Add: thumbnail gen task for pdfs

backend/apps/files/tasks.py

@@ -215,7 +215,72 @@ def generate_video_thumbnail(
         _handle_task_error(e, file_id, "video thumbnail generation")
 
 
+@shared_task(autoretry_for=(Exception,), retry_backoff=True, max_retries=5)
+def generate_pdf_thumbnail(
+    file_id: int, page: int = 1, size: Optional[Tuple[int, int]] = None, dpi: int = 200
+) -> str:
+    """
+    Generate PDF thumbnails using pdf2image and update the PostFileModel instance.
+
+    Args:
+        file_id (int): ID of the PostFileModel instance
+        page (int): Page number to use for thumbnail (defaults to first page)
+        size (Tuple[int, int], optional): Desired thumbnail (width, height) or None to maintain original size
+        dpi (int): DPI for rendering the PDF (higher values result in larger images)
+
+    Returns:
+        str: Success message or error message
+    """
+    try:
+        from pdf2image import convert_from_path
+
+        with transaction.atomic():
+            # Retrieve the PostFileModel instance with a lock
+            pstfile = PostFileModel.objects.select_for_update().get(id=file_id)
+
+            if not pstfile.file:
+                return "Error: PDF file not found for the given file_id."
+
+            pdf_path = pstfile.file.path
+
+            # Setup output path
+            _, thumbnail_file_path = _setup_output_path(
+                pstfile.hash_blake3, "pdf_thumbnail"
+            )
+            thumbnail_filename = Path(thumbnail_file_path).name
+
+            # Convert PDF to image using pdf2image
+            # first_page and last_page are 1-indexed
+            images = convert_from_path(
+                pdf_path, dpi=dpi, first_page=page, last_page=page
+            )
+
+            # Get the first page (should be the only one based on our parameters)
+            if not images:
+                raise ValueError(f"Could not extract page {page} from PDF")
+
+            image = images[0]
+
+            # Resize if size is specified
+            if size:
+                image = image.resize(size, PillowImage.LANCZOS)
+
+            # Save the image
+            image.save(thumbnail_file_path, "PNG")
+
+            # Update model with new thumbnail
+            _update_file_model(pstfile, thumbnail_file_path, thumbnail_filename)
+
+            # Clean up temporary file
             os.remove(thumbnail_file_path)
 
+        return f"PDF thumbnail generated successfully for file {file_id}"
 
+    except ImportError:
+        error_message = (
+            "pdf2image library is not installed. Install it with: pip install pdf2image"
+        )
+        print(error_message)
+        raise
     except Exception as e:
+        _handle_task_error(e, file_id, "PDF thumbnail generation")