feat(service-storage-harness): slice 1 — harness + qbit store + client + integration

ServiceDataHarness (services/service_data.py): lifecycle-only registry of
per-concern storage — DB provisioning, idempotent migrations (ALTER TABLE
duplicate-column-name caught per-statement), cascade_delete(service_id).
QbittorrentSampleStore: append/window/prune (MAX_SAMPLES=120) in
qbittorrent.db. QbittorrentClient: cookie-login Web API client (403 re-login,
/sync/maindata). Integration registered with 3 widget kinds (totals/active/
speed). Harness initialized in main.py lifespan.

Backend: 314 pytest pass (21 new), ruff clean.

backend/tests/test_qbittorrent_client.py

@@ -0,0 +1,134 @@
+"""Unit tests for the QbittorrentClient."""
+
+from __future__ import annotations
+
+import unittest
+from unittest.mock import MagicMock, patch
+
+import requests
+
+from media_library_viewer_api.clients.qbittorrent import QbittorrentClient
+
+
+class QbittorrentClientTests(unittest.TestCase):
+    def setUp(self) -> None:
+        self.client = QbittorrentClient("https://qb.example.com", "admin", "secret", timeout=5)
+        self.session = MagicMock()
+        self.client._session = self.session
+
+    def _login_response(self, text: str = "Ok.") -> MagicMock:
+        resp = MagicMock()
+        resp.text = text
+        resp.raise_for_status.return_value = None
+        resp.status_code = 200
+        return resp
+
+    def _get_response(self, json_data: dict, status_code: int = 200) -> MagicMock:
+        resp = MagicMock()
+        resp.json.return_value = json_data
+        resp.raise_for_status.return_value = None
+        resp.status_code = status_code
+        resp.text = ""
+        return resp
+
+    def test_base_url_appends_api_v2(self) -> None:
+        c = QbittorrentClient("https://qb.example.com", "u", "p")
+        self.assertEqual(c.base_url, "https://qb.example.com/api/v2")
+
+    def test_base_url_keeps_existing_api_v2(self) -> None:
+        c = QbittorrentClient("https://qb.example.com/api/v2", "u", "p")
+        self.assertEqual(c.base_url, "https://qb.example.com/api/v2")
+
+    def test_base_url_strips_trailing_slash(self) -> None:
+        c = QbittorrentClient("https://qb.example.com/", "u", "p")
+        self.assertEqual(c.base_url, "https://qb.example.com/api/v2")
+
+    def test_empty_base_url_raises(self) -> None:
+        with self.assertRaises(ValueError):
+            QbittorrentClient("", "u", "p")
+
+    def test_empty_username_raises(self) -> None:
+        with self.assertRaises(ValueError):
+            QbittorrentClient("https://qb.example.com", "", "p")
+
+    def test_login_posts_credentials(self) -> None:
+        self.session.post.return_value = self._login_response("Ok.")
+        self.client._login()
+        self.session.post.assert_called_once()
+        call_args = self.session.post.call_args
+        self.assertIn("/auth/login", call_args.args[0])
+        self.assertEqual(call_args.kwargs["data"], {"username": "admin", "password": "secret"})
+        self.assertTrue(self.client._logged_in)
+
+    def test_login_failure_raises_runtime_error(self) -> None:
+        self.session.post.return_value = self._login_response("Fails.")
+        with self.assertRaises(RuntimeError):
+            self.client._login()
+
+    def test_get_auto_logs_in_on_first_call(self) -> None:
+        """First _get triggers login, then fetches data."""
+        self.session.post.return_value = self._login_response("Ok.")
+        self.session.get.return_value = self._get_response({"server_state": {}, "torrents": {}})
+
+        result = self.client._get("/sync/maindata")
+
+        self.session.post.assert_called_once()  # login happened
+        self.assertEqual(result, {"server_state": {}, "torrents": {}})
+
+    def test_cookie_reuse_does_not_re_login(self) -> None:
+        """After login, subsequent _get calls do NOT re-login."""
+        self.client._logged_in = True  # simulate already logged in
+        self.session.get.return_value = self._get_response({"data": 1})
+
+        self.client._get("/some/path")
+
+        self.session.post.assert_not_called()  # no re-login
+
+    def test_403_triggers_re_login(self) -> None:
+        """A 403 response triggers re-login and retries the GET."""
+        self.client._logged_in = True  # already logged in from a prior call
+        forbidden = MagicMock()
+        forbidden.status_code = 403
+        ok = self._get_response({"server_state": {}, "torrents": {}})
+        self.session.get.side_effect = [forbidden, ok]
+        self.session.post.return_value = self._login_response("Ok.")
+
+        result = self.client._get("/sync/maindata")
+
+        self.assertEqual(self.session.get.call_count, 2)  # initial + retry
+        self.session.post.assert_called_once()  # re-login happened
+        self.assertEqual(result, {"server_state": {}, "torrents": {}})
+
+    def test_maindata_returns_full_payload(self) -> None:
+        self.client._logged_in = True
+        payload = {
+            "server_state": {"dl_info_speed": 12345, "up_info_speed": 6789},
+            "torrents": {
+                "abc": {"name": "Movie.mkv", "state": "downloading", "progress": 0.5},
+                "def": {"name": "Show.mkv", "state": "uploading", "progress": 1.0},
+            },
+        }
+        self.session.get.return_value = self._get_response(payload)
+
+        result = self.client.maindata()
+
+        self.assertEqual(result["server_state"]["dl_info_speed"], 12345)
+        self.assertEqual(len(result["torrents"]), 2)
+
+    @patch("media_library_viewer_api.clients.qbittorrent.requests.Session")
+    def test_login_http_error_propagates(self, mock_session_cls: MagicMock) -> None:
+        """A network error during login propagates as requests exception."""
+        mock_session = MagicMock()
+        mock_session_cls.return_value = mock_session
+        bad_resp = MagicMock()
+        bad_resp.raise_for_status.side_effect = requests.ConnectionError("refused")
+        bad_resp.text = ""
+        mock_session.post.return_value = bad_resp
+
+        client = QbittorrentClient("https://qb.example.com", "u", "p")
+        with self.assertRaises(requests.ConnectionError):
+            client._login()
+
+
+if __name__ == "__main__":
+    unittest.main()

backend/tests/test_service_data.py

@@ -0,0 +1,148 @@
+"""Tests for ServiceDataHarness lifecycle and QbittorrentSampleStore operations."""
+
+from __future__ import annotations
+
+import pytest
+
+from media_library_viewer_api.services.qbittorrent_store import (
+    MAX_SAMPLES,
+    QBITTORRENT_CONCERN,
+    QbittorrentSampleStore,
+)
+from media_library_viewer_api.services.service_data import (
+    ServiceDataHarness,
+    StorageConcern,
+)
+
+# A throwaway concern used to test harness lifecycle in isolation.
+_TEST_CONCERN = StorageConcern(
+    concern_key="test",
+    db_filename="test.db",
+    migrations=[
+        """
+        CREATE TABLE IF NOT EXISTS test_items (
+            id INTEGER PRIMARY KEY,
+            service_id TEXT NOT NULL,
+            value TEXT
+        );
+        CREATE INDEX IF NOT EXISTS idx_test_service ON test_items(service_id);
+        """
+    ],
+    tables=["test_items"],
+)
+
+
+class TestServiceDataHarnessMigrations:
+    def test_run_migrations_creates_tables(self, tmp_path):
+        harness = ServiceDataHarness(tmp_path)
+        harness.register(_TEST_CONCERN)
+        harness.run_migrations()
+
+        with harness.connect("test") as conn:
+            tables = {row[0] for row in conn.execute("SELECT name FROM sqlite_master WHERE type='table'").fetchall()}
+        assert "test_items" in tables
+
+    def test_migrations_are_idempotent(self, tmp_path):
+        """Re-running migrations on an already-migrated DB must not crash."""
+        harness = ServiceDataHarness(tmp_path)
+        harness.register(_TEST_CONCERN)
+        harness.run_migrations()
+        harness.run_migrations()  # should not raise
+
+    def test_alter_table_idempotency(self, tmp_path):
+        """ALTER TABLE ADD COLUMN must be silently skipped on re-run."""
+        concern = StorageConcern(
+            concern_key="alter_test",
+            db_filename="alter.db",
+            migrations=[
+                "CREATE TABLE IF NOT EXISTS items (id INTEGER PRIMARY KEY)",
+                "ALTER TABLE items ADD COLUMN extra TEXT DEFAULT ''",
+            ],
+            tables=["items"],
+        )
+        harness = ServiceDataHarness(tmp_path)
+        harness.register(concern)
+        harness.run_migrations()
+        harness.run_migrations()  # second run: "duplicate column name" caught
+
+        with harness.connect("alter_test") as conn:
+            cols = {row[1] for row in conn.execute("PRAGMA table_info(items)").fetchall()}
+        assert "extra" in cols
+
+
+class TestServiceDataHarnessCascadeDelete:
+    def test_cascade_delete_removes_only_matching_service(self, tmp_path):
+        harness = ServiceDataHarness(tmp_path)
+        harness.register(_TEST_CONCERN)
+        harness.run_migrations()
+
+        with harness.connect("test") as conn:
+            conn.execute("INSERT INTO test_items (id, service_id, value) VALUES (1, 'svc-a', 'a1')")
+            conn.execute("INSERT INTO test_items (id, service_id, value) VALUES (2, 'svc-a', 'a2')")
+            conn.execute("INSERT INTO test_items (id, service_id, value) VALUES (3, 'svc-b', 'b1')")
+            conn.commit()
+
+        harness.cascade_delete("svc-a")
+
+        with harness.connect("test") as conn:
+            remaining = conn.execute("SELECT service_id, value FROM test_items ORDER BY id").fetchall()
+        assert len(remaining) == 1
+        assert remaining[0][0] == "svc-b"
+
+    def test_cascade_delete_skips_missing_concern_db(self, tmp_path):
+        """cascade_delete on a concern whose DB file doesn't exist should not crash."""
+        harness = ServiceDataHarness(tmp_path)
+        harness.register(_TEST_CONCERN)
+        # No run_migrations → DB file doesn't exist
+        harness.cascade_delete("svc-x")  # should not raise
+
+
+class TestQbittorrentSampleStore:
+    @pytest.fixture()
+    def store(self, tmp_path):
+        harness = ServiceDataHarness(tmp_path)
+        harness.register(QBITTORRENT_CONCERN)
+        harness.run_migrations()
+        return QbittorrentSampleStore(harness=harness)
+
+    def test_append_and_window(self, store):
+        store.append("svc-1", ts=100, dl_speed=500, up_speed=50)
+        store.append("svc-1", ts=200, dl_speed=600, up_speed=60)
+        store.append("svc-1", ts=300, dl_speed=700, up_speed=70)
+
+        samples = store.window("svc-1")
+        assert len(samples) == 3
+        assert samples[0]["ts"] == 100
+        assert samples[2]["ts"] == 300
+        assert samples[1]["dl_speed"] == 600
+
+    def test_window_with_since_ts(self, store):
+        store.append("svc-1", ts=100, dl_speed=500, up_speed=50)
+        store.append("svc-1", ts=200, dl_speed=600, up_speed=60)
+        store.append("svc-1", ts=300, dl_speed=700, up_speed=70)
+
+        samples = store.window("svc-1", since_ts=200)
+        assert len(samples) == 2
+        assert samples[0]["ts"] == 200
+
+    def test_prune_enforces_max_samples(self, store):
+        for i in range(MAX_SAMPLES + 10):
+            store.append("svc-1", ts=i, dl_speed=i, up_speed=i)
+
+        samples = store.window("svc-1")
+        assert len(samples) == MAX_SAMPLES
+        # The oldest 10 should have been pruned
+        assert samples[0]["ts"] == 10
+        assert samples[-1]["ts"] == MAX_SAMPLES + 9
+
+    def test_two_services_do_not_cross_contaminate(self, store):
+        store.append("svc-a", ts=100, dl_speed=500, up_speed=50)
+        store.append("svc-b", ts=200, dl_speed=600, up_speed=60)
+
+        a_samples = store.window("svc-a")
+        b_samples = store.window("svc-b")
+
+        assert len(a_samples) == 1
+        assert a_samples[0]["dl_speed"] == 500
+        assert len(b_samples) == 1
+        assert b_samples[0]["dl_speed"] == 600

backend/tests/test_services.py

@@ -57,7 +57,7 @@ def client(tmp_path):
 # ---------------------------------------------------------------------------
 
 
-def test_registry_contains_seven_service_types():
+def test_registry_contains_eight_service_types():
     assert set(SERVICE_DEFINITIONS) == {
         "prometheus",
         "alertmanager",
@@ -66,6 +66,7 @@ def test_registry_contains_seven_service_types():
         "ssh_tasks",
         "backups",
         "authentik",
+        "qbittorrent",
     }
 
 
@@ -173,6 +174,7 @@ def test_list_service_types(client):
         "jellyfin",
         "nextcloud",
         "prometheus",
+        "qbittorrent",
         "ssh_tasks",
     }