Add prerendering

frontend/package.json

@@ -3,7 +3,9 @@
   "version": "1.0.0",
   "scripts": {
     "dev": "webpack serve --mode development --port 3030",
-    "build": "webpack --mode production",
+    "build": "webpack --mode production && node scripts/prerender.mjs",
+    "build:no-prerender": "webpack --mode production",
+    "prerender": "node scripts/prerender.mjs",
     "typecheck": "tsc --noEmit",
     "lint": "eslint src --ext .ts,.tsx",
     "lint:fix": "eslint src --ext .ts,.tsx --fix",
@@ -38,9 +40,11 @@
     "eslint-plugin-react": "^7.34.0",
     "eslint-plugin-react-hooks": "^4.6.0",
     "html-webpack-plugin": "^5.6.0",
+    "mini-css-extract-plugin": "^2.9.0",
     "postcss": "^8.4.0",
     "postcss-loader": "^8.0.0",
     "prettier": "^3.2.0",
+    "puppeteer": "^24.0.0",
     "style-loader": "^4.0.0",
     "tailwindcss": "^3.4.0",
     "ts-loader": "^9.5.0",

frontend/scripts/prerender.mjs

@@ -0,0 +1,140 @@
+import { createServer } from 'http';
+import { readFileSync, writeFileSync, existsSync, statSync } from 'fs';
+import { join, extname } from 'path';
+import { launch } from 'puppeteer';
+
+const DIST_DIR = join(import.meta.dirname, '..', 'dist');
+const INDEX_PATH = join(DIST_DIR, 'index.html');
+
+const MIME_TYPES = {
+  '.html': 'text/html',
+  '.js': 'application/javascript',
+  '.css': 'text/css',
+  '.json': 'application/json',
+  '.png': 'image/png',
+  '.jpg': 'image/jpeg',
+  '.svg': 'image/svg+xml',
+};
+
+function startServer() {
+  return new Promise((resolve) => {
+    const server = createServer((req, res) => {
+      const url = new URL(req.url, 'http://localhost');
+      let filePath = join(DIST_DIR, url.pathname === '/' ? 'index.html' : url.pathname);
+
+      if (!existsSync(filePath) || !statSync(filePath).isFile()) {
+        // SPA fallback
+        filePath = INDEX_PATH;
+      }
+
+      const ext = extname(filePath);
+      const mime = MIME_TYPES[ext] || 'application/octet-stream';
+      const content = readFileSync(filePath);
+      res.writeHead(200, { 'Content-Type': mime });
+      res.end(content);
+    });
+
+    server.listen(0, '127.0.0.1', () => {
+      const port = server.address().port;
+      resolve({ server, port });
+    });
+  });
+}
+
+async function prerender() {
+  console.log('Starting prerender...');
+
+  const { server, port } = await startServer();
+  console.log(`Static server on port ${port}`);
+
+  const browser = await launch({
+    headless: true,
+    args: ['--no-sandbox', '--disable-setuid-sandbox'],
+  });
+
+  try {
+    const page = await browser.newPage();
+
+    // Intercept API requests to prevent real fetches and retry loops
+    await page.setRequestInterception(true);
+    page.on('request', (req) => {
+      const url = req.url();
+      if (url.includes('/api/features')) {
+        req.respond({
+          status: 200,
+          contentType: 'application/json',
+          body: JSON.stringify({ groups: [] }),
+        });
+      } else if (url.includes('/api/poi-categories')) {
+        req.respond({
+          status: 200,
+          contentType: 'application/json',
+          body: JSON.stringify({ groups: [] }),
+        });
+      } else if (url.includes('/api/')) {
+        req.respond({
+          status: 200,
+          contentType: 'application/json',
+          body: '{}',
+        });
+      } else {
+        req.continue();
+      }
+    });
+
+    await page.goto(`http://127.0.0.1:${port}/`, {
+      waitUntil: 'networkidle0',
+      timeout: 30000,
+    });
+
+    // Wait for the home page heading to render
+    await page.waitForSelector('h1', { timeout: 10000 });
+
+    // Extract and clean the rendered HTML
+    const html = await page.evaluate(() => {
+      const root = document.getElementById('root');
+      if (!root) return '';
+
+      // Strip fade-in-visible classes (added by IntersectionObserver effects)
+      root.querySelectorAll('.fade-in-visible').forEach((el) => {
+        el.classList.remove('fade-in-visible');
+      });
+
+      // Clean canvas elements (dimensions set by ResizeObserver effect)
+      root.querySelectorAll('canvas').forEach((canvas) => {
+        canvas.removeAttribute('width');
+        canvas.removeAttribute('height');
+        canvas.style.removeProperty('width');
+        canvas.style.removeProperty('height');
+      });
+
+      return root.innerHTML;
+    });
+
+    if (!html || html.length < 100) {
+      throw new Error('Prerender produced too little HTML — something went wrong');
+    }
+
+    // Inject into dist/index.html
+    const indexHtml = readFileSync(INDEX_PATH, 'utf-8');
+    const updated = indexHtml.replace(
+      '<div id="root"></div>',
+      `<div id="root">${html}</div>`
+    );
+
+    if (updated === indexHtml) {
+      throw new Error('Could not find <div id="root"></div> in index.html');
+    }
+
+    writeFileSync(INDEX_PATH, updated);
+    console.log(`Prerendered ${html.length} chars into dist/index.html`);
+  } finally {
+    await browser.close();
+    server.close();
+  }
+}
+
+prerender().catch((err) => {
+  console.error('Prerender failed:', err);
+  process.exit(1);
+});

frontend/src/components/Map.tsx

@@ -36,6 +36,7 @@ interface MapProps {
   onHexagonHover: (h3: string | null) => void;
   initialViewState?: ViewState;
   theme?: 'light' | 'dark';
+  screenshotMode?: boolean;
 }
 
 const INITIAL_VIEW: ViewState = {
@@ -86,6 +87,7 @@ export default memo(function Map({
   onHexagonHover,
   initialViewState,
   theme = 'light',
+  screenshotMode = false,
 }: MapProps) {
   const containerRef = useRef<HTMLDivElement>(null);
   const [viewState, setViewState] = useState<ViewState>(initialViewState || INITIAL_VIEW);
@@ -389,6 +391,17 @@ export default memo(function Map({
       >
         <DeckOverlay layers={layers} getTooltip={null} />
       </MapGL>
+      {screenshotMode ? (
+        <div className="absolute inset-0 flex items-center justify-center z-20 pointer-events-none">
+          <h1
+            className="text-5xl font-bold text-white drop-shadow-lg"
+            style={{ textShadow: '0 2px 8px rgba(0,0,0,0.6)' }}
+          >
+            Your perfect postcodes
+          </h1>
+        </div>
+      ) : (
+        <>
           <PostcodeSearch onFlyTo={handleFlyTo} />
           {viewSource === 'eye' && viewFeature && (
             <div className="absolute top-4 left-1/2 -translate-x-1/2 z-20 flex items-center gap-3 bg-white dark:bg-warm-800 rounded-lg shadow-lg px-5 py-3">
@@ -435,6 +448,8 @@ export default memo(function Map({
               <div className="text-gray-500 dark:text-warm-400 text-xs">{popupInfo.category}</div>
             </div>
           )}
+        </>
+      )}
     </div>
   );
 });

frontend/src/index.tsx

@@ -1,4 +1,4 @@
-import { createRoot } from 'react-dom/client';
+import { createRoot, hydrateRoot } from 'react-dom/client';
 import App from './App';
 import './index.css';
 import { initPlausible } from './usePlausible';
@@ -9,5 +9,9 @@ const container = document.getElementById('root');
 if (!container) {
   throw new Error('Root element not found');
 }
-const root = createRoot(container);
-root.render(<App />);
+
+if (container.children.length > 0) {
+  hydrateRoot(container, <App />);
+} else {
+  createRoot(container).render(<App />);
+}

frontend/webpack.config.js

@@ -1,5 +1,6 @@
 const path = require('path');
 const HtmlWebpackPlugin = require('html-webpack-plugin');
+const MiniCssExtractPlugin = require('mini-css-extract-plugin');
 
 module.exports = (env, argv) => {
   const isProduction = argv.mode === 'production';
@@ -26,7 +27,11 @@ module.exports = (env, argv) => {
         },
         {
           test: /\.css$/,
-          use: ['style-loader', 'css-loader', 'postcss-loader'],
+          use: [
+            isProduction ? MiniCssExtractPlugin.loader : 'style-loader',
+            'css-loader',
+            'postcss-loader',
+          ],
         },
       ],
     },
@@ -34,6 +39,7 @@ module.exports = (env, argv) => {
       new HtmlWebpackPlugin({
         template: './src/index.html',
       }),
+      ...(isProduction ? [new MiniCssExtractPlugin()] : []),
     ],
     devServer: {
       port: 3000,