106 lines
3.0 KiB
JavaScript
106 lines
3.0 KiB
JavaScript
const express = require('express');
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const path = require('path');
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const { GoogleAuth } = require('google-auth-library');
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const app = express();
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const port = process.env.PORT || 8080;
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const BACKEND_URL = process.env.BACKEND_URL;
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// Validate required environment variable at startup
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if (!BACKEND_URL) {
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console.error('ERROR: BACKEND_URL environment variable is required');
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process.exit(1);
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}
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// Initialize Google Auth client (auto-detects credentials on Cloud Run)
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const auth = new GoogleAuth();
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app.use(express.json());
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// Serve static React build
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app.use(express.static(path.join(__dirname, 'dist')));
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// Proxy endpoint - generates ID token and forwards to backend
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app.post('/api/chat/stream', async (req, res) => {
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console.log('Proxy request received for /api/chat/stream');
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try {
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// Get ID token client with backend URL as audience
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const client = await auth.getIdTokenClient(BACKEND_URL);
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const headers = await client.getRequestHeaders();
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console.log('Generated ID token, forwarding to backend...');
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// Forward request to backend with auth
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const backendResponse = await fetch(`${BACKEND_URL}/chat/stream`, {
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method: 'POST',
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headers: {
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'Content-Type': 'application/json',
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...headers,
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},
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body: JSON.stringify(req.body),
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});
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// Check if backend returned an error
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if (!backendResponse.ok) {
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const errorText = await backendResponse.text();
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console.error(`Backend error: ${backendResponse.status} - ${errorText}`);
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res.status(backendResponse.status).json({
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error: 'Backend error',
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status: backendResponse.status,
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message: errorText,
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});
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return;
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}
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// Set SSE headers and flush immediately
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res.setHeader('Content-Type', 'text/event-stream');
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res.setHeader('Cache-Control', 'no-cache');
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res.setHeader('Connection', 'keep-alive');
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res.flushHeaders?.();
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// Pipe raw SSE stream from backend to browser (no parsing)
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const reader = backendResponse.body.getReader();
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// Handle client disconnect
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req.on('close', () => {
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console.log('Client disconnected');
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reader.cancel();
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});
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// Stream loop
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while (true) {
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const { done, value } = await reader.read();
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if (done) {
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console.log('Stream complete');
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res.end();
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return;
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}
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res.write(value);
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}
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} catch (error) {
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console.error('Proxy error:', error);
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if (!res.headersSent) {
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res.status(500).json({ error: 'Proxy error', message: error.message });
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} else {
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res.end();
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}
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}
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});
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// Health check endpoint for Cloud Run
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app.get('/health', (req, res) => {
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res.status(200).json({ status: 'healthy' });
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});
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// SPA fallback - all other routes serve index.html
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app.get('*', (req, res) => {
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res.sendFile(path.join(__dirname, 'dist', 'index.html'));
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});
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// Listen on 0.0.0.0 for Cloud Run
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app.listen(port, '0.0.0.0', () => {
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console.log(`Server listening on ${port}`);
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console.log(`Backend URL: ${BACKEND_URL}`);
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});
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