from collections.abc import Mapping
from typing import TYPE_CHECKING, Optional, TypedDict

from django.db.models import QuerySet

from zerver.lib.cache import (
    bulk_cached_fetch,
    cache_with_key,
    display_recipient_cache_key,
    generic_bulk_cached_fetch,
    single_user_display_recipient_cache_key,
)
from zerver.lib.per_request_cache import cache_for_current_request
from zerver.lib.types import DisplayRecipientT, UserDisplayRecipient

if TYPE_CHECKING:
    from zerver.models import Recipient

display_recipient_fields = [
    "id",
    "email",
    "full_name",
    "is_mirror_dummy",
]


class TinyStreamResult(TypedDict):
    recipient_id: int
    name: str


def get_display_recipient_cache_key(
    recipient_id: int, recipient_type: int, recipient_type_id: int | None
) -> str:
    return display_recipient_cache_key(recipient_id)


# Note that the _same_ cache key is used for streams, which contain a
# string, not a list[UserDisplayRecipient]!  This works because the
# recipient space is distinct between the two.
@cache_with_key(get_display_recipient_cache_key, timeout=3600 * 24 * 7)
def get_display_recipient_remote_cache(
    recipient_id: int, recipient_type: int, recipient_type_id: int | None
) -> list[UserDisplayRecipient]:
    """
    This returns an appropriate object describing the recipient of a
    direct message (whether individual or group).

    It will be an array of dicts for each recipient.

    Do not use this for streams.
    """

    from zerver.models import Recipient, UserProfile

    assert recipient_type != Recipient.STREAM

    # 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,
        )
        .order_by("id")
        .values(*display_recipient_fields)
    )
    return list(user_profile_list)


def user_dict_id_fetcher(user_dict: UserDisplayRecipient) -> int:
    return user_dict["id"]


def bulk_fetch_single_user_display_recipients(uids: list[int]) -> dict[int, UserDisplayRecipient]:
    from zerver.models import UserProfile

    return bulk_cached_fetch(
        # Use a separate cache key to protect us from conflicts with
        # the get_user_profile_by_id cache.
        # (Since we fetch only several fields here)
        cache_key_function=single_user_display_recipient_cache_key,
        query_function=lambda ids: list(
            UserProfile.objects.filter(id__in=ids).values(*display_recipient_fields)
        ),
        object_ids=uids,
        id_fetcher=user_dict_id_fetcher,
    )


def bulk_fetch_stream_names(
    recipient_tuples: set[tuple[int, int, int]],
) -> dict[int, str]:
    """
    Takes set of tuples of the form (recipient_id, recipient_type, recipient_type_id)
    Returns dict mapping recipient_id to corresponding display_recipient
    """

    from zerver.models import Stream

    if len(recipient_tuples) == 0:
        return {}

    recipient_id_to_stream_id = {tup[0]: tup[2] for tup in recipient_tuples}
    recipient_ids = [tup[0] for tup in recipient_tuples]

    def get_tiny_stream_rows(
        recipient_ids: list[int],
    ) -> QuerySet[Stream, TinyStreamResult]:
        stream_ids = [recipient_id_to_stream_id[recipient_id] for recipient_id in recipient_ids]
        return Stream.objects.filter(id__in=stream_ids).values("recipient_id", "name")

    def get_recipient_id(row: TinyStreamResult) -> int:
        return row["recipient_id"]

    def get_name(row: TinyStreamResult) -> str:
        return row["name"]

    # ItemT = TinyStreamResult, CacheItemT = str (name), ObjKT = int (recipient_id)
    stream_display_recipients: dict[int, str] = generic_bulk_cached_fetch(
        cache_key_function=display_recipient_cache_key,
        query_function=get_tiny_stream_rows,
        object_ids=recipient_ids,
        id_fetcher=get_recipient_id,
        cache_transformer=get_name,
        setter=lambda obj: obj,
        extractor=lambda obj: obj,
        pickled_tupled=False,
    )

    return stream_display_recipients


def bulk_fetch_user_display_recipients(
    recipient_tuples: set[tuple[int, int, int]],
    recipient_dm_user_ids: Mapping[int, set[int]] = {},
) -> dict[int, list[UserDisplayRecipient]]:
    """
    Takes set of tuples of the form (recipient_id, recipient_type, recipient_type_id)
    Returns dict mapping recipient_id to corresponding display_recipient

    The participants of a DirectMessageGroup are fixed when it is created, so
    a caller that already knows them for some recipients can pass them in via
    dm_involved_user_ids to avoid looking them up again.
    """

    from zerver.models.recipients import bulk_get_direct_message_group_user_ids

    if len(recipient_tuples) == 0:
        return {}

    get_recipient_id = lambda tup: tup[0]

    direct_message_group_recipient_ids = [get_recipient_id(tup) for tup in recipient_tuples]

    # Query only DirectMessageGroup participants who are not already loaded.
    user_ids_in_direct_message_groups = bulk_get_direct_message_group_user_ids(
        [
            recipient_id
            for recipient_id in direct_message_group_recipient_ids
            if recipient_id not in recipient_dm_user_ids
        ]
    )
    user_ids_in_direct_message_groups.update(recipient_dm_user_ids)

    # Find all user ids whose UserProfiles we will need to fetch:
    user_ids_to_fetch: set[int] = set()

    for recipient_id in direct_message_group_recipient_ids:
        direct_message_group_user_ids = user_ids_in_direct_message_groups[recipient_id]
        user_ids_to_fetch |= direct_message_group_user_ids

    # Fetch the needed user dictionaries.
    user_display_recipients = bulk_fetch_single_user_display_recipients(list(user_ids_to_fetch))

    result = {}

    for recipient_id in direct_message_group_recipient_ids:
        user_ids = sorted(user_ids_in_direct_message_groups[recipient_id])
        display_recipients = [user_display_recipients[user_id] for user_id in user_ids]
        result[recipient_id] = display_recipients

    return result


def bulk_fetch_display_recipients(
    recipient_tuples: set[tuple[int, int, int]],
    recipient_dm_user_ids: Mapping[int, set[int]] = {},
) -> dict[int, DisplayRecipientT]:
    """
    Takes set of tuples of the form (recipient_id, recipient_type, recipient_type_id)
    Returns dict mapping recipient_id to corresponding display_recipient
    """

    from zerver.models import Recipient

    stream_recipients = {
        recipient for recipient in recipient_tuples if recipient[1] == Recipient.STREAM
    }
    direct_message_recipients = recipient_tuples - stream_recipients

    stream_display_recipients = bulk_fetch_stream_names(stream_recipients)
    direct_message_display_recipients = bulk_fetch_user_display_recipients(
        direct_message_recipients, recipient_dm_user_ids
    )

    # Glue the dicts together and return:
    return {**stream_display_recipients, **direct_message_display_recipients}


@cache_for_current_request
def get_display_recipient_by_id(
    recipient_id: int, recipient_type: int, recipient_type_id: int | None
) -> list[UserDisplayRecipient]:
    """
    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.
    """
    return get_display_recipient_remote_cache(recipient_id, recipient_type, recipient_type_id)


def get_display_recipient(recipient: "Recipient") -> list[UserDisplayRecipient]:
    return get_display_recipient_by_id(
        recipient.id,
        recipient.type,
        recipient.type_id,
    )


def get_recipient_ids(
    recipient: Optional["Recipient"], user_profile_id: int
) -> tuple[list[int], str]:
    from zerver.models import Recipient

    if recipient is None:
        recipient_type_str = ""
        to = []
    elif recipient.type == Recipient.STREAM:
        recipient_type_str = "stream"
        to = [recipient.type_id]
    else:
        # We're somewhat weirdly using the display recipient cache,
        # for the fact that it is a probably-cached lookup which knows
        # the user-ids which are members of a group DM.
        recipient_type_str = "private"
        to = []
        recipients = get_display_recipient(recipient)
        for r in recipients:
            assert not isinstance(r, str)  # It will only be a string for streams
            if r["id"] != user_profile_id or len(recipients) == 1:
                to.append(r["id"])
    return to, recipient_type_str