"""App factory and lifespan."""

import logging
from contextlib import asynccontextmanager

from fastapi import FastAPI

from app.api import health
from app.config import Settings
from app.db.engine import close_db_connection, init_db
from app.logging_config import configure_logging


@asynccontextmanager
async def lifespan(app: FastAPI):
    """Application lifespan: startup and shutdown hooks.

    Handles database initialization, logging configuration,
    and cleanup on shutdown.
    """
    configure_logging()
    logging.info("SlabUploader starting up")
    await init_db()
    yield
    logging.info("SlabUploader shutting down")
    await close_db_connection()


def create_app(settings: Settings | None = None) -> FastAPI:
    """Create a fresh FastAPI app instance.

    Each call produces an independent app with its own database connection
    and cleared dependency overrides. This is the factory used by tests.

    Args:
        settings: Application settings. Uses env vars if None.

    Returns:
        Configured FastAPI application.
    """
    if settings is None:
        settings = Settings()
    settings.validate()

    app = FastAPI(title="SlabUploader", version="0.1.0", lifespan=lifespan)

    app.include_router(health.router)

    return app