"""FastAPI application factory and lifecycle.

Startup runs migrations and opens the database engine; shutdown disposes it so no
connection or engine resource leaks. The engine, session factory, and config live
on ``app.state`` for dependencies to use. The app binds to 127.0.0.1 by default
and exposes the versioned ``/api/v1`` surface; US01-02 ships only health.
"""

from __future__ import annotations

from contextlib import asynccontextmanager

from fastapi import FastAPI

from photo_pipeline.api.routes import health, thumbnails
from photo_pipeline.config import Config
from photo_pipeline.db import create_db_engine, create_session_factory, run_migrations
from photo_pipeline.logging import configure_logging


def create_app(config: Config | None = None) -> FastAPI:
    config = config or Config.from_env()
    configure_logging(config.log_level, config.log_format)

    @asynccontextmanager
    async def lifespan(app: FastAPI):
        config.database_path.parent.mkdir(parents=True, exist_ok=True)
        run_migrations(config.database_url)
        engine = create_db_engine(config.database_url)
        app.state.config = config
        app.state.engine = engine
        app.state.session_factory = create_session_factory(engine)
        try:
            yield
        finally:
            engine.dispose()
            app.state.engine = None

    app = FastAPI(title="Photo Pipeline", version="0.1.0", lifespan=lifespan)
    app.include_router(health.router, prefix="/api/v1")
    app.include_router(thumbnails.router, prefix="/api/v1")
    return app