feat(filename): enhance item filename generation and extraction for hierarchical structure

Author: ErcinDedeoglu

src/sync/item-packer.ts

@@ -88,20 +88,75 @@ export function calculateChecksum(data: string): string {
 
 /**
  * Generate filename for an item in storage.
+ *
+ * Item IDs come from category-loader.ts in format: {type}/{parent}/{file}.json
+ * We transform these to a hierarchical structure for remote storage:
+ * - Sessions: session/{projectHash}/{sessionId}.json → sessions/{projectHash}/{sessionId}.json.gz
+ * - Messages: message/{sessionId}/{messageId}.json → messages/{sessionId}/{messageId}.json.gz
+ * - Parts:    part/{messageId}/{partId}.json → messages/parts/{messageId}/{partId}.json.gz
  */
 export function getItemFilename(category: SyncCategory, itemId: string): string {
-  // Sanitize item ID for filename (replace unsafe chars)
-  const safeId = itemId.replace(/[/\\:*?"<>|]/g, '_');
+  if (category === 'sessions') {
+    // itemId: session/{projectHash}/{sessionId}.json
+    // Output: sessions/{projectHash}/{sessionId}.json.gz
+    const match = /^session\/([^/]+)\/(.+)\.json$/.exec(itemId);
+    if (match?.[1] && match[2]) {
+      return `sessions/${match[1]}/${match[2]}.json.gz`;
+    }
+  }
+
+  if (category === 'messages') {
+    // Message: message/{sessionId}/{messageId}.json
+    // Output: messages/{sessionId}/{messageId}.json.gz
+    const msgMatch = /^message\/(ses_[^/]+)\/(.+)\.json$/.exec(itemId);
+    if (msgMatch?.[1] && msgMatch[2]) {
+      return `messages/${msgMatch[1]}/${msgMatch[2]}.json.gz`;
+    }
+
+    // Part: part/{messageId}/{partId}.json
+    // Output: messages/parts/{messageId}/{partId}.json.gz
+    const partMatch = /^part\/(msg_[^/]+)\/(.+)\.json$/.exec(itemId);
+    if (partMatch?.[1] && partMatch[2]) {
+      return `messages/parts/${partMatch[1]}/${partMatch[2]}.json.gz`;
+    }
+  }
+
+  // Fallback: flat structure (replace path separators and unsafe chars)
+  const safeId = itemId.replace(/[/\\:*?"<>|]/g, '_').replace(/\.json$/, '');
   return `${category}/${safeId}.json.gz`;
 }
 
 /**
  * Extract item ID from filename.
+ *
+ * Reverses the hierarchical remote path back to the original item ID format
+ * used by category-loader.ts.
  */
 export function getItemIdFromFilename(filename: string): string | null {
-  const regex = /^[^/]+\/(.+)\.json\.gz$/;
-  const match = regex.exec(filename);
-  return match ? (match[1] ?? null) : null;
+  // Sessions: sessions/{projectHash}/{sessionId}.json.gz -> session/{projectHash}/{sessionId}.json
+  const sessionMatch = /^sessions\/([^/]+)\/([^/]+)\.json\.gz$/.exec(filename);
+  if (sessionMatch?.[1] && sessionMatch[2]) {
+    return `session/${sessionMatch[1]}/${sessionMatch[2]}.json`;
+  }
+
+  // Messages: messages/{sessionId}/{messageId}.json.gz -> message/{sessionId}/{messageId}.json
+  const msgMatch = /^messages\/(ses_[^/]+)\/([^/]+)\.json\.gz$/.exec(filename);
+  if (msgMatch?.[1] && msgMatch[2]) {
+    return `message/${msgMatch[1]}/${msgMatch[2]}.json`;
+  }
+
+  // Parts: messages/parts/{messageId}/{partId}.json.gz -> part/{messageId}/{partId}.json
+  const partMatch = /^messages\/parts\/(msg_[^/]+)\/([^/]+)\.json\.gz$/.exec(filename);
+  if (partMatch?.[1] && partMatch[2]) {
+    return `part/${partMatch[1]}/${partMatch[2]}.json`;
+  }
+
+  // Fallback: old flat format - restore slashes from underscores and add .json
+  const fallbackMatch = /^[^/]+\/(.+)\.json\.gz$/.exec(filename);
+  if (fallbackMatch?.[1]) {
+    return fallbackMatch[1].replace(/_/g, '/') + '.json';
+  }
+  return null;
 }
 
 /**