Fix CORS for stats endpoint

Ensure CORS headers are set for all responses and return 204 on preflight.

Author: Your Name

api/serverless/write-stats.js

@@ -0,0 +1,104 @@
+// Serverless function to write stats to GitHub Gist
+// Works with Vercel, Netlify, or Cloudflare Workers
+// Set GITHUB_TOKEN and GIST_ID as environment variables
+
+// Vercel/Netlify format
+export default async function handler(req, res) {
+  const allowedOrigin = 'https://persistence-ai.github.io';
+  res.setHeader('Access-Control-Allow-Origin', allowedOrigin);
+  res.setHeader('Access-Control-Allow-Methods', 'POST, OPTIONS');
+  res.setHeader('Access-Control-Allow-Headers', 'Content-Type');
+  res.setHeader('Access-Control-Max-Age', '600');
+  res.setHeader('Vary', 'Origin');
+
+  // Handle CORS preflight
+  if (req.method === 'OPTIONS') {
+    return res.status(204).end();
+  }
+
+  // Only allow POST requests
+  if (req.method !== 'POST') {
+    return res.status(405).json({ error: 'Method not allowed' });
+  }
+
+  const { GITHUB_TOKEN, GIST_ID } = process.env;
+
+  if (!GITHUB_TOKEN || !GIST_ID) {
+    return res.status(500).json({ error: 'Server configuration missing' });
+  }
+
+  try {
+    const { type, platform, fingerprint, date } = req.body;
+
+    // Fetch current Gist
+    const gistResponse = await fetch(`https://api.github.com/gists/${GIST_ID}`, {
+      headers: {
+        'Accept': 'application/vnd.github.v3+json',
+        'Authorization': `token ${GITHUB_TOKEN}`,
+      },
+    });
+
+    if (!gistResponse.ok) {
+      throw new Error(`Failed to fetch gist: ${gistResponse.status}`);
+    }
+
+    const gist = await gistResponse.json();
+    const filename = Object.keys(gist.files)[0];
+    const currentStats = JSON.parse(gist.files[filename].content);
+
+    // Update stats based on type
+    const updatedStats = { ...currentStats };
+
+    if (type === 'copy' && platform) {
+      // Increment copy count for platform
+      updatedStats.copyCounts[platform] = (updatedStats.copyCounts[platform] || 0) + 1;
+      updatedStats.copyCounts.total = 
+        (updatedStats.copyCounts.windows || 0) + 
+        (updatedStats.copyCounts.linux || 0) + 
+        (updatedStats.copyCounts.mac || 0);
+    }
+
+    if (type === 'pageView' && fingerprint && date) {
+      // Check if new visitor
+      const isNewVisitor = !updatedStats.visitors.fingerprints[fingerprint];
+      
+      if (isNewVisitor) {
+        updatedStats.visitors.total = (updatedStats.visitors.total || 0) + 1;
+        updatedStats.visitors.fingerprints[fingerprint] = date;
+        updatedStats.visitors.daily[date] = (updatedStats.visitors.daily[date] || 0) + 1;
+      }
+
+      // Always increment page views
+      updatedStats.pageViews.total = (updatedStats.pageViews.total || 0) + 1;
+      updatedStats.pageViews.daily[date] = (updatedStats.pageViews.daily[date] || 0) + 1;
+    }
+
+    updatedStats.lastUpdated = new Date().toISOString();
+
+    // Update Gist
+    const updateResponse = await fetch(`https://api.github.com/gists/${GIST_ID}`, {
+      method: 'PATCH',
+      headers: {
+        'Accept': 'application/vnd.github.v3+json',
+        'Authorization': `token ${GITHUB_TOKEN}`,
+        'Content-Type': 'application/json',
+      },
+      body: JSON.stringify({
+        files: {
+          [filename]: {
+            content: JSON.stringify(updatedStats, null, 2),
+          },
+        },
+      }),
+    });
+
+    if (!updateResponse.ok) {
+      throw new Error(`Failed to update gist: ${updateResponse.status}`);
+    }
+
+    return res.status(200).json({ success: true, stats: updatedStats });
+  } catch (error) {
+    console.error('Error updating stats:', error);
+    return res.status(500).json({ error: error.message });
+  }
+}