import asyncio
from contextlib import asynccontextmanager
from enum import Enum, auto
from pathlib import Path
from typing import AsyncGenerator, Optional

from loguru import logger
from sqlalchemy import text
from sqlalchemy.ext.asyncio import (
    create_async_engine,
    async_sessionmaker,
    AsyncSession,
    AsyncEngine,
    async_scoped_session,
)

from basic_memory.models import Base
from basic_memory.models.search import CREATE_SEARCH_INDEX

# Module level state
_engine: Optional[AsyncEngine] = None
_session_maker: Optional[async_sessionmaker[AsyncSession]] = None


class DatabaseType(Enum):
    """Types of supported databases."""

    MEMORY = auto()
    FILESYSTEM = auto()

    @classmethod
    def get_db_url(cls, db_path: Path, db_type: "DatabaseType") -> str:
        """Get SQLAlchemy URL for database path."""
        if db_type == cls.MEMORY:
            logger.info("Using in-memory SQLite database")
            return "sqlite+aiosqlite://"

        return f"sqlite+aiosqlite:///{db_path}"


def get_scoped_session_factory(
    session_maker: async_sessionmaker[AsyncSession],
) -> async_scoped_session:
    """Create a scoped session factory scoped to current task."""
    return async_scoped_session(session_maker, scopefunc=asyncio.current_task)


@asynccontextmanager
async def scoped_session(
    session_maker: async_sessionmaker[AsyncSession],
) -> AsyncGenerator[AsyncSession, None]:
    """
    Get a scoped session with proper lifecycle management.

    Args:
        session_maker: Session maker to create scoped sessions from
    """
    factory = get_scoped_session_factory(session_maker)
    session = factory()
    try:
        await session.execute(text("PRAGMA foreign_keys=ON"))
        yield session
        await session.commit()
    except Exception:
        await session.rollback()
        raise
    finally:
        await session.close()
        await factory.remove()


async def init_db() -> None:
    """Initialize database with required tables."""
    if _session_maker is None:  # pragma: no cover
        raise RuntimeError("Database session maker not initialized")

    logger.info("Initializing database...")

    async with scoped_session(_session_maker) as session:
        await session.execute(text("PRAGMA foreign_keys=ON"))
        conn = await session.connection()
        await conn.run_sync(Base.metadata.create_all)

        # recreate search index
        await session.execute(CREATE_SEARCH_INDEX)

        await session.commit()


async def get_or_create_db(
    db_path: Path,
    db_type: DatabaseType = DatabaseType.FILESYSTEM,
) -> tuple[AsyncEngine, async_sessionmaker[AsyncSession]]:  # pragma: no cover
    """Get or create database engine and session maker."""
    global _engine, _session_maker

    if _engine is None:
        db_url = DatabaseType.get_db_url(db_path, db_type)
        logger.debug(f"Creating engine for db_url: {db_url}")
        _engine = create_async_engine(db_url, connect_args={"check_same_thread": False})
        _session_maker = async_sessionmaker(_engine, expire_on_commit=False)

        # Initialize database
        await init_db()

    assert _engine is not None  # for type checker
    assert _session_maker is not None  # for type checker
    return _engine, _session_maker


async def shutdown_db() -> None:  # pragma: no cover
    """Clean up database connections."""
    global _engine, _session_maker

    if _engine:
        await _engine.dispose()
        _engine = None
        _session_maker = None


@asynccontextmanager
async def engine_session_factory(
    db_path: Path,
    db_type: DatabaseType = DatabaseType.MEMORY,
    init: bool = True,
) -> AsyncGenerator[tuple[AsyncEngine, async_sessionmaker[AsyncSession]], None]:
    """Create engine and session factory.

    Note: This is primarily used for testing where we want a fresh database
    for each test. For production use, use get_or_create_db() instead.
    """

    global _engine, _session_maker

    db_url = DatabaseType.get_db_url(db_path, db_type)
    logger.debug(f"Creating engine for db_url: {db_url}")

    _engine = create_async_engine(db_url, connect_args={"check_same_thread": False})
    try:
        _session_maker = async_sessionmaker(_engine, expire_on_commit=False)

        if init:
            await init_db()

        assert _engine is not None  # for type checker
        assert _session_maker is not None  # for type checker
        yield _engine, _session_maker
    finally:
        if _engine:
            await _engine.dispose()
            _engine = None
            _session_maker = None