# -*- coding: utf-8 -*-
# Copyright 2017 Vector Creations Ltd
# Copyright 2019 New Vector Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import logging
from collections import namedtuple
from typing import Any, Awaitable, Callable, List, Optional, Tuple

import attr

from synapse.replication.http.streams import ReplicationGetStreamUpdates

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 = 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(object):
    """Base class for the streams.

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

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

    @classmethod
    def parse_row(cls, row: StreamRow):
        """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,
        current_token_function: Callable[[], Token],
        update_function: UpdateFunction,
    ):
        """Instantiate a Stream

        current_token_function and update_function are callbacks which should be
        implemented by subclasses.

        current_token_function is called to get the current token of the underlying
        stream. It is only meaningful on the process that is the source of the
        replication stream (ie, usually the master).

        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.current_token = current_token_function
        self.update_function = update_function

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

    def discard_updates_and_advance(self):
        """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()

    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, and `limited` is whether there are more updates
            to fetch.
        """
        current_token = self.current_token()
        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


def db_query_to_update_function(
    query_function: Callable[[Token, Token, int], Awaitable[List[tuple]]]
) -> UpdateFunction:
    """Wraps a db query function which returns a list of rows to make it
    suitable for use as an `update_function` for the Stream class
    """

    async def update_function(instance_name, from_token, upto_token, limit):
        rows = await query_function(from_token, upto_token, limit)
        updates = [(row[0], row[1:]) for row in rows]
        limited = False
        if len(updates) >= limit:
            upto_token = updates[-1][0]
            limited = True

        return updates, upto_token, limited

    return update_function


def make_http_update_function(hs, 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.
    """

    BackfillStreamRow = namedtuple(
        "BackfillStreamRow",
        (
            "event_id",  # str
            "room_id",  # str
            "type",  # str
            "state_key",  # str, optional
            "redacts",  # str, optional
            "relates_to",  # str, optional
        ),
    )

    NAME = "backfill"
    ROW_TYPE = BackfillStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            store.get_current_backfill_token,
            db_query_to_update_function(store.get_all_new_backfill_event_rows),
        )


class PresenceStream(Stream):
    PresenceStreamRow = namedtuple(
        "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):
        store = hs.get_datastore()

        if hs.config.worker_app is None:
            # on the master, query the presence handler
            presence_handler = hs.get_presence_handler()
            update_function = db_query_to_update_function(
                presence_handler.get_all_presence_updates
            )
        else:
            # Query master process
            update_function = make_http_update_function(hs, self.NAME)

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


class TypingStream(Stream):
    TypingStreamRow = namedtuple(
        "TypingStreamRow", ("room_id", "user_ids")  # str  # list(str)
    )

    NAME = "typing"
    ROW_TYPE = TypingStreamRow

    def __init__(self, hs):
        typing_handler = hs.get_typing_handler()

        if hs.config.worker_app is None:
            # on the master, query the typing handler
            update_function = db_query_to_update_function(
                typing_handler.get_all_typing_updates
            )
        else:
            # Query master process
            update_function = make_http_update_function(hs, self.NAME)

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


class ReceiptsStream(Stream):
    ReceiptsStreamRow = namedtuple(
        "ReceiptsStreamRow",
        (
            "room_id",  # str
            "receipt_type",  # str
            "user_id",  # str
            "event_id",  # str
            "data",  # dict
        ),
    )

    NAME = "receipts"
    ROW_TYPE = ReceiptsStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            store.get_max_receipt_stream_id,
            db_query_to_update_function(store.get_all_updated_receipts),
        )


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

    PushRulesStreamRow = namedtuple("PushRulesStreamRow", ("user_id",))  # str

    NAME = "push_rules"
    ROW_TYPE = PushRulesStreamRow

    def __init__(self, hs):
        self.store = hs.get_datastore()
        super(PushRulesStream, self).__init__(
            hs.get_instance_name(), self._current_token, self._update_function
        )

    def _current_token(self) -> int:
        push_rules_token, _ = self.store.get_push_rules_stream_token()
        return push_rules_token

    async def _update_function(
        self, instance_name: str, from_token: Token, to_token: Token, limit: int
    ):
        rows = await self.store.get_all_push_rule_updates(from_token, to_token, limit)

        limited = False
        if len(rows) == limit:
            to_token = rows[-1][0]
            limited = True

        return [(row[0], (row[2],)) for row in rows], to_token, limited


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

    PushersStreamRow = namedtuple(
        "PushersStreamRow",
        ("user_id", "app_id", "pushkey", "deleted"),  # str  # str  # str  # bool
    )

    NAME = "pushers"
    ROW_TYPE = PushersStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()

        super().__init__(
            hs.get_instance_name(),
            store.get_pushers_stream_token,
            db_query_to_update_function(store.get_all_updated_pushers_rows),
        )


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

    @attr.s
    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 = attr.ib(type=str)
        keys = attr.ib(type=Optional[List[Any]])
        invalidation_ts = attr.ib(type=int)

    NAME = "caches"
    ROW_TYPE = CachesStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            store.get_cache_stream_token,
            db_query_to_update_function(store.get_all_updated_caches),
        )


class PublicRoomsStream(Stream):
    """The public rooms list changed
    """

    PublicRoomsStreamRow = namedtuple(
        "PublicRoomsStreamRow",
        (
            "room_id",  # str
            "visibility",  # str
            "appservice_id",  # str, optional
            "network_id",  # str, optional
        ),
    )

    NAME = "public_rooms"
    ROW_TYPE = PublicRoomsStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            store.get_current_public_room_stream_id,
            db_query_to_update_function(store.get_all_new_public_rooms),
        )


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

    @attr.s
    class DeviceListsStreamRow:
        entity = attr.ib(type=str)

    NAME = "device_lists"
    ROW_TYPE = DeviceListsStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            store.get_device_stream_token,
            db_query_to_update_function(store.get_all_device_list_changes_for_remotes),
        )


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

    ToDeviceStreamRow = namedtuple("ToDeviceStreamRow", ("entity",))  # str

    NAME = "to_device"
    ROW_TYPE = ToDeviceStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            store.get_to_device_stream_token,
            db_query_to_update_function(store.get_all_new_device_messages),
        )


class TagAccountDataStream(Stream):
    """Someone added/removed a tag for a room
    """

    TagAccountDataStreamRow = namedtuple(
        "TagAccountDataStreamRow", ("user_id", "room_id", "data")  # str  # str  # dict
    )

    NAME = "tag_account_data"
    ROW_TYPE = TagAccountDataStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            store.get_max_account_data_stream_id,
            db_query_to_update_function(store.get_all_updated_tags),
        )


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

    AccountDataStreamRow = namedtuple(
        "AccountDataStream", ("user_id", "room_id", "data_type")  # str  # str  # str
    )

    NAME = "account_data"
    ROW_TYPE = AccountDataStreamRow

    def __init__(self, hs):
        self.store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            self.store.get_max_account_data_stream_id,
            db_query_to_update_function(self._update_function),
        )

    async def _update_function(self, from_token, to_token, limit):
        global_results, room_results = await self.store.get_all_updated_account_data(
            from_token, from_token, to_token, limit
        )

        results = list(room_results)
        results.extend(
            (stream_id, user_id, None, account_data_type)
            for stream_id, user_id, account_data_type in global_results
        )

        return results


class GroupServerStream(Stream):
    GroupsStreamRow = namedtuple(
        "GroupsStreamRow",
        ("group_id", "user_id", "type", "content"),  # str  # str  # str  # dict
    )

    NAME = "groups"
    ROW_TYPE = GroupsStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            store.get_group_stream_token,
            db_query_to_update_function(store.get_all_groups_changes),
        )


class UserSignatureStream(Stream):
    """A user has signed their own device with their user-signing key
    """

    UserSignatureStreamRow = namedtuple("UserSignatureStreamRow", ("user_id"))  # str

    NAME = "user_signature"
    ROW_TYPE = UserSignatureStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            hs.get_instance_name(),
            store.get_device_stream_token,
            db_query_to_update_function(
                store.get_all_user_signature_changes_for_remotes
            ),
        )