#
# This file is licensed under the Affero General Public License (AGPL) version 3.
#
# Copyright 2016 OpenMarket Ltd
# Copyright (C) 2023 New Vector, Ltd
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# See the GNU Affero General Public License for more details:
# <https://www.gnu.org/licenses/agpl-3.0.html>.
#
# Originally licensed under the Apache License, Version 2.0:
# <http://www.apache.org/licenses/LICENSE-2.0>.
#
# [This file includes modifications made by New Vector Limited]
#
#

import logging
import re
from typing import TYPE_CHECKING, Iterable

from synapse.api.constants import EventTypes, Membership
from synapse.events import EventBase
from synapse.types import StateMap

if TYPE_CHECKING:
    from synapse.storage.databases.main import DataStore

logger = logging.getLogger(__name__)

# intentionally looser than what aliases we allow to be registered since
# other HSes may allow aliases that we would not
ALIAS_RE = re.compile(r"^#.*:.+$")

ALL_ALONE = "Empty Room"


async def calculate_room_name(
    store: "DataStore",
    room_state_ids: StateMap[str],
    user_id: str,
    fallback_to_members: bool = True,
    fallback_to_single_member: bool = True,
) -> str | None:
    """
    Works out a user-facing name for the given room as per Matrix
    spec recommendations.
    Does not yet support internationalisation.
    Args:
        store: The data store to query.
        room_state_ids: Dictionary of the room's state IDs.
        user_id: The ID of the user to whom the room name is being presented
        fallback_to_members: If False, return None instead of generating a name
                             based on the room's members if the room has no
                             title or aliases.
        fallback_to_single_member: If False, return None instead of generating a
            name based on the user who invited this user to the room if the room
            has no title or aliases.

    Returns:
        A human readable name for the room, if possible.
    """
    # does it have a name?
    if (EventTypes.Name, "") in room_state_ids:
        m_room_name = await store.get_event(
            room_state_ids[(EventTypes.Name, "")], allow_none=True
        )
        if m_room_name and m_room_name.content and m_room_name.content.get("name"):
            return m_room_name.content["name"]

    # does it have a canonical alias?
    if (EventTypes.CanonicalAlias, "") in room_state_ids:
        canon_alias = await store.get_event(
            room_state_ids[(EventTypes.CanonicalAlias, "")], allow_none=True
        )
        if (
            canon_alias
            and canon_alias.content
            and canon_alias.content.get("alias")
            and _looks_like_an_alias(canon_alias.content["alias"])
        ):
            return canon_alias.content["alias"]

    if not fallback_to_members:
        return None

    my_member_event = None
    if (EventTypes.Member, user_id) in room_state_ids:
        my_member_event = await store.get_event(
            room_state_ids[(EventTypes.Member, user_id)], allow_none=True
        )

    if (
        my_member_event is not None
        and my_member_event.content.get("membership") == Membership.INVITE
    ):
        if (EventTypes.Member, my_member_event.sender) in room_state_ids:
            inviter_member_event = await store.get_event(
                room_state_ids[(EventTypes.Member, my_member_event.sender)],
                allow_none=True,
            )
            if inviter_member_event:
                if fallback_to_single_member:
                    return "Invite from %s" % (
                        name_from_member_event(inviter_member_event),
                    )
                else:
                    return None
        else:
            return "Room Invite"

    # at this point we're going to need to search the state by all state keys
    # for an event type, so rearrange the data structure
    room_state_bytype_ids = _state_as_two_level_dict(room_state_ids)

    # we're going to have to generate a name based on who's in the room,
    # so find out who is in the room that isn't the user.
    if EventTypes.Member in room_state_bytype_ids:
        member_events = await store.get_events(
            list(room_state_bytype_ids[EventTypes.Member].values())
        )
        all_members = [
            ev
            for ev in member_events.values()
            if ev.content.get("membership") == Membership.JOIN
            or ev.content.get("membership") == Membership.INVITE
        ]
        # Sort the member events oldest-first so the we name people in the
        # order the joined (it should at least be deterministic rather than
        # dictionary iteration order)
        all_members.sort(key=lambda e: e.origin_server_ts)
        other_members = [m for m in all_members if m.state_key != user_id]
    else:
        other_members = []
        all_members = []

    if len(other_members) == 0:
        if len(all_members) == 1:
            # self-chat, peeked room with 1 participant,
            # or inbound invite, or outbound 3PID invite.
            if all_members[0].sender == user_id:
                if EventTypes.ThirdPartyInvite in room_state_bytype_ids:
                    third_party_invites = room_state_bytype_ids[
                        EventTypes.ThirdPartyInvite
                    ].values()

                    if len(third_party_invites) > 0:
                        # technically third party invite events are not member
                        # events, but they are close enough

                        # FIXME: no they're not - they look nothing like a member;
                        # they have a great big encrypted thing as their name to
                        # prevent leaking the 3PID name...
                        # return "Inviting %s" % (
                        #     descriptor_from_member_events(third_party_invites)
                        # )
                        return "Inviting email address"
                    else:
                        return ALL_ALONE
            else:
                return name_from_member_event(all_members[0])
        else:
            return ALL_ALONE
    elif len(other_members) == 1 and not fallback_to_single_member:
        return None

    return descriptor_from_member_events(other_members)


def descriptor_from_member_events(member_events: Iterable[EventBase]) -> str:
    """Get a description of the room based on the member events.

    Args:
        member_events: The events of a room.

    Returns:
        The room description
    """

    member_events = list(member_events)

    if len(member_events) == 0:
        return "nobody"
    elif len(member_events) == 1:
        return name_from_member_event(member_events[0])
    elif len(member_events) == 2:
        return "%s and %s" % (
            name_from_member_event(member_events[0]),
            name_from_member_event(member_events[1]),
        )
    else:
        return "%s and %d others" % (
            name_from_member_event(member_events[0]),
            len(member_events) - 1,
        )


def name_from_member_event(member_event: EventBase) -> str:
    if member_event.content and member_event.content.get("displayname"):
        return member_event.content["displayname"]
    return member_event.state_key


def _state_as_two_level_dict(state: StateMap[str]) -> dict[str, dict[str, str]]:
    ret: dict[str, dict[str, str]] = {}
    for k, v in state.items():
        ret.setdefault(k[0], {})[k[1]] = v
    return ret


def _looks_like_an_alias(string: str) -> bool:
    return ALIAS_RE.match(string) is not None
