feat: implement remote homeserver handling for LiveKit calls

src/app/features/call/useRtcConfig.ts

@@ -1,6 +1,59 @@
 import { useCallback } from 'react';
+import { Room } from 'matrix-js-sdk';
 import { useMatrixClient } from '../../hooks/useMatrixClient';
 import { LiveKitFocus, LiveKitJWTResponse, OpenIdToken, WellKnownWithRTC } from './types';
+import { getMxIdServer } from '../../utils/matrix';
+import { guessDmRoomUserId } from '../../utils/matrix';
+
+/**
+ * Get room server from room ID (format: !roomid:server.com)
+ */
+function getRoomServer(roomId: string): string | undefined {
+  return getMxIdServer(roomId);
+}
+
+/**
+ * Determine which homeservers to try for LiveKit JWT, in priority order
+ * @param room - Room to start call in
+ * @param userHomeserver - User's homeserver
+ * @param myUserId - Current user's Matrix ID
+ * @returns Array of homeserver base URLs to try in order
+ */
+export function getLiveKitHomeserverPriority(
+  room: Room,
+  userHomeserver: string,
+  myUserId: string
+): string[] {
+  const servers: string[] = [];
+  const memberCount = room.getMembers().length;
+  const isDM = memberCount <= 2;
+
+  if (isDM) {
+    // For DMs: user's homeserver first, then other member's homeserver
+    servers.push(userHomeserver);
+    
+    const otherUserId = guessDmRoomUserId(room, myUserId);
+    if (otherUserId && otherUserId !== myUserId) {
+      const otherServer = getMxIdServer(otherUserId);
+      if (otherServer && otherServer !== userHomeserver) {
+        servers.push(`https://${otherServer}`);
+      }
+    }
+  } else {
+    // For channels: room's homeserver first, then user's homeserver
+    const roomServer = getRoomServer(room.roomId);
+    if (roomServer) {
+      servers.push(`https://${roomServer}`);
+    }
+    
+    // Fallback to user's homeserver if different
+    if (!roomServer || roomServer !== userHomeserver.replace('https://', '').replace('http://', '')) {
+      servers.push(userHomeserver);
+    }
+  }
+
+  return servers;
+}
 
 /**
  * Fetches the LiveKit focus configuration from well-known data
@@ -113,6 +166,59 @@ export async function fetchLiveKitJWT(
   return response.json();
 }
 
+/**
+ * Try fetching LiveKit JWT from multiple homeservers in priority order
+ * @param homeservers - Array of homeserver base URLs to try
+ * @param roomId - The Matrix room ID
+ * @param userId - The Matrix user ID
+ * @param deviceId - The Matrix device ID
+ * @param accessToken - The Matrix access token
+ * @returns LiveKit JWT response and the homeserver that provided it, or null
+ */
+export async function fetchLiveKitJWTFromServers(
+  homeservers: string[],
+  roomId: string,
+  userId: string,
+  deviceId: string,
+  accessToken: string
+): Promise<{ jwt: LiveKitJWTResponse; homeserver: string } | null> {
+  for (const homeserver of homeservers) {
+    try {
+      console.log(`Trying LiveKit JWT from homeserver: ${homeserver}`);
+      
+      // Fetch well-known from this homeserver
+      const wellKnown = await fetchWellKnownWithRTC(homeserver);
+      const livekitFocus = getLiveKitFocus(wellKnown);
+      
+      if (!livekitFocus) {
+        console.log(`No LiveKit config on ${homeserver}, trying next...`);
+        continue;
+      }
+      
+      // Get OpenID token from this homeserver
+      const openIdToken = await requestOpenIdToken(homeserver, userId, accessToken);
+      
+      // Exchange for LiveKit JWT
+      const jwt = await fetchLiveKitJWT(
+        livekitFocus.livekit_service_url,
+        roomId,
+        userId,
+        deviceId,
+        openIdToken
+      );
+      
+      console.log(`Successfully got LiveKit JWT from ${homeserver}`);
+      return { jwt, homeserver };
+    } catch (error) {
+      console.warn(`Failed to get LiveKit JWT from ${homeserver}:`, error);
+      // Continue to next homeserver
+    }
+  }
+  
+  console.error('Failed to get LiveKit JWT from any homeserver');
+  return null;
+}
+
 /**
  * Hook to get RTC configuration functions
  * Provides utilities for fetching well-known data and LiveKit JWTs