Use attachments from old CollectionFS database structure, when not yet migrated to Meteor-Files/ostrio-files, without needing to migrate database structure.

Thanks to xet7 !

server/routes/legacyAttachments.js

@@ -0,0 +1,72 @@
+import { Meteor } from 'meteor/meteor';
+import { WebApp } from 'meteor/webapp';
+import { ReactiveCache } from '/imports/reactiveCache';
+import { getAttachmentWithBackwardCompatibility, getOldAttachmentStream } from '/models/lib/attachmentBackwardCompatibility';
+
+// Ensure this file is loaded
+console.log('Legacy attachments route loaded');
+
+/**
+ * Legacy attachment download route for CollectionFS compatibility
+ * Handles downloads from old CollectionFS structure
+ */
+
+if (Meteor.isServer) {
+  // Handle legacy attachment downloads
+  WebApp.connectHandlers.use('/cfs/files/attachments', (req, res, next) => {
+    const attachmentId = req.url.split('/').pop();
+
+    if (!attachmentId) {
+      res.writeHead(404);
+      res.end('Attachment not found');
+      return;
+    }
+
+    try {
+      // Try to get attachment with backward compatibility
+      const attachment = getAttachmentWithBackwardCompatibility(attachmentId);
+
+      if (!attachment) {
+        res.writeHead(404);
+        res.end('Attachment not found');
+        return;
+      }
+
+      // Check permissions
+      const board = ReactiveCache.getBoard(attachment.meta.boardId);
+      if (!board) {
+        res.writeHead(404);
+        res.end('Board not found');
+        return;
+      }
+
+      // Check if user has permission to download
+      const userId = Meteor.userId();
+      if (!board.isPublic() && (!userId || !board.hasMember(userId))) {
+        res.writeHead(403);
+        res.end('Access denied');
+        return;
+      }
+
+      // Set appropriate headers
+      res.setHeader('Content-Type', attachment.type || 'application/octet-stream');
+      res.setHeader('Content-Length', attachment.size || 0);
+      res.setHeader('Content-Disposition', `attachment; filename="${attachment.name}"`);
+
+      // Get GridFS stream for legacy attachment
+      const fileStream = getOldAttachmentStream(attachmentId);
+      if (fileStream) {
+        res.writeHead(200);
+        fileStream.pipe(res);
+      } else {
+        res.writeHead(404);
+        res.end('File not found in GridFS');
+      }
+
+    } catch (error) {
+      console.error('Error serving legacy attachment:', error);
+      res.writeHead(500);
+      res.end('Internal server error');
+    }
+  });
+}