test(S01/T02): Built pydantic-settings config (env + YAML + zero-config…

- backend/app/core/config.py
- backend/app/core/database.py
- backend/app/core/sse_broker.py
- backend/tests/conftest.py

.gsd/milestones/M001/slices/S01/S01-PLAN.md

@@ -59,7 +59,7 @@ All tests run from `backend/`:
   - Verify: `cd backend && pip install -e ".[dev]" && python -m pytest tests/test_models.py -v`
   - Done when: `pip install -e ".[dev]"` succeeds, all model tests pass, `from app.models.job import Job, JobStatus, ProgressEvent, JobCreate, FormatInfo` works
 
-- [ ] **T02: Build config system, database layer, and SSE broker** `est:1h`
+- [x] **T02: Build config system, database layer, and SSE broker** `est:1h`
   - Why: These three infrastructure modules are the foundation everything else depends on. Config provides settings to database and download service. Database stores all job state. SSE broker is the thread-safe event distribution mechanism. All three are pure infrastructure with well-defined interfaces.
   - Files: `backend/app/core/config.py`, `backend/app/core/database.py`, `backend/app/core/sse_broker.py`, `backend/tests/conftest.py`, `backend/tests/test_config.py`, `backend/tests/test_database.py`, `backend/tests/test_sse_broker.py`
   - Do: Build `AppConfig` via pydantic-settings with env prefix `MEDIARIP`, nested delimiter `__`, YAML source (handle missing file gracefully), and `settings_customise_sources` for priority ordering. Build database module with aiosqlite: singleton connection pattern for lifespan, WAL + busy_timeout + synchronous PRAGMAs first, schema creation (sessions, jobs, config, unsupported_urls tables with indexes), async CRUD functions. Build SSEBroker with per-session queue map, subscribe/unsubscribe, and `publish` using `loop.call_soon_threadsafe`. Create `conftest.py` with shared fixtures (temp DB, test config). Write tests: config env override + YAML + zero-config defaults; DB CRUD + WAL verification + concurrent write test; broker subscribe/publish-from-thread/unsubscribe.

.gsd/milestones/M001/slices/S01/tasks/T02-SUMMARY.md

@@ -0,0 +1,104 @@
+---
+id: T02
+parent: S01
+milestone: M001
+provides:
+  - AppConfig with pydantic-settings (env + YAML + zero-config defaults)
+  - aiosqlite database layer with WAL mode, busy_timeout, CRUD functions
+  - SSEBroker with thread-safe publish via call_soon_threadsafe
+  - Shared test fixtures in conftest.py (tmp_db_path, test_config, db, broker)
+key_files:
+  - backend/app/core/config.py
+  - backend/app/core/database.py
+  - backend/app/core/sse_broker.py
+  - backend/tests/conftest.py
+key_decisions:
+  - Used monkeypatch.setitem on model_config to test YAML loading since pydantic-settings v2 does not accept _yaml_file as an init kwarg
+  - SSE broker fixture must be async (pytest_asyncio.fixture) using asyncio.get_running_loop() — get_event_loop() returns a different loop than the one running async tests
+  - env_prefix set to "MEDIARIP__" (with trailing delimiter) so nested vars use MEDIARIP__SERVER__PORT format
+patterns_established:
+  - _SafeYamlSource wraps YamlConfigSettingsSource to gracefully handle missing/None yaml_file
+  - Database PRAGMA order (busy_timeout → WAL → synchronous) set before any DDL
+  - _row_to_job helper converts aiosqlite.Row to Job model — single point of row mapping
+observability_surfaces:
+  - mediarip.database logger: INFO on journal_mode set and table creation
+  - mediarip.sse logger: WARNING on QueueFull (subscriber backpressure)
+  - mediarip.config logger: DEBUG when YAML file not found
+duration: 25m
+verification_result: passed
+completed_at: 2026-03-17
+blocker_discovered: false
+---
+
+# T02: Build config system, database layer, and SSE broker
+
+**Built pydantic-settings config (env + YAML + zero-config), aiosqlite database with WAL mode and CRUD, and thread-safe SSE broker — 47 tests passing**
+
+## What Happened
+
+Created three infrastructure modules in `backend/app/core/`:
+
+1. **config.py** — `AppConfig(BaseSettings)` with six nested config sections (ServerConfig, DownloadsConfig, SessionConfig, PurgeConfig, UIConfig, AdminConfig). Uses `_SafeYamlSource` subclass of `YamlConfigSettingsSource` that gracefully returns `{}` when the YAML file is missing or None. Priority chain: env vars → YAML → init kwargs → .env. Env prefix `MEDIARIP__` with `__` nesting.
+
+2. **database.py** — `init_db()` opens aiosqlite connection, sets PRAGMAs in the critical order (busy_timeout=5000 → journal_mode=WAL → synchronous=NORMAL), then creates four tables (sessions, jobs, config, unsupported_urls) with three indexes. CRUD functions: create_job, get_job, get_jobs_by_session, update_job_status, update_job_progress, delete_job, close_db. All writes commit immediately.
+
+3. **sse_broker.py** — `SSEBroker` holds a dict of session_id → list[asyncio.Queue]. `publish()` uses `loop.call_soon_threadsafe(_publish_sync, ...)` so yt-dlp worker threads can fire events safely. `_publish_sync` iterates queues with `put_nowait`, catching `QueueFull`.
+
+Created `conftest.py` with shared async fixtures (tmp_db_path, test_config, db, broker). The broker fixture is async to capture the running event loop correctly — `asyncio.get_event_loop()` returns a different loop than the test runner's.
+
+Two test issues discovered and fixed during verification:
+- YAML config tests initially used `_yaml_file` as an init kwarg, but pydantic-settings v2 rejects unknown init kwargs. Fixed by using `monkeypatch.setitem` on `model_config`.
+- Broker thread-safety tests initially failed because the broker fixture used `get_event_loop()` (deprecation-era API returning a stale loop). Fixed by making the fixture async with `get_running_loop()`.
+
+## Verification
+
+All three module test suites pass, plus the T01 model tests — 47/47 total:
+- `test_config.py`: 11 passed (zero-config, env overrides, YAML load, missing YAML, default templates)
+- `test_database.py`: 11 passed (all tables created, WAL mode, busy_timeout, indexes, CRUD roundtrip, concurrent writes)
+- `test_sse_broker.py`: 9 passed (subscribe, unsubscribe, publish, multi-subscriber, thread-safe publish, multi-thread publish)
+- `test_models.py`: 16 passed (unchanged from T01)
+
+## Verification Evidence
+
+| # | Command | Exit Code | Verdict | Duration |
+|---|---------|-----------|---------|----------|
+| 1 | `cd backend && python -m pytest tests/test_config.py -v` | 0 | ✅ pass | 0.22s |
+| 2 | `cd backend && python -m pytest tests/test_database.py -v` | 0 | ✅ pass | 0.19s |
+| 3 | `cd backend && python -m pytest tests/test_sse_broker.py -v` | 0 | ✅ pass | 0.23s |
+| 4 | `cd backend && python -m pytest tests/ -v` | 0 | ✅ pass | 0.42s |
+
+Slice-level checks (partial — T02 is not the final task):
+| # | Command | Exit Code | Verdict | Notes |
+|---|---------|-----------|---------|-------|
+| 1 | `test_models.py -v` | 0 | ✅ pass | T01 output |
+| 2 | `test_config.py -v` | 0 | ✅ pass | T02 new |
+| 3 | `test_database.py -v` | 0 | ✅ pass | T02 new |
+| 4 | `test_sse_broker.py -v` | 0 | ✅ pass | T02 new |
+| 5 | `test_download_service.py -v` | — | ⏳ pending | T03 |
+| 6 | `test_api.py -v` | — | ⏳ pending | T04 |
+
+## Diagnostics
+
+- WAL mode: `sqlite3 mediarip.db "PRAGMA journal_mode"` → should return `wal`
+- Config inspection: `python -c "from app.core.config import AppConfig; c = AppConfig(); print(c.model_dump())"`
+- Database tables: `sqlite3 mediarip.db ".tables"` → sessions, jobs, config, unsupported_urls
+- SSE broker: subscriber count visible via `len(broker._subscribers[session_id])`
+
+## Deviations
+
+- YAML config test approach changed from init kwarg (`_yaml_file=path`) to `monkeypatch.setitem(model_config, "yaml_file", path)` — pydantic-settings v2 forbids extra init kwargs.
+- Broker fixture changed from sync (`@pytest.fixture`) to async (`@pytest_asyncio.fixture`) using `get_running_loop()` instead of `get_event_loop()`.
+
+## Known Issues
+
+None.
+
+## Files Created/Modified
+
+- `backend/app/core/config.py` — AppConfig with nested sections, _SafeYamlSource, env/YAML/zero-config support
+- `backend/app/core/database.py` — init_db with WAL PRAGMAs, schema DDL, CRUD functions
+- `backend/app/core/sse_broker.py` — SSEBroker with thread-safe publish via call_soon_threadsafe
+- `backend/tests/conftest.py` — shared fixtures: tmp_db_path, test_config, db, broker
+- `backend/tests/test_config.py` — 11 config tests (zero-config, env override, YAML, missing YAML)
+- `backend/tests/test_database.py` — 11 database tests (tables, WAL, CRUD, concurrent writes)
+- `backend/tests/test_sse_broker.py` — 9 broker tests (subscribe, publish, thread-safe, multi-subscriber)

.gsd/milestones/M001/slices/S01/tasks/T02-VERIFY.json

@@ -0,0 +1,9 @@
+{
+  "schemaVersion": 1,
+  "taskId": "T02",
+  "unitId": "M001/S01/T02",
+  "timestamp": 1773805319038,
+  "passed": true,
+  "discoverySource": "none",
+  "checks": []
+}