zulip/zerver/actions/message_edit.py

import itertools
from collections import defaultdict
from datetime import timedelta
from typing import AbstractSet, Any, Dict, Iterable, List, Optional, Set, Tuple

from django.conf import settings
from django.db import transaction
from django.db.models import Q
from django.utils.timezone import now as timezone_now
from django.utils.translation import gettext as _
from django.utils.translation import gettext_lazy
from django.utils.translation import override as override_language
from django_stubs_ext import StrPromise

from zerver.actions.message_delete import DeleteMessagesEvent
from zerver.actions.message_flags import do_update_mobile_push_notification
from zerver.actions.message_send import (
    filter_presence_idle_user_ids,
    get_recipient_info,
    internal_send_stream_message,
    render_incoming_message,
)
from zerver.actions.uploads import check_attachment_reference_change
from zerver.actions.user_topics import bulk_do_set_user_topic_visibility_policy
from zerver.lib.exceptions import (
    JsonableError,
    MessageMoveError,
    StreamWildcardMentionNotAllowedError,
    TopicWildcardMentionNotAllowedError,
)
from zerver.lib.markdown import MessageRenderingResult, topic_links
from zerver.lib.markdown import version as markdown_version
from zerver.lib.mention import MentionBackend, MentionData, silent_mention_syntax_for_user
from zerver.lib.message import (
    access_message,
    bulk_access_messages,
    check_user_group_mention_allowed,
    normalize_body,
    stream_wildcard_mention_allowed,
    topic_wildcard_mention_allowed,
    truncate_topic,
    update_to_dict_cache,
)
from zerver.lib.queue import queue_json_publish
from zerver.lib.stream_subscription import get_active_subscriptions_for_stream_id
from zerver.lib.stream_topic import StreamTopicTarget
from zerver.lib.streams import (
    access_stream_by_id,
    can_access_stream_history,
    check_stream_access_based_on_stream_post_policy,
)
from zerver.lib.string_validation import check_stream_topic
from zerver.lib.timestamp import datetime_to_timestamp
from zerver.lib.topic import (
    ORIG_TOPIC,
    RESOLVED_TOPIC_PREFIX,
    TOPIC_LINKS,
    TOPIC_NAME,
    messages_for_topic,
    participants_for_topic,
    save_message_for_edit_use_case,
    update_edit_history,
    update_messages_for_topic_edit,
)
from zerver.lib.types import EditHistoryEvent
from zerver.lib.url_encoding import near_stream_message_url
from zerver.lib.user_message import UserMessageLite, bulk_insert_ums
from zerver.lib.user_topics import get_users_with_user_topic_visibility_policy
from zerver.lib.widget import is_widget_message
from zerver.models import (
    ArchivedAttachment,
    Attachment,
    Message,
    Reaction,
    Stream,
    UserMessage,
    UserProfile,
    UserTopic,
)
from zerver.models.streams import get_stream_by_id_in_realm
from zerver.models.users import get_system_bot
from zerver.tornado.django_api import send_event


def subscriber_info(user_id: int) -> Dict[str, Any]:
    return {"id": user_id, "flags": ["read"]}


def validate_message_edit_payload(
    message: Message,
    stream_id: Optional[int],
    topic_name: Optional[str],
    propagate_mode: Optional[str],
    content: Optional[str],
) -> None:
    """
    Checks that the data sent is well-formed. Does not handle editability, permissions etc.
    """
    if topic_name is None and content is None and stream_id is None:
        raise JsonableError(_("Nothing to change"))

    if not message.is_stream_message():
        if stream_id is not None:
            raise JsonableError(_("Direct messages cannot be moved to streams."))
        if topic_name is not None:
            raise JsonableError(_("Direct messages cannot have topics."))

    if propagate_mode != "change_one" and topic_name is None and stream_id is None:
        raise JsonableError(_("Invalid propagate_mode without topic edit"))

    if topic_name is not None:
        check_stream_topic(topic_name)

    if stream_id is not None and content is not None:
        raise JsonableError(_("Cannot change message content while changing stream"))

    # Right now, we prevent users from editing widgets.
    if content is not None and is_widget_message(message):
        raise JsonableError(_("Widgets cannot be edited."))


def maybe_send_resolve_topic_notifications(
    *,
    user_profile: UserProfile,
    stream: Stream,
    old_topic_name: str,
    new_topic_name: str,
    changed_messages: List[Message],
) -> Optional[int]:
    """Returns resolved_topic_message_id if resolve topic notifications were in fact sent."""
    # Note that topics will have already been stripped in check_update_message.
    #
    # This logic is designed to treat removing a weird "✔ ✔✔ "
    # prefix as unresolving the topic.
    topic_resolved: bool = new_topic_name.startswith(
        RESOLVED_TOPIC_PREFIX
    ) and not old_topic_name.startswith(RESOLVED_TOPIC_PREFIX)
    topic_unresolved: bool = old_topic_name.startswith(
        RESOLVED_TOPIC_PREFIX
    ) and not new_topic_name.startswith(RESOLVED_TOPIC_PREFIX)

    if not topic_resolved and not topic_unresolved:
        # If there's some other weird topic that does not toggle the
        # state of "topic starts with RESOLVED_TOPIC_PREFIX", we do
        # nothing. Any other logic could result in cases where we send
        # these notifications in a non-alternating fashion.
        #
        # Note that it is still possible for an individual topic to
        # have multiple "This topic was marked as resolved"
        # notifications in a row: one can send new messages to the
        # pre-resolve topic and then resolve the topic created that
        # way to get multiple in the resolved topic. And then an
        # administrator can the messages in between. We consider this
        # to be a fundamental risk of irresponsible message deletion,
        # not a bug with the "resolve topics" feature.
        return None

    # Compute the users who either sent or reacted to messages that
    # were moved via the "resolve topic' action. Only those users
    # should be eligible for this message being managed as unread.
    affected_participant_ids = {message.sender_id for message in changed_messages} | set(
        Reaction.objects.filter(message__in=changed_messages).values_list(
            "user_profile_id", flat=True
        )
    )
    sender = get_system_bot(settings.NOTIFICATION_BOT, user_profile.realm_id)
    user_mention = silent_mention_syntax_for_user(user_profile)
    with override_language(stream.realm.default_language):
        if topic_resolved:
            notification_string = _("{user} has marked this topic as resolved.")
        elif topic_unresolved:
            notification_string = _("{user} has marked this topic as unresolved.")

        resolved_topic_message_id = internal_send_stream_message(
            sender,
            stream,
            new_topic_name,
            notification_string.format(
                user=user_mention,
            ),
            limit_unread_user_ids=affected_participant_ids,
        )

    return resolved_topic_message_id


def send_message_moved_breadcrumbs(
    target_message: Message,
    user_profile: UserProfile,
    old_stream: Stream,
    old_topic_name: str,
    old_thread_notification_string: Optional[StrPromise],
    new_stream: Stream,
    new_topic_name: Optional[str],
    new_thread_notification_string: Optional[StrPromise],
    changed_messages_count: int,
) -> None:
    # Since moving content between streams is highly disruptive,
    # it's worth adding a couple tombstone messages showing what
    # happened.
    sender = get_system_bot(settings.NOTIFICATION_BOT, old_stream.realm_id)

    if new_topic_name is None:
        new_topic_name = old_topic_name

    user_mention = silent_mention_syntax_for_user(user_profile)
    old_topic_link = f"#**{old_stream.name}>{old_topic_name}**"
    new_topic_link = f"#**{new_stream.name}>{new_topic_name}**"
    message = {
        "id": target_message.id,
        "stream_id": new_stream.id,
        "display_recipient": new_stream.name,
        "topic": new_topic_name,
    }
    moved_message_link = near_stream_message_url(target_message.realm, message)

    if new_thread_notification_string is not None:
        with override_language(new_stream.realm.default_language):
            internal_send_stream_message(
                sender,
                new_stream,
                new_topic_name,
                new_thread_notification_string.format(
                    message_link=moved_message_link,
                    old_location=old_topic_link,
                    user=user_mention,
                    changed_messages_count=changed_messages_count,
                ),
            )

    if old_thread_notification_string is not None:
        with override_language(old_stream.realm.default_language):
            # Send a notification to the old stream that the topic was moved.
            internal_send_stream_message(
                sender,
                old_stream,
                old_topic_name,
                old_thread_notification_string.format(
                    user=user_mention,
                    new_location=new_topic_link,
                    changed_messages_count=changed_messages_count,
                ),
            )


def get_mentions_for_message_updates(message_id: int) -> Set[int]:
    # We exclude UserMessage.flags.historical rows since those
    # users did not receive the message originally, and thus
    # probably are not relevant for reprocessed alert_words,
    # mentions and similar rendering features.  This may be a
    # decision we change in the future.
    mentioned_user_ids = (
        UserMessage.objects.filter(
            message=message_id,
            flags=~UserMessage.flags.historical,
        )
        .filter(
            Q(
                flags__andnz=UserMessage.flags.mentioned
                | UserMessage.flags.stream_wildcard_mentioned
                | UserMessage.flags.topic_wildcard_mentioned
                | UserMessage.flags.group_mentioned
            )
        )
        .values_list("user_profile_id", flat=True)
    )
    return set(mentioned_user_ids)


def update_user_message_flags(
    rendering_result: MessageRenderingResult,
    ums: Iterable[UserMessage],
    topic_participant_user_ids: AbstractSet[int] = set(),
) -> None:
    mentioned_ids = rendering_result.mentions_user_ids
    ids_with_alert_words = rendering_result.user_ids_with_alert_words
    changed_ums: Set[UserMessage] = set()

    def update_flag(um: UserMessage, should_set: bool, flag: int) -> None:
        if should_set:
            if not (um.flags & flag):
                um.flags |= flag
                changed_ums.add(um)
        else:
            if um.flags & flag:
                um.flags &= ~flag
                changed_ums.add(um)

    for um in ums:
        has_alert_word = um.user_profile_id in ids_with_alert_words
        update_flag(um, has_alert_word, UserMessage.flags.has_alert_word)

        mentioned = um.user_profile_id in mentioned_ids
        update_flag(um, mentioned, UserMessage.flags.mentioned)

        if rendering_result.mentions_stream_wildcard:
            update_flag(um, True, UserMessage.flags.stream_wildcard_mentioned)
        elif rendering_result.mentions_topic_wildcard:
            topic_wildcard_mentioned = um.user_profile_id in topic_participant_user_ids
            update_flag(um, topic_wildcard_mentioned, UserMessage.flags.topic_wildcard_mentioned)

    for um in changed_ums:
        um.save(update_fields=["flags"])


def do_update_embedded_data(
    user_profile: UserProfile,
    message: Message,
    content: Optional[str],
    rendering_result: MessageRenderingResult,
) -> None:
    timestamp = timezone_now()
    event: Dict[str, Any] = {
        "type": "update_message",
        "user_id": None,
        "edit_timestamp": datetime_to_timestamp(timestamp),
        "message_id": message.id,
        "rendering_only": True,
    }
    changed_messages = [message]
    rendered_content: Optional[str] = None

    ums = UserMessage.objects.filter(message=message.id)

    if content is not None:
        update_user_message_flags(rendering_result, ums)
        rendered_content = rendering_result.rendered_content
        message.rendered_content = rendered_content
        message.rendered_content_version = markdown_version
        event["content"] = content
        event["rendered_content"] = rendered_content

    message.save(update_fields=["content", "rendered_content"])

    event["message_ids"] = update_to_dict_cache(changed_messages)

    def user_info(um: UserMessage) -> Dict[str, Any]:
        return {
            "id": um.user_profile_id,
            "flags": um.flags_list(),
        }

    send_event(user_profile.realm, event, list(map(user_info, ums)))


def get_visibility_policy_after_merge(
    orig_topic_visibility_policy: int, target_topic_visibility_policy: int
) -> int:
    # This function determines the final visibility_policy after the merge
    # operation, based on the visibility policies of the original and target
    # topics.
    #
    # The algorithm to decide is based on:
    # Whichever of the two policies is most visible is what we keep.
    # The general motivation is to err on the side of showing messages
    # rather than hiding them.
    if orig_topic_visibility_policy == target_topic_visibility_policy:
        return orig_topic_visibility_policy
    elif UserTopic.VisibilityPolicy.UNMUTED in (
        orig_topic_visibility_policy,
        target_topic_visibility_policy,
    ):
        return UserTopic.VisibilityPolicy.UNMUTED
    return UserTopic.VisibilityPolicy.INHERIT


# This must be called already in a transaction, with a write lock on
# the target_message.
@transaction.atomic(savepoint=False)
def do_update_message(
    user_profile: UserProfile,
    target_message: Message,
    new_stream: Optional[Stream],
    topic_name: Optional[str],
    propagate_mode: Optional[str],
    send_notification_to_old_thread: bool,
    send_notification_to_new_thread: bool,
    content: Optional[str],
    rendering_result: Optional[MessageRenderingResult],
    prior_mention_user_ids: Set[int],
    mention_data: Optional[MentionData] = None,
) -> int:
    """
    The main function for message editing.  A message edit event can
    modify:
    * the message's content (in which case the caller will have
      set both content and rendered_content),
    * the topic, in which case the caller will have set topic_name
    * or both message's content and the topic
    * or stream and/or topic, in which case the caller will have set
        new_stream and/or topic_name.

    With topic edits, propagate_mode determines whether other message
    also have their topics edited.
    """
    timestamp = timezone_now()
    target_message.last_edit_time = timestamp

    event: Dict[str, Any] = {
        "type": "update_message",
        "user_id": user_profile.id,
        "edit_timestamp": datetime_to_timestamp(timestamp),
        "message_id": target_message.id,
        "rendering_only": False,
    }

    edit_history_event: EditHistoryEvent = {
        "user_id": user_profile.id,
        "timestamp": event["edit_timestamp"],
    }

    changed_messages = [target_message]

    realm = user_profile.realm

    stream_being_edited = None
    if target_message.is_stream_message():
        stream_id = target_message.recipient.type_id
        stream_being_edited = get_stream_by_id_in_realm(stream_id, realm)
        event["stream_name"] = stream_being_edited.name
        event["stream_id"] = stream_being_edited.id

    ums = UserMessage.objects.filter(message=target_message.id)

    if content is not None:
        assert rendering_result is not None

        # mention_data is required if there's a content edit.
        assert mention_data is not None

        # add data from group mentions to mentions_user_ids.
        for group_id in rendering_result.mentions_user_group_ids:
            members = mention_data.get_group_members(group_id)
            rendering_result.mentions_user_ids.update(members)

        # One could imagine checking realm.allow_edit_history here and
        # modifying the events based on that setting, but doing so
        # doesn't really make sense.  We need to send the edit event
        # to clients regardless, and a client already had access to
        # the original/pre-edit content of the message anyway.  That
        # setting must be enforced on the client side, and making a
        # change here simply complicates the logic for clients parsing
        # edit history events.
        event["orig_content"] = target_message.content
        event["orig_rendered_content"] = target_message.rendered_content
        edit_history_event["prev_content"] = target_message.content
        edit_history_event["prev_rendered_content"] = target_message.rendered_content
        edit_history_event["prev_rendered_content_version"] = (
            target_message.rendered_content_version
        )
        target_message.content = content
        target_message.rendered_content = rendering_result.rendered_content
        target_message.rendered_content_version = markdown_version
        event["content"] = content
        event["rendered_content"] = rendering_result.rendered_content
        event["prev_rendered_content_version"] = target_message.rendered_content_version
        event["is_me_message"] = Message.is_status_message(
            content, rendering_result.rendered_content
        )

        # target_message.has_image and target_message.has_link will have been
        # already updated by Markdown rendering in the caller.
        target_message.has_attachment = check_attachment_reference_change(
            target_message, rendering_result
        )

        if target_message.is_stream_message():
            if topic_name is not None:
                new_topic_name = topic_name
            else:
                new_topic_name = target_message.topic_name()

            stream_topic: Optional[StreamTopicTarget] = StreamTopicTarget(
                stream_id=stream_id,
                topic_name=new_topic_name,
            )
        else:
            stream_topic = None

        info = get_recipient_info(
            realm_id=realm.id,
            recipient=target_message.recipient,
            sender_id=target_message.sender_id,
            stream_topic=stream_topic,
            possible_topic_wildcard_mention=mention_data.message_has_topic_wildcards(),
            possible_stream_wildcard_mention=mention_data.message_has_stream_wildcards(),
        )

        event["online_push_user_ids"] = list(info.online_push_user_ids)
        event["dm_mention_push_disabled_user_ids"] = list(info.dm_mention_push_disabled_user_ids)
        event["dm_mention_email_disabled_user_ids"] = list(info.dm_mention_email_disabled_user_ids)
        event["stream_push_user_ids"] = list(info.stream_push_user_ids)
        event["stream_email_user_ids"] = list(info.stream_email_user_ids)
        event["followed_topic_push_user_ids"] = list(info.followed_topic_push_user_ids)
        event["followed_topic_email_user_ids"] = list(info.followed_topic_email_user_ids)
        event["muted_sender_user_ids"] = list(info.muted_sender_user_ids)
        event["prior_mention_user_ids"] = list(prior_mention_user_ids)
        event["presence_idle_user_ids"] = filter_presence_idle_user_ids(info.active_user_ids)
        event["all_bot_user_ids"] = list(info.all_bot_user_ids)
        if rendering_result.mentions_stream_wildcard:
            event["stream_wildcard_mention_user_ids"] = list(info.stream_wildcard_mention_user_ids)
            event["stream_wildcard_mention_in_followed_topic_user_ids"] = list(
                info.stream_wildcard_mention_in_followed_topic_user_ids
            )
        else:
            event["stream_wildcard_mention_user_ids"] = []
            event["stream_wildcard_mention_in_followed_topic_user_ids"] = []

        if rendering_result.mentions_topic_wildcard:
            event["topic_wildcard_mention_user_ids"] = list(info.topic_wildcard_mention_user_ids)
            event["topic_wildcard_mention_in_followed_topic_user_ids"] = list(
                info.topic_wildcard_mention_in_followed_topic_user_ids
            )
            topic_participant_user_ids = info.topic_participant_user_ids
        else:
            event["topic_wildcard_mention_user_ids"] = []
            event["topic_wildcard_mention_in_followed_topic_user_ids"] = []
            topic_participant_user_ids = set()

        update_user_message_flags(rendering_result, ums, topic_participant_user_ids)

        do_update_mobile_push_notification(
            target_message,
            prior_mention_user_ids,
            rendering_result.mentions_user_ids,
            info.stream_push_user_ids,
        )

    if topic_name is not None or new_stream is not None:
        assert propagate_mode is not None
        orig_topic_name = target_message.topic_name()
        event["propagate_mode"] = propagate_mode

    losing_access_user_ids: List[int] = []
    if new_stream is not None:
        assert content is None
        assert target_message.is_stream_message()
        assert stream_being_edited is not None

        edit_history_event["prev_stream"] = stream_being_edited.id
        edit_history_event["stream"] = new_stream.id
        event[ORIG_TOPIC] = orig_topic_name
        assert new_stream.recipient_id is not None
        target_message.recipient_id = new_stream.recipient_id

        event["new_stream_id"] = new_stream.id
        event["propagate_mode"] = propagate_mode

        # When messages are moved from one stream to another, some
        # users may lose access to those messages, including guest
        # users and users not subscribed to the new stream (if it is a
        # private stream).  For those users, their experience is as
        # though the messages were deleted, and we should send a
        # delete_message event to them instead.

        subs_to_old_stream = get_active_subscriptions_for_stream_id(
            stream_id, include_deactivated_users=True
        ).select_related("user_profile")
        subs_to_new_stream = list(
            get_active_subscriptions_for_stream_id(
                new_stream.id, include_deactivated_users=True
            ).select_related("user_profile")
        )

        old_stream_user_ids = {user.user_profile_id for user in subs_to_old_stream}
        new_stream_user_ids = {user.user_profile_id for user in subs_to_new_stream}

        # Get users who aren't subscribed to the new_stream.
        subs_losing_usermessages = [
            sub for sub in subs_to_old_stream if sub.user_profile_id not in new_stream_user_ids
        ]
        # Users who can longer access the message without some action
        # from administrators.
        subs_losing_access = [
            sub
            for sub in subs_losing_usermessages
            if sub.user_profile.is_guest or not new_stream.is_public()
        ]
        losing_access_user_ids = [sub.user_profile_id for sub in subs_losing_access]

        ums = ums.exclude(
            user_profile_id__in=[sub.user_profile_id for sub in subs_losing_usermessages]
        )

        gaining_usermessage_user_ids = []
        if not new_stream.is_history_public_to_subscribers():
            # For private streams, with history not public to subscribers,
            # We find out users who are not present in the msgs' old stream
            # and create new UserMessage for these users so that they can
            # access this message.
            gaining_usermessage_user_ids += [
                user_id for user_id in new_stream_user_ids if user_id not in old_stream_user_ids
            ]

    # We save the full topic name so that checks that require comparison
    # between the original topic and the topic name passed into this function
    # will not be affected by the potential truncation of topic_name below.
    pre_truncation_topic_name = topic_name
    if topic_name is not None:
        topic_name = truncate_topic(topic_name)
        target_message.set_topic_name(topic_name)

        # These fields have legacy field names.
        event[ORIG_TOPIC] = orig_topic_name
        event[TOPIC_NAME] = topic_name
        event[TOPIC_LINKS] = topic_links(target_message.realm_id, topic_name)
        edit_history_event["prev_topic"] = orig_topic_name
        edit_history_event["topic"] = topic_name

    update_edit_history(target_message, timestamp, edit_history_event)

    # 'target_topic_has_messages', 'target_stream', and 'target_topic'
    # will be used while migrating user_topic records later in this function.
    #
    # We need to calculate 'target_topic_has_messages' here,
    # as we are moving the messages in the next step.
    if topic_name is not None or new_stream is not None:
        assert stream_being_edited is not None
        assert orig_topic_name is not None

        target_stream: Stream = new_stream if new_stream is not None else stream_being_edited
        target_topic_name: str = topic_name if topic_name is not None else orig_topic_name

        assert target_stream.recipient_id is not None
        target_topic_has_messages = messages_for_topic(
            realm.id, target_stream.recipient_id, target_topic_name
        ).exists()

    if propagate_mode in ["change_later", "change_all"]:
        assert topic_name is not None or new_stream is not None
        assert stream_being_edited is not None

        # Other messages should only get topic/stream fields in their edit history.
        topic_only_edit_history_event: EditHistoryEvent = {
            "user_id": edit_history_event["user_id"],
            "timestamp": edit_history_event["timestamp"],
        }
        if topic_name is not None:
            topic_only_edit_history_event["prev_topic"] = edit_history_event["prev_topic"]
            topic_only_edit_history_event["topic"] = edit_history_event["topic"]
        if new_stream is not None:
            topic_only_edit_history_event["prev_stream"] = edit_history_event["prev_stream"]
            topic_only_edit_history_event["stream"] = edit_history_event["stream"]

        messages_list = update_messages_for_topic_edit(
            acting_user=user_profile,
            edited_message=target_message,
            propagate_mode=propagate_mode,
            orig_topic_name=orig_topic_name,
            topic_name=topic_name,
            new_stream=new_stream,
            old_stream=stream_being_edited,
            edit_history_event=topic_only_edit_history_event,
            last_edit_time=timestamp,
        )
        changed_messages += messages_list

        if new_stream is not None:
            assert stream_being_edited is not None
            changed_message_ids = [msg.id for msg in changed_messages]

            if gaining_usermessage_user_ids:
                ums_to_create = []
                for message_id in changed_message_ids:
                    for user_profile_id in gaining_usermessage_user_ids:
                        # The fact that the user didn't have a UserMessage originally means we can infer that the user
                        # was not mentioned in the original message (even if mention syntax was present, it would not
                        # take effect for a user who was not subscribed). If we were editing the message's content, we
                        # would rerender the message and then use the new stream's data to determine whether this is
                        # a mention of a subscriber; but as we are not doing so, we choose to preserve the "was this
                        # mention syntax an actual mention" decision made during the original rendering for implementation
                        # simplicity. As a result, the only flag to consider applying here is read.
                        um = UserMessageLite(
                            user_profile_id=user_profile_id,
                            message_id=message_id,
                            flags=UserMessage.flags.read,
                        )
                        ums_to_create.append(um)
                bulk_insert_ums(ums_to_create)

            # Delete UserMessage objects for users who will no
            # longer have access to these messages.  Note: This could be
            # very expensive, since it's N guest users x M messages.
            UserMessage.objects.filter(
                user_profile_id__in=[sub.user_profile_id for sub in subs_losing_usermessages],
                message_id__in=changed_message_ids,
            ).delete()

            delete_event: DeleteMessagesEvent = {
                "type": "delete_message",
                "message_ids": changed_message_ids,
                "message_type": "stream",
                "stream_id": stream_being_edited.id,
                "topic": orig_topic_name,
            }
            send_event(user_profile.realm, delete_event, losing_access_user_ids)

            # Reset the Attachment.is_*_public caches for all messages
            # moved to another stream with different access permissions.
            if new_stream.invite_only != stream_being_edited.invite_only:
                Attachment.objects.filter(messages__in=changed_message_ids).update(
                    is_realm_public=None,
                )
                ArchivedAttachment.objects.filter(messages__in=changed_message_ids).update(
                    is_realm_public=None,
                )

            if new_stream.is_web_public != stream_being_edited.is_web_public:
                Attachment.objects.filter(messages__in=changed_message_ids).update(
                    is_web_public=None,
                )
                ArchivedAttachment.objects.filter(messages__in=changed_message_ids).update(
                    is_web_public=None,
                )

    # This does message.save(update_fields=[...])
    save_message_for_edit_use_case(message=target_message)

    realm_id: Optional[int] = None
    if stream_being_edited is not None:
        realm_id = stream_being_edited.realm_id

    event["message_ids"] = update_to_dict_cache(changed_messages, realm_id)

    def user_info(um: UserMessage) -> Dict[str, Any]:
        return {
            "id": um.user_profile_id,
            "flags": um.flags_list(),
        }

    # The following blocks arranges that users who are subscribed to a
    # stream and can see history from before they subscribed get
    # live-update when old messages are edited (e.g. if the user does
    # a topic edit themself).
    #
    # We still don't send an update event to users who are not
    # subscribed to this stream and don't have a UserMessage row. This
    # means if a non-subscriber is viewing the narrow, they won't get
    # a real-time updates. This is a balance between sending
    # message-edit notifications for every public stream to every user
    # in the organization (too expansive, and also not what we do for
    # newly sent messages anyway) and having magical live-updates
    # where possible.
    users_to_be_notified = list(map(user_info, ums))
    if stream_being_edited is not None and stream_being_edited.is_history_public_to_subscribers():
        subscriptions = get_active_subscriptions_for_stream_id(
            stream_id, include_deactivated_users=False
        )
        # We exclude long-term idle users, since they by
        # definition have no active clients.
        subscriptions = subscriptions.exclude(user_profile__long_term_idle=True)
        # Remove duplicates by excluding the id of users already
        # in users_to_be_notified list.  This is the case where a
        # user both has a UserMessage row and is a current
        # Subscriber
        subscriptions = subscriptions.exclude(
            user_profile_id__in=[um.user_profile_id for um in ums]
        )

        if new_stream is not None:
            subscriptions = subscriptions.exclude(user_profile_id__in=losing_access_user_ids)

        # All users that are subscribed to the stream must be
        # notified when a message is edited
        subscriber_ids = set(subscriptions.values_list("user_profile_id", flat=True))

        if new_stream is not None:
            # TODO: Guest users don't see the new moved topic
            # unless breadcrumb message for new stream is
            # enabled. Excluding these users from receiving this
            # event helps us avoid a error traceback for our
            # clients. We should figure out a way to inform the
            # guest users of this new topic if sending a 'message'
            # event for these messages is not an option.
            #
            # Don't send this event to guest subs who are not
            # subscribers of the old stream but are subscribed to
            # the new stream; clients will be confused.
            old_stream_unsubbed_guests = [
                sub
                for sub in subs_to_new_stream
                if sub.user_profile.is_guest and sub.user_profile_id not in subscriber_ids
            ]
            subscriptions = subscriptions.exclude(
                user_profile_id__in=[sub.user_profile_id for sub in old_stream_unsubbed_guests]
            )
            subscriber_ids = set(subscriptions.values_list("user_profile_id", flat=True))

        users_to_be_notified += map(subscriber_info, sorted(subscriber_ids))

    # UserTopic updates and the content of notifications depend on
    # whether we've moved the entire topic, or just part of it. We
    # make that determination here.
    moved_all_visible_messages = False
    if topic_name is not None or new_stream is not None:
        assert stream_being_edited is not None

        if propagate_mode == "change_all":
            moved_all_visible_messages = True
        else:
            # With other propagate modes, if the user in fact moved
            # all messages in the stream, we want to explain it was a
            # full-topic move.
            #
            # For security model reasons, we don't want to allow a
            # user to take any action that would leak information
            # about older messages they cannot access (E.g. the only
            # remaining messages are in a stream without shared
            # history). The bulk_access_messages call below addresses
            # that concern.
            #
            # bulk_access_messages is inefficient for this task, since
            # we just want to do the exists() version of this
            # query. But it's nice to reuse code, and this bulk
            # operation is likely cheaper than a `GET /messages`
            # unless the topic has thousands of messages of history.
            assert stream_being_edited.recipient_id is not None
            unmoved_messages = messages_for_topic(
                realm.id,
                stream_being_edited.recipient_id,
                orig_topic_name,
            )
            visible_unmoved_messages = bulk_access_messages(
                user_profile, unmoved_messages, stream=stream_being_edited
            )
            moved_all_visible_messages = len(visible_unmoved_messages) == 0

    # Migrate 'topic with visibility_policy' configuration in the following
    # circumstances:
    #
    # * If propagate_mode is change_all, do so unconditionally.
    #
    # * If propagate_mode is change_later or change_one, do so when
    #   the acting user has moved the entire topic (as visible to them).
    #
    # This rule corresponds to checking moved_all_visible_messages.
    if moved_all_visible_messages:
        assert stream_being_edited is not None
        assert target_stream is not None
        assert target_topic_name is not None

        stream_inaccessible_to_user_profiles: List[UserProfile] = []
        orig_topic_user_profile_to_visibility_policy: Dict[UserProfile, int] = {}
        target_topic_user_profile_to_visibility_policy: Dict[UserProfile, int] = {}
        for user_topic in get_users_with_user_topic_visibility_policy(
            stream_being_edited.id, orig_topic_name
        ):
            if new_stream is not None and user_topic.user_profile_id in losing_access_user_ids:
                stream_inaccessible_to_user_profiles.append(user_topic.user_profile)
            else:
                orig_topic_user_profile_to_visibility_policy[user_topic.user_profile] = (
                    user_topic.visibility_policy
                )

        for user_topic in get_users_with_user_topic_visibility_policy(
            target_stream.id, target_topic_name
        ):
            target_topic_user_profile_to_visibility_policy[user_topic.user_profile] = (
                user_topic.visibility_policy
            )

        # User profiles having any of the visibility policies set for either the original or target topic.
        user_profiles_having_visibility_policy: Set[UserProfile] = set(
            itertools.chain(
                orig_topic_user_profile_to_visibility_policy.keys(),
                target_topic_user_profile_to_visibility_policy.keys(),
            )
        )

        user_profiles_for_visibility_policy_pair: Dict[Tuple[int, int], List[UserProfile]] = (
            defaultdict(list)
        )
        for user_profile_with_policy in user_profiles_having_visibility_policy:
            if user_profile_with_policy not in target_topic_user_profile_to_visibility_policy:
                target_topic_user_profile_to_visibility_policy[user_profile_with_policy] = (
                    UserTopic.VisibilityPolicy.INHERIT
                )
            elif user_profile_with_policy not in orig_topic_user_profile_to_visibility_policy:
                orig_topic_user_profile_to_visibility_policy[user_profile_with_policy] = (
                    UserTopic.VisibilityPolicy.INHERIT
                )

            orig_topic_visibility_policy = orig_topic_user_profile_to_visibility_policy[
                user_profile_with_policy
            ]
            target_topic_visibility_policy = target_topic_user_profile_to_visibility_policy[
                user_profile_with_policy
            ]
            user_profiles_for_visibility_policy_pair[
                (orig_topic_visibility_policy, target_topic_visibility_policy)
            ].append(user_profile_with_policy)

        # If the messages are being moved to a stream the user
        # cannot access, then we treat this as the
        # messages/topic being deleted for this user. This is
        # important for security reasons; we don't want to
        # give users a UserTopic row in a stream they cannot
        # access. Remove the user topic rows for such users.
        bulk_do_set_user_topic_visibility_policy(
            stream_inaccessible_to_user_profiles,
            stream_being_edited,
            orig_topic_name,
            visibility_policy=UserTopic.VisibilityPolicy.INHERIT,
        )

        # If the messages are being moved to a stream the user
        # can access. We move the user topic records for such
        # users, but removing the old topic visibility_policy
        # and then creating a new one.
        #
        # Algorithm used for the 'merge userTopic states' case:
        # Using the 'user_profiles_for_visibility_policy_pair' dictionary,
        # we have 'orig_topic_visibility_policy', 'target_topic_visibility_policy',
        # and a list of 'user_profiles' having the mentioned visibility policies.
        #
        # For every 'orig_topic_visibility_policy and target_topic_visibility_policy' pair,
        # we determine the final visibility_policy that should be after the merge.
        # Update the visibility_policy for the concerned set of user_profiles.
        for (
            visibility_policy_pair,
            user_profiles,
        ) in user_profiles_for_visibility_policy_pair.items():
            orig_topic_visibility_policy, target_topic_visibility_policy = visibility_policy_pair

            if orig_topic_visibility_policy != UserTopic.VisibilityPolicy.INHERIT:
                bulk_do_set_user_topic_visibility_policy(
                    user_profiles,
                    stream_being_edited,
                    orig_topic_name,
                    visibility_policy=UserTopic.VisibilityPolicy.INHERIT,
                    # bulk_do_set_user_topic_visibility_policy with visibility_policy
                    # set to 'new_visibility_policy' will send an updated muted topic
                    # event, which contains the full set of muted
                    # topics, just after this.
                    skip_muted_topics_event=True,
                )

            new_visibility_policy = orig_topic_visibility_policy

            if target_topic_has_messages:
                # Here, we handle the complex case when target_topic already has
                # some messages. We determine the resultant visibility_policy
                # based on the visibility_policy of the orig_topic + target_topic.
                # Finally, bulk_update the user_topic rows with the new visibility_policy.
                new_visibility_policy = get_visibility_policy_after_merge(
                    orig_topic_visibility_policy, target_topic_visibility_policy
                )
                if new_visibility_policy == target_topic_visibility_policy:
                    continue
                bulk_do_set_user_topic_visibility_policy(
                    user_profiles,
                    target_stream,
                    target_topic_name,
                    visibility_policy=new_visibility_policy,
                )
            else:
                # This corresponds to the case when messages are moved
                # to a stream-topic pair that didn't exist. There can
                # still be UserTopic rows for the stream-topic pair
                # that didn't exist if the messages in that topic had
                # been deleted.
                if new_visibility_policy == target_topic_visibility_policy:
                    # This avoids unnecessary db operations and INFO logs.
                    continue
                bulk_do_set_user_topic_visibility_policy(
                    user_profiles,
                    target_stream,
                    target_topic_name,
                    visibility_policy=new_visibility_policy,
                )

    send_event(user_profile.realm, event, users_to_be_notified)

    resolved_topic_message_id = None
    if topic_name is not None and content is None and len(changed_messages) > 0:
        # When stream is changed and topic is marked as resolved or unresolved
        # in the same API request, resolved or unresolved notification should
        # be sent to "new_stream".
        # In general, it is sent to "stream_being_edited".
        stream_to_send_resolve_topic_notification = stream_being_edited
        if new_stream is not None:
            stream_to_send_resolve_topic_notification = new_stream

        assert stream_to_send_resolve_topic_notification is not None
        resolved_topic_message_id = maybe_send_resolve_topic_notifications(
            user_profile=user_profile,
            stream=stream_to_send_resolve_topic_notification,
            old_topic_name=orig_topic_name,
            new_topic_name=topic_name,
            changed_messages=changed_messages,
        )

    if (
        len(changed_messages) > 0
        and (new_stream is not None or topic_name is not None)
        and stream_being_edited is not None
    ):
        # Notify users that the topic was moved.
        changed_messages_count = len(changed_messages)

        old_thread_notification_string = None
        if send_notification_to_old_thread:
            if moved_all_visible_messages:
                old_thread_notification_string = gettext_lazy(
                    "This topic was moved to {new_location} by {user}."
                )
            elif changed_messages_count == 1:
                old_thread_notification_string = gettext_lazy(
                    "A message was moved from this topic to {new_location} by {user}."
                )
            else:
                old_thread_notification_string = gettext_lazy(
                    "{changed_messages_count} messages were moved from this topic to {new_location} by {user}."
                )

        # The new thread notification code path is a bit subtle. We
        # don't want every resolve-topic action to also annoyingly
        # send an extra notification that the topic was moved!
        #
        # Since one can resolve/unresolve a topic at the same time
        # you're moving it, we need to carefully treat the resolve
        # topic notification as satisfying our obligation to send a
        # notification to the new topic only if the only thing this
        # request did is mark the topic as resolved.
        new_thread_notification_string = None
        if send_notification_to_new_thread and (
            new_stream is not None
            or not resolved_topic_message_id
            or (
                pre_truncation_topic_name is not None
                and orig_topic_name.lstrip(RESOLVED_TOPIC_PREFIX)
                != pre_truncation_topic_name.lstrip(RESOLVED_TOPIC_PREFIX)
            )
        ):
            stream_for_new_topic = new_stream if new_stream is not None else stream_being_edited
            assert stream_for_new_topic.recipient_id is not None

            new_topic_name = topic_name if topic_name is not None else orig_topic_name

            changed_message_ids = [changed_message.id for changed_message in changed_messages]

            # We calculate whether the user moved the entire topic
            # using that user's own permissions, which is important to
            # avoid leaking information about whether there are
            # messages in the destination topic's deeper history that
            # the acting user does not have permission to access.
            #
            # TODO: These queries are quite inefficient, in that we're
            # fetching full copies of all the messages in the
            # destination topic to answer the question of whether the
            # current user has access to at least one such message.
            #
            # The main strength of the current implementation is that
            # it reuses existing logic, which is good for keeping it
            # correct as we maintain the codebase.
            preexisting_topic_messages = messages_for_topic(
                realm.id, stream_for_new_topic.recipient_id, new_topic_name
            ).exclude(id__in=[*changed_message_ids, resolved_topic_message_id])

            visible_preexisting_messages = bulk_access_messages(
                user_profile, preexisting_topic_messages, stream=stream_for_new_topic
            )

            no_visible_preexisting_messages = len(visible_preexisting_messages) == 0

            if no_visible_preexisting_messages and moved_all_visible_messages:
                new_thread_notification_string = gettext_lazy(
                    "This topic was moved here from {old_location} by {user}."
                )
            else:
                if changed_messages_count == 1:
                    new_thread_notification_string = gettext_lazy(
                        "[A message]({message_link}) was moved here from {old_location} by {user}."
                    )
                else:
                    new_thread_notification_string = gettext_lazy(
                        "{changed_messages_count} messages were moved here from {old_location} by {user}."
                    )

        send_message_moved_breadcrumbs(
            target_message,
            user_profile,
            stream_being_edited,
            orig_topic_name,
            old_thread_notification_string,
            new_stream if new_stream is not None else stream_being_edited,
            topic_name,
            new_thread_notification_string,
            changed_messages_count,
        )

    return len(changed_messages)


def check_time_limit_for_change_all_propagate_mode(
    message: Message,
    user_profile: UserProfile,
    topic_name: Optional[str] = None,
    stream_id: Optional[int] = None,
) -> None:
    realm = user_profile.realm
    message_move_limit_buffer = 20

    topic_edit_deadline_seconds = None
    if topic_name is not None and realm.move_messages_within_stream_limit_seconds is not None:
        # We set topic_edit_deadline_seconds only if topic is actually
        # changed and there is some time limit to edit topic.
        topic_edit_deadline_seconds = (
            realm.move_messages_within_stream_limit_seconds + message_move_limit_buffer
        )

    stream_edit_deadline_seconds = None
    if stream_id is not None and realm.move_messages_between_streams_limit_seconds is not None:
        # We set stream_edit_deadline_seconds only if stream is
        # actually changed and there is some time limit to edit
        # stream.
        stream_edit_deadline_seconds = (
            realm.move_messages_between_streams_limit_seconds + message_move_limit_buffer
        )

    # Calculate whichever of the applicable topic and stream moving
    # limits is stricter, and use that.
    if topic_edit_deadline_seconds is not None and stream_edit_deadline_seconds is not None:
        # When both stream and topic are changed, we consider the
        # minimum of the two limits to make sure that we raise the
        # error even when user cannot change one of topic or stream.
        message_move_deadline_seconds = min(
            topic_edit_deadline_seconds, stream_edit_deadline_seconds
        )
    elif topic_edit_deadline_seconds is not None:
        message_move_deadline_seconds = topic_edit_deadline_seconds
    elif stream_edit_deadline_seconds is not None:
        message_move_deadline_seconds = stream_edit_deadline_seconds
    else:
        # There is no applicable time limit for this move request, so
        # approve it.
        return

    stream = get_stream_by_id_in_realm(message.recipient.type_id, realm)

    if not can_access_stream_history(user_profile, stream):
        # If the user doesn't have full access to the stream's
        # history, check if the user can move the entire portion that
        # they do have access to.
        accessible_messages_in_topic = UserMessage.objects.filter(
            user_profile=user_profile,
            message__recipient_id=message.recipient_id,
            message__subject__iexact=message.topic_name(),
        ).values_list("message_id", flat=True)
        messages_allowed_to_move: List[int] = list(
            Message.objects.filter(
                # Uses index: zerver_message_pkey
                id__in=accessible_messages_in_topic,
                date_sent__gt=timezone_now() - timedelta(seconds=message_move_deadline_seconds),
            )
            .order_by("date_sent")
            .values_list("id", flat=True)
        )
        total_messages_requested_to_move = len(accessible_messages_in_topic)
    else:
        all_messages_in_topic = (
            messages_for_topic(message.realm_id, message.recipient_id, message.topic_name())
            .order_by("id")
            .values_list("id", "date_sent")
        )
        oldest_allowed_message_date = timezone_now() - timedelta(
            seconds=message_move_deadline_seconds
        )
        messages_allowed_to_move = [
            message[0]
            for message in all_messages_in_topic
            if message[1] > oldest_allowed_message_date
        ]
        total_messages_requested_to_move = len(all_messages_in_topic)

    if total_messages_requested_to_move == len(messages_allowed_to_move):
        # We return if all messages are allowed to move.
        return

    raise MessageMoveError(
        first_message_id_allowed_to_move=messages_allowed_to_move[0],
        total_messages_in_topic=total_messages_requested_to_move,
        total_messages_allowed_to_move=len(messages_allowed_to_move),
    )


@transaction.atomic(durable=True)
def check_update_message(
    user_profile: UserProfile,
    message_id: int,
    stream_id: Optional[int] = None,
    topic_name: Optional[str] = None,
    propagate_mode: str = "change_one",
    send_notification_to_old_thread: bool = True,
    send_notification_to_new_thread: bool = True,
    content: Optional[str] = None,
) -> int:
    """This will update a message given the message id and user profile.
    It checks whether the user profile has the permission to edit the message
    and raises a JsonableError if otherwise.
    It returns the number changed.
    """
    message, ignored_user_message = access_message(user_profile, message_id, lock_message=True)

    if content is not None and not user_profile.realm.allow_message_editing:
        raise JsonableError(_("Your organization has turned off message editing"))

    # The zerver/views/message_edit.py call point already strips this
    # via REQ_topic; so we can delete this line if we arrange a
    # contract where future callers in the embedded bots system strip
    # use REQ_topic as well (or otherwise are guaranteed to strip input).
    if topic_name is not None:
        topic_name = topic_name.strip()
        if topic_name == message.topic_name():
            topic_name = None

    validate_message_edit_payload(message, stream_id, topic_name, propagate_mode, content)

    if (
        content is not None
        # You cannot edit the content of message sent by someone else.
        and message.sender_id != user_profile.id
    ):
        raise JsonableError(_("You don't have permission to edit this message"))

    if topic_name is not None and not user_profile.can_move_messages_to_another_topic():
        raise JsonableError(_("You don't have permission to edit this message"))

    # If there is a change to the content, check that it hasn't been too long
    # Allow an extra 20 seconds since we potentially allow editing 15 seconds
    # past the limit, and in case there are network issues, etc. The 15 comes
    # from (min_seconds_to_edit + seconds_left_buffer) in message_edit.js; if
    # you change this value also change those two parameters in message_edit.js.
    edit_limit_buffer = 20
    if content is not None and user_profile.realm.message_content_edit_limit_seconds is not None:
        deadline_seconds = user_profile.realm.message_content_edit_limit_seconds + edit_limit_buffer
        if (timezone_now() - message.date_sent) > timedelta(seconds=deadline_seconds):
            raise JsonableError(_("The time limit for editing this message has passed"))

    # If there is a change to the topic, check that the user is allowed to
    # edit it and that it has not been too long. If user is not admin or moderator,
    # and the time limit for editing topics is passed, raise an error.
    if (
        topic_name is not None
        and user_profile.realm.move_messages_within_stream_limit_seconds is not None
        and not user_profile.is_realm_admin
        and not user_profile.is_moderator
    ):
        deadline_seconds = (
            user_profile.realm.move_messages_within_stream_limit_seconds + edit_limit_buffer
        )
        if (timezone_now() - message.date_sent) > timedelta(seconds=deadline_seconds):
            raise JsonableError(_("The time limit for editing this message's topic has passed."))

    rendering_result = None
    links_for_embed: Set[str] = set()
    prior_mention_user_ids: Set[int] = set()
    mention_data: Optional[MentionData] = None
    if content is not None:
        if content.rstrip() == "":
            content = "(deleted)"
        content = normalize_body(content)

        mention_backend = MentionBackend(user_profile.realm_id)
        mention_data = MentionData(
            mention_backend=mention_backend,
            content=content,
            message_sender=message.sender,
        )
        prior_mention_user_ids = get_mentions_for_message_updates(message.id)

        # We render the message using the current user's realm; since
        # the cross-realm bots never edit messages, this should be
        # always correct.
        # Note: If rendering fails, the called code will raise a JsonableError.
        rendering_result = render_incoming_message(
            message,
            content,
            user_profile.realm,
            mention_data=mention_data,
        )
        links_for_embed |= rendering_result.links_for_preview

        if message.is_stream_message() and rendering_result.mentions_stream_wildcard:
            stream = access_stream_by_id(user_profile, message.recipient.type_id)[0]
            if not stream_wildcard_mention_allowed(message.sender, stream, message.realm):
                raise StreamWildcardMentionNotAllowedError

        if message.is_stream_message() and rendering_result.mentions_topic_wildcard:
            topic_participant_count = len(
                participants_for_topic(message.realm.id, message.recipient.id, message.topic_name())
            )
            if not topic_wildcard_mention_allowed(
                message.sender, topic_participant_count, message.realm
            ):
                raise TopicWildcardMentionNotAllowedError

        if rendering_result.mentions_user_group_ids:
            mentioned_group_ids = list(rendering_result.mentions_user_group_ids)
            check_user_group_mention_allowed(user_profile, mentioned_group_ids)

    new_stream = None
    number_changed = 0

    if stream_id is not None:
        assert message.is_stream_message()
        if not user_profile.can_move_messages_between_streams():
            raise JsonableError(_("You don't have permission to move this message"))

        new_stream = access_stream_by_id(user_profile, stream_id, require_active=True)[0]
        check_stream_access_based_on_stream_post_policy(user_profile, new_stream)

        if (
            user_profile.realm.move_messages_between_streams_limit_seconds is not None
            and not user_profile.is_realm_admin
            and not user_profile.is_moderator
        ):
            deadline_seconds = (
                user_profile.realm.move_messages_between_streams_limit_seconds + edit_limit_buffer
            )
            if (timezone_now() - message.date_sent) > timedelta(seconds=deadline_seconds):
                raise JsonableError(
                    _("The time limit for editing this message's stream has passed")
                )

    if (
        propagate_mode == "change_all"
        and not user_profile.is_realm_admin
        and not user_profile.is_moderator
        and (topic_name is not None or stream_id is not None)
    ):
        check_time_limit_for_change_all_propagate_mode(message, user_profile, topic_name, stream_id)

    number_changed = do_update_message(
        user_profile,
        message,
        new_stream,
        topic_name,
        propagate_mode,
        send_notification_to_old_thread,
        send_notification_to_new_thread,
        content,
        rendering_result,
        prior_mention_user_ids,
        mention_data,
    )

    if links_for_embed:
        event_data = {
            "message_id": message.id,
            "message_content": message.content,
            # The choice of `user_profile.realm_id` rather than
            # `sender.realm_id` must match the decision made in the
            # `render_incoming_message` call earlier in this function.
            "message_realm_id": user_profile.realm_id,
            "urls": list(links_for_embed),
        }
        queue_json_publish("embed_links", event_data)

    return number_changed