Add a new component: currentstateserver (#1171)

* Add a new component: currentstateserver

- Add a skeleton for it, with databases and a single query method.
- Add integration tests for it.
- Add listen/address fields in the config (breaking as this will force people to specify this to validate)

Not currently hooked up to anything yet.

* Unbreak config tests

* Add current_state to sample config

* comments

currentstateserver/storage/shared/storage.go

@@ -0,0 +1,65 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// 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.
+
+package shared
+
+import (
+	"context"
+	"database/sql"
+
+	"github.com/matrix-org/dendrite/currentstateserver/storage/tables"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+type Database struct {
+	DB               *sql.DB
+	CurrentRoomState tables.CurrentRoomState
+}
+
+func (d *Database) GetStateEvent(ctx context.Context, roomID, evType, stateKey string) (*gomatrixserverlib.HeaderedEvent, error) {
+	return d.CurrentRoomState.SelectStateEvent(ctx, roomID, evType, stateKey)
+}
+
+func (d *Database) StoreStateEvents(ctx context.Context, addStateEvents []gomatrixserverlib.HeaderedEvent,
+	removeStateEventIDs []string) error {
+	return sqlutil.WithTransaction(d.DB, func(txn *sql.Tx) error {
+		// remove first, then add, as we do not ever delete state, but do replace state which is a remove followed by an add.
+		for _, eventID := range removeStateEventIDs {
+			if err := d.CurrentRoomState.DeleteRoomStateByEventID(ctx, txn, eventID); err != nil {
+				return err
+			}
+		}
+
+		for _, event := range addStateEvents {
+			if event.StateKey() == nil {
+				// ignore non state events
+				continue
+			}
+			var membership *string
+			if event.Type() == "m.room.member" {
+				value, err := event.Membership()
+				if err != nil {
+					return err
+				}
+				membership = &value
+			}
+
+			if err := d.CurrentRoomState.UpsertRoomState(ctx, txn, event, membership); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}