Merge pull request #40 from PostHog/add-dev-server

Add dev server with hot-rebuild of the resource zip file

Author: daniloc

package.json

@@ -5,6 +5,7 @@
   "description": "PostHog example projects",
   "scripts": {
     "build:docs": "node scripts/build-examples-mcp-resources.js",
+    "dev": "node scripts/dev-server.js",
     "test:plugins": "vitest run scripts/plugins/tests",
     "test:plugins:watch": "vitest scripts/plugins/tests"
   },

scripts/dev-server.js

@@ -0,0 +1,179 @@
+#!/usr/bin/env node
+
+/**
+ * Development server for MCP resources
+ *
+ * Serves the generated ZIP file over HTTP and watches markdown files
+ * for changes, automatically rebuilding when needed.
+ *
+ * Usage: npm run dev
+ *
+ * To use a different port:
+ *   PORT=3000 npm run dev
+ *
+ * Then update the MCP server command to match:
+ *   pnpm run dev:local-resources (and update wrangler --var flag)
+ */
+
+const http = require('http');
+const fs = require('fs');
+const path = require('path');
+const { spawn } = require('child_process');
+
+const PORT = process.env.PORT || 8765;
+const ZIP_PATH = path.join(__dirname, '..', 'dist', 'examples-mcp-resources.zip');
+
+// Directories to watch for changes
+const WATCH_DIRS = [
+    path.join(__dirname, '..', 'llm-prompts'),
+    path.join(__dirname, '..', 'mcp-commands'),
+    path.join(__dirname, '..', 'basics'),
+];
+
+let isRebuilding = false;
+let rebuildQueued = false;
+
+/**
+ * Run the build script
+ */
+function rebuild() {
+    if (isRebuilding) {
+        rebuildQueued = true;
+        return;
+    }
+
+    console.log('\n🔨 Rebuilding resources...');
+    isRebuilding = true;
+
+    const buildProcess = spawn('node', [path.join(__dirname, 'build-examples-mcp-resources.js')], {
+        stdio: 'inherit',
+        cwd: path.join(__dirname, '..')
+    });
+
+    buildProcess.on('close', (code) => {
+        isRebuilding = false;
+
+        if (code === 0) {
+            console.log('✅ Rebuild complete!\n');
+        } else {
+            console.error(`❌ Build failed with code ${code}\n`);
+        }
+
+        // If another rebuild was queued, run it now
+        if (rebuildQueued) {
+            rebuildQueued = false;
+            rebuild();
+        }
+    });
+}
+
+/**
+ * Watch directories for markdown file changes
+ */
+function setupWatchers() {
+    console.log('\n👀 Watching for changes in:');
+
+    WATCH_DIRS.forEach(dir => {
+        if (!fs.existsSync(dir)) {
+            console.log(`   ⚠️  ${path.relative(path.join(__dirname, '..'), dir)} (not found, skipping)`);
+            return;
+        }
+
+        console.log(`   📁 ${path.relative(path.join(__dirname, '..'), dir)}`);
+
+        // Watch recursively
+        fs.watch(dir, { recursive: true }, (eventType, filename) => {
+            if (!filename) return;
+
+            // Only trigger on markdown or JSON files
+            if (filename.endsWith('.md') || filename.endsWith('.json')) {
+                console.log(`\n📝 Changed: ${filename}`);
+                rebuild();
+            }
+        });
+    });
+}
+
+/**
+ * Create HTTP server to serve the ZIP file
+ */
+function createServer() {
+    const server = http.createServer((req, res) => {
+        // Only serve the ZIP file
+        if (req.url === '/examples-mcp-resources.zip' || req.url === '/') {
+            if (!fs.existsSync(ZIP_PATH)) {
+                res.writeHead(404, { 'Content-Type': 'text/plain' });
+                res.end('ZIP file not found. Run build first.');
+                return;
+            }
+
+            const stat = fs.statSync(ZIP_PATH);
+            const fileSize = stat.size;
+            const fileStream = fs.createReadStream(ZIP_PATH);
+
+            res.writeHead(200, {
+                'Content-Type': 'application/zip',
+                'Content-Length': fileSize,
+                'Content-Disposition': 'attachment; filename="examples-mcp-resources.zip"',
+                'Cache-Control': 'no-cache, no-store, must-revalidate',
+                'Pragma': 'no-cache',
+                'Expires': '0'
+            });
+
+            fileStream.pipe(res);
+
+            console.log(`📦 Served ZIP file (${(fileSize / 1024).toFixed(1)} KB)`);
+        } else {
+            res.writeHead(404, { 'Content-Type': 'text/plain' });
+            res.end('Not found. Use /examples-mcp-resources.zip');
+        }
+    });
+
+    server.listen(PORT, () => {
+        console.log('\n🚀 Development server started!');
+        console.log(`\n📍 ZIP available at: http://localhost:${PORT}/examples-mcp-resources.zip`);
+        console.log('\n💡 To use with MCP server, set environment variable:');
+        console.log(`   POSTHOG_MCP_LOCAL_EXAMPLES_URL=http://localhost:${PORT}/examples-mcp-resources.zip`);
+    });
+}
+
+/**
+ * Main entry point
+ */
+async function main() {
+    console.log('🎯 PostHog MCP Resources Development Server');
+    console.log('==========================================');
+
+    // Initial build if ZIP doesn't exist
+    if (!fs.existsSync(ZIP_PATH)) {
+        console.log('\n⚠️  ZIP file not found. Running initial build...');
+        await new Promise((resolve) => {
+            const buildProcess = spawn('node', [path.join(__dirname, 'build-examples-mcp-resources.js')], {
+                stdio: 'inherit',
+                cwd: path.join(__dirname, '..')
+            });
+            buildProcess.on('close', resolve);
+        });
+    }
+
+    // Start server
+    createServer();
+
+    // Setup file watchers
+    setupWatchers();
+
+    console.log('\n✨ Ready for development!');
+    console.log('   Press Ctrl+C to stop\n');
+}
+
+// Handle graceful shutdown
+process.on('SIGINT', () => {
+    console.log('\n\n👋 Shutting down dev server...');
+    process.exit(0);
+});
+
+// Run
+main().catch(err => {
+    console.error('Fatal error:', err);
+    process.exit(1);
+});