#
# This file is licensed under the Affero General Public License (AGPL) version 3.
#
# 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 abc
import logging
from typing import TYPE_CHECKING, Any, Dict, List, Mapping, Optional, Sequence, Set

import attr

from synapse.api.constants import Direction, Membership
from synapse.events import EventBase
from synapse.types import JsonMapping, RoomStreamToken, StateMap, UserID, UserInfo
from synapse.visibility import filter_events_for_client

if TYPE_CHECKING:
    from synapse.server import HomeServer

logger = logging.getLogger(__name__)


class AdminHandler:
    def __init__(self, hs: "HomeServer"):
        self._store = hs.get_datastores().main
        self._device_handler = hs.get_device_handler()
        self._storage_controllers = hs.get_storage_controllers()
        self._state_storage_controller = self._storage_controllers.state
        self._msc3866_enabled = hs.config.experimental.msc3866.enabled

    async def get_whois(self, user: UserID) -> JsonMapping:
        connections = []

        sessions = await self._store.get_user_ip_and_agents(user)
        for session in sessions:
            connections.append(
                {
                    "ip": session["ip"],
                    "last_seen": session["last_seen"],
                    "user_agent": session["user_agent"],
                }
            )

        ret = {
            "user_id": user.to_string(),
            "devices": {"": {"sessions": [{"connections": connections}]}},
        }

        return ret

    async def get_user(self, user: UserID) -> Optional[JsonMapping]:
        """Function to get user details"""
        user_info: Optional[UserInfo] = await self._store.get_user_by_id(
            user.to_string()
        )
        if user_info is None:
            return None

        user_info_dict = {
            "name": user.to_string(),
            "admin": user_info.is_admin,
            "deactivated": user_info.is_deactivated,
            "locked": user_info.locked,
            "shadow_banned": user_info.is_shadow_banned,
            "creation_ts": user_info.creation_ts,
            "appservice_id": user_info.appservice_id,
            "consent_server_notice_sent": user_info.consent_server_notice_sent,
            "consent_version": user_info.consent_version,
            "consent_ts": user_info.consent_ts,
            "user_type": user_info.user_type,
            "is_guest": user_info.is_guest,
        }

        if self._msc3866_enabled:
            # Only include the approved flag if support for MSC3866 is enabled.
            user_info_dict["approved"] = user_info.approved

        # Add additional user metadata
        profile = await self._store.get_profileinfo(user)
        threepids = await self._store.user_get_threepids(user.to_string())
        external_ids = [
            ({"auth_provider": auth_provider, "external_id": external_id})
            for auth_provider, external_id in await self._store.get_external_ids_by_user(
                user.to_string()
            )
        ]
        user_info_dict["displayname"] = profile.display_name
        user_info_dict["avatar_url"] = profile.avatar_url
        user_info_dict["threepids"] = [attr.asdict(t) for t in threepids]
        user_info_dict["external_ids"] = external_ids
        user_info_dict["erased"] = await self._store.is_user_erased(user.to_string())

        last_seen_ts = await self._store.get_last_seen_for_user_id(user.to_string())
        user_info_dict["last_seen_ts"] = last_seen_ts

        return user_info_dict

    async def export_user_data(self, user_id: str, writer: "ExfiltrationWriter") -> Any:
        """Write all data we have on the user to the given writer.

        Args:
            user_id: The user ID to fetch data of.
            writer: The writer to write to.

        Returns:
            Resolves when all data for a user has been written.
            The returned value is that returned by `writer.finished()`.
        """
        # Get all rooms the user is in or has been in
        rooms = await self._store.get_rooms_for_local_user_where_membership_is(
            user_id,
            membership_list=(
                Membership.JOIN,
                Membership.LEAVE,
                Membership.BAN,
                Membership.INVITE,
                Membership.KNOCK,
            ),
        )

        # We only try and fetch events for rooms the user has been in. If
        # they've been e.g. invited to a room without joining then we handle
        # those separately.
        rooms_user_has_been_in = await self._store.get_rooms_user_has_been_in(user_id)

        for index, room in enumerate(rooms):
            room_id = room.room_id

            logger.info(
                "[%s] Handling room %s, %d/%d", user_id, room_id, index + 1, len(rooms)
            )

            forgotten = await self._store.did_forget(user_id, room_id)
            if forgotten:
                logger.info("[%s] User forgot room %d, ignoring", user_id, room_id)
                continue

            if room_id not in rooms_user_has_been_in:
                # If we haven't been in the rooms then the filtering code below
                # won't return anything, so we need to handle these cases
                # explicitly.

                if room.membership == Membership.INVITE:
                    event_id = room.event_id
                    invite = await self._store.get_event(event_id, allow_none=True)
                    if invite:
                        invited_state = invite.unsigned["invite_room_state"]
                        writer.write_invite(room_id, invite, invited_state)

                if room.membership == Membership.KNOCK:
                    event_id = room.event_id
                    knock = await self._store.get_event(event_id, allow_none=True)
                    if knock:
                        knock_state = knock.unsigned["knock_room_state"]
                        writer.write_knock(room_id, knock, knock_state)

                continue

            # We only want to bother fetching events up to the last time they
            # were joined. We estimate that point by looking at the
            # stream_ordering of the last membership if it wasn't a join.
            if room.membership == Membership.JOIN:
                stream_ordering = self._store.get_room_max_stream_ordering()
            else:
                stream_ordering = room.stream_ordering

            from_key = RoomStreamToken(topological=0, stream=0)
            to_key = RoomStreamToken(stream=stream_ordering)

            # Events that we've processed in this room
            written_events: Set[str] = set()

            # We need to track gaps in the events stream so that we can then
            # write out the state at those events. We do this by keeping track
            # of events whose prev events we haven't seen.

            # Map from event ID to prev events that haven't been processed,
            # dict[str, set[str]].
            event_to_unseen_prevs = {}

            # The reverse mapping to above, i.e. map from unseen event to events
            # that have the unseen event in their prev_events, i.e. the unseen
            # events "children".
            unseen_to_child_events: Dict[str, Set[str]] = {}

            # We fetch events in the room the user could see by fetching *all*
            # events that we have and then filtering, this isn't the most
            # efficient method perhaps but it does guarantee we get everything.
            while True:
                events, _ = await self._store.paginate_room_events(
                    room_id, from_key, to_key, limit=100, direction=Direction.FORWARDS
                )
                if not events:
                    break

                last_event = events[-1]
                assert last_event.internal_metadata.stream_ordering
                from_key = RoomStreamToken(
                    stream=last_event.internal_metadata.stream_ordering,
                    topological=last_event.depth,
                )

                events = await filter_events_for_client(
                    self._storage_controllers, user_id, events
                )

                writer.write_events(room_id, events)

                # Update the extremity tracking dicts
                for event in events:
                    # Check if we have any prev events that haven't been
                    # processed yet, and add those to the appropriate dicts.
                    unseen_events = set(event.prev_event_ids()) - written_events
                    if unseen_events:
                        event_to_unseen_prevs[event.event_id] = unseen_events
                        for unseen in unseen_events:
                            unseen_to_child_events.setdefault(unseen, set()).add(
                                event.event_id
                            )

                    # Now check if this event is an unseen prev event, if so
                    # then we remove this event from the appropriate dicts.
                    for child_id in unseen_to_child_events.pop(event.event_id, []):
                        event_to_unseen_prevs[child_id].discard(event.event_id)

                    written_events.add(event.event_id)

                logger.info(
                    "Written %d events in room %s", len(written_events), room_id
                )

            # Extremities are the events who have at least one unseen prev event.
            extremities = (
                event_id
                for event_id, unseen_prevs in event_to_unseen_prevs.items()
                if unseen_prevs
            )
            for event_id in extremities:
                if not event_to_unseen_prevs[event_id]:
                    continue
                state = await self._state_storage_controller.get_state_for_event(
                    event_id
                )
                writer.write_state(room_id, event_id, state)

        # Get the user profile
        profile = await self.get_user(UserID.from_string(user_id))
        if profile is not None:
            writer.write_profile(profile)
            logger.info("[%s] Written profile", user_id)

        # Get all devices the user has
        devices = await self._device_handler.get_devices_by_user(user_id)
        writer.write_devices(devices)
        logger.info("[%s] Written %s devices", user_id, len(devices))

        # Get all connections the user has
        connections = await self.get_whois(UserID.from_string(user_id))
        writer.write_connections(
            connections["devices"][""]["sessions"][0]["connections"]
        )
        logger.info("[%s] Written %s connections", user_id, len(connections))

        # Get all account data the user has global and in rooms
        global_data = await self._store.get_global_account_data_for_user(user_id)
        by_room_data = await self._store.get_room_account_data_for_user(user_id)
        writer.write_account_data("global", global_data)
        for room_id in by_room_data:
            writer.write_account_data(room_id, by_room_data[room_id])
        logger.info(
            "[%s] Written account data for %s rooms", user_id, len(by_room_data)
        )

        # Get all media ids the user has
        limit = 100
        start = 0
        while True:
            media_ids, total = await self._store.get_local_media_by_user_paginate(
                start, limit, user_id
            )
            for media in media_ids:
                writer.write_media_id(media.media_id, attr.asdict(media))

            logger.info(
                "[%s] Written %d media_ids of %s",
                user_id,
                (start + len(media_ids)),
                total,
            )
            if (start + limit) >= total:
                break
            start += limit

        return writer.finished()


class ExfiltrationWriter(metaclass=abc.ABCMeta):
    """Interface used to specify how to write exported data."""

    @abc.abstractmethod
    def write_events(self, room_id: str, events: List[EventBase]) -> None:
        """Write a batch of events for a room."""
        raise NotImplementedError()

    @abc.abstractmethod
    def write_state(
        self, room_id: str, event_id: str, state: StateMap[EventBase]
    ) -> None:
        """Write the state at the given event in the room.

        This only gets called for backward extremities rather than for each
        event.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def write_invite(
        self, room_id: str, event: EventBase, state: StateMap[EventBase]
    ) -> None:
        """Write an invite for the room, with associated invite state.

        Args:
            room_id: The room ID the invite is for.
            event: The invite event.
            state: A subset of the state at the invite, with a subset of the
                event keys (type, state_key content and sender).
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def write_knock(
        self, room_id: str, event: EventBase, state: StateMap[EventBase]
    ) -> None:
        """Write a knock for the room, with associated knock state.

        Args:
            room_id: The room ID the knock is for.
            event: The knock event.
            state: A subset of the state at the knock, with a subset of the
                event keys (type, state_key content and sender).
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def write_profile(self, profile: JsonMapping) -> None:
        """Write the profile of a user.

        Args:
            profile: The user profile.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def write_devices(self, devices: Sequence[JsonMapping]) -> None:
        """Write the devices of a user.

        Args:
            devices: The list of devices.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def write_connections(self, connections: Sequence[JsonMapping]) -> None:
        """Write the connections of a user.

        Args:
            connections: The list of connections / sessions.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def write_account_data(
        self, file_name: str, account_data: Mapping[str, JsonMapping]
    ) -> None:
        """Write the account data of a user.

        Args:
            file_name: file name to write data
            account_data: mapping of global or room account_data
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def write_media_id(self, media_id: str, media_metadata: JsonMapping) -> None:
        """Write the media's metadata of a user.
        Exports only the metadata, as this can be fetched from the database via
        read only. In order to access the files, a connection to the correct
        media repository would be required.

        Args:
            media_id: ID of the media.
            media_metadata: Metadata of one media file.
        """

    @abc.abstractmethod
    def finished(self) -> Any:
        """Called when all data has successfully been exported and written.

        This functions return value is passed to the caller of
        `export_user_data`.
        """
        raise NotImplementedError()
