"""Database test fixtures for Mantimon TCG.

This module provides fixtures for database integration testing using the
running dev containers (docker-compose).

Key insight: pytest-asyncio runs fixture teardown in a DIFFERENT event loop
than the test body. This causes "Future attached to different loop" errors
when trying to do async cleanup on connections created during the test.

Solution: Use SYNC psycopg2 for all fixture setup/teardown operations,
and only use asyncpg within the test body itself. The session is created
fresh per test with no cleanup needed (NullPool + TRUNCATE after).

Prerequisites:
    docker compose up -d  # Start Postgres (5433) and Redis (6380)
"""

import contextlib
import os
from collections.abc import AsyncGenerator
from typing import Any

import psycopg2
import pytest
import pytest_asyncio
from alembic import command
from alembic.config import Config
from sqlalchemy import pool
from sqlalchemy.ext.asyncio import (
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)

# =============================================================================
# Configuration
# =============================================================================

# Dev container URLs (matches docker-compose.yml)
TEST_DATABASE_URL = os.getenv(
    "TEST_DATABASE_URL",
    "postgresql+asyncpg://mantimon:mantimon@localhost:5433/mantimon",
)
SYNC_DATABASE_URL = os.getenv(
    "SYNC_DATABASE_URL",
    "postgresql+psycopg2://mantimon:mantimon@localhost:5433/mantimon",
)
TEST_REDIS_URL = os.getenv(
    "TEST_REDIS_URL",
    "redis://localhost:6380/1",  # Use DB 1 for tests, DB 0 for dev
)

# Connection params for sync psycopg2 (used in fixtures)
DB_PARAMS = {
    "host": "localhost",
    "port": 5433,
    "user": "mantimon",
    "password": "mantimon",
    "dbname": "mantimon",
}


# =============================================================================
# Tables to Truncate (ordered for FK constraints - children first)
# =============================================================================

TABLES_TO_TRUNCATE = [
    "game_history",
    "active_games",
    "campaign_progress",
    "collections",
    "decks",
    "oauth_linked_accounts",
    "users",
]


# =============================================================================
# Sync Helper Functions (for fixture setup/teardown)
# =============================================================================


def truncate_all_tables() -> None:
    """Truncate all tables using sync psycopg2.

    This runs in fixture teardown which may be in a different event loop,
    so we use sync operations to avoid event loop issues.
    """
    conn = psycopg2.connect(**DB_PARAMS)
    try:
        conn.autocommit = True
        with conn.cursor() as cur:
            for table in TABLES_TO_TRUNCATE:
                cur.execute(f"TRUNCATE TABLE {table} CASCADE")
    finally:
        conn.close()


# =============================================================================
# Migration Fixture (Session-Scoped, Sync)
# =============================================================================


@pytest.fixture(scope="session", autouse=True)
def _run_migrations() -> None:
    """Run Alembic migrations once per session.

    Uses sync psycopg2 to avoid async event loop issues.
    autouse=True ensures migrations run before any tests.
    """
    alembic_cfg = Config("alembic.ini")
    alembic_cfg.set_main_option("sqlalchemy.url", SYNC_DATABASE_URL)
    command.upgrade(alembic_cfg, "head")


# =============================================================================
# Database Session Fixture (Function-Scoped)
# =============================================================================


@pytest_asyncio.fixture
async def db_session() -> AsyncGenerator[AsyncSession, None]:
    """Provide a fresh async session for each test.

    The session uses NullPool (no connection reuse) and expires on commit=False.
    Tables are truncated AFTER each test using sync psycopg2 to avoid event
    loop issues in fixture teardown.

    Example:
        async def test_create_user(db_session):
            user = User(email="test@example.com", ...)
            db_session.add(user)
            await db_session.flush()

            assert user.id is not None
            # Data is truncated after test via sync cleanup
    """
    # Create fresh engine with NullPool
    engine = create_async_engine(
        TEST_DATABASE_URL,
        echo=False,
        poolclass=pool.NullPool,
    )

    # Create session factory
    session_factory = async_sessionmaker(
        bind=engine,
        class_=AsyncSession,
        expire_on_commit=False,
    )

    # Create session
    session = session_factory()

    try:
        yield session
    finally:
        # Close session without rollback (may fail on different event loop)
        # The truncate below will clean up any uncommitted data anyway
        with contextlib.suppress(RuntimeError):
            await session.close()

        # Dispose engine (may fail on different event loop)
        with contextlib.suppress(RuntimeError):
            await engine.dispose()

        # SYNC truncate - this always works regardless of event loop
        truncate_all_tables()


# =============================================================================
# Redis Client Fixture
# =============================================================================


@pytest_asyncio.fixture
async def redis_client() -> AsyncGenerator[Any, None]:
    """Provide a Redis client for testing.

    Uses DB 1 (test database) to avoid conflicts with dev data in DB 0.
    Flushes the database after each test.
    """
    import redis.asyncio as aioredis

    client = aioredis.from_url(TEST_REDIS_URL, decode_responses=True)
    try:
        yield client
    finally:
        try:
            await client.flushdb()
            await client.aclose()
        except RuntimeError:
            # Ignore event loop errors during cleanup
            pass


# =============================================================================
# Utility Fixtures
# =============================================================================


@pytest.fixture
def anyio_backend() -> str:
    """Specify asyncio as the async backend."""
    return "asyncio"