# -*- 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, cached, cachedInlineCallbacks, cachedList

from twisted.internet import defer

from synapse.util.stringutils import random_string

import logging

logger = logging.getLogger(__name__)


class StateStore(SQLBaseStore):
    """ Keeps track of the state at a given event.

    This is done by the concept of `state groups`. Every event is a assigned
    a state group (identified by an arbitrary string), which references a
    collection of state events. The current state of an event is then the
    collection of state events referenced by the event's state group.

    Hence, every change in the current state causes a new state group to be
    generated. However, if no change happens (e.g., if we get a message event
    with only one parent it inherits the state group from its parent.)

    There are three tables:
      * `state_groups`: Stores group name, first event with in the group and
        room id.
      * `event_to_state_groups`: Maps events to state groups.
      * `state_groups_state`: Maps state group to state events.
    """

    @defer.inlineCallbacks
    def get_state_groups(self, room_id, event_ids):
        """ Get the state groups for the given list of event_ids

        The return value is a dict mapping group names to lists of events.
        """
        if not event_ids:
            defer.returnValue({})

        event_to_groups = yield self._get_state_group_for_events(
            room_id, event_ids,
        )

        groups = set(event_to_groups.values())

        group_to_state = yield self._get_state_for_groups(groups)

        defer.returnValue({
            group: state_map.values()
            for group, state_map in group_to_state.items()
        })

    def _fetch_events_for_group(self, key, events):
        return self._get_events(
            events, get_prev_content=False
        ).addCallback(
            lambda evs: (key, evs)
        )

    def _store_state_groups_txn(self, txn, event, context):
        return self._store_mult_state_groups_txn(txn, [(event, context)])

    def _store_mult_state_groups_txn(self, txn, events_and_contexts):
        state_groups = {}
        for event, context in events_and_contexts:
            if context.current_state is None:
                continue

            if context.state_group is not None:
                state_groups[event.event_id] = context.state_group
                continue

            state_events = dict(context.current_state)

            if event.is_state():
                state_events[(event.type, event.state_key)] = event

            state_group = self._state_groups_id_gen.get_next_txn(txn)
            self._simple_insert_txn(
                txn,
                table="state_groups",
                values={
                    "id": state_group,
                    "room_id": event.room_id,
                    "event_id": event.event_id,
                },
            )

            self._simple_insert_many_txn(
                txn,
                table="state_groups_state",
                values=[
                    {
                        "state_group": state_group,
                        "room_id": state.room_id,
                        "type": state.type,
                        "state_key": state.state_key,
                        "event_id": state.event_id,
                    }
                    for state in state_events.values()
                ],
            )
            state_groups[event.event_id] = state_group

        self._simple_insert_many_txn(
            txn,
            table="event_to_state_groups",
            values=[
                {
                    "state_group": state_groups[event.event_id],
                    "event_id": event.event_id,
                }
                for event, context in events_and_contexts
                if context.current_state is not None
            ],
        )

    @defer.inlineCallbacks
    def get_current_state(self, room_id, event_type=None, state_key=""):
        if event_type and state_key is not None:
            result = yield self.get_current_state_for_key(
                room_id, event_type, state_key
            )
            defer.returnValue(result)

        def f(txn):
            sql = (
                "SELECT event_id FROM current_state_events"
                " WHERE room_id = ? "
            )

            if event_type and state_key is not None:
                sql += " AND type = ? AND state_key = ? "
                args = (room_id, event_type, state_key)
            elif event_type:
                sql += " AND type = ?"
                args = (room_id, event_type)
            else:
                args = (room_id, )

            txn.execute(sql, args)
            results = txn.fetchall()

            return [r[0] for r in results]

        event_ids = yield self.runInteraction("get_current_state", f)
        events = yield self._get_events(event_ids, get_prev_content=False)
        defer.returnValue(events)

    @cachedInlineCallbacks(num_args=3)
    def get_current_state_for_key(self, room_id, event_type, state_key):
        def f(txn):
            sql = (
                "SELECT event_id FROM current_state_events"
                " WHERE room_id = ? AND type = ? AND state_key = ?"
            )

            args = (room_id, event_type, state_key)
            txn.execute(sql, args)
            results = txn.fetchall()
            return [r[0] for r in results]
        event_ids = yield self.runInteraction("get_current_state_for_key", f)
        events = yield self._get_events(event_ids, get_prev_content=False)
        defer.returnValue(events)

    def _get_state_groups_from_group(self, group, types):
        def f(txn):
            if types is not None:
                where_clause = "AND (%s)" % (
                    " OR ".join(["(type = ? AND state_key = ?)"] * len(types)),
                )
            else:
                where_clause = ""

            sql = (
                "SELECT event_id FROM state_groups_state WHERE"
                " state_group = ? %s"
            ) % (where_clause,)

            args = [group]
            if types is not None:
                args.extend([i for typ in types for i in typ])

            txn.execute(sql, args)

            return [r[0] for r in txn.fetchall()]

        return self.runInteraction(
            "_get_state_groups_from_group",
            f,
        )

    def _get_state_groups_from_groups(self, groups_and_types):
        def f(txn):
            results = {}
            for group, types in groups_and_types:
                if types is not None:
                    where_clause = "AND (%s)" % (
                        " OR ".join(["(type = ? AND state_key = ?)"] * len(types)),
                    )
                else:
                    where_clause = ""

                sql = (
                    "SELECT event_id FROM state_groups_state WHERE"
                    " state_group = ? %s"
                ) % (where_clause,)

                args = [group]
                if types is not None:
                    args.extend([i for typ in types for i in typ])

                txn.execute(sql, args)

                results[group] = [
                    r[0]
                    for r in txn.fetchall()
                ]

            return results

        return self.runInteraction(
            "_get_state_groups_from_groups",
            f,
        )

    @cached(num_args=3, lru=True, max_entries=10000)
    def _get_state_for_event_id(self, room_id, event_id, types):
        def f(txn):
            type_and_state_sql = " OR ".join([
                "(type = ? AND state_key = ?)"
                if typ[1] is not None
                else "type = ?"
                for typ in types
            ])

            sql = (
                "SELECT e.event_id, sg.state_group, sg.event_id"
                " FROM state_groups_state as sg"
                " INNER JOIN event_to_state_groups as e"
                " ON e.state_group = sg.state_group"
                " WHERE e.event_id = ? AND (%s)"
            ) % (type_and_state_sql,)

            args = [event_id]
            for typ, state_key in types:
                args.extend(
                    [typ, state_key] if state_key is not None else [typ]
                )
            txn.execute(sql, args)

            return event_id, [
                r[0]
                for r in txn.fetchall()
            ]

        return self.runInteraction(
            "_get_state_for_event_id",
            f,
        )

    @defer.inlineCallbacks
    def get_state_for_events(self, room_id, event_ids, types):
        """Given a list of event_ids and type tuples, return a list of state
        dicts for each event. The state dicts will only have the type/state_keys
        that are in the `types` list.

        Args:
            room_id (str)
            event_ids (list)
            types (list): List of (type, state_key) tuples which are used to
                filter the state fetched. `state_key` may be None, which matches
                any `state_key`

        Returns:
            deferred: A list of dicts corresponding to the event_ids given.
            The dicts are mappings from (type, state_key) -> state_events
        """
        event_to_groups = yield self._get_state_group_for_events(
            room_id, event_ids,
        )

        groups = set(event_to_groups.values())

        group_to_state = yield self._get_state_for_groups(
            groups, types
        )

        event_to_state = {
            event_id: group_to_state[group]
            for event_id, group in event_to_groups.items()
        }

        defer.returnValue([
            event_to_state[event]
            for event in event_ids
        ])

    @cached(num_args=2, lru=True, max_entries=100000)
    def _get_state_group_for_event(self, room_id, event_id):
        return self._simple_select_one_onecol(
            table="event_to_state_groups",
            keyvalues={
                "event_id": event_id,
            },
            retcol="state_group",
            allow_none=True,
            desc="_get_state_group_for_event",
        )

    @cachedList(cache=_get_state_group_for_event.cache, list_name="event_ids",
                num_args=2)
    def _get_state_group_for_events(self, room_id, event_ids):
        def f(txn):
            results = {}
            for event_id in event_ids:
                results[event_id] = self._simple_select_one_onecol_txn(
                    txn,
                    table="event_to_state_groups",
                    keyvalues={
                        "event_id": event_id,
                    },
                    retcol="state_group",
                    allow_none=True,
                )

            return results

        return self.runInteraction(
            "_get_state_group_for_events",
            f,
        )

    def _get_state_for_group_from_cache(self, group, types=None):
        is_all, state_dict = self._state_group_cache.get(group)

        type_to_key = {}
        missing_types = set()
        if types is not None:
            for typ, state_key in types:
                if state_key is None:
                    type_to_key[typ] = None
                    missing_types.add((typ, state_key))
                else:
                    if type_to_key.get(typ, object()) is not None:
                        type_to_key.setdefault(typ, set()).add(state_key)

                    if (typ, state_key) not in state_dict:
                        missing_types.add((typ, state_key))

        if is_all and types is None:
            return state_dict, missing_types

        if is_all or (types is not None and not missing_types):
            sentinel = object()

            def include(typ, state_key):
                valid_state_keys = type_to_key.get(typ, sentinel)
                if valid_state_keys is sentinel:
                    return False
                if valid_state_keys is None:
                    return True
                if state_key in valid_state_keys:
                    return True
                return False

            return {
                k: v
                for k, v in state_dict.items()
                if v and include(k[0], k[1])
            }, missing_types

        return {}, missing_types

    @defer.inlineCallbacks
    def _get_state_for_groups(self, groups, types=None):
        results = {}
        missing_groups_and_types = []
        for group in groups:
            state_dict, missing_types = self._get_state_for_group_from_cache(
                group, types
            )

            if types is not None and not missing_types:
                results[group] = {
                    key: value
                    for key, value in state_dict.items()
                    if value
                }
            else:
                missing_groups_and_types.append((
                    group,
                    missing_types if types else None
                ))

        if not missing_groups_and_types:
            defer.returnValue(results)

        # Okay, so we have some missing_types, lets fetch them.
        cache_seq_num = self._state_group_cache.sequence

        group_state_dict = yield self._get_state_groups_from_groups(
            missing_groups_and_types
        )

        state_events = yield self._get_events(
            [e_id for l in group_state_dict.values() for e_id in l],
            get_prev_content=False
        )

        state_events = {
            e.event_id: e
            for e in state_events
        }

        for group, state_ids in group_state_dict.items():
            state_dict = {
                key: None
                for key in missing_types
            }
            evs = [
                state_events[e_id] for e_id in state_ids
                if e_id in state_events  # This can happen if event is rejected.
            ]
            state_dict.update({
                (e.type, e.state_key): e
                for e in evs
            })

            # Update the cache
            self._state_group_cache.update(
                cache_seq_num,
                key=group,
                value=state_dict,
                full=(types is None),
            )

            results[group] = {
                key: value
                for key, value in state_dict.items()
                if value
            }

        defer.returnValue(results)


def _make_group_id(clock):
    return str(int(clock.time_msec())) + random_string(5)