"""Database engine, session factory and declarative base."""

from __future__ import annotations

from collections.abc import Generator

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

from app.config import settings


class Base(DeclarativeBase):
    """Declarative base shared by every model."""


def _make_engine(url: str) -> Engine:
    connect_args = {"check_same_thread": False} if url.startswith("sqlite") else {}
    return create_engine(url, connect_args=connect_args, future=True)


engine = _make_engine(settings.database_url)
SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)


@event.listens_for(Engine, "connect")
def _enable_sqlite_foreign_keys(dbapi_connection, _connection_record) -> None:
    """SQLite ignores FK constraints unless they are explicitly switched on."""
    module = type(dbapi_connection).__module__
    if "sqlite" in module:
        cursor = dbapi_connection.cursor()
        cursor.execute("PRAGMA foreign_keys=ON")
        cursor.close()


def get_db() -> Generator[Session, None, None]:
    """FastAPI dependency yielding a scoped session."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def init_db() -> None:
    """Create all tables. Imported for side effects so every model is registered."""
    from app import models  # noqa: F401  (registers models on Base.metadata)

    Base.metadata.create_all(bind=engine)