text: # 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 typing import Optional, Tuple
  
  import attr
  
  from synapse.api.constants import RelationTypes
  from synapse.events import EventBase
  from synapse.storage._base import SQLBaseStore
  from synapse.storage.databases.main.stream import generate_pagination_where_clause
  from synapse.storage.relations import (
      AggregationPaginationToken,
      PaginationChunk,
      RelationPaginationToken,
  )
  from synapse.util.caches.descriptors import cached
  
  logger = logging.getLogger(__name__)
  
  
  class RelationsWorkerStore(SQLBaseStore):
      @cached(tree=True)
      async def get_relations_for_event(
          self,
          event_id: str,
          relation_type: Optional[str] = None,
          event_type: Optional[str] = None,
          aggregation_key: Optional[str] = None,
          limit: int = 5,
          direction: str = "b",
          from_token: Optional[RelationPaginationToken] = None,
          to_token: Optional[RelationPaginationToken] = None,
      ) -> PaginationChunk:
          """Get a list of relations for an event, ordered by topological ordering.
  
          Args:
              event_id: Fetch events that relate to this event ID.
              relation_type: Only fetch events with this relation type, if given.
              event_type: Only fetch events with this event type, if given.
              aggregation_key: Only fetch events with this aggregation key, if given.
              limit: Only fetch the most recent `limit` events.
              direction: Whether to fetch the most recent first (`"b"`) or the
                  oldest first (`"f"`).
              from_token: Fetch rows from the given token, or from the start if None.
              to_token: Fetch rows up to the given token, or up to the end if None.
  
          Returns:
              List of event IDs that match relations requested. The rows are of
              the form `{"event_id": "..."}`.
          """
  
          where_clause = ["relates_to_id = ?"]
          where_args = [event_id]
  
          if relation_type is not None:
              where_clause.append("relation_type = ?")
              where_args.append(relation_type)
  
          if event_type is not None:
              where_clause.append("type = ?")
              where_args.append(event_type)
  
          if aggregation_key:
              where_clause.append("aggregation_key = ?")
              where_args.append(aggregation_key)
  
          pagination_clause = generate_pagination_where_clause(
              direction=direction,
              column_names=("topological_ordering", "stream_ordering"),
              from_token=attr.astuple(from_token) if from_token else None,
              to_token=attr.astuple(to_token) if to_token else None,
              engine=self.database_engine,
          )
  
          if pagination_clause:
              where_clause.append(pagination_clause)
  
          if direction == "b":
              order = "DESC"
          else:
              order = "ASC"
  
          sql = """
              SELECT event_id, topological_ordering, stream_ordering
              FROM event_relations
              INNER JOIN events USING (event_id)
              WHERE %s
              ORDER BY topological_ordering %s, stream_ordering %s
              LIMIT ?
          """ % (
              " AND ".join(where_clause),
              order,
              order,
          )
  
          def _get_recent_references_for_event_txn(txn):
              txn.execute(sql, where_args + [limit + 1])
  
              last_topo_id = None
              last_stream_id = None
              events = []
              for row in txn:
                  events.append({"event_id": row[0]})
                  last_topo_id = row[1]
                  last_stream_id = row[2]
  
              next_batch = None
              if len(events) > limit and last_topo_id and last_stream_id:
                  next_batch = RelationPaginationToken(last_topo_id, last_stream_id)
  
              return PaginationChunk(
                  chunk=list(events[:limit]), next_batch=next_batch, prev_batch=from_token
              )
  
          return await self.db_pool.runInteraction(
              "get_recent_references_for_event", _get_recent_references_for_event_txn
          )
  
      @cached(tree=True)
      async def get_aggregation_groups_for_event(
          self,
          event_id: str,
          event_type: Optional[str] = None,
          limit: int = 5,
          direction: str = "b",
          from_token: Optional[AggregationPaginationToken] = None,
          to_token: Optional[AggregationPaginationToken] = None,
      ) -> PaginationChunk:
          """Get a list of annotations on the event, grouped by event type and
          aggregation key, sorted by count.
  
          This is used e.g. to get the what and how many reactions have happend
          on an event.
  
          Args:
              event_id: Fetch events that relate to this event ID.
              event_type: Only fetch events with this event type, if given.
              limit: Only fetch the `limit` groups.
              direction: Whether to fetch the highest count first (`"b"`) or
                  the lowest count first (`"f"`).
              from_token: Fetch rows from the given token, or from the start if None.
              to_token: Fetch rows up to the given token, or up to the end if None.
  
          Returns:
              List of groups of annotations that match. Each row is a dict with
              `type`, `key` and `count` fields.
          """
  
          where_clause = ["relates_to_id = ?", "relation_type = ?"]
          where_args = [event_id, RelationTypes.ANNOTATION]
  
          if event_type:
              where_clause.append("type = ?")
              where_args.append(event_type)
  
          having_clause = generate_pagination_where_clause(
              direction=direction,
              column_names=("COUNT(*)", "MAX(stream_ordering)"),
              from_token=attr.astuple(from_token) if from_token else None,
              to_token=attr.astuple(to_token) if to_token else None,
              engine=self.database_engine,
          )
  
          if direction == "b":
              order = "DESC"
          else:
              order = "ASC"
  
          if having_clause:
              having_clause = "HAVING " + having_clause
          else:
              having_clause = ""
  
          sql = """
              SELECT type, aggregation_key, COUNT(DISTINCT sender), MAX(stream_ordering)
              FROM event_relations
              INNER JOIN events USING (event_id)
              WHERE {where_clause}
              GROUP BY relation_type, type, aggregation_key
              {having_clause}
              ORDER BY COUNT(*) {order}, MAX(stream_ordering) {order}
              LIMIT ?
          """.format(
              where_clause=" AND ".join(where_clause),
              order=order,
              having_clause=having_clause,
          )
  
          def _get_aggregation_groups_for_event_txn(txn):
              txn.execute(sql, where_args + [limit + 1])
  
              next_batch = None
              events = []
              for row in txn:
                  events.append({"type": row[0], "key": row[1], "count": row[2]})
                  next_batch = AggregationPaginationToken(row[2], row[3])
  
              if len(events) <= limit:
                  next_batch = None
  
              return PaginationChunk(
                  chunk=list(events[:limit]), next_batch=next_batch, prev_batch=from_token
              )
  
          return await self.db_pool.runInteraction(
              "get_aggregation_groups_for_event", _get_aggregation_groups_for_event_txn
          )
  
      @cached()
      async def get_applicable_edit(self, event_id: str) -> Optional[EventBase]:
          """Get the most recent edit (if any) that has happened for the given
          event.
  
          Correctly handles checking whether edits were allowed to happen.
  
          Args:
              event_id: The original event ID
  
          Returns:
              The most recent edit, if any.
          """
  
          # We only allow edits for `m.room.message` events that have the same sender
          # and event type. We can't assert these things during regular event auth so
          # we have to do the checks post hoc.
  
          # Fetches latest edit that has the same type and sender as the
          # original, and is an `m.room.message`.
          sql = """
              SELECT edit.event_id FROM events AS edit
              INNER JOIN event_relations USING (event_id)
              INNER JOIN events AS original ON
                  original.event_id = relates_to_id
                  AND edit.type = original.type
                  AND edit.sender = original.sender
              WHERE
                  relates_to_id = ?
                  AND relation_type = ?
                  AND edit.type = 'm.room.message'
              ORDER by edit.origin_server_ts DESC, edit.event_id DESC
              LIMIT 1
          """
  
          def _get_applicable_edit_txn(txn):
              txn.execute(sql, (event_id, RelationTypes.REPLACE))
              row = txn.fetchone()
              if row:
                  return row[0]
  
          edit_id = await self.db_pool.runInteraction(
              "get_applicable_edit", _get_applicable_edit_txn
          )
  
          if not edit_id:
              return None
  
          return await self.get_event(edit_id, allow_none=True)
  
      @cached()
      async def get_thread_summary(
          self, event_id: str
      ) -> Tuple[int, Optional[EventBase]]:
          """Get the number of threaded replies, the senders of those replies, and
          the latest reply (if any) for the given event.
  
          Args:
              event_id: The original event ID
  
          Returns:
              The number of items in the thread and the most recent response, if any.
          """
  
          def _get_thread_summary_txn(txn) -> Tuple[int, Optional[str]]:
              # Fetch the count of threaded events and the latest event ID.
              # TODO Should this only allow m.room.message events.
              sql = """
                  SELECT event_id
                  FROM event_relations
                  INNER JOIN events USING (event_id)
                  WHERE
                      relates_to_id = ?
                      AND relation_type = ?
                  ORDER BY topological_ordering DESC, stream_ordering DESC
                  LIMIT 1
              """
  
              txn.execute(sql, (event_id, RelationTypes.THREAD))
              row = txn.fetchone()
              if row is None:
                  return 0, None
  
              latest_event_id = row[0]
  
              sql = """
                  SELECT COALESCE(COUNT(event_id), 0)
                  FROM event_relations
                  WHERE
                      relates_to_id = ?
                      AND relation_type = ?
              """
              txn.execute(sql, (event_id, RelationTypes.THREAD))
              count = txn.fetchone()[0]
  
              return count, latest_event_id
  
          count, latest_event_id = await self.db_pool.runInteraction(
              "get_thread_summary", _get_thread_summary_txn
          )
  
          latest_event = None
          if latest_event_id:
              latest_event = await self.get_event(latest_event_id, allow_none=True)
  
          return count, latest_event
  
      async def has_user_annotated_event(
          self, parent_id: str, event_type: str, aggregation_key: str, sender: str
      ) -> bool:
          """Check if a user has already annotated an event with the same key
          (e.g. already liked an event).
  
          Args:
              parent_id: The event being annotated
              event_type: The event type of the annotation
              aggregation_key: The aggregation key of the annotation
              sender: The sender of the annotation
  
          Returns:
              True if the event is already annotated.
          """
  
          sql = """
              SELECT 1 FROM event_relations
              INNER JOIN events USING (event_id)
              WHERE
                  relates_to_id = ?
                  AND relation_type = ?
                  AND type = ?
                  AND sender = ?
                  AND aggregation_key = ?
              LIMIT 1;
          """
  
          def _get_if_user_has_annotated_event(txn):
              txn.execute(
                  sql,
                  (
                      parent_id,
                      RelationTypes.ANNOTATION,
                      event_type,
                      sender,
                      aggregation_key,
                  ),
              )
  
              return bool(txn.fetchone())
  
          return await self.db_pool.runInteraction(
              "get_if_user_has_annotated_event", _get_if_user_has_annotated_event
          )
  
  
  class RelationsStore(RelationsWorkerStore):
      pass
  