"""
Database engine, session management, and WAL mode setup.

SQLite with WAL mode for single-user concurrent read/write safety.
"""

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

from sqlalchemy import event, create_engine, Engine
from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker

from app.config import settings


class Base(DeclarativeBase):
    """SQLAlchemy declarative base for all models."""
    pass


def _set_sqlite_wal_mode(dbapi_conn: Any, _connection_record: Any) -> None:
    """Enable WAL mode and other SQLite performance pragmas on every connection."""
    cursor = dbapi_conn.cursor()
    cursor.execute("PRAGMA journal_mode=WAL")
    cursor.execute("PRAGMA synchronous=NORMAL")
    cursor.execute("PRAGMA foreign_keys=ON")
    cursor.close()


def create_db_engine() -> Engine:
    """Create the SQLAlchemy engine with SQLite and WAL mode."""
    # Ensure the database directory exists
    settings.DATABASE_PATH.parent.mkdir(parents=True, exist_ok=True)

    engine = create_engine(
        f"sqlite:///{settings.DATABASE_PATH}",
        echo=settings.DEBUG,
        connect_args={"check_same_thread": False},
    )

    # Register WAL mode on every new connection
    event.listen(engine, "connect", _set_sqlite_wal_mode)

    return engine


engine = create_db_engine()
SessionLocal = sessionmaker(bind=engine, class_=Session, expire_on_commit=False)


def get_db() -> Session:
    """FastAPI dependency that yields a database session."""
    db = SessionLocal()
    try:
        yield db  # type: ignore[misc]
    finally:
        db.close()