feat(voice): harden Gemini Live provider integration

server/providers/gemini/realtime.js

@@ -0,0 +1,180 @@
+import { clientKey, makeCostRateLimiter } from '../common/rate-limit.js';
+import { readResponseJsonCapped } from '../../../src/sources/httpBody.js';
+import {
+  GEMINI_TOKEN_ENDPOINT,
+  GEMINI_LIVE_WEBSOCKET_URL,
+  GEMINI_LIVE_MODEL_DEFAULT,
+  createGeminiLiveConfig,
+  normalizeGeminiModel,
+} from './config.js';
+import {
+  isGeminiRequestOriginAllowed,
+  readGeminiTokenRequest,
+} from './request.js';
+
+const UPSTREAM_RESPONSE_BYTES = 32 * 1024;
+const MINT_FAILURE = 'Gemini voice could not connect. Try again.';
+
+export function createGeminiTokenHandler({
+  annotationGuidance,
+  providerDropdown = false,
+  tools,
+  fetchImpl = (...args) => fetch(...args),
+  resolveApiKey = () => process.env.GEMINI_API_KEY,
+  resolveModel = () =>
+    process.env.GEMINI_LIVE_MODEL || GEMINI_LIVE_MODEL_DEFAULT,
+  resolveHost = () => process.env.HOST,
+  resolveAllowedHosts = () => process.env.GEV_ALLOWED_HOSTS,
+  resolveRateLimit = () => process.env.GEV_RATELIMIT_GEMINI_PER_MIN ?? '30',
+  now = Date.now,
+  timeoutMs = 15_000,
+} = {}) {
+  let limiter;
+  return async (req, res) => {
+    res.setHeader('Cache-Control', 'no-store');
+    res.setHeader('Content-Type', 'application/json; charset=utf-8');
+    res.setHeader('X-Content-Type-Options', 'nosniff');
+    const reply = (status, errorOrPayload) => {
+      if (res.destroyed || res.writableEnded) return;
+      res.statusCode = status;
+      if (status >= 400) res.setHeader('Connection', 'close');
+      res.end(
+        JSON.stringify(
+          typeof errorOrPayload === 'string'
+            ? { error: errorOrPayload }
+            : errorOrPayload,
+        ),
+      );
+    };
+    if (req.method !== 'POST') {
+      res.setHeader('Allow', 'POST');
+      return reply(405, 'Method not allowed');
+    }
+    if (
+      !isGeminiRequestOriginAllowed(req, resolveHost(), resolveAllowedHosts())
+    )
+      return reply(403, 'Gemini voice requires a same-origin app request');
+    const apiKey = String(resolveApiKey() || '').trim();
+    if (!apiKey) return reply(503, 'Add a Gemini API key in Provider Settings');
+    const model = normalizeGeminiModel(resolveModel());
+    if (!model)
+      return reply(503, 'The Gemini Live model configuration is invalid');
+    if (limiter === undefined)
+      limiter = makeCostRateLimiter(resolveRateLimit(), 30);
+    if (limiter && !limiter(clientKey(req))) {
+      res.setHeader('Retry-After', '60');
+      return reply(
+        429,
+        'Gemini voice is starting too often. Try again shortly.',
+      );
+    }
+
+    const lifetime = new AbortController();
+    let disconnected = false;
+    const disconnect = () => {
+      disconnected = true;
+      lifetime.abort(new DOMException('Request closed', 'AbortError'));
+    };
+    const responseClosed = () => {
+      if (!res.writableEnded) disconnect();
+    };
+    req.once('aborted', disconnect);
+    res.once('close', responseClosed);
+    const deadline = setTimeout(() => {
+      lifetime.abort(
+        new DOMException('Token request timed out', 'TimeoutError'),
+      );
+    }, timeoutMs);
+    deadline.unref?.();
+    try {
+      const inputMode = await readGeminiTokenRequest(req, lifetime.signal);
+      lifetime.signal.throwIfAborted();
+      const config = createGeminiLiveConfig(
+        annotationGuidance,
+        inputMode,
+        tools,
+        { providerDropdown },
+      );
+      const issuedAt = now();
+      // REST uses bidiGenerateContentSetup. liveConnectConstraints is the SDK
+      // input shape, converted before transport. With no fieldMask the complete
+      // setup is locked to this server-owned configuration.
+      const request = {
+        uses: 1,
+        expireTime: new Date(issuedAt + 30 * 60_000).toISOString(),
+        newSessionExpireTime: new Date(issuedAt + 60_000).toISOString(),
+        bidiGenerateContentSetup: { model: `models/${model}`, ...config },
+      };
+      const response = await fetchImpl(GEMINI_TOKEN_ENDPOINT, {
+        method: 'POST',
+        redirect: 'error',
+        signal: lifetime.signal,
+        headers: {
+          'x-goog-api-key': apiKey,
+          'Content-Type': 'application/json',
+        },
+        body: JSON.stringify(request),
+      });
+      lifetime.signal.throwIfAborted();
+      if (
+        response.redirected ||
+        (response.url && response.url !== GEMINI_TOKEN_ENDPOINT)
+      )
+        throw new Error('Unexpected token response destination');
+      if (!response.ok) {
+        // Never forward upstream bodies, headers or exception messages.
+        void response.body?.cancel().catch(() => {});
+        if (response.status === 429) {
+          res.setHeader('Retry-After', '60');
+          return reply(429, 'Gemini quota is unavailable. Try again later.');
+        }
+        if (response.status === 401 || response.status === 403)
+          return reply(
+            503,
+            'Gemini access was refused. Check the API key and model access.',
+          );
+        if (response.status === 400 || response.status === 404)
+          return reply(
+            502,
+            'Gemini Live is unavailable for the configured model.',
+          );
+        return reply(502, MINT_FAILURE);
+      }
+      const data = await readResponseJsonCapped(
+        response,
+        UPSTREAM_RESPONSE_BYTES,
+        lifetime.signal,
+      );
+      lifetime.signal.throwIfAborted();
+      if (
+        !data ||
+        Array.isArray(data) ||
+        typeof data !== 'object' ||
+        typeof data.name !== 'string' ||
+        data.name.length > 8192 ||
+        !/^auth_tokens\/[A-Za-z0-9._~+/=-]+$/.test(data.name) ||
+        data.name.includes(apiKey)
+      )
+        throw new Error('Invalid ephemeral token');
+      reply(200, {
+        token: data.name,
+        model,
+        config,
+        websocketUrl: GEMINI_LIVE_WEBSOCKET_URL,
+      });
+    } catch (error) {
+      if (disconnected || req.aborted) return;
+      if (error?.code === 'BODY_TOO_LARGE')
+        return reply(413, 'Token request is too large');
+      if (error?.code === 'BAD_CONTENT_TYPE')
+        return reply(415, 'Use an empty JSON token request');
+      if (error?.code === 'BAD_BODY')
+        return reply(400, 'Use an empty JSON token request');
+      reply(lifetime.signal.aborted ? 504 : 502, MINT_FAILURE);
+    } finally {
+      clearTimeout(deadline);
+      req.off('aborted', disconnect);
+      res.off('close', responseClosed);
+    }
+  };
+}