"""The accounts DB engine layer: dialect selection and the read/read-write split.

These run on the SQLite fallback (no THERMOGRAPH_DATABASE_URL in the test env);
the Postgres path (asyncpg RO/RW engines) is exercised by the docker-compose stack,
not the unit suite, so tests stay Postgres-free and fast."""
import asyncio

from sqlalchemy import select

from accounts import db


def test_defaults_to_sqlite_when_no_database_url():
    assert db.IS_POSTGRES is False
    # Both engines exist; on SQLite the RO engine is an alias of the RW one.
    assert db.async_engine is not None
    assert db.async_engine_ro is db.async_engine


def test_read_and_write_session_makers_are_distinct_dependencies():
    # Distinct FastAPI deps so pure-read endpoints can opt into the RO engine.
    assert db.get_async_session is not db.get_read_session
    assert callable(db.get_async_session) and callable(db.get_read_session)


def test_sync_url_derivation():
    assert db._sync_url("postgresql+asyncpg://u:p@h:5432/d") == "postgresql+psycopg://u:p@h:5432/d"
    assert db._sync_url("sqlite+aiosqlite:////tmp/x.sqlite") == "sqlite:////tmp/x.sqlite"


def test_read_session_yields_a_working_session():
    # On SQLite the read session is fully usable (no read-only enforcement); this
    # just confirms the dependency wiring resolves to a live AsyncSession.
    db.Base.metadata.create_all(db.sync_engine)

    async def _use():
        async for session in db.get_read_session():
            return (await session.execute(select(1))).scalar_one()

    assert asyncio.run(_use()) == 1