fix(audiobookbay): reuse the resolved magnet when retrying (#1388) (#1398)

Retrying an AudiobookBay download re-scraped the detail page for the
magnet link before checking the torrent client, so a torrent that had
already finished in the client could not be imported while AudiobookBay
was down.

The handler now keeps the magnet it resolved in the task's retry
context, which is persisted with the download history, and a retry hands
that magnet straight to the client's existing-download check. The
context is handler-owned, so a client-supplied download URL cannot seed
it.

Fixes #1388

tests/audiobookbay/test_handler.py

@@ -6,11 +6,17 @@ from pathlib import Path
 from threading import Event
 from unittest.mock import MagicMock, patch
 
+import pytest
+
 from shelfmark.core.models import DownloadTask
 from shelfmark.download.clients import (
     DownloadState,
     DownloadStatus,
 )
+from shelfmark.download.orchestrator import (
+    _restore_task_from_retry_payload,
+    serialize_task_for_retry,
+)
 from shelfmark.release_sources.audiobookbay.handler import AudiobookBayHandler
 
 
@@ -243,6 +249,105 @@ class TestAudiobookBayHandlerDownload:
         assert result == "/path/to/book.m4b"
         mock_client.add_download.assert_not_called()
 
+    @pytest.mark.parametrize("restarted", [False, True], ids=["in_memory", "after_restart"])
+    @patch("shelfmark.release_sources.audiobookbay.handler.scraper.extract_magnet_link")
+    @patch("shelfmark.release_sources.audiobookbay.handler.get_client")
+    def test_retry_imports_finished_torrent_while_site_is_down(
+        self, mock_get_client, mock_extract_magnet, restarted
+    ):
+        """A retry reuses the first attempt's magnet instead of re-scraping AudiobookBay (#1388)."""
+        magnet = "magnet:?xt=urn:btih:abc123"
+        mock_extract_magnet.return_value = magnet
+
+        mock_client = MagicMock()
+        mock_client.name = "qbittorrent"
+        mock_client.find_existing.return_value = None
+        mock_client.add_download.return_value = "abc123"
+        mock_get_client.return_value = mock_client
+
+        handler = AudiobookBayHandler()
+        task = DownloadTask(
+            task_id="35f56a3e5734bfa69c3169ee8e605a60",
+            source="audiobookbay",
+            title="Test Book",
+            content_type="audiobook",
+            source_url="https://audiobookbay.lu/abss/test-book/",
+        )
+        recorder = ProgressRecorder()
+
+        # First attempt hands the magnet to the client, then gives up (e.g. stall timeout).
+        with patch.object(AudiobookBayHandler, "_poll_and_complete", return_value=None):
+            handler.download(
+                task=task,
+                cancel_flag=Event(),
+                progress_callback=recorder.progress_callback,
+                status_callback=recorder.status_callback,
+            )
+        mock_client.add_download.assert_called_once()
+
+        if restarted:
+            task = _restore_task_from_retry_payload(serialize_task_for_retry(task))
+            assert task is not None
+
+        # AudiobookBay goes down while the torrent finishes in the client.
+        mock_extract_magnet.reset_mock()
+        mock_extract_magnet.return_value = None
+        mock_client.find_existing.return_value = (
+            "abc123",
+            DownloadStatus(
+                progress=100,
+                state=DownloadState.COMPLETE,
+                message="Complete",
+                complete=True,
+                file_path="/path/to/book.m4b",
+            ),
+        )
+
+        with patch.object(
+            AudiobookBayHandler,
+            "_wait_for_completed_path",
+            return_value=(Path("/path/to/book.m4b"), None),
+        ):
+            result = handler.download(
+                task=task,
+                cancel_flag=Event(),
+                progress_callback=recorder.progress_callback,
+                status_callback=recorder.status_callback,
+            )
+
+        assert result == "/path/to/book.m4b"
+        mock_extract_magnet.assert_not_called()
+        assert mock_client.find_existing.call_args.args[0] == magnet
+        mock_client.add_download.assert_called_once()
+
+    @patch("shelfmark.release_sources.audiobookbay.handler.scraper.extract_magnet_link")
+    @patch("shelfmark.release_sources.audiobookbay.handler.get_client")
+    def test_failed_scrape_caches_no_magnet(self, mock_get_client, mock_extract_magnet):
+        """Only a magnet that was actually resolved is reused, so a retry scrapes again."""
+        mock_extract_magnet.return_value = None
+
+        handler = AudiobookBayHandler()
+        task = DownloadTask(
+            task_id="35f56a3e5734bfa69c3169ee8e605a60",
+            source="audiobookbay",
+            title="Test Book",
+            content_type="audiobook",
+            source_url="https://audiobookbay.lu/abss/test-book/",
+        )
+        recorder = ProgressRecorder()
+
+        for _ in range(2):
+            handler.download(
+                task=task,
+                cancel_flag=Event(),
+                progress_callback=recorder.progress_callback,
+                status_callback=recorder.status_callback,
+            )
+
+        assert mock_extract_magnet.call_count == 2
+        assert task.retry_source_context == {}
+        mock_get_client.assert_not_called()
+
     @patch("shelfmark.release_sources.audiobookbay.handler.scraper.extract_magnet_link")
     @patch("shelfmark.release_sources.audiobookbay.handler.get_client")
     def test_download_existing_in_progress(self, mock_get_client, mock_extract_magnet):