#
# 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 heapq
import logging
from typing import (
    TYPE_CHECKING,
    Any,
    Awaitable,
    Callable,
    List,
    Optional,
    Tuple,
    TypeVar,
)

import attr

from synapse.api.constants import AccountDataTypes
from synapse.replication.http.streams import ReplicationGetStreamUpdates

if TYPE_CHECKING:
    from synapse.server import HomeServer
    from synapse.storage.util.id_generators import AbstractStreamIdGenerator

logger = logging.getLogger(__name__)

# the number of rows to request from an update_function.
_STREAM_UPDATE_TARGET_ROW_COUNT = 100


# Some type aliases to make things a bit easier.

# A stream position token
Token = int

# The type of a stream update row, after JSON deserialisation, but before
# parsing with Stream.parse_row (which turns it into a `ROW_TYPE`). Normally it's
# just a row from a database query, though this is dependent on the stream in question.
#
StreamRow = TypeVar("StreamRow", bound=Tuple)

# The type returned by the update_function of a stream, as well as get_updates(),
# get_updates_since, etc.
#
# It consists of a triplet `(updates, new_last_token, limited)`, where:
#   * `updates` is a list of `(token, row)` entries.
#   * `new_last_token` is the new position in stream.
#   * `limited` is whether there are more updates to fetch.
#
StreamUpdateResult = Tuple[List[Tuple[Token, StreamRow]], Token, bool]

# The type of an update_function for a stream
#
# The arguments are:
#
#  * instance_name: the writer of the stream
#  * from_token: the previous stream token: the starting point for fetching the
#    updates
#  * to_token: the new stream token: the point to get updates up to
#  * target_row_count: a target for the number of rows to be returned.
#
# The update_function is expected to return up to _approximately_ target_row_count rows.
# If there are more updates available, it should set `limited` in the result, and
# it will be called again to get the next batch.
#
UpdateFunction = Callable[[str, Token, Token, int], Awaitable[StreamUpdateResult]]


class Stream:
    """Base class for the streams.

    Provides a `get_updates()` function that returns new updates since the last
    time it was called.
    """

    NAME: str  # The name of the stream
    # The type of the row. Used by the default impl of parse_row.
    ROW_TYPE: Any = None

    @classmethod
    def parse_row(cls, row: StreamRow) -> Any:
        """Parse a row received over replication

        By default, assumes that the row data is an array object and passes its contents
        to the constructor of the ROW_TYPE for this stream.

        Args:
            row: row data from the incoming RDATA command, after json decoding

        Returns:
            ROW_TYPE object for this stream
        """
        return cls.ROW_TYPE(*row)

    def __init__(
        self,
        local_instance_name: str,
        update_function: UpdateFunction,
    ):
        """Instantiate a Stream

        `update_function` is called to get updates for this stream between a
        pair of stream tokens. See the `UpdateFunction` type definition for more
        info.

        Args:
            local_instance_name: The instance name of the current process
            current_token_function: callback to get the current token, as above
            update_function: callback go get stream updates, as above
        """
        self.local_instance_name = local_instance_name
        self.update_function = update_function

        # The token from which we last asked for updates
        self.last_token = self.current_token(self.local_instance_name)

    def current_token(self, instance_name: str) -> Token:
        """This takes an instance name, which is a writer to
        the stream, and returns the position in the stream of the writer (as
        viewed from the current process).
        """
        # We can't make this an abstract class as it makes mypy unhappy.
        raise NotImplementedError()

    def minimal_local_current_token(self) -> Token:
        """Tries to return a minimal current token for the local instance,
        i.e. for writers this would be the last successful write.

        If local instance is not a writer (or has written yet) then falls back
        to returning the normal "current token".
        """
        raise NotImplementedError()

    def can_discard_position(
        self, instance_name: str, prev_token: int, new_token: int
    ) -> bool:
        """Whether or not a position command for this stream can be discarded.

        Useful for streams that can never go backwards and where we already know
        the stream ID for the instance has advanced.
        """
        return False

    def discard_updates_and_advance(self) -> None:
        """Called when the stream should advance but the updates would be discarded,
        e.g. when there are no currently connected workers.
        """
        self.last_token = self.current_token(self.local_instance_name)

    async def get_updates(self) -> StreamUpdateResult:
        """Gets all updates since the last time this function was called (or
        since the stream was constructed if it hadn't been called before).

        Returns:
            A triplet `(updates, new_last_token, limited)`, where `updates` is
            a list of `(token, row)` entries, `new_last_token` is the new
            position in stream (ie the highest token returned in the updates),
            and `limited` is whether there are more updates to fetch.
        """
        current_token = self.current_token(self.local_instance_name)

        # If the minimum current token for the local instance is less than or
        # equal to the last thing we published, we know that there are no
        # updates.
        if self.last_token >= self.minimal_local_current_token():
            self.last_token = current_token
            return [], current_token, False

        updates, current_token, limited = await self.get_updates_since(
            self.local_instance_name, self.last_token, current_token
        )
        self.last_token = current_token

        return updates, current_token, limited

    async def get_updates_since(
        self, instance_name: str, from_token: Token, upto_token: Token
    ) -> StreamUpdateResult:
        """Like get_updates except allows specifying from when we should
        stream updates

        Returns:
            A triplet `(updates, new_last_token, limited)`, where `updates` is
            a list of `(token, row)` entries, `new_last_token` is the new
            position in stream, and `limited` is whether there are more updates
            to fetch.
        """

        from_token = int(from_token)

        if from_token == upto_token:
            return [], upto_token, False

        updates, upto_token, limited = await self.update_function(
            instance_name,
            from_token,
            upto_token,
            _STREAM_UPDATE_TARGET_ROW_COUNT,
        )
        return updates, upto_token, limited


class _StreamFromIdGen(Stream):
    """Helper class for simple streams that use a stream ID generator"""

    def __init__(
        self,
        local_instance_name: str,
        update_function: UpdateFunction,
        stream_id_gen: "AbstractStreamIdGenerator",
    ):
        self._stream_id_gen = stream_id_gen
        super().__init__(local_instance_name, update_function)

    def current_token(self, instance_name: str) -> Token:
        return self._stream_id_gen.get_current_token_for_writer(instance_name)

    def minimal_local_current_token(self) -> Token:
        return self._stream_id_gen.get_minimal_local_current_token()

    def can_discard_position(
        self, instance_name: str, prev_token: int, new_token: int
    ) -> bool:
        # These streams can't go backwards, so we know we can ignore any
        # positions where the tokens are from before the current token.

        return new_token <= self.current_token(instance_name)


def current_token_without_instance(
    current_token: Callable[[], int]
) -> Callable[[str], int]:
    """Takes a current token callback function for a single writer stream
    that doesn't take an instance name parameter and wraps it in a function that
    does accept an instance name parameter but ignores it.
    """
    return lambda instance_name: current_token()


def make_http_update_function(hs: "HomeServer", stream_name: str) -> UpdateFunction:
    """Makes a suitable function for use as an `update_function` that queries
    the master process for updates.
    """

    client = ReplicationGetStreamUpdates.make_client(hs)

    async def update_function(
        instance_name: str, from_token: int, upto_token: int, limit: int
    ) -> StreamUpdateResult:
        result = await client(
            instance_name=instance_name,
            stream_name=stream_name,
            from_token=from_token,
            upto_token=upto_token,
        )
        return result["updates"], result["upto_token"], result["limited"]

    return update_function


class BackfillStream(Stream):
    """We fetched some old events and either we had never seen that event before
    or it went from being an outlier to not.
    """

    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class BackfillStreamRow:
        event_id: str
        room_id: str
        type: str
        state_key: Optional[str]
        redacts: Optional[str]
        relates_to: Optional[str]

    NAME = "backfill"
    ROW_TYPE = BackfillStreamRow

    def __init__(self, hs: "HomeServer"):
        self.store = hs.get_datastores().main
        super().__init__(
            hs.get_instance_name(),
            self.store.get_all_new_backfill_event_rows,
        )

    def current_token(self, instance_name: str) -> Token:
        # The backfill stream over replication operates on *positive* numbers,
        # which means we need to negate it.
        return -self.store._backfill_id_gen.get_current_token_for_writer(instance_name)

    def minimal_local_current_token(self) -> Token:
        # The backfill stream over replication operates on *positive* numbers,
        # which means we need to negate it.
        return -self.store._backfill_id_gen.get_minimal_local_current_token()

    def can_discard_position(
        self, instance_name: str, prev_token: int, new_token: int
    ) -> bool:
        # Backfill stream can't go backwards, so we know we can ignore any
        # positions where the tokens are from before the current token.

        return new_token <= self.current_token(instance_name)


class PresenceStream(_StreamFromIdGen):
    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class PresenceStreamRow:
        user_id: str
        state: str
        last_active_ts: int
        last_federation_update_ts: int
        last_user_sync_ts: int
        status_msg: str
        currently_active: bool

    NAME = "presence"
    ROW_TYPE = PresenceStreamRow

    def __init__(self, hs: "HomeServer"):
        store = hs.get_datastores().main

        if hs.get_instance_name() in hs.config.worker.writers.presence:
            # on the presence writer, query the presence handler
            presence_handler = hs.get_presence_handler()

            from synapse.handlers.presence import PresenceHandler

            assert isinstance(presence_handler, PresenceHandler)

            update_function: UpdateFunction = presence_handler.get_all_presence_updates
        else:
            # Query presence writer process
            update_function = make_http_update_function(hs, self.NAME)

        super().__init__(
            hs.get_instance_name(), update_function, store._presence_id_gen
        )


class PresenceFederationStream(Stream):
    """A stream used to send ad hoc presence updates over federation.

    Streams the remote destination and the user ID of the presence state to
    send.
    """

    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class PresenceFederationStreamRow:
        destination: str
        user_id: str

    NAME = "presence_federation"
    ROW_TYPE = PresenceFederationStreamRow

    def __init__(self, hs: "HomeServer"):
        self._federation_queue = hs.get_presence_handler().get_federation_queue()
        super().__init__(
            hs.get_instance_name(),
            self._federation_queue.get_replication_rows,
        )

    def current_token(self, instance_name: str) -> Token:
        return self._federation_queue.get_current_token(instance_name)

    def minimal_local_current_token(self) -> Token:
        return self._federation_queue.get_current_token(self.local_instance_name)


class TypingStream(Stream):
    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class TypingStreamRow:
        """
        An entry in the typing stream.
        Describes all the users that are 'typing' right now in one room.

        When a user stops typing, it will be streamed as a new update with that
        user absent; you can think of the `user_ids` list as overwriting the
        entire list that was there previously.
        """

        # The room that this update is for.
        room_id: str

        # All the users that are 'typing' right now in the specified room.
        user_ids: List[str]

    NAME = "typing"
    ROW_TYPE = TypingStreamRow

    def __init__(self, hs: "HomeServer"):
        if hs.get_instance_name() in hs.config.worker.writers.typing:
            # On the writer, query the typing handler
            typing_writer_handler = hs.get_typing_writer_handler()
            update_function: Callable[
                [str, int, int, int], Awaitable[Tuple[List[Tuple[int, Any]], int, bool]]
            ] = typing_writer_handler.get_all_typing_updates
            self.current_token_function = typing_writer_handler.get_current_token
        else:
            # Query the typing writer process
            update_function = make_http_update_function(hs, self.NAME)
            self.current_token_function = hs.get_typing_handler().get_current_token

        super().__init__(
            hs.get_instance_name(),
            update_function,
        )

    def current_token(self, instance_name: str) -> Token:
        return self.current_token_function()

    def minimal_local_current_token(self) -> Token:
        return self.current_token_function()


class ReceiptsStream(_StreamFromIdGen):
    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class ReceiptsStreamRow:
        room_id: str
        receipt_type: str
        user_id: str
        event_id: str
        thread_id: Optional[str]
        data: dict

    NAME = "receipts"
    ROW_TYPE = ReceiptsStreamRow

    def __init__(self, hs: "HomeServer"):
        store = hs.get_datastores().main
        super().__init__(
            hs.get_instance_name(),
            store.get_all_updated_receipts,
            store._receipts_id_gen,
        )


class PushRulesStream(_StreamFromIdGen):
    """A user has changed their push rules"""

    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class PushRulesStreamRow:
        user_id: str

    NAME = "push_rules"
    ROW_TYPE = PushRulesStreamRow

    def __init__(self, hs: "HomeServer"):
        store = hs.get_datastores().main

        super().__init__(
            hs.get_instance_name(),
            store.get_all_push_rule_updates,
            store._push_rules_stream_id_gen,
        )


class PushersStream(_StreamFromIdGen):
    """A user has added/changed/removed a pusher"""

    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class PushersStreamRow:
        user_id: str
        app_id: str
        pushkey: str
        deleted: bool

    NAME = "pushers"
    ROW_TYPE = PushersStreamRow

    def __init__(self, hs: "HomeServer"):
        store = hs.get_datastores().main

        super().__init__(
            hs.get_instance_name(),
            store.get_all_updated_pushers_rows,
            store._pushers_id_gen,
        )


class CachesStream(Stream):
    """A cache was invalidated on the master and no other stream would invalidate
    the cache on the workers
    """

    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class CachesStreamRow:
        """Stream to inform workers they should invalidate their cache.

        Attributes:
            cache_func: Name of the cached function.
            keys: The entry in the cache to invalidate. If None then will
                invalidate all.
            invalidation_ts: Timestamp of when the invalidation took place.
        """

        cache_func: str
        keys: Optional[List[Any]]
        invalidation_ts: int

    NAME = "caches"
    ROW_TYPE = CachesStreamRow

    def __init__(self, hs: "HomeServer"):
        self.store = hs.get_datastores().main
        super().__init__(
            hs.get_instance_name(),
            self.store.get_all_updated_caches,
        )

    def current_token(self, instance_name: str) -> Token:
        return self.store.get_cache_stream_token_for_writer(instance_name)

    def minimal_local_current_token(self) -> Token:
        if self.store._cache_id_gen:
            return self.store._cache_id_gen.get_minimal_local_current_token()
        return self.current_token(self.local_instance_name)

    def can_discard_position(
        self, instance_name: str, prev_token: int, new_token: int
    ) -> bool:
        # Caches streams can't go backwards, so we know we can ignore any
        # positions where the tokens are from before the current token.

        return new_token <= self.current_token(instance_name)


class DeviceListsStream(_StreamFromIdGen):
    """Either a user has updated their devices or a remote server needs to be
    told about a device update.
    """

    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class DeviceListsStreamRow:
        entity: str
        # Indicates that a user has signed their own device with their user-signing key
        is_signature: bool

    NAME = "device_lists"
    ROW_TYPE = DeviceListsStreamRow

    def __init__(self, hs: "HomeServer"):
        self.store = hs.get_datastores().main
        super().__init__(
            hs.get_instance_name(),
            self._update_function,
            self.store._device_list_id_gen,
        )

    async def _update_function(
        self,
        instance_name: str,
        from_token: Token,
        current_token: Token,
        target_row_count: int,
    ) -> StreamUpdateResult:
        (
            device_updates,
            devices_to_token,
            devices_limited,
        ) = await self.store.get_all_device_list_changes_for_remotes(
            instance_name, from_token, current_token, target_row_count
        )

        (
            signatures_updates,
            signatures_to_token,
            signatures_limited,
        ) = await self.store.get_all_user_signature_changes_for_remotes(
            instance_name, from_token, current_token, target_row_count
        )

        upper_limit_token = current_token
        if devices_limited:
            upper_limit_token = min(upper_limit_token, devices_to_token)
        if signatures_limited:
            upper_limit_token = min(upper_limit_token, signatures_to_token)

        device_updates = [
            (stream_id, (entity, False))
            for stream_id, (entity,) in device_updates
            if stream_id <= upper_limit_token
        ]

        signatures_updates = [
            (stream_id, (entity, True))
            for stream_id, (entity,) in signatures_updates
            if stream_id <= upper_limit_token
        ]

        updates = list(
            heapq.merge(device_updates, signatures_updates, key=lambda row: row[0])
        )

        return updates, upper_limit_token, devices_limited or signatures_limited


class ToDeviceStream(_StreamFromIdGen):
    """New to_device messages for a client"""

    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class ToDeviceStreamRow:
        entity: str

    NAME = "to_device"
    ROW_TYPE = ToDeviceStreamRow

    def __init__(self, hs: "HomeServer"):
        store = hs.get_datastores().main
        super().__init__(
            hs.get_instance_name(),
            store.get_all_new_device_messages,
            store._to_device_msg_id_gen,
        )


class AccountDataStream(_StreamFromIdGen):
    """Global or per room account data was changed"""

    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class AccountDataStreamRow:
        user_id: str
        room_id: Optional[str]
        data_type: str

    NAME = "account_data"
    ROW_TYPE = AccountDataStreamRow

    def __init__(self, hs: "HomeServer"):
        self.store = hs.get_datastores().main
        super().__init__(
            hs.get_instance_name(),
            self._update_function,
            self.store._account_data_id_gen,
        )

    async def _update_function(
        self, instance_name: str, from_token: int, to_token: int, limit: int
    ) -> StreamUpdateResult:
        limited = False
        global_results = await self.store.get_updated_global_account_data(
            from_token, to_token, limit
        )

        # if the global results hit the limit, we'll need to limit the room results to
        # the same stream token.
        if len(global_results) >= limit:
            to_token = global_results[-1][0]
            limited = True

        room_results = await self.store.get_updated_room_account_data(
            from_token, to_token, limit
        )

        # likewise, if the room results hit the limit, limit the global results to
        # the same stream token.
        if len(room_results) >= limit:
            to_token = room_results[-1][0]
            limited = True

        tags, tag_to_token, tags_limited = await self.store.get_all_updated_tags(
            instance_name,
            from_token,
            to_token,
            limit,
        )

        # again, if the tag results hit the limit, limit the global results to
        # the same stream token.
        if tags_limited:
            to_token = tag_to_token
            limited = True

        # convert the global results to the right format, and limit them to the to_token
        # at the same time
        global_rows = (
            (stream_id, (user_id, None, account_data_type))
            for stream_id, user_id, account_data_type in global_results
            if stream_id <= to_token
        )

        room_rows = (
            (stream_id, (user_id, room_id, account_data_type))
            for stream_id, user_id, room_id, account_data_type in room_results
            if stream_id <= to_token
        )

        tag_rows = (
            (stream_id, (user_id, room_id, AccountDataTypes.TAG))
            for stream_id, user_id, room_id in tags
            if stream_id <= to_token
        )

        # We need to return a sorted list, so merge them together.
        #
        # Note: We order only by the stream ID to work around a bug where the
        # same stream ID could appear in both `global_rows` and `room_rows`,
        # leading to a comparison between the data tuples. The comparison could
        # fail due to attempting to compare the `room_id` which results in a
        # `TypeError` from comparing a `str` vs `None`.
        updates = list(
            heapq.merge(room_rows, global_rows, tag_rows, key=lambda row: row[0])
        )
        return updates, to_token, limited