feat(appservice): mosaic-as daemon host + container (M4a) (#531)

apps/appservice/src/server.ts

@@ -0,0 +1,124 @@
+import { createHmac, randomBytes, timingSafeEqual } from 'node:crypto';
+
+import {
+  AppserviceIntent,
+  TransactionHandler,
+  validateBridgeMessage,
+  validateBridgeTyping,
+} from '@mosaicstack/appservice';
+import type { AppserviceConfig, MatrixEvent } from '@mosaicstack/appservice';
+
+export interface DaemonConfig extends AppserviceConfig {
+  /** Bearer tokens accepted on /bridge/v1/* (one per agent-comms host daemon). */
+  bridgeTokens: string[];
+}
+
+export interface DaemonRequest {
+  method: string;
+  /** URL path without query string. */
+  path: string;
+  searchParams: URLSearchParams;
+  authorizationHeader?: string;
+  body: unknown;
+}
+
+export interface DaemonResponse {
+  status: number;
+  body: Record<string, unknown>;
+}
+
+// Compare equal-length HMAC digests so neither content nor LENGTH of the
+// stored secret is observable through timing.
+const HMAC_KEY = randomBytes(32);
+const digest = (value: string): Buffer => createHmac('sha256', HMAC_KEY).update(value).digest();
+
+const safeEqual = (a: string, b: string): boolean => timingSafeEqual(digest(a), digest(b));
+
+const TXN_PATH = /^\/_matrix\/app\/v1\/transactions\/([^/]+)$/;
+
+/**
+ * HTTP-framework-agnostic request router for the mosaic-as daemon: the
+ * Application Service transactions endpoint (Synapse-facing) plus the
+ * internal bridge API v1 (agent-comms daemon-facing). main.ts binds this to
+ * node:http; tests drive it directly.
+ */
+export class AppserviceDaemon {
+  readonly intent: AppserviceIntent;
+  private readonly transactions: TransactionHandler;
+
+  constructor(
+    private readonly cfg: DaemonConfig,
+    fetchImpl?: typeof fetch,
+    private readonly log: (line: string) => void = (line) => console.log(line),
+  ) {
+    this.intent = new AppserviceIntent(cfg, fetchImpl);
+    this.transactions = new TransactionHandler({
+      hsToken: cfg.hsToken,
+      onEvent: (event) => this.onEvent(event),
+      onError: (error, txnId) => this.log(`txn ${txnId} handler error: ${String(error)}`),
+    });
+  }
+
+  /** v1: the daemon only observes; room logic lives in the agent-comms daemons. */
+  private onEvent(event: MatrixEvent): void {
+    if (event.type === 'm.room.message') {
+      this.log(
+        `event ${event.event_id ?? '?'} in ${event.room_id ?? '?'} from ${event.sender ?? '?'}`,
+      );
+    }
+  }
+
+  private bridgeAuthorized(authorizationHeader: string | undefined): boolean {
+    if (!authorizationHeader?.startsWith('Bearer ')) return false;
+    const presented = authorizationHeader.slice('Bearer '.length);
+    return this.cfg.bridgeTokens.some((token) => safeEqual(presented, token));
+  }
+
+  async handle(req: DaemonRequest): Promise<DaemonResponse> {
+    if (req.method === 'GET' && req.path === '/health') {
+      return { status: 200, body: { ok: true } };
+    }
+
+    const txnMatch = req.method === 'PUT' ? TXN_PATH.exec(req.path) : null;
+    if (txnMatch?.[1] !== undefined) {
+      return this.transactions.handle(txnMatch[1], req.body, {
+        authorizationHeader: req.authorizationHeader,
+        accessTokenParam: req.searchParams.get('access_token') ?? undefined,
+      });
+    }
+
+    if (req.path.startsWith('/bridge/v1/')) {
+      if (!this.bridgeAuthorized(req.authorizationHeader)) {
+        return { status: 403, body: { errcode: 'M_FORBIDDEN', error: 'bad bridge token' } };
+      }
+      try {
+        if (req.method === 'POST' && req.path === '/bridge/v1/messages') {
+          validateBridgeMessage(req.body);
+          const eventId = await this.intent.sendAsAgent({
+            roomId: req.body.room_id,
+            agent: req.body.agent,
+            body: req.body.body,
+            threadRoot: req.body.thread_root,
+            msgtype: req.body.msgtype,
+            extraContent: req.body.extra_content,
+          });
+          return { status: 200, body: { event_id: eventId ?? null } };
+        }
+        if (req.method === 'POST' && req.path === '/bridge/v1/typing') {
+          validateBridgeTyping(req.body);
+          await this.intent.setTyping(req.body.room_id, req.body.agent, req.body.typing);
+          return { status: 200, body: {} };
+        }
+      } catch (error) {
+        const message = error instanceof Error ? error.message : String(error);
+        this.log(`bridge error ${req.method} ${req.path}: ${message}`);
+        return { status: 400, body: { error: message } };
+      }
+      // Explicit: never fall out of the authenticated bridge block, so future
+      // sub-paths cannot accidentally route around the auth guard above.
+      return { status: 405, body: { error: 'unsupported bridge method/path' } };
+    }
+
+    return { status: 404, body: { error: 'not found' } };
+  }
+}