text, Tuple, Union
)

session_engine = import_module(settings.SESSION_ENGINE)

from zerver.lib.alert_words import user_alert_words
from zerver.lib.attachments import user_attachments
from zerver.lib.avatar import avatar_url, avatar_url_from_dict
from zerver.lib.hotspots import get_next_hotspots
from zerver.lib.integrations import EMBEDDED_BOTS
from zerver.lib.message import (
    aggregate_unread_data,
    apply_unread_message_event,
    get_raw_unread_data,
)
from zerver.lib.narrow import check_supported_events_narrow_filter
from zerver.lib.soft_deactivation import maybe_catch_up_soft_deactivated_user
from zerver.lib.realm_icon import realm_icon_url
from zerver.lib.request import JsonableError
from zerver.lib.topic_mutes import get_topic_mutes
from zerver.lib.actions import (
    validate_user_access_to_subscribers_helper,
    do_get_streams, get_default_streams_for_realm,
    gather_subscriptions_helper, get_cross_realm_dicts,
    get_status_dict, streams_to_dicts_sorted
)
from zerver.lib.upload import get_total_uploads_size_for_user
from zerver.tornado.event_queue import request_event_queue, get_user_events
from zerver.models import Client, Message, Realm, UserPresence, UserProfile, \
    get_user_profile_by_id, \
    get_realm_user_dicts, realm_filters_for_realm, get_user,\
    get_owned_bot_dicts, custom_profile_fields_for_realm, get_realm_domains
from zproject.backends import email_auth_enabled, password_auth_enabled
from version import ZULIP_VERSION


def get_raw_user_data(realm_id):
    # type: (int) -> Dict[int, Dict[str, Text]]
    user_dicts = get_realm_user_dicts(realm_id)

    def user_data(row):
        # type: (Dict[str, Any]) -> Dict[str, Any]
        avatar_url = avatar_url_from_dict(row)
        is_admin = row['is_realm_admin']

        return dict(
            email=row['email'],
            user_id=row['id'],
            avatar_url=avatar_url,
            is_admin=is_admin,
            is_bot=row['is_bot'],
            full_name=row['full_name'],
            timezone=row['timezone'],
            is_active = row['is_active'],
        )

    return {
        row['id']: user_data(row)
        for row in user_dicts
    }

def always_want(msg_type):
    # type: (str) -> bool
    '''
    This function is used as a helper in
    fetch_initial_state_data, when the user passes
    in None for event_types, and we want to fetch
    info for every event type.  Defining this at module
    level makes it easier to mock.
    '''
    return True

# Fetch initial data.  When event_types is not specified, clients want
# all event types.  Whenever you add new code to this function, you
# should also add corresponding events for changes in the data
# structures and new code to apply_events (and add a test in EventsRegisterTest).
def fetch_initial_state_data(user_profile, event_types, queue_id,
                             include_subscribers=True):
    # type: (UserProfile, Optional[Iterable[str]], str, bool) -> Dict[str, Any]
    state = {'queue_id': queue_id}  # type: Dict[str, Any]

    if event_types is None:
        # return True always
        want = always_want  # type: Callable[[str], bool]
    else:
        want = set(event_types).__contains__

    if want('alert_words'):
        state['alert_words'] = user_alert_words(user_profile)

    if want('custom_profile_fields'):
        fields = custom_profile_fields_for_realm(user_profile.realm.id)
        state['custom_profile_fields'] = [f.as_dict() for f in fields]

    if want('attachments'):
        state['attachments'] = user_attachments(user_profile)

    if want('upload_quota'):
        state['upload_quota'] = user_profile.quota

    if want('total_uploads_size'):
        state['total_uploads_size'] = get_total_uploads_size_for_user(user_profile)

    if want('hotspots'):
        state['hotspots'] = get_next_hotspots(user_profile)

    if want('message'):
        # The client should use get_messages() to fetch messages
        # starting with the max_message_id.  They will get messages
        # newer than that ID via get_events()
        messages = Message.objects.filter(usermessage__user_profile=user_profile).order_by('-id')[:1]
        if messages:
            state['max_message_id'] = messages[0].id
        else:
            state['max_message_id'] = -1

    if want('muted_topics'):
        state['muted_topics'] = get_topic_mutes(user_profile)

    if want('pointer'):
        state['pointer'] = user_profile.pointer

    if want('presence'):
        state['presences'] = get_status_dict(user_profile)

    if want('realm'):
        for property_name in Realm.property_types:
            state['realm_' + property_name] = getattr(user_profile.realm, property_name)

        # Most state is handled via the property_types framework;
        # these manual entries are for those realm settings that don't
        # fit into that framework.
        state['realm_authentication_methods'] = user_profile.realm.authentication_methods_dict()
        state['realm_allow_message_editing'] = user_profile.realm.allow_message_editing
        state['realm_message_content_edit_limit_seconds'] = user_profile.realm.message_content_edit_limit_seconds
        state['realm_icon_url'] = realm_icon_url(user_profile.realm)
        state['realm_icon_source'] = user_profile.realm.icon_source
        state['max_icon_file_size'] = settings.MAX_ICON_FILE_SIZE
        state['realm_bot_domain'] = user_profile.realm.get_bot_domain()
        state['realm_uri'] = user_profile.realm.uri
        state['realm_presence_disabled'] = user_profile.realm.presence_disabled
        state['realm_show_digest_email'] = user_profile.realm.show_digest_email
        state['realm_is_zephyr_mirror_realm'] = user_profile.realm.is_zephyr_mirror_realm
        state['realm_email_auth_enabled'] = email_auth_enabled(user_profile.realm)
        state['realm_password_auth_enabled'] = password_auth_enabled(user_profile.realm)
        if user_profile.realm.notifications_stream and not user_profile.realm.notifications_stream.deactivated:
            notifications_stream = user_profile.realm.notifications_stream
            state['realm_notifications_stream_id'] = notifications_stream.id
        else:
            state['realm_notifications_stream_id'] = -1

    if want('realm_domains'):
        state['realm_domains'] = get_realm_domains(user_profile.realm)

    if want('realm_emoji'):
        state['realm_emoji'] = user_profile.realm.get_emoji()

    if want('realm_filters'):
        state['realm_filters'] = realm_filters_for_realm(user_profile.realm_id)

    if want('realm_user'):
        state['raw_users'] = get_raw_user_data(user_profile.realm_id)
        state['avatar_source'] = user_profile.avatar_source
        state['avatar_url_medium'] = avatar_url(user_profile, medium=True)
        state['avatar_url'] = avatar_url(user_profile)
        state['can_create_streams'] = user_profile.can_create_streams()
        state['cross_realm_bots'] = list(get_cross_realm_dicts())
        state['is_admin'] = user_profile.is_realm_admin
        state['user_id'] = user_profile.id
        state['enter_sends'] = user_profile.enter_sends
        state['email'] = user_profile.email
        state['full_name'] = user_profile.full_name

    if want('realm_bot'):
        state['realm_bots'] = get_owned_bot_dicts(user_profile)

    # This does not yet have an apply_event counterpart, since currently,
    # new entries for EMBEDDED_BOTS can only be added directly in the codebase.
    if want('realm_embedded_bots'):
        state['realm_embedded_bots'] = list(bot.name for bot in EMBEDDED_BOTS)

    if want('subscription'):
        subscriptions, unsubscribed, never_subscribed = gather_subscriptions_helper(
            user_profile, include_subscribers=include_subscribers)
        state['subscriptions'] = subscriptions
        state['unsubscribed'] = unsubscribed
        state['never_subscribed'] = never_subscribed

    if want('update_message_flags') and want('message'):
        # Keeping unread_msgs updated requires both message flag updates and
        # message updates. This is due to the fact that new messages will not
        # generate a flag update so we need to use the flags field in the
        # message event.
        state['raw_unread_msgs'] = get_raw_unread_data(user_profile)

    if want('stream'):
        state['streams'] = do_get_streams(user_profile)
    if want('default_streams'):
        state['realm_default_streams'] = streams_to_dicts_sorted(get_default_streams_for_realm(user_profile.realm_id))

    if want('update_display_settings'):
        for prop in UserProfile.property_types:
            state[prop] = getattr(user_profile, prop)
        state['emojiset_choices'] = user_profile.emojiset_choices()
        state['autoscroll_forever'] = user_profile.autoscroll_forever

    if want('update_global_notifications'):
        for notification in UserProfile.notification_setting_types:
            state[notification] = getattr(user_profile, notification)
        state['default_desktop_notifications'] = user_profile.default_desktop_notifications

    if want('zulip_version'):
        state['zulip_version'] = ZULIP_VERSION

    return state


def remove_message_id_from_unread_mgs(state, message_id):
    # type: (Dict[str, Dict[str, Any]], int) -> None
    raw_unread = state['raw_unread_msgs']

    for key in ['pm_dict', 'stream_dict', 'huddle_dict']:
        raw_unread[key].pop(message_id, None)

    raw_unread['unmuted_stream_msgs'].discard(message_id)
    raw_unread['mentions'].discard(message_id)

def apply_events(state, events, user_profile, include_subscribers=True,
                 fetch_event_types=None):
    # type: (Dict[str, Any], Iterable[Dict[str, Any]], UserProfile, bool, Optional[Iterable[str]]) -> None
    for event in events:
        if fetch_event_types is not None and event['type'] not in fetch_event_types:
            # TODO: continuing here is not, most precisely, correct.
            # In theory, an event of one type, e.g. `realm_user`,
            # could modify state that doesn't come from that
            # `fetch_event_types` value, e.g. the `our_person` part of
            # that code path.  But it should be extremely rare, and
            # fixing that will require a nontrivial refactor of
            # `apply_event`.  For now, be careful in your choice of
            # `fetch_event_types`.
            continue
        apply_event(state, event, user_profile, include_subscribers)

def apply_event(state, event, user_profile, include_subscribers):
    # type: (Dict[str, Any], Dict[str, Any], UserProfile, bool) -> None
    if event['type'] == "message":
        state['max_message_id'] = max(state['max_message_id'], event['message']['id'])
        if 'raw_unread_msgs' in state:
            apply_unread_message_event(
                user_profile,
                state['raw_unread_msgs'],
                event['message'],
                event['flags'],
            )

    elif event['type'] == "hotspots":
        state['hotspots'] = event['hotspots']
    elif event['type'] == "custom_profile_fields":
        state['custom_profile_fields'] = event['fields']
    elif event['type'] == "pointer":
        state['pointer'] = max(state['pointer'], event['pointer'])
    elif event['type'] == "realm_user":
        person = event['person']
        person_user_id = person['user_id']

        if event['op'] == "add":
            person = copy.deepcopy(person)
            person['is_active'] = True
            state['raw_users'][person_user_id] = person
        elif event['op'] == "remove":
            state['raw_users'][person_user_id]['is_active'] = False
        elif event['op'] == 'update':
            is_me = (person_user_id == user_profile.id)

            if is_me:
                if ('avatar_url' in person and 'avatar_url' in state):
                    state['avatar_source'] = person['avatar_source']
                    state['avatar_url'] = person['avatar_url']
                    state['avatar_url_medium'] = person['avatar_url_medium']

                for field in ['is_admin', 'email', 'full_name']:
                    if field in person and field in state:
                        state[field] = person[field]

                # In the unlikely event that the current user
                # just changed to/from being an admin, we need
                # to add/remove the data on all bots in the
                # realm.  This is ugly and probably better
                # solved by removing the all-realm-bots data
                # given to admin users from this flow.
                if ('is_admin' in person and 'realm_bots' in state):
                    prev_state = state['raw_users'][user_profile.id]
                    was_admin = prev_state['is_admin']
                    now_admin = person['is_admin']

                    if was_admin and not now_admin:
                        state['realm_bots'] = []
                    if not was_admin and now_admin:
                        state['realm_bots'] = get_owned_bot_dicts(user_profile)

            if person_user_id in state['raw_users']:
                p = state['raw_users'][person_user_id]
                for field in p:
                    if field in person:
                        p[field] = person[field]

    elif event['type'] == 'realm_bot':
        if event['op'] == 'add':
            state['realm_bots'].append(event['bot'])

        if event['op'] == 'remove':
            email = event['bot']['email']
            for bot in state['realm_bots']:
                if bot['email'] == email:
                    bot['is_active'] = False

        if event['op'] == 'update':
            for bot in state['realm_bots']:
                if bot['email'] == event['bot']['email']:
                    if 'owner_id' in event['bot']:
                        bot['owner'] = get_user_profile_by_id(event['bot']['owner_id']).email
                    else:
                        bot.update(event['bot'])

    elif event['type'] == 'stream':
        if event['op'] == 'create':
            for stream in event['streams']:
                if not stream['invite_only']:
                    stream_data = copy.deepcopy(stream)
                    if include_subscribers:
                        stream_data['subscribers'] = []
                    # Add stream to never_subscribed (if not invite_only)
                    state['never_subscribed'].append(stream_data)
                state['streams'].append(stream)
            state['streams'].sort(key=lambda elt: elt["name"])

        if event['op'] == 'delete':
            deleted_stream_ids = {stream['stream_id'] for stream in event['streams']}
            state['streams'] = [s for s in state['streams'] if s['stream_id'] not in deleted_stream_ids]
            state['never_subscribed'] = [stream for stream in state['never_subscribed'] if
                                         stream['stream_id'] not in deleted_stream_ids]

        if event['op'] == 'update':
            # For legacy reasons, we call stream data 'subscriptions' in
            # the state var here, for the benefit of the JS code.
            for obj in state['subscriptions']:
                if obj['name'].lower() == event['name'].lower():
                    obj[event['property']] = event['value']
            # Also update the pure streams data
            for stream in state['streams']:
                if stream['name'].lower() == event['name'].lower():
                    prop = event['property']
                    if prop in stream:
                        stream[prop] = event['value']
        elif event['op'] == "occupy":
            state['streams'] += event['streams']
        elif event['op'] == "vacate":
            stream_ids = [s["stream_id"] for s in event['streams']]
            state['streams'] = [s for s in state['streams'] if s["stream_id"] not in stream_ids]
    elif event['type'] == 'default_streams':
        state['realm_default_streams'] = event['default_streams']
    elif event['type'] == 'realm':
        if event['op'] == "update":
            field = 'realm_' + event['property']
            state[field] = event['value']

            # Tricky interaction: Whether we can create streams can get changed here.
            if (field in ['realm_create_stream_by_admins_only',
                          'realm_waiting_period_threshold']) and 'can_create_streams' in state:
                state['can_create_streams'] = user_profile.can_create_streams()
        elif event['op'] == "update_dict":
            for key, value in event['data'].items():
                state['realm_' + key] = value
                # It's a bit messy, but this is where we need to
                # update the state for whether password authentication
                # is enabled on this server.
                if key == 'authentication_methods':
                    state['realm_password_auth_enabled'] = (value['Email'] or value['LDAP'])
                    state['realm_email_auth_enabled'] = value['Email']
    elif event['type'] == "subscription":
        if not include_subscribers and event['op'] in ['peer_add', 'peer_remove']:
            return

        if event['op'] in ["add"]:
            if not include_subscribers:
                # Avoid letting 'subscribers' entries end up in the list
                for i, sub in enumerate(event['subscriptions']):
                    event['subscriptions'][i] = copy.deepcopy(event['subscriptions'][i])
                    del event['subscriptions'][i]['subscribers']

        def name(sub):
            # type: (Dict[str, Any]) -> Text
            return sub['name'].lower()

        if event['op'] == "add":
            added_names = set(map(name, event["subscriptions"]))
            was_added = lambda s: name(s) in added_names

            # add the new subscriptions
            state['subscriptions'] += event['subscriptions']

            # remove them from unsubscribed if they had been there
            state['unsubscribed'] = [s for s in state['unsubscribed'] if not was_added(s)]

            # remove them from never_subscribed if they had been there
            state['never_subscribed'] = [s for s in state['never_subscribed'] if not was_added(s)]

        elif event['op'] == "remove":
            removed_names = set(map(name, event["subscriptions"]))
            was_removed = lambda s: name(s) in removed_names

            # Find the subs we are affecting.
            removed_subs = list(filter(was_removed, state['subscriptions']))

            # Remove our user from the subscribers of the removed subscriptions.
            if include_subscribers:
                for sub in removed_subs:
                    sub['subscribers'] = [id for id in sub['subscribers'] if id != user_profile.id]

            # We must effectively copy the removed subscriptions from subscriptions to
            # unsubscribe, since we only have the name in our data structure.
            state['unsubscribed'] += removed_subs

            # Now filter out the removed subscriptions from subscriptions.
            state['subscriptions'] = [s for s in state['subscriptions'] if not was_removed(s)]

        elif event['op'] == 'update':
            for sub in state['subscriptions']:
                if sub['name'].lower() == event['name'].lower():
                    sub[event['property']] = event['value']
        elif event['op'] == 'peer_add':
            user_id = event['user_id']
            for sub in state['subscriptions']:
                if (sub['name'] in event['subscriptions'] and
                        user_id not in sub['subscribers']):
                    sub['subscribers'].append(user_id)
            for sub in state['never_subscribed']:
                if (sub['name'] in event['subscriptions'] and
                        user_id not in sub['subscribers']):
                    sub['subscribers'].append(user_id)
        elif event['op'] == 'peer_remove':
            user_id = event['user_id']
            for sub in state['subscriptions']:
                if (sub['name'] in event['subscriptions'] and
                        user_id in sub['subscribers']):
                    sub['subscribers'].remove(user_id)
    elif event['type'] == "presence":
        # TODO: Add user_id to presence update events / state format!
        presence_user_profile = get_user(event['email'], user_profile.realm)
        state['presences'][event['email']] = UserPresence.get_status_dict_by_user(
            presence_user_profile)[event['email']]
    elif event['type'] == "update_message":
        # We don't return messages in /register, so we don't need to
        # do anything for content updates, but we may need to update
        # the unread_msgs data if the topic of an unread message changed.
        if 'subject' in event:
            stream_dict = state['raw_unread_msgs']['stream_dict']
            topic = event['subject']
            for message_id in event['message_ids']:
                if message_id in stream_dict:
                    stream_dict[message_id]['topic'] = topic
    elif event['type'] == "delete_message":
        max_message = Message.objects.filter(
            usermessage__user_profile=user_profile).order_by('-id').first()
        if max_message:
            state['max_message_id'] = max_message.id
        else:
            state['max_message_id'] = -1

        remove_id = event['message_id']
        remove_message_id_from_unread_mgs(state, remove_id)
    elif event['type'] == "reaction":
        # The client will get the message with the reactions directly
        pass
    elif event['type'] == 'typing':
        # Typing notification events are transient and thus ignored
        pass
    elif event['type'] == "update_message_flags":
        # We don't return messages in `/register`, so most flags we
        # can ignore, but we do need to update the unread_msgs data if
        # unread state is changed.
        if event['flag'] == 'read' and event['operation'] == 'add':
            for remove_id in event['messages']:
                remove_message_id_from_unread_mgs(state, remove_id)
    elif event['type'] == "realm_domains":
        if event['op'] == 'add':
            state['realm_domains'].append(event['realm_domain'])
        elif event['op'] == 'change':
            for realm_domain in state['realm_domains']:
                if realm_domain['domain'] == event['realm_domain']['domain']:
                    realm_domain['allow_subdomains'] = event['realm_domain']['allow_subdomains']
        elif event['op'] == 'remove':
            state['realm_domains'] = [realm_domain for realm_domain in state['realm_domains']
                                      if realm_domain['domain'] != event['domain']]
    elif event['type'] == "realm_emoji":
        state['realm_emoji'] = event['realm_emoji']
    elif event['type'] == "alert_words":
        state['alert_words'] = event['alert_words']
    elif event['type'] == "muted_topics":
        state['muted_topics'] = event["muted_topics"]
    elif event['type'] == "realm_filters":
        state['realm_filters'] = event["realm_filters"]
    elif event['type'] == "update_display_settings":
        assert event['setting_name'] in UserProfile.property_types
        state[event['setting_name']] = event['setting']
    elif event['type'] == "update_global_notifications":
        assert event['notification_name'] in UserProfile.notification_setting_types
        state[event['notification_name']] = event['setting']
    else:
        raise AssertionError("Unexpected event type %s" % (event['type'],))

def do_events_register(user_profile, user_client, apply_markdown=True,
                       event_types=None, queue_lifespan_secs=0, all_public_streams=False,
                       include_subscribers=True, narrow=[], fetch_event_types=None):
    # type: (UserProfile, Client, bool, Optional[Iterable[str]], int, bool, bool, Iterable[Sequence[Text]], Optional[Iterable[str]]) -> Dict[str, Any]

    # Technically we don't need to check this here because
    # build_narrow_filter will check it, but it's nicer from an error
    # handling perspective to do it before contacting Tornado
    check_supported_events_narrow_filter(narrow)

    # Note that we pass event_types, not fetch_event_types here, since
    # that's what controls which future events are sent.
    queue_id = request_event_queue(user_profile, user_client, apply_markdown,
                                   queue_lifespan_secs, event_types, all_public_streams,
                                   narrow=narrow)

    if queue_id is None:
        raise JsonableError(_("Could not allocate event queue"))

    if fetch_event_types is not None:
        event_types_set = set(fetch_event_types)  # type: Optional[Set[str]]
    elif event_types is not None:
        event_types_set = set(event_types)
    else:
        event_types_set = None

    # Fill up the UserMessage rows if a soft-deactivated user has returned
    maybe_catch_up_soft_deactivated_user(user_profile)

    ret = fetch_initial_state_data(user_profile, event_types_set, queue_id,
                                   include_subscribers=include_subscribers)

    # Apply events that came in while we were fetching initial data
    events = get_user_events(user_profile, queue_id, -1)
    apply_events(ret, events, user_profile, include_subscribers=include_subscribers,
                 fetch_event_types=fetch_event_types)

    '''
    NOTE:

    Below is an example of post-processing initial state data AFTER we
    apply events.  For large payloads like `unread_msgs`, it's helpful
    to have an intermediate data structure that is easy to manipulate
    with O(1)-type operations as we apply events.

    Then, only at the end, we put it in the form that's more appropriate
    for client.
    '''
    if 'raw_unread_msgs' in ret:
        ret['unread_msgs'] = aggregate_unread_data(ret['raw_unread_msgs'])
        del ret['raw_unread_msgs']

    '''
    See the note above; the same technique applies below.
    '''
    if 'raw_users'in ret:
        user_dicts = list(ret['raw_users'].values())

        ret['realm_users'] = [d for d in user_dicts if d['is_active']]
        ret['realm_non_active_users'] = [d for d in user_dicts if not d['is_active']]

        '''
        Be aware that we do intentional aliasing in the below code.
        We can now safely remove the `is_active` field from all the
        dicts that got partitioned into the two lists above.

        We remove the field because it's already implied, and sending
        it to clients makes clients prone to bugs where they "trust"
        the field but don't actually update in live updates.  It also
        wastes bandwidth.
        '''
        for d in user_dicts:
            d.pop('is_active')

        del ret['raw_users']

    if len(events) > 0:
        ret['last_event_id'] = events[-1]['id']
    else:
        ret['last_event_id'] = -1
    return ret
