"""Shared pytest fixtures for the trading-bot test suite.

Provides:
- `db_session`: an `AsyncSession` against the dev Postgres (transaction-scoped,
  rolled back between tests).
"""

from __future__ import annotations

import os
from collections.abc import AsyncIterator

import pytest_asyncio
from sqlalchemy.ext.asyncio import (
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)


def _dev_db_url() -> str:
    return os.environ.get(
        "TRADING_TEST_DATABASE_URL",
        "postgresql+asyncpg://trading:trading@localhost:5432/trading_dev",
    )


@pytest_asyncio.fixture
async def db_session() -> AsyncIterator[AsyncSession]:
    """Per-test session wrapped in a transaction that is rolled back at teardown."""
    engine = create_async_engine(_dev_db_url(), echo=False)
    try:
        connection = await engine.connect()
        transaction = await connection.begin()
        session_factory = async_sessionmaker(
            bind=connection,
            class_=AsyncSession,
            expire_on_commit=False,
            join_transaction_mode="create_savepoint",
        )
        session = session_factory()
        try:
            yield session
        finally:
            await session.close()
            await transaction.rollback()
            await connection.close()
    finally:
        await engine.dispose()