# -*- coding: utf-8 -*-
# Copyright 2014, 2015 OpenMarket 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.

from ._base import SQLBaseStore
from synapse.util.caches.descriptors import cachedInlineCallbacks

from twisted.internet import defer

from synapse.util import unwrapFirstError

from blist import sorteddict
import logging
import ujson as json


logger = logging.getLogger(__name__)


class ReceiptsStore(SQLBaseStore):
    def __init__(self, hs):
        super(ReceiptsStore, self).__init__(hs)

        self._receipts_stream_cache = _RoomStreamChangeCache()

    @defer.inlineCallbacks
    def get_linearized_receipts_for_rooms(self, room_ids, to_key, from_key=None):
        """Get receipts for multiple rooms for sending to clients.

        Args:
            room_ids (list): List of room_ids.
            to_key (int): Max stream id to fetch receipts upto.
            from_key (int): Min stream id to fetch receipts from. None fetches
                from the start.

        Returns:
            list: A list of receipts.
        """
        room_ids = set(room_ids)

        if from_key:
            room_ids = yield self._receipts_stream_cache.get_rooms_changed(
                self, room_ids, from_key
            )

        results = yield defer.gatherResults(
            [
                self.get_linearized_receipts_for_room(
                    room_id, to_key, from_key=from_key
                )
                for room_id in room_ids
            ],
            consumeErrors=True,
        ).addErrback(unwrapFirstError)

        defer.returnValue([ev for res in results for ev in res])

    @defer.inlineCallbacks
    def get_linearized_receipts_for_room(self, room_id, to_key, from_key=None):
        """Get receipts for a single room for sending to clients.

        Args:
            room_ids (str): The room id.
            to_key (int): Max stream id to fetch receipts upto.
            from_key (int): Min stream id to fetch receipts from. None fetches
                from the start.

        Returns:
            list: A list of receipts.
        """
        def f(txn):
            if from_key:
                sql = (
                    "SELECT * FROM receipts_linearized WHERE"
                    " room_id = ? AND stream_id > ? AND stream_id <= ?"
                )

                txn.execute(
                    sql,
                    (room_id, from_key, to_key)
                )
            else:
                sql = (
                    "SELECT * FROM receipts_linearized WHERE"
                    " room_id = ? AND stream_id <= ?"
                )

                txn.execute(
                    sql,
                    (room_id, to_key)
                )

            rows = self.cursor_to_dict(txn)

            return rows

        rows = yield self.runInteraction(
            "get_linearized_receipts_for_room", f
        )

        if not rows:
            defer.returnValue([])

        content = {}
        for row in rows:
            content.setdefault(
                row["event_id"], {}
            ).setdefault(
                row["receipt_type"], {}
            )[row["user_id"]] = json.loads(row["data"])

        defer.returnValue([{
            "type": "m.receipt",
            "room_id": room_id,
            "content": content,
        }])

    def get_max_receipt_stream_id(self):
        return self._receipts_id_gen.get_max_token(self)

    @cachedInlineCallbacks()
    def get_graph_receipts_for_room(self, room_id):
        """Get receipts for sending to remote servers.
        """
        rows = yield self._simple_select_list(
            table="receipts_graph",
            keyvalues={"room_id": room_id},
            retcols=["receipt_type", "user_id", "event_id"],
            desc="get_linearized_receipts_for_room",
        )

        result = {}
        for row in rows:
            result.setdefault(
                row["user_id"], {}
            ).setdefault(
                row["receipt_type"], []
            ).append(row["event_id"])

        defer.returnValue(result)

    def insert_linearized_receipt_txn(self, txn, room_id, receipt_type,
                                      user_id, event_id, data, stream_id):

        # We don't want to clobber receipts for more recent events, so we
        # have to compare orderings of existing receipts
        sql = (
            "SELECT topological_ordering, stream_ordering, event_id FROM events"
            " INNER JOIN receipts_linearized as r USING (event_id, room_id)"
            " WHERE r.room_id = ? AND r.receipt_type = ? AND r.user_id = ?"
        )

        txn.execute(sql, (room_id, receipt_type, user_id))
        results = txn.fetchall()

        if results:
            res = self._simple_select_one_txn(
                txn,
                table="events",
                retcols=["topological_ordering", "stream_ordering"],
                keyvalues={"event_id": event_id},
            )
            topological_ordering = int(res["topological_ordering"])
            stream_ordering = int(res["stream_ordering"])

            for to, so, _ in results:
                if int(to) > topological_ordering:
                    return False
                elif int(to) == topological_ordering and int(so) >= stream_ordering:
                    return False

        self._simple_delete_txn(
            txn,
            table="receipts_linearized",
            keyvalues={
                "room_id": room_id,
                "receipt_type": receipt_type,
                "user_id": user_id,
            }
        )

        self._simple_insert_txn(
            txn,
            table="receipts_linearized",
            values={
                "stream_id": stream_id,
                "room_id": room_id,
                "receipt_type": receipt_type,
                "user_id": user_id,
                "event_id": event_id,
                "data": json.dumps(data),
            }
        )

        return True

    @defer.inlineCallbacks
    def insert_receipt(self, room_id, receipt_type, user_id, event_ids, data):
        """Insert a receipt, either from local client or remote server.

        Automatically does conversion between linearized and graph
        representations.
        """
        if not event_ids:
            return

        if len(event_ids) == 1:
            linearized_event_id = event_ids[0]
        else:
            # we need to points in graph -> linearized form.
            # TODO: Make this better.
            def graph_to_linear(txn):
                query = (
                    "SELECT event_id WHERE room_id = ? AND stream_ordering IN ("
                    " SELECT max(stream_ordering) WHERE event_id IN (%s)"
                    ")"
                ) % (",".join(["?"] * len(event_ids)))

                txn.execute(query, [room_id] + event_ids)
                rows = txn.fetchall()
                if rows:
                    return rows[0][0]
                else:
                    raise RuntimeError("Unrecognized event_ids: %r" % (event_ids,))

            linearized_event_id = yield self.runInteraction(
                "insert_receipt_conv", graph_to_linear
            )

        stream_id_manager = yield self._receipts_id_gen.get_next(self)
        with stream_id_manager as stream_id:
            yield self._receipts_stream_cache.room_has_changed(
                self, room_id, stream_id
            )
            have_persisted = yield self.runInteraction(
                "insert_linearized_receipt",
                self.insert_linearized_receipt_txn,
                room_id, receipt_type, user_id, linearized_event_id,
                data,
                stream_id=stream_id,
            )

            if not have_persisted:
                defer.returnValue(None)

        yield self.insert_graph_receipt(
            room_id, receipt_type, user_id, event_ids, data
        )

        max_persisted_id = yield self._stream_id_gen.get_max_token(self)
        defer.returnValue((stream_id, max_persisted_id))

    def insert_graph_receipt(self, room_id, receipt_type, user_id, event_ids,
                             data):
        return self.runInteraction(
            "insert_graph_receipt",
            self.insert_graph_receipt_txn,
            room_id, receipt_type, user_id, event_ids, data
        )

    def insert_graph_receipt_txn(self, txn, room_id, receipt_type,
                                 user_id, event_ids, data):
        self._simple_delete_txn(
            txn,
            table="receipts_graph",
            keyvalues={
                "room_id": room_id,
                "receipt_type": receipt_type,
                "user_id": user_id,
            }
        )
        self._simple_insert_txn(
            txn,
            table="receipts_graph",
            values={
                "room_id": room_id,
                "receipt_type": receipt_type,
                "user_id": user_id,
                "event_ids": json.dumps(event_ids),
                "data": json.dumps(data),
            }
        )


class _RoomStreamChangeCache(object):
    """Keeps track of the stream_id of the latest change in rooms.

    Given a list of rooms and stream key, it will give a subset of rooms that
    may have changed since that key. If the key is too old then the cache
    will simply return all rooms.
    """
    def __init__(self, size_of_cache=10000):
        self._size_of_cache = size_of_cache
        self._room_to_key = {}
        self._cache = sorteddict()
        self._earliest_key = None

    @defer.inlineCallbacks
    def get_rooms_changed(self, store, room_ids, key):
        """Returns subset of room ids that have had new receipts since the
        given key. If the key is too old it will just return the given list.
        """
        if key > (yield self._get_earliest_key(store)):
            keys = self._cache.keys()
            i = keys.bisect_right(key)

            result = set(
                self._cache[k] for k in keys[i:]
            ).intersection(room_ids)
        else:
            result = room_ids

        defer.returnValue(result)

    @defer.inlineCallbacks
    def room_has_changed(self, store, room_id, key):
        """Informs the cache that the room has been changed at the given key.
        """
        if key > (yield self._get_earliest_key(store)):
            old_key = self._room_to_key.get(room_id, None)
            if old_key:
                key = max(key, old_key)
                self._cache.pop(old_key, None)
            self._cache[key] = room_id

            while len(self._cache) > self._size_of_cache:
                k, r = self._cache.popitem()
                self._earliest_key = max(k, self._earliest_key)
                self._room_to_key.pop(r, None)

    @defer.inlineCallbacks
    def _get_earliest_key(self, store):
        if self._earliest_key is None:
            self._earliest_key = yield store.get_max_receipt_stream_id()
            self._earliest_key = int(self._earliest_key)

        defer.returnValue(self._earliest_key)