feat: Enhance product management by adding WebSocket support for real-time updates, implement product loading in categories, and improve caching for category products.

server.js

@@ -1,4 +1,6 @@
 import express from 'express';
+import { createServer } from 'http';
+import { Server } from 'socket.io';
 import path from 'path';
 import { fileURLToPath } from 'url';
 import fs from 'fs/promises';
@@ -6,8 +8,11 @@ import fs from 'fs/promises';
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
 
-export function startServer(categorySyncer) {
+export function startServer(categorySyncer, categoryProductsSyncer) {
     const app = express();
+    const httpServer = createServer(app);
+    const io = new Server(httpServer);
+
     const PORT = process.env.SERVER_PORT || 3000;
     const HOST = process.env.SERVER_HOST || '0.0.0.0';
     const CACHE_DIR = process.env.CACHE_LOCATION || './cache';
@@ -15,7 +20,8 @@ export function startServer(categorySyncer) {
     // Cache for ETags and data
     const cache = {
         categories: { etag: null, data: null },
-        html: { etag: null, data: null }
+        html: { etag: null, data: null },
+        products: new Map() // id -> { etag, data }
     };
 
     // Function to calculate ETag for categories
@@ -34,6 +40,24 @@ export function startServer(categorySyncer) {
         }
     }
 
+    // Function to calculate ETag for a specific category's products
+    async function updateProductCache(id) {
+        try {
+            const productPath = path.join(CACHE_DIR, 'products', `category_${id}.json`);
+            const data = await fs.readFile(productPath, 'utf-8');
+            const crypto = await import('crypto');
+            const etag = crypto.createHash('md5').update(data).digest('hex');
+            cache.products.set(id, { etag, data });
+        } catch (err) {
+            // If file missing, remove from cache
+            if (err.code === 'ENOENT') {
+                cache.products.delete(id);
+            } else {
+                console.error(`Error updating product cache for category ${id}:`, err);
+            }
+        }
+    }
+
     // Function to calculate ETag for HTML
     async function updateHtmlCache() {
         try {
@@ -56,10 +80,27 @@ export function startServer(categorySyncer) {
         categorySyncer.on('synced', ({ changed }) => {
             if (changed) {
                 updateCategoriesCache();
+                io.emit('categoriesUpdated');
             }
         });
     }
 
+    // Update product cache when category products update
+    if (categoryProductsSyncer) {
+        categoryProductsSyncer.on('categoryUpdated', ({ id }) => {
+            updateProductCache(id);
+            io.emit('categoryProductsUpdated', { id });
+        });
+    }
+
+    // Socket.io connection
+    io.on('connection', (socket) => {
+        console.log('🔌 Client connected');
+        socket.on('disconnect', () => {
+            console.log('🔌 Client disconnected');
+        });
+    });
+
     // Serve category tree JSON (with ETag for conditional caching)
     app.get('/api/categories', async (req, res) => {
         try {
@@ -78,6 +119,38 @@ export function startServer(categorySyncer) {
         }
     });
 
+    // Serve category products JSON (with ETag)
+    app.get('/api/categories/:id/products', async (req, res) => {
+        try {
+            const id = parseInt(req.params.id);
+            
+            // Lazy load if not in cache
+            if (!cache.products.has(id)) {
+                await updateProductCache(id);
+            }
+
+            const cached = cache.products.get(id);
+
+            if (!cached) {
+                return res.status(404).json({ error: 'Category products not found' });
+            }
+
+            // Check if client has cached version
+            if (req.headers['if-none-match'] === cached.etag) {
+                return res.status(304).end(); // Not Modified
+            }
+
+            // Set cache headers with ETag
+            res.set('Cache-Control', 'public, max-age=60, must-revalidate');
+            res.set('ETag', cached.etag);
+            
+            res.json(JSON.parse(cached.data));
+        } catch (err) {
+            console.error(`Error serving products for category ${req.params.id}:`, err);
+            res.status(500).json({ error: 'Failed to load products' });
+        }
+    });
+
     // Serve category images (long cache - images rarely change)
     app.get('/img/cat/:id.avif', (req, res) => {
         const { id } = req.params;
@@ -113,7 +186,7 @@ export function startServer(categorySyncer) {
         }
     });
 
-    app.listen(PORT, HOST, () => {
+    httpServer.listen(PORT, HOST, () => {
         console.log(`🌐 Server running on http://${HOST}:${PORT}`);
     });
 }