Tilføj retries til URL-refresh ved manglende @microsoft.graph.downloadUrl i API svar

GEMINI.md

@@ -17,7 +17,8 @@ A production-ready Python utility for robust synchronization of SharePoint Onlin
 2.  **Reliability:** Includes a custom `retry_request` decorator for Exponential Backoff, handling throttling (429) and transient network errors.
 3.  **Concurrency:** Multi-threaded architecture (5 workers) for simultaneous scanning and downloading.
 4.  **Pagination:** Full support for OData pagination, ensuring complete folder traversal regardless of item count.
-5.  **Logging & Audit:** Integrated Python `logging` to `sharepoint_download.log` and structured CSV reports for error auditing.
+5.  **Self-Healing Sessions:** Automatically detects and resolves 401 Unauthorized errors by refreshing both expiring Microsoft Graph Download URLs and MSAL Access Tokens mid-process.
+6.  **Logging & Audit:** Integrated Python `logging` to `sharepoint_download.log` and structured CSV reports for error auditing.
 
 ## Building and Running
 
@@ -30,7 +31,8 @@ A production-ready Python utility for robust synchronization of SharePoint Onlin
 
 ## Development Conventions
 
-*   **Error Handling:** Always use the `safe_get` (retry-wrapped) method for Graph API calls.
+*   **Error Handling:** Always use the `safe_get` (retry-wrapped) method for Graph API calls. For item-specific operations, use `get_fresh_download_url` to handle token/URL expiry.
+*   **Authentication:** Use `get_headers(app, force_refresh=True)` when a 401 error is encountered from Graph API to ensure session continuity.
 *   **Thread Safety:** Use `report_lock` when updating the shared error list from worker threads.
 *   **Logging:** Prefer `logger.info()` or `logger.error()` over `print()` to ensure persistence in `sharepoint_download.log`.
 *   **Integrity:** Always verify file integrity using `size` and `quickXorHash` where available.

download_sharepoint.py

@@ -112,22 +112,37 @@ def get_drive_id(app, site_id, drive_name):
 
 # --- Punkt 2: Resume / Chunked Download logic ---
 def get_fresh_download_url(app, drive_id, item_id):
-    """Fetches a fresh download URL for a specific item ID with token refresh support."""
+    """Fetches a fresh download URL for a specific item ID with retries and robust error handling."""
-    url = f"https://graph.microsoft.com/v1.0/drives/{drive_id}/items/{item_id}?$select=id,@microsoft.graph.downloadUrl"
+    url = f"https://graph.microsoft.com/v1.0/drives/{drive_id}/items/{item_id}"
     
+    for attempt in range(3):
         try:
             headers = get_headers(app)
             response = requests.get(url, headers=headers, timeout=60)
             
             if response.status_code == 401:
-            logger.info("Access Token expired. Forcing refresh...")
+                logger.info(f"Access Token expired during refresh (Attempt {attempt+1}). Forcing refresh...")
                 headers = get_headers(app, force_refresh=True)
                 response = requests.get(url, headers=headers, timeout=60)
                 
             response.raise_for_status()
-        return response.json().get('@microsoft.graph.downloadUrl'), None
+            data = response.json()
+            download_url = data.get('@microsoft.graph.downloadUrl')
+            
+            if download_url:
+                return download_url, None
+            
+            # If item exists but URL is missing, it might be a transient SharePoint issue
+            logger.warning(f"Attempt {attempt+1}: '@microsoft.graph.downloadUrl' missing for {item_id}. Retrying in 1s...")
+            time.sleep(1)
+            
         except Exception as e:
+            if attempt == 2:
                 return None, str(e)
+            logger.warning(f"Attempt {attempt+1} failed: {e}. Retrying...")
+            time.sleep(1)
+            
+    return None, "Item returned but '@microsoft.graph.downloadUrl' was missing after 3 attempts."
 
 def download_single_file(app, drive_id, item_id, local_path, expected_size, display_name, remote_hash=None, initial_url=None):
     try: