backend: fix date changing on post

backend/server.js

@@ -155,10 +155,17 @@ function parsePostMetadata(content) {
 }
 
 // Helper function to generate filename from title
-function generateFilename(title) {
+function generateFilename(title, dateOverride = null) {
     // Create date-based filename similar to existing pattern
-    const date = new Date();
-    const dateStr = date.toISOString().slice(0, 10).replace(/-/g, "");
+    // Use override if provided, otherwise current date
+    let dateStr;
+    if (dateOverride) {
+        dateStr = dateOverride;
+    } else {
+        const date = new Date();
+        dateStr = date.toISOString().slice(0, 10).replace(/-/g, "");
+    }
+
     const slug = title
         .toLowerCase()
         .replace(/[^a-z0-9]+/g, "-")
@@ -564,8 +571,14 @@ app.put("/api/posts/:slug", requireAuth, async (req, res) => {
                 .json({ error: "Title and content are required" });
         }
 
-        // Generate new filename if title changed
-        const newFilename = generateFilename(title);
+        // Extract date from existing slug/filename to preserve it
+        // Filename format: YYYYMMDD-slug.md
+        // We assume the first 8 chars are the date if they are digits
+        const dateMatch = slug.match(/^(\d{8})-/);
+        const originalDate = dateMatch ? dateMatch[1] : null;
+
+        // Generate new filename if title changed, but PRESERVE original date
+        const newFilename = generateFilename(title, originalDate);
         const newFilePath = path.join(POSTS_DIR, newFilename);
 
         // Format the post content