pull out all screen share related logic.

src/state/CallViewModel/localMember/LocalTransport.ts

@@ -0,0 +1,169 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-IdFentifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import {
+  type CallMembership,
+  isLivekitTransport,
+  type LivekitTransportConfig,
+  type LivekitTransport,
+  isLivekitTransportConfig,
+} from "matrix-js-sdk/lib/matrixrtc";
+import { type MatrixClient } from "matrix-js-sdk";
+import { combineLatest, distinctUntilChanged, first, from } from "rxjs";
+import { logger } from "matrix-js-sdk/lib/logger";
+import { AutoDiscovery } from "matrix-js-sdk/lib/autodiscovery";
+import { deepCompare } from "matrix-js-sdk/lib/utils";
+
+import { type Behavior } from "../../Behavior.ts";
+import {
+  type Epoch,
+  mapEpoch,
+  type ObservableScope,
+} from "../../ObservableScope.ts";
+import { Config } from "../../../config/Config.ts";
+import { MatrixRTCTransportMissingError } from "../../../utils/errors.ts";
+import { getSFUConfigWithOpenID } from "../../../livekit/openIDSFU.ts";
+
+/*
+ * - get well known
+ * - get oldest membership
+ * - get transport to use
+ * - get openId + jwt token
+ * - wait for createTrack() call
+ *    - create tracks
+ * - wait for join() call
+ *   - Publisher.publishTracks()
+ *   - send join state/sticky event
+ */
+interface Props {
+  scope: ObservableScope;
+  memberships$: Behavior<Epoch<CallMembership[]>>;
+  client: MatrixClient;
+  roomId: string;
+  useOldestMember$: Behavior<boolean>;
+}
+
+/**
+ * This class is responsible for managing the local transport.
+ * "Which transport is the local member going to use"
+ *
+ * @prop useOldestMember Whether to use the same transport as the oldest member.
+ * This will only update once the first oldest member appears. Will not recompute if the oldest member leaves.
+ */
+export const createLocalTransport$ = ({
+  scope,
+  memberships$,
+  client,
+  roomId,
+  useOldestMember$,
+}: Props): Behavior<LivekitTransport | undefined> => {
+  /**
+   * The transport over which we should be actively publishing our media.
+   * undefined when not joined.
+   */
+  const oldestMemberTransport$ = scope.behavior(
+    memberships$.pipe(
+      mapEpoch((memberships) => memberships[0].getTransport(memberships[0])),
+      first((t) => t != undefined && isLivekitTransport(t)),
+    ),
+    undefined,
+  );
+
+  /**
+   * The transport that we would personally prefer to publish on (if not for the
+   * transport preferences of others, perhaps).
+   */
+  const preferredTransport$: Behavior<LivekitTransport | undefined> =
+    scope.behavior(from(makeTransport(client, roomId)), undefined);
+
+  /**
+   * The transport we should advertise in our MatrixRTC membership.
+   */
+  const advertisedTransport$ = scope.behavior(
+    combineLatest(
+      [useOldestMember$, oldestMemberTransport$, preferredTransport$],
+      (useOldestMember, oldestMemberTransport, preferredTransport) =>
+        useOldestMember ? oldestMemberTransport : preferredTransport,
+    ).pipe<LivekitTransport>(distinctUntilChanged(deepCompare)),
+    undefined,
+  );
+  return advertisedTransport$;
+};
+
+const FOCI_WK_KEY = "org.matrix.msc4143.rtc_foci";
+
+async function makeTransportInternal(
+  client: MatrixClient,
+  roomId: string,
+): Promise<LivekitTransport> {
+  logger.log("Searching for a preferred transport");
+  //TODO refactor this to use the jwt service returned alias.
+  const livekitAlias = roomId;
+
+  // TODO-MULTI-SFU: Either remove this dev tool or make it more official
+  const urlFromStorage =
+    localStorage.getItem("robin-matrixrtc-auth") ??
+    localStorage.getItem("timo-focus-url");
+  if (urlFromStorage !== null) {
+    const transportFromStorage: LivekitTransport = {
+      type: "livekit",
+      livekit_service_url: urlFromStorage,
+      livekit_alias: livekitAlias,
+    };
+    logger.log(
+      "Using LiveKit transport from local storage: ",
+      transportFromStorage,
+    );
+    return transportFromStorage;
+  }
+
+  // Prioritize the .well-known/matrix/client, if available, over the configured SFU
+  const domain = client.getDomain();
+  if (domain) {
+    // we use AutoDiscovery instead of relying on the MatrixClient having already
+    // been fully configured and started
+    const wellKnownFoci = (await AutoDiscovery.getRawClientConfig(domain))?.[
+      FOCI_WK_KEY
+    ];
+    if (Array.isArray(wellKnownFoci)) {
+      const transport: LivekitTransportConfig | undefined = wellKnownFoci.find(
+        (f) => f && isLivekitTransportConfig(f),
+      );
+      if (transport !== undefined) {
+        logger.log("Using LiveKit transport from .well-known: ", transport);
+        return { ...transport, livekit_alias: livekitAlias };
+      }
+    }
+  }
+
+  const urlFromConf = Config.get().livekit?.livekit_service_url;
+  if (urlFromConf) {
+    const transportFromConf: LivekitTransport = {
+      type: "livekit",
+      livekit_service_url: urlFromConf,
+      livekit_alias: livekitAlias,
+    };
+    logger.log("Using LiveKit transport from config: ", transportFromConf);
+    return transportFromConf;
+  }
+
+  throw new MatrixRTCTransportMissingError(domain ?? "");
+}
+
+async function makeTransport(
+  client: MatrixClient,
+  roomId: string,
+): Promise<LivekitTransport> {
+  const transport = await makeTransportInternal(client, roomId);
+  // this will call the jwt/sfu/get endpoint to pre create the livekit room.
+  await getSFUConfigWithOpenID(
+    client,
+    transport.livekit_service_url,
+    transport.livekit_alias,
+  );
+  return transport;
+}