"""Pin the leak-safety of the session-mode DB helpers.

chat_routes.py persists a session's "mode" in three best-effort spots (read
current mode, persist the effective mode, set research_pending). Those spots
previously hand-rolled `SessionLocal()` with `.close()` as the LAST statement
inside a try/except — so any error before close() (e.g. a SQLite "database is
locked" under concurrent streams) leaked the connection. With the default
QueuePool for file SQLite (5 + 10 overflow), accumulated leaks exhaust the
pool and the app can no longer obtain a DB session until restart.

The logic now lives in core.database.{get,set}_session_mode, which route
through get_db_session() (commit/rollback + guaranteed close). These tests pin
that a mid-operation DB error neither raises out of the helper nor leaks the
connection. The error-path cases fail against the old close()-inside-try
pattern.
"""
import os
os.environ.setdefault("DATABASE_URL", "sqlite:///:memory:")

from unittest.mock import MagicMock

from core import database as db


def _mock_session(monkeypatch):
    """Make get_db_session() hand out a MagicMock session (no real DB)."""
    sess = MagicMock()
    monkeypatch.setattr(db, "SessionLocal", lambda: sess)
    return sess


def test_set_session_mode_commits_and_closes_on_success(monkeypatch):
    sess = _mock_session(monkeypatch)
    assert db.set_session_mode("s1", "agent") is True
    sess.query.return_value.filter.return_value.update.assert_called_once_with({"mode": "agent"})
    sess.commit.assert_called_once()
    sess.close.assert_called_once()


def test_set_session_mode_does_not_leak_on_error(monkeypatch):
    sess = _mock_session(monkeypatch)
    sess.query.return_value.filter.return_value.update.side_effect = RuntimeError("database is locked")
    # Best-effort: the error is swallowed and False returned...
    assert db.set_session_mode("s1", "agent") is False
    # ...and crucially the connection is still returned to the pool.
    sess.rollback.assert_called_once()
    sess.close.assert_called_once()


def test_get_session_mode_reads_and_closes(monkeypatch):
    sess = _mock_session(monkeypatch)
    sess.query.return_value.filter.return_value.scalar.return_value = "research_pending"
    assert db.get_session_mode("s1") == "research_pending"
    sess.close.assert_called_once()


def test_get_session_mode_does_not_leak_on_error(monkeypatch):
    sess = _mock_session(monkeypatch)
    sess.query.return_value.filter.return_value.scalar.side_effect = RuntimeError("database is locked")
    assert db.get_session_mode("s1") is None
    sess.close.assert_called_once()