feat(example-images): add stop control for download panel

tests/utils/test_example_images_download_manager_unit.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import asyncio
+import time
 from typing import Any, Dict
 
 import pytest
@@ -128,6 +129,59 @@ async def test_pause_and_resume_flow(monkeypatch: pytest.MonkeyPatch, tmp_path)
     await asyncio.wait_for(task, timeout=1)
 
 
+async def test_stop_download_transitions_to_stopped(monkeypatch: pytest.MonkeyPatch, tmp_path) -> None:
+    settings_manager = get_settings_manager()
+    settings_manager.settings["example_images_path"] = str(tmp_path)
+    settings_manager.settings["libraries"] = {"default": {}}
+    settings_manager.settings["active_library"] = "default"
+
+    ws_manager = RecordingWebSocketManager()
+    manager = download_module.DownloadManager(ws_manager=ws_manager)
+
+    started = asyncio.Event()
+    release = asyncio.Event()
+
+    async def fake_download(self, *_args):
+        started.set()
+        await release.wait()
+        async with self._state_lock:
+            if self._stop_requested and self._progress['status'] == 'stopping':
+                self._progress['status'] = 'stopped'
+            else:
+                self._progress['status'] = 'completed'
+            self._progress['end_time'] = time.time()
+            self._stop_requested = False
+        await self._broadcast_progress(status=self._progress['status'])
+        async with self._state_lock:
+            self._is_downloading = False
+            self._download_task = None
+
+    monkeypatch.setattr(
+        download_module.DownloadManager,
+        "_download_all_example_images",
+        fake_download,
+    )
+
+    await manager.start_download({})
+    await asyncio.wait_for(started.wait(), timeout=1)
+
+    stop_response = await manager.stop_download(object())
+    assert stop_response == {"success": True, "message": "Download stopping"}
+    assert manager._progress["status"] == "stopping"
+
+    task = manager._download_task
+    assert task is not None
+    release.set()
+    await asyncio.wait_for(task, timeout=1)
+
+    assert manager._progress["status"] == "stopped"
+    assert manager._is_downloading is False
+    assert manager._stop_requested is False
+    statuses = [payload["status"] for payload in ws_manager.payloads]
+    assert "stopping" in statuses
+    assert "stopped" in statuses
+
+
 async def test_pause_or_resume_without_running_download(monkeypatch: pytest.MonkeyPatch) -> None:
     manager = download_module.DownloadManager(ws_manager=RecordingWebSocketManager())
 
@@ -136,3 +190,6 @@ async def test_pause_or_resume_without_running_download(monkeypatch: pytest.Monk
 
     with pytest.raises(download_module.DownloadNotRunningError):
         await manager.resume_download(object())
+
+    with pytest.raises(download_module.DownloadNotRunningError):
+        await manager.stop_download(object())