Element-R: add a listener for room membership events

we need to track the devices of users that join the room after us.

Author: richvdh

src/client.ts

@@ -2183,7 +2183,11 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         // importing rust-crypto will download the webassembly, so we delay it until we know it will be
         // needed.
         const RustCrypto = await import("./rust-crypto");
-        this.cryptoBackend = await RustCrypto.initRustCrypto(this.http, userId, deviceId);
+        const rustCrypto = await RustCrypto.initRustCrypto(this.http, userId, deviceId);
+        this.cryptoBackend = rustCrypto;
+
+        // attach the event listeners needed by RustCrypto
+        this.on(RoomMemberEvent.Membership, rustCrypto.onRoomMembership.bind(rustCrypto));
     }
 
     /**

src/rust-crypto/RoomEncryptor.ts

@@ -20,6 +20,7 @@ import { IContent, MatrixEvent } from "../models/event";
 import { Room } from "../models/room";
 import { logger, PrefixedLogger } from "../logger";
 import { KeyClaimManager } from "./KeyClaimManager";
+import { RoomMember } from "../models/room-member";
 
 /**
  * RoomEncryptor: responsible for encrypting messages to a given room
@@ -53,6 +54,26 @@ export class RoomEncryptor {
         }
     }
 
+    /**
+     * Handle a new `m.room.member` event in this room
+     *
+     * @param member - new membership state
+     */
+    public onRoomMembership(member: RoomMember): void {
+        this.prefixedLogger.debug(`${member.membership} event for ${member.userId}`);
+
+        if (
+            member.membership == "join" ||
+            (member.membership == "invite" && this.room.shouldEncryptForInvitedMembers())
+        ) {
+            // make sure we are tracking the deviceList for this user
+            this.prefixedLogger.debug(`starting to track devices for: ${member.userId}`);
+            this.olmMachine.updateTrackedUsers([new UserId(member.userId)]);
+        }
+
+        // TODO: handle leaves (including our own)
+    }
+
     /**
      * Prepare to encrypt events in this room.
      *

src/rust-crypto/index.ts

@@ -18,15 +18,14 @@ import * as RustSdkCryptoJs from "@matrix-org/matrix-sdk-crypto-js";
 
 import { RustCrypto } from "./rust-crypto";
 import { logger } from "../logger";
-import { CryptoBackend } from "../common-crypto/CryptoBackend";
 import { RUST_SDK_STORE_PREFIX } from "./constants";
 import { IHttpOpts, MatrixHttpApi } from "../http-api";
 
 export async function initRustCrypto(
     http: MatrixHttpApi<IHttpOpts & { onlyData: true }>,
     userId: string,
     deviceId: string,
-): Promise<CryptoBackend> {
+): Promise<RustCrypto> {
     // initialise the rust matrix-sdk-crypto-js, if it hasn't already been done
     await RustSdkCryptoJs.initAsync();
 

src/rust-crypto/rust-crypto.ts

@@ -21,6 +21,7 @@ import type { IToDeviceEvent } from "../sync-accumulator";
 import type { IEncryptedEventInfo } from "../crypto/api";
 import { MatrixEvent } from "../models/event";
 import { Room } from "../models/room";
+import { RoomMember } from "../models/room-member";
 import { CryptoBackend, OnSyncCompletedData } from "../common-crypto/CryptoBackend";
 import { logger } from "../logger";
 import { IHttpOpts, MatrixHttpApi } from "../http-api";
@@ -227,6 +228,27 @@ export class RustCrypto implements CryptoBackend {
         this.outgoingRequestLoop();
     }
 
+    ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+    //
+    // Other public functions
+    //
+    ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+    /** called by the MatrixClient on a room membership event
+     *
+     * @param event - The matrix event which caused this event to fire.
+     * @param member - The member whose RoomMember.membership changed.
+     * @param oldMembership - The previous membership state. Null if it's a new member.
+     */
+    public onRoomMembership(event: MatrixEvent, member: RoomMember, oldMembership?: string): void {
+        const enc = this.roomEncryptors[event.getRoomId()!];
+        if (!enc) {
+            // not encrypting in this room
+            return;
+        }
+        enc.onRoomMembership(member);
+    }
+
     ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////
     //
     // Outgoing requests