from __future__ import annotations

import os
from collections.abc import AsyncIterator
from contextlib import asynccontextmanager

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

from app.api.routes import router
from app.config import Settings, get_settings
from app.db import init_db
from app.runtime import Runtime


def create_app(
    settings: Settings | None = None,
    runtime: Runtime | None = None,
) -> FastAPI:
    settings = settings or get_settings()
    runtime = runtime or Runtime(settings)

    @asynccontextmanager
    async def lifespan(app: FastAPI) -> AsyncIterator[None]:
        init_db()
        app.state.runtime = runtime
        yield
        await runtime.shutdown()

    app = FastAPI(title=settings.app_name, lifespan=lifespan)
    # Baked at build time (see Dockerfile); the frontend compares its own
    # version against this to self-heal from a stale cache.
    app.state.build_version = os.environ.get("BUILD_VERSION", "unknown")
    app.add_middleware(
        CORSMiddleware,
        allow_origins=settings.cors_origin_list,
        allow_credentials=True,
        allow_methods=["*"],
        allow_headers=["*"],
    )
    app.include_router(router)

    @app.get("/")
    def root() -> dict[str, str]:
        return {"name": settings.app_name, "docs": "/docs"}

    return app


app = create_app()